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 NOV 1 1 1930 
 
 CORNE LL UNIV ERSITY 
 
 THE 
 
 IFlouier Ifetmttanj ^library 
 
 FOUNDED BY 
 
 ROSWELL P. FLOWER 
 for the use of the 
 
 N. Y. State Veterinary College 
 
 1897 
 
 This Volume is the Gift of 
 
 Mrs. P. A. Fish. 
 
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 3 1924 001 046 220 
 
 
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The original of this book is in 
 the Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://archive.org/details/cu31924001046220 
 
A TEXT-BOOK 
 
 HUMAN PHYSIOLOGY. 
 
 LANDOIS. 
 
NOTICES OF THE FIRST EDITION 
 
 OF 
 
 LANDOIS' PHYSIOLOGY. 
 
 " It speaks well for the popularity of Professor Landols' Text-book of Physiology that no fewer than four large 
 editions have been already published in Germany, although the hook made its first appearance not more than four or 
 five years ago. Indeed, it has evidently supplied a want in that country. In its German form it has also attained 
 considerable popularity in England. Inasmuch, however, as it is essentially a book for students as well as for practi- * 
 tioners of Medicine, no doubt the fact that it has not hitherto been translated has, to a considerable extent, interfered 
 with its wider circulation among that class of readers in this country. We must, therefore, tender to Professor 
 Stirling sincere thanks for undertaking the arduous task of rendering the work into English, thereby giving to English 
 students easy access to one, from their point of view, of the most practical books on physiology ever written. The 
 book, as the translator aptly remarks in his preface, forms a kind of bridge between physiology and practical 
 medicine, as one of its special features consists in the arrangement at the end of the various sections of the physi- 
 ology, proper, of an excellently clear and succinct account of the ways in which the normal functions treated of in 
 the preceding paragraphs may be modified under diseased conditions. * * * * Its special qualities are its com- 
 pleteness and conciseness. It contains a very large amount of accurate information put in such a way as to be 
 attractive and not tedious to the reader, and the information is brought up' to date Professor St ; rling's translation 
 possesses the great merit of reading as though it were not a translation; and the additional information which he has 
 inserted appears to us to be in all cases ample and judicious. The illustrations of the work are good, both those to 
 be found in the original and those which have been added." — British Medical Journal, January 31st, 188.5. 
 
 " It is the most complete and satisfactory text-book on Physiology extant. The translator and pub- 
 lisher have each done something to increase the value of the volume. Dr. Stirling has added numerous useful anno- 
 tations and a large number of new plates. * * * * We wish that every student and physician could be drilled in 
 these volumes." — The Medical Record, New York, Sept. sbth, 18S5. 
 
 "A careful examination of the work before us will, we think, convince any impartial reader that the claim put forth 
 by Dr. Stirling in favor of Prof. Landois is, at least so far as relates to the * eminent practicality' of his manual, a 
 well-founded one. Obviously, our author not only teaches his pupils how and to what extent pathological processes 
 are derangements of normal activities, but also most effectively aids the busy physician to trace back from morbid 
 phenomena the course of divergence from healthy physical operations, and to gather in this way new lights and novel 
 indications for the comprehension and scientific treatment of the maladies which he is called upon to cope with in his 
 daily warfare against disease. The superiority of the German work is attractively displayed in the abundant illustra- 
 tion allotted to this portion of the volume, renal anatomy being elucidated by no less than seven figures, including 
 four of Prof. Tyson's improved modifications of Klein's and of Henle's pictures. 
 
 "An additional feature of the great practical value is exhibited in the condensed account of the ' Comparative 
 Physiology of the Urinary Apparatus,' and in the brief historical resume devoted to an outline sketch of the chief 
 discoveries relating to the kidneys, from the days of Aristotle to the present time. Such a narrative of the progress of 
 our knowledge in regard to the renal functions not only serves to gratify a legitimate curiosity, which often forms 
 a powerful incentive to the prosecution of diligent study, but also contributes in an agreeable manner to fix indelibly 
 in the mind of a student the essential facts and many minor details of renal physiology and pathology. — American 
 Journal 0/ Medical Sciences, July, /886. 
 
 "Professor Landois* work on Physiology is particularly distinguished by its practical nature, and by the con- 
 stancy with which the author brings the facts of physiology into relationship with Medicine. It is a book written 
 especially for medical students and medical practitioners, and the success with which the author has adapted it to their 
 wants is shown by the fact that it has already passed through four large editions in four years. ***** The 
 work is thus calculated to direct the attention of the student toward a rational system of treatment, and to help the 
 practitioner rightly to understand and treat the cases under his care. * * * * Professor Stirling has translated 
 the work well. * * * * The work is, however, not a mere translation. Dr. Stirling has made large and valuable 
 additions to it. In places where the German edition begins abruptly, and seems to assume an amount of knowledge 
 which the student may not possess, Dr. Stirling has supplied the necessary introduction. * * * * Is one of the 
 best and most practical treatises on physiology we have ever seen."— Dr. T, Lauder Brunton, in "Brain/' 
 January, 1885. 
 
 Price of Second Edition, in Cloth, $6.50 ; in Leather, $7.50. 
 
A TEXT-BOOK OF 
 
 HUMAN PHYSIOLOGY, 
 
 INCLUDING 
 
 HISTOLOGY AND MICROSCOPICAL ANATOMY; 
 
 WITH 
 SPECIAL REFERENCE TO THE REQUIREMENTS OF 
 
 PRACTICAL MEDICINE. 
 
 DR. L. LANDOIS, 
 
 PROFESSOR OF PHYSIOLOGY AND DIRECTOR OF THE PHYSIOLOGICAL INSTITUTE, 
 UNIVERSITY OF GREIFSWALD. 
 
 SECOND AMERICAN, 
 TRANSLATED FROM THE FIFTH GERMAN EDITION. 
 
 WITH ADDITIONS BY 
 
 WILLIAM STIRLING, M.D., Sc.D., 
 
 BRACKENBDRY PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN OWEN'S COLLEGE AND VICTORIA UNIVERSITY, 
 MANCHESTER; EXAMINER IN THE HONOURS SCHOOL OF SCIENCE, UNIVERSITY OF OXFORD. 
 
 FIVE HUNDRED AND EIGHTY-THREE ILLUSTRATIONS. 
 
 PHILADELPHIA: 
 
 P. BLAKISTON, SON & CO., 
 
 No. 1012 Walnut Street. 
 1887. 
 
,887 
 
 Tier, /0<?6 i 
 
 
 W'i 
 
 H YW • ft -^ ■ ^-^ 
 
TO 
 
 SIR JOSEPH LISTER, Baronet, 
 
 M.D., D.C.L., LL.D., F.R.SS. (LOND. AND EDIN.), 
 
 PROFESSOR OF CLINICAL SURGERY IN KING'S COLLEGE, LONDON; SURGEON EXTRAORDINARY TO THE QUEEN; 
 FORMERLY REGIUS PROFESSOR OF CLINICAL SURGERY IN THE UNIVERSITY OF EDINBURGH. 
 
 IN ADMIRATION OF 
 
 WHOSE BRILLIANT DISCOVERIES HAVE REVOLUTIONIZED 
 
 MEDICAL PRACTICE, AND 
 
 CONTRIBUTED INCALCULABLY TO THE WELL-BEING OF MANKIND; 
 
 AND IN GRATITUDE TO 
 
 WHOSE NOBLE EARNESTNESS IN INCULCATING 
 
 THE SACREDNESS OF HUMAN LIFE 
 
 STIRRED THE HEARTS OF ALL WHO HEARD HIM: 
 
 BY HIS FORMER PUPIL, 
 
 THE TRANSLATOR. 
 
PREFATORY NOTE TO SECOND ENGLISH EDITION. 
 
 That a Second Edition of this " Text-Book of Physiology " has been called 
 for within little more than six months after the publication of the complete work, 
 indicates that the work has met a felt want. 
 
 In this Edition, the distinctive character of the work has been adhered to and 
 extended, matter being added bringing forward more clearly the relation of Physi- 
 ology to Practical Medicine and Surgery; the additions have chiefly been 
 derived from the Fifth German Edition, but there has been incorporated a large 
 amount of new matter. 
 
 The number of Woodcuts has been increased from 494 to 583, to most of the 
 Chapters I have added a paragraph on the Action of Drugs, and the Chapters 
 on the Nervous System have been largely recast, partly with the aid of the Lec- 
 tures on the Diseases of the Brain, by Dr. Gowers. 
 
 I would wish to tender my thanks to Dr. Lauder Brunton for the use of some 
 illustrations, and for information derived from his Text-Book of Pharmacology, 
 Therapeutics, and Materia Medica. For some suggestions relating to the Nervous 
 System I am indebted to my friend Professor Schafer, also to Dr. Sidney Martin, 
 who was kind enough to write the paragraph on " Vegetable Proteid Bodies," arid 
 to Dr. Berry Hart for suggestions on the Chapters on Reproduction. 
 
 Some of the new illustrations are taken from Schenk's Grundriss der normalen 
 Histologie. For some of the new illustrations I am indebted to Professors Victor 
 Horsley, Rutherford and Charteris, Drs. Hart and Johnson, and Mr. Martindale. 
 The others are acknowledged elsewhere. 
 
 Altogether, the work has been carefully revised, and I trust this Edition will 
 prove as useful to Practitioners and Students as the last one. 
 
 WILLIAM STIRLING. 
 The Owens College, 
 
 Manchester, June, 1886. 
 
PREFACE TO FIRST ENGLISH EDITION. 
 
 The fact that Professor Landois' "Lehrbuch der Physiologic des Menschen" 
 has already passed through four large editions since its first appearance in 1880, 
 shows that in some special way it has met the wants of Students and Practitioners 
 in Germany. The characteristic which has thus commended the work will be 
 found mainly to lie in its eminent practicality ; and it is this consideration which 
 has induced me to undertake the task of putting it into an English dress for 
 English readers. 
 
 Landois' work, in fact, forms a Bridge between Physiology and the Practice of 
 Medicine. It never loses sight of the fact that the Student of to-day is the prac- 
 ticing Physician of to-morrow. Thus, to every Section is appended — after a full 
 description of the normal processes — a short resume of the pathological variations, 
 the object of this being to direct the attention of the Student, from the outset, to 
 the field of his future practice, and to show him to what extent pathological pro- 
 cesses are a disturbance of the normal activities. 
 
 In the same way, the work offers to the busy physician in practice a ready means 
 of refreshing his memory on the theoretical aspects of Medicine. He can pass 
 backward from the examination of pathological phenomena to the normal pro- 
 cesses, and, in the study of these, find new indications and new lights for the 
 appreciation and treatment of the cases under consideration. 
 
 With this object in view, all the methods of investigation which may wich 
 advantage be used by the Practitioner, are carefully and fully described ; and 
 Histology, also, occupies a larger place than is usually assigned to it in Text- books 
 of Physiology. 
 
 A word as to my own share in the present version : — 
 
 (1.) In the task of translating, I have endeavored throughout to convey the 
 author's meaning accurately, without a too rigid adherence to the original. Those 
 who from experience know something of the difficulties of such an undertaking 
 will be most ready to pardon any shortcomings they may detect. 
 
 (2.) Very considerable additions have been made to the Histological and also 
 (where it has seemed necessary) to the Physiological sections. All such additions 
 are enclosed within square brackets [ ]. I have to acknowledge my indebtedness 
 to many valuable Papers in the various Medical Journals — British and Foreign — 
 and also to the Histological Treatises of Cadiat, Ranvier and Klein; Quain's 
 Anatomy, vol. 11, ninth edition; Hermann's Handbuch der Physiologie ; and the 
 Text-books on Physiology, by Rutherford, Foster and Kirkes ; Gamgee's Physio- 
 logical Chemistry ; Ewald's Digestion; and Robert's Digestive Ferments. 
 
 (3.) The Illustrations have been increased to 494 in the English version. These 
 
X PREFACE TO FIRST EDITION. 
 
 additional diagrams, with the sources whence derived, are distinguished in the 
 List of Woodcuts by an asterisk. 
 
 There only remains for me now to express my thanks to all who have kindly 
 helped in the progress of the work, either by furnishing Illustrations or otherwise 
 — especially to Drs. Byrom Bramwell, Dudgeon, Lauder Brunton, and Knott ; 
 Mr. Hawksley; Professors Hamilton and M'Kendrick; to my esteemed teacher 
 and friend, Professor Ludwig, of Leipzic ; and, finally, to my friend, Mr. A. W. 
 Robertson, M. A., formerly Assistant Librarian in the University, and now Libra- 
 rian of the. Aberdeen Public Library, for much valuable assistance while the work 
 was passing through the press. 
 
 The Second Part will, it is hoped, be issued early in 1885. 
 
 In conclusion — and forgetting for the moment my own connection with it — I 
 heartily commend the work per se to the attention of Medical Men, and can wish 
 for it no better fate than that it may speedily become as popular in this country as 
 it is in its Fatherland. 
 
 WILLIAM STIRLING. 
 Aberdeen University, 
 November, 1884. 
 
GENERAL CONTENTS. 
 
 INTRODUCTION. 
 
 PAGE 
 
 The Scope of Physiology, and its Relation to the other Branches of Natural Science . . . xxxi 
 
 Matter xxxii 
 
 Forces xxxiii 
 
 Law of the Conservation of Energy xxxvi 
 
 Animals and Plants xxxvii 
 
 Vital Energy and Life xxxix 
 
 I. PHYSIOLOGY OF THE BLOOD. 
 
 SECTION 
 
 1. Physical Properties of the Blood 17 
 
 2. Microscopic Examination of the Blood 18 
 
 3. Histology of the Human Red Blood Corpuscles 21 
 
 4. Effects of Reagents on the Blood Corpuscles 21 
 
 5. Preparation of the Stroma — Making Blood " Lake-Colored " 23 
 
 6. Form and Size of the Blood Corpuscles of Different Animals 24 
 
 7. Origin of the Red Blood Corpuscles 25 
 
 8. Decay of the Red Blood Corpuscles 28 
 
 9. The Colorless Corpuscles — Leucocytes — Blood Plates — Granules 29 
 
 10. A bnormal Changes of the Blood Corpuscles 34 
 
 11. Chemical Constituents of the Red Blood Corpuscles 35 
 
 12. Preparation of Haemoglobin Crystals 36 
 
 13. Quantitative Estimation of Haemoglobin 36 
 
 14. Use of Spectroscope 38 
 
 15. Compounds of Haemoglobin — Methaemoglobin 39 
 
 16. Carbonic Oxide-Haemoglobin — Poisoning with Carbonic Oxide . 40 
 
 17. Other Compounds— Haemoglobin 42 
 
 18. Decomposition of Haemoglobin 42 
 
 19. Haemin and Blood Tests 43 
 
 20. Haematoidin 44 
 
 21. The Colorless Proteid of Haemoglobin 44 
 
 22. Proteids of the Stroma 44. 
 
 23. The other Constituents of Red Blood Corpuscles 45. 
 
 24. Chemical Composition of the Colorless Corpuscles ... 45 
 
 25. Blood Plasma, and its Relation to Serum 46. 
 
 26. Preparation of Plasma 46 
 
 27. Fibrin — Coagulation of the Blood 47 
 
 28. General Phenomena of Coagulation 48 
 
 29. Cause of Coagulation of the Blood 49 
 
 30. Source of the Fibrin Factors 53 
 
 31. Relation of the Red Blood Corpuscles to the Formation of Fibrin 54 
 
 32. Chemical Composition of the Plasma and Serum 54 
 
 33. The Gases of the Blood 36 
 
 34. Extraction of the Blood Gases 57 
 
 35. Quantitative Estimation of the Blood Gases 59 
 
 36. The Blood Gases 59 
 
 37. Is Ozone (O a ) present in Blood? 60 
 
 38. Carbon dioxide and Nitrogen in Blood 61 
 
 39. Arterial and Venous Blood 62 
 
 40. Quantity of Blood 63 
 
 41. Variations from the Normal Condiiions of the Blood 63 
 
 II. PHYSIOLOGY OF THE CIRCULATION. 
 
 42. General View of the Circulation 67 
 
 43. The Heart '.'..'..'. 67 
 
 44. Arrangement of the Cardiac Muscular Fibres 68 
 
 45. Arrangement of the Ventricular Fibres 70 
 
 xi 
 
XH CONTENTS. 
 
 SECTION PAGE 
 
 46. Pericardium, Endocardium, Valves 71 
 
 47. Automatic Regulation of the Heart 73 
 
 48. The Movements of the Heart 75 
 
 49. Pathological Disturbances of Cardiac Action - 77 
 
 50. The Apex Beat — The Cardiogram 78 
 
 51. The Time occupied by the Cardiac Movements 83 
 
 52. Pathological Disturbance of the Cardiac Impulse '" 86 
 
 53. The Heart Sounds 88 
 
 54. Variations of the Heart Sounds 92 
 
 55. The Duration of the Movements of the Heart 92 
 
 56. Physical Examination of the Heart 92 
 
 57. Innervation of Heart — Cardiac Nerves 92 
 
 58. The Automatic Motor Centres of the Heart 95 
 
 59. The Cardio-Pneumatic Movements 104 
 
 60. Influence of the Respiratory Pressure of the Heart 105 
 
 THE CIRCULATION. 
 
 61. The Flow of Fluids through Tubes 108 
 
 62. Propelling Force, Velocity of Current, Lateral Pressure 108 
 
 63. Currents through Capillary Tubes 1 10 
 
 64. Movements of Fluids and Wave Motion in Elastic Tubes no 
 
 65. Structure and Properties of the Blood Vessels in 
 
 66. The Pulse — Historical 116 
 
 67. Instruments for Investigating the Pulse 117 
 
 68. The Pulse Curve or Sphygmogram 122 
 
 69. Dicrotic Pulse 126 
 
 70. Characters of the Pulse 127 
 
 71. Variations in the Strength, Tension and Volume of the Pulse . 128 
 
 72. The Pulse Curves of various Arteries 129 
 
 73. Anacrotism 130 
 
 74. Influence of the Respiratory Movements on the Pulse Curve 131 
 
 .75. Influence of Pressure upon the Form of the Pulse Curve 133 
 
 76. Rapidity of Transmission of Pulse Waves 134 
 
 77. Propagation of the Pulse Wave in Elastic Tubes 134 
 
 78. Velocity of the Pulse Wave in Man 136 
 
 79. Further Pulsatile Phenomena 137 
 
 80. Vibrations Communicated to the Body by the Action of the Heart 137 
 
 81. The Blood Current 139 
 
 82. Schemata of the Circulation 140 
 
 83. Capacity of the Ventricles 140 
 
 84. Estimation of the Blood Pressure 141 
 
 85. Blood Pressure in the Arteries 145 
 
 86. Blood Pressure in the Capillaries 151 
 
 87. Blood Pressure in the Veins 152 
 
 88. Blood Pressure in the Pulmonary Artery .- 153 
 
 89. Measurement of the Velocity of the Blood Stream 155 
 
 90. Velocity of the Blood in Arteries, Capillaries, and Veins 157 
 
 91. Estimation o£ the Capacity of the Ventricles 159 
 
 92. The Duration of the Circulation 159 
 
 93. Work of the Heart 159 
 
 94. Blood Current in the Smaller Vessels , J60 
 
 95. Passage of the Blood Corpuscles out of the Vessels — [Diapedesis] 162 
 
 96. Movement of the Blood in the Veins 163 
 
 97. Rounds or Bruits within Arteries 164 
 
 98. Venous Murmurs 164 
 
 99. The Venous Pulse — Phlebogram 165 
 
 100. Distribution of the Blood 167 
 
 101. Plethysmography 167 
 
 102. Transfusion of Blood 168 
 
 THE BLOOD GLANDS. 
 
 103. The Spleen — Thymus — Thyroid — Suprarenal Capsules— Hypophysis Cerebri— Coc- 
 
 cygeal and Carotid Glands 172 
 
 104. Comparative 181 
 
 105. Historical Retrospect , . 182 
 
CONTENTS. Xlll 
 III. PHYSIOLOGY OF RESPIRATION. 
 
 SECTION PAGE 
 
 106. Structure of the Air Passages and Lungs 183 
 
 107. Mechanism of Respiration 190 
 
 108. Quantity of Gases Respired '. 191 
 
 109. Number of Respirations • 192 
 
 1 10. Time occupied by the Respiratory Movements 192 
 
 11 1 . Pathological Variations of the Respiratory Movements 19S 
 
 112. General View of the Respiratory Muscles 1 96 
 
 1 13. Action of the Individual Respiratory Muscles 197 
 
 1 14. Relative Sire of the Chest 201 
 
 115. Pathological Variations of the Percussion Sounds ... 203 
 
 116. The'Normal Respiratory Sounds 204 
 
 117. Pathological Respiratory Sounds 204 
 
 1 18. Pressure in the Air Passages during Respiration 205 
 
 119. Appendix to Respiration 207 
 
 120. Peculiarly Modified Respiratory Sounds 207 
 
 CHEMISTRY OF RESPIRATION. 
 
 121. Quantitative Estimation of C0 2 , O, and Watery Vapor 209 
 
 122. Methods of Investigation 209 
 
 123. Composition and Properties of Atmospheric Air 212 
 
 124. Composition of Expired Air 212 
 
 125. Daily Quantity of Gases Exchanged 213 
 
 126. Review of the Daily Gaseous Income and Expenditure 213 
 
 127. Conditions Influencing the Gaseous Exchanges . . 213 
 
 128. Diffusion of Gases within the Lungs 216 
 
 129. Exchange of Gases between the Blood and Air 216 
 
 130. Dissociation of Gases . 218 
 
 131. Cutaneous Respiration 219 
 
 132. Internal Respiration 219 
 
 133. Respiration in a Closed Space 221 
 
 134. Dyspnoea and Asphyxia 222 
 
 135. Respiration of Foreign Gases . . . . 225 
 
 136. Accidental Impurities of the Air .... 225 
 
 137. Ventilation of Rooms 226 
 
 138. Formation of Mucus . . 227 
 
 139. Action of the Atmospheric Pressure . . ... 229 
 
 140. Comparative and Historical 230 
 
 IV. PHYSIOLOGY OF DIGESTION. 
 
 141. The Mouth and its Glands .... . . 232 
 
 142. The Salivary Glands 233 
 
 i+j. Histoligical Changes in the Salivary Glands . ... ... 235 
 
 144. The Nerves of the Salivary Glands 237 
 
 145. Action of Nerves on the Salivary Secretion .... 237 
 
 146. The Saliva of the Individual Glands 242 
 
 147. The Mixed Saliva in the Mouth . ... 243 
 
 148. Physiological Action of Saliva .... ... . . 244 
 
 149. Tests for Sugar . . . 246 
 
 150. Quantitative Estimation of Sugar . . ... . 247 
 
 151. Mechanism of the Digestive Apparatus 248 
 
 152. Introduction of the Food .... 248 
 
 153. The Movements of Mastication 248 
 
 154. Structure and Development of the Teeth 249 
 
 155. Movements of the Tongue 253 
 
 156. Deglutition 254 
 
 157. Movements of the Stomach 256 
 
 158. Vomiting 257 
 
 159. Movements of the Intestine 259 
 
 160. Excretion of Faecal Matter .... 260 
 
 161. Influence of Nerves on the Intestine 262 
 
 162. Structure of the Stomach 266 
 
 163. The Gastric Juice '_ 269 
 
 164. Secretion of Gastric Juice 269 
 
XIV r . CONTENTS. 
 
 SECTION PACE 
 
 165. Methods of obtaining Gastric Juice 273 
 
 166. Process of Gastric Digestion 274 
 
 167. Gases in the Stomach 278 
 
 168. Structure of the Pancreas 278 
 
 169. The Pancreatic Juice 279 
 
 170. Digestive Action of the Pancreatic Juice ,, 280 
 
 171. The Secretion of the Pancreatic Juice 283 
 
 172. Preparation of Peptonized Food 284 
 
 173. Structure of the Liver 284 
 
 174. Chemical Composition of the Liver Cells 288 
 
 175. Diabetes Mellitus, or Glycosuria 290 
 
 176. The Functions of the Liver ' 292 
 
 177. Constituents of the Bile f 293 
 
 178. Secretion of Bile , 296 
 
 179. Excretion of Bile • 298 
 
 180. Reabsorption of Bile ... 299 
 
 181. Functions of the Bile 301 
 
 182. Fate of the Bile in the Intestine _ 302 
 
 183. The Intestinal Juice - 303 
 
 184. Fermentation Processes in the Intestine 307 
 
 185. Processes in the Large Intestine .... 31 1 
 
 186. Pathological Variations 314 
 
 187. Comparative Physiology 316 
 
 188. Historical Retrospect 317 
 
 V. PHYSIOLOGY OF ABSORPTION. 
 
 189. The Organs of Absorption 319 
 
 190. Structure of the Small and Large Intestines 319 
 
 191. Absorption of the Digested Food 325 
 
 192. Absorptive Activity of the Wall of the Intestine ' 327 
 
 193. Influence of the Nervous System 331 
 
 194. Feeding with " Nutrient Enemata " 331 
 
 195. Chyle Vessels and Lymphatics 332 
 
 196. Origin of the Lymphatics 332 
 
 197. The Lymph Glands 335 ■ 
 
 198. Properties of Chyle and Lymph 337 
 
 199. Quantity of Lymph and Chyle 339 
 
 200. Origin of Lymph 340 
 
 201. Movement of Chyle and Lymph 341 
 
 202. Absorption of Parenchymatous Effusions 344 
 
 203. Congestion of Lymph, Serous Effusions and (Edema . 344 
 
 204. Comparative Physiology 346 
 
 205. Historical Retrospect 346 
 
 VI. PHYSIOLOGY OF ANIMAL HEAT. 
 
 206. Sources of Heat 347 . 
 
 207. Homoiothermal and Poikilothermal Animals 350 
 
 208. Methods of Estimating Temperature — Thermometry 351 
 
 209. Temperature — Topography 353 
 
 210. Conditions Influencing the Temperature of Organs 354 
 
 211. Estimation of the Amount of Heat — Calorimetry 356 
 
 212. Thermal Conductivity of Animal Tissues 357 
 
 213. Variations of the Mean Temperature 3^8 
 
 214. Regulation of the Temperature 361 
 
 215. Income and Expenditure of Heat 363 
 
 216. Variations in Heat Production 365 
 
 217. Relation of Heat Production to Bodily Work . . , 365 
 
 218. Accommodation for different Temperatures 366 
 
 219. Storage of Heat in the Body 367 
 
 220. Fever 367 
 
 221. Artificial Increase of the Temperature 369 
 
 222. Employment of Heat 369 
 
 223. Increase of Temperature post-mortem 369 
 
 224. Action of Cold on the Body 370 
 
CONTENTS. XV 
 
 SBCTION PAGE 
 
 225. Artificial Lowering of Temperature 37° 
 
 226. Employment of Cold ■ . . 37 1 
 
 227. Heat of Inflamed Parts 372 
 
 228. Historical and Comparative 37 z 
 
 VII.THYSIOLOGY OF THE METABOLIC PHENOMENA OF THE BODY. 
 
 229. General View of Food Stuffs 373 
 
 230. Structure and Secretion of the Mammary Glands 375 
 
 231. Milk and its Preparations 377 
 
 232. Eggs 381 
 
 233. Flesh and its Preparations 3^' 
 
 234. Vegetable Foods 383 
 
 235. Condiments — Coffee, Tea, and Alcohol 385 
 
 PHENOMENA AND LAWS OF METABOLISM. 
 
 236. Equilibrium of the Metabolism 388 
 
 237. Metabolism during Hunger and Starvation .... 394 
 
 238. Metabolism during a purely Flesh Diet . 396 
 
 239. A Diet of Fat or of Carbohydrates . . 397 
 
 240. Mixture of Flesh and Fat 397 
 
 241. Origin of Fat in the Body .... 398 
 
 242. Corpulence 399 
 
 243. The Metabolism of the Tissues 400 
 
 244. Regeneration of Organs and Tissues 402 
 
 245. Transplantation of the Tissues 405 
 
 246. Increase in Size and Weight during Growth 405 
 
 GENERAL VIEW OF THE CHEMICAL CONSTITUENTS OF THE ORGANISM. 
 
 247. Inorganic Constituents 407 
 
 248. Organic Compounds — Proteids : 408 
 
 249. The Animal and Vegetable Proteids and their Properties 409 
 
 250. The Albuminoids 411 
 
 251. The Fats . 412 
 
 252. The Carbohydrates . . . ... 415 
 
 253. Historical Retrospect ... . .... .... 417 
 
 VIII. THE SECRETION OF URINE. 
 
 254. Structure of the Kidney . . . ... ... 419 
 
 255. The Urine . . . . . 426 
 
 256. Urea 430 
 
 257. Qualitative and Quantitative Estimation of Urea 432 
 
 258. Uric Acid . 434 
 
 259. Qualitative and Quantitative Estimation of Uric Acid . . : . . . 435 
 
 260. Kreatinin and other Substances 436 
 
 261. Coloring Matters of the Urine ... .... 439 
 
 262. Indigo, Phenol, Kresol, Pyrokatechin 440 
 
 263. Spontaneous Changes in Urine, Fermentations . . . ... 443 
 
 264. Albumin in Urine 445 
 
 265. Blood in Urine ..... ... .... . . 447 
 
 266. Bile in Urine . . . 450 
 
 267. Sugar in Urine .... '. . 451 
 
 268. Cystin . . . .... 454 
 
 269. Leucin, Tyrosin . . . . ... . . . .... 454 
 
 270. Deposits in Urine 455 
 
 271. General Scheme for Detecting Urinary Deposits 457 
 
 272. Urinary Calculi . ... 458 
 
 273. The Secretion of Urine . . . 459 
 
 274. The Preparation of Urine . . 463 
 
 275. Passage of Various Substances into the Urine 465 
 
 276. Influence of Nerves on the Renal Secretion . . 465 
 
 277. Ursemia, Ammoniaemia . . . ... 469 
 
XVI CONTENTS. 
 
 SECTION PAGE 
 
 278. Structure and Functions of the Ureter 47° 
 
 279. Urinary Bladder and Urethra .... . . ... . 47 1 
 
 280. Accumulation and Retention of Urine . . . . ......... 47 2 
 
 281. Retention and Incontinence of Urine .... . . • . 475 
 
 282. Comparative and Historical 475 
 
 IX. FUNCTIONS OF THE SKIN. 
 
 283. Structure of the Skin . . 
 
 284. Nails and Hair 
 
 285. The Glands of the Skin 
 
 286. The Skin as a Protective Covering .... 
 
 287. Cutaneous Respiration and Secretion — Sweat 
 
 288. Conditions Influencing the Secretion of Sweat 
 
 289. Pathological Variations 
 
 290. Cutaneous Absorption — Galvanic Conduction 
 
 291. Comparative — Historical . 
 
 X. PHYSIOLOGY OF THE MOTOR APPARATUS. 
 
 4' 
 
 4/9 
 
 482 
 
 483 
 484 
 486 
 •188 
 489 
 490 
 
 292. Ciliary Motion, Pigment Cells 49 1 
 
 292A.Structure and Arrangement of the Muscles 493 
 
 293. Physical and Chemical Properties of Muscle 5 oc 
 
 294. Metabolism in Muscle ... 5°' 
 
 295. Rigor mortis ... S '' 
 
 296. Muscular Excitability ... 5°^ 
 
 297. Changes in a Muscle during Contraction 5 11 
 
 298. Muscular Contraction ! 5 '3 
 
 299. Rapidity of Transmission of a Muscular Contraction ... 523 
 
 300. Muscular Work ... 5 2 4 
 
 301. The Elasticity of Muscle . 526 
 
 302. Formation of Heat in an Active Muscle . 5 2 9 
 
 303. The Muscle Sound 530 
 
 304. Fatigue of Muscle .... .... 53 1 
 
 305. The Mechanism of the Joints 533 
 
 306. Arrangement and Uses of the Muscles of the Body 535 
 
 307. Gymnastics — Pathological Motor Variations 538 
 
 308. Standing . .... 539 
 
 309. Sitting . 54° 
 
 310. Walking and Running 54' 
 
 311. Comparative . . 543 
 
 VOICE AND SPEECH. 
 
 312. Voice and Speech . . 545 
 
 313. Arrangement of the Larynx ... 545 
 
 314. Organs of Voice — Laryngoscopy .... 551 
 
 315. Conditions Modifying the Laryngeal Sounds . 553 
 
 316. Range of the Voice . 554 
 
 317. Speech — The Vowels . . . . 555 
 
 318. The Consonants 557 
 
 319. Pathological Variations of Voice and Speech . 558 
 
 320. Comparative — Historical . . . . 559 
 
 XI. GENERAL PHYSIOLOGY OF THE NERVES AND ELECTRO- 
 PHYSIOLOGY. 
 
 321. Structure and Arrangement of the Nerve Elements 561 
 
 322 Chemistry of the Nerve Substance 566 
 
 323. Metabolism of Nerves . 568 
 
 324. Excitability of Nerves — Stimuli 568 
 
 325. Diminution of the Excitability — Degene:ation and Regeneration of Nerves . . . 572 
 
 326. The Galvanic Current . 577 
 
 327. Action of the Galvanic Current — Galvanometer 578 
 
 328. Electrolysis ... 579 
 
 329. Induction — Extra Current — Magneto-Induction . ... . . 584 
 
CONTENTS. XV11 
 
 SICTIOS PACK 
 
 330. Du Bois-Reymond's Inductofium S°° 
 
 331. Electrical Currents in Passive Muscle and Nerve 588 
 
 332. Currents of Stimulated Muscle and Nerve . . 59 1 
 
 333. Currents in Nerve and Muscle during Electrotonus 594 
 
 334. Theories of Muscle and Nerve Currents 595 
 
 335. Electrotonic Alteration of the Excitability . . 597 
 
 336. Electrotonus — Law of Contraction 600 
 
 337. Rapidity of Transmission of Nervous Impulses 602 
 
 338. Double Conduction in Nerves ... . 605 
 
 339. Therapeutical Uses of Electricity — Reaction of Degeneration 606 
 
 340. Electrical Charging of the Body 611 
 
 341. Comparative — Historical . . . .611 
 
 XII. PHYSIOLOGY OF THE PERIPHERAL NERVES. 
 
 342. Classification of Nerve Fibres 613 
 
 343. Nervus Olfactorius 615 
 
 •344. Nervus Opticus .... 616 
 
 345. Nervus Oculomotorius . 618 
 
 346. Nervus Trochlearis 621 
 
 347. Nervus Trigeminus 621 
 
 348. Nervus Abducens 630 
 
 349. Nervus Facialis 631 
 
 350. Nervus Acusticus 634 
 
 351. Nervus Glosso-pharyngeus . 637 
 
 352. Nervus Vagus ... 638 
 
 353. Nervus Accessorius 644 
 
 354. Nervus Hypoglossus 645 
 
 355. The Spinal Nerves . 645 
 
 356. The Sympathetic Nerve 649 
 
 357. Comparative — Historical .... 652 
 
 XIII. PHYSIOLOGY OF THE NERVE CENTRES. 
 
 358. General ... 653 
 
 359. Structure of the Spinal Cord . . 654 
 
 360. Spinal Reflexes 661 
 
 361. Inhibition of the Reflexes 664 
 
 362. Centres in the Spinal Cord 668 
 
 363. Excitability of the Spinal Cord 670 
 
 364. The Conducting Paths in the Spinal Cord 671 
 
 365. General Schema of the Brain 675 
 
 366. The Medulla Oblongata 681 
 
 367. Reflex Centres of the Medulla Oblongata 685 
 
 368. The Respiratory Centre 686 
 
 369. The Cardio-Inhibitory Centre . . . . 691 
 
 370. The Accelerans Cordis Centre 693 
 
 371. Vasomotor Centre and Vasomotor Nerves 695 
 
 372. Vaso-dilator Centre and Vaso-dilator Nerves 701 
 
 373. The Spasm Centre — The Sweat Centre 702 
 
 374. Psychical Functions of the Cerebrum 703 
 
 375. Structure of the Cerebrum — Motor Cortical Centres 709 
 
 376. The Sensory Cortical Centres 721 
 
 377. The Thermal Cortical Centres 724 
 
 378. Topography of the Cortex Cerebri ... 725 
 
 379. The Basal Ganglia— The Mid-brain 733 
 
 380. The Structure and Functions of the Cerebellum 739 
 
 381. The Protective Apparatus of the Brain 742 
 
 382. Comparative — Historical 746 
 
 XIV. PHYSIOLOGY OF THE SENSE ORGANS. 
 
 1. SIGHT. 
 
 383. Introductory Observations 74^ 
 
 384. Histology of the Eye 750 
 
 385. Dioptric Observations 759 
 
 B 
 
XV111 CONTENTS. 
 
 SECTION PAGE 
 
 386. Formation of a Retinal Image ' 764 
 
 387. Accommodation of the Eye [ 766 
 
 388. Normal and Abnormal Refraction ' ' 770 
 
 389. The Power of Accommodation 772 
 
 390. Spectacles 773 
 
 391. Chromatic Aberration and Astigmatism 774 
 
 392. The Ws 775 
 
 393. Entoptical Phenomena 779 
 
 394. Illumination of the Eye — The Ophthalmoscope 781 
 
 395. Activity of the Retina in Vision 785 
 
 396. Perception of Colors 790 
 
 397. Color Blindness 794 
 
 398. Stimulation of the Retina 796 
 
 399. Movements of the Eyeballs 799 
 
 400. Binocular Vision 803 
 
 401. Single Vision — Identical Points 803 
 
 402. Stereoscopic Vision 805 
 
 403. Estimation of Size and Distance 808 
 
 404. Protective Organs of the Eye 810 
 
 405. Comparative — Historical . 812 
 
 2. HEARING. 
 
 406. Structure of the Organ of Hearing 814 
 
 407. Physical Introduction . . 815 
 
 408. Ear Muscles 816 
 
 409. Tympanic Membrane 816 
 
 410. The Auditory Ossicles and their Muscles 819 
 
 411. Eustachian Tube — Tympanum 822 
 
 412. Conduction of Sound in the Labyrinth 824 
 
 413. Structure of the Labyrinth 825 
 
 414. Auditory Perceptions of Pitch 828 
 
 415. Perception of Quality — Vowels . . . 830 
 
 416. Action of the Labyrinth 833 
 
 417. Harmony — Discords — Beats 835 
 
 418. Perception of Sound 836 
 
 419. Comparative — Historical 837 
 
 3. SMELL. 
 
 420. Structure of the Organ of Smell 839 
 
 421. Olfactory Sensations 840 
 
 4. TASTE. 
 
 422. Position and Structure of the Organs of Taste 841 
 
 423. Gustatory Sensations 842 
 
 5. TOUCH. 
 
 424. Terminations of Sensory Nerves 844 
 
 425. Sensory and Tactile Sensations .... 846 
 
 426. The Sense of Locality 847 
 
 427. The Pressure Sense 850 
 
 428. The Temperature Sense 852 
 
 429. Common Sensation — Pain 853 
 
 430. The Muscular Sense ... 854 
 
 XV. PHYSIOLOGY OF REPRODUCTION AND DEVELOPMENT. 
 
 431. Forms of Reproduction .... 857 
 
 432. Testis — Seminal Fluid . . 857 
 
 433. The Ovary — Ovum — Uterus 862 
 
 434. Puberty 866 
 
 435. Menstruation 867 
 
 436. Penis — Erection . . 869 
 
CONTENTS. XIX 
 
 SECTION PAGE 
 
 437. Ejaculation — Reception of the Semen 872 
 
 438. Fertilization of the Ovum 872 
 
 439. Impregnation and Cleavage of the Ovum 873 
 
 440. Structures formed from the Epiblast 877 
 
 441. Structures formed from the Mesoblast and Hypoblast 877 
 
 442. Formation of the Heart and Embryo 878 
 
 443. Further Formation of the Body 880 
 
 444. Formation of the Amnion and Allantois 881 
 
 445. Human Foetal Membranes — Placenta 882 
 
 446. Chronology of Human Development 886 
 
 447. Formation of the Osseous System 888 
 
 448. Development of the Vascular System 892 
 
 449. Formation of the Intestinal Canal 895 
 
 450. Development of the Genito-urinary Organs 897 
 
 451. Formation of the Central Nervous System 900 
 
 452. Development of the Sense Organs 901 
 
 453. Birth 902 
 
 454. Comparative — Historical 903 
 
LIST OF ILLUSTRATIONS. 
 
 FIGURE PAGE 
 
 i. Human colored blood corpuscles 19 
 
 2. Apparatus of Abbe and Zeiss for estimating the blood corpuscles 20 
 
 3. Mixer 20 
 
 *4. Gower's haemacytometer (Hawksley) 20 
 
 5. Red blood corpuscles showing various changes of shape 21 
 
 6. Vaso-formative cells 26 
 
 7. White blood corpuscles 29 
 
 *8. White blood corpuscles {Klein} 30 
 
 9. Amoeboid movements 32 
 
 10. Blood plates and their derivatives 33 
 
 1 1 . Haemoglobin crystals 35 
 
 *i 2. Gower's haemoglobinometer [Hawksley) 37 
 
 13. Scheme of a spectroscope 38 
 
 14. Various spectra of haemoglobin . . , 39 
 
 15. Haeniin crystals 43 
 
 16. Haemin crystals prepared from traces of blood 43 
 
 17. Hsernatoidin-crystals 44 
 
 *i8. Hewson's experiment 50 
 
 19. Scheme of Pfluger's gas pump 58 
 
 20. Micrococcus, bacterium, vibrio , . 66 
 
 *2I. Bacillus anthracis 66 
 
 *22. Scheme of the circulation 67 
 
 23. Muscular fibres from the heart 68 
 
 24. Muscular fibres in the left auricle 69 
 
 25. Muscular fibres in the ventricles 70 
 
 *26. Lymphatic from the pericardium ( Cadiat) 71 
 
 *27. Section of the endocardium (Cadiat) 71 
 
 *28. Purkinje's fibres (Ranvier) 72 
 
 29. Cast of the ventricles of the human heart 76 
 
 30. The closed semilunar valves 77 
 
 *3I. Various cardiographs (Hermann) 79 
 
 32. Curves of the apex beat 79 
 
 33. Changes of the heart during systole, and sections of thorax 80 
 
 *34. Dog's heart, posterior surface (Ludwig and Hesse) 82 
 
 *35. Left lateral surface (Ludwig and Hesse) 82 
 
 *3§. Anterior surface (Ludwig and Hesse) 83 
 
 *37. Base of heart (Ludwig and Hesse) 83 
 
 *38. Base of heart in systole and diastole (Ludwig and Hesse) 83 
 
 39. Curves from a rabbit's ventricle 84 
 
 *40. Marey's registering tambour (Hermann) 85 
 
 41. Curves obtained with a cardiac sound 86 
 
 42. Curves from the cardiac impulse 87 
 
 *43. Scheme of cardiac cycle 89 , 
 
 *44. Position of the heart in the chest (Luschka and Gairdner) 90 
 
 *45. Heart of frog from the front (Ecker) 94 
 
 *4§. Heart of frog from behind (Ecker) . 94 
 
 *47. Auricular septum (Ecker) 95 
 
 48. Bipolar nerve cells from a frog's heart 95 
 
 49. Frog's heart (Ecker) 95 
 
 ♦49a. Scheme of frog's heart (Brunton) 95 
 
 *SO. Stannius's experiment (Brunton) 97 
 
 *5 1 . Scheme of a frog manometer (Stirling) 98 
 
 *S2. Perfusion cannula (JCronecker and Stirling) 98 
 
 *53. Roy's tonometer (Stirling) 99 
 
 *54. Luciani's groups of cardiac pulsations (Hermann) 100 
 
 *55. Curves of a frog's heart at different temperatures (Hermann) 101 
 
 xxi 
 
XXU ILLUSTRATIONS. 
 
 FIGURE PAGE 
 
 56. Cardio-pneumograph of Landois 104 
 
 57. Apparatus for showing the effect of respiration 106 
 
 ,58. Cylindrical vessel filled with water 108 
 
 59. Cylindrical vessel with manometers 109 
 
 60. Small artery with its various coats in 
 
 61. Capillaries injected with silver nitrate 112 
 
 *62. Longitudinal section of a vein at a valve (Cadiat) 114 
 
 63. Poiseuille's pulse measurer 117 
 
 64. Sphygmometer of Herisson 117 
 
 65. Scheme of Marey's sphygmograph 118 
 
 *66. Marey's improved Sphygmograph (B. Bramwell) 118 
 
 *67. Scheme of Marey's sphygmograph in working order (B. Bramwell) 118 
 
 *68. Scheme of Marey's sphygmograph (B. Bramwell) 118 
 
 *69- Dudgeon's sphygmograph (Dudgeon) 119 
 
 *70. Mode of applying Dudgeon's sphygmograph (Dudgeon) 119 
 
 *7I. Sphygmogram (Dudgeon) 120 
 
 72. Scheme of Brondgeest's pansphygmograph ... 120 
 
 73. Scheme of Landois' angiograph 121 
 
 74. Pulse curves of the carotid, radial, and posterior tibial arteries 121 
 
 75. Landois's gas sphygmoscope 122 
 
 76. Hsemautographic curve 122 
 
 •77. Sphygmogram of radial artery (Dudgeon) 123 
 
 . 78. Sphygmograms of various arteries 123 
 
 79. Pulsus dicrotus, P. caprizans, P. monoerotus 124 
 
 *8o. Aortic regurgitation 126 
 
 *8l. Pulsus dicrotus 126 
 
 *82. Hyperdicrotic pulse 127 
 
 83. Pulsus alternans ' . . . . 128 
 
 84. Curves of the posterior tibial .and pedal arteries 130 
 
 85. Anacrotic pulse curves 130 
 
 86. Anacrotic pulse curves 131 
 
 87. Influence of the respiration on the sphygmogram , 131 
 
 88. Pulse curves during Miiller's and Valsalva's experiments 132 
 
 89. Pulsus paradoxus 133 
 
 90. Various radial curves altered by pressure 1 34 
 
 91. Apparatus for measuring the velocity of the pulse wave . . 135 
 
 92. Tracing obtained from 91 135 
 
 93. Pulse tracings of the radial artery 136 
 
 94. Tracings from the posterior tibial and carotid arteries 136 
 
 95. Apparatus for registering the molar motions of the body 138 
 
 96. Vibration and heart curves 138 
 
 97. Ludwig and Fick's kymographs 141 
 
 ♦98. Ludwig's improved revolving cylinder (Hermann) 142 
 
 *99. Blood-pressure tracing of the carotid of a dog (Hermann) 143 
 
 *ioo. Fick's spring manometer, by Hering (Hermann) 144 
 
 101. Fick's flat-spring kymograph 144 
 
 *I02. Scheme of height of blood pressure . . . 145 
 
 *I03. Depressor curve (Stirling) 147 
 
 104. Blood pressure and respiration tracings taken simultaneously 147 
 
 *ios. Blood pressure tracing during stimulation of the vagus (Stirling) . 149 
 
 # ' V Apparatus of v. Kries for capillary pressure (C Ludwig) 151 
 
 *io8. Scheme of the blood pressure , . . . 152 
 
 109. Volkmann's haemadromometer 156 
 
 1 10. Ludwig and Dogiel's rheometer 156 
 
 111. Vierordt's hEematachometer 1 56 
 
 112. Dromograph 157 
 
 113. Scheme of sectional arei (after Yeo) 157 
 
 114. Diapedesis 162 
 
 115. Various forms of venous pulse . . .... 166 
 
 116. Mosso's plethysmograph , , 168 
 
 *II7> Trabecular of the spleen (Cadiat) . , . . . 172 
 
 *n8. Adenoid tissue of spleen (Cadiat) 172 
 
 *II9. Malpighian corpuscle of the spleen (Capiat) 173 
 
 *I20. Tracing of a splenic curve (Roy) . . 176 
 
 *I2I. Thymus gland (Cadiat) 178 
 
ILLUSTRATIONS. XX1U 
 
 FIGURE PAGE 
 
 *I22. Elements of the thymus gland (Cadiat) 178 
 
 *I23. Thyroid gland (Cat/tat) 179 
 
 *I24. Suprarenal capsule (Cadiat) 180 
 
 •125. Human bronchus (Hamilton) 184 
 
 *I26. Air vesicles injected with silver nitrate (Hamilton) 186 
 
 127. Scheme of the air vesicles of lung 187 
 
 *I28. Interlobular septa of lung (Hamilton) 188 
 
 129. Scheme of Hutchinson's spirometer 191 
 
 130. Marey's stethograph (M' Kendrick) 193 
 
 131. Brondgeest's tambour and curve 193 
 
 132. Pneumatogram ; 194 
 
 133. Section through diaphragm (Hermann) 198 
 
 134. Action of intercostal muscles 199 
 
 135. Cyrtometer curve 201 
 
 136. Sibson's thoracometer 202 
 
 137. Topography of the lungs and heart 202 
 
 138. Andral and Gavarret's respiration apparatus 210 
 
 139. Scharling's apparatus 210 
 
 140. Regnault and Reiset's apparatus ... 211 
 
 141. v. Pettenkofer's apparatus 211 
 
 142. Valentin and Brunner's apparatus 213 
 
 143. Ciliated epithelium (Schenk) 225 
 
 144. Objects found in sputum 223 
 
 *I45. Squamous epithelium of mouth 232 
 
 146. Mucous follicle (Schenk) 233 
 
 147. Rodded epithelium of a salivary duct 233 
 
 148. Histology of the salivary glands 234 
 
 *I49. Human sub-maxillary gland (Heidenhain) 235 
 
 #,»,' \ Sections of a serous gland (Heidenhain) 236 
 
 *i 52. Diagram of a salivary gland (L. Brunton) 240 
 
 153. Apparatus for estimation of sugar 247 
 
 154. Polarization apparatus 247 
 
 155. Vertical section of a tooth 250 
 
 156. Dentine 250 
 
 157. Interglobular spaces 250 
 
 158. Dentine and enamel 251 
 
 159. Dentine and crusta petrosa 251 
 
 160. ") 
 
 161. \ Development of a tooth 252 
 
 162. J 
 
 163. Section of oesophagus (Schenk) 256 
 
 164. Perinseum and its muscles 260 
 
 165. Levator ani externus and internus 261 
 
 *l66. Auerbach's plexus (Cadiat) 263 
 
 *i67. Meissner's plexus (Cadiat) . . ... 264 
 
 168. Goblet cells 266 
 
 169. Surface section of gastric mucous membrane 266 
 
 170. Fundus gland of the stomach 267 
 
 171. Pyloric gland 267 
 
 172. Scheme of the gastric mucous membrane 268 
 
 •173. Pyloric mucous membrane (Hermann) 270 
 
 *I74- Pyloric glands during digestion (Hermann) 270 
 
 *I75- Scheme of pyloric fistula (Stirling) 271 
 
 *I7<>. Section of the tubes of the pancreas (Hermann) 278 
 
 177. Changes of the pancreatic cells during activity 279 
 
 178. Scheme of a liver lobule 285 
 
 *I79- Human liver cells (Cadiai) 2 gg 
 
 *l8o. Liver cells during fasting (Hermann) 286 
 
 181. Bile ducts 287 
 
 182. Various appearances of the liver cells 287 
 
 183. Interlobular bile duct \ 287 
 
 •184. Cholesterin (Aitken) ... 296 
 
 *l8S- Biliary fistulse (Stirling) 298 
 
 186. Longitudinal section of the small intestine (Schenk) -504 
 
 187. Transverse section of Lieberkiihn's follicles (Schenk) 305 
 
XXIV ILLUSTRATIONS. 
 
 FIGURE PAGE 
 
 *i88. Schemata of intestinal fistulse {Stirling) 305 
 
 *i8(). Moreau's fistula (after Brunton) 306 
 
 190. Bacterium aceti and B. butyricus 308 
 
 191. Bacillus subtilis 309 
 
 192. Bacteria of faeces 313 
 
 *I93. Scheme of intestinal absorption (Beaunis) 319 
 
 ♦194. Villi of small intestine injected (Cadiat) 320 
 
 195. Scheme of an intestinal villus 320 
 
 196. Injected villus (Schenk) 321 
 
 *I97- Villi and Lieberkiihn's follicles ( Cadiat) 322 
 
 *I98. Section of a solitary follicle (Cadiat) 323 
 
 *I99. Section of a Peyer's patch ( Cadiat) ... . . 323 
 
 *20o. Section of Auerbach's plexus ( Cadiat) . 324 
 
 201. Section of large intestine (ScAeni) 324 
 
 *202. Lieberkiihn's gland (Hermann) 325 
 
 203. Endosmometer 326 
 
 204. Origin of lymphatics in the tendon of diaphragm 333 
 
 *205. Lymphatics of diaphragm silvered (Jianvier) 334 
 
 206. Perivascular lymphatics 334 
 
 207. Stomata from lymph sack of frog 334 
 
 208. Section of two lymph follicles 335 
 
 *209. Scheme of a lymphatic gland (Sharpey) 336 
 
 210. Part of a lymphatic gland 337 
 
 *2ii. Section of the central tendon of diaphragm (Brunton) 342 
 
 *2I2. Section of fascia lata of a dog (Brunton) 342 
 
 *2I3- Lymph hearts (Ecker) 343 
 
 214. Water calorimeter of Favre and Silbermann 347 
 
 215. Walferdin's metastatic thermometer 351 
 
 216. Scheme of thermo-electric arrangements . . 352 
 
 217. Kopp's apparatus for specific heat 356 
 
 218. Daily variations of temperature 359 
 
 *2I9. Acini of the mammary gland of a sheep (Cadiat) 375 
 
 220. Milk glands during inaction and secretion 376 
 
 *22i. Milk and colostrum (Stirling) 377 
 
 *222. Section of a grain of wheat (Blylh) 384 
 
 223. Yeast cells growing 387 
 
 224. Composition of animal and vegetable foods 391 
 
 *225. Starch grains 416 
 
 *226. Longitudinal section of the kidney (Henle) 419 
 
 *227. Malpighian pyramid ( Tyson after Ludwig) 420 
 
 228. Scheme of the uriniferous tubules (Klein and Noble Smith) 421 
 
 229. Scheme of the structure of the kidney 422 
 
 230. Glomerulus and renal tubules 423 
 
 *23I. Convoluted renal tubule (Heidenhain) ... . 424 
 
 *232. Irregular tubule ( Tyson after Klein) 424 
 
 *233. Transverse section of the apex of a Malpighian pyramid (Cadiat) 426 
 
 *234- Development of a glomerulus ( Cadiat) 426 
 
 235A.Graduated urinary flask 427 
 
 23SB.Urinometer 427 
 
 236. Graduated burette 429 
 
 237. Urea and urea nitrate 430 
 
 ♦238. Oxalate of urea (after Beale) 431 
 
 239. Urameter (Charteris) 433 
 
 240. Squibb's method for urea (Martindale) 433 
 
 241. Graduated pipette 433 
 
 ♦242. Uric acid .... 434 
 
 *243- Uric acid ( Wedl ) 434 
 
 244. Kreatinin-zinc chloride 437 
 
 *245- Oxalate of lime ( Wedl) 437 
 
 *246. Oxalate of lime 437 
 
 247. Hippuric acid 438 
 
 248. Spermatozoa and calcic phosphate 442 
 
 249. Deposit in urine during the " acid fermentation " 444 
 
 250. Deposit in ammoniacal urine 444 
 
 251. Deposit in ammoniacal urine 444 
 
 *252. Ammonio-magnesic phosphate and urates 444 
 
ILLUSTRATIONS. XXV 
 
 FAGB 
 
 PIGURK 
 
 253. Blood corpuscles in urine 44° 
 
 254. Peculiar forms of blood corpuscles 44$ 
 
 255. Colored and colorless corpuscles in urine 449 
 
 256. Blood corpuscles and triple phosphate 449 
 
 257. Spectroscopic examination of urine 45° 
 
 *257A.Picro-Saccharimeter {G.Johnson) ... . 4S3 
 
 ♦258. Inosit {Beak after Funke) 453 
 
 259. Cystin and oxalate of lime 454 
 
 260. Leucin, tyrosin and ammonium urate 454 
 
 261. Epithelium from the genito-urinary apparatus 455 
 
 262. Micrococci and fungi in urine 45^ 
 
 263. Blood and granular tube casts 456 
 
 264. Hyaline casts 457 
 
 *26S- Oncometer (Stirling, after Roy) 467 
 
 *266. Oncograph {Stirling, after Hoy) 4°7 
 
 *267. Renal oncograph curve (Stirling, after Soy) 468 
 
 *268. Transitional epithelieum (Beale) .... 47 ' 
 
 269. View of the trigone of the bladder 47 1 
 
 *27o. Nervous mechanism of micturition (Power) 474 
 
 *27i. Section of epidermis and its nerves 477 
 
 272. Scheme of the structure of the skin 478 
 
 273. Vertical section of the skin . ... 479 
 
 *274. Papillae of the skin injected ... 479 
 
 *275. Margarin crystals in fat cells 479 
 
 276. Transverse section of a nail 480 
 
 277. Transverse section of a hair follicle 481 
 
 278. Section of a hair follicle 481 
 
 279. Sebaceous gland 483 
 
 280. Ciliated epithelium 491 
 
 281. Histology of muscular tissue 494 
 
 *282. Muscular fibre (Quain) 495 
 
 2S3. Tendon attached to a muscle 496 
 
 ♦284. Injected blood vessels of muscle (Kolliker) 496 
 
 285. Motorial end plates 497 
 
 286. Termination of a nerve in muscle .... 498 
 
 •287. Nerve ending in smooth muscle ( Cadiat) 499 
 
 *288. Non-striped muscle cell (Stirling) 499 
 
 ♦289. Frog with its sciatic artery ligatured 508 
 
 *290. Scheme of the curara experiment (after Rutherfora) 509 
 
 *29I. Platinum electrodes (Elliott Brothers) 509 
 
 292. Microscopic appearances in contracting muscle 512 
 
 293. Helmholtz's myograph . . .... 513 
 
 *294- Pendulum myograph 514 
 
 *295- Scheme of the pendulum myograph {Stirling) . . , 515 
 
 ♦296. Du Bois-Reymond's spring myograph 516 
 
 297. Muscle curve 5 J 6 
 
 *298. Muscle curve (Rutherford) 517 
 
 *299. Method of studying a muscular contraction (after Rutherford) . 518 
 
 300. Muscle curves 519 
 
 301. Muscle curves, opening and closing shocks . 519 
 
 302. Muscle curves, tetanus 521 
 
 *303. Curves of a red and pale muscle (Kronecker and Stirling) .... . . . . 522 
 
 *304. Muscle curves (Kronecker and Stirling) 522 
 
 ♦305. Tone inductorium (Kronecker and Stirling) 522 
 
 *3o6. Muscle curves (Marey) " 5 2 4 
 
 *307. Height of the lift by a muscle 525 
 
 *3o8. Dynamometer 5 2 ^ 
 
 ♦309. Curves of elasticity (after Marey) ... 527 
 
 *3io. Curve of elasticity of a muscle {after Marey) 527 
 
 311. Curve of elasticity (Marey) 527 
 
 *3I2. Fatigue curve (Waller) 533 
 
 *3I3. Orders of levers , . 536 
 
 *3I4. Scheme of the action of muscles on bones . . . 537 
 
 315. Phases of walking 541 
 
 316. Instantaneous photograph of a person walking 542 
 
 317. Instantaneous photograph of a runner 543 
 
XXVI ILLUSTRATIONS. 
 
 FIGURE 
 
 318. Instantaneous photograph of a person jumping 543 
 
 319. Larynx from the front . . . 546 
 
 320. Larynx from behind . . 546 
 
 321. Larynx from behind 547 
 
 322. Nerves of the larynx 547 
 
 323. Action of the posterior crico-arytenoid muscles 548 
 
 324. Action of the arytenoid muscles 548 
 
 325. Action of the lateral crico-arytenoid muscles 549 
 
 326. Vertical section of the head and neck 550 
 
 327. Examination of the larynx . .. 551 
 
 328. Laryngoscopic view of the larynx 552 
 
 329. "View of the larynx during a high note 553 
 
 330. View of the larynx during a deep inspiration 553 
 
 331. Rhinoscopy 553 
 
 332. View of the posterior nares 553 
 
 333. Parts concerned in phonation . . . 556 
 
 334. Tumors on the vocal cords 558 
 
 335. Histology of nervous tissues . . . 562 
 
 *33§. Sympathetic nerve fibre (Ranvier) .... ... . . 563 
 
 *337. Transverse sections of nerve fibres ... 563 
 
 338. Medullated nerve fibre 563 
 
 *339> Ranvier's crosses {Ranvier) . . 563 
 
 340. Transverse section of a nerve 565 
 
 *34I. Cell from the Gasserian ganglion (Schwalie) ... .... . . . . 566 
 
 342. Degeneration and regeneration of nerve fibres ... 573 
 
 *343- Waller's experiments (after Dalton) 574 
 
 344. Rheocord of Du Bois Reymond ... 578 
 
 345. Scheme of a galvanometer .... . . 580 
 
 *34o. Large Grove's battery (Gscheidlen) 580 
 
 *347. Grennet's battery ( Gscheidlen) . . . . 581 
 
 *348. Leclanche's element (Gscheidlen) ... . . 581 
 
 *349. Non-polarizable electrodes (Elliott Brothers) . . . . 582 
 
 *350. Thomson's galvanometer (Elliott Brothers) . . . . 583 
 
 *35 1 . Lamp and scale (Elliott Brothers) ... . . . . 583 
 
 *352. Galvanometer shunt (Elliott Brothers) ... . . 583 
 
 *353. Scheme of the induced currents (Hermann) 585 
 
 *354. Helmholtz's modification (Hermann) 585 
 
 355. Scheme of an induction machine 586 
 
 *35o. Inductorium (Elliott Brothers) 587 
 
 357. Stohrer's apparatus 1:87 
 
 *358. Friction key (Elliott Brothers) 587 
 
 *359. Plug key (Elliott Brothers) '.'.'. 588 
 
 *3§o. Capillary contact (Kronecker and Stirling) 588 
 
 361. Scheme of the muscle current 589 
 
 362. Capillary electrometer 589 
 
 *363. Secondary contraction 392 
 
 *364. Nerve-muscle preparation jg2 
 
 365. Bernstein's differential rheotome 503 
 
 366. Nerve current in electrotonus cnc 
 
 367. Scheme of electrotonic excitability cn8 
 
 368. Method of testing electrotonic excitability 500, 
 
 369. Distribution of an electrical current 500, 
 
 370. Velocity of nerve energy ... 603 
 
 *37i. Scheme for testing velocity of a nerve impulse 604 
 
 *372. Curves of a nerve impulse (Marey)' 604 
 
 *373- Sponge rheophores ( Weiss) 6oy 
 
 *374. Disk rheophore ( Weiss) 607 
 
 *375. Metallic brush ( Weiss) 607 
 
 376. Motor points of the arm 603 
 
 377. Motor points of the arm 6 8 
 
 378. Motor points of the leg . . 6 o 
 
 379. Motor points of the leg ... . 6l 
 
 *38o. Scheme of a reflex act (Stirling) 6,5 
 
 381. Optic chiasma 61 y 
 
 *382. Decussation of the optic tracts ( Charcot) D1 g 
 
 *383. Scheme of images in squinting (Bristovie) gjq 
 
ILLUSTRATIONS. XXV11 
 
 FIGURE PAGE 
 
 384. Medulla oblongata 620 
 
 *38s. Under surface of the brain 622 
 
 386. Connections of the cranial nerves 625 
 
 387. Sensory nerves of the face 629 
 
 388. Motor points of the face and neck 633 
 
 *389. Disposition of the semicircular canals ( W. Stirling) 636 
 
 *390. Cardiac nerves of the rabbit ( W. Stirling) 640 
 
 *39I. Spinal ganglion (Cadiat) 646 
 
 392. Cutaneous nerves of the arm 647 
 
 393. Cutaneous nerves of the leg (Henle) 647 
 
 394. Transverse section of the spinal cord 654 
 
 *395. Transverse section of the white matter [Cadiat) 655 
 
 *39§. Multipolar nerve cells of the cord ( Cadiat) 655 
 
 *397. Relation of white and gray matter of the cord (Schafer) 655 
 
 *398. Transverse sections of the spinal cord 656 
 
 *399. Transverse section of the cord (Cadiat) 657 
 
 *400. Longitudinal section of the cord (Cadiat) 658 
 
 *40I. Multipolar nerve cell 658 
 
 *402. Injected blood vessels of the cord (KSlliker) 658 
 
 403. Conducting paths in the cord 658 
 
 *404. Degeneration paths in the cord (Bramwell) 660 
 
 ♦405. Scheme of a reflex act ( W. Stirling) 661 
 
 *406. Section of a spinal segment ( W. Stirling) 661 
 
 *407. Propagation of reflex movements (Beaunis) 662 
 
 *4o8. Effect of section on half of the cord (Erb) 674 
 
 *409. Brain, ventricles and basal ganglia . 675 
 
 410. Scheme of the brain 676 
 
 *4U. Connections of the cerebellum 677 
 
 *4I2. Diagram of a spinal segment (Bramwell) 680 
 
 *4I3. Section across the pyramids (Schwalbe) 681 
 
 *4I4. Section of the medulla oblongata (Schwalbe) 683 
 
 *4I5. Section of the olivary body (Schwalbe) 683 
 
 *4i6. Scheme of the respiratory centres (Rutherford) 687 
 
 ♦417. Scheme of the accelerans flbres ( iV. Stirling) 693 
 
 *4l8. Cardiac plexus of a cat (BShm) 694 
 
 *4I9- Frog without its cerebrum (Stirling, after Goltz) 705 
 
 *420. Frog without its cerebrum (Stirling, after Goltz) 705 
 
 *42I. Pigeon with its cerebrum removed (after Dalton) 705 
 
 *422. Cerebral convolution 709 
 
 ♦423. Cerebral convolution injected ... . 710 
 
 *424> Left side of the human brain (Ecker) .... 711 
 
 ♦425. Inner aspect of right hemisphere (Ecker) 712 
 
 *42o. Left frontal lobe and island of Reil (Turner) 713 
 
 *427. Brain from above (Ecker) 714 
 
 428. Cerebrum of dog, carp, frog, pigeon, and rabbit . 716 
 
 429. Relation of the cerebral convolutions to the skull 717 
 
 *430. Motor centres (after Schafer and Horsley) 718 
 
 *43I. Motor areas (after Gowers) 719 
 
 432. Psycho-optic fibres (Munk) 722 
 
 *433- Section of a cerebral hemisphere (Horsley) ■ 726 
 
 *434. Secondary degeneration in a crus ( Charcot) 728 
 
 *43S. Transverse section of the crus cerebri (Charcot) 728 
 
 *43<>. Scheme of aphasia (Lichtheim) 730 
 
 *437. Scheme of aphasia (Lichtheim) ■ 730 
 
 *438. Relation of the convolutions to the skull (R. W. Reid) 732 
 
 *439. Basal ganglia and the ventricles 734 
 
 *440. Transverse section of the right hemisphere ( Gegenbaur) 736 
 
 *44I. Fibres in pons (Erb) 736 
 
 *442. Section of the cerebellum (Sankey) 740 
 
 *443. Cortex cerebri and its membranes (Schwalbe) 740 
 
 *444. Pigeon with its cerebellum removed (Dalton) 742 
 
 *445. Circle of Willis (Charcot) \ 744 
 
 *44&. Ganglionic arteries ( Charcot) 74c 
 
 *447. Corneal corpuscles (Ranvier) 750 
 
 *448. Corneal spaces (Ranvier) 750 
 
 .449. Junction of the cornea and sclerotic 751 
 
XXV111 ILLUSTRATIONS. 
 
 FIGURE PAGE 
 
 *45o. Vertical section of cornea {Ranvier) 752 
 
 *45i. Horizontal section of cornea {Ranvier) . .... 752 
 
 452. Blood vessels of the eyeball 753 
 
 *4S3. Vertical section human retina {Cadiat) 755 
 
 454. Layers of the retina 755 
 
 *45S. Vertical section of the fovea centralis {Cadiat) 756 
 
 *4S6. Fibres of the lens {Kolliker) 757 
 
 457. Section of the optic nerve . . 758 
 
 458. Action of lenses on light 760 
 
 459. Refraction of light 760 
 
 460. Construction of the refracted ray 760 
 
 461. Optical cardinal points 762 
 
 462. Construction of the refracted ray 762 
 
 463. Construction of the image 763 
 
 464. Refracted ray in several media 763 
 
 465. Visual angle and retinal image 764 
 
 466. Scheme of the ophthalmometer 765 
 
 467. Horizontal section of the eyeball 767 
 
 468. Scheme of accommodation 767 
 
 469. Sanson-Purkinje's images 768 
 
 *470. Phakoscope (M' Kendrick) 768 
 
 • 471. Scheiner's experiment 770 
 
 472. Refraction of the eye 771 
 
 473. Myopic eye 771 
 
 474. Hypermetrophic eye 772 
 
 475. Power of accommodation 772 
 
 *476. Diagram of astigmatism {Frost) 775 
 
 477. Cylindrical glasses 775 
 
 *478. Scheme of the nerves of the iris {Erb) 777 
 
 *479. Pupilometer ( Gorham) 778 
 
 *48o. Pupilometer {Gorham) 778 
 
 481. Entoptical shadows . . . . . 779 
 
 482. Scheme of the original ophthalmoscope . 781 
 
 483. Scheme of the indirect method v 782 
 
 484. Action of a divergent lens 782 
 
 485. Action of a divergent lens . 782 
 
 486. View of the fundus oculi 783 
 
 *487. Morton's ophthalmoscope {Pickard and Curry) . . 783 
 
 *488. Frost's artificial eye {Frost) . . 784 
 
 489. Action of the orthoscope . 784 
 
 *490. Mariotte's experiment . 785 
 
 491. Horizontal section of the right eye . 786 
 
 *492. M'Hardy's perimeter {Pickard and Curry) . . 787 
 
 *493. Priestley Smith's perimeter {Pickard and Curry) . 788 
 
 494. Perimetric chart .... 789 
 
 495. Geometrical color cone . 792 
 
 496. Action of light rays on the retina , 793 
 
 *497. Cones of the retina {Stirling, after Engelmann) 797 
 
 *498. Irradiation 797 
 
 499. Scheme of the action of the ocular muscles 802 
 
 500. Identical points of the retina 804 
 
 501. The horopter _ 804 
 
 502. Two stereoscopic drawings .... .... ... 805 
 
 503. Brewster's stereoscope 806 
 
 504. Wheatstone's stereoscope 806 
 
 505. Telestereoscope t 807 
 
 506. Wheatstone's pseudoscope 807 
 
 507. Rollett's apparatus ... , . 809 
 
 ♦508. Zollner's lines 809 
 
 509. Section of an eyelid 811 
 
 510. Scheme of the organ of hearing , 814 
 
 511. External auditory meatus ... 816 
 
 512. Left tympanic membrane and ossicles ^lj 
 
 513. Membrana tympani and ossicles 817 
 
 514. Tympanic membrane from within 817 
 
ILLUSTRATIONS. XXIX 
 
 FIGURE PAGB 
 
 *5I5. Ear specula (Krohne and Sesemann) 818 
 
 *Si6. Toynbee's artificial membrana tympani [Krohne and Sesemann) 818 
 
 517. Right auditory ossicles 818 
 
 518. Tympanum and auditory ossicles 819 
 
 519. Tensor tympani and Eustachian tube 821 
 
 520. Right stapedius muscle 822 
 
 *52I. Eustachian catheter 823 
 
 *522. Politzer's ear- bag [Krohne and Sesemann) 823 
 
 523. Right labyrinth 824 
 
 524. Scheme of the cochlea 825 
 
 ♦525. Interior of the right labyrinth 826 
 
 *S26. Semicircular canals 826 
 
 527. Scheme of the canalis cochlearis 827 
 
 *528. Gal ton's whistle (Krohne and Sesemann) 829 
 
 529. Curve of a musical note and its overtones 831 
 
 *530. Kcenig's manometric capsule (Kcenig) 832 
 
 *53I. Flame pictures of vowels (Kcenig) 833 
 
 *532. Kcenig's analyzing apparatus (Kcenig) 835 
 
 533. Olfactory cells 839 
 
 534. Nasal and pharyngo-nasal cavities 839 
 
 535. Circumvallate papilla and taste bulbs 841 
 
 *53§. Wagner's touch corpuscle (Ranvier) 844 
 
 537. Vertical section of skin 844 
 
 538. Pacini's corpuscle 845 
 
 *539. Bouchon epidermique (Ranvier) 846 
 
 540. ^Esthesiometer 847 
 
 541. ^Esthesiometer of Sieveking 848 
 
 *542. Aristotle's experiment 849 
 
 543. Landois' pressure mercurial balance 850 
 
 *544. Karyokinesis ( Gegenbaur) 856 
 
 *S4S. Section of testis (Schenk) '. 858 
 
 *546. Tubule of testis (Schenk) 859 
 
 *S47. Section of epididymis (Schenk) 859 
 
 548. Spermatic crystals 860 
 
 549. Spermatozoa 861 
 
 550. Spermatogenesis 861 
 
 *55I. A cat's ovary (Hart and Barbour, after Schron) 862 
 
 *552. Section of an ovary ( Turner) 863 
 
 553. Ovary and polar globules 864 
 
 *554. Mucous membrane of the uterus (Hart and Barbour, after Turner) 865 
 
 *S55. Fallopian tube and its annexes (Henle) 866 
 
 *S56. Section of Fallopian tube (Schenk) 867 
 
 *S57. Uterus before menstruation (J. Williams) 868 
 
 *558. Uterus after menstruation (J. Williams) 868 
 
 *559. Erectile tissue ( Cadiat) 869 
 
 560. The urethra and adjoining muscles 871 
 
 561. Cleavage of the yelk 874 
 
 562. The blastoderm 875 
 
 563. Schemata of development 876 
 
 ♦564. Embryo of the mole (W. K. Parker) 881 
 
 ♦565. Uterine^ mucous membrane (Coste) 883 
 
 *566. Placental villi (Cadiat) 884 
 
 567. Hare lip 889 
 
 *S68. Meckel's cartilage ( W. K. Parker) 889 
 
 569. Centres of ossification in the innominate bone 890 
 
 570. Development of the heart 893 
 
 571. The aortic arches 893 
 
 572. Veins of the embryo 894 
 
 573. Development of the veins and portal system 895 
 
 574. Development of the intestine 896 
 
 575. Development of the lungs 896 
 
 576. Formation of the omentum 896 
 
 577. Development of the internal generative organs 897 
 
XXX 
 
 ILLUSTRATIONS. 
 
 FIGURE 
 
 578. Development of the external genitals 
 
 *579- " 
 *S8o. 
 *58i. 
 *S82. 
 583. Development of the eye 
 
 ■ Changes in the external organs of generation in the female (after Schrceder) 
 
 PAGE 
 
 899 
 900 
 900 
 900 
 900 
 901 
 
 [The illustrations indicated by the word Hermann are from Hermann's Handbuch der Physi- 
 ologic; by Cadiat, from Cadiat's Train d' Anatomic Ginirale; by Ranvier, from Ranvier's Traiti 
 Technique d' Histologic ; by Brunton, from The Practitioner; Brunton's Text-Book of Pharma- 
 cology, Therapeutics, and Materia Medico ; by Schenk, from Schenk's Grundriss der normalen 
 Histologic; by Ecker, from Ecker's Anatomic des Prosches.J 
 
INTRODUCTION. 
 
 THE SCOPE OF PHYSIOLOGY AND ITS RELATIONS TO OTHER BRANCHES 
 OF NATURAL SCIENCE. 
 
 Physiology is the science of the vital phenomena of organisms, or, broadly, 
 it is the Doctrine of Life. Correspondingly to the divisions of organisms, we 
 distinguish — (i) Animal Physiology ; (2) Vegetable Physiology ; and {$) the Physi- 
 ology of the Lowest Living Organisms, which stand on the border line of animals 
 and plants, i. e., the so-called Protista of H»ckel, micro-organisms, and those 
 elementary organisms or cells which exist on the same level. 
 
 The object of Physiology is to establish these phenomena, to determine their 
 regularity and causes, and to refer them to the general fundamental laws of 
 Natural Science, viz., the Laws of Physics and of Chemistry. 
 
 The following Scheme shows the relation of Physiology to the allied branches 
 of Natural Science : — 
 
 BIOLOGY. 
 
 The science of organized beings or organisms (animals, plants, protista;, and 
 elementary organisms). 
 
 I. MORPHOLOGY. 
 
 The doctrine of the form of organ- 
 
 General 
 Morphology. 
 
 The doctrine of the 
 formed elementary 
 constituents of or- 
 ganisms. 
 
 (Histology) — 
 (a) Histology of 
 
 Plants. 
 (i) Histology of Ani- 
 mals. 
 
 Special 
 Morphology. 
 
 The doctrine of the 
 parts and organs of 
 organisms. 
 
 (Organology 
 Anatomy) — 
 
 (a) Phytotomy. 
 
 (6) Zootomy. 
 
 II. PHYSIOLOGY. 
 
 The doctrine of the vital phenom. 
 ena of organisms. 
 
 General 
 Physiology. 
 
 The doctrine of vital 
 phenomena in gen- 
 eral — 
 
 (a) Of Plants. 
 
 (d) Of Animals. 
 
 Special 
 Physiology. 
 
 The doctrine of the 
 activities of the in- 
 dividual organs — 
 
 (a) Of Plants. 
 
 (6) Of Animals. 
 
 III. EMBRYOLOGY. 
 
 The doctrine of the generation and development of organisms. 
 
 Morphological part of the doc- 
 trine of development, i. e., 
 the doctrine of form in its 
 stages of development — 
 
 (a) General. 
 
 (b) Special. 
 
 1. History of the development 
 of single beings, of the indi- 
 vidual (e. g., of man) from the 
 ovum onward (Ontogeny) — 
 
 (a) In Plants. 
 (i) In Animals. 
 
 2. History of the development 
 of a whole stock of organisms 
 from the lowest forms of the 
 series upward (Phylogeny) — 
 
 (a) In Plants. 
 (i) In Animals. 
 xxxi 
 
 Physiological part of the doc- 
 trine of development, i. e., 
 the doctrine of the activity 
 during development — 
 
 (a) General. 
 
 (6) Special. 
 
XXX11 INTRODUCTION. 
 
 I 
 
 Morphology and Physiology are of equal rank in biological science, and a 
 previous acquaintance with Morphology is assumed as a basis for the comprehen- 
 
 li sion of Physiology, since the work of an organ can only be properly understood 
 when its external form and its internal arrangements are known. Development 
 occupies a middle place between Morphology and Physiology ; it is a morpho- 
 
 j logical discipline in so far as it is concerned with the description of the parts of 
 the developing organism ; it is a physiological doctrine in so far as it studies the 
 activities and vital phenomena during the course of development. 
 
 MATTER. 
 
 The entire visible world, including all organisms, consists of matter, i. e., of 
 substance which occupies space. 
 1 We distinguish ponderable matter which has weight, and imponderable matter 
 ' which cannot be weighed in a balance. The latter is generally termed ether. 
 f In ponderable materials, again, we distinguish their form, i. e., the nature of 
 / their limiting surfaces ; further, their volume, i. e. , the amount of space which 
 ' they occupy; and lastly, their aggregate condition, i. e., whether they are solid, 
 fluid, or gaseous bodies. 
 
 Ether. — The ether fills the space of the universe, certainly as far as the most 
 distant visible stars. This ether, notwithstanding its imponderability, possesses 
 distinct mechanical properties ; it is infinitely more attenuated than any known 
 kind of gas, and behaves more like a solid body than a gas, resembling a gelatin- 
 ous mass rather than the air. It participates in the luminous phenomena due to 
 the vibrations of the atoms of the fixed stars, and hence it is the transmitter of 
 light, which is conducted by means of its vibrations, with inconceivable rapidity 
 (42,220 geographical miles per second) to our visual organs (Tyndall). 
 
 Imponderable matter (ether) and ponderable matter are not separated sharply 
 from each other ; rather does the ether penetrate into all the spaces existing 
 between the smallest particles of ponderable matter. 
 
 ^ Particles. — Supposing that ponderable matter were to be subdivided continu- 
 
 / ously into smaller and smaller portions, until we reached the last stage of division 
 
 I in which it is possible to recognize the aggregate condition of the matter operated 
 
 ■ upon, we should call the finely-divided portions of matter in this state particles. 
 
 Particles of iron would still be recognized as solid, particles of water as fluid, 
 
 particles of oxygen as gaseous. 
 
 Molecules. — Supposing, however, the process of division of the particles to 
 
 be carried further still, we should at last reach a limit beyond which, neither 
 
 by mechanical nor by physical means, could any further division be effected. 
 
 1 We should have arrived at the molecules.. A molecule, therefore, is the smallest 
 
 I amount of matter which can still exist in a free condition, and which as a unit 
 
 J no longer exhibits the aggregate condition. 
 
 Atoms. — But even molecules are not the final units of matter, since every 
 \molecule consists of a group of smaller units, called atoms. An atom cannot 
 f exist by itself in a free condition, but the atoms unite with other similar or dis- 
 j similar atoms to form groups, which are called molecules. Atoms are incapable 
 lof further subdivision, hence their name. We assume that the atoms are invari- 
 ably of the same size, and that they are solid. From a chemical point of view, 
 the atom of an elementary body (element) is the smallest amount of the element 
 which can enter into a chemical combination. Just as ponderable matter consists 
 1 in its ultimate parts of ponderable atoms, so does the ether consist of analogous 
 small ether atoms. 
 
 Ponderable and Imponderable Atoms. — The ponderable atoms within 
 
 ponderable matter are arranged in a definite relation to the ether atoms. The 
 
 (ponderable atoms mutually attract each other, and similarly they attract the im- 
 
 Jponderable ether atoms ; but the ether atoms repel each other. Hence, in pon- 
 
INTRODUCTION. XXX111 
 
 derable masses, ether atoms surround every ponderable atom. These masses, in 
 virtue of the attraction of the ponderable atoms, tend to come together, but only 
 to the extent permitted by the surrounding ether atoms. Thus the ponderable 
 atoms can never come so close as not to leave interspaces. All matter must, 
 therefore, be regarded as more or less loose and open in texture, a condition due 
 to the interpenetrating ether atoms, which resist the direct contact of the ponder- 
 able atoms. 
 
 Aggregate Condition of Atoms. — The relative arrangement of the mole- 
 cules, i. e., the smallest particles of matter which can be isolated in a free condi- 
 tion, determines the aggregate condition of the body. 
 
 Within a solid body, characterized by the permanence of its volume as well as 
 by the independence of its form, the molecules are so arranged that they cannot 
 readily be displaced from their relative position. 
 
 Fluid bodies, although their volume is permanent, readily change their shape, 
 and their molecules are in a condition of continual movement. 
 
 When this movement of the molecules takes so wide a range that the individual 
 molecules fly apart, the body becomes gaseous, and as such is characterized by 
 the instability of its form as well as by the changeableness of its volume. 
 
 Physics is the study of these molecules and their motions. 
 
 FORCES. 
 
 i. Gravitation — Work done. — All phenomena appertain to matter. These 
 phenomena are the appreciable expression of the forces inherent in matter. The 
 forces themselves are not appreciable, they are the causes of the phenomena. 
 
 Gravitation. — The law of gravitation postulates that every particle of pon- 
 derable matter in the universe attracts every other particle with a certain force. 
 This force is inversely as the square of the distance. Further, the attractive force 
 is directly proportional to the amount of the attracting matter, without any refer- 
 ence to the quality of the body. We may estimate the intensity of gravitation 
 by the extent of the movement which it communicates to a body allowed to fall, i 
 for one second, through a given distance, in a space free from air. Such a body) 
 will fall in vacuo 9^809 metres per second. This fact has been arrived at experi- 
 mentally. ™ 
 
 Let us represent £• = 9.809 metres, the final velocity of the freely falling body at the end of one 
 second. The velocity, V, of the freely falling body is proportional to the time, t, so that 
 
 V=jf/ (1); 
 
 i.e., at the end of the 1st sec, V = g, I = g = 9.809 M — the distance traversed — 
 
 s^it*. (2); 
 
 i.e., the distances are as the square of the times. Hence, from (1) and (2) it follows (by eliminat- 
 ing /) that — 
 
 V=l/W (3)- 
 
 The velocities are as the square roots of the distances traversed — 
 
 V 2 
 Therefore, , = s (4). 
 
 *g 
 
 The freely falling body, and in fact every freely moving body,' possesses kinetic 
 
 energy, and is in a certain sense a magazine of energy. The kinetic energy of 
 
 any moving body is always equal to the product of its weight (estimated by the 
 
 balance), and the height to which it would rise from the earth, if it were thrown 
 
 from the earth with its own velocity. 
 
 Let W represent the kinetic energy of the moving body, and P its weight, then W = P.s, so that 
 from (4) it follows that — 
 
 W = P J (5). 
 
 Hence, the kinetic energy of a body is proportional to the square of its velocity, 
 c 
 
XXXIV INTRODUCTION. 
 
 Work. — If a force (pressure, strain, tension) be so applied to a body as to move 
 it, a certain amount of work is performed. The amount of work is equal to the 
 product of the amount of the pressure or strain which moves the body, and of the 
 distance through which it is moved. 
 
 Let K represent the force acting on the body, and S the distance, then the work W = KS. The 
 attraction between the earth and any body raised above it is a source of work. 
 
 It is usual to express the value of K in kilogrammes, and S in metres, so that 
 the "unit of work" is the kilogramme-metre, i.e., the force which is re- 
 quired to raise i kilo, to the height of i metre. 
 
 2. Potential Energy. — The transformation of Potential into Kinetic energy 
 
 and conversely : Besides kinetic energy, there is also "potential energy," or 
 
 energy of position. By this term are meant various forms of energy, which are 
 
 suspended in their action, and which, although they may cause motion, are not 
 
 in themselves motion. A coiled watch-spring kept in this position, a stone resting 
 
 i upon a tower, are instances of bodies possessing potential energy, or the energy of 
 
 i position. It requires merely a push to develop kinetic from the potential energy, 
 
 \^or to transform potential into kinetic energy. 
 
 Work, w, was performed in raising the stone to rest upon the tower. 
 
 ■w =J>, s, where/ = the weight and j.= the height. 
 p = m .g, is = the product of the mass (m), and the force of gravity ( g), so that m = m g s. 
 
 This is at the same time the expression for the potential energy of the stone. 
 This potential energy may readily be transformed into kinetic energy by merely 
 pushing the stone so that it falls from the tower. The kinetic energy of the stone 
 is equal to the final velocity with which it impinges upon the earth. 
 
 V = -\/2g s (see above (3) ). 
 V a = 2g s. 
 mV 2 = 2m gs. 
 
 —V 2 = m g s. 
 2 
 
 m gs was the expression for the potential energy of the stone while it was still rest- 
 ing on the height ; _ V 2 is the kinetic energy corresponding to this potential 
 2 
 
 energy (Briicke). 
 
 Potential energy may be transformed into mechanical energy under the most 
 varied conditions ; it may also be transferred from one body to another. 
 
 The movement of a pendulum is a striking example of the former. When the pendulum is at 
 ( the highest point of its excursion, it must be regarded as absolutely at rest for an instant, and as en- 
 i dowed with potential energy, thus corresponding with the raised stone in the previous instance. 
 1 During the swing of the pendulum this potential energy is changed into kinetic energy, which is 
 f greatest when the pendulum is moving most rapidly toward the vertical. As it rises again from the 
 vertical position, it moves more slowly, and the kinetic energy is changed into potential energy, 
 which once more reaches its maximum when the pendulum comes to rest at the utmost limit of its 
 excursion. Were it not for the resistances continually opposed to its movements, such. as the resist- 
 ance of the air and friction, the movement of the pendulum, due to the alternating change of kinetic 
 into potential energy and vice versS, would continue uninterruptedly, as with a mathematical pendu- 
 lum. Suppose the swinging ball of the pendulum, when exactly in a vertical position, impinged 
 upon a resting but moving sphere, the potential energy of the ball of the pendulum would be trans- 
 ferred directly to the sphere, provided that the elasticity of the ball of the pendulum and the sphere 
 were complete ; the pendulum would come to rest, while the sphere would move onward with an 
 equal amount of kinetic energy, provided there were no resistance' to its movement. This is an ex- 
 ample of the transference of kinetic energy from one body to another. Lastly, suppose that a 
 stretched watch-spring on uncoiling causes another spring to become coiled ; and we have another 
 example of the transference of kinetic energy from one body to another. 
 
 The following general statement is deducible from the foregoing examples : If, 
 in a system, the individual moving masses approach the final position of equili- 
 brium, then in this system the sum of the kinetic energies increases ; if, on the 
 
INTRODUCTION. XXXV 
 
 other hand, the particles move away from the final position of equilibrium, then 
 the sum of the potential energies is increased at the expense of the kinetic ener- 
 gies, i.e., the kinetic energies diminish (Brucke). 
 
 The pendulum, which, after swinging from the highest point of its excursion, approaches the ver- 
 tical position, i.e., the position of equilibrium of a passive pendulum, has in this position the largest 
 amount of potential energy ; as it again ascends to the highest point of its excursion on the other 
 side, it again gradually receives the maximum of potential energy at the expense of the gradually 
 diminishing movement, and, therefore, of the kinetic energy. 
 
 3. Heat. — Its Relation to Potential and Kinetic Energy. — If a lead weight be 
 thrown from a high tower to the earth, and if it strike an unyielding substance, the 
 movement of the mass of lead is not only arrested, but the kinetic energy (which 
 to the eye appears to be lost) is transformed into a lively vibratory movement of 
 the atoms. When the lead meets the earth, heat is produced. The amount of/ 
 heat produced is proportional to the kinetic energy, which is transformed through / 
 the concussion. At the moment when the lead weight reaches the earth, the atoms 
 are thrown into vibrations ; they impinge upon each other ; then rebound again from 
 each other in consequence of their elasticity, which opposes their direct juxtapo-, 
 sition ; they fly asunder to the maximum extent permitted by the attractive force i 
 of the ponderable atoms, and thus oscillate to and fro. All the atoms vibrate like ; 
 a pendulum, until their movement is communicated to the ethereal atoms surround-! 
 ing them on every side, i.e., until the heat of the heated mass is " radiated." Heat\ 
 is thus a vibratory movement of the atoms. 
 
 As the amount of heat produced is proportional to the kinetic energy, which is 
 transformed through the concussion, we must find an adequate measure for both 
 forces. 
 
 Heat Unit. — As a standard of measure of heat, we have the " heat unit " or 
 calorie. The "heat unit" or calorie is the amount of energy required to raise 
 the temperature of 1 gramme of water i° C. The " heat unit " corresponds to 
 425.5 gramme-metres, i.e., the same energy required to heat 1 gramme of water 
 i° C. would raise a weight of 425.5 grammes to the height of 1 metre ; or, a weight 
 of 425.5 grammes, if allowed to fall from the height of 1 metre, would by its con- 
 cussion produce as much heat as would raise the temperature of 1 gramme of water 
 i° C. The "mechanical equivalent" of the heat unit is, therefore, 425.5 
 gramme-metres. 
 
 It is evident that from the collision of moving masses an immeasurable amount of heat can be 
 produced. Let us apply what has already been said to the earth. Suppose the earth to be dis- 
 turbed in its orbit, and suppose further that, owing to the attraction of the sun, it were to impinge 
 on the latter (whereby, according to J. R. Mayer, its final velocity would be 85 geographical miles 
 per second), the amount of heat produced by the collision would be equal to that produced by the 
 combustion of a mass of pure charcoal more than 5000 times as heavy ( Julius Robert Mayer, Helm- 
 holtz). 
 
 Thus, the heat of the sun itself can be produced by the collision of masses of cold matter. If the 
 cold matter of the universe were thrown into space, and there left to the attraction of its particles, 
 the collision of these particles would ultimately produce the light of the stars. At the present time, 
 numerous cosmic bodies collide in space, while innumerable small meteors (94,000 to 188,000 bil- 
 lions of kilos., per minute) fall into the sun. The force of gravity is, perhaps, in fact, the only source 
 of all heat (J. R. Mayer, Tyndall). . 
 
 We have a homely example of the transformation of kinetic energy into heat in the fact that a 1 
 blacksmith may make a piece of iron red hot by hammering it. Of the conversion of heat into ki- 
 netic energy, we have an example in the hot watery vapor (steam) of the steam engine raising the 
 piston. An example of the conversion of potential energy into heat occurs in a metallic spring, 
 when it uncoils and is so placed as to rub against a rough surface, producing heat by friction. 
 
 4. Chemical Affinity : Relation to Heat. — While gravity acts upon the : 
 particles of matter without reference to the composition of the body, there is an- 
 other atomic force which acts between atoms of a chemically different nature ; this 1 
 is chemical affinity. This is the force in virtue of which the atoms of chemi- 1 
 cally different bodies unite to form a chemical compound. The force itself 
 varies greatly between the atoms of different chemical bodies ; thus we speak of 
 
XXXVI INTRODUCTION. 
 
 strong chemical affinities and weak affinities. Just as we were able to estimate the 
 potential energy of a body in motion from the amount of heat which was produced 
 when it collided with an unyielding body, so we can measure the amount of the 
 chemical affinity by the amount of heat which is formed when the atoms of chem- 
 ically different bodies unite to form a chemical compound. As a rule, heat 
 is formed when separate chemically different atoms form a compound body. 
 When, in virtue of chemical affinity, the atoms of i kilo, of hydrogen and 8 kilos, 
 of oxygen unite to form the chemical compound water, an amount of heat is there- 
 by evolved which is equal to that produced by a weight of 47,000 kilos, falling 
 and colliding with the earth from a height of 1000 feet above the surface of the 
 earth. If 1 gram, of H be burned along with the requisite amount of O to form 
 water, it yields 34,460 heat units or calories; and 1 gram, carbon burned 
 to carbonic acid (carbon dioxide) yields 8080 heat units. Wherever, in 
 chemical processes, strong chemical affinities are satisfied, heat is set free, i. e. , 
 ' chemical affnity is changed into heat. Chemical affinity is a form of potential 
 energy obtaining between the most different atoms, which during chemical pro- 
 cesses is changed into heat. Conversely, in those chemical processes where strong 
 affinities are dissolved, and chemically-united atoms thereby pulled asunder, there 
 must be a diminution of temperature, or, as it is said, heat becomes latent — that is, 
 the energy of the heat which has become latent is changed into chemical energy, 
 and this, after decomposition of the compound chemical body, is again represented 
 by the chemical affinity between its isolated different atoms. 
 
 LAW OF THE CONSERVATION OF ENERGY. 
 
 Julius Robert Mayer and Helmholtz have established the important law that, in 
 a system which does not receive any influence and impression from without, the 
 sum of all the forces acting within it is always the same. The various forms of 
 energy can be transformed one into the other, so that kinetic energy may be trans- 
 formed into potential energy, and vice versd, but there is never any part of the energy 
 lost. The transformation takes place in such measure that, from a certain definite 
 amount of one form of energy, a definite amount of another can be obtained. 
 
 The various forms of energy acting in organisms occur in the following 
 modifications : — 
 f 1. Molar motion (ordinary movements), as in the movements of the whole 
 / body, of the limbs, or of the intestines, and even those observable microscopically 
 I in connection with cells. 
 
 2. Movements of Atoms as Heat. — We know, in connection with the 
 vibration of atoms, that the number of vibrations in the unit of time determines 
 whether the oscillations appear as heat, light, or chemically-active vibrations. 
 
 / Heat vibrations have the smallest number, while chemically-active vibrations have 
 / the largest number, light vibrations standing between the two. In the human 
 body we only observe heat vibrations, but some of the lower animals are capable 
 of exhibiting the phenomena of light. 
 
 In the human organism, the molar movements -in the individual organs are 
 
 1 constantly being transformed into heat, e. g., the kinetic energy in the organs of 
 
 the circulation is transformed by friction into heat. The measure of this is the 
 
 "unit of work " = 1 gramme-metre, and the "unit of heat " = 425.5 
 
 gramme-metres. 
 
 3. Potential Energy. — The organism contains many chemical compounds 
 which are characterized by the great complexity of their constitution, by the 
 imperfect saturation of their affinities, and hence by their great tendency to split 
 up into simpler bodies. 
 
 The body can transform the potential energy into heat as well as into kinetic 
 
 I energy, the latter always in conjunction with the former, but the former always by 
 
 itself alone. The simplest measure of the potential energy is the amount of heat, 
 
INTRODUCTION. 
 
 XXXVII 
 
 which can be obtained by complete combustion of the chemical compounds 
 representing the potential energy. The number of work units can then be calcu- 
 lated from the amount of heat produced. 
 
 4. The phenomena of electricity, magnetism and diamagnetism may be / 
 recognized in two directions, as movements of the smallest particles, which are /*'- 
 recognized in the glowing of a thin wire when it is traversed by strong electrical) 
 currents (against considerable resistance), and also as molar movement, as in the 
 attraction or repulsion of the magnetic needle. Electrical phenomena are mani-j I 
 fested in our bodies by muscle, nerve) and glands, but these phenomena are rela4 J 
 tively small in amount when compared with the other forms of energy. It is not 
 improbable that the electrical phenomena of our bodies become almost completely 
 transformed into •heat. As yet experiment has not determined with accuracy a 
 " unit of electricity " directly comparable with the "heat unit " and the " work 
 unit." 
 
 It is quite certain that within the organism one form of energy can be trans- 
 formed into another form, and that a certain amount of one form will yield a 
 definite amount of another form ; further, that new energy never arises sponta- 
 neously, nor, is energy already present ever destroyed, so that in the organism the 
 law of the conservation of energy is continually in action. 
 
 ANIMALS AND PLANTS. 
 
 The animal body contains a quantity of chemically-potential energy stored up 
 in its constituents. The total amount of the energy present in the human body 
 might be measured by burning completely an entire human body in a calorimeter, 
 and thereby determining how many heat units are produced when it is reduced to 
 ashes (see Animal Heat). 
 
 The chemical compounds containing the potential energy are characterized by 
 the complicated relative position of their atoms, by a comparatively imperfect 
 saturation of the affinities of their atoms, by the relatively small amount of oxy- 
 gen which they contain, by their great tendency to decomposition, and the facility 
 with which they undergo decomposition. 
 
 If a man were not supplied with food he would lose 50 grammes of his body 
 weight every hour ; the material part of his body, which contains the potential 
 energy, is used up, oxygen is absorbed, and a continual process of combustion 
 takes place ; by the process of combustion simpler substances are formed from the 
 more complex compounds, whereby potential is converted into kinetic energy. 
 It is immaterial whether the combustion is rapid or slow ; the same amount of 
 the same chemical substances always produces the same amount of kinetic energy, 
 i. <?., of heat. 
 
 A person, when fasting, experiences after a certain time the disagreeable feeling 
 of exhaustion of his reserve of potential energy, hunger sets in, and he takes 
 food. All food for the animal kingdom is obtained, either directly or indirectly, 
 from the vegetable kingdom. Even carnivora, which eat the flesh of other animals, 
 only eat organized matter which has been formed from vegetable food. The 
 existence of the animal kingdom presupposes the existence of the vegetable king 
 dom. 
 
 All substances, therefore, necessary for the food of animals occur in vegetables.! 
 Besides water and the inorganic constituents, plants contain, among other! 
 organic compounds, the following three chief representatives of food stuffs — fats,| 
 carbohydrates and proteids. 
 
 All these contain stores of potential energy, in virtue of their complex chemical 
 constitution. 
 
 Co "•- 
 
 IK; 
 
 The fats contain — I C»H 2n _ 1 0(OH) = fatty acids 
 1 ne tats contain . j + C s H 5 (OH) s = glycerine 
 
 }(§2S0- 
 
XXXV111 INTRODUCTION. 
 
 The carbohydrates contain : — C 6 H J0 O.-, . . (§252). 
 
 (C. 51.5-54-5' 
 
 The proteids contain per cent. 
 
 (§§ 248 and 249). 
 
 H. 6.9- 7.3 
 
 N. 15. 2-17.0 
 
 O. 20.9-23.5 
 
 S. 0.3- 2.0 
 
 / A man who takes a certain amount of this food adds thereto oxygen from the 
 (air in the process of respiration. Combustion or oxidation then takes place, 
 whereby chemically potential energy is transformed into heat. 
 , It is evident that the products of this combustion must be bodies of simpler 
 'constitution — bodies with less complex arrangement of their atoms, with the 
 1 greatest possible saturation of the affinities of their atoms, of greater stability, 
 'partly rich in O, and possessing either no potential energy, or only very little. 
 These bodies are carbon dioxide, C0 2 ; water, H 2 ; and as the chief repre- 
 sentative of the nitrogenous excreta, urea (CO(NH 2 ) 2 ), which has still a small 
 amount of potential energy, but which outside the body readily splits into C0 2 
 and ammonia (NH 3 ). 
 
 The human body is an organism in which, by the phenomena of oxidation, the 
 complex nutritive materials of the vegetable kingdom, which are highly charged 
 with potential energy, are transformed into simple chemical bodies, whereby the 
 potential energy is transformed into the equivalent amount of kinetic energy (heat, 
 work, electrical phenomena). 
 
 - -But how do plants form these complex food stuffs so rich in potential energy ? 
 It is plain that the potential energy of plants must be obtained from some other 
 form of energy. This potential energy is supplied to plants by the rays of the 
 sun, whose chemical light rays are absorbed by plants. Without the rays of the 
 sun there could be no plants. Plants absorb from the air and the soil C0 2 , H 2 0, 
 NHj, and N, of which carbon dioxide, water, and ammonia (from urea) are also 
 produced by the excreta of animals. Plants absorb the kinetic energy of light from 
 the sun's rays and transform it into potential energy , which is accumulated during 
 the growth of the plant in its tissues, and in the food stuffs produced in them 
 during their growth. This formation of complex chemical compounds is accom- 
 panied by the simultaneous excretion of O. 
 
 Occasionally, kinetic energy, such as we universally meet with in animals, is liberated in plants. 
 Many plants develop considerable quantities of heat in their flowers, e.g., the arum tribe. We 
 must also remember that during the formation of the solid parts of plants, when fluid juices are 
 changed into solid masses, heat is set free. In plants, under certain circumstances, O is absorbed, 
 and C0 2 is excreted, but these processes are so trivial as compared with the typical condition in the 
 vegetable kingdom, that they may be regarded as of small moment. 
 
 Plants, therefore, are organisms which, by a reduction process, transform 
 simple stable combinations into complex compounds, whereby potential solar 
 energy is transformed into the chemically-potential energy of vegetable tissues. 
 Animals are living beings, which by oxidation decompose or break up the com- 
 plex grouping of atoms manufactured by plants, whereby potential is transformed 
 into kinetic energy. Thus there is a constant circulation of matter and a con- 
 stant exchange of energy between plants and animals. All the energy of animals 
 is derived from plants. All the energy of plants arises from the sun. Thus the 
 sun is the cause, the original source of all energy in the organism, i. <?., of the whole 
 of life. 
 
 As the formation of solar heat and solar light is explicable by the gravitation 
 of masses, gravity is, perhaps, the original form of energy of all life. 
 
 We may thus represent the formation of kinetic energy in the animal body from 
 the potential energy of plants. Let us suppose the atoms of the substances 
 formed in organisms, as simple small bodies, balls, or blocks. As long as these 
 
INTRODUCTION. XXXIX 
 
 lie in a single layer, or in a few layers, upon the surface, there is a stable arrange- 
 ment, and they continue to remain at rest. If, however, an artificial tower be 
 built of these blocks, so that an unstable erection is produced, and the same tower 
 be afterwards knocked down, then for this purpose we require — (i) the motor 
 power of the workman who lifts and carries the blocks; (2) a blow or other 
 impulse from without applied to the unstable structure — when the atoms will fall 
 together, and as they fall collide with each other and produce heat. Thus the 
 energy employed by the workman is again transformed into the last-named form 
 of energy. 
 
 In plants, the complex unstable building of the groups of atoms is carried on, f 
 the constructor being the sun. In animals, which eat plants, the complex groups / 
 of the atoms are tumbled down, with the liberation of kinetic energy. 
 
 VITAL ENERGY AND LIFE. 
 
 The forces which act in organisms, in plants, and animals are exactly the same 
 as are recognizable as acting in dead matter. A so-called "vital force," as a 
 special force of a peculiar kind, causing and governing the vital phenomena of 
 living beings, does not exist. The forces of all matter, of organized as well as 
 unorganized, exist in connection with their smallest particles or atoms. As, how- 
 ever, the smallest particles of organized matter are, for the most part, arranged in 
 a very complicated way, compared with the much simpler composition of inor- 
 ganic bodies, so the forces of the organism connected with the smallest particles 
 yield more complicated phenomena and combinations, whereby it is excessively 
 difficult to ascribe the vital phenomena in organisms to the simple fundamental 
 laws of physics and chemistry. 
 
 The Exchange of Material, or Metabolism ( " Stoffwechsel" ) as a Sign 
 of Life. — Nevertheless, there appears to be a special exchange of matter and I 
 energy peculiar to living beings. This consists in the capacity of organisms to as- / 
 similate the matter of their surroundings, and to work it up into their own consti- ! 
 tution, so that it forms for a time an integral part of the living being, to be given . 
 off again. The whole series of phenomena is called Metabolism or Stoffwech- 
 sel, which consists in the introduction, assimilation, integration, and excretion of/ 
 matter. 
 
 We have already shown that the metabolism of plants and that of animals are , 
 quite different. The processes, as already described, actually occur in the typical I 
 higher plants and animals. 
 
 But there is a large group of organisms which, throughout their entire organiza- 
 tion, exhibit so low a degree of development, that by some observers they are 
 considered as undifferentiated " ground forms." They are regarded as neither 
 plants nor animals, and are the most simple forms of animated matter. Hseckel 
 has called these organisms Protista?, as being the original and primitive forms. 
 
 We must assume that, corresponding with their simpler vital conditions, their ' 
 metabolism is also simpler, but on this point we still require further observations. 
 
ERRATA. 
 
 Page 42, sixth line from bottom, " Fig. 11.5" should be " Fig. 14.5." 
 Page 45, sixteenth line from top, read haemoglobin. 
 Page 79, Fig. 32, the letters D E are omitted. 
 
 Page 84, twentieth line from top, " Fig. 31, E " should be " Fig. 32, E." 
 Page 101, Fig. 55, the section marked b is reversed. 
 
 Page 133, Section 75, the references to Fig. 90 are incorrect, because a portion of the cut has been 
 omitted. 
 
 Page 138, second line from bottom, " Fig. 96 " should be " Fig. 95." 
 
 Page 734, fourth line from top, " cordate " should be ' : caudate." 
 
 Page 757, eleventh line from bottom, "meredional" should be "meridional." 
 
 /f 
 
PHYSIOLOGY OF THE BLOOD. 
 
 [The blood is aptly described by Claude Bernard as an internal medium which 
 acts as a " go-between " or medium of exchange for the outer world and the 
 tissues. Into it are poured those substances which have been subjected to the 
 action of the digestive fluids, and in the lungs or other respiratory organs it 
 receives oxygen. It thus contains new substances, but in its passage through the 
 tissues it gives up some of these new substances, and receives in exchange certain 
 effete or 'waste products and more or less useless substances which have to be 
 got rid of. Its composition is thus highly complex, containing, as it does, things 
 both new and old. Besides carrying the new nutrient fluids to the tissues, it is 
 also the great oxygen carrier, as well as the medium by which part of the waste 
 pre ducts, e.g., C0 2 , urea, are removed from the tissues and brought to the organs, 
 e. g., the lungs, kidneys, skin, which eliminate them from the body. It is at once 
 a great pabulum-supplying medium and a channel for getting rid of useless mate- 
 rials. As the composition of the organs through which the blood flows varies, it 
 is evident that its composition must vary in different parts of the circulatory 
 system ; and it also varies in the same individual under different conditions. 
 Still, with slight variations, there are certain general physical, histological and 
 chemical properties which characterize blood as a whole.'] 
 
 i. PHYSICAL PROPERTIES OF THE BLOOD.— (i) Color.— 
 
 The color of blood varies from a bright scarlet red in the arteries to a deep, dark, 
 bluish-red in the veins. Oxygen (and, therefore, the air) makes the blood bright 
 red ; want of oxygen makes it dark. Blood free from oxygen (and also venous 
 blood) is dichroic — i. e., by reflected light it appears dark red, while by transmitted 
 light it is green (Briicke). [Arterial blood is monochroic] 
 
 In thin layers blood is opaque, as is easily shown by shaking blood so as to 
 form bubbles, or by allowing blood to fall upon a plate with a pattern on it, and 
 pouring it off again. Blood behaves, therefore, like an "opaque color" (Rolletf), 
 as its coloring matter is suspended in the form of fine particles — the blood cor- 
 puscles. 
 
 Hence, it is possible to separate the coloring matter from the fluid part of the blood by filtration. 
 This is accomplished by mixing the blood with fluids which render the blood corpuscles sticky or 
 rough. If mammalian blood be treated with one-seventh of its volume of solution of sodic sulphate 
 (Figuier), or if frogs' blood be mixed with a * per cent, solution of sugar (Joh. Miiller) and 
 filtered, the shriveled corpuscles, now robbed of part of their water, remain upon the filter. 
 
 (2) Reaction. — The reaction is alkaline, owing to the presence of disodic 
 phosphate, Na 2 ,H,P0 4 (Maty) [and bicarbonate of soda]. After blood is shed, 
 its alkalinity rapidly diminishes, and this occurs more rapidly the greater the 
 alkalinity of the blood. This is due to the formation of an acid, in which, perhaps, 
 the colored corpuscles take part, owing to the decomposition of their coloring 
 matter. A high temperature and the addition of an alkali favor the formation of 
 the acid (N. Zuntz). 
 
 The alkaline reaction of blood is diminished : (a) by great muscular exertion, owing to the 
 formation of a large amount of acid in the muscles ; (£) during coagulation ; (c) in old blood, or 
 blood dissolved by water from old blood stains, such blood being usually acid ; fresh cruor has a 
 stronger alkaline reaction than serum ; [d ) after the prolonged use of soda the alkalinity is in- 
 creased [Dubelir), after the use of acids it is decreased. 
 2 17 
 
18 MICROSCOPIC EXAMINATION OF THE BLOOD. 
 
 Pathological. — The alkalinity is less in persons suffering from anaemia, cachectic conditions, 
 and chronic rheumatism (Lfyine), and also in cholera. [Immediately before death by cholera it 
 may be acid (Cantani).] 
 
 Methods. — Owing to the color of the blood we cannot employ ordinary litmus paper to test its 
 reaction. One or other of the following methods may be used : (i) Moisten a strip of glazed red 
 litmus paper with solution of common salt, and dip it quickly into the bltod, or allow a drop of 
 blood to fall on the paper, and rapidly wipe it off before its coloring matter has time to penetrate 
 and tinge the paper (Zuntz). (2) Kuhne made a small cup of parchment paper, which was placed 
 in water in a watch glass. The colorless tliffusate was afterward tested with litmus paper. (3) 
 Liebreich used thin plates of plaster-of- Paris of a perfectly neutral reaction. These are dried, and 
 afterward moistened with a neutral solution of litmus. When a drop of blood is placed upon the 
 porous plate, the fluid part of the blood passes into it, while the corpuscles remain at the surface. 
 The corpuscles are washed off with water, and the altered color of the litmus-stained slab is ap- 
 parent. [(4) Schafer uses dry, faintly-reddened, glazed litmus paper, and on it is placed a drop of 
 blood, which is wiped off after a few seconds. The place where the blood rested is indicated by a 
 well-defined blue patch upon a red or violet ground.] 
 
 (3) Odor. — Blood emits a peculiar odor {Hatttus sanguinis), which differs in 
 animals and man. 
 
 It depends upon the presence of volatile fatty acids (Matleucci). If concentrated sulphuric acid 
 be added to blood, whereby the volatile fatty acids are set free from their combinations with alka- 
 lies, the characteristic odor becomes much more perceptible (Barruel). [The odor is somewhat 
 similar to that of butyric acid.] 
 
 (4) Taste. — Blood has a saline taste, depending upon the salts dissolved in the 
 fluid of the blood. 
 
 (5) Specific Gravity. — The specific gravity is 1055 (extreme limits 1045- 
 1075) ; in women and young persons it is somewhat less. The specific gravity of 
 the blood corpuscles is 1105, that of the plasma 1027. Hence, the corpuscles 
 tend to sink. 
 
 The specific gravity of the red blood corpuscles is estimated by allowing the corpuscles to subside 
 to the bottom (which occurs most readily in the blood of the horse) ; but it is more correctly esti- 
 mated by placing the blood in a tall cylindrical vessel, and setting the latter in the radius of the 
 revolving disk of a centrifugal apparatus, the base of the cylinder being directed outward. The 
 drinking of water and hunger diminish the specific gravity temporarily, while thirst and the digestion 
 of dry food raise it. If blood be passed through an organ artificially, its specific gravity rises in 
 consequence of the absorption of dissolved matters and the giving off of water. It falls after hem- 
 orrhage, and is less in badly-nourished individuals. 
 
 (6) [Temperature. — Blood is viscid, and its temperature varies from 36.5° C. 
 (97.7° F.) to 37. 8° C. (ioo° F.). The warmest blood in the body is that of the 
 hepatic vein, while that of the right ventricle is warmer than that of the left side 
 of the heart, § 2 10. J 
 
 2. MICROSCOPIC EXAMINATION OF THE BLOOD.— [Blood, 
 
 when examined by the microscope, is seen to consist of an enormous number of 
 corpuscles — colored and colorless — floating in a transparent fluid, the plasma, 
 or liquor sanguinis.^ 
 
 f The red blood corpuscles were discovered in frogs' blood by Swammerdam in 
 
 I 1658, and in human blood by Leeuwenhoek in 1673. 
 
 ' Characters of Human Blood — (a) Form. — The human red blood cor- 
 puscles are circular, coin-shaped, homogeneous disks, with saucer-like depressions 
 on both surfaces, and with rounded margins ; in other words, they are bi-concave, 
 circular, non-nucleated disks. 
 
 (&) Size. — According to Welcker the diameter (ab) is 7.7 //,* the greatest 
 thickness (c d) 1.9 fi (Fig. 1, C) [z. e., it is -^^ to -^^ of an inch in diameter, 
 and about one-fourth of that in thickness]. 
 
 The corpuscles are slightly diminished in size by septic fever, inanition, after the subcutaneous 
 I injection of morphia, increased bodily temperature, and C0 2 ; while they are increased 'by O, wa- 
 [ tery condition of the blood, cold, consumption of alcohol, quinine, hydrocyanic acid and acute 
 anaemia (Manasseln). Compare \ 113. 
 
 * The Greek letter [X represents one-thousandth of a millimetre (/£ = 0.001 mm.), and is the sign of a micro-milli- 
 metre, or a micron. 
 
MICROSCOPIC EXAMINATION OF THE* BLOOD. 
 
 19 
 
 If the total amount of blood in a man he taken at 4400 cubic centimetres, the corpuscles therein \ , 
 contained have a surface of 2816 square metres, which is equal to a square surface with a side of 80 )/ 
 paces; 176 cubic centimetres of blood pass through the lungs in a second, and the blood corpuscles / 
 in this amount of blood have a superficies of 81 square metres, equal to a square surface with a side/ 
 of 13 paces ( Welder). 
 
 (c) Weight. — The weight of a blood corpuscle, according to Welcker, is I 
 0.00008 milligrammes. ' 
 
 (aQ Number. — According to Vierordt, the number exceeds 5,000,000 per 
 cubic millimetre in the male, and 4,500,000 in the female ; so that in 10 lbs. of 
 blood there are 25 billions of corpuscles. As a general rule, the number is in 
 inverse ratio to the amount of plasma ; hence, the number must vary with the 
 state of contraction of the blood vessels, the pressure-diffusion currents and other 
 conditions. 
 
 The number of red corpuscles is increased ; in venous blood (especially in the small cutaneous 
 veins), after the use of solid food. After much sweating, and the excretion of water by the bowel 
 and kidney; during inanition, because the blood plasma undergoes decomposition sooner than the 
 blood corpuscles themselves (Buntzen) ; in the blood of the newly-born child (Panum and So- 
 rensen), especially when the umbilical cord is long in being tied ($40); [from the fourth day onward 
 the number is diminished (Hayem)'], in persons of robust constitution, and in those who live in the 
 
 Fig. 1. 
 
 A, Human colored blood corpuscles — r, seen on the flat ; 2, on edge ; 3, rouleau of colored corpuscles slightly sepa- 
 rated. B, colored amphibian blood corpuscles — 1, seen on the flat, and 2, on edge. C, ideal transverse section 
 of a human colored blood corpuscle magnified 5000 times linear — a l>, diameter ; c d, thickness. 
 
 country. The number is diminished, during pregnancy, after copious draughts of water. In the 
 earlier period of foetal life the number is only \-\ million in 1 c. c. {Cohnheim, Zuntz). 
 (The pathological conditions which affect the number of corpuscles are given at \ 10. ) 
 Methods of Estimating the Number of Blood Corpuscles. — The pointed end of a glass 
 pipette (Fig, 3), the mixer, is dipped into the blood, and by sucking the elastic tube/, blood is 
 drawn into the tube until it reaches the mark \, on the stem of the pipette, or until the mark 1 is 
 reached. The caretully-cleaned point of the pipette is dipped into the artificial serum, and this is 
 sucked into the pipette until it reiches the mark, 101. The artificial serum consists.of I vol. of 
 solution of gum arabic (sp. gr. 1020) and 3 vols, of a solution of equal parts of sodic sulphate and 
 sodic chloride (sp. gr. 1020). The process of mixing the two fluids is aided by the presence of a 
 little glass ball («) in the bulb of the pipette. If blood is sucked up to the mark \, the strength of 
 the mixture is I : 200; if to the mark 1, it is 1 : 100. A small drop of the mixture is allowed to 
 run into the counting chamber of Abbe and Zeiss (Fig. 2) (the first portions are not used, in order to 
 obtain a uniform sample from the bulb of the pipette). This chamber consists of a gla«s receptacle 
 0.1 mm. deep, with its base divided into squares, and cemented to a microscopic slide, the whole 
 being covered with a microscopic covering glass. The space over each square = j^tf cu bic milli- 
 metre. Count, with the aid of a microscope, the number of blood corpuscles in each square, and 
 the number found, multiplied by 4000, will give the number of blood corpuscles in 1 c.mm. This 
 number, again, must be multiplied by 100 or 200, according as the blood was diluted 100 or 200 
 times. To ensure greater accuracy, it is well to count the number in several squares, and to take 
 the mean of these. [The method of Malassez was described in the last edition of this work.] 
 
20 
 
 MICROSCOPIC EXAMINATION OF THE BLOOD. 
 Fig. 2. 
 
 5TS T1 T? T^^^^^! ■-- ■— - 
 g ° ^^ " ° " " " " "T"" *.^ :°c» 
 
 3"*~ ~ — z — ST VTS" ~a — 5 ~ — "" ~~ ~ d ■ * - 
 o °° ■" * a 6 ° ° ° ° " o " ° I ° b • 
 
 r 
 
 Apparatus, of Abbe and Zeiss for counting the number of 
 corpuscles. A, in section ; C, surface view without 
 cover glass ; B, microscopic appearance with the 
 blood corpuscles. 
 
 Fig. 4. 
 
 The Melange ur t pipette or 
 mixer. 
 
 Gowers apparatus, made by Hawksley, London. A, pipette for measuring the diluting solution ; B, capillary tube 
 for measuring the blood; C, cell with divisions on the floor, mounted on a slide, to which springs are fixed to 
 secure the cover glass; D, vessel in which the solution is made; E, spud for mixing the blood and solution- 
 F, guarded spear-pointed needle. 
 
EFFECTS OF REAGENTS ON BLOOD CORPUSCLES. 21 
 
 [The following is a description of Gowers' instrument (Fig. 4): "The Haemacytometer 
 consists of — (1) a small pipette, which, when filled to the mark on its stem, holds exactly 995 
 cubic millimetres. It is furnished with an India-rubber tube and mouthpiece to facilitate filling 
 and emptying. (2) A capillary tube marked to contain exactly 5 cubic millimetres, with India- 
 rubber tube for rilling, etc. (3) A small glass jar in which the dilution is made. (4) A glass 
 stirrer for mixing the blood and solution in the glass jar. (5) A brass stage plate, carrying a glass 
 slip, on which is a cell, i of a millimetre deep. The bottom of this is divided into ^ millimetre 
 squares. Upon the top of the cell rests the cover glass, which is kept in its place by the pressure 
 of two springs proceeding from the ends of the stage plate." 
 
 The diluting solution used is a solution of sodic sulphate in distilled water, sp. gr. 1025, or the 
 following — sodic sulphate, 104 grains ; acetic acid, 1 drachm ; distilled water, 4 oz. 
 
 "995 cubic millimetres of the solution are placed in the mixing jar; 5 cubic millimetres of 
 blood are drawn into the capillary tube from a puncture in the finger, and then blown into the 
 solution. The two fluids are well mixed by rotating the stirrer between the thumb and finger, 
 and a small drop of this dilution is placed in the centre of the cell, the covering glass gently put 
 upon the cell, and secured by the two springs, and the plate placed upon the stage of the 
 microscope. The lens is then focused for the squares. In a few minutes the corpuscles have 
 sunk to the bottom of the cell, and are seen at rest on the squares. The number in ten squares is 
 then counted, and this, multiplied by 10,000, gives the number in a cubic millimetre of blood." 
 
 To estimate the colorless corpuscles only, mix the blood with 10 parts of 0.5 per cent, solution 
 of acetic acid, which destroys all the red corpuscles ( Thorna).] 
 
 (e) Red blood corpuscles are characterized by their great elasticity, flexi- 
 bility and softness. [The elastic property is shown by the great extent to 
 which red corpuscles still within the circulation may be distorted, and yet resume 
 their original form as soon as the pressure is removed.] 
 
 3. HISTOLOGY OF THE HUMAN RED BLOOD CORPUS- 
 CLES. — When observed singly, blood corpuscles have a yellow color with a 
 slight tinge of green ; they seem to be devoid of an envelope, are certainly non- 
 nucleated, and appear to be homogeneous throughout. Each corpuscle consists (1) 
 of a framework, an exceedingly pale, transparent, soft protoplasm — the stroma 
 [Rollett) ; and (2) of the red pigment, or haemoglobin, which impregnates the 
 stroma, much as fluid passes into and is retained in the interstices of a bath-sponge. 
 Some observers (Bottcher, Eberhardt, Strieker) maintain that the corpuscles contain 
 a nucleus, but this is certainly a mistake. 
 
 4. EFFECTS OF REAGENTS.— (A) On the Vital Phenomena. 
 
 Blood corpuscles contained in shed blood — or even in defibrinated blood, when it 
 is reintroduced into the circulation — retain their vitality and functions undimin- 
 ished. Heat acts powerfully on their vitality, for if blood be heated to 52 C, 
 the vitality of the red corpuscles is extinguished. Mammalian blood may be kept 
 for four or five days in a vessel under iced water, and still retain its functions; but 
 if it be kept longer, and reintroduced into the circulation, the corpuscles rapidly 
 break up — a proof that they have lost their vitality (Landois). Crenation. — 
 Blood freshly shed from an artery frequently shows a transformation of the corpus- 
 cles into a peculiar mulberry shape. [This is the so-called crenation of the colored 
 corpuscles. It is produced by poisoning with Calabar bean (T. R. Fraser), and 
 also by the addition of a 2 per cent, solution of common salt.] The blood of 
 many persons crenates spontaneously — a condition ascribed to an active contrac- 
 tion ot the stroma {Klebs), but it is doubtful if this is the cause. Max Schultze 
 observed that the red corpuscles of the embryo chick undergo active contraction. 
 
 (B) On the External Characters. — Many agents affect the external char- 
 acters of the corpuscles. 
 
 (a) The Color is changed by many gases. O makes blood scarlet, want of O 
 renders it dark bluish-red, CO makes it cherry-red, NO violet-red. There is no 
 difference between the shape of corpuscles in arterial and venous blood, as was 
 supposed by Harless. All reagents (e. g. , a concentrated solution of sodic sul- 
 phate) which cause great shrinking of the colored corpuscles produce a very 
 bright scarlet or brick-red color (Bartholinus, 1661). The red color so produced 
 is quite different from the scarlet-red of arterial blood. Reagents which render 
 
22 EFFECTS OF REAGENTS ON BLOOD CORPUSCLES. 
 
 blood corpuscles globular darken the blood, e.g., water. [The contrast is very 
 striking, if we compare blood to which a 10 per cent, solution of common salt 
 has been added with blood to which water has been added. With reflected light 
 the one is bright red, and the other a very dark, deep crimson, almost black.] 
 
 (fi) Change of Position and Form. — A very common phenomenon in 
 shed blood is the tendency of the corpuscles to run into rouleaux (Fig. i, A, 3). 
 
 Conditions that increase the coagulability of the blood favor this phenomenon, which is ascribed 
 by Dogiel to the attraction of the disks and the formation of a sticky substance. [The cause of the 
 arrangement of the red corpuscles into rouleaux is by no means clear. They may be detached 
 from each other by gently touching the cover glass, but the rouleaux may reform. Lister suggested 
 that the surfaces of the corpuscles were so altered that they became adhesive, and thus cohered. 
 Norris has made some ingenious, experiments with corks weighted with tacks or pins, so as to pro- 
 duce partial submersion of the cork disks. These disks rapidly cohere, owing to capillarity, and 
 form rouleaux. If the disks be completely submerged they remain apart, as occurs with unaltered 
 blood corpuscles within the blood vessels. If, however, the corpuscles be dipped in petroleum, and 
 then placed in water, rouleaux are formed.] If reagen's which cause the corpuscles to swell up be 
 added to the blood, the corpuscles become globular and the rouleaux break. According to E. 
 Weber and Suchard, the uniting medium is not fibrin (although it may sometimes assume a fibrous 
 form), but belongs to the peripheral layer of the corpuscles. 
 
 {c) The Changes of Form which, after blood is shed, the red corpuscles 
 undergo until they are gradually dissolved, are important. Some reageants rapidly 
 produce this series of events, eg., the discharge of a Leyden jar causes the 
 
 Red blood corpuscles, showing various changes of shape, a, b, normal human red corpuscles, with the central de- 
 pression more or less in focus ; c, d, e, mulberry forms ; g, h , crenated corpuscles ; k, pale decolorized corpuscles ; 
 /, stroma ; f, a frog's blood corpuscle, partly shriveled, owing to the action of a strong saline solution. 
 
 corpuscles to crenate, so that their surfaces are beset with large or small projec- 
 tions (Fig. 5, c, d, e, g, K) ; it also causes the corpuscles to assume a spherical form 
 (J, i), when they are smaller than normal. The corpuscles so altered are sticky, 
 and run together like drops of oil, forming larger spheres. The prolonged action 
 of the electrical spark causes the haemoglobin to separate from the stroma ik), 
 whereby the fluid part of the blood is reddened, while the stroma is recognizable 
 only as a faint shadow (1). Similar forms are to be found in decomposing blood, 
 as well as after the action of many other reagents. 
 
 Action of Heat. — When blood is heated, on a warm stage, to 5 2° C. the 
 corpuscles begin to undergo remarkable changes. Some of them become spherical, 
 others biscuit-shaped ; some are perforated, while in others small portions become 
 detached and swim about in the surrounding fluid, a proof that heat destroys the 
 histological individuality of the corpuscles {Max Schultze). If the heat be con- 
 tinued, the corpuscles are ultimately dissolved (§ 10, 3). 
 
 Heat acts like the addition of a concentrated solution of urea to blood. If strong pressure be 
 exerted upon a microscopic preparation, the blood corpuscles are compressed, and may break in 
 pieces. This latter process of breaking up the corpuscles is called haemocytotrypsis, in distinc- 
 tion to that of solution of the corpuscles or haemocytolysis. 
 
 Cytozoon or Wurmchen — Gaule's Experiment. — The following remarkable observation 
 made by Gaule deserves mention here : A few drops of freshly-shed frog's blood are mixed with 
 
LAKE-COLORED BLOOD. 23 
 
 5 c.c. of 0.6 per cent, solution of common salt, and the mixture defibrinated by shaking it along 
 with a few c.c. of mercury. A drop of the defibrinated blood is examined on a hot stage (30-32 
 C.) under a microscope, when a protoplasmic mass, the so-called " wiirmchen" escapes, with a 
 lively movement, from many corpuscles, and ultimately dissolves. Similar "cytozoa" were dis- 
 covered by Gaule in the epithelium of the cornea, of the stomach and intestine, in connective tissue, 
 in most of the large glands, and in the retina (frog, triton). In mammals also he found similar but 
 smaller structures. Most probably these structures are parasitic in their nature, as suggested by 
 Ray Lankester, who called the parasite Drepanidium ranarum. 
 
 If a finger moistened with blood be rapidly drawn across a warm slip of glass, 
 so that the fluid dries rapidly, very remarkable corpuscle shapes, showing their 
 great ductility and softness, are observed under the microscope. 
 
 (For the effects of chemical reagents see p. 24.) 
 
 [Staining Reagents. — Such reagents as magenta, picrocarmine, carmine, 
 and many of the aniline dyes, stain the nucleus deep red when such is present, and 
 although they must traverse the haemoglobin to reach the nucleus, the haemoglobin 
 itself is not stained. When no nucleus is present, therefore, the corpuscles are 
 not stained. Magenta (as pointed out by Roberts) causes one or more small spots 
 or maculae to appear on the edge of the corpuscles. What its significance is, is 
 entirely unknown. Normal saline solution ^6 per cent. NaCl), tinged with methyl- 
 violet, is a good staining and preservative agent {Bizzozero)^\ 
 
 [Effect of Agitation with Mercury. — Meltzer and Welch find that if ox blood be shaken up 
 with mercury for 7 or 8 hours, the agitation causes the corpuscles completely to disappear, no trace 
 of stroma or particles of the corpuscles being found in the tiuid. On the other hand, the addition of 
 pyrogallic acid (20 per cent.), potassic chlorate (6 per cent.), and silver nitrate (3 per cent.), completely 
 prevents this dissolution of the corpuscles, even though the shaking be kept up for fourteen days.] 
 
 If blood be mixed with concentrated gum, and if concentrated salt solution be added to it under 
 the microscope, the corpuscles assume elongated forms (Lindwurm). Similar forms are obtained 
 by mixing blood with an equal volume of gelatine at 36° C, allowing it to cool, and then making 
 sections of the coagulated mass {/iollett). The corpuscles may be broken up by pressing firmly on 
 the cover glass. In all these experiments no trace of an envelope is observed. 
 
 Conservation of the Red Blood Corpuscles. — The blood corpuscles retain their characters 
 in the following fluids : — 
 
 Hayem's Fluid. 
 
 Hydrarg. bichlor., 0.5 
 
 Sodic sulphate 5.0 
 
 Sodic chloride, 1.0 
 
 Distilled water, 200.0 
 
 Pacini's Mixture. 
 
 Hydrarg. bichlor., 2 
 
 Sodic chloride 4 
 
 Glycerine, 26 
 
 Distilled Water 226 
 
 To be diluted with 2 parts of distilled water 
 before being used. 
 
 [An excellent reagent for " fixing " the blood corpuscles is either a dilute solution or the vapor 
 of osmic acid.] 
 
 In investigating blood with the microscope for forensic purposes, it is necessary to have a 
 solvent for the blood when it occurs as stains on a garment or instrument. Dried stains are dis- 
 solved by a concentrated ( Virchow), or a 30 per cent. {Malinin) solution of caustic potash, or with 
 one of the preserving fluids, care being taken to avoid friction. If the stain be softened with con- 
 centrated tartaric acid, the colorless corpuscles are specially distinct {Struwe). Nevertheless, cor- 
 puscles are often not found in such stains. If the corpuscles have become very pale, their color 
 may be improved by adding a solution of iodine in iodide of potassium, a saturated solution of 
 picric acid, 20 per cent, pyrogallic acid, or 3 per cent, solution of silver nitrate (Meltzer and Welch). 
 
 5. PREPARATION OF THE STROMA— MAKING BLOOD 
 " LAKE-COLORED." — There are many reagents which separate the haemo- 
 globin from the stroma. The haemoglobin dissolves in the serum ; the blood then 
 becomes transparent, as it contains its coloring matter in solution, and hence is 
 called "Lake-colored" by Rollett. Lake-colored blood is dark red. The 
 aggregate condition of the haemoglobin is not altered when the corpuscles are 
 dissolved ; it only changes its place, leaving the stroma and passing into the 
 serum. Hence, the temperature of the blood is not lowered thereby {Landois). 
 
 Methods. — To obtain a large quantity of the stroma for chemical purposes, add 10 vols, of a 
 solution of common salt (1 vol. concentrated solution, and 15 to 20 vols, of water) to 1 vol. of 
 defibrinated blood, when the stromata are thrown down as a whitish precipitate. 
 
24 FORM AND SIZE OF BLOOD CORPUSCLES. 
 
 For microscopical purposes, mix blood with an equal volume of a concentrated solntion of ssdic 
 sulphate, and cautiously add a I per cent, solution of tartaric acid (Landois). 
 
 The following reagents cause a separation of the stroma from the haemoglobin : — 
 
 (a) Physical Agents. — I. Heating the blood to 60° C. (Schultze); the temperature, however, 
 varies for the blood of different animals. 2. Repeated freezing and thawing of the blood 
 (Rollett). 3. Sparks from an electrical machine (but not after the addition of salts to the blood) 
 (Rollett) ; the constant and induced currents [Neumann). 
 
 (b) Chemically active Substances produced within the Body. — 4. Bile (Hiinefeld), or bile 
 salts (Plaltner, v. Dusch). 5. Serum of other species of animals (Landois) ; thus dog's serum 
 and frog's serum dissolve the blood corpuscles of the rabbit in a few minutes. 6. The addition 
 of lake-colored blood of many species of animals (Landois). 
 
 (c) Other Chemical Reagents. — 7. Water. 8. Conduction of vapor of chloroform (Bottcker) ; 
 ether (v. Wittich) ; amyls, small quantities of alcohol (Rollett) ; thymol (Marchand) ; nitrobenzol, 
 ethylic ether, aceton, petroleum ether, etc. (L. Lewin). 9. Antimoniuretted hydrogen, arseniu- 
 retted hydrogen; carbon uisulphide (Hiinefeld, Hermann); boracic acid (2 per cent.), added to 
 amphibian blood, causes the red mass (which also encloses the nucleus when such is present), 
 the so-called zooid, to separate from the acoid. The zooid may shrink from the periphery of the 
 corpuscle, or it may even pass out of the corpuscle altogether (Brucke); Briicke regards the 
 stroma in a certain sense as a house, in which the remainder of the substance of the corpuscle, 
 the chief part endowed with vital phenomena, lives. 1 1 . Strong solutions of acids dissolve the 
 corpuscles ; more dilute solutions cause precipitates in the haemoglobin. This is easily seen with 
 carbolic acid (Hiils and Landois ; Stirling and Rannie). 12. Alkalies of moderate strength 
 cause sudden solution. A 10 per cent, solution of potash, placed at the margin of a cover glass, 
 shows the process of solution going on under the microscope. At first the corpuscles become 
 globular, and so appear smaller, but afterward they burst like soap bubbles. [NH 4 C1 injected 
 into the blood causes vacuolation of the red corpuscles (Bobritzky).~\ 
 
 [Tannic Acid. — A freshly-prepared solution of tannic acid has a remarkable effect on the colored 
 blood corpuscles of man and animals — causing a separation of the haemoglobin and the stroma. 
 The usual effect is to produce one or more granular buds of haemoglobin on the side of the cor- 
 puscles; more rarely the haemoglobin collects around the nucleus, if such be present ( W. 
 Roberts)] 
 [Ammonium or Potassium Sulphocyanide removes the haemoglobin, and reveals a reticular 
 structure — intranuclear plexus of fibrils (Stirling and Rannie). .] 
 
 The quantity of gases contained in the blood corpuscles exercises an important influence on their 
 solubility. The corpuscles of venous blood, which contains much C0 2 , are more easily dissolved 
 than those of arterial blood; while between both stands blood containing CO (Landois, Li/tersii, 
 Ltpine). When the gases are completely removed from the blood, it becomes lake-colored. 
 
 Salts increase the resistance of the corpuscles to physical means of solution, 
 while they facilitate the action of chemical solvents (Bernstein and Becker). 
 
 Resistance to Solvents. — The red blood corpuscles offer a certain degree 
 of resistance to the action of solvents. 
 
 Method. — Mix a small drop of blood with an equal volume of a 3 per cent, solution of sodic 
 chloride, and then add distilled water until all the colored corpuscles are dissolved. Fill the mixer 
 (Fig. 3) up to the mark 1 with blood obtained by pricking the finger, and blow this blood into an 
 equal volume of a 3 per cent, solution of NaCl previously placed in a hollow in a microscopic glass 
 slide. Mix the fluids, and the corpuscles will remain undissolved. By means of the pipette add 
 distilled water, and go on doing so until all the corpuscles are dissjlved; which is ascertained 
 with the microscope. In normal blood, solution of the corpuscles occurs after 30 volumes of dis- 
 tilled water have been added to the blood (Landois). 
 
 There are some individuals whose blood is more soluble than that of others ; their corpuscles are 
 soft, and readily undergo changes. Many conditions again, such as cholaemia, poisoning with sub- 
 stances which dissjlve the corpuscles, and a markedly venous condition of the blood, affect the 
 corpuscles. Interesting observations are to be made on the blood in infectious diseases, hemoglo- 
 binuria, and in cases of burning. In anaemia and fever, the capacity for resistance seems to be 
 diminished (Peiper). [Sodic salicylate, benzoate and colchicin dissolve the red corpuscles (N. 
 Paton).] 
 
 6. FORM AND SIZE OF THE BLOOD CORPUSCLES OF 
 DIFFERENT ANIMALS.— All mammals (with the exception of the camel, 
 llama, alpaca, and their allies), and the cyclostomata among fishes, e.g. , Petromy- 
 zon, possess circular, bi-concave, non-nucleated, disk-shaped corpuscles. 
 
 Elliptical corpuscles without a nucleus are found in the above-named mammals, 
 while all birds, reptiles, amphibians (Fig. 1, B, 1, 2), and fishes (except cyclosto- 
 mata) have nucleated, elliptical, bi-convex corpuscles. 
 
ORIGIN OF THE RED BLOOD CORPUSCLES. 
 
 25 
 
 v v 
 
 Size (/* = o.ooi Millimetre). 
 
 Of the Disk-shaped 
 Corpuscles. 
 
 S 
 
 Elephant 9 4 !>■ 
 
 Man, 77 " 
 
 Dog 7-3 " 
 
 Rabbit 6.9 " 
 
 at, 6.5 " 
 
 ^-Sheep 5-0 " 
 
 Goat 4.1 " 
 
 /'Musk deer, ... 2.5 " 
 
 Of the Elliptical Corpuscles. 
 
 Short Diameter. 
 
 Llama, 4.0 ft 
 
 Dove, .... 6.5 " 
 
 Frog 15.7 " 
 
 Triton, . . . 19.5 '' 
 
 Proteus, . . . 35 o " 
 
 Long Diameter. 
 
 8.0 11. 
 14.7 " 
 22.3 " 
 293 " 
 58.0 " 
 
 The corpuscles of Amphiuma are nearly one third larger 
 than those of Proteus {Riddel). 
 
 Among vertebrates, amphioxus has colorless blood. The large blood corpuscles of many | 
 amphibia, e.g., amphiuma, are visible to the naked eye. The blood corpuscles of the frog contain, 
 in addition to a nucleus, a nucleolus (Auerbach, Ranvier), [and the same is true of the colored cor- 
 puscles of the newt [Stirling). The nucleolus is revealed by acting on the corpuscles with dilute 
 alcohol (1, alcohol; 2, water; Ranvier's " alcool au tiers").'] It is evident that the larger the 
 blood corpuscles are, the smaller must be the number and total superficies of corpuscles in a given 
 volume of blood. In birds, however, the number is relatively larger than in other classes of verte- 
 brates, notwithstanding the larger size of their corpuscles ; this, doubtless, has a relation to the very 
 energetic metabolism that takes place in birds {Malassez). Among mammals, carnivora havef 
 more blood corpuscles than heTbivora. Welcker has ascertained that goat's blood contains 9,720,000 
 corpuscles per cubic millimetre; the llama's 13,000,000; the bullfinch's, 3,600,000; the lizard's, 
 1,420,000; the frog's, 404,000; the proteus', 36,000. In hybernating animals, Vierordt found 
 that the number of corpuscles diminished from 7,000,000 to 2,000,000 per cubic millimetre during 
 hybernation. ' 
 
 The invertebrata generally have colorless blood, with colorless corpuscles; but the earthworm, 
 and the larva of the large gnats, etc., have red blood whose plasma contains haemoglobin, while the 
 blood corpuscles themselves are colorless. Many invertebrates possess red, violet, brown, or green 
 opalescent blood with colorless corpuscles (amoeboid cells). In cephalopods, and some crabs, the 
 blood is blue, owing to the presence of a coloring matter (Hsemocyanin) which contains copper, 
 and combines with O [Bert, Rabuteau and Papillon, Frtdiricq, and Krukenberg). 
 
 [Elaborate measurements of the blood corpuse'es have been made in this country by Gulliver, but 
 the relative size may be best appreciated by comparing the corpuscles from various vertebrates. 
 There is no relation between the size of the animal and the size of its blood corpuscles.] 
 
 7. ORIGIN OF THE RED BLOOD CORPUSCLES.— (A; Origin 
 of the Nucleated Red Corpuscles during Embryonic Life. — Blood cor- 1 
 puscles are developed in the fowl during the first days of embryonic life. [They 
 appear in groups within the large branched cells of the mesoblast, in the vascular!, 
 area of the blastoderm outside the developing body of the chick or embryo, where \ 
 they form the "blood islands" of Pander. The mother cells form an irregular \ 
 network by the union of the processes of adjoining cells, and meantime the central j 
 masses split up, and the nuclei multiply. The small nucleated masses of pro- j 
 toplasm, which represent the ' blood corpuscles, acquire a reddish hue, while the 
 surrounding protoplasm, and also that of the processes, becomes vacuolated or j 
 hollowed out, constituting a branching system of canals ; the outer part of the 
 cells remaining with their nuclei to form the walls of the future blood vessels. A 
 fluid appears within this system of branched canals in which the corpuscles lie, 
 and gradually a communication is established with the blood vessels developed in 
 connection with the heart.] 
 
 [According to Klein, the nuclei of the protoplasmic wall may also proliferate, 
 and give rise to new corpuscles, which are washed away to form blood corpuscles.] 
 At first the corpuscles are devoid of pigment, nucleated, globular, larger, and j 
 more irregular than the permanent corpuscles, and they also exhibit amoeboid \ 
 movements. They become colored, retain their nucleus, and are capable of under- , 
 going multiplication by division ; and, in fact, Remak observed all the stages of J 
 the process of division. The process of division is best seen from the 3d-5th day 
 
^6 ORIGIN OF THE RED BLOOD CORPUSCLES. 
 
 of incubation. Increase by division also takes place in the larvae of the salaman- 
 der, triton and toad {Flemming, Peremeschkd), and also during the intra-uterine 
 life of a mammal, in the spleen, bone marrow, the liver and the circulating blood 
 {Bizzoaero, E berth). 
 
 ) After the liver is developed, blood corpuscles seem to be formed in it (JE. H. 
 Weber, Kolliker). Neumann found in the liver of the embryo protoplasmic cells 
 containing red blood corpuscles. Cells, some with, others without, Hb, but with 
 large nuclei, have been found. These cells increase by division, their nucleus 
 shrivels, and they then ultimately form blood corpuscles (Lowit). The spleen 
 is also regarded as a centre of their formation, but this seems to be the case only 
 during embryonic life {Neumann). Here the red corpuscles are said to arise from 
 yellow, round, nucleated cells, which represent transition forms. Foa and Sal- 
 violi found red corpuscles forming endogenously within large protoplasmic cells 
 in lymphatic glands. In the later period of embryonic life, the characteristic 
 non-nucleated corpuscles seem to be developed from the nucleated corpuscles. 
 The nucleus becomes smaller and smaller, breaks up, and gradually disappears. 
 In the human embryo at the fourth week only nucleated corpuscles are found ; at 
 the third month their number is still \-\ of the total corpuscles, while at the end 
 of foetal life nucleated blood corpuscles are very rarely found. Of course, in 
 
 Fig. 6. 
 
 Formation of red blood corpuscles within " vaso-formative cells," from the omentum of a rabbit seven days old. 
 r, r, the formed corpuscles ; K, K, nuclei of the vaso-formative cells ; a, a, processes which ultimately unite to 
 form capillaries. 
 
 animals with nucleated blood corpuscles, the nucleus of the embryonic blood cor- 
 puscles remains. 
 
 (B) Development of Blood Vessels, Formation of Blood Vessels 
 and Blood Corpuscles during Post-embryonic Life. — Kolliker assumed 
 that, in the tail of the tadpole, capillaries are formed by the anastomoses of the 
 processes of branched and radiating connective-tissue corpuscles. These cor- 
 puscles lose their nuclei and protoplasm, become hollowed out, join with neigh- 
 boring capillaries, and thus form new blood channels. J. Arnold and Von Golu- 
 bew, on the other hand, oppose this view. They assert that the blood capillaries 
 in the tail of the tadpole give off solid buds at different places, which grow more 
 and more into the surrounding tissues, and anastomose with each other; their pro- 
 toplasm and contents disappearing, they become hollow and a branched system of 
 capillaries is formed in the tissues. Ranvier, be it remarked, noticed the same 
 mode of growth in the omentum of newly-born kittens. 
 
 The latter observer has recently studied the development of blood vessels and 
 blood corpuscles in the omentum of young rabbits. These animals, when a week 
 old, have, in their omentum, little white or milk spots (" taches laiteuses," Ran- 
 vier), in which lie " vaso-formative cells," i. e., highly refractive cells of vari- 
 able shape, with long cylindrical protoplasmic processes (Fig. 6). In its refractive 
 
ORIGIN OF THE RED BLOOD CORPUSCLES. 27 
 
 power the protoplasm of these cells resembles that of lymph corpuscles. Long, 
 rod-like nuclei lie within these cells (K, K), and also red blood corpuscles [r, r), 
 and both are surrounded with protoplasm. These vaso-formative cells give off 
 protoplasmic points and processes (a, a), some of which end free, while others 
 form a network. Here and there elongated connective tissue corpuscles lie on 
 the branches, and ultimately form the adventitia of the blood vessel. 
 
 The vaso-formative cells have many forms : they may be elongated cylinders 
 ending in points, or more round and oval, resembling lymph cells, or they may 
 be modified connective-tissue corpuscles, as observed by Schafer in the sub- 
 cutaneous tissue of young rats. These cells are always the seat of origin of 
 non-nucleated red blood corpuscles, which arise in the protoplasm of vaso-formative 
 cells, as chlorophyll grains or starch granules arise within the cells of plants. 
 The corpuscles escape and are washed into the circulation, when the cells form 
 connections with the circulatory system by means of their processes. It is 
 probable that the vessels so formed in the omentum are only temporary. May 
 it not be that there are many other situations in the body where blood is 
 regenerated ? 
 
 [The observations of Schafer also prove the intra- cellular origin of red blood 
 corpuscles, and although this mode usually ceases before birth, still it is found in 
 the rat at birth. The protoplasm of the subcutaneous connective-tissue 
 corpuscles, which are derived from the mesoblast, has in it small colored 
 globules about the size of a colored corpuscle. The mother cells elongate, 
 become pointed at their ends, and unite with processes from adjoining cells. 
 The cells become vacuolated ; fluid or plasma, in which the liberated corpuscles 
 float, appears in their interior, and ultimately a communication is established 
 with the general circulation.] 
 
 Similar observations have been made by Neumann in the embryonic liver ; by Wissotzky in the 
 rabbit's amnion; by Klein in the embryo chick ; and by Leboucq and Hayem in various animals; 
 all of which go to show that at a certain early period of development blooi corpuscles are formed 
 within other large cells of the mesoblast, and that part of the protoplasm of these blood-forming cells 
 remains to form the wall of the future blood vessel. 
 
 [According to Bayerl red blood corpuscles are formed within cartilage capsules at the line of 
 ossification in the ribs and bones of the extremities of mammalian and human embryos.] 
 
 (C) Later Formation of Red Blood Corpuscles. — There is much diversity 
 of opinion as to how colored blood corpuscles are formed in mammals at a later 
 period. [They have been described as derived from colorless corpuscles, one set 
 of observers (including Kolliker) maintaining that the nucleus of these corpuscles 
 disappears, while the perinuclear portion remains, becomes flattened and colored, 
 and assumes the characters of the mammalian blood corpuscles. On the other 
 hand, other observers (including Wharton Jones, Gulliver, Busk, Huxley and 
 Balfour) are of opinion that the nucleus becomes pigmented, and forms the 
 future blood corpuscle. It is still doubtful, however, whether colored corpuscles 
 are developed in either of these ways.] Neumann and Bizzozero described 
 peculiar corpuscles occurring in the red marrow of bone, which they maintain 
 become developed into colored blood corpuscles, undergoing a series of changes, 
 and forming a series of intermediate forms, which may be detected in the red 
 marrow. Bizzozero holds that it is the nucleus of the marrow cell which is 
 colored, while Neumann thinks that it is the perinuclear part which becomes 
 colored, and forms the blood corpuscle. Schafer's observations on the red 
 marrow of the guinea pig rather tend to confirm Neumann's view. These 
 transition cells are said by Erb to be more numerous after severe hemorrhage, 
 the number of them occurring in the blood corresponding with the energy of the 
 formative process. In dogs and guinea pigs, which he had rendered anaemic, 
 Bizzozero found in the marrow and spleen nucleated red blood corpuscles, which 
 increased by division. According to Neumann, the bone marrow of adults 
 contains all transition forms, from nucleated colored corpuscles to true red blood 
 
28 DECAY OF THE RED BLOOD CORPUSCLES. 
 
 corpuscles. After copious hemorrhage, these transition forms appear in numbers 
 in the blood stream. 
 
 Red or blood-forming marrow occurs in the bones of the skull, and in mo: t of the bones of the 
 trunk, while the bones of the extremities either contain yellow marrow (which is essentially fatty 
 in its nature), or, at most, it is only the heads of the long bones that contain red marrow. When 
 the blood regeneration process is very active, however, the )ellow marrow may be changed into red, 
 even throughout all the bones of the extremities (A'eumann). 
 
 Rindfleisch also regards the connective substance of the red marrow and the spleen as the mother- 
 tissue of the red blood corpuscles, the connective-substance or the hsematogenous connective tissue 
 either temporarily or permanently forming red blood corpuscles. Once the red corpuscles are 
 formed, they easily enter the blood stream, as the capillaries or veins of the red marrow have either 
 no walls (Hoyer, Kollmann), or exceedingly thin, perforated walls. Similar conditions obtain in 
 the spleen. 
 
 Bizzozero and Torre found that, after severe hemorrhage in birds, the marrow of the bones 
 contained globular, granular, nucleated cells, whose protoplasm was colored with haemoglobin, 
 while between these and the oval, biconvex, nucleated corpuscles of the bird, there were numerous 
 transition stages. The spleen of the bird seems to be of much less importance in the formation of 
 blood corpuscles (Korn). All these observations prove that the red marrow of the bones is a great 
 manufactory lor colored blood corpuscles. 
 
 v. Recklinghausen observed the direct transformation of these intermediate forms into blood 
 corpuscles in frogs' blood which was kept for several days in a moist chamber. A. Schmidt and 
 Semmer found in the blood large lymph cells, filled with granules of hsemogoblin, and they legard 
 these as intermediate forms between colorless and colored corpuscles. 
 
 [Malassez, from an investigation of the red marrow of young kids, finds that the cells of the red 
 marrow and certain cells in the spleen form rounded colored projections or buds on their surface. 
 These get detached and form young blood corpuscles, which soon become disk-shaped ; while the 
 mother cell itself continues to produce other colored corpuscles. Thus gemmation of the splenic 
 and medullary cells constitutes one great process in the manufacture of blood corpuscles. Hence 
 it is apparent why diseases of the bone in children lead to anaemia, and soon bring about a cachectic 
 condition.] 
 
 [In mammals, birds, reptiles, and tailless amphibians, colored blood corpuscles divide in bone 
 marrow. In the tailed amphibians ( Triton crista'us) the bone marrow consists of fat, and shows 
 none of the characters of a blood-forming organ. In tailed amphibians, again, Bizzozero and Torre 
 find the first example of animals in which, in adults, red blood corpuscles are formed in the spleen, 
 where the process of indirect division is very marked, especially if the corpuscles be stained by 
 methyl-violet in ^ per cent. NaCl solution, and afterwaid with y% per cent, acetic acid.] 
 
 8. DECAY OF THE RED BLOOD CORPUSCLES.— The blood 
 corpuscles must positively undergo decay within a limited time, and the liver is 
 regarded as one of the chief places in which their disintegration occurs, because 
 bile pigments are formed from haemoglobin, and the blood of the hepatic vein 
 contains fewer red corpuscles than the blood of the portal vein. 
 
 The splenic pulp contains cells which seem to indicate that colored corpuscles 
 are broken up within it. These are the so-called "blood-corpuscle-containing 
 cells." Quincke's observations go to show that the red corpuscles — which may 
 live from three to four weeks — when about to disintegrate, are taken up by white 
 blood corpuscles, and by the cells of the spleen and the bone marrow, and are 
 stored up chiefly in the capillaries of the liver, in the spleen, and -in the marrow 
 of bone. They are transformed, partly into colored, and partly into colorless 
 proteids which contain iron, and are either deposited in a granular form, or are 
 dissolved. Part of the products of decomposition is used for the formation of 
 new blood corpuscles in the marrow and in the spleen, and also perhaps in the. 
 liver, while a portion of the iron is excreted by the liver in the bile. 
 
 That the normal red blood corpuscles and other particles suspended in the blood stream are not 
 taken up in this way, may be due to their being smooth and polished. As the corpuscles grow 
 older and become more rigid, they, as it were, are caught by the amceboid cells. As cells con- 
 taining blood corpuscles are very rarely found in the general circulation, one may assume that the 
 occurrence of these cells within the spleen, liver and marrow of bone is favored by the slowness of 
 the circulation in these organs {Quincke). 
 
 Pathological. — lit certain pathological conditions, ferruginous substances derived from the red 
 blood corpuscles are found in the spleen, in the marrow of bone, and in the capillaries of the 
 liver : (l) When the disintegration of blood corpuscles is increased, as in anaemia {Stahel). (2) 
 When the formation of red blood corpuscles from the old material is diminished. If the excretion 
 
THE COLORLESS BLOOD CORPUSCLES. 
 
 29 
 
 from the liver cells be prevented, iron accumulates within them; it is also more abundant in the 
 blood serum, and it may even accumulate in the secretory cells of the cortex of the kidney and 
 pancreas, in gland cells, and in the tissue elements of other organs [Quincke). When the amount 
 of blood is greatly increased (in dogs), after four weeks an enormous number of granules containing 
 iron occur in the leucocytes of the liver capillaries, the cells of the spleen, bone marrow, lymph 
 glands, the liver cells.and the epithelium of the cortex of the kidney (Quincke). The iron reaction 
 in the two last situations occurs after the introduction of haemoglobin, or of salts of iron into the 
 blood (Glaeveck and v. Stark). 
 
 When we reflect how rapidly (relatively) large quantities of blood are replaced 
 after hemorrhage and after menstruation, it is evident that there must be a brisk 
 manufactory somewhere. As to the number of corpuscles which daily decay, we 
 have in some measure an index in the amount of bile pigment and urine pigment 
 resulting from the transformation of the liberated haemoglobin (§ 20). 
 
 9. THE COLORLESS CORPUSCLES (LEUCOCYTES). 
 BLOOD PLATES AND ELEMENTARY GRANULES.— I. White 
 Blood Corpuscles. — Blood, like many other tissues, contains a number of cells 
 
 Fig. 7. 
 
 » VI * 
 
 White blood corpuscles. A, human, without the addition of any reagent : B, after the addition of water, nuclei 
 visible ; C, after the action of acetic acid ; D, frogs' corpuscles showing changes of shape due to amoeboid move- 
 ment; E, fibrils of fibrin from coagulated blood ; F, elemental y granules. 
 
 or corpuscles which reach it from without ; the corpuscles vary somewhat in form, 
 and are called colorless or white blood corpuscles, or "leucocytes" 
 (Hewson, 1770). Similar corpuscles are found in lymph, adenoid tissue, marrow 
 of bone, as wandering cells or leucocytes, in connective tissue, and also between 
 glandular and epithelial cells. They all consist of more or less spherical masses 
 of protoplasm, which is sticky, highly refractile, soft, capable of movement, and 
 devoid of an envelope (Fig. 7). When they are quite fresh (A) it is difficult to 
 detect the nucleus, but after they have been shed for some time, or after the 
 addition of water (B), or acetic acid, the nucleus (which is usually a compound 
 one) appears ; acetic acid clears up the perinuclear protoplasm, and reveals the 
 presence of the nuclei, of which the number varies from one to four, although 
 generally three are found. The subsequent addition of magenta solution stains 
 the nuclei deeply. Water makes the contents more turbid, and causes the 
 corpuscles .to swell up. One or more nucleoli may be present in the nucleus. 
 The corpuscles contain proteids, but they also contain fats, lecithin, and salts 
 
30 THE COLORLESS BLOOD CORPUSCLES. 
 
 (§ 24). The size of the corpuscles varies from four to thirteen ;i, and as a rule 
 they are about ^Jj^ of an inch in diameter, and in the smallest the layer of the 
 protoplasm is extremely thin. They all have the property of exhibiting amoeboid 
 movements, which are very apparent in the larger corpuscles. These movements 
 were discovered by Wharton Jones in the skate, and by Davine in the corpuscles 
 of man. Max Schultze describes three different forms in human blood : — 
 
 (1) The smallest, round forms, less than the red corpuscles, with one or two 
 nuclei, and a very small amount of protoplasm ; 
 
 (2) Round forms, the same size as the colored blood corpuscles ; 
 
 (3) The large amoeboid corpuscles, with much protoplasm and distinctly evi- 
 dent movements. 
 
 [When a drop of human blood is examined under the microscope, more especially after the 
 colored blood corpuscles have run into rouleaux, the colorless corpuscles may readily be detected, 
 there being usually three or four of them visible in the field at once. They adhere to the glass 
 slide, for if the cover glass be moved, the colored corpuscles readily glide over each other, while the 
 colorless can be seen still adhering to the slide.] 
 
 [White Corpuscles of Newt's Blood. — The characters of the colorless corpuscles are best 
 studied in a drop of newt's blood. Cut off the tip of the tail and express a drop of blood on to a 
 slide, cover it with a thin glass, and examine. Neglecting the colored corpuscles, search for the 
 colorless, of which there are three varieties: — 
 
 (1) The Large, Finely Granular Corpuscle, which is about j^ 5 of an inch in diameter, irregu- 
 lar in outline, with fine processes or pseudopodia projecting from its surface. It rapidly changes its 
 shape at the ordinary temperature, and in its interior a bi- or tripartite nucleus may be seen, sur- 
 rounded with fine granular protoplasm, whose outline is continually changing. Sometimes vacuoles 
 are seen in the protoplasm. 
 
 (2) The Coarsely Granular Variety is less common than the first mentioned, but when de- 
 tected its characters are distinct. The protoplasm contains, besides a nucleus, a. large number of 
 highly refractive granules, and the corpuscle usually exhibits active amoeboid movements ; suddenly 
 the granules may be seen to rush from one side of the corpuscle to the other. The processes are 
 usually more blunt than those emitted by (1). The relation between these two kinds of corpuscles 
 has not been ascertained. 
 
 (3) The Small, Colorless Corpuscles are more like the ordinary human colorless corpuscle, 
 and they, too, exhibit amoeboid movements. 
 
 Two kinds of colorless corpuscles like (1) and (2) exist in frogs' blood. In the coarsely granular 
 corpuscles the glancing granules may be of a fatty nature, since they dissolve in alcohol and ether, 
 but other granules exist which are insoluble in these fluids, and the nature of which is unknown. 
 Very large colorless corpuscles exist in the axolotl's blood (Ranvier).'] 
 
 [Action of Reagents. — (a) Water, when added slowly, causes the colorless 
 corpuscles to become globular, and the granules within them to exhibit Brownian 
 movements {Richardson, Strieker). (0) Pigments, such as magenta or carmine, 
 stain the nuclei very deeply,, and the protoplasm to a less extent. (c) Dilute 
 Acetic Acid clears up the surrounding protoplasm and brings clearly into view the 
 composite nucleus, which may be stained thereafter with magenta, (d) Iodine 
 gives a faint port-wine color (horse's blood indicating the presence of glycogen 
 best), {e) Dilute Alcohol causes the formation of clear 
 Fig. 8. blebs on the surface of the corpuscles, and brings the 
 
 nuclei clearly into view (Hanvier, Stirling).'] 
 
 [A. delicate plexus of fibrils — intra-nuclear plexus — 
 exists within the nucleus, just as in other cells. It is very 
 probable that the protoplasm itself is pervaded by a similar 
 plexus of fibrils, and that it is continuous with the intra- 
 nuclear plexus (Fig. 8).] 
 
 The colorless corpuscles divide, and in this way repro- 
 duce themselves (Klein). 
 
 The Number of Colorless Blood Corpuscles is 
 
 very much less than that of the red corpuscles, and is sub- 
 
 intneeib.hr and intranuclear J ect *° considerable variations. It is certain that the color- 
 
 piexus of a colorless cor- less corpuscles are very much fewer in shed blood than in 
 
 [a7«£). w " tw ° nuce ' blood still within the circulation. Immediately after blood 
 
AMCEBOID MOVEMENTS OF THE COLORLESS CORPUSCLES. 
 
 31 
 
 is shed, an enormous number of white corpuscles disappear (see Formation of 
 Fibrin, § 31). [The extent to which this occurs is questioned by different 
 observers.] 
 
 Al. Schmidt estimates the number that remain at -^ of the whole originally present in the circu- 
 lating blood. The proportion is greater in children than in adults (Bouchut and Dubrisay). 
 
 The following table gives the number in shed blood : — 
 
 Number of White Corpuscles in Proportion to Red Corpuscles- 
 
 In Normal Conditions. 
 
 I : 335 ( Welcker). 
 I : 357 (Molescholt). 
 
 In Different Places. 
 
 Splenic Vein, I : 60 
 Splenic Artery, I : 2260 
 Hepatic Vein, 1 : 170 
 Portal Vein, 1 : 740 
 Generally more numerous 
 Veins than Arteries. 
 
 In Different Conditions. 
 
 Increased by 
 Digestion, Loss of Blood, Pro- 
 longed Suppuration, Parturi- 
 tion, Leukaemia, Quinine, Bit- 
 ters. 
 
 Diminished by 
 Hunger, Bad Nourishment. 
 
 The number also varies with the Age and Sex :- 
 
 Age. Sex. 
 
 White. Red. 
 
 General Conditions. 
 
 White. Red. 
 
 Girls, 
 
 Boys, ... 
 
 Old Age 
 
 I : 405 
 I : 226 
 " = 334 
 1 = 381 
 
 While fasting, . . 
 After a meal, . . 
 During pregnancy, 
 
 I : 716 
 
 I = 347 
 I : 281 
 
 The old method of Welcker for estimating the number of colorless corpuscles is unsatisfactory. 
 The blood was defibrinated, placed in a tall vessel, and allowed to subside, when a layer of color- 
 less corpuscles was obtained immediately under a layer of serum. [It is better to use the hsema- 
 cytometer (p. 21) as improved by Gowers.] 
 
 The Amoeboid Movements of the white corpuscles (so called because they 
 resemble the movements of amoeba) consist in an alternate contraction and 
 relaxation of the protoplasm surrounding the nucleus. Processes are given off 
 from the surface, and are retracted again (like the pseudopodia of amoeba). 
 There is an internal current in the protoplasm, and the nucleus has also been 
 observed to change its form [and exhibit contractions without the corpuscle divid- 
 ing. The karyokinetic figures or aster, and convolution of the intranuclear 
 plexus have been seen] (Lawdowsky). Two series of phenomena result from these 
 movements: (1) The " wandering" or locomotion of the corpuscles due to the 
 extension and retraction of their processes ; (2). the absorption of small particles 
 into their interior (fat, pigment, foreign bodies). The particles adhere to the 
 sticky external surface, are carried into the interior by the internal currents 
 (Freyer), and may eventually be excreted, just as particles are taken up by amoeba 
 and the effete particles excreted. [Max Schultze observed that colored particles 
 were readily taken up by these corpuscles.] 
 
 [Conditions for Movement. — In order that the amoeboid movements of the 
 leucocytes may take place, it is necessary that there be — (1) a certain temperature 
 and normal atmospheric pressure ; (2) the surrounding medium, within certain 
 limits, must be "indifferent," and contain a sufficient amount of water and 
 oxygen ; (3) there must be a basis or support to move on.] 
 
 Metschnikoff emphasizes the activity of the leucocytes in retrogressive processes, whereby the 
 parts to be removed are taken up by them in fine granules, and, as it were, are " eaten." Hence, 
 he calls such cells " phagocytes." They may be found in the atrophied tails of batrachians, the 
 cells containing in their interior whole pieces of nerve fibre and primitive muscular bundles. Schizo- 
 
32 
 
 AMCEBOID MOVEMENTS OF THE COLORLESS CORPUSCLES. 
 
 mycetes which have found their way into the blood (g 183) have been found to be partly taken up 
 by the colorless corpuscles. 
 
 Effects of Reagents. — On a hot stage (35-40° C.) the colorless corpuscles 
 of warm-blooded animals retain their movements for a long time ; at 40° C. 
 for two to three hours ; at 50° C. the proteids are coagulated and cause " heat 
 rigor" and death [when their movements no longer recur on lowering the tem- 
 perature]. In cold-blooded animals (frogs), colorless corpuscles may be seen 
 to crawl out of small coagula, in a moist chamber, and move about in the serum. 
 [Draw a drop of newt's blood into a capillary tube, seal up the ends of the latter 
 and allow the blood to coagulate. After a time, examine the tube in clove oil, 
 when some of the colorless corpuscles will be found to have made their way out of 
 the clot.] Induction shocks cause them to withdraw their processes and become 
 
 Fig. 9. 
 
 Human leucocytes, showing amoeboid movements. 
 
 spherical, and, if the shocks be not too severe, their movements recommence. 
 Strong and continued shocks kill them, causing them to swell up, and completely 
 disintegrating them. Oxygen is necessary for their movements. 
 
 Diapedesis. — These amoeboid movements are of special interest on account 
 of the " wandering out " (diapedesis) of colorless blood corpuscles through the 
 walls of the blood vessels (§ 95). 
 
 [Effect of Drugs. — Acids and alkalies, if very dilute, at first increase, but afterward arrest their 
 movements. Sodic chloride in a 1 per cent, solution at first accelerates their movements, but after- 
 ward produces a tetanic contraction, and, it may be, expulsion of any food particles they contain. 
 The Cinchona alkaloids — quinine, quinidine, cinchonidine (1 : 1500) — quickly arrest the locomo- 
 tive movements, as well as the protrusion of pseudopodia, although the leucocytes of different 
 animals vary somewhat in their resistance to the action of drugs. Quinine not only arrests the 
 
THE BLOOD PLATES. 33 
 
 movements of the leucocytes when applied to them directly, but when injected into the circulation 
 of a frog to the amount of jj$ to part of the animal's weight, the leucocytes no longer pass through 
 the walls of the capillaries (Binz).'] 
 
 The chyle contains leucocytes, which are more resistant than those of the blood, but less so than 
 those of the coagulable transudations (Heyl). The leucocytes of the lymphatic glands may also 
 be dissolved (Rauschenbach). 
 
 Relation to Aniline Pigments. — Ehrlich has observed a remarkable relation of the white 
 
 corpuscles to acid (eosin, picric acid, aurantia), basic (dahlia, acetate of rosanilin), or neutral 
 
 (picrate of rosanilin) reactions. The smallest protoplasmic granules of the cells have diffeient 
 
 chemical affinities for these pigments. Thus Ehrlich distinguishes " eosinophile," " basophile," 
 
 . and " neutrophile " granules within the cells. Eosinophile granules occur in the leucocytes which 
 
 J come from bone marrow [myelogenic leucocytes). The small leucocytes, i.e., those about the size 
 
 of a colored blood corpuscle or slightly larger, are formed in the lymphatic glands (lymphogenic 
 
 1 L.). The large amoeboid multi-nucleated cells which are found outside the vessels in inflam- 
 
 ' mations exhibit a neutrophile reaction. Their origin is unknown, and so is that of the large 
 
 , uni-nuqleated cells, and the large cells with constricted nuclei (Ehrlich and Einhorn). The 
 
 I eosinophile corpuscles are considerably increased in leukaemia. The basophile granules occur also 
 
 I in connective-tissue corpuscles, especially in the neighborhood of epithelium ; they are always 
 
 greatly increased where chronic inflammation occurs. As such conditions are always accompanied 
 
 by an increased supply of the nutritive materials necessary for cells, Ehrlich has called these cells 
 
 " Mastzellen " ; they do not occur normally in human blood. 
 
 Fig. io. 
 
 "Blood plates" and their derivatives, partly after Bizzozero and Laker, i, red blood corpuscles on the fiat; 2, from 
 the side; 3, unchanged blood plates; 4, a lymph corpuscle, surrounded with blood plates; 5, blood plates 
 variously altered ; 6, a lymph corpuscle with two heaps of fused blood plates and threads of fibrin ; 7, group of 
 blood plates fused or run together; 8, a similar small heap of partially dissolved blood plates with fibrils of fibrin. 
 
 II. Blood Plates. — Special attention has recently been directed to another 
 element of the blood, the " blood plates " or " Blutplattchen " of Bizzozero ; 
 pale, colorless, oval, round, or lenticular discs of variable size (mean, 3 //). 
 According to Hayem (who called these structures hsematoblasts, supposing 
 that they were an early stage in the development of the red blood corpuscles), 
 they are forty times as numerous as the leucocytes. These blood plates may be 
 recognized in circulating blood, as in the mesentery of a chloralized guinea pig 
 and the wing of a bat. They are precipitated in enormous numbers upon threads 
 suspended in fresh shed blood (Bizzozero). They may be obtained from blood 
 flowing directly from a blood vessel, on mixing it with 1 per cent, solution of 
 osmic acid or Hayem's fluid (p. 23), (Laker). They undergo a rapid change in 
 shed blood (Fig. 10, 5), disintegrating, forming small particles, and ultimately 
 dissolving. When several occur together they rapidly unite, form small groups 
 (7), and collect into finely granular masses or " Kornchenhaufen." These masses 
 may be associated in coagulated blood with fibrils of fibrin (Fig. 10). 
 
 [These blood plates are seen in shed blood, best in the guinea pig, especially if it be mixed with 
 a solution of sodic sulphate (sp. gr. 1022) or Jjf per cent. NaCl tinged with methyl-violet (Bizzozero) .~\ 
 
 3 
 
34 CHANGES OF THE RED AND WHITE BLOOD CORPUSCLES. 
 
 Bizzozero believes that they are the agents which immediately induce coagulation and take part in 
 the formation of fibrin during coagulation of the blood ; Eberth and Schitnmelbusch ascribe the 
 formation of thrombi to them. It is not yet determined whether they are derived from partially 
 disintegrated leucocytes, as a consequence of alteration of the blood (Lowit), or whether they are 
 independent formations. Along with the leucocytes they are concerned in the formation of fibrin 
 (//lava). These structures were known to early observers (Max Schultze, Riess, and others); 
 but their significance has been variously interpreted. Halla found that they are increased in 
 pregnancy, and Afanassiew in conditions of regeneration of the blood. [Gibson's view is that these 
 blood plates, which he calls colorless microcytes, are derived from the nucleus of young red blood 
 corpuscles, or, occasionally from the nucleus of white corpuscles.] 
 
 [As to the hcematoblasts, or, as they have also been called, the "globules of DonnS" by 
 Pouchet, there seems to be some confusion, for both colored and colorless granules are described 
 under these names. As Gibson suggests, the former are, perhaps, parts of disintegrated colored 
 corpuscles, whilst the latter are the blood plates.] 
 
 [The "invisible blood corpuscles" described by Norris seem to be simply decolorized red 
 corpuscles {Hart, Gibson), .] 
 
 III. Elementary Granules. — Blood, especially after a microscopic prepara- 
 tion has been made for a short time, is seen to contain elementary granules 
 (Fig. 7, F), [i.e., the elementary particles of Zimmermann and Beale. They are 
 irregular bodies, much smaller than the ordinary corpuscles, and appear to consist 
 of masses of protoplasm detached from the surface of leucocytes, or derived from 
 the disintegration of these corpuscles, or of the blood plates. Others, again, are 
 completely spherical granules, either consisting of some proteid substance or fatty 
 in their nature. The protoplasmic and the proteid granules disappear on the 
 addition of acetic acid, while the fatty granules (which are most numerous after a 
 diet rich in fats) dissolve in ether]. 
 
 [Gibson is of opinion that some of the granules are fragments of broken-down red corpuscles. 
 He calls them colored microcytes, and considers them as representing one stage of Hayem's haemato- 
 blasts.] 
 
 [It seems, then, that in addition to the red and white corpuscles, there are two 
 distinct elements in shed blood, one the colored microcyte of Gibson, derived from 
 broken-down red corpuscles, and the other the blood plates or colorless microcyte.~\ 
 
 [When the blood-forming process is particularly active, " nucleated colored 
 corpuscles," or the "corpuscles of Neumann," are sometimes found in the 
 blood. They are identical with the nucleated colored blood corpuscles of the 
 foetus, being somewhat larger than the non-nucleated colored corpuscle (§ 7).] 
 
 IV. In coagulated blood, delicate fibrils or threads of fibrin (Fig. 7, E, and 
 10, 6, 7, 8) are seen, more especially after the corpuscles have run into rouleaux. 
 At the nodes of these fibres are found granules which closely resemble those 
 described under II. [These granules and fibres are stained by magenta and 
 iodine, but not by carmine or picrocarmine (Ranvier).~\ 
 
 10. ABNORMAL CHANGES OF THE RED AND WHITE BLOOD COR- 
 PUSCLES. — (I) All hemorrhages diminish the number of red corpuscles (at most one-half), 
 and so does )nenstruation. The loss is partly covered by the absorption of fluid from the tissues. 
 Menstruation shows us that a moderate loss of red corpuscles is replaced within twenty-eight days. 
 When a large amount of blood is lost, so that all the vital processes are lowered, the time may be 
 • extended to five weeks. In acute fevers , as the temperature increases, the number of red corpuscles 
 1 diminishes, while the white corpuscles increase in number (Riegel and Boekmann, Halla). 
 
 By greatly cooling periphtral parts of the body, as by keeping the hands in iced water, in some 
 individuals possessing red blood corpuscles of low resisting power, these corpuscles are dissolved, 
 the blood plasma is reddened, and even hemoglobinuria (§ 265) may occur (Lichtheim, Boas). 
 
 Diminished production of new red corpuscles causes a decrease, since blood corpuscles are 
 continually being used up. In chlorolic girls there seems to be a congenital weakness in the blood- 
 forming and blood-propelling apparatus, the cause of which is to be sought for in some faulty con- 
 dition of the mesoblast. In them the heart and the blood vessels are small, and the absolute number 
 of corpuscles may be diminished one-half, although the relative number may be retained, while in 
 the corpuscles themselves the haemoglobin is diminished almost one-third (Duncan, Quincke) ; but 
 it rises again after the administration of iron [Hayem). The administration of iron increases the 
 amount of haemoglobin in the blood (Scherpf). 1 he amount of iron in the blood may be diminished 
 one-half. [The action of iron in anaemic persons has been known since the time of Sydenham. 
 
CHEMICAL CONSTITUENTS OF THE RED BLOOD CORPUSCLES. 35 
 
 Hayem also finds that in certain forms of anaemia there is considerable variation in the size of the 
 red corpuscles, and that in chronic anaemia the mean diameter of the corpuscles is always less than 
 normal (7 ft to 6 ft). There is, moreover, a persistent alteration in the volume, coloring power, and 
 consistence of the corpuscles, consequently a want of accord between the number of the corpuscles 
 and their coloring power, i. e., the amount of haemoglobin which they contain, as was pointed out 
 by Johann Duncan.] In so-called pernicious ancemia, in which the continued decrease in the red 
 corpuscles may ultimately produce death, there is undoubtedly a severe affection of the blood-form- 
 ing apparatus. The corpuscles assume many abnormal and bizarre forms (microcytes), often being 
 oval or tailed, irregularly shaped, and sometimes very pale ; while numerous cells containing blood 
 corpuscles are found in the marrow of bone (Jfiess). Curiously enough, in this disease, although 
 the red blood corpuscles are diminished in number, some may be larger and contain more haemo- 
 globin than do normal corpuscles (Laache). The number of colored corpuscles is also diminished 
 in chronic poisoning by lead or miasmata, and also by the poison of syphilis. 
 
 (2) Abnormal forms of the red corpuscles have been observed after severe burns (Lesser) ; the 
 corpuscles are much smaller, and under the influence of the heat particles seem to be detached 
 from them, just as can be seen happening under the microscope as the effect of heat (Wertheim). 
 Disintegration of the corpuscles into fine droplets has been observed in various diseases, as in severe 
 malarial fevers. The dark granules of a pigment closely related to haematin are derived from the 
 granules arising from the disintegration of the blood corpuscles, and these particles float in the blood 
 (Melanaemia). They are partly absorbed by the colorless corpuscles, but they are also deposited 
 in the spleen, liver, brain and bone marrow (Arnstein). Sometimes the red corpuscles are ab- 
 normally soft, and readily yield to pressure. 
 
 The white corpuscles are enormously increased in number in Leukaemia (J. H. Sennet and 
 Virchow) ; sometimes even to the extent of the red corpuscles. In some cases the blood looks as 
 if it were mixed with milk. The colorless corpuscles seem to be formed chiefly in bone marrow 
 (£. Neumann), but also in the spleen and lymphatic glands (myelogenic, splenic and lymphatic 
 leukaemia). 
 
 11. CHEMICAL CONSTITUENTS OF THE RED BLOOD 
 CORPUSCLES.— (1) The coloring matter or haemoglobin (Hb) 
 (Haematoglobulin, Hsematocrystallin), is the cause of the red color of blood ; it 
 also occurs in muscle, and in traces in the fluid part of blood, but in this last case 
 only as the result of the solution of some red corpuscles, lis percentage composi- 
 tion is : C 53.85, H 7.32, N 16.17, Fe 0.42, S 0.39, O 21.84 (dog). Its rational 
 formula is unknown, but Preyer gives the empirical formula C 600 , H 960 , N 154 , 
 Fe, S 3 , 179 . Although it is a colloid substance it crystallizes ^Hunefeld, 1840, 
 Reicherf) in all classes of vertebrates, according to the rhombic system, and 
 chiefly in rhombic plates or prisms; in the guinea pig in rhombic tetrahedra 
 {v. Lang) ; in the squirrel, however, it yields hexagonal plates. The varying 
 forms, perhaps, correspond to slight differences FlG 
 
 in the chemical composition in different cases. 
 Crystals separate from the blood of all classes of ■'■ 
 
 vertebrata during the slow evaporation of lake- 
 colored blood, but with varying facility (Fig. 11). 
 
 The coloring matter crystallizes very readily from the 
 blood of man, dog, mouse, guinea pig, rat, cat, hedgehog, 
 horse, rabbit, birds, fishes; with difficulty from that of the 
 sheep, ox and pig. Colored crystals are not obtained from 
 the blood of the frog. More rarely a crystal is formed from 
 a single corpuscle enclosing the stroma. Crystals have been 
 found near the nucleus of the large corpuscles of fishes, and 
 in this class of vertebrates colorless crystals have been 
 observed. 
 
 Haemoglobin crystals are doubly refractive and 
 pleo-chromatic ; they are bluish red with trans- 
 mitted light, scarlet-red by reflected light. They 
 contain from 3 to 9 per cent, water of crystalliza- 
 tion, and are soluble in water, but more so in 
 dilute alkalies. They are insoluble in alcohol, 
 ether, chloroform, and fats. The solutions are 
 dichroic; red in reflected light, and green in 
 
 Haemoglobin crystals, a, b t from human 
 blood ; c, from the cat ; d, from the 
 guinea pig ; e, hamster ; /, squirrel. 
 
36 QUANTITATIVE ESTIMATION OF H/EMOGLOBIN. 
 
 transmitted light. [The solutions are readily decomposed by boiling, while they 
 are precipitated by mineral acids, alcohol, and acetic acid.] 
 
 In the act of crystallization the haemoglobin seems to undergo some internal change. Before it 
 crystallizes it does not diffuse like a true colloid, and it also rapidly decomposes hydric peroxide. 
 If it be redissolved after crystallization, it diffuses, although only to a small extent, but it no longer 
 decomposes hydric peroxide, and is decolorized by it. A body like an acid is deposited from 
 haemoglobin at the positive pole of a battery. [The presence of O favors crystallization.] 
 
 [Haemoglobin exists in two states, either as reduced haemoglobin, i. e., free 
 from oxygen, or as oxyhsemoglobin. The former is non-crystalline. They differ 
 in their color and spectra ; § 15.] 
 
 12. PREPARATION OF HAEMOGLOBIN CRYSTALS.— Method of Rollett.— 
 Place defibrinated blood in a platinum capsule, allow the capsule and the blood to freeze by placing 
 them in a freezing mixture, and then gradually to thaw ; pour the lake-colored blood into a plate, 
 until it forms a stratum not more than I y z mm. in thickness, and allow it to evaporate slowly in a 
 cool place, when crystals will separate. 
 
 Method of Hoppe-Seyler. — Mix defibrinated blood with 10 volumes of a 20 per cent, salt 
 solution, and allow it to stand for two days. Remove the clear upper fluid with a pipette, wash the 
 thick deposit of blood corpuscles with water, and afterward shake it for a long time with an equal 
 volume of ether, which dissolves the blood corpuscles. Remove the ether, filter the lake-colored 
 blood, add to it % of its volume of cold (0°) alcohol, and allow the mixture to stand in the cold 
 for several days. The numerous crystals can be collected on a filter and pressed between folds of 
 blotting paper. 
 
 Method of Gscheidlen. — Crystals several centimetres in length were obtained by taking de- 
 fibrinated blood which had been exposed for twenty-four hours to the air, and keeping it in a closed 
 tube of narrow calibre for several days at 37° C. When the blood is spread on glass, the crystals 
 form rapidly. [Vaccine tubes answer very well.] 
 
 [Method of Sterling and Brito. — It is in many cases sufficient to mix a drop of blood with 
 a few drops of water on a microscopic slide, and to seal up the preparation. After a few days 
 beautiful crystals are developed. The addition of water to the blood of some animals, such as the 
 rat and the guinea pig, is rapidly followed by the formation of crystals of haemoglobin. Very large 
 crystals may be obtained from the stomach of the leech several days after it has sucked blood.] 
 
 13. QUANTITATIVE ESTIMATION OF HEMOGLOBIN. — (a) From the 
 Amount of Iron. — As dry (160° C.) haemoglobin contains 0.42 per cent, of iron, the amount of 
 iron may be calculated from the amount of haemoglobin. If m represents the percentage amount 
 of metallic iron, then the percentage of haemoglobin in blood is 
 
 100 m 
 
 0.42 
 The procedure is the following : Calcine a weighed quantity of blood, and exhaust the ash with 
 HC1 to obtain ferric chloride, which is transformed into ferrous chloride. The solution is then 
 titrated with potassic permanganate. 
 
 (i) Colorimetric Method. — Prepare a. dilute watery solution of haemoglobin crystals of a 
 known strength. With this compare an aqueous dilution of the blood to be investigated, by adding 
 water to it until the color of the test solution is obtained. Of course, the solutions must be com- 
 pared in vessels with parallel sides and of exactly the same width, so as to give the same thickness 
 of fluid [Hoppe-Seyler). [In the vessel with parallel sides, or, haematinometer, tbe sides are 
 exactly one centimetre apart. Instead of using a standard solution of oxyhsemoglobin, a solution 
 of picrocarminate of ammonia may be used (Kajewsky, Malassez)."] 
 
 (c) By the Spectroscope. — Preyer found that an 0.8 per cent, watery solution (1 cm. thick), 
 allowed the red, the yellow, and the first strip of green to be seen (Fig. 14, 1). Take the blood to 
 be investigated (about 0.5 cm ), and dilute it with water until it shows exactly the same optical 
 effects in the spectroscope. If k is the percentage of Hb, which allows green to pass through (0.8 
 per cent.), b, the volume of blood investigated (about 0.5 cm.), w, the necessary amount of water 
 added to dilute it, then x = the percentage of Hb in the blood to be investigated — 
 
 k [w + b) 
 
 b 
 
 It. is very convenient to add a drop of caustic potash to blood and then to shake it up with CO. 
 
 [(</) The Haemoglobinometer of Gowers is used for the clinical estimation of haemoglobin 
 (Fig. 12).] "The tint of the dilution of a given volume of blood with distilled water is taken as 
 the index of the amount of haemoglobin. The distilled water rapidly dissolves out all the haemo- 
 globin, as is shown by the fact that the tint of the dilution undergoes no change on standing. The 
 color of a dilution of average normal blood one hundred times is taken as the standard. The 
 quantity of haemoglobin is indicated by the amount of distilled water needed to obtain the tint with 
 
QUANTITATIVE ESTIMATION OF HAEMOGLOBIN. 
 
 37 
 
 the same volume of blood under examination as was taken of the standard. On account of the 
 instability of a standard dilution of blood, tinted glycerine jelly is employed instead. This is per- 
 fectly stable, and by means of carmine and picrocarmine the exact tint of diluted blood can be 
 obtained. The apparatus consists of two glass tubes of exactly the same size. One contains (D) a 
 standard of the tint of a dilution of 20 cubic mm. of blood, in two cubic centimetres of water (1 in 
 100). The second tube (C) is graduated, 100 degrees = 2 centimetres (100 times 20 cubic milli- 
 metres). The 20 cubic millimetres of blood are measured by a capillary pipette (B) (similar to, but 
 larger than, that used for the haemacytometer.) This quantity of the blood to be tested is ejected into 
 the bottom of the tube, a few drops of distilled water being first placed in the latter. The mixture 
 is rapidly agitated, to prevent the coagulation of the blood. The distilled water is then added, drop 
 by drop (from the pipette stopper of a bottle (A) supplied for that purpose) until the tint of the dilution 
 is the same as that of the standard, and the amount of water which has been added (». e., the degree 
 of dilution) indicates the amount of haemoglobin. 
 
 " Since average normal blood yields the tint of the standard at 100 degrees of dilution, the 
 number of degrees of dilution necessary to obtain the same tint with a given specimen of blood is 
 the percentage proportion of the haemoglobin contained in it, compared to the normal. For instance, 
 the 20 cubic millimetres of blood from a patient with anaemia gave the standard tint of 30 degrees 
 of dilution. Hence it contained only 30 per cent, of the normal quantity of hsemoglobin. By 
 ascertaining with the haemacytometer the corpuscular richness of the blood, we are able to compare 
 the two. A fraction, of which the numerator is the percentage of haemoglobin, and the denomi- 
 
 FlG. 12. 
 
 A, pipette bottle for distilled water ; B, capillary pipette ; 
 lancet for pricking the finger. 
 
 C, graduated tube ; D, tube with standard dilution ; F, 
 
 nator the percentage of corpuscles, gives at once the average value per corpuscle. Thus the blood 
 mentioned above containing 30 per cent, of haemoglobin, contained 60 per cent, of corpuscles ; 
 hence the average value of each corpuscle was $$ or \ of the normal. Variations in the amount of 
 haemoglobin may be recorded on the same chart as that employed for the corpuscles. 
 
 " In using the instrument, the tint may be estimated by holding the tubes between the eye and the 
 window, or by placing a piece of white paper behind the tubes ; the former is perhaps the best. 
 Care must be taken that the tubes are always held in the line of light, not below it. In the latter 
 case some light is reflected from the suspended corpuscles from which the haemoglobin has been dis- 
 solved. If the value of the corpuscles is small, then a perceptibly paler tint is seen when the tubes 
 are held below the line of illumination. If all the light is transmitted directly through the tubes, 
 the corpuscles do not interfere with the tint. In practice it will be found that, during six or eight 
 degrees of dilution, it is difficult to distinguish a difference between the tint of the tubes. It is 
 therefore necessary to note the degree at which the color of the dilution ceases to be deeper than the 
 standard, and also that at which it is distinctly paler. The degree midway between these two will 
 represent the haemoglobin percentage. 
 
 " The instrument is only expected to yield approximate results, accurate within two or three per 
 cent. It has, however, been found of much utility in clinical observation." 
 
 The amount of haemoglobin in man is 13.77 per cent., in the woman 12.59 per 
 cent. {J. G. Oti), during pregnancy 9 to 12 per cent. (Preyer). According to 
 
38 
 
 USE OF THE SPECTROSCOPE. 
 
 Leichtenstern, Hb is in greatest amount in the blood of a newly-born infant, but 
 after ten weeks the excess disappears. Between six months and five years it 
 becomes least in amount, reaches its second highest maximum between twenty-one 
 and forty-five, and then sinks again. From the tenth year onward the blood of 
 the female is poorer in Hb. The taking of food causes a temporary decrease of 
 the Hb, owing to the dilution of the blood. 
 
 Pathological. — A decrease is observable during recovery from febrile conditions, and also during 
 phthisis, cancer, ulcer of the stomach, cardiac disease, chronic diseases, chlorosis, leukaemia, perni- 
 cious anaemia, and during the rapid mercurial treatment of syphilitic persons. 
 
 14. USE OF THE SPECTROSCOPE. — As the spectroscope is frequently used in the in- 
 vestigation of blood and other substances of the body, it will be convenient to give a short descrip- 
 tion of the instrument here (Fig. 13). It consists of (1) a tube, A, which has at its peripheral end 
 al slit, S (that can be narrowed or widened). At the other end a collecting lens, C (called a colli- 
 mator), is placed, so that its focus is in exact line with the slit. Light (from the sun or a lamp) 
 passes through the slit, and thus goes parallel through C to (2) the prism, P, which decomposes 
 the parallel rays into a colored spectrum, r, v. (3) An astronomical telescope is directed to the 
 spectrum, /-, v, and the observer, B, with the aid of the telescope, sees the spectrum magnified from 
 
 Fig. 13. 
 
 Scheme of a spectroscope for observing the spectrum of blood, A, tube ; S, slit ; nt m, layer of blood with flame 
 in front of it ; P, prism ; M, Scale ; B, eye of observer looking through a telescope ; r, v, spectrum. 
 
 six to eight times. (4) A third tube, D, contains a delicate scale, M, on glass, whose image, when 
 illuminated, is reflected from the prism to the eye of the observer, so that he sees the spectrum, and 
 over and above it the scale. To keep out other rays of light the inner ends of the three tubes are 
 covered by metal or by a dark cloth (see also § 265). 
 
 [The micro-spectroscope, e.g., that known as the *' Sorby-Browning " micro spectroscope, may be 
 used when small quantities of a solution are to be examined. While the corresponding instrument 
 of Zeiss is also most admirable.] 
 
 [Every spectroscope ought to give two spectra, so that the position of any absorption band may be 
 definitely ascertained. The spectroscope is fitted into the ocular end of the tube of a microscope 
 instead of the e>e piece. Small cells for containing the fluid to be examined are made from short 
 pieces of barometer tubes cemented to a piece of glass.] 
 
 Absorption Spectra. — If a colored medium (e.g., a solution of blood) be placed between the 
 slit and a source of light, all the rays of colored light do not pass through it — some are absorbed ; 
 many yellow rays are absorbed by blood, hence that part of the spectrum appears dark to the 
 observer. On account of this absorption, such a spectrum is called an " absorption spectrum" 
 
 Flame Spectra.— If mineral substances be burned on a platinum wire in a non-luminous flame 
 (Bunsen's burner) in front of the slip, the elements present in the mineral or ash give a special colored 
 band or bands, which have a definite position. Sodium gives a yellow, potassium a red and a violet 
 line. These substances are found in burning the ashes of almost all .organs. 
 
COMPOUNDS OF HAEMOGLOBIN. 
 
 39 
 
 If sunlight be allowed to fall upon the slit, the spectrum shows a large number of lines {Fraun- 
 hafet's lines) which occupy definite positions in the colored spectrum. These lines are indicated by 
 the letters A, B, C, D, etc., a, b, c, etc. (Fig. 14). 
 
 15. COMPOUNDS OF HAEMOGLOBIN WITH O; OXYHE- 
 MOGLOBIN AND METH^MOGLOBIN.-i. Oxyhemoglobin 
 
 (0 2 Hb) behaves as a weak acid, and occurs to the extent of 86.78 to 94.30 per 
 cent, in dry human red corpuscles (Jtidelf). It is formed very readily whenever 
 Hb comes into contact with O or atmospheric air. 1 gramme Hb unites with 
 1.202 cubic centimetres of O at o° and 1 metre Hg pressure {Hufner 1 ). Oxyhsemo- 
 
 ' Fig. 14. 
 
 Red. Orange. 
 
 Green. 
 
 iii|iiii|iiii|iiujiii |l-UI|ui.i|IILI|uli|llii|iiii|iiii'|||||i||ii' l ]TTT 
 4o 50 l 60 70 so qo 100 113 
 
 A a B C D E F 
 
 Various spectra of haemoglobin and its compounds. 
 
 Hsemattn in 
 
 an Alkaline 
 
 Solution. 
 
 Reduced 
 Hsematin. 
 
 globin is a very loose chemical compound, and is slightly less soluble than Hb ; 
 its spectrum shows in the yellow and the green two dark absorption bands {Hoppe- 
 Seyler) whose length and breadth in an o. 18 per cent, solution are given in Fig. 14 
 (2). [If the solution be very weak, only the narrow band near D is obtained.] 
 
 [The two absorption bands lie between the lines D and E, the band nearer D. 
 being more sharply defined and narrower than the second band, which is wider 
 and less clearly marked off, and lies nearer E.] 
 
 It occurs in the blood corpuscles circulating in arteries and capillaries, as was 
 
40 
 
 METtLEMOGLOBIN. 
 
 shown by the spectroscopic examination of the ear of a rabbit, of the prepuce, 
 and the web of the fingers (Vierordt). 
 
 Reduction of Oxyhaemoglobin. — It gives up its O very readily, however, 
 even when means which set free absorbed gases are used. It is reduced by the 
 removal of the gases by the. air pump, by the conduction through its solution of 
 other gases (CO and NO), and by heating to the boiling point. In the circulating 
 blood its O is very rapidly given up to the tissues, so that in suffocated animals 
 only reduced haptoglobin is found in the arteries. Some constituents of the serum 
 and sugar use up O. By adding to a solution of oxyhaemoglobin reducing sub- 
 stances — e.g., ammonium sulphide, ammoniated tartarate of zinc oxide solution, 
 iron filings, or Stokes's fluid [tartaric acid", iron protosulphate and excess of 
 ammonia] — the two absorption bands of the spectrum disappear, and reduced 
 hamoglobin (gas free) (Fig. 14, 4), with one absorption band, is formed (Stokes, 
 1864). [The single band which is obtained from reduced haemoglobin lies between 
 D and E, and its most deeply shaded portion is opposite the interval between the 
 two bands of oxyhaemoglobin. Its edges are less sharply defined. The color of 
 the blood changes from a bright red to a brownish tint. Hoppe-Seyler applies 
 the term Hcemoglobin to the reduced substance, to distinguish it from oxyhaemo- 
 globin.] The two bands are reproduced by shaking the reduced haemoglobin with 
 air, whereby O a Hb is again formed. Solutions of oxyhaemoglobin are readily 
 distinguished, by their scarlet color, from the purplish tint of reduced haemoglobin. 
 
 If a string be tied round the base of two fingers so as to interrupt the circulation, the spectro- 
 scopic examination shows that the oxyhaemoglobin rapidly passes into reduced Hb ( Vierordt). 
 Cold delays this reduction {Filehne), it is accelerated in youth, during muscular activity, or 
 by suppressed respiration, and usually also during fever [Denning). 
 
 The spectroscopic examination of small blood stains is often of the utmost forensic importance. 
 A minimal drop is sufficient. Dissolve the stain in a few drops of distilled, water, and place in a 
 thin glass tube in front of the slit of the spectroscope. 
 
 [Haemoglobin has certain remarkable characters : — 
 
 (1) Although it is a crystalloid body it diffuses with difficulty through an 
 animal membrane, owing to the large size of its molecule. 
 
 (2) It readily combines with O to form an unstable and loose chemical com- 
 pound, oxyhaemoglobin. 
 
 (3) This O it gives up readily to the tissues or other deoxidizing reagents. 
 
 (4) Its composition is very complex, for in addition to the ordinary elements 
 present in proteids, it contains a remarkable amount of iron (0.4 per 
 cent).] 
 
 2. Methsemoglobin (Hoppe Seyler) is a more stable, crystalline compound. 
 It contains the same amount of O as 2 Hb, but in a different chemical union, 
 while the O is also more firmly united with it (Killz, Hufner,J. G. Off'). It shows 
 four absorption bands like haematin in acid solution (Fig. 14, 5), of which those 
 between C and D are distinct ; the second is very indistinct, while the third and 
 fourth readily fuse, so that these last are only well seen with good apparatus. 
 
 Methsemoglobin is only formed from solutions of Hb, and not within the blood corpuscles 
 [v Mering). It is produced spontaneously in old brown blood stains, in the crusts of bloody 
 wounds, in blood cysts, and in bloody urine. It is also formed by the addition of minute traces of 
 acid to blood, or by heating blood with a trace of alkali. Chemically, it can be prepared in a solu- 
 tion of Hb, by the action of potassic ferricyanide [Jaderholm) or potassic chlorate [Marchand), 
 [or by adding to a solution of Hb a freshly-prepared solution of potassic permanganate] . 
 
 If a trace of ammonia be added to a solution of methsemoglobin, it gives an alkaline solution of 
 methsemoglobin, which shows two bands like oxyhemoglobin, of which the first one is the broader, 
 and extends more into the red. If ammonium sulphide be added to the methsemoglobin solution, 
 reduced Hb is formed. 
 
 16. CARBONIC OXIDE HEMOGLOBIN AND POISONING 
 "WITH CO. — 3. CO- Haemoglobin is a more stable chemical compound than 
 the foregoing, and is produced at once when carbonic oxide is brought into con- 
 
POISONING BY CARBONIC OXIDE. 41 
 
 tact with pure Hb or 2 Hb {CI. Bernard, 1857). It has an intensely florid or 
 cherry-red color, and gives two absorption bands, very like those of 2 Hb, but 
 they are slightly closer together and lie more toward the violet (Fig. 14, 3). 
 Reducing substances (which act upon Hb0 2 ) do not affect these bands, i. <?., 
 they cannot convert the CO compound into reduced Hb. Another good test to 
 distinguish it from Hb0 2 is the soda test. If a 10 per cent, solution of caustic 
 soda be added to a solution of CO-Hb. and heated, it gives a cinnabar-red color ; 
 while, with an Hb0 2 solution, it gives a dark brown, greenish, greasy mass 
 (Hoppe-Seyler). Oxidizing substances [solutions of potassic permanganate (0.025 
 per cent.), potassic chlorate (5 per cent.), and dilute chlorine solution] make 
 solutions of CO-Hb cherry-red in color, while they turn solutions of 2 Hb pale 
 yellow. After this treatment both solutions show the absorption baVids of 
 methsemoglobin, but those of the CO-Hb appear considerably later. If ammo- 
 nium sulphide be added, 2 Hb and CO-Hb are reformed {Th. Weyl and v. 
 Anrep). 
 
 On account of its stability, CO-Hb resists external influences and even putrefaction for a long 
 time (Hoppe Seyler), and the two bands of the spectrum may be visible after many months. Lan- 
 dois obtained the soda test and spectroscopic bands in the blood of a woman poisoned eighteen 
 months previously by CO, and after great putrefaction of the body had taken place. [Stirling has 
 kept CO-Hb in a stoppered bottle for four years without its undergoing putrefaction.] 
 
 If CO is breathed by man, or if air containing it be inspired, it gradually dis- 
 places the O, volume for volume, out of the Hb (Z. Meyer), and death soon 
 occurs; 1000 c.cm. inspired at once will kill a man. A very small quantity in 
 the air (^fai — twoO suffices, in a relatively short time, to form a large quantity of 
 CO-Hb {Grihant). As continued contact with other gases (such as the passing 
 of O through it for a very long time), gradually separates the CO from the Hb 
 (with the formation of 2 Hb (Do/iders)), it happens that, in very partial poison- 
 ing with CO, the blood gradually gets rid of the latter, so that only a very small 
 part of the CO is excreted by the respiratory organs ; the largest amount is more 
 highly oxidized in the body into C0 2 and thus excreted (Juries). [CO-Haemo- 
 globin, being a comparatively stable compound when once formed, circulates in 
 the blood vessels ; but it neither gives up oxygen to the tissues, nor takes up 
 oxygen in the lungs, hence its very poisonous properties. The real cause of 
 death in animals poisoned with it is that the internal respiration is arrested.] 
 
 [Gamgee and Zuntz also find that although the CO-Hb compound is very stable, yet it may 
 be reduced bypassing air or neutral gases through it for a lengthened period; it is also reduced 
 when blood is boiled in the mercurial pump.] 
 
 Poisoning with Carbonic Oxide. — Carbonic oxide is formed during incomplete combustion of 
 coal or coke, and passes into the air of the room, provided there is not a free outlet for the products 
 of combustion. It occurs to the extent of 12-28 per cent, in ordinary'gas, which largely owes its 
 poisonous properties to the presence of CO. If the O be gradually displaced from the blood by 
 the respiration of air containing CO, life can only be maintained as long as sufficient O can be 
 obtained from the blood to support the oxidations necessary for life. Death occurs before all the 
 O is displaced from the blood. CO has no effect when directly applied to muscle and nerve. When 
 it is inhaled, there is first stimulation and afterward paralysis of the nervous system, as shown by 
 the symptoms induced, c. g., violent headache, great restlessness, excitement, increased activity of 
 the heart and respiration, salivation, tremors and spisms. Later, unconsciousness, weakness and 
 paralysis occur, labored respiration, diminished heart beat, and, lastly, complete loss of sensibility, 
 cessation of the respiration and heart beat, and death. At first the temperature rises several tenths 
 of a degree, but it soon falls 1° or more. The pulse is also increased at first, but afterward it 
 becomes very small and frequent. 
 
 In poisoning with pure CO there is no dyspnoea, but sometimes muscular spasms occur, the coma 
 not being very marked. There is also temporary but pronounced paralysis of the limbs, followed 
 by violent spasms. After death, the heart and brain are congested with intensely florid blood. In 
 poisoning with the vapor of charcoal, where CO and C0 2 both occur, there is a varying degree 
 of coma ; pronounced dyspnoea, muscular spasms which may last several minutes, gradual paralysis 
 and asphyxia, moniliform contractions and subsequent dilatation of the blood vessels, with conges- 
 tion of various organs, occur, accompanied by a fall of the blood pressure [K'lebs), indicating initial 
 stimulation and subsequent paralysis of the vaso-motor centre. This also explains the variations in 
 the temperature and the occasional occurrence of sugar in the urine after poisoning with CO. After 
 
42 DECOMPOSITION OF HEMOGLOBIN. 
 
 death, the blood vessels are found to be filled with fluid blood of an exquisitely bright cherry-red 
 color, while all the muscles and viscera and exposed parts of the body (such as the lips) have the 
 same color. The brain is soft arid friable, there are catarrh of the respiratory organs and degenera- 
 tion of the muscles, and great congestion and degeneration of the liver, kidneys and spleen. The 
 spots of lividity, post-mortem, are bright red. After recovery from poisoning with CO there may 
 be paraplegia and (although more rarely) disturbances of the cerebral activity. The poisonous 
 action of the vapois of combustion was known to Aristotle. 
 
 17. OTHER COMPOUNDS OF H/EMOGLOBIN. — 4. Nitric 
 Oxide Haemoglobin (NO-Hb) is formed when NO is brought into contact 
 with Hb {L. Hermann). 
 
 As NO has a great affinity for O, red fumes of nitrogen peroxide (N0 2 ) being formed whenever 
 the two gases meet, it is clear that, in order to prepare NO-HB, the must first be removed. This 
 may be done by passing H through it [or ammonia may be added to the blood, and a stream of 
 NO passed through it; the ammonia combines with all the acid formed by the union of the NO with 
 the of the blood]. NO-Hb is a more stable chemical compound than CO-Hb, which, as we have 
 seen, is, again, more stable than 2 Hb. It has a bluish-violet tint, and also gives two absorption 
 bands in the spectrum similar to those of the other two compounds, but not so intense. These 
 bands are not abolished by the action of reducing agents. 
 
 The three compounds of Hb, with O, CO and NO, are crystalline, like Hb; 
 they are isomorphous, and their solutions are not dichroic. All three gases unite 
 in equal volumes with Hb (Preyer, L. Hermann). If O be conducted through 
 a concentrated solution of Hb devoid of gases, a crystalline mass of 2 Hb is 
 thereby readily formed. 
 
 [Nitrites, e.g., amyl, added to fresh blood, give it a chocolate color, and its spectrum is that of 
 methsemoglobin. The compound so formed, however, is less stable than that with CO, for the 
 decomposition products formed in the blood during asphyxia can reduce the former but not the latter 
 compound.] 
 
 5. Cyanogen, CNH (ffoppe-Seyler), and acetylene, C 2 H 4 {Bistrow and Liebreich), form 
 easily decomposable compounds with Hb. The former occurs in poisoning with hydrocyanic acid, 
 and has a spectrum identical with that of 2 Hb, and, like 2 Hb, it is reduced by special agents. 
 [The existence of these compounds is, however, highly doubtful [Gamgee).~\ 
 
 18. DECOMPOSITION OF HEMOGLOBIN.— In solution and in the dry state, Hb 
 gradually becomes decomposed, whereby the iron-containing pigment hsematin, along with certain 
 by-products, formic, lactic and butyric acids, are formed. 
 
 Haemoglobin, however, may be decomposed at once into (1) a body contain- 
 ing iron, hcematin, and (2) a colorless proteid closely related to globulin; by {a) 
 the addition of all acids, even by C0 2 in the presence of plenty of water : (b) 
 strong alkalies ; (/) all reagents which coagulate albumin, and by heat at 7o°-8o° 
 C. ; (d) by ozone. 
 
 (A) Hsematin (Qs, H, , N 8 , Fe 2 , Oi ) is a bluish-black, amorphous body, 
 which forms about 4 per cent, of haemoglobin (dog). It is insoluble in water, 
 alcohol and ether ; soluble in dilute alkalies and acids and in acidulated ether and 
 alcohol. 
 
 Haemocbromogen. — When Hb containing O is decomposed, hsematin is formed at once ; while 
 Hb free from O, on being decomposed, forms, first, a purplish-red body, Hcemochromogen (C S4 ,H 6 , 
 N 4 ,FeO s ), which contains less O, and is a precursor of hsematin. In the presence of O it becomes 
 oxidized and passes into hsematin. In solution, it gives the spectrum shown in Fig. 14, 7 {Hoppe- 
 Seyler). 
 
 Haemato- Porphyrin. — Dilute acids in an alkaline solution deprive hsemochromogen of its iron, 
 and hcemato-porphyrin, a substance which remains stable in contact with air, is produced. It may 
 also be produced from hsematin by the action of acids, so that hsematin is an oxidation stage of 
 haemocbromogen. The following derivatives are known : — 
 
 (a) Haematin in Acid Solution — Lecanu extracted it from dry blood corpuscles by using 
 alcohol containing sulphuric and tartaric acids. If acetic acid be added to a solution of Hb, a 
 mahogany-brown fluid is obtained, containing hcematin in acid solution, which gives a spectrum 
 with four absorption bands in the yellow and green (Fig. Wr-5^. ) 1(1, K~ 
 
 (b) Hsematin in Alkaline Solution. — If this solution be treated with excess of ammonia, 
 hamatin in alkaline solution is formed, which gives one absorption band on the boundary line 
 between red and yellow (Fig. 14, 6). 
 
 (c) Reduced Hsematin. — Reducing agents cause this band to disappear, and produce in the 
 yellow two broad bands, which are due to the presence of " reduced hcematin" (Fig. 14, 7). 
 
HyEMIN AND BLOOD TESTS. 43 
 
 Action of C0 2 . — If C0 2 be passed through a solution of oxyhemoglobin for a considerable 
 time, reduced Hb is first formed ; but if the process be prolonged the Hb is decomposed, a precipi- 
 tate of globulin is thrown down, and an absorption band, similar to that obtained when Hb is 
 decomposed with acids, is observed (see p. 42). 
 
 According to Zinoffsky's analysis there are exactly two atoms of S to each atom of Fe in Hb. 
 
 When haemoglobin is extravasated into the subcutaneous tissue, it becomes so altered that ulti- 
 mately hydrated oxide of iron appears in its place. 
 
 19. HiEMIN AND BLOOD TESTS.— In 1853 Teichmann prepared 
 crystals from blood, which Hoppe-Seyler showed to be chloride of hcemalin or 
 hydrochlorate of hsematin. The presence of these crystals is used as a test for 
 blood stains or blood in solution. These crystals of hsemin (Fig. 15) are prepared 
 by adding a small crystal of common salt to dry blood on a glass slide, and then 
 an excess of glacial acetic acid ; the whole is gently heated until bubbles of gas 
 are given off. On allowing the preparation to cool, the characteristic hasmin 
 crystals are obtained (Hsematin -f- 2HCI). 
 
 Characters. — When well formed, the crystals are small, microscopic, rhombic 
 plates, or rhombic rods ; sometimes they are single — at other times they are aggre- 
 gated in groups, often crossing each other. Some kinds of blood (ox and pig) 
 yield very irregular, scarcely crystalline, masses. The crystalline forms of haemin 
 are identical in all the different kinds of blood that have been examined (Jahnke, 
 Hogyes). They are doubly refractive and pleo-chromatic ; by transmitted light they 
 
 Fig. 15. Fig. 16. 
 
 '/*< 
 
 V\S 
 
 ~x V 
 
 ' ' ' !;K I * , » x ' 
 
 Hsemin crystals of various forms. ' Hasmin crystals prepared from 
 
 traces of blood. 
 
 are mahogany brown, and by reflected light bluish black, glancing like steel. 
 They give a brown streak on porcelain. 
 
 (1) Preparation from Dry Blood Stains. — Place a few particles of the 
 blood stain on a glass slide, add two to three drops of glacial acetic acid and a 
 small crystal of common salt ; cover with a cover glass, and heat gently over the 
 flame of a spirit lamp until bubbles of gas are given off. On cooling, the crystals 
 appear in the preparation (Fig. 16). 
 
 (2) From Stains on Porous Bodies. — The stained object (cloth, wood, 
 blotting paper, earth) is extracted with a small quantity of dilute caustic potash, 
 and afterward with water in a watch glass. Both solutions are carefully filtered, 
 and tannic acid and glacial acetic acid are added until an acid reaction is obtained. 
 The dark precipitate which is formed is collected on a filter and washed. A small 
 part of it is placed on a microscope slide, a granule of common salt is added, and 
 the whole dried ; the dry stain is treated as in (1) (Struwe.) 
 
 (3) From Fluid Blood. — Dry the blood slowly at a low temperature, and 
 proceed as in (1). 
 
 (4) From very Dilute Solutions of Haemoglobin. — (a) Struwe's 
 Method. — Add to the fluid, ammonia, tannic acid, and afterward glacial acetic 
 acid, until it is acid ; soon a black precipitate of tannate of hsematin is thrown 
 
44 . H^MATOIDIN. 
 
 down. This is isolated, washed, dried, and treated as in (i), but instead of NaCl 
 a granule of ammonium chloride is added. 
 
 (d) Guning and van Geuns recommend the addition of zinc acetate, which gives a reddish pre- 
 cipitate; this precipitate is to be treated as in (i). 
 
 Hsemin crystals may sometimes be prepared from putrefying or lake-colored 
 blood, but they are very small, and here the test often fails. When mixed with 
 iron rust, as on iron weapons, the blood crystals are generally not formed. In 
 such cases, scrape off the stains and boil them with dilute caustic potash. If blood 
 be present, the dissolved hsematin forms a fluid, which in a thin layer is green ; in 
 a thick layer, red (H. Rose). 
 
 Haemin crystals have been prepared from all classes of vertebrates and from the blood of the 
 earthworm. 
 
 Chemical Characters. — They are insoluble in water, alcohol, ether, chloroform ; but concen- 
 trated H 2 S0 4 dissolves them, expelling the HC1, and giving a violet red color. Ammonia also dis- 
 solves them, and if the resulting solution be evaporated, heated to 130° C, and treated with boiling 
 water (which extracts the ammonium chloride), pure htemalin is obtained (Hoppe-Seyler) as a bluish- 
 black substance, which on being pounded forms a brown and amorphous powder. Its solutions in 
 caustic alkalies are dichroic ; in reflected light brownish red ; in transmitted light, in a thick stratum, 
 red — in a thin one, olive green. The acid solutions are monochromatic and brown. 
 
 It is important to note that an alcoholic solution of hsematin, when reduced by 
 tin and hydrochloric acid, yields urobilin (Hoppe-Seyler, Nencki, and Sieber) 
 (compare Bile). 
 
 20. H^EMATOIDIN. — Virchow discovered this important derivative from 
 haemoglobin. It occurs in the body wherever blood stagnates outside the 
 circulation, and becomes decomposed — as when blood is extravasated into 
 
 ^ the tissues — e. g., the brain — in solidified blood plugs 
 
 (thrombus); invariably in the Graafian follicles. It 
 contains no iron (C 32 , H 36 , N 4 , O s ), and crystallizes in 
 clinorhombic prisms (Fig. 17) of a yellowish brown 
 color. It is soluble in water, alkalies, carbon disul- 
 phide, benzol, and chloroform. Very probably it is 
 identical with one of the bile pigments — bilirubin 
 (Valenteiner). [When acted upon by impure nitric 
 acid (Gmelin's reaction), it gives the same play of 
 
 Haanatoidin crystals. Colors as bile.] 
 
 Pathological. — In cases where a large amount of blood has undergone solution within the blood 
 vessels (as by injecting foreign blood), haematoidin crystals have been found in the urine (v. Reckling- 
 hausen, Landois). For their occurrence in urine, in jaundice (§ 180), and in the sputum (§ 138). 
 
 21. (B.) THE COLORLESS PROTEID OF HAEMOGLOBIN. 
 
 — It is closely related to globulin ; but, while the latter is precipitated by all 
 acids, even by C0 2 , and re-dissolved on passing O through it, the proteid of 
 haemoglobin, on the other hand, is not dissolved after precipitation on passing 
 through it a stream of O. 
 
 As crystals of hsemoglobin can be decolorized under special circumstances, it is probable that 
 these owe their crystalline form to the proteid which they contain. Landois placed crystals of 
 haemoglobin along with alcohol in a dialvser, putting ether acidulated with sulphuric acid outside, 
 and thereby obtained colorless crystals. [If frogs' blood be sealed up on a microscopic slide, along 
 with a few drops of water, for several days, long, colorless, acicular crystals are developed in it 
 [Stirling and Brito).'] 
 
 22. II. PROTEIDS OF THE STROMA.— Dry, red, human blood 
 corpuscles contain from 5. 10-12. 24 per cent, of these proteids ; but little is known 
 about them (Jtidell). One of them is globulin, which is combined with a body 
 resembling nuclein ( Wboldridge), and traces of a diastatic ferment (v. WitticK). 
 The stroma tends to form masses which resemble fibrin (Landois). 
 
 L. Brunton found a body resembling mucin in the nuclei of red blood corpuscles, and Miescher 
 detected nuclein (\ 250, 2). 
 
CHEMICAL COMPOSITION OF THE COLORLESS CORPUSCLES. 
 
 45 
 
 23. THE OTHER CONSTITUENTS OF RED BLOOD COR- 
 PUSCLES. — III. Lecithin (0.35-0.72 per cent.) in dry blood corpuscles 
 
 \Judell), (§ 250, 2). 
 
 It is regarded as a glycerophosphate of neurin, in which, in the radical of glycero-phosphoric 
 acid, two atoms of H are replaced by two of the radical of stearic acid. By gentle heat glycero- 
 phosphoric acid is split up into glycerine and phosphoric acid ({! 250). 
 
 Cholesterin (0.25 per cent.) (§ 250, III), no Fats. 
 
 These substances are obtained by extracting old stromata or isolated blood corpuscles with ether. 
 When the ether evaporates, the characteristic globular forms ("myelin-forms") of lecithin and 
 crystals of cholesterin are recognized. The amount of lecithin may be determined from the 
 amount of phosphorus in the ethereal extract. 
 
 IV. Water (681.63 per 1000 — C. Schmidt}. 
 
 V. Salts (7.28 per 1000 — C. Schmidt), chiefly compounds of potash and phos- 
 phoric acid ; the phosphoric acid is derived only from the burned lecithin ; while 
 the greater part of the sulphuric acid in the analysis is derived from the burning 
 of the haemoglohin. Z- 
 
 Analysis of Blood.— 1000 parts, by weight, of horse's blood contain : — 
 344.18 blood corpuscles (containing about 128 per cent, of solids). 
 655.82 plasma (containing about 10 per cent, of solids). 
 
 1000 parts, by weight; of MOIST BLOOD CORPUSCLES contain: — 
 
 Solids 367.9 (pig); 400.1 (ox). 
 
 Water 632.1 " 599.9 •' 
 
 The solids are : — 
 
 Pig. Ox. 
 
 Haemoglobin 261 280.5 
 
 Albumin 86.1 107 
 
 Lecithin, Cholesterin and other Organic 1 
 
 Bodies ) I2 '° ' 5 
 
 Inorganic Salts 8.9 4.8 
 
 ' Potash 5.543 0.747 
 
 Magnesia 0.158 0.017 
 
 Including • Chlorine 1.504 1.635 
 
 Phosphoric Acid 2.067 °7°3 
 
 Soda o 2.093 (Bunge). 
 
 [An approximate estimate of the composition of human blood is given in the 
 following table : — 
 
 Composition of Human Blood as a Whole. 
 
 Water 7S0 
 
 Solids — of these — 
 
 Corpuscles 134 
 
 Serum Albumin 1 
 
 Serum Globulin / ' 
 
 Fibrin of Clot (? Fibrinogen) 2.2 
 
 Inorganic Salts (of serum) 6.0 
 
 Extractives 6.4 
 
 Fatty matters 1.4 
 
 Gases, O, C0 2 , N.] 
 
 24. CHEMICAL COMPOSITION OF THE COLORLESS COR- 
 PUSCLES. — Investigations have been made on pus cells, which closely resemble 
 colorless blood corpuscles. They contain several proteids ; alkali albuminate, a 
 proteid which coagulates at 48 C. , and another resembling myosin, para- 
 globulin, peptone, and a coagulating ferment ; nudein in the nuclei (Miescher) 
 (§ 250, 2); perhaps also glycogen (§ 252) (Salomon), lecithin, cerebrin, cholesterin, 
 and fat. 
 
 100 parts, by weight, of dry pus contain — 
 
 Earthy Phosphates 0.416 
 
 Sodic Phosphate 0.606 
 
 Potash, 0.201 
 
 Sodic Chloride, 0.143 
 
46 
 
 PREPARATION OF PLASMA. 
 
 25. BLOOD PLASMA AND ITS RELATION TO SERUM.— 
 
 The unaltered fluid in which the blood corpuscles float is called plasma, or 
 liquor sanguinis. This fluid, however, after blood is withdrawn from the 
 vessels rapidly undergoes a change, owing to the formation of a solid fibrous 
 substance — fibrin. After this occurs, the new fluid which remains no longer 
 coagulates spontaneously (it is plasma, minus the fibrin factors), and is called 
 serum. Apart from the presence of the fibrin factors, the chemical composition 
 of plasma and serum are the same. 
 
 [When blood coagulates, the following table, I, shows what takes place, while the second table, II, 
 shows what occurs when it is beaten : — 
 
 Coagulation. 
 Blood. 
 
 Plasma. 
 
 I 
 
 Corpuscles. 
 
 I 
 Serum. 
 
 I 
 
 Fibrin-factors. 
 
 I 
 
 Blood clot 
 
 II. 
 
 When beaten. 
 Blood. 
 
 Plasma. 
 
 Corpuscles. 
 
 1 I 
 
 Fibrin-factors. Serum. 
 
 Fibrin. 
 
 Defibrinated Blood. 
 
 The serum, however, still contains a portion of the fibrin ferment, and also some 
 of the fibrinoplastin or fibrinoplastic substance. Plasma is a clear, transparent, 
 slightly thickish fluid, which, in most animals (rabbit, ox, cat, dog), is almost 
 colorless ; in man it is yellow, and in the horse citron-yellow.] 
 
 26. PREPARATION OF PLASMA.— (A) Without Admixture.— 
 
 Taking advantage of the fact that plasma, when cooled to 0° outside the body, 
 does not coagulate for a considerable time, Briicke prepares the plasma thus : 
 Selecting the blood of the horse (because it coagulates slowly, and its corpuscles 
 sink rapidly to the bottom), he receives it, as it flows from an artery, in a tall, 
 narrow glass, placed in a freezing mixture, and cooled to o°. The blood remains 
 fluid, and the colored corpuscles subsiding in a few hours, the plasma remains 
 above as a clear layer, which can be removed with a cooled pipette. If this plasma 
 be then passed through a cooled filter, it is robbed of all its colorless corpuscles. 
 [Burdon-Sanderson uses a vessel consisting of three compartments — the outer and 
 inner contain ice, while the blood of the horse is caught in the central compart- 
 ment, which does not exceed half an inch in diameter.] 
 
 The quantity of plasma may be roughly (but only roughly) estimated by using a 
 tall, graduated measuring glass. If the plasma be warmed, it soon coagulates 
 (owing to the formation of the fibrin), and passes into a trembling jelly. If, how- 
 ever, it be beaten with a glass rod, the fibrin is obtained as a white, stringy 
 mass, adhering to the rod. The quantity of fibrin in a given volume of plasma, 
 is about 0.7-1 per cent., although it varies much in different cases. 
 
 (B) With Admixture. — Blood flowing from an artery is caught in a tall, 
 graduated measure containing \ of its volume of a concentrated solution of sodic 
 sulphate (Hewsori) — or in a 25 per cent, solution of magnesic sulphate (1 vol. to 
 4 vols, blood — Semmer) — or 1 vol. blood with 2 vols, of a 4 per cent, solution of 
 monophosphate of potash (Masia). When the blood is mixed with these fluids 
 and put in a cool place, the corpuscles subside, and the clear stratum of plasma 
 mixed with the salts may be removed with a pipette. If the salts be removed by 
 dialysis, coagulation occurs ; or it may be caused by the addition of water (/oh. 
 Muller). Blood which is mixed with a 4 per cent, solution of common salt does 
 not coagulate, so that it also may be used for the preparation of plasma. [For 
 frogs' blood Johannes Muller used a y 2 per cent, solution of cane sugar, which 
 
FIBRIN — COAGULATION OF THE BLOOD. 47 
 
 permits the corpuscles to be separated from the plasma by filtration. The plasma 
 mixed with the sugar coagulates in a short time.] 
 
 27. FIBRIN — COAGULATION OF THE BLOOD. — General 
 Characters. — Fibrin is that substance which, becoming solid in shed blood, in 
 plasma and in lymph causes coagulation. In these fluids, when left to themselves, 
 fibrin is formed, consisting of innumerable, excessively delicate, closely packed, 
 microscopic, doubly refractive {Hermann) fibrils (Fig. 7, E). These fibrils en- 
 tangle the blood corpuscles as in a spider's web, and form with them a jelly-like, 
 solid mass, called the blood clot or placenta sanguinis. At first the clot is 
 very soft, and after the first 2 to 15 minutes a few fibres may be found on its 
 surface ; these may be removed with a needle, while the interior of the clot is 
 still fluid. The fibres ultimately extend throughout the entire mass, which, in 
 this stage, has been called cruor. After from 12 to 15 hours the fibrin contracts, 
 or, at least, shrinks more and more closely round the corpuscles, and a fairly 
 solid, trembling, jelly-like clot, which can be cut with a knife, is formed. During 
 this time the clot has expressed from its substance a fluid — the blood serum. 
 The clot takes the shape of the vessel in which the blood coagulates. Fibrin may 
 be obtained by washing away the corpuscles from the clot with a stream of water. 
 
 Crusta Phlogistica. — If the corpuscles subside very rapidly, and if the blood 
 coagulates slowly, the upper stratum of the clot is not red, but only yellowish, on 
 account of the absence of colored corpuscles. This is regularly the case in horse's 
 blood, and in human blood it is observed especially in inflammations ; hence this 
 layer has been called crusta phlogistica. Such blood contains more fibrin, 
 and so coagulates more slowly. 
 
 The crusta is formed under other circumstances, but the cause of its formation is not always 
 clear, e.g., with increased sp. gr. of the corpuscles, or diminished sp. gr. of the plasma (as in hydrsemia 
 and chlorosis), whereby the corpuscles sink more rapidly, and also during pregnancy. The taller 
 and narrower the glass, the thicker is the crusta (compare \ 41). The upper end of the clot, where 
 there are few corpuscles, shrinks more, and is, therefore, smaller than the rest of the clot. This 
 upper, lighter-colored layer is called the " buffy" coat ; this, however, gradually passes, both as to 
 size and color, into the normal dark-colored clot. [Sometimes the upper surface of the clot is 
 concave or " cupped." The older physicians used to attribute great importance to this condition, 
 and also to the occurrence of the crusta phlogistica, or buffy coat.] 
 
 Defibrinated Blood. — If freshly-shed blood be beaten or whipped with a 
 glass rod or with a bundle of twigs, fibrin is deposited on the rod of twigs in the 
 form of a solid, fibrous, yellowish-white, elastic mass, and the blood which remains 
 is called " defibrinated blood" (p. 46). [The twigs and fibrin must be washed in 
 a stream of water, to remove adhering corpuscles.] 
 
 Coagulation of Plasma. — Plasma shows phenomena exactly analogous, save 
 that there is no well-defined clot, owing to the absence of the resisting corpuscles ; 
 there is, however, always a soft, trembling jelly formed when plasma coagulates. 
 [In Hewson's experiment on the blood of a horse tied in a vein, he found that 
 the plasma coagulated — fibrin being formed, so that he showed coagulation to be 
 due to changes in the plasma itself (§ 29).] 
 
 Properties of Fibrin. — Although the fibrin appears voluminous, it only occurs 
 to the extent of 0.2 per cent. (o. 1 to 0.3 per cent.) in the blood. The amount 
 varies considerably in two samples of the same blood (Sig. Mayer). It is insol- 
 uble in water and ether ; alcohol shrivels it by extracting water ; dilute hydro- 
 chloric acid (o. 1 per cent.) causes it to swell up and become clear, and changes 
 it into syntonin or acid albumin (§ 249, III). When fresh, it has a grayish- 
 yellow, fibrous appearance and is elastic ; when dried, it is horny, transparent, 
 brittle and friable. 
 
 When fresh, it dissolves in 6 to 8 per cent, solutions of sodium nitrate or sulphate, in dilute alka- 
 lies and in ammonia, thus forming alkali albuminate. Heat does not coagulate these solutions. 
 Hydric peroxide is rapidly decomposed by fibrin into water and O ( Thlnard). Fibrin which has 
 been exposed to the air for a long time is no longer soluble in solution of potassic nitrate, but in 
 
48 GENERAL PHENOMENA OF COAGULATION. 
 
 neurin {Mauthner). During putrefaction, it passes into solution, albumen being formed [J. v. Liebig) . 
 Fibrin contains iron, calcic and magnesic phosphates, whose origin is unknown. 
 
 Time for Coagulation. — According to H. Nasse, the first appearance of a coagulum occurs in 
 man's blood after 3 minutes 45 seconds, in women's blood after 2 minutes 20 seconds. Age has no 
 effect; withdrawal of food accelerates coagulation (A. Vierordt). 
 
 28. GENERAL PHENOMENA OF COAGULATION.— I. Blood 
 which is in direct contact with the living and unaltered blood vessels 
 does not coagulate (Thackrah, 1819). — [Hewson (1772) found that when he 
 tied the jugular vein of a horse in two places, and excised it (Fig. 18), the blood 
 did not coagulate for a long time.] This important fact was confirmed by Briicke 
 (1857), who filled the heart of a tortoise with blood which had stood fifteen 
 minutes exposed to the air at o°, and kept it in a moist chamber. The blood 
 was still fluid at the end of syi hours, while the heart itself still continued to 
 beat. He observed that at o° the blood was uncoagulated in the contracting 
 heart of a tortoise after eight days. Blood inside a contracting frog's heart 
 preserved under mercury does not coagulate. If the wall of the vessel be altered 
 by pathological processes {e.g., if the intima becomes rough and uneven, or 
 undergoes inflammatory change), coagulation is apt to occur at these places. 
 Blood rapidly coagulates in a dead heart, or in blood vessels (but not in capilla- 
 ries) or other canals {e.g., the ureter) {Virchow). If blood stagnates in a living 
 vessel, coagulation begins in the central axis, because here there is no contact 
 with the wall of the living blood vessel. 
 
 II. Conditions which Hinder or Delay Coagulation. — {a) The addition 
 of small quantities of alkalies and ammonia, or of concentrated solutions of neutral 
 salts of the alkalies and earths (alkaline chlorides, sulphates, phosphates, nitrates, 
 carbonates). Magnesic sulphate acts most favorably in delaying coagulation (1 
 vol. solution of 28 per cent, to 3^ vols, blood of the horse). 
 
 {b) The precipitation of the fibrinoplastin by adding weak acids, or by C0 2 . 
 
 By the addition of acetic acid until the reaction is acid, the coagulation is completely arrested. 
 A large amount of CO z delays it, and hence venous blood coagulates more slowly than arterial. 
 Hence, also, the blood of suffocated persons remains fluid. 
 
 {c) The addition of egg albumin, syrup, glycerine and much water. If un- 
 coagulated blood be brought into contact with a layer of already-formed fibrin, 
 coagulation occurs later. 
 
 (d) By cold at o° coagulation may be delayed for one hour {J. Davy). If 
 blood is frozen at once, after thawing, it is still fluid, and then coagulates {Hew- 
 son). When shed blood is under high pressure it coagulates slowly {Landois). 
 
 {e) Blood of embryo fowls does not coagulate before the twelfth or fourteenth 
 day of incubation {Boll) ; that of the hepatic vein very slightly ; menstrual blood 
 shows little tendency to coagulate when alkaline mucus from the vagina is mixed 
 with it. If it be rapidly discharged it coagulates in masses. 
 
 (/) Blood rich in fibrin from inflamed parts coagulates slowly, but the clot 
 so formed is firm. 
 
 Haemophilia. — A very slight scratch in some persons may cause very free bleeding. These 
 persons are called colloquially " bleeders," and are said to have haemophilia or the hemorrhagic 
 diathesis. In " bleeders " coagulation seems not to take place, owing to a want of the substances 
 producing fibrin ; hence, in these cases, wounds of vessels are not plugged with fibrin. [A ten- 
 dency to hemorrhage occurs in scurvy, purpura, in some infectious diseases, such as typhus, plague, 
 yellow fever, and in poisoning with phosphorus.] 
 
 Injection of Peptones. — Albertoni observed that if tryptic pancreas ferment (dissolved in gly- 
 cerine) be injected into the blood of an animal, the blood does not coagulate. Schmidt-Mulheim 
 found that after the injection of pure peptone into the blood (0.3 to 0.6 grammes per kilo.) of a dog, 
 the blood lost its power of coagulating. [This occurs in the dog, but not in the rabbit, moreover, 
 although gastric peptone prevents coagulation, trypton or pancreas ferment does not do so {Fano). 
 Peptonized blood, etc., coagulates when it is treated with C0 2 or water.] A substance is formed 
 in the plasma, which prevents coagulation, but which is precipitated by C0 2 . Lymph behaves 
 similarly {Fano). After peptones are injected, there is a great solution of leucocytes in the blood 
 (v. Samson- Himmelstjerna). The secretion of the mouth of the medicinal leech [although its 
 
GENERAL PHENOMENA OF COAGULATION. 49 
 
 action is not due to a ferment (Haycraft)], and snake poison also prevent coagulation {Wall). 
 [Diastatic ferment also prevents coagulation {Salvioli).~\ 
 
 [Blood coagulates more slowly in a smooth than a rough vessel, and also in a shallow vessel than 
 in a deep one.] 
 
 III. Coagulation is accelerated — (a) By contact with Foreign Sub- 
 stances of all kinds ; hence, threads or needles introduced into arteries are 
 rapidly covered with fibrin. Even the introduction of air bubbles into the circu- 
 lation accelerates it, and the pathologically altered wall of a vessel acts like a 
 foreign body. Blood shed from an artery rapidly coagulates on the walls of 
 vessels, on the surfaces exposed freely to air, and on the rods or twigs by which 
 it is beat. The passage through it of indifferent gases, such as N and H, and 
 the addition of H 2 have the same effect. 
 
 (b) Heating from 39° to 55° C. rapidly facilitates coagulation (Hewson). 
 
 (c) Agitation of the blood, as shown by Hewson and Hunter. 
 [(</) The addition of a small quantity of water. 
 
 (*) A watery condition of the blood, but in this case the clot is small and soft. 
 (/) Contact with oxygen.] 
 
 IV. Rapidity of Coagulation. — Among vertebrates, the blood of birds 
 (especially, of the pigeon), coagulates almost momentarily ; in cold-blooded 
 animals coagulation occurs much more slowly, while mammals stand midway, 
 between the two. 
 
 [The blood of a fowl begins to coagulate in ^ to J y^ minute ; that of a pig, sheep, rabbit, in 
 y z to iyi, minute; of a dog, I to 3 minutes; of a horse and ox, 5 to 13 minutes; of man, 3 to 4 
 minutes ; solidification is completed in 9 to II minutes, but rather sooner in the case of women 
 (JVasse).'] The blood of invertebrates, which is usually colorless when it is oxidized (ji 32), forms 
 a srft, whitish clot of fibrin. Even in lymph and chyle, a small soft clot is formed. 
 
 V. When coagulation occurs, the aggregate condition of the fibrin factors is 
 altered, so that heat must be set free {Valentin, 1884, Schiffer, L&pine). The rise 
 in the temperature may be ascertained with a very delicate thermometer. 
 
 VI. In blood shed from an artery, the degree of alkalinity diminishes from the 
 time of its being shed until coagulation is completed (Pfluger and Zuntz). This 
 is probably due to a decomposition in the blood, whereby an acid is developed, 
 which diminishes the alkalinity (p. 17). 
 
 VII. Whether or not electricity is developed is not positively proved. Hermann supposes that 
 the parts already coagulated are negative, while non coagulated parts are positive ; but this has not 
 been clearly shown. 
 
 VIII. During coagulation there is a diminution of the O in the blood, although 
 a similar decrease also occurs in non-coagulated blood. Traces of ammonia are 
 also given off, which Richardson erroneously supposed to be the cause of the 
 coagulation of the blood. 
 
 [This is refuted — (1) by the fact that blood, when collected under mercury (whereby no escape 
 of ammonia is possible), also coagulates; and (2) by the following experiment of Lister: He 
 placed two ligatures on a ve.n containing blood, moistening one-half of the outer surface of the 
 vein with ammonia, leaving the other half intact. The blood coagulated in the first half, and not in 
 the other, owing to the properties of the wall of the vein of the former being altered. Lister also 
 proved that blood will remain fluid for hours in a vein after it has been freely exposed ' to the air, 
 and even after it has been poured in a thin stream from one vein to another.] Neither the decrease 
 of nor the evolution of ammonia seems to have any causal connection with the formation of 
 fibrin. 
 
 Pathological. — When the blood coagulates within the vessels during life, the process is called 
 thrombosis, and the coagulum or plug so formed is termed a thrombus. When a clot of blood or 
 other body is carried by the blood stream to another part of the vascular system where it blocks up a 
 vessel, the plug is called an embolus, and the result embolism. 
 
 29. CAUSE OF THE COAGULATION OF THE BLOOD.— 
 
 Perhaps this subject is best treated historically. 
 
 [Hewson's Experiments (1772). — Hewson tied the jugular vein of a horse between two liga- 
 tures, removed it, and then suspended it by one end (Fig. 18). He found that the blood remained 
 
 4 
 
50 CAUSE OF THE COAGULATION OF THE BLOOD. 
 
 fluid for a long time (48 hours), while the red corpuscles sank (R.C.) and left a clear layer of plasma 
 on the surface (P). When he drew off some of this clear plasma it coagu- 
 FlG. 18. lated, thus proving coagulation to be due to changes in the plasma. Lister 
 
 repeated this experiment, and found that even if the upper end of the tube 
 be opened and the bloud freely exposed to the air, coagulation is but slightly 
 hastened. Moreover, he proved that the blood might be poured from one 
 vein into another, just as one would pour fluid from one test-tube into 
 another. In this case there were two test-tubes, i.e., the veins — and 
 although the blood, on being poured from the one to the other, came into 
 contact with the air, it did not coagulate. Hewson, however, found that 
 blood poured from the vein into a glass vessel coagulated, so that, in his 
 opinion, the blood vessels exerted a restraining influence on the coagulation. 
 By cooling the blood and preventing it from coagulating, he proved that 
 coagulation was not due to the loss of heat. Nor could it be a vital act, as 
 sodic sulphate or other neutral salt prevented coagulation indefinitely, but 
 coagulation took place when the blood was diluted with water.] 
 
 [Buchanan's Researches. — The serous sacs of the body contain a 
 fluid which in some respects closely resembles lymph. The pericardium 
 contains pericardial fluid, which in some animals coagulates spontaneously 
 
 Vein of a horse tied be- [e.g., in the rabbit, ox, horse, and sheep), if the fluid be removed immedi- 
 
 pTima'^wf?" 1 white atel y a f ter death - If this be not done tiU several hours a f ter death ' the 
 and RC., red corpuscles', fluid does not coagulate spontaneously. The fluid of the tunica vaginalis 
 of the testis, again, sometimes accumulates to a great extent, and constitutes 
 hydrocele, but this fluid shows no tendency to coagulate spontaneously. Andrew Buchanan found, 
 however, that if to the fluid of ascites, to pleuritic fluid, or to hydrocele fluid, there be added clear 
 blood serum, then coagulation takes place, i.e., two fluids — neither of which shows any tendency 
 by itself to coagulate — form a clot when they are mixed (1831). He also found that if " washed 
 blood clot " (which consists of a mixture of fibrin and colorless corpuscles) be added to hydrocele 
 fluid, coagulation occurred. He compared the action of washed blood clot to the action of rennet 
 in coagulating milk, and he imagined the agents which determined the coagulation to be the colorless 
 corpuscles. Thus, the buffy coat of horses' blood is a powerful agent, and it contains very numerous 
 colorless corpuscles. He finally concluded that some constituent in the plasma, to which he gave the 
 name of a " soluble fibrin," is acted upon by the colorless corpuscles and converted into fibrin. The 
 soluble fibrin of Buchanan is comparable to the fibrinogen in Hammaisten's theory. But Buchanan 
 did not separate the substance.] 
 
 [Denis's Plasmine. — Denis mixed uncoagulated blood with a saturated solution of sodic sul- 
 phate, allowed the corpuscles to subside, and decanted the clear fluid, which was mixed with sodic 
 chloride, until a large amount of precipitate had been obtained. The precipitate, when washed with 
 a saturated solution of sodic chloride, he called plasmine (1859). If plasmine be mixed with 
 water, it coagulates spontaneously, resulting in the formation of fibrin, while another proteid remains 
 in solution. According to the view of Denis, fibrin is produced by the splitting up of plasmine into 
 two bodies — fibrin and an insoluble proteid.] 
 
 [Researches of A. Schmidt (1861). — This observer rediscovered the chief facts already known 
 to Buchanan, viz., that some fluids which do not coagulate spontaneously, clot when mixed with 
 other fluids, which also show no tendency to coagulate spontaneously, e.g., hydrocele fluid and blood 
 serum. He proceeded to isolate from these fluids the bodies which are described as fibrinogen and 
 fibrinoplastin. The bodies so obtained were not pure, but Schmidt supposed that the formation of 
 fibrin was due to the interaction of these two proteids. The reason why hydrocele fluid did not 
 coagulate, he said, was that it contained fibrinogen and no fibrinoplastin, while blood serum con- 
 tained the latter, but not the former. Schmidt afterward discovered that these two substances may be 
 present in a fluid, and yet that coagulation may not occur [e.g., occasionally in hydrocele fluid). He 
 supposed, therefore, that blood or blood serum contained some other constituent necessary for coagu- 
 lation. This he afterward isolated in an impure condition and called fibrin ferment [Gamgee).~\ 
 
 Alexander Schmidt's theory is that fibrin is formed by the coming together of 
 two proteid substances which occur dissolved in the plasma or liquor sanguinis, 
 viz. : (1) Fibrinogen, i.e., the substance which yields the chief mass of the fibrin, 
 and (2) Fibrinoplastic substance or fibrinoplastin, [ = serum globulin (7/4. Weyl 
 and Hoppe-Seyler) or paraglobulin (Kuhne) § 3 2]. In order to determine the 
 coagulation a ferment seems to be necessary, and this is supplied by (3) the 
 Fibrin ferment. 
 
 1. Properties of these Substances. — Fibrinogen and fibrinoplastin are 
 not distinguished from each other by well-marked chemical characters. Still 
 they differ, as follows : — 
 
 {a) Fibrinoplastin is more easily precipitated from its solutions than fibrinogen. 
 
CAUSE OF THE COAGULATION OF THE BLOOD. 51 
 
 (b) It is more readily redissolved when once it is precipitated. 
 
 (/) It forms when precipitated a very light granular powder. 
 
 (d) Fibrinogen adheres as a sticky deposit to the side of the vessel. It coagu- 
 lates at 56° C. 
 
 Both substances closely resemble globulin in their chemical composition 
 (Kiihne called fibrinoplastin paraglobulin), and in their reactions they are not 
 unlike myosin. Like all globulins, they require a trace of common salt for their 
 solution (§ 249). 
 
 On account of their great similarity, both substances are not usually prepared 
 from blood plasma. Fibrinogen is prepared from serous transudations (pericardial, 
 abdominal, or pleuritic fluid, or the fluid of hydrocele), which contain no fibrino- 
 plastin. Fibrinoplastin is 'most readily prepared from serum, in which there is 
 still plenty of fibrinoplastin, but no fibrinogen. 
 
 2. Preparation of Fibrinoplastin, Serum Globulin, or Paraglobu- 
 lin. — (a) Dilute blood serum with twelve times its volume of ice-cold water, and 
 almost neutralize it with acetic acid [add 4 drops of a 25 per cent, solution of 
 acetic acid to every 120 c.c. of diluted serum] ;• or (b) pass a stream of carbon 
 dioxide through the diluted serum, which soon becomes turbid ; and after a time 
 a fine white powder, copious and granular, is precipitated (Schmidt, 1862). 
 
 [(c) The serum may be dialysed for a day ; at the end of this time the contents of the dialyser 
 have become turbid, and when a current of C0 2 is passed through them, a precipitate of fibrino- 
 plastin is obtained.] 
 
 [(</) Method of Hammarsten. — All the fibrinoplastin in serum is not pre- 
 cipitated either by adding acetic acid or by C0 2 . Hammarsten found, however, 
 that if crystals of magnesium sulphate be added to complete saturation, it precipi- 
 tates the whole of the serum globulin, but does not precipitate serum albumin 
 ( Gamgee) ; it seems that in the ox and horse serum globulin is more abundant 
 than serum albumin, while in the dog and rabbit the reverse obtains ; (com- 
 pare § 32).] 
 
 Schmidt found that 100 c.c. of the serum of the ox blood yielded 0.7 to 0.8 grms. ; horse's 
 serum, 0.3 to 0.56 grms. of dry fibrinoplastin. Fibrinoplastin occurs not only in serum, but 
 also in red blood corpuscles, in the fluids of connective tissue, and in the juices of the cornea. 
 
 3. Preparation of Fibrinogen. — This is best prepared from hydrocele 
 fluid, although it may also be obtained from the fluids of serous cavities, e.g., the 
 pleura, pericardium, or peritoneum. It does not exist in blood serum, although 
 it does exist in blood plasma, lymph, and chyle, from which it may be obtained 
 by a stream of C0 2 , after the paraglobulin is precipitated, (a) Dilute hydrocele 
 fluid with ten to fifteen times its volume of water, and pass a stream of C0 2 
 through it ; or (b) carefully neutralize it by adding acetic acid, (c) Add powdered 
 common salt to saturation to a serous transudation, when a sticky, glutinous (not 
 very abundant) precipitate of fibrinogen is obtained. 
 
 [Hammarsten and Eichwald find that, although paraglobulin and fibrinogen are 
 soluble in solutions of common salt (containing 5 to 8 per cent, of the salt), a 
 saline solution of 12 to 16 per cent, is required to precipitate the fibrinogen, 
 leaving still in solution paraglobulin, which is not precipitated until the amount 
 of salt exceeds 20 per cent. (Gamgee).'} 
 
 Hammarsten found that it may be prepared from blood (of the horse) by first 
 precipitating all the serum globulin or fibrinoplastin with crystals of magnesium 
 sulphate, and subsequent filtration, which removes the corpuscles ; a clear, salted 
 plasma is thus obtained. If to the filtrate a saturated solution of common salt be 
 added, a turbid, flaky, impure precipitate of fibrinogen is obtained. This may be 
 dissolved in dilute common salt, and again precipitated by a saturated solution 
 ofNaCl. 
 
 Properties of the Fibrin Factors. — They are insoluble in pure water, but 
 dissolve in water containing O in solution. Both are soluble in very dilute alka- 
 
52 THE FIBRIN FACTORS. 
 
 lies, e.g., caustic soda, and are precipitated from this solution by C0 2 . They are 
 soluble in dilute common salt — like all globulins — but if a certain amount of 
 common salt be added in excess they are precipitated. Very dilute hydrochloric 
 acid dissolves them, but after several hours they become changed into a body 
 resembling syntonin or acid albumin (§ 249, III). 
 
 Fibrinogen dissolved in a weak solution of common salt (1 to 5 per cent.) is 
 reprecipitated on adding water, so that it resembles fibrin. Its solution in com- 
 mon salt coagulates at 52° to 55° C. (Hammarsten, Fredtricq). 
 
 [Fr6d6ricq finds that fibrinogen exists as such in the plasma ; it coagulates at 
 56 C, and the plasma thereafter is uncoagulable (Gamgee).~\ 
 
 4. Preparation of the Fibrin Ferment. — Mix blood serum (ox) with 
 twenty times its volume of strong alcohol, and filter off the deposit thereby pro- 
 duced after one month. The deposit on the filter consists of albumin and the 
 ferment ; dry it carefully over sulphuric acid, and reduce to a powder. Triturate 
 one gramme of the powder with 65 c.c. of water for ten minutes, and filter. The 
 ferment is dissolved by the water, and passes through the filter, while the coagu- 
 lated albumin remains behind (Schmidt). 
 
 In the preparation of fibrinoplastin, the ferment is carried down with it mechanically. The 
 ferment seems to be formed first in fluids outside ihe body, very probably by the solution of the 
 colorless corpuscles. More ferment is formed in the blood the longer the interval between its being 
 shed and its coagulation. It is destroyed at 70 C. Blood flowing directly from an artery into 
 alcohol contains no ferment. It is also formed in other protoplasmic parts (Hausehenbach), eg., in 
 dead muscle, brain, suprarenal capsule, spermatozoa, testicle (Foa and Pellacani), and in vegetable 
 micro-organisms [e.g., yeast and protozoa] (Grohmann) [so that it would seem to be a geiieral 
 product of protoplasm]. [As the ferment does not preexist in colorless blood corpuscles, it setms 
 to be formed from some mother substance in them, the blood plasma itself decomposing this sub- 
 stance [Rauschenbach')."\ 
 
 [Gamgee's Method. — Buchanan's " washed blood clot" (p. 50) is digested in an 8 per cent, 
 solution of common salt. The solution so obtained possesses in an intense degree the properties of 
 Schmidt's fibrin ferment.] 
 
 Coagulation Experiments. — According to A. Schmidt, if the pure solutions 
 of (1) fibrinogen, (2) fibrinoplastin, and (3) fibrin ferment be mixed, fibrin is 
 formed. The process goes on best at the temperature of the body ; it is delayed 
 at o° ; and the ferment is destroyed at the boiling point. The presence of O seems 
 necessary for coagulation. The amount of ferment appears to be immaterial; 
 large quantities produce more rapid coagulation, but the amount of fibrin formed 
 is not greater. 
 
 The amount of salts present has a remarkable relation to coagulation. 
 Solutions of the fibrin factors deprived of salts, and redissolved in very dilute 
 caustic soda, when mixed, do not coagulate until sufficient NaCl be added to 
 make a 1 per cent, solution of this salt (Schmidt). 
 
 When blood or blood plasma coagulates, all the fibrinogen is used up, so that 
 the serum contains only fibrinoplastin and fibrin ferment ; hence, the addition 
 of hydrocele fluid (which contains fibrinogen) to serum causes coagulation. 
 
 According to Hammarsten, fibrin is formed when the ferment is added to a 
 solution of fibrinogen. 
 
 [Foa and Pellacani find that a filtered watery extract of fresh brain, cap»u'.e of the kidneys, testes, 
 and some other tissues, when injected into the blood vessels of a rabbit, causes coagulation of the 
 blood in the pulmonary circulation and the heart, death being caused by the action of a substance 
 identical with the fibrin ferment.] 
 
 [Hammarsten's Theory of Coagulation. — Hammersten's researches led him to believe that 
 fibrinoplastin is quite unnecessary for coagulation. According to him, fibrin is formed from one 
 body, viz., fibrinogen, which is present in plasma when it is acted upon by the fibrin ferment ; the 
 latter, however, has not been obtained in a pure state. Neither he nor Schmidt asserts that this 
 body is of the nature of a ferment, although they use the term for convenience. It is quite certain 
 that fibrin may be formed when no fibrinoplastin is present, coagulation being caused by the addi- 
 tion of calcic chloride or casein prepared in a special way. But, whtther one or two proteids be 
 required, in all cases it is clear that a certain quantity of salts, especially of NaCl, is necessary.] 
 
SOURCE OF THE FIBRIN FACTORS. 53 
 
 [The main drift of the foregoing evidence points to the presence of one proteid 
 —fibrinogen — in the plasma, which, under certain circumstances, yields fibrin. In 
 shed blood this act seems to be determined by a ferment, perhaps derived from 
 the disintegration of colorless corpuscles.] 
 
 [Theory of Wooldridge. — Wooldridge attributes great importance to lecithin. In shed blood 
 the coagulation is brought about by the interaction of the plasma and the colorless corpuscles. If 
 lecithin (which is present in considerable amount in the colorless corpuscles) diffuses into the blood, 
 coagulation takes place. When peptone is injected into the blood of the dog, the blood does not 
 clot ; this is due, according to Wooldridge, to the peptone " preventing the interaction of leucocytes 
 and plasma." If, however, the corpuscular elements are removed by the centrifugal machine, the 
 peptone plasma can be made to clot. He also believes that fibrin ferment does not preexist in 
 normal plasma, but that " it may make its appearance in that plasma in the absence of all cellular 
 elements, and must, therefore, come from some constituent or constituents of the plasma itself."] 
 
 30. SOURCE OF THE FIBRIN FACTORS.— Al. Schmidt maintains 
 that all the three substances out of which fibrin is said to be formed arise from 
 the breaking up of colorless blood corpuscles. In the blood of man and mam- 
 mals fibrinogen exists dissolved in the circulating blood as a dissolution product 
 of the retrogressive changes of the white corpuscles. Plasma contains dissolved 
 fibrinogen and serum albumin. The circulating blood is very rich in colorless 
 blood corpuscles — much richer, indeed, than was formerly supposed {Schmidt, 
 Landois). As soon as blood is shed from an artery, enormous numbers of the 
 colorless corpuscles are dissolved (Mantegazzd) — according to Alex. Schmidt, 71.7 
 per cent, (horse). First the body of the cell disappears, and then the nucleus 
 (Hlavd). The products of their dissolution are dissolved in the plasma, and one 
 of these products is fibrinoplastin. At the same time the fibrin ferment is also 
 produced, so that it would seem not to exist in the intact blood corpuscles. 
 Fibrinoplastin and fibrin ferment are also produced by the " transition forms" 
 of blood corpuscles, i.e., those forms which are intermediate between the red and 
 the white corpuscles. They seem to break up immediately after blood is shed. 
 The blood plates (p. 33) are also, probably, sources of these substances. 
 
 In amphibians and birds the red nucleated corpuscles rapidly break up after blood is shed, and 
 yield the substance or substances which form fibrin. Al. Schmidt convinced himself that in these 
 animals fibrinogen is originally, also, a constituent of the blood corpuscles. 
 
 It is clear, therefore, according to Schmidt's view, that as soon as the blood 
 corpuscles, white or red, are dissolved, the fibrin factors pass into solution, and 
 the formation of fibrin by the interaction of the three substances will ensue. 
 
 If a large number of leucocytes be introduced into the circulation of an animal, 
 the leucocytes are dissolved in great numbers in the blood, so that death takes 
 place by diffuse coagulation. Should the animal survive the immediate danger of 
 death, the blood, owing to the want of leucocytes, is completely incapable of 
 coagulating {GrotK). 
 
 [It is worthy of remark to recall the conclusion arrived at by And.. Buchanan, viz., that the 
 potential element of his " washed blood clot " resided in the colorless corpuscles, " primary cells or 
 vesicles." He, like Schmidt, found that the buffy coat of horses' blood, which is very rich in white 
 corpuscles, produced coagulation rapidly. Buchanan compared the action of his washed clot to 
 ■ that of rennet in coagulating milk.] 
 
 Pathological — Al. Schmidt and his pupils, Jakowicki and Birk, have shown that some ferment, 
 probably derived from the dissolution of colorless corpuscles, is found in circulating blood, and that 
 it is more abundant in venous than in arterial blood, while it is most abundant in shed blood. It 
 is specially remarkable that in septic fever the amount of ferment in blood may increase to such an 
 extent as to permit the occurrence of spontaneous coagulation (thrombosis), which may even pro- 
 duce death (Arn. Kokler). In febrile cases generally, the amount of ferment is somewhat more 
 abundant (Adelberg and Birk). Af.er the injection of ichor into the blood, an enormous number 
 of colorless corpuscles are dissolved (F. Hoffman). The injection of peptone (Hb) and, to a less 
 degree, of distilled water, is followed by solution of numerous leucocytes. 
 
 There are changes in the blood, constituting true blood diseases, in which the physiological meta- 
 bolism of the colorless corpuscles is enormously increased, so that the metabolic products accumu- 
 late in the blood (Alex. Schmidt). The result of this is spontaneous coagulation within the circu- 
 latory system, and death even may occur ; at the least, there is an increase of temperature. After 
 such a condition, the coagulability of such blood is diminished. 
 
54 CHEMICAL COMPOSITION OF THE PLASMA AND SERUM. 
 
 31. RELATION OF THE RED BLOOD CORPUSCLES TO THE FORMA- 
 TION OF FIBRIN. — After the investigations of several observers had shown that the red blood 
 corpuscles [bird (flbppe-Seyler)~], Horse (Heynsius), frog (A. Schmidt and Semmer) participate in 
 the production of fibrin, Landois observed, in 1874, under the microscope, that the stromata of the 
 red blood corpuscles of the mammals passed into fibrin. If a drop of defibrinated rabbit's blood be 
 placed in serum of frog's blood, without mixing them, the red corpuscles can be seen collecting 
 together ; their surfaces are sticky, and they can only be separated by a certain pressure on the 
 cover glass, whereby some of the new spherical corpuscles are drawn out into threads. The cor- 
 puscles soon become spherical, and those at the margin allow the haemoglobin to escape, when the 
 decolorization progresses, from the margin inward, untii at last there remains a mass of stroma 
 adhering together. The stroma substance is very sticky, but soon the cell contours disappear, and 
 the stromata adhere and form fine fibres. Thus { according to Landois) the formation of fibrin from 
 red blood corpuscles can be traced step by step. The red blood corpuscles of man and animals, 
 when dissolved in the serum of other animals, show much the same phenomena. 
 
 Stroma Fibrin and Plasma Fibrin. — Landois calls fibrin formed direct from stroma, stroma 
 fibrin. Fibrin which is formed in the usual way by the fibrin factors he calls plasma fibrin. The 
 stroma fibrin is closely related chemically to stroma itself; and as yet the two kinds of fibrin have 
 not been sharply distinguished chemically. Substances which rapidly dissolve red corpuscles cause 
 extensive coagulation, e. g., injection of bile or bile falts, or lake-colored blood, into arteries 
 {Naunyn and Francken). After the injection of foreign blood the newly-injected blood often 
 breaks up in the blood vessels of the recipient, while the finer vessels are frequently found plugged 
 with small thrombi (see Transfusion, \ 102). 
 
 Coagulable Fluids. — With regard to coagulability, fluids containing proteids 
 may be classified thus : — 
 
 (1) Those that coagulate spontaneously, i. e., blood, lymph, chyle. 
 
 (2) Those capable of coagulating, e.g., fluids secreted pathologically in serous cavities; for 
 example, hydrocele fluid, which, as usually containing fibrinogen only, does not coagulate sponta- 
 neously, cogaulates on the addition of fibrinoplastin and ferment (or of blood serum in which both 
 occur). 
 
 (3) Those which do not coagulate, e. g., milk or seminal fluid, which do not seem to contain 
 fibrinogen. 
 
 32. CHEMICAL COMPOSITION OF THE PLASMA AND 
 SERUM. — I. Proteids occur to the amount of 8 to 10 per cent, in the plasma. 
 Only 0.2 per cent, of these go to form fibrin. When coagulation has taken 
 place, and after the separation of the fibrin, the plasma becomes converted into 
 serum. The sp. gr. of human serum is 1027 to 1029. It contains several proteids. 
 [According to Hammarsten, human serum contains 9.2075 per cent, of solids — 
 of these, 3.103 = serum globulin, and 4.516 = serum albumin, i. e., in the 
 ratio of 1 : 1.5 n. The total amount of proteids in blood seems to be much 
 more constant than are the relative proportions of serum albumin and serum 
 globulin (SalvioK').'] 
 
 (a) Serum Globulin {Th. Weyl~) or Paraglobulin, 2 to 4 per cent., was 
 formerly believed to occur in much smaller amount than it actually does. Ham- 
 marsten found that if serum be diluted with two volumes of water, and crystals of 
 magnesium sulphate be added to saturation, serum globulin is precipitated, but 
 not serum albumin. In the serum of the horse and ox, serum globulin is more 
 abundant than serum albumin, while in the serum of the rabbit and dog the- 
 reverse is the case. It is soluble in 10 per cent, solution of common salt, and 
 coagulates at 75 C. 
 
 [Serum globulin was carefully described by Panum under the name of " serum casein ;" by Al. 
 Schmidt, as " fibrinoplastic substance ;" and by Kiihne, as " paraglobulin."] 
 
 As already mentioned, it may also be precipitated, in part, by diluting serum with 10 to 15 vols, 
 of water, and passing a stream of C0 2 through it (p. 51). If a trace of acetic acid be added to 
 serum afier the separation of the serum globulin, Kiihne finds that a fine precipitate of what he calls 
 soda albuminate occurs. [It is, however, highly doubtful if an alkali albuminate does occur in the 
 blood. Hammarsten found that C0 2 does not precipitate all the serum globulin, so that it is impos- 
 sible that Kuhne's soda albuminate exists as a distinct substance in serum.] 
 
 According to A. E. P>urckhard, magnesium sulphate not only precipitates serum globulin, but also 
 another proteid substance more closely resembling albumin. During hunger the globulin increases 
 and the albumin diminishes. 
 
PROTEIDS OF THE SERUM. 55 
 
 (£) Serum Albumin. — Its solutions begin to be turbid at 6o° C, and coagu- 
 lation occurs at 73 C, the fluid becoming slightly more alkaline at the same 
 time. The amount is about 3 to 4 per cent. (Fridiricq). If sodium chloride be 
 cautiously added to serum, the coagulating temperature may be lowered to 50° 
 C. It has a rotatory power of — 56 . It is changed into syntonin or acid 
 albumin by the action of dilute HC1, and by dilute alkalies into alkali albuminate. 
 
 [Serum Albumin v. Egg Albumin. — Although serum albumin is closely related to egg albu- 
 min, they differ — (a) as regards their action upon polarized light; (b) the precipitate produced by 
 adding HC1 or HN0 3 is readily soluble in 4 c.c. of the reagent in the case of serum albumin, 
 while the precipitate in egg albumin is dis-solved with very great difficulty; (c) egg albumin, injected 
 into the veins, is excreted in the urine as a foreign body, while serum albumin is not (Slockvis) ; 
 (d) serum albumin is not coagulated by ether, while egg albumin is, if the solution is not alkaline 
 
 (2 249)-] 
 
 [Serum albumin has never been obtained from free salts, even when it is dialysed for a very long 
 
 time, as was maintained by Aronstein, whose results have not been confirmed by Heynsius, Haas, 
 
 Huizinga, Salkowski and others] 
 
 After all the paraglobulin (serum globulin) in serum is precipitated by magnesium sulphate, serum 
 
 albumin still remains in solution. If this solution be heated to 40 or 50° C. a copious precipitate 
 
 of non-coagulated serum albumin is obtained, which is soluble in water. If the serum albumin be 
 
 filtered from the fluid, and if the clear fluid be heated to over 6o° C, Fredericq found that it becomes 
 
 turbid from the precipitation of other proteids ; the amount of these other bodies, however, is small. 
 
 [Proteids of the Serum. — Halliburton has shown, by the method of "frac- 
 tional heat coagulation ' ' (i. e. , ascertaining the temperature at which a proteid is 
 coagulated, filtering the fluid and again heating the filtrate to a higher tempera- 
 ture), that from the same fluid perhaps two or more proteids, all with different 
 temperatures of coagulation, may be obtained. Care must be taken to keep the 
 reaction constant. He finds that serum globulin coagulates at 75 C, while serum 
 albumin in reality consists of three proteids, which coagulate at different tempera- 
 tures ; (a) at 73 , (b) at 77 , and (c) at 84 C] 
 
 [Precipitation by Salts. — Sulphate of magnesia not only precipitates serum 
 globulin but also fibrinogen (Halliburton). The fluid must be shaken for several 
 hours, to get complete saturation. Sodic sulphate, when added to serum deprived 
 of its globulin by MgS0 4 , precipitates serum albumin, but it produces no precipi- 
 tate with pure serum. In this way serum albumin may be obtained in a pure, un- 
 coagulated and still soluble condition. But Halliburton finds that serum globulin 
 is thrown down by sodic nitrate, acetate, or carbonate ; while all the proteids of 
 the serum are precipitated by potassic acetate or phosphate, and the same result is 
 brought about by adding two salts, e. g., MgSO, and Na 2 S0 4 (in this case sodio- 
 magnesic sulphate is formed) ; MgS0 4 and NaN0 3 ; MgS0 4 and KI ; NaCl and 
 NajSOf After serum globulin is thrown down by MgS0 4 , the addition of MgS0 4 
 and Na 2 S0 4 or the double salt, precipitates the serum albumin, which is still 
 soluble in water.] 
 
 [The plasma of invertebrata (decapo 1 crustaceans, some gasteropods, cephalopods, etc.) clots 
 like vertebrate blood, and contains fibrinogen, but it is noteworthy that, in addition, there is found in 
 it a substance corresponding to haemoglobin, and called by Fredericq, Haemocyanin. It exists like 
 Hb in two conditions, one reduced and the other oxyhaemocyanin, the former being colorless, the 
 latter blue. In its general characters it resembles Hb, although it contains copper instead of iron, 
 and gives no absorption bands (Halliburton). In the blood of some decapod crustaceans there is a 
 reddish pigment, Tetronerythrin, which is identical with that in the exoskeleton and hypoderm. 
 It belongs to the group of lipochromes, like some of the pigments of the retina. The haemocyanin 
 is respiratory in function, and it is remarkable that it is contained in the plasma, and not in the 
 formed elements, like the Hb of vertebrates. So that, stated broadly, in these Invertebrates the 
 plasma is both nutritive and respiratory in its functions, while in Vertebrates the red corpuscles 
 chiefly are respiratory and the plasma nutritive (Fridiricq) .] 
 
 II. Fats (0.1 to 0.2 percent.). — Neutral fats (tristearin, tripalmitin, triolein) 
 occur in the blood in the form of small microscopic granules which, after a meal 
 rich in fat (or milk), render the serum quite milky. 
 
 [The amount of fat in the serum of fasting animals is about 0.2 per cent. ; 
 during digestion 0.4 to 0.6 per cent. ; and in dogs fed on a diet rich in fat it may 
 
56 GASES OF THE BLOOD. 
 
 be 1.25 per cent. There are also minute traces of fatty acids (succinic). Rohrig 
 showed that soluble soaps, i. e., alkaline salts of the fatty acids, cannot exist in the 
 blood. Cholesterin may be considered along with the fats. It occurs in 
 considerable amount in nerve tissues, and, like fats, is extracted by ether from the 
 dry residue of blood serum. Hoppe-Seyler found 0.019 t0 °-3 I 4 P er cent, in the 
 serum of the blood of fattened geese. There is no fat in the red blood corpuscles 
 {Hoppe-Seyler). Lecithin (its decomposition products, glycerin -phosphoric acid 
 and protagon) occur in serum and also in the blood corpuscles.] 
 
 III. Traces of Grape Sugar [o. 1 to 0.15 per cent. {Seegeri) more in the hepatic 
 vein (0.23 per cent.)], derived from the liver and muscles, is increased after 
 hemorrhage (§ 175) {Bernard, v. Meting); some glycogen {Pavy), and another 
 reducing fermentative substance also increased by hemorrhage (_/. G- Otf). 
 
 The amount of grape sugar in the blood increases with the absorption of sugar from the intestine, 
 and this increase is most obvious in the blood of the portal and hepatic veins ; there is also a slight 
 increase in the arterial blood, but there it is rapidly changed. The presence of sugar is ascertained 
 by coagulating blood by boiling it with sodium sulphate, pressing out the fluid and testing it for 
 sugar with Fehling's solution (CI. Bernard). Pavy coagulates the blood with alcohol. 
 
 IV. Extractives. — Kreatin, urea (0.016 per cent., increased after food), 
 succinic acid, and uric acid (more abundant in gouty conditions), guanin (?), car- 
 baminic acid ; all occur in very small amounts. 
 
 V. Sarcolactic Acid and Indican, also in small amount. 
 
 VI. Salts (.085 to .09 per cent.). — The most abundant salt is sodium chloride 
 (0.5 per cent.), and next to it sodium carbonate. [It is most important to note 
 that the soda salts are- far more abundant in the serum than the potassium salts. 
 The ratio may be as high as to : 1.] Animal diet increases the amount of salts, 
 vegetable food diminishes it temporarily. 
 
 Salts in human blood serum (Hoppe-Seyler). 
 Sodic Chloride, 4.92 per 1000 
 " Sulphate, 0.44 " 
 
 " Carbonate, 0.21 " 
 
 VII. Water about 90 per cent. 
 
 VIII. A yellow Pigment. 
 
 Sodic Phosphate, . . 0.15 per 1000 
 Calcic Phosphate, . \ », « 
 Magnesic / 
 
 Thudichum regards the pigment of the serum as lutein; Maly, as hydrobilirubin ; and MacMunn 
 as choletelin. 
 
 33. THE GASES OF THE BLOOD. —Absorption of Gases by Solid Bodies and by 
 Fluids. — Absorption by Solid Bodies. — A considerable attraction exists between the particles of 
 solid porous bodies and gaseous substances, so that gases are attracted and condensed within the 
 pores of solid bodies, i. e„ the gases are absorbed. Thus I volume of boxwood charcoal (at 12° 
 C. and ordinary barometric pressure) absorbs 35 volumes C0 2 , 9.4 vol. O, 7.5 vol. N, 1.75 vol. H. 
 Heat is always formed when gases are absorbed, and the amount of heat evolved bears a relation to 
 the energy with which the absorption takes place. Non-porous bodies are similarly invested by a 
 layer of condensed gases on their surface. 
 
 By Fluids. — Fluids can also absorb gases. A known quantity of fluid at different pressures 
 always absorbs the same volume of gas. 'Whether the pressure be great or small, the volume of the 
 gas absorbed is equally great {W.Henry). But according to Boyle and Mariotte's law (1679), 
 when the pressure within the same volume of gas is increased, the volume varies inversely as the 
 pressure. 
 
 Hence it follows that, with varying pressure, the volume of gas absorbed remains the same, but 
 the quantity of gas [weight, density) is directly proportional to the pressure. If the pressure =0, 
 the weight of the gas absorbed must also = o. As a necessary result of this, we see that (1) 
 fluids can be freed of their absorbed gases in a vacuum under an air pump. 
 
 Coefficient of Absorption means the volume of a gas (0° C.) which is absorbed by a unit of 
 volume of a liquid (at 760 mm. Hg) at a given temperature. The volume of a gas absorbed, and 
 therefo e the coefficient of absorption, is quite independent of the pressure, while the weight of the 
 gas is proportional to it. Temperature has an important influence on the coefficient of absorption. 
 With a low temperature it is greatest; it diminishes as the temperature increases; and at the boiling 
 point it = o. Hence, it follows that (2) absorbed gases may be expelled from fluids simply by 
 causing the fluids to boil. The coefficient of absorption diminishes for different fluids and gases, 
 with increasing temperature, in a. special, and by no means uniform, manner, which must be deter- 
 
EXTRACTION OF THE BLOOD GASES. 57 
 
 mined empirically for each liquid and gas. Thus the coefficient of absorption for CO z in water 
 diminishes with an increasing temperature, while that for H in water remains unchanged between 
 o° and 20° C. 
 
 Diffusion and Absorption of Gases. — Diffusion of Gases. — Gases which do not enter into 
 chemical combinations with each other mix with each other in quite a regular proportion. If, e. g., 
 the necks of two flasks be placed in communication by means of a glass or other tube, and if the 
 lower flask contain C0 2 , and the upper one H, the gases mix quite independently of their different 
 specific gravities, both gases forming in each flask a perfectly uniform mixture. The phenomenon 
 is called the diffusion of gases. If a porous membrane be previously inserted between the gases, 
 the exchange of gases still goes on through the membrane. But (as with endosmosis in fluids) 
 the gases pass with unequal rapidity through the pores, so that at the beginning of the experiment a 
 larger amount of gas is found on one side of the membrane than on the other. According to Gra- 
 ham, the rapidity of the diffusion of the gases through the pores is inversely proportional to the 
 square root of their specific gravities. (According to Bunsen, however, this is not quite correct.) 
 
 Different Gases Forming a Gaseous Mixture do not Exert Pressure upon One Another. 
 — Gases', therefore, pass into a space filled with another gas, as they would pass into a vacuum. If 
 the surface of a fluid containing absorbed gases be placed in contact with a very large quantity of 
 another gas, the absorbed gases diffuse into the latter. Hence, absorbed gases can be removed by 
 (3) passing a stream of another gas through the fluid, or by merely shaking up the fluid with another 
 gas. 
 
 Partial Pressure. — If two or more gases are mixed in a closed space over a fluid, as the different 
 gases existing in a gaseous mixture exert no pressure upon each other, the several gases are 
 absorbed. The weight of each absorbed is proportional to the pressure under which each gas 
 would be were it the only gas in the space. This pressure is called the partial pressure of a 
 gas ( Bunsen). The absorption of gases from their mixtures, therefore, is proportional to the par- 
 tial pressure. The partial pressure of a gas in a space is at the same time the expression for the 
 tension of the gas absorbed by a fluid. 
 
 The air contains 0.2096 volume of O, and 0.7904 volume N. If I volume of the air be placed 
 under apressure, P, over water, the partial pressure under which O is absorbed = 0.2096 P ; that 
 for N =0.7904 P. At 0° C., and 760 mm. pressure, I volume of water absorbs 0.02477 volume of 
 air, consisting of 0.00862 volume O, and 0.01615 volume N. It contains, therefore, 34 per cent. 
 O and 66 per cent. N. Therefore, water absorbs from the air a mixture of gases containing a 
 larger percentage of O than the air itself. 
 
 34. EXTRACTION OF THE BLOOD GASES.— [The blood to be analyzed must be 
 collected over mercury, so as to avoid its contact with air. This is easily done by means of a special 
 apparatus, consisting of a graduated tube filled with mercury and communicating with a glass globe 
 also filled with mercury, which can be lowered as the blood flows into the graduated tube.] 
 
 The extraction of the gases from the blood, and their collection for chemical analysis, are carried 
 out by means of the mercurial pump [C, Ludwig). Fig. 19 shows in a diagrammatic form the 
 arrangement of Pfliiger's gas pump. 
 
 It consists of a receptacle for the blood or " blood bulb " (A), a glass globe capable of 
 containing 250 to 300 ex., connected above and below with tubes, each of which is provided with 
 a stop-cock, a and b ; b is an ordinary stop-cock, while a has through its long axis a perforation 
 which opens at x, and is so arranged that, according to the position of the handle, it leads up into 
 the blood bulb (position x, a), or downward through the lower tube (position x', a'). This blood 
 bulb is first completely emptied of air (by means of a mercurial airpump), and then carefully 
 weighed. One end (x') of it is tied into an artery or a vein of an animal, and when the lower 
 stop cock is placed in the position (x, a) blood flows into the receptacle. When the necessary 
 amount of blood is collected the lower stop-cock is put into the position x', a', and the blood bulb, 
 after being cleaned most carefully, is weighed, to ascertain the weight of the amount of blood col- 
 lected. The second part of the apparatus consists of the froth chamber, B, leading upward and 
 downward into tubes, each of which is provided with an ordinary stop-cock, c and d. The froth 
 chamber, as its name denotes, is to catch the froth which is formed during the energetic evolution of 
 the gases from the blood. The lower aperture of the froth chamber is connected by means of a 
 well-ground tube with the blood bulb, while above it communicates with the third part of the 
 apparatus, the drying chamber, G. This consists of a U-shaped tube, provided below with a 
 small glass bulb, which is half filled with sulphuric acid, while in its limbs are placed pieces of 
 pumice stone also moistened with sulphuric acid- As the blood gases pass through this apparatus 
 (which may be shut off by the stop-cocks, e and/), they are freed from their watery vapor by the 
 sulphuric acid, so that they pass quite dry through the stop-cock,/ The short, well-ground tube, 
 D, is fixed tof, and to the former is attached the small barometric tube or manometer, y, which 
 indicates the extent of the vacuum. From D we pass to the pump proper. This consists of two 
 large glass bulbs, which are continued above and below into open tubes ; the lower tubes, Z and w, 
 being united by a caoutchouc tube, G. Both the bulbs and caoutchouc tube contain mercury — the 
 bulbs being about half full, and F being larger than E. The bulb E is fixed ; but F can be raised 
 or lowered by means of a pulley with a rack and pinion motion. If F be raised, E is filled ; if F 
 be lowered, E is emptied. The upper end of E divides into two tubes, g and h, of which g is 
 
58 
 
 EXTRACTION OF THE BLOOD GASES. 
 
 united to D. The ascending tube, h (gas-delivery tube), is very narrow, and is bent so that its 
 free end dips into a vessel containing mercury, v (a pneumatic trough), and the opening is placed 
 exactly under the tube for collecting the gases, the eudiometer, J, which is also filled with mercury. 
 Where g and H unite, there is a two-way stop-cock, which in one position, H, places E in commu- 
 nication with A, B, G, D, the chambers to be exhausted, and in the position K, shuts off A, B, G, 
 D, and places the bulb, E, in communication with the gas-delivery tube, h, and the eudiometer, J. 
 
 B, G, D are completely emptied of air, thus : The stop-cock is placed in the position, K ; raise 
 F until drops of mercury issue from the fine tube, i (not yet placed under J) ; place the stop-cock 
 
 Fig. 19. 
 
 Scheme of PflUger's Gas Pump. A, blood bulb ; a, stop-cock, with a longitudinal perforation opening upward ; a', 
 the same opening downward ; b and c, stop-cocks; B, froth chamber; d, e,/^ stop-cocks; G, drying cham- 
 bers, containing sulphuric acid and pumice stone ; D, tube, with manometer, y, 
 
 in the position H, lower F; stop-cock in position, K and so on until the barometer, y, indicates a 
 complete vacuum. J is now placed over i. Open the cocks c and b, so that the blood bulb, A, 
 communicates with the rest of the apparatus, and the blood gases froth up in B, and after being 
 dried in G pass toward E. Lower F, and they pass into E; stop-cock in position K, raise F, and 
 the gases are collected in J, under mercury. The repeated lowering and raising of F with the 
 corresponding position of the stop-cocks ultimately drives all the gases into J. The removal of 
 the gases is greatly facilitated by placing the blood bulb, A, in a vessel containing water at 
 60° C. 
 
THE BLOOD GASES. b\) 
 
 It is well to remove the gases from the blood immediately after it is collected from a bloodvessel, 
 because the O undergoes a diminution if the blood be kept. Of course, in making several analyses 
 it is difficult to do this, and the best plan to pursue in that case is to keep the receptacles containing 
 the blood on ice. 
 
 Mayow (1670) observed that gases were given off from blood in vacuo. Magnus (1837) 
 investigated the percentage composition of the blood gases. The more important recent inves- 
 tigations have been made by Lothar Meyer (1857), and by the pupils of C. Ludwig and E. Pflilger. 
 
 35. QUANTITATIVE ESTIMATION OF THE BLOOD 
 GASES. — The gases obtained from blood consist of O, C0 2 , and N. Pflilger 
 obtained (at o° C. and 1 metre Hg pressure), 47.3 volumes per cent, consisting 
 of— 
 
 O 16.9 per cent. ; C0 2 29 per cent. ; N 1.4 per cent. 
 As is shown in Fig. 19, the gases are obtained in an eudiometer, i. <?., in a nar- 
 row tube, J, closed at one end, and with a very exact scale marked on it, and 
 having two fine platinum wires melted into its upper end, with their free ends 
 projecting into trie tube (/ and n). 
 
 (1) Estimation of the C0 2 . — A small ball of fused caustic potash, fixed on a platinum wire, is 
 introduced into the mixture of gases through the lower end of the eudiometer, under cover of the 
 mercury. The surface of the potash ball is moistened before it is introduced. The C0 2 unites 
 with the potash to form potassium carbonate. After it has been in for a considerable time (24 hours), 
 it is withdrawn in a similar manner. The diminution in volume indicates the amount of C0 2 
 absorbed. 
 
 (2) Estimation of the O. — (a) Just as in estimating the C0 2 , a ball of phosphorus on a 
 platinum wire is introduced into the eudiometer (Bertholet); it absorbs the O and forms phosphoric 
 acid. Another plan is to employ a small papier-machg ball saturated with pyrogallic acid in caustic 
 potash, which rapidly absorbs {Lieiig), After the ball is removed, the diminution in volume 
 indicates the quantity of O. 
 
 (b) The O is most easily and accurately estimated by exploding it in the eudiometer ( Volta and 
 Bunsen). Introduce a sufficient quantity of H into the eudiometer, and accurately ascertain its 
 volume ; an electrical spark is now passed between the wires, p and », through the mixture of gases ; 
 the O and H unite to form water, which causes a diminution in the volume of the gases in the 
 eudiometer, of which y^ is due to the O used to form water (H 2 0). 
 
 (c) Estimation of the N. — When the C0 2 and O are estimated by the above method, the 
 remainder is pure N. 
 
 36. THE BLOOD GASES.— [In human blood the average is estimated to 
 be, at o° C and 1 metre pressure, 
 
 C C0 2 N 
 
 Arterial blood 16 30 I to 2 per cent. 
 
 Venous blood 6 to 10 35 1 to 2 " 
 
 or, calculated at o° C. and 760 mm. pressure, 
 
 Arterial blood, 20 39 1.4 percent. 
 
 Venous blood, 8 to 12 46 1.4 " j 
 
 I. Oxygen exists in arterial blood (dog), on an average, to the extent of 1 7 
 volumes per cent, (at o° C. and 1 metre Hg pressure) (Pfluger). According to 
 Pfluger, arterial blood (dog) is saturated to -fo with O, while, according to Hiifner, 
 it is saturated to the extent of \%. In venous blood the quantity varies very greatly ; 
 in the blood of a passive muscle 6 volumes per cent, have been found ; while in 
 the blood after asphyxia it is absent, or occurs only in traces. It is certainly more 
 abundant in the comparatively red blood of active glands (salivary glands, kidney), 
 than in ordinary dark venous blood. 
 
 [Modifying Conditions. — The amount of O obtainable from the blood depends upon the organ 
 from which the blood comes, or whether the organ be active or at rest. Thus the O present in the 
 
 Carotid artery is 21 per cent. I Renal vein (kidney active), 17 per cent. 
 
 Renal artery, 19 " | Renal vein (kidney at rest), 6 " 
 
 Bert finds that increase of the atmospheric pressure from I to 10 atmospheres increases the amount 
 of O in arterial blood from 20 to over 24 per cent., and that of N from 1.8 to over 9 per cent., while 
 the C0 2 is but slightly affected.] 
 
 The O in Blood occurs — (a) simply absorbed in the plasma. This is only 
 a minimal amount, and does not exceed what distilled water at the temperature of 
 
60 THE BLOOD GASES AND OZONE. 
 
 the body would take up at the partial pressure of the O in the air of the lungs 
 (Lothar Meyer). According to Fernet, serum takes up slightly more O than cor- 
 responds to the pressure, and this is perhaps due to the trace of haemoglobin con- 
 tained in the plasma or the serum, and which is derived from the solution of red 
 corpuscles. 
 
 (b) Almost the total O of the blood is chemically united, and therefore not 
 subject to the law of absorption. It is loosely united to the haemoglobin of the 
 red corpuscles, with which it forms oxyhemoglobin (§ 15). 
 
 The absorption of this quantity of O is completely independent of pressure ; hence, animals con- 
 fined in a closed space until they are nearly asphyxiated, can use up almost all the O from the 
 surrounding atmosphere. The fact of the union being independent of pressure is proved by the 
 following : The blood only gives off copiously its chemically united O, when the atmospheric pres- 
 sure is lowered to 20 millimetres, Hg. ( Worm Miiller); and, conversely, blood only takes up a little 
 more O when the pressure is increased to 6 atmospheres {Bert). 
 
 Physical Methods of obtaining O from Blood. — Notwithstanding this 
 chemical union between the Hb and O, however, the total O of the blood can be 
 expelled from its state of combination by those means which set free absorbed 
 gases — (a) by introducing blood into a Torricellian vacuum ; (b) by boiling ; (c) 
 by the conduction of other gases [H, N, CO, or NO] through the blood, because 
 the chemical union of the oxyhemoglobin is so loose that it is decomposed even 
 by these physical means. 
 
 Chemical Reagents. — Among chemical reagents the following reducing 
 substances — ammonium sulphide, sulphuretted hydrogen, alkaline solutions of 
 sub-salts, iron filings, etc., rob blood of its O (p. 40). 
 
 With regard to the taking up of O, the total quantity of blood behaves exactly 
 like a solution of haemoglobin free from O (Preyer). The absorption of O is 
 more rapid in blood than in a solution of Hb. 
 
 Relation to Fe. — The amount of iron in the blood (0.55 in 1000 parts) stands in direct relation 
 to the amount of Hb; this to the quantity of blood corpuscles; and this, in turn, to the specific 
 gravity of the blood. The amount of O in the blood, therefore, is nearly proportional to the specific 
 gravity of the blood, and it is also in proportion to the amount of iron in the blood. Picard affirms 
 that 2.36 grammes of iron in the blood can fix chemically 1 grm. O ; while, according to Hoppe- 
 Seyler, the proportion is 1 atom iron to 2 atoms O. 
 
 During morphia narcosis the amount of O in the blood is diminished [E-uiald); after hemorrhage 
 the arterial blood is saturated with O (f. G. Ott). 
 
 Disappearance of O. — Even immediately after blood is shed, there is a slight disappearance of 
 O, as a physiological index of respiration of the tissues within the living blood itself ($ 132). 
 
 When blood is kept long outside of the blood vessels, the quantity of O gradually diminishes, and 
 if it be kept for a length of time at a high temperature it may disappear altogether. This depends 
 upon decomposition occurring within the blood. By this decomposition in the blood (cadaveric 
 phenomenon), reducing substances are formed which consume the O.' All kinds of blood, however, 
 do not act with equal energy in consuming O, e. g., venous blood from active muscles acts most 
 energetically, while that from the hepatic vein has very little effect. C0 2 appears in the blood in 
 place of the O, and the color darkens. The amount of C0 2 produced is sometimes greater than 
 that of the O consumed. 
 
 If blood (or a solution of oxyhemoglobin) be acted upon by acids (e. g., tartaric acid) until it is 
 strongly acid, O maybe pumped out in considerably less amount, while the formation of C0 2 is not 
 increased. We must, therefore, assume that, during the decomposition of the Hb caused by the 
 acids (g 18), a decomposition product becomes more highly oxidized by the intense chemical union 
 of the O at the moment of its origin (Lothar Meyer, Zuntz, Strassburg). The same phenomenon 
 occurs when oxyheemoglobin is decomposed by boiling. 
 
 37. IS OZONE (O s ) PRESENT IN BLOOD?— On account of the 
 numerous and energetic oxidations which occur in connection with the blood, the 
 question has often been raised as to whether the O of the blood exists in the form 
 of active O (O g ), or ozone. Ozone, however, is contained neither in the blood 
 itself (Schonbein) nor in the blood gases obtained from it. Nevertheless, the red 
 corpuscles (and Hb) have a distinct relation to ozone. 
 
 (1) Tests for Ozone. — Haemoglobin acts as a conveyer of ozone, i.e., it is able to remove the 
 active O of other bodies and to convey or transfer it at once to other easily oxidizable substances. 
 
CARBON DIOXIDE AND NITROGEN IN BLOOD. 61 
 
 («) Turpentine which has been exposed to the air for a long time always contains ozone. The tests 
 for the latter are starch and potassium iodide, the ozone decomposing the iodide, when the iodine 
 strikes a blue with the starch. (&) Freshly-prepared tincture of guaiacum is also rendered blue by 
 ozone. If some tincture of guaiacum be added to turpentine there is no reaction, but on adding a 
 drop of blood a deep blue color is immediately produced, i. e., blood takes the ozone from the tur- 
 pentine and conveys it at once to the dissolved guaiacum, which becomes blue [Schonbein, His). It 
 is immaterial whether the Hb contains O or not. 
 
 (2) It has been asserted also that haemoglobin acts as an ozone producer, i.e., 
 that it can convert the ordinary O of the air into ozone. Hence the reason why 
 red blood corpuscles alone render guaiacum blue. This reaction succeeds best 
 when the guaiacum solution is allowed to dry on blotting paper, and a few drops 
 of blood (diluted 5 to 10 times) are poured on it. That the Hb forms ozone from 
 the surrounding O, is shown by the experiment in which even red blood cor- 
 puscles containing carbonic oxide were found to cause the blue color (Kiihne and 
 Scholz). 
 
 According to Pfliiger, however, these reactions only occur from decomposition 
 of the Hb, and as a result of this view the blood corpuscles cannot be regarded 
 as producers of ozone. 
 
 Sulphuretted hydrogen is decomposed by blood (as by ozone itself) into sulphur and water. 
 Hydric peroxide is decomposed by blood into O and water [but this reaction is prevented by the 
 addition of a small amount of hydrocyanic acid (Schonbein\\. Crystallized Hb does not do this, 
 and H 2 2 may be cautiously injected into the blood vessels of animals. This would show that 
 unchanged Hb does not produce ozone. 
 
 Various Forms of Oxygen. — There are three forms of oxygen: (1) The ordinary oxygen 
 (0 2 ) in the air. (2) Active or nascent oxygen (O), which never can occur in the free state, but the 
 moment it is formed acts as a powerful oxidizing agent and produces chemical compounds. It 
 converts water into hydric peroxide — the N of the air into nitrous and nitric acids, and even CO 
 into C0 2 , which ozone does not. It certainly plays an important part in the organism. (3) Ozone 
 (O s ), which is formed by the decomposition of several molecules of ordinary oxygen (0 2 ) into two 
 atoms of O, and the appropriation of each of these atoms by a molecule of undecomposed oxygen. 
 It is oxygen condensed to J of its volume. 
 
 38. CARBON DIOXIDE AND NITROGEN IN BLOOD.— II. 
 Carbon Dioxide. — In arterial blood there are about 30 volumes per cent, of 
 C0 2 (at o° C. and 1 metre pressure — Setschenowy, but in venous blood the amount 
 is very variable, e.g., in the venous blood of passive muscles there are 35 volumes 
 per cent. (Sczelkow), while in the blood of asphyxia there may be 52.6 volumes 
 per cent. The amount of C0 2 in the lymph of asphyxia is less than that in the 
 blood {Buchner, Gaule~). 
 
 The C0 2 in the entire mass of the blood may be extracted from it or completely 
 pumped out, but during the process of evacuation, or removal of the gas, a new 
 property of the red blood corpuscles is produced, whereby they assume the func- 
 tion of an acid, and thus aid in the chemical expulsion of the C0 2 . This acid- 
 like property of the red corpuscles occurs especially in the presence of O and 
 heat. 
 
 (A) The CO 2 in the Plasma. — The largest portion of the CO % belongs to the 
 plasma (or serum) and it appears all to be in a state of chemical combination. 
 Serum takes up C0 2 quite independently of pressure, hence it cannot be merely 
 absorbed. A certain part of the C0 2 can be removed from the serum (plasma) by 
 the Torricellian vacuum, while another part is obtained only after the addition of 
 an acid. [The latter is called the "fixed" C0 2 , while the former is known as the 
 "loose" C0 2 .] 
 
 The union of C0 2 in the serum may take place in the following ways : — 
 
 (1) C0 2 is united to the soda of the plasma in the form of " sodic carbonate." 
 This portion of the CO2 can only be displaced from its combination by the addi- 
 tion of an acid. (In depriving blood of its gases the red corpuscles play the role 
 of an acid.) 
 
 (2) A portion of the C0 2 is loosely united to sodic carbonate in the form of 
 sodic bicarbonate ; the carbonate takes up 1 equivalent of C0 2 ; Na 2 C0 3 -\- C0 2 + 
 
62 ARTERIAL AND VENOUS BLOOD. 
 
 H 2 = 2NaHC0 3 . This C0 2 may be pumped out, as in the process the bi- 
 carbonate splits up again into the neutral carbonate and C0 2 . 
 
 Preyer has objected to this view on the ground that blood is alkaline in reaction, while all 
 solutions that contain C0 2 in a state of absorption, or loose chemical combination, are always acid. 
 Pfiiiger and Zuntz showed that blood, after being completely saturated with COj still remains 
 alkaline. 
 
 As the bicarbonate only gives up its C0 2 very slowly in vacuo, while blood gives off its C0 2 very 
 energetically, perhaps the soda, united with an albuminous body, combines with the C0 2 and forms 
 a complex compound, from which the C0 2 is rapidly given off in vacuo. 
 
 (3) A minimal portion of the C0 2 may be chemically united in the plasma with 
 neutral sodic phosphate (Fernet}. One equivalent of this salt can fix one equiva- 
 lent of C0 2 , so acid sodium phosphate and acid sodium carbonate are formed, 
 Na 2 HP0 4 + C0 2 + H 2 = NaH 2 P0 4 + NaH,C0 3 (Hermann). When the gases 
 are removed the C0 2 escapes, and neutral sodic phosphate remains. 
 
 It is probable, however, that almost all the sodic phosphate found in the blood-ash arises from 
 the burning of lecithin ; we have, therefore, to consider only the very small amount of this salt 
 which occurs in the plasma (Hoppe-Seyler and Sertoli). 
 
 (B) The C0 2 in the Blood Corpuscles. — The red corpuscles contain C0 2 
 in a loose chemical combination; for (ij a volume of blood can fix nearly as 
 much C0 2 as an equal volume of serum (Ludwig, Al. Schmidt) ; and (2) with 
 increasing pressure, the absorption of C0 2 by blood takes place in a different 
 ratio from what occurs with serum {Pfiiiger, Zuntz). The red corpuscles may fix 
 more C0 2 than their own volume, and the union of the C0 2 seems to depend 
 upon the Hb; for Setschenow found that when Hb was acted on by C0 2 , its power 
 of fixing the latter was increased, which is, perhaps, due to the formation of some 
 substance (paraglobulin) more suited for fixing C0 2 . The colorless corpuscles 
 also fix C0 2 after the manner of the serum constituents, and to the extent of \ to 
 ■j 1 ^ of the absorbing power of serum {Setschenow). 
 
 III. Nitrogen exists in the blood to the extent of 1.4 to 1.6 vol. per cent., 
 and it appears to be simply absorbed. 
 
 After the use of I, Hg, sodic oxalate and nitrate, there is a diminution of C0 2 in arterial blood 
 (Feiteiberg), and also in fever (Geppert, Minkowski). [In the last case it is, perhaps, due to the 
 diminished alkalinity, and this is, in part, owing to the acid products formed by the decomposition 
 of the tissues.] 
 
 It is still doubtful whether a small part of the N exists chemically united in the red corpuscles. 
 Outside the body, when blood is heated, and when there is a free supply of O and warmth, it gives 
 off very minute quantities of ammonia, which are, perhaps, derived from the decomposition of 
 some salt of ammonia as yet unknown (Kuhne and Utrauch). 
 
 39. ARTERIAL AND VENOUS BLOOD.— Arterial blood contains 
 in solution all those substances which are necebsary for the nutrition of the tissues, 
 those which are employed in secretion, and it also contains a rich supply of O. 
 Venous blood must contain less of all these, but, in addition, it holds the used-up 
 or effete substances derived from the tissues, and the products of their retrogressive 
 metabolism are more numerous ; there is in venous blood a larger amount of C0. 2 , 
 
 It is evident, also, that the blood of certain veins must have special characters.- 
 e.g., that of the portal and hepatic veins. 
 
 [According to C. Schmidt, the blood of the portal vein contains more water, plasma, salts and 
 fats, but less extractives and corpuscles, than the blood of the hepatic vein; while (when an animal 
 is not digesting) sugar is absent, or, at least, only in traces in the portal vein, and in considerable 
 amount in the hepatic vein (§ 175).] 
 
 The following are the most important points of difference between arterial 
 blood and venous blood : — 
 
 Arterial Blood contains — 
 
 more O, 
 less C0 2 , 
 more water, 
 more fibrin, 
 
 more extractives, 
 
 more salts, 
 
 more sugar, 
 
 fewer blood corpuscles, 
 
 less urea. 
 
 It is bright red, and not 
 
 dichroic. 
 As a rule, it is 1° C. warmer. 
 
ABNORMAL CONDITIONS OF THE BLOOD. 63 
 
 The bright-red color of arterial blood depends on the presence of oxyhaemo- 
 globin, while the dark color of venous blood is due to its smaller proportion of 
 oxyhaemoglobin and the quantity of reduced haemoglobin which it contains. The 
 dark change of color is not to be attributed to the larger quantity of C0 2 in venous 
 blood (Mdrchand) ; for if equal qualities of O be added to two portions of blood, 
 and if C0 2 be added to one of them, the color is not changed [Pfluger). 
 
 40. QUANTITY OF BLOOD.— In the adult, the quantity of blood is 
 equal to -fa of the body weight {Bischoff) ; in newly -born children -Jj ( Welcker). 
 
 According to Schiicking, the amount of blood in a newly-born child depends, to some extent, 
 upon the time at which the umbilical cord is ligatured. The amount = T *j of the body weight when 
 the cord is tied at once, while if it is tied somewhat later, it may be \. Immediate ligature of the 
 cord may, therefore, deprive a newly-born child of a hundred grammes of blood. Further, the 
 number of corpuscles is less in a child after immediate ligature of the umbilical cord than when it 
 is tied somewhat later (Helot). 
 
 Various methods are adopted to ascertain the amount of blood, but perhaps 
 that of Welcker is the best. 
 
 The methods of Valentin (1838) and Ed. Weber (1850) are not now used, as the results obtained 
 are not sufficiently accurate. 
 
 Method of Welcker (1854). — Begin by taking the weight of the animal to be experimented 
 on ; place a cannula in the carotid, and allow the blood to run into a flask previously weighed, and 
 in which small pebbles (or Hg) have been placed, in order to defibrinate the blood by shaking. 
 Take a part of this defibrinated blood, and make it cherry-red in color by passing through it a 
 stream of CO (because ordinary blood varies in color according to the amount of O contained in it 
 — Gscheidlen, Heidenhain). Tie a f~ -shaped canula in the two cut ends of the carotid, and allow 
 a 0.6 per cent, solution of common salt to flow into the vessel from a pressure bottle ; collect the 
 colored fluid issuing from the jugular veins and inferior vena cava until the fluid is quite clear. 
 The entire body is then chopped up (with the exception of the contents of the stomach and intes- 
 tines, which are weighed, and their weight deducted from the body weight), and extracted with 
 water, and after twenty-four hours the fluid is expressed. This water, as well as the washings with 
 salt solution, are collected and weighed, and part of the mixture is saturated with CO. A sample 
 of this dilute blood is placed in a vessel with parallel sides (1 cm. apart), opposite the light (the 
 so-called haematinometer), and in a second vessel of the same dimensions a sample of the undi- 
 luted CO blood is diluted with water from a burette until both fluids give the same intensity of 
 color. From the quantity of water required to dilute the blood to the tint of the washings of the 
 blood vessels, the quantity of blood in the washings is calculated. (On chopping up the muscles 
 alone, we obtain the amount of Hb present in them, which is not taken into calculation— JCiihne.) 
 
 Quantity of Blood in Various Animals. — The quantity of blood in the 
 mouse = ,rV to T \ ; guinea pig ^. T ( T V to ^) ; rabbit = ^. T (^ to ^ ) j dog 
 
 = tV (irY t0 tV) > cat = -jt.t J birds = tV t0 ts- > fro S = tV t0 -fo > fishes = tV 
 to. ^ of the body weight (without the contents of the stomach and intestines). 
 
 The specific gravity of the blood ought always to be taken when estimating the 
 amount of blood. The amount of blood is diminished during inanition ; fat 
 persons have relatively less blood ; after hemorrhage the loss is at first replaced by 
 a watery fluid, while the blood corpuscles are gradually regenerated. 
 
 Blood in Organs. — The estimation of the quantity of blood in different organs 
 is done by suddenly ligaturing their blood vessels intra vitam. A watery extract 
 of the chopped-up organ is prepared, and the quantity of blood estimated as 
 described above. [Roughly it may be said that the lungs, heart, large arteries, 
 and veins contain % ; the muscles of the skeleton, % ; the liver, ^ ; and other 
 organs, % {Hanke).'] 
 
 41. VARIATIONS FROM THE NORMAL CONDITION OF THE BLOOD.— 
 (A) Polysomia. — (1) An increase in the entire mass of the blood, uniformly in all organs, cor\- 
 SiWxAes polyamia (or plethora), and in over-nourished individuals it may approach a pathological 
 condition. A bluish-red color of the skin, swollen veins, large arteries, hard, full pulse, injection 
 of the capillaries and smaller vessels of the visible mucous membranes are signs of this state, and 
 when accompanied by congestion of the brain, give rise to vertigo and congestion of the lungs, as 
 shown by breathlessness. After major amputations with little loss of blood a relative increase of 
 blood has been found (?) [plethora apocoptica). [In this case, the plethora is transient.] 
 
 Transfusion. — Polysomia may be produced artificially by the injection of blood of the same 
 species. If the normal quantity of blood be increased 83 per cent, no abnormal condition occurs, 
 
64 ABNORMAL CONDITIONS OF THE BLOOD. 
 
 because the blood pressure is not permanently raised. The excess of blood is accommodated in 
 the greatly distended capillaries, which may be stretched beyond their normal elasticity ( Worm 
 Miiller). If it be increased to 150 per cent, there are variations in the blood pressure, life is 
 endangered, and there may be sudden rupture of blood vessels ( Worm Miiller). 
 
 Fate of Transfused Blood. — After the transfusion of blood the formation of lymph is greatly 
 increased ; but in one or two days the serum is used up, the water is excreted chiefly by the urine, 
 and the albumin is partly changed into urea (Landois). Hence, the blood at this time appears to 
 be relatively richer in blood corpuscles (Panum, Lesser, Worm Miiller). The red corpuscles 
 break up much more slowly, and the products thereof are partly excreted as urea and partly (but 
 not constantly) as bile pigments. Even after a month an increase of colored blood corpuscles has 
 been observed ( Tschirjew). That the blood corpuscles are broken up slowly in the economy is 
 proved by the fact that the amount of urea is much larger when the same quantity of blood is 
 swallowed by the animal than when an equal amount is transfused {Tschirjew, Landois). In the 
 latter case there is a moderate increase of the urea, lasting for days, a proof of the slow decomposi- 
 tion of the red corpuscles. Pronounced over-filling of the vessels causes loss of appetite and a ten- 
 dency to hemorrhage of the mucous membranes. 
 
 (2) Polysemia serosa is that condition in which the amount of serum, i. e., the amount of 
 water in the blood, is increased. This may be produced artificially by the transfusion of blood 
 serum from the same species. The water is soon given off in the urine, and the albumin is decom- 
 posed into urea, without, however, passing into the urine. An animal forms more urea in a short 
 time from a quantity of transfused serum than from the same quantity of blood, a proof that the 
 blood corpuscles remain longer undecomposed than the serum (J<orster, Landois). If serum from 
 another species of animal be used [e. g., dog's serum transfused into a rabbit), the blood corpuscles 
 of the recipient are dissolved; hsemoglobinuria is produced (Ponfick) ; and if there be general disso- 
 lution of the corpuscles, death may occur {Landois). 
 
 Polyaemia aquosa is a simple increase of the water of the blood, and occurs temporarily after 
 copious drinking, but increased diuresis soon restores the normal condition. Diseases of the kid- 
 neys which destroy their secreting parenchyma produce this condition, and often general dropsy, 
 owing to the passage of water into the tissues. Ligature of the ureter produces a watery condition 
 of the blood. 
 
 (3) Plethora polycythaemica, Hyperglobulie. — An increase of the red corpuscles has been 
 assumed to occur when customary regular hemorrhages are interrupted, e. g., menstruation, bleeding 
 from the nose, etc. ; but the increase uf corpuscles has not been definitely proved. There is a proved 
 case of temporary polycythsemia, viz., when similar blood is transfused, apartof the fluid being used 
 up, while the corpuscles remain unchanged for a considerable time. There is a remarkable increase 
 in the number of blood corpuscles (to 8 82 millions per cubic millimeter, p. 18) in certain severe 
 cardiac affections where there is great congestion, and much water transudes through the vessels. 
 In cases of hemiplegia, for the same reason, the number of corpuscles is greater on the paralyzed 
 congested side (Penzoldt). After diarrhoea, which diminishes the water of the blood, there is also 
 an increase (Brouardel). There is a temporary increase in the haematoblasts as a reparative process 
 after severe hemorrhage (§ 7), or after acute diseases. In cachectic conditions this increase con- 
 tinues, owing to the diminished non-conversion of these corpuscles into red corpuscles. In the 
 last stages of cachexia the number diminishes more and more until the formation of hsematoblasts 
 ceases \Hayem). 
 
 (4) Plethora hyperalbuminosa is a term applied to the increase of albumins in the plasma, 
 such as occurs after taking a large amount of food. A similar condition is produced by transfusing 
 the serum of the same species, whereby, at the same time, the urea is increased. Injection of egg 
 albumin produces albuminuria (StoAvis Lehmann). 
 
 [The subcutaneous injection of human blood has been practiced with good 
 results in anemia (v. Ziemssen). When defibrinated human blood is injected sub- 
 cutaneously, while its passage into the circulation is aided by massage, it causes 
 neither pain nor inflammation, but the blood of animals, and a solution of haemo- 
 globin, always induce abscess (Benczur). Blood is also rapidly absorbed when 
 injected in small amount into the respiratory passages.] 
 
 Mellitsemia — The sugar in the blood is partly given off by the urine, and in " diabetes 
 mellitus " I kilo. (2.2 ft>) may be given off daily, when the quantity of urine may rise to 25 
 kilos. To replace this loss a large amount of food and drink is required, whereby the urea may be 
 increased threefold. The increased production of sugar causes an increased decomposition of 
 albuminous tissues; hence, the urea is always increased, even though the supply of albumin be 
 insufficient. The patient loses flesh ; all the glands, and even the testicles, atrophy or degenerate 
 (pulmonary phthisis is common) ; the skin and bones become thinner ; the nervous system holds out 
 longest. The teeth become carious on account of the acid saliva, the crystalline lens becomes 
 turbid from the amount of sugar in the fluid of the eye which extracts water from the lens (Kunde, 
 Heubel), and wounds heal badly because of the abnormal condition of the blood. Absence of all 
 carbohydrates in the food causes a diminution of the sugar in the blood, but does not cause it to 
 
ABNORMAL CONDITIONS OF THE BLOOD. 65 
 
 disappear entirely. [The sugar in the blood is also increased after the inhalation of chloroform or 
 amyl nitrite, and after the use of curara, nitrobenzole and chloral (g 175).] 
 
 An excessive amount of inosite has been found in the blood and urine (J 267), constituting melli- 
 turia inosita ( Vokl). 
 
 Lipaemia, or an increase of the Fat in the Blood, occurs after every meal rich in fat, so that 
 the serum may become turbid like milk. Pathologically, this occurs in a high degree in drunk- 
 ards and in corpulent individuals. When there is great decomposition of albumin in the body 
 (and, therefore, in very severe diseases), the fat in the blood increases, and this also takes place 
 after a liberal supply of easily decomposable carbohydrates and much fat. 
 
 The Salts remain very persistently in the blood. The withdrawal of common salt produces 
 albuminuria, and, if all salts be withheld, paralytic phenomena occur {Forster). Over- feeding with 
 salted food, such as salt meat, has caused death through fatty degeneration of the tissues, especially 
 of the glands. Withdrawal of lime and phosphoric acid produces atrophy and softening of the, 
 bones. In infectious diseases and dropsies the salts of the blood are often increased, and dimin- 
 ished in inflammation and cholera. [NaCl is absent from the urine in certain stages of pneumonia, 
 and it is a good sign when the chlorides begin to return to the urine.] [In Scurvy the corpus- 
 cular elements are diminished in amount, but we have not precise information as to the salts, 
 although this disease is prevented, in persons forced to live upon preserved and salted food, by a 
 liberal use of the salts — especially potash salts — of the organic acids, as contained in lime juice. 
 In Gout, the blood, during an acute attack, and also in chronic gout, contains an excess of uric 
 acid (Garrod)."] 
 
 The amount of fibrin is increased [hyperinosis] in inflammations of the lung and pleura 
 [croupous pneumonia, erysipelas], hence, such blood forms a crusta phlogistica (\ 27). In other 
 diseases where decomposition of the blood corpuscles occurs, the fibrin is increased, perhaps because 
 the dissolved red corpuscles yield material for the formation of fibrin. After repeated hemorrhages, 
 Sigm. Mayer found an increase of fibrin. Blood rich in fibrin is said to coagulate more slowly than 
 when less fibrin is present — still there are many exceptions. 
 
 For the abnormal changes of the red and white blood corpuscles, see g 10 ; for Haemophilia, 
 \ 28. 
 
 (B) Diminution of the Quantity of Blood, or its Individual Constituents.— (1) Olige- 
 mia vera, Ansmia, or diminution of the quantity of blood, occurs whenever there is hemor- 
 rhage. Life is endangered in newly-born children when they lose a fewounces of blood; in 
 children a year old, on losing half a pound ; and in adults, when one-half of the total blood is 
 lost. Women bear loss of blood much better than men. The periodical formation of blood after 
 each menstruation seems to enable blood to be renewed more rapidly in their case. Stout persons, 
 old people, and children do not bear the loss of blood well. The more rapidly blood is lost, the 
 more dangerous it is. [A moderate loss of blood is soon made up, but the fluid part is more 
 quickly restored than are the corpuscles.] 
 
 Symptoms of Loss of Blood. — Great loss of blood is accompanied by general paleness and 
 coldness of the cutaneous surface, increased oppression, twitching of the eyeballs, noises in the ears 
 and vertigo, loss of voice, great breathless ness, stoppage of secretions, coma; dilatation of the 
 pupils, involuntary evacuations of urine and faeces, and lastly, general convulsions, are sure signs of 
 death by hemorrhage. In the grayest cases restitution is only possible by means of transfusion. 
 Animals can bear the loss of one-fourth of their entire blood without the blood pressure in the 
 arteries permanently failing, because the blood vessels contract and accommodate themselves to the 
 smaller quantity of blood (in consequence of the stimulation of the vasomotor centre in the medulla). 
 The loss of one-third of the total blood diminishes the blood pressure considerably (one-fourth in 
 the carotid of the dog). If the hemorrhage is not such as to cause death, the fluid part of the 
 blood and the dissolved salts are restored by absorption from the tissues, the blood pressure gradu- 
 ally rises, and then the albumin is restored, though a longer time is required for the formation of 
 red corpuscles. At first, therefore, the blood is abnormally rich in water [hydremia) and at last 
 abnormally poor in corpuscles (oligocythemia, hypoglobulie). With the increased lymph stream 
 which pours into the blood, the colorless corpuscles are considerably increased above normal, and 
 during the period of restitution fewer red corpuscles seem to be used up (e. g., for bile). 
 
 After moderate bleeding from an artery in animals, Buntzen observed that the volume of the 
 blood was restored in several hours ; after more severe hemorrhage in 24 to 48 hours. The red 
 blood corpuscles, after a loss of blood equal to 1 . 1 to 4.4 per cent, of the body weight, are restored 
 only after 7 to 34 days. The regeneration begins after 24 hours. During the period of regenera- 
 tion the number of the smallest blood corpuscles (hsematoblasts) is increased. Even in man the 
 duration of the period of regeneration depends upon the amount of blood lost (Lyon) The 
 amount of haemoglobin is diminished nearly in proportion to the amount of the hemorrhage (Bizzo- 
 zero and Salvioli). 
 
 Metabolism in Anaemia. — The condition of the metabolism within the bodies of anaemic per- 
 sons is important. The decomposition of proteids is increased (the same is the case in hunger), 
 hence the excretion of urea is increased (Bauer, Jiirgensen). The decomposition of fats, on the 
 contrary, is diminished, which stands in relation with the diminution of C0 2 given off. Anaemic 
 
 s 
 
66 
 
 ORGANISMS IN THE BLOOD. 
 
 and chlorotic persons put on fat easily. The fattening of cattle is aided by occasional bleedings 
 and by intercurrent periods of hunger (Aristotle). 
 
 (2) An excessive thickening of the blood through loss of water is called Oligaemia sicca. 
 This occurs in man after copious watery evacuations, as in cholera, so that the thick, tarry blood 
 stagnates in the vessels. Perhaps a similar condition — though to a less degree — may exist after 
 very copious perspiration. 
 
 (3) If the proteids in blood be abnormally diminished, the condition is called Oligaemia hyp. 
 albuminosa ; they may be diminished about one-half. They are usually replaced by an excess of 
 water in the blood [so that the blood is watery, constituting Hydraemia], Loss of albumin from 
 the blood is caused directly by albuminuria (25 grammes of albumin may be given off by the 
 urine daily), persistent suppuration, great loss of milk, extensive cutaneous ulceration, albuminous 
 diarrhoea (dysentery). Frequent and copious hemorrhages, however, by increasing the absorption 
 of water into the vessels, at first produce oligaemia hypalbuminosa. 
 
 [Organisms in the Blood. — The presence of animal and vegetable parasites in the blood gives 
 rise to certain diseases. Some of these, and especially the vegetable organisms, have the power of 
 
 Fig. 20. 
 
 Fig. 21. 
 
 A, diagram of micrococcus ; B , bacte- * Bacillus anthracis from the 
 
 Hum; C, vibrios ; D, bacilli ; E, blood (ox) in splenic fever 
 
 spirillum. {Co/in). 
 
 multiplying in the blood. The vegetable forms belonging to the Schizomycetes are frequently 
 spoken of collecting under the title bacteria. They are classified by Cohn into 
 
 I. Sphaerobacteria 
 II. Microbacteria "J 
 
 III. Desmobacteria \ exhibit movements. 
 
 IV. Spirobacteria J 
 
 These forms are shown in Fig. 20. The micrococci (A) are examples of I ; while bacterium 
 'termo (B) is an example of II. In III the members are short cylindrical rods, straight (Bacillus, 
 
 D) or wavy (Vibrio, C). Splenic fever of cattle is due to the presence of Bacillus anthracis (Fig. 
 
 21). These rod-shaped bodies under proper conditions divide transversely and elongate, but they 
 
 also form spores in their interior, which in turn, under appropriate conditions, may germinate (Fig. 
 
 21). Class IV is represented by two genera, Spirochaeta and Spirillum (Fig. 20), the former with 
 ■ close, and the latter with open spirals. The Spirochaeta Obermeieri (often spoken of as " Spirillum " ) 
 
 is present in the blood during the paroxysms in persons suffering from relapsing fever. Among 
 
 animal parasites are Filaria sanguinis; Bilharzia haematobia, which occurs in the portal vein and in 
 
 the veins of the urinary apparatus.] 
 
PHYSIOLOGY OF THE CIRCULATION. 
 
 Fig. 22. 
 
 42. GENERAL VIEW OF THE CIRCULATION.— The blood 
 
 within the vessels is in a state of continual motion, 
 being carried from the ventricles by the large arteries 
 (aorta and pulmonary) and their branches to the system 
 of capillary vessels, from which again it passes into the 
 veins that end in the atria of the auricles ( W. Harvey). 
 
 The Cause of the Circulation is the difference of 
 pressure which exists between the blood in the aorta 
 and pulmonary artery on the one hand, and the two 
 venae cavae and the four pulmonary veins on the other. 
 The blood, of course, moves continually, in its closed 
 tubular system, in the direction of least resistance. 
 The greater the difference of pressure, the more rapid 
 the movement will be. The cessation of the difference 
 of pressure (as after death) naturally brings the move- 
 ment to a standstill (§ 81). 
 
 The circulation is usually divided into — 
 
 (1) The greater, or systemic circulation, 
 which includes the course of the blood from the left 
 auricle and left ventricle, through the aorta and all 
 
 - its branches, the capillaries of the body and the veins, 
 until the two venae cavae terminate in the right auricle. 
 
 (2) The lesser, or pulmonic circulation, 
 which includes the course from the right auricle and 
 right ventricle, the pulmonary artery, the pulmonary 
 capillaries, and the four pulmonary veins springing 
 from them, until these open into the left auricle. 
 
 (3) The portal circulation, which is sometimes 
 spoken of as a special circulatory system, although it 
 represents only a second set of capillaries (within the 
 liver) introduced into the course of a venous trunk. 
 It consists of the vena portarum — formed by the union 
 of the intestinal or mesenteric and splenic veins, and 
 it passes into the liver, where it divides into capillaries, 
 from which the hepatic veins arise. These last veins 
 join the inferior vena cava. 
 
 Strictly speaking, however, there is no special portal circulation. 
 Similar arrangements occur in other animals in different places ; 
 e.g., snakes have such a system in their suprarenal capsules, and the frog in its kidneys. 
 
 When an artery splits up into fine branches during its course, and these branches do not form 
 capillaries, but reunite into an arterial trunk, a rete mirabile is formed, such as occurs in apes and 
 edentata. Microscopic retia mirabilia exist in the human mesentery (Sckobl). Similar arrange- 
 ments may exist on veins, giving rise to venous retia mirabilia. 
 
 43. THE HEART.— Muscular Fibres of the Heart.— The musculature 
 of the mammalian heart consists of short (50 to 70 /*, man), very fine, transversely 
 striated muscular fibres (C Krause, 1833), which are actual unicellular elements 
 (Eberth, 1866), devoid of a sarcolemma (15 to 25 fi broad), and usually divided 
 
 67 
 
 Scheme of the circulation — a, right 
 auricle; A, right ventricle: 6, 
 left auricle; B, left ventricle; 1, 
 pulmonary artery ; 2, aorta with 
 semilunar valves ; /, area of 
 pulmonary circulation ; K, area 
 of systemic circulation in region 
 supplying the superior vena 
 cava, ; G, area supplying the 
 inferior vena cava, u ; d, d, in- 
 testine, ; m, mesenteric artery; 
 q, portal vein ; L, liver ; h, he- 
 patic vein. 
 
68 ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. 
 
 at their blunt ends, by which means they anastomose and form a network (Fig. 
 23, A, B). The individual muscle cells contain in their centre an oval nucleus, 
 and are held together by a cement which js blackened by silver nitrate, and dis- 
 solved by a 33 per cent, solution of caustic potash. This cement is also dissolved 
 by a 40 per cent, solution of nitric acid. The transverse striae are not very 
 distinct, and not unfrequently there is an appearance of longitudinal striation, 
 produced by a number of very small granules arranged in rows within the fibres. 
 The fibres are gathered lengthwise in bundles, or fasciculi, surrounded and sepa- 
 rated from each other by delicate processes of the perimysium. When the 
 connective tissue is dissolved by prolonged boiling, these bundles can be isolated, 
 and constitute the so-called " fibres" of the heart. The transverse sections of the 
 bundles in the auricles are polygonal or rounded, while in the ventricles they are 
 somewhat flattened. [The muscular mass of the heart is called the myocardium, 
 and is invested by fibrous tissue. It is important to notice that the connective 
 tissue of the visceral pericardium (epicardium) is continuous with that of the 
 endocardium by means of the perimysium surrounding the bundles of muscular 
 fibres.] The fine spaces which exist between these bundles form narrow lacunas, 
 lined with epithelium, and constituting part of the lymphatic system of the heart. 
 
 Fig. 23. 
 
 A, branched muscular fibres from the heart of a mammal ; B, transverse section of the cardiac fibres ; b, con- 
 nective-tissue corpuscles ; c, capillaries ; C, muscular fibres from the heart of a frog. 
 
 [The cardiac muscular fibres occupy an intermediate position between striped and plain muscular 
 fibres. Although they are striped they are involuntary, not being directly under the influence of the 
 will, while they contract more slowly than a voluntary muscle of the skeleton.] 
 
 [In the frog's heart the muscular fibres are, in shape, elongated spindles, or fusiform, in this 
 respect resembling the plain muscle cells, but they are transversely striped (Fig. 23, C). They 
 are easily isolated by means of a 33 per cent, solution of potash or dilute alcohol ( Weissmann, 
 Ratlvier).~\ 
 
 44. ARRANGEMENT OF THE CARDIAC MUSCULAR 
 FIBRES, AND THEIR PHYSIOLOGICAL IMPORTANCE.— 
 
 The study of the embryonic heart is the key to a proper understanding of the 
 complicated arrangement of the fibres in the adult heart. The simple tubular 
 heart of the embryo has an outer circular and an inner longitudinal layer of fibres. 
 The septum is formed later ; hence, it is clear that a part, at least, of the fibres 
 must be common to the two auricles, and a part also to the two ventricles, since 
 there is originally, but one chamber in the heart. The muscular fibres of the 
 auricles, are, however, completely separated from those of the ventricles by the 
 fibro-cartilaginous rings (Lieutaud, 1782). In the auricles the fundamental 
 arrangement of the embryonic fibres partly remains, while in the ventricles it 
 becomes obscured as the cavities undergo a sac-like dilatation, and also become 
 twisted in a spiral manner. 
 
 (1) The Muscular Fibres in the Auricles are completely separated from 
 •the fibres of the ventricles by Una fibrous rings which surround the auriculo-ventri- 
 
ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. 
 
 69 
 
 cular orifices, and which serve as an attachment for the auriculo-ventricular valves 
 (Fig. 24, I). The auricles are much thinner than the ventricles, and their fibres 
 are generally arranged in two layers; the outer transverse layer is continuous over 
 both auricles, while the inner one is directed longitudinally. The outer transverse 
 fibres may be traced from the openings of the venous trunks anteriorly and pos- 
 teriorly over the auricular walls. The longitudinal fibres are specially well marked 
 where they are inserted into the fibro-cartilaginous rings, while in some parts of 
 the anterior auricular wall they are not continuous. In the auricular septum, some 
 fibres, circularly disposed around the fossa ovalis (formerly the embryonic opening 
 of the foramen ovale) are well marked. Circular bands of striped muscle exist 
 around the veins where they open into the heart ; these are least marked on the 
 inferior vena cava, and are stronger and reach higher (2.5 cm.) on the superior 
 vena cava (Fig. 24, II). Similar fibres exist around the pulmonary veins, where 
 they join the left auricle, and these fibres (which are arranged as an inner circular 
 and an outer longitudinal layer) can be traced to the hilus of the lung in man and 
 some mammals; in the ape and rat they extend on the pulmonary veins right into 
 the lung. In the mouse and bat, again, the striped muscular fibres pass so far 
 into the lungs that the walls of the smaller veins are largely composed of striped 
 muscle (Stiedd). 
 
 Fig. 24. 
 
 D 
 
 I. Course of the muscular fibres on the left auricle. Observe the outer transverse and inner longitudinal fibres, the 
 circular fibres on the pulmonary veins (z*. p.) ; V, the left ventricle {John Reid). II. Arrangement oi the striped 
 muscular fibres on the superior vena cava [Elzscher) — a, opening of vena azygos ; v, auricle. 
 
 Circular muscular fibres are found where the vena magna cordis enters the heart, 
 and in the Valvula Thebesii which guards it. 
 
 From a physiological point of view, the following facts are to be noted as a 
 result of the anatomical arrangement : — 
 
 (1) The auricles contract independently of the ventricles. This is seen when 
 the heart is about to die ; then there may be several auricular contractions for one 
 ventricular, and at last only the auricles pulsate. The auricular portion of the J 
 right auricle beats longest; hence, it is called the "ultimum moriens." Inde- 
 pendent rhythmical contractions of the vense cavse and pulmonary veins are often 
 noticed after the heart has ceased to beat {Haller, Nysten). [This beating can 
 also be observed in those veins of a rabbit after the heart is cut out of the body.] 
 
 (2) The double arrangement of the fibres (transverse and longitudinal) pro- 
 duces a simultaneous and uniform diminution of the auricular cavity (such as 
 occurs in most of the hollow viscera). 
 
 (3) The contraction of the circular muscular fibres around the venous orifices, 
 and the subsequent contraction of the auricle, cause these veins to empty them- 
 selves into the auricle ; and by their presence and action they prevent any large 
 quantity of blood from passing backward into the veins when the auricle con- 
 
70 
 
 ARRANGEMENT OF THE VENTRICULAR FIBRES. 
 
 tracts. [No valves are present in the superior and inferior vena cava in the adult 
 heart, or in the pulmonary veins, hence the contraction of these circular muscular 
 fibres plays an important part in preventing any reflux of blood during the con- 
 traction of the auricles.] 
 
 45. ARRANGEMENT OF THE VENTRICULAR FIBRES.— 
 (2) The Muscular Fibres of the Ventricles.— The fibres in the thick wall 
 of the ventricles are arranged in several layers (Fig. 25, A) under the pericardium. 
 First, there is an outer longitudinal layer (A), which is in the form of single bun- 
 dles on the right ventricle, but forms a complete layer on the left ventricle, where 
 it measures about one-eighth of the thickness of the ventricular wall. A second 
 longitudinal layer of fibres lies on the inner surface of the ventricles, distinctly 
 visible at the orifices, and within the vertically-placed papillary muscles, while 
 elsewhere it is replaced by the irregularly-arranged trabeculse carnese. Between 
 these two layers there lies the thickest layer, consisting of more or less transversely 
 
 Fig. 25. 
 
 Course of the ventricular muscular fibres. A, on the anterior surface ; B, view of the apex with the vortex {Henle) ; 
 C, scheme of the course of the fibres within the ventricular wall ; D, fibres passing into a papillary muscle 
 (C. Ludwig). 
 
 arranged bundles, which may be broken up into single layers more or less 
 circularly disposed. The deep lymphatic vessels run between the layers, while the 
 blood vessels lie within the substance of the layers and are surrounded by the 
 primitive bundles of muscular fibres {Henle). All three layers are not completely 
 independent of each other ; on the contrary, the fibres which run obliquely form 
 a gradual transition between the transverse layers and the inner and outer longi- 
 tudinal layers. It is not, however, quite correct to assume that the outer lon- 
 gitudinal layer gradually passes into the transverse, and this again into the inner 
 longitudinal layer (as is shown schematically in C) ; because, as Henle pointed 
 out, the transverse fibres are relatively far greater in amount. In general, the 
 outer longitudinal fibres are so arranged as to cross the inner longitudinal layer at 
 an acute angle. The transverse layers lying between these two form gradual 
 transitions between these directions. At the apex of the left ventricle, the outer 
 longitudinal fibres bend or curve so as to meet at the so-called vortex ("Wirbel") 
 
PERICARDIUM, ENDOCARDIUM, VALVES. 
 
 71 
 
 Fig. 26. 
 
 B, where they enter the muscular substance, and, taking an upward and inward 
 direction, reach the papillary muscles, D {Lower) ; although it is a mistake to say 
 that all the bundles which ascend to the papillary muscles arise from the vertical 
 fibres of the outer surface ; many seem to arise independently within the ven- 
 tricular wall. According to Henle, all the external longitudinal fibres do not 
 arise from the fibrous rings or the roots of the arteries. 
 
 [The assumption that the muscles of the ventricle are arranged so as to form a figure of 8, or in 
 loops, seems to be incorrect ; thus, fibres are said to arise at the base of the ventricle, to pass over 
 it. and to reach the vortex, where they pass into the interior of the muscular substance, to end 
 either in the papillary muscles or high up on the inner surface of the heart at its base. Figs C and 
 D give a schematic representation of this view.] 
 
 A special layer of circular muscular fibres, which acts like a true sphincter, 
 surrounds the arterial opening of the left ventricle, and seems to have a certain 
 independence of action {Henle). 
 
 Only the general arrangement of the ventricular muscular fibres has been indicated here {Lower, 
 Casp. Wolff, /7S0-92). C. Ludwig (1849), an< * more recently Pettigrew (1864), have made the 
 subject a special study, and followed out its complications. According to the last observer, there 
 are seven layers in the ventricles, viz., three external, a fourth or central layer, and three internal. 
 These internal layers are continuous with the corresponding external layers at the apex, thus —one 
 and seven, two and six. 
 
 46. PERICARDIUM, ENDOCARDIUM, VALVES.— The pericardium encloses within 
 its two layers [visceral and parietal] a lymph space — the pericardial space — which contains a small ■' 
 quantity of lymph — the pericardial fluid. It has the structure of a serous membrane, i. e., it con- ' 
 sists of connective tissue mixed with fine elastic fibres arranged in the form of a thin, delicate mem- 
 brane, and covered on its free surfaces with 
 a single layer of epithelium or endothelium, 
 composed of irregular, polygonal, flat cells. 
 
 A rich lymphatic network lies under the 
 pericardium (Fig. 26) and endocardium ; 
 and also in the deeper layers of the vis- 
 ceral pericardium next the heart, but sto- 
 mata have not been found leading from 
 the pericardial cavity into these lymphat- 
 ics, nor do these openings exist on the 
 parietal layer. [Salvioli has shown that 
 lymphatic spaces also lie between the mus- 
 cular bundles.] Around the coronary arter- 
 ies of the heart exist lymph vessels and 
 deposits of fat ( Wedl), which lie in the 
 furrows and grooves in the subserosa of the 
 epicardium (visceral layer). 
 
 The endocardium (according to Luschka) 
 does not represent the intima alone, but the 
 wall of a blood vessel. Next the cavity 
 of the heart, it consists of a single layer of 
 polygonal, flat, nucleated endothelial cells. 
 [Under this there is a nearly homogeneous 
 hyaline layer (Fig. 27, a), slightly thicker on 
 the left side, which gives the endocardium 
 its polished appearance.] Then follows, as 
 the basis of tke membrane, a layer of fine 
 elastic fibres — stronger in the auricles, and 
 in some places thereof assuming the char- 
 acters of a fenestrated membrane. Between 
 these fibres a small quantity of connective 
 tissue exists, which is in larger amount and 
 more areolar in its characters next the 
 myocardium. Bundles of non-striped mus- 
 cular fibres (few in the auricles) are 
 scattered and arranged for the most part 
 longitudinally between the elastic fibres. 
 These seem evidently meant to resist the 
 distention which is apt to occur when the 
 heart contracts and great pressure is put 
 
 Lymphatic of the pericardium, epithelium stained with 
 nitrate of silver. 
 
 Fig. 27. 
 
 
 Section of the endocardium, a, hyaline layer ; b, network ot 
 fine elastic fibres ; c, network of stronger elastic fibres : 
 d, myocardium with blood vessels, which do not pass 
 into the endocardium. 
 
STRUCTURE OF THE VALVES. 
 
 upon the endocardium. In all cases where high pressure is put upon walls composed of soft parts, 
 .we always find muscular fibres present, and never elastic fibres alone. No blood vessels occur in 
 /the endocardium (Lander.) 
 
 I The valves also belong to the endocardium — both the semilunar valves of the 
 I aorta and pulmonary artery, which prevent the blood from passing back into the 
 I ventricles, and the tricuspid {right auriculo-ventricular) and mitral {left auriculo- 
 I ventricular), which protect the auricles from the same result. The lower verte- 
 brata have valves in the orifices of the venae cavse which prevent regurgitation into 
 them ; while in birds and some mammals these valves exist in a rudimentary con- 
 dition. 
 
 The valves are fixed by means of their base to resistant fibrous rings, consist- 
 ing of elastic and fibrous tissue. They are formed of two layers— (i) the fibrous, 
 which is a direct continuation of the fibrous rings, and (2) a layer of elastic ele- 
 ments. The elastic layer of the auriculo-ventricular valves is an immediate pro- 
 longation of the endocardium of the auricles, and is directed toward the auricles. 
 The semilunar valves have a thin elastic layer directed toward the arteries, which 
 is thickest at their base. The connective-tissue layer directed toward the ventricle 
 is about half the thickness of the valve itself. 
 
 I Muscular Fibres inthe Valves. — The auriculo-ventricular valves also con tain 
 \ striped muscular fibres {Reid, Gussenbauer). Radiating fibres proceed from the 
 
 Fig. 28. 
 
 Purkinje's fibres isolated with dilute alcohol, c, cell ; f^ striated substance ; n, nucleus. X 300, 
 
 auricles and pass into the valves, which, when the atria contract, retract the 
 valves toward their base, and thus make a larger opening for the passage of the 
 blood into the ventricles ; according to Paladino, they raise the valves after they 
 have been pressed down by the blood current. This observer also described some 
 longitudinal fibres which proceed from the ventricles to enter these valves. There 
 is also a concentric layer of fibres arranged near their point of attachment, and 
 directed more toward their ventricular surface. These fibres seem to contract, 
 sphincter-like, when the ventricle contracts, and thus approximate the base of the 
 valves, and so prevent too great tension being put upon them. The larger chords 
 tendineas also contain striped muscle {Oehl~), while a delicate muscular network 
 exists in the valvula Thebesii and valvula Eustachii. 
 
 Purkinje's Fibres. — This name is applied to an anastomosing system of grayish fibres which 
 exist in the sub-endocardial tissue of the ventricles, especially in the heart of the sheep and ox. The 
 fibres are made up of polyhedral, clear cells, containing some granular protoplasm, and usually two 
 nuclei (Fig. 28). The margin of the cells are striated. Transition forms are found, between these 
 cells and the ordinary cardiac fibres ; in fact, these cells become continuous with the true fully 
 developed cardiac fibres. They represent cells which have been arrested in their development. 
 They are absent in man and the lower vertebrates, but in birds and some mammals they are well 
 marked (Schweigger-Seidel, Ranvier). 
 
 Blood Vessels occur in the auriculo-ventricular valves only where muscular fibres are present, 
 while the semilunar valves are usually devoid of vessels except at their base. The best figures of 
 
AUTOMATIC REGULATION OF THE HEART. 73 
 
 the blood vessels of the valves are given by Langer. The network of lymphatics in the endocar- 
 dium reaches toward the middle of the valves (Eberth and Belajeff). 
 
 Weight of the Heart. — According to W. Miiller the proportion between the weight of the 
 body and the heart in the child, and until the body reaches 40 kilos., is 5 grms. of heart substance 
 to I kilo of body weight ; when the body weight is from 50 to 90 kilos , the ratio is 1 kilo, to 4 
 grms. of heart substance ; at 100 kilos. 3.5 grms. As age advances the auricles become stronger. 
 The right ventricle is half the weight of the left. The weight of the heart of an adult man is about 
 9 oz. (1 oz. = 29.2 grms.) ; female = Sj4 oz. (Clendinning, as a mean of 400 observations). 
 [According to Laennec the heart is about the size of the closed fist of the individual.] Blosfeld and 
 Dieberg give 346 grms. for the male, and 310 to 340 grms. for the female heart. The specific gravity 
 of the heart muscle is 1.069 {Kapff). The thickness of the left ventricle in the middle in man is 
 11.4 mm., and in woman 11. 15 ; that of the right is 4 I and 3.6 mm. respectively. The circumfer- 
 ence of the tricuspid orifice in man is 1 18 mm., and in woman 1 1 1.2 mm.; the corresponding num- 
 bers for the mitral being 106. 1 and 97. The circumference of the pulmonary artery = 75.5 mm. 
 (man), and 74.7 mm. (woman); aorta= 71. 1 mm. (man), and 68x> mm. (woman). Sup. vena 
 cava (circumference) = 18 to 27 mm., the inferior from 27 to 36 mm. The diameter of the pul- 
 monary veins is 13.53 '° '5-79 mm - [The sizes of these orifices are best measured by means of 
 cones or orifice gauges of known diameter.] 
 
 47. AUTOMATIC REGULATION OF THE HEART.— Coronary Vessels.— Many 
 observations have been made to ascertain whether the orifices of the coronary arteries are covered 
 by the semilunar valves during contraction of the left ventricle [Thebesius, tjjq; Briicke, 1854), 
 or whether they are permanently open (Morgagni, 1723 ; Hyrtl, 1835) (Fig. 29). 
 
 Anatomical Investigations. — The two coronary arteries arise from the 
 beginning of the aorta in the region of the sinus of Valsalva. [Hyrtl asserts that 
 the branches of the coronary arteries do not anastomose, but this is certainly not 
 the case (Krause, L. Langer). West has injected the one artery from the other.] 
 The position of origin varies — (1) either the origins lie within the sinus, or (2) 
 their openings are only partially reached by the margins of the semilunar valves 
 (which is usually the case in the left coronary artery of man and the ox), or (3) 
 their orifices lie clear above the margins of the valyes. Post-mortem observations 
 seem to show that during contraction of the ventricle it is very improbable that 
 the semilunar valves constantly cover the origin of the coronary arteries. 
 
 The Automatic Regulation of the Heart. — Briicke attempted to show 
 that during the systole, or contraction of the ventricle, the semilunar valves 
 covered the openings of the coronary arteries, so that these vessels could be filled 
 with blood only during the diastole or relaxation of the ventricle. To him it 
 seemed that (a) the diastolic filling of the coronary arteries would help to dilate 
 the ventricles ; (J>) on the contrary, a systolic filling of these arteries would oppose 
 the contraction, because the systolic filling and expulsion of the blood from the 
 coronary arteries would diminish the force of the ventricular contraction. [To 
 this supposed arrangement Briicke gave the name "Selbststeuerung," which may 
 be rendered as above, or as "self-controlling" action of the heart by the aortic 
 valves.] 
 
 Arguments Against Brucke's View. — The following considerations militate against this 
 theory: (1) Filling the coronary vessels under a high pressure in a dead heart causes a diminution 
 of the ventricular cavity (v. IVittich). (2) The chief trunks of the coronary arteries lie in loose 
 subpericardial fatty tissue in the cardiac sulci, hence a dilatation of the ventricle through this agency 
 is most unlikely [Landois). (3) Experiments on animals have shown that a coronary artery spouts, 
 like all arteries, during the systole of the ventricle. Von Ziemssen found that in the case of a 
 woman (Serafin), who had a large part of the anterior wall of the thorax removed by an operation, 
 the heart being covered only by a thin membrane, the pulse in the coronary arteries was synchronous 
 with the pulse in the pulmonary artery. H. N. Martin and Sedgwick placed a manometer in 
 connection with the coronary artery, and another with the carotid, in a large dog, and they found 
 that the pulsations occurred simultaneously. When a coronary artery is divided, the blood flows 
 out continuously, but undergoes acceleration during the systole of the ventricles (Endemann, Perls). 
 (4) If a strong intermittent current of water be allowed to flow through a sufficiently wide lube into 
 the left auricle of a fresh pig's heart, so that the water passes into the aorta, and if the aorta be 
 provided with a vertical tube, the water flows continuously from the coronary arteries, and is 
 accelerated during the systole. (5) It is exceedingly improbable that the coronary arteries should 
 be filled during the diastole while all the other arteries are filled during systole of the ventricle. 
 (6) There is always a sufficient quantity of blood in the sinus of Valsalva to fill the arteries during 
 
74 LIGATURE OF THE CORONARY ARTERIES. 
 
 the first part of the systole. (7) The valves, when raised, are not applied directly to the aortic wall 
 (Hamberger, Riidinger) even by the most energetic pressure from the ventricle {Sandborg and 
 Worm Miiller). (8) Observations on voluntary muscles have shown that the small arteries dilate 
 during contraction of the muscle, and the blood stream is accelerated. (9) By the systolic filling 
 of the aorta the arterial path is elongated — this elastic distention is compensated before the diastole 
 occurs. By the recoil of the aortic walls the layer of blood in them is driven backward and closes 
 the valves (Ceradini). According to Sandborg and Worm Miiller, the semilunar valves close just 
 after the ventricles have begun to relax, which agrees with the curve obtained from the cardiac 
 impulse (Fig. 32, A). 
 
 During the systole, the small arterial trunks lying next the ventricular cavities 
 have to bear a higher pressure than that borne by the aorta, and their lumen must 
 be compressed during the systole so that their contents are propelled toward the 
 veins. 
 
 Peculiarities of the Cardiac Blood Vessels — The capillary vessels of the myocardium are 
 very numerous, corresponding to the energetic activity of the heart. Where they pass into veins, 
 several unite at once to form a wide venous trunk whereby an easy passage is offered to the blood . 
 The veins are provided with valves so that (1) during systole of the right auricle the venous stream 
 is interrupted ; (2) during contraction of the ventricles the blood in the coronary veins is similarly 
 accelerated as in the veins of muscles. 
 
 The coronary arteries are characterized by their very thick connective tissue and elastic intima, 
 which perhaps accounts for the frequent occurrence of atheroma of these vessels (Henle). Some 
 observers (Hyrtl and Henle) maintain that the coronary arteries do not anastomose, but this is 
 denied by Langer and Krause. Many of the small lower vertebrates have no blood vessels in their 
 heart muscle e.g., frog (Hyrtl). 
 
 Coronary Circulation. — The phenomena produced by partial obliteration or 
 ligature of the coronary arteries are most important. In man analogous conditions 
 occur, as in atheroma or calcification of these arteries. 
 
 Ligature of the Coronary Arteries. — See and others ligatured the coronary 
 arteries in a dog, and found that after two minutes the cardiac contractions gave 
 place to twitchings of the muscular fibres, and ultimately the heart ceased to beat. 
 Ligature of the anterior coronary artery alone, or of both its branches, is sufficient 
 to produce the result. If the ordinary arteries be compressed or tied in a rabbit, 
 in the angle between the bulbus aortas and the ventricle, the heart's action is soon 
 weakened, owing to the sudden anaemia and to the retention of the decomposition 
 products of the metabolism in the heart muscle (z>. Bezold, Erichsen). Ligature 
 of one artery first affects the corresponding ventricle, then the other ventricle, 
 and, last of all, the auricles. Hence, compression of the left coronary artery 
 (with simultaneous artificial respiration in a curarized animal) causes slowing of 
 the contractions, especially of the left ventricle, while the right one at first 
 contracts more quickly, and then, gradually, its rhythm is slowed. The contrac- 
 tions of the left ventricle are not only slowed but also weakened, while the right 
 pulsates with undiminished force. Hence it follows that, as the left half of the 
 heart cannot expel the blood in sufficient quantity, the left auricle becomes filled, 
 while the right ventricle, not being affected, pumps blood into the lungs. (Edema 
 of the lungs is produced by the high pressure in the pulmonary circulation, which 
 is propagated from the right heart through the pulmonary vessels into the left 
 auricle {Samuelson and Grilnhagen). According to Sig. Mayer, protracted dyspnoea 
 causes the left ventricle to beat more feebly sooner than the right, so that the left 
 side of the heart becomes congested. Perhaps this may explain the occurrence of 
 pulmonary oedema during the death agony. 
 
 Cohnheim and v. Schulthess-Rechberg found, after ligature of one of the large branches of a 
 coronary artery in a large dog, that at the end of a minute the pulsations became discontinuous; 
 several, as it were, do not occur. This intermittence becomes more pronounced, the two sides of 
 the heart do not contract simultaneously (arhythmia), the heart beats more slowly, and the blood 
 pressure falls. Suddenly, about 105 seconds after the ligature is applied, both ventricles cease to 
 beat, and there is the greatest fall of the blood pressure. After 10 to 20 seconds, twitching move- 
 ments occur in the ventricles, while the auricles pulsate regularly, and may continue to do so for 
 many minutes, but the ventricles cease to beat altogether after 50 seconds. According to Lukjanow, 
 
EVENTS DURING A CARDIAC CYCLE. 75 
 
 there is a peristaltic condition which operates upward and downward, and occurs in the period 
 between the regular contraction and the twitching vibratory movement. 
 
 Pathological. — In so-called sclerosis of the coronary arteries, in old age, there are attacks of 
 diminished cardiac activity, weakness of the heart, an altered rhythm and frequency, with con- 
 sequent breathlessness ; there may also be loss of consciousness, congestions, and attacks of pul- 
 monary oedema. 
 
 48. MOVEMENTS OF THE HEART.— Cardiac Revolution.— The 
 
 movement of the heart is characterized by an alternate contraction and relaxation 
 of the cardiac walls. The total cardiac movement is called a " cardiac revolu- 
 tion," or a "cardiac cycle," and consists of three acts — the contraction or 
 systole of the auricles, the contraction or systole of the ventricles, and the pause 
 (Fig. 43). During the pause the auricles and ventricles are relaxed; during the 
 contraction of the auricles the ventricles are at rest ; while during the contraction 
 of the ventricles the auricles are relaxed. The rest during the phaseof relaxation 
 is called the diastole. The following is the sequence of events in the heart during 
 a cardiac revolution : — 
 
 EVENTS DURING A CARDIAC REVOLUTION. 
 
 (A) The Blood Flows into the Auricles, and thus distends them and 
 the auricular appendices. This is caused by — 
 
 (1) Tat pressure of the blood in the venae cavas (right side) and the pulmonary 
 veins (left side) being greater than the pressure in the auricles. 
 
 (2) The elastic traction of the lungs (§ 68) which, after complete systole of the 
 auricles, pulls asunder the now relaxed and yielding auricular walls. The auricular 
 appendages are also filled at the same time, and they act to a certain extent as 
 accessory reservoirs for the large supply of blood streaming into the auricles. 
 
 (B) The Auricles Contract, and we observe in rapid succession — 
 
 (1) The contraction and emptying of the auricular appendix toward the atrium. 
 Simultaneously the mouths of the veins become narrowed {Haller, Nysten) owing 
 to the contraction of their circular muscular fibres (more especially the superior 
 vena cava and the pulmonary veins). 
 
 (2) The auricular walls contract simultaneously toward the auriculo-ventricular 
 valves and the venous orifices, whereby 
 
 (3) The blood is driven into the relaxed ventricles, which are considerably dis- 
 tended thereby. 
 
 The contraction of the auricles is followed by 
 
 (a) A slight stagnation of the blood in the large venous trunks, as can be easily 
 observed in a rabbit after division of the pectoral muscles so as to expose the junc- 
 tion of the jugular with the subclavian vein. There is no proper regurgitation of 
 the blood, but only a partial interruption of the inflow into the auricles, because, 
 as already mentioned, the mouths of the veins are contracted, and because the 
 pressure in the superior vena cava and in the pulmonary veins soon holds in equili- 
 brium any reflux of blood ; and lastly, because any reflux into the cardiac veins is 
 prevented by valves. The movement of the. heart causes a regular pulsatile phe- 
 nomenon in the blood of the venae cavae, which under abnormal circumstances 
 may produce a venous pulse (see§ 99). 
 
 (0) The chief motor effect of the contraction of the auricles is the dilatation of 
 the relaxed ventricle, which has already been dilated to a slight extent by the 
 elastic traction of the lungs. 
 
 Aspiration of the Ventricles. — The dilatation of the ventricles has been ascribed to the elas 
 ticity of the muscular walls — the strongly contracted ventricular walls (like a compressed india- 
 rubber bag), in virtue of their elasticity, are supposed, in returning to their normal resting form, to 
 suck in or aspirate the blood under a negative pressure ; this power on the part of the ventricle is 
 not great (p. 77). 
 
 (c) when the ventricles are distended by the inflowing blood, the auriculo- 
 ventricular valves are floated up, partly by the recoil or reflection of the blood 
 
76 
 
 EVENTS DURING A CARDIAC CYCLE. 
 
 from the ventricular wall, and partly owing to their lighter specific gravity, 
 whereby they easily float into a more or less horizontal position. The valves are 
 also raised to a slight extent by the longitudinal muscular fibres, which pass from 
 the auricles into the cusps of the valve (Paladind). 
 
 (C) The Ventricles now Contract, and simultaneously the auricles relax, 
 whereby 
 
 (i) The muscular walls contract forcibly from all sides, and thus diminish the 
 ventricular cavity. 
 
 (2) The blood is at once pressed against the under surface of the auriculo- 
 ventricular valves, whose curved margins are opposed to each other like teeth, 
 
 Fig. 29. 
 
 Gypsum cast of the ventricles of the human heart — viewed from behind and above ; the walls have been removed, and 
 only the fibrous rings and the auriculo-ventricular valves are retained. L, left, R, right ventricle ; S, position of 
 septum ; F, left fibrous ring, with mitral valve closed ; D , right fibrous ring, with tricuspid closed ; A, aorta, with 
 the left (C t ) and right (C) coronary arteries ; S, sinus of Valsalva; P, pulmonary artery. 
 
 and are pressed hermetically against each other {Sandborg and Worm Muller) 
 (Fig. 29). It is impossible for the blood to push the cusps backward into the 
 auricle, as the chordae tendineae hold fast their margins and surfaces like a taut 
 sail. The margins of the neighboring cusps are also kept in apposition, as the 
 chordae tendineae from one papillary muscle always pass to the adjoining edges of 
 two cusps {John Reid^). The extent to which the ventricular wall is shortened is 
 compensated by the contraction of the papillary muscle, and also of the large 
 muscular chordae, so that the cusps cannot be pushed into the auricle (p. 82). 
 When the valves are closed their surfaces are horizontal, so that, even when the 
 
PATHOLOGICAL DISTURBANCES OF CARDIAC ACTION. 77 
 
 ventricles are contracted to their greatest extent, there remains in the supra- 
 papillary space a small amount of blood which is not expelled (Sandborg and 
 Worm Muller). 
 
 (3) Opening of the Semilunar Valves. — When the pressure within the ventricle 
 exceeds that in the arteries, the semilunar valves are forced open and stretched 
 like a sail across the pocket-like sinus, without, however, being firmly or directly 
 applied to the wall of the arteries (pulmonary and aorta), and thus the blood 
 enters the arteries. 
 
 Negative Pressure in the Ventricle. — Goltz and Gaule found that there was a negative 
 pressure of 23.5 mm. Hg (dog) in the interior of the ventricle during a certain phase of the heart's 
 action. This they determined by a maximal and minimal manometer. They surmised that this 
 phase coincided with the diastolic dilatation, for which they 
 assumed a considerable power of aspiration. Marey observed a jr IG 
 
 similar condition and called if'vacuite postsystolique," but thought 
 that it coincided with the end of the systole ; while Moens is of 
 opinion that this negative pressure within the ventricle obtains 
 shortly before the systole has reached its height, i. e., just before the 
 inner surface of the ventricles and the valves, after the blood. is ex- 
 pelled, are nearly in apposition. He explains this aspiration as 
 being due to the formation of an empty space in the ventricle 
 caused by the energetic expulsion of the blood through the aorta 
 and pulmonary artery. 
 
 (D) Pause. — As soon as the ventricular contraction 
 ends, and the ventricles begin to relax, the semilunar 
 valves close (Fig. 30). The diastole of the ventricles is 
 followed by the pause. Under normal circumstances 
 the right and left halves of the heart always contract or The closed semilunar valve of the 
 
 i -r i 1 ■ 1, , pulmonary artery seen from 
 
 relax uniformly and simultaneously. below. 
 
 4g. PATHOLOGICAL DISTURBANCES OF CARDIAC ACTION.— Cardiac 
 Hypertrophy. — All resistances to the movement of the blood through the various chambers 
 of the heart, and through the vessels communicating with it, cause a greater amount of work 
 to be thrown upon the portion of the heart specially related to this part of the circulatory 
 system ; consequently, there is produced an increase in the thickness of the muscular walls and 
 dilatation of the heart. If the resistance or obstacle does not acr upon one part of the heart alone, 
 but on parts lying in the onward direction of the blood stream, these parts also subsequently 
 undergo hypertrophy. If in addition to the muscular thickening of a part of the heart the cavity 
 is simultaneously dilated, it is spoken of as eccentric hypertrophy or hypertrophy with dilatation. 
 
 The obstacles most likely to occur in the blood vessels are narrowing of the lumen or want of 
 elasticity in their walls ; in the heart, narrowing of the arterial or venous orifices or insufficiency or 
 incompetency of the valves. Incompetency of the valves forms an obstruction to the movement of 
 the blood, by allowing part of the blood to flow back or regurgitate, thus throwing extra work upon 
 the heart. 
 
 Thus arise (1) Hypertrophy of the left ventricle, owing to resistance in the area of the sys- 
 temic circulation, especially in the arteries and capillaries — not in the veins. Among the causes 
 are, constriction of the orifice or other parts of the aorta, calcification, atheroma and want of elas- 
 ticity of the large arteries and irregular dilatations in their course (Aneurisms) ; insufficiency of the 
 aortic valves, in which case the same pressure always obtains within the ventricle and in the aorta ; 
 and lastly, contraction of the kidneys, so that the excretion of water by these organs is diminished. 
 Even in mitral insufficiency compensatory hypertrophy of the left ventricle must occur, owing to 
 the hypertrophy of the left atrium in consequence of the increased blood pressure in the pulmonary 
 circuit. 
 
 (2) Hypertrophy of the left auricle occurs in stenosis of the left auriculo- ventricular orifice, or 
 in insufficiency of the mitral valve, and it occurs also as a result of aortic insufficiency, because the 
 auricle has to overcome the continual aortic pressure within the ventricle. 
 
 (3) Hypertrophy of the right ventricle occurs (a) when there is resistance to the blood stream 
 through the pulmonary circuit. The resistance may be due to (a) obliteration of large vascular 
 areas, in consequence of destruction, shrinking or compression of the lungs, and the disappearance 
 of numerous capillaries in emphysematous lungs; (£) overfilling of the pulmonary circuit with 
 blood, in consequence of stenosis of the left auriculo-ventricular orifice, or mitral insufficiency — 
 consequent upon hypertrophy of the left auricle resulting from aortic insufficiency, (b) Hyper- 
 trophy of the right ventricle will also occur when the valves of the pulmonary artery are insufficient, 
 thus permitting the blood to flow back into the ventricle, so that the pressure within the pulmonary 
 artery prevails within the right ventricle (very rare). 
 
78 SYNCOPE, CARDIAC IMPULSE. 
 
 (4) Hypertrophy of the right auricle occurs in consequence of the last named condition, and 
 also from stenosis of the tricuspid orifice, or insufficiency of the tricuspid valve (rare). If several 
 lesions occur simultaneously, the result is complex. 
 
 Artificial Injury to the Valves. — O. Rosenbach has made experiments on the action of the 
 heart when its valves are injured artificially. If the aortic valves are perforated, with or without 
 simultaneous injury to the mitral or tricuspid valves, the heart does more work; thus the physical 
 defect is overcome for a time, so that the blood pressure does not fall. The heart seems to have a 
 store of reserve energy, which is called into play. Soon, however, dilatation takes place, on account 
 of the regurgitation of the blood into the heart. Hypertrophy then occurs, but the compensation, 
 meanwhile, must be obtained through the reserve energy of the heart. 
 
 Impeded Diastole. — Among causes which hinder the diastole of the heart are— copious effusions 
 into the pericardium, or pressure of tumors upon the heart. The systole is greatly interfered with 
 when the heart is united to the pericardium and to the connective tissue in the mediastinum. As a 
 consequence, the connective tissue, and even the thoracic wall, are drawn in during contraction of 
 the heart, so that there is a retraction of the region of the apex beat during systole, and a protrusion 
 of this part during the diastole. 
 
 [Palpitation is a symptom indicating, generally, very rapid and quick action of the heart, the 
 pulsations often being unequal in time and intensity, while the person is generally conscious of the 
 irregularity of the cardiac action. It may be due to some organic condition of the heart itself, 
 especially where the cardiac muscles are weak, in cases of dilatation and hypertrophy of the left 
 ventricle where the heart is gradually becoming unable to overcome the resistances offered to its 
 work, and especially during exertion, when the heart is taxed above its strength. It may also occur 
 where the blood pressure is low, as in anaemia, so that the heart contracts quickly, there being little 
 resistance opposed to its action. The excitability of the cardiac muscle may be increased, as in 
 fatty heart, when very slight exertion may excite it, often in a paroxysmal way. In other cases it 
 is nervous in its origin, being either direct or reflex. In very emotional and excitable people 
 (especially in women), it is easily set up, and in some people it may be produced reflexly by gastric 
 or intestinal irritation or dyspepsia. It also frequently results from excesses of all kinds and the 
 over-use of tobacco.] 
 
 [Action of Drugs. — The remedies to be used obviously depend on the cause. Where the 
 blood pressure is low, as in anasmia, digitalis and iron will do good ; the former by increasing the 
 blood pressure, and the latter by improving the general nutrition of the body and the blood in 
 particular. In neurotic cases, cardiac sedatives are indicated, while in cases due to indigestion, 
 hydrocyanic acid is useful (Brunton)l\ 
 
 [Fainting or Syncope. — In fainting, the person loses consciousness, owing to a sudden arrest 
 of the blood supply to the brain, the face is pallid, the respiration is feeble or ceases, while the 
 heart beats buc feebly or not at all. The defective supply of blood to the brain may depend upon 
 sudden arrest of the heart's action, caused, it may be, by a fright, or the heart's action may be 
 arrested reflexly. Any cause which suddenly diminishes the blood pressure may produce it, or 
 when pressure is suddenly removed from the large vessels, as in tapping the abdomen in ascles, 
 without at the same time giving sufficient support to the abdominal viscera. . When a person has 
 been long in the recumbent position, on being rapidly set up in bed, he may faint. In some forms 
 of heart uisease, sudden exertion or change of position may produce it.] 
 
 [Treatment. — The object is to restore consciousness and the action of the heart.- Place the 
 person in the horizontal position, with the head low, even lower than the body, and do not support 
 it with pillows. Dashing cold water in the face, so as to stimulate the fifth nerve, usually succeeds 
 in causing the person to take a deep inspiration. In other cases, a sniff of smelling salts or ammonia, 
 acting through the nasal branch ol the fifth nerve, will excite the cardiac and respiratory functions 
 
 M36*)-]- 
 
 50. THE APEX BEAT, THE CARDIOGRAM, CHANGES IN 
 THE SHAPE OF THE HEART.— Cardiac Impulse.— By the term 
 "apex beat," or cardiac impulse, is understood, under normal circumstances, 
 an elevation (perceptible to touch and sight) in a circumscribed area of the fifth 
 left intercostal space, caused by the movement of the heart. [The apex beat is 
 felt in the fifth left intercostal space, 2 inches below the nipple and 1 inch to its 
 sternal side, or at a point 2 inches to the left of the sternum.] The impulse is 
 more rarely felt in the fourth intercostal space, and it is much less distinct when 
 the heart beats against the fifth rib itself. The position and force of the cardiac 
 impulse vary with changes in the position of the body. 
 
 [The cardiac impulse is synchronous with the systole of the heart, but although this name 
 and apex beat are frequently used as synonymous terms, it is to be remembered that the impulse 
 may be caused by different parts of the heart being in contact with the chest wall. The cardiac 
 impulse is usually higher than normal in children, while it is lower during inspiration than 
 expiration.] 
 
THE CARDIOGRAM. 
 Fig. 31. 
 
 79 
 
 Various cardiographs. A, original form as used by Marey : B, improved form by Marey ; C, pansphygmograph 
 of Brondgeest ; D, cardiograph of Burdon-Sanderson ; E, that of Grummach and v. Knoll. 
 
 Fig. 32. 
 
 Curves taken from the apex beat. A, normal curve from man ; B, from a dog ; C, very rapid curve from a dog ; 
 D and E, normal curves from a man, registered on a vibrating glass plate where each indentation = 0.01613 
 sec. In all the curves, ad means contraction of the auricles ; be, ventricular systole ; d, closure of the aortic 
 valves ; e, closure of the pulmonary artery valves ; «/, relaxation of diastole of the ventricle. 
 
80 
 
 THE CARDIOGRAM. 
 
 [Methods — To obtain a curve of the apex beat or a cardiogram, we may use one or other of 
 the following cardiographs (Fig. 3j). Hg. 31, A, is the first form used by Marey, and it consists of 
 an oval wooden capsule applied in an air-tight manner over the apex beat. The disk, /, capable 
 of being regulated by the screw, s, presses upon the region of the apex beat, while t is a tube which 
 may be connected with a recording tambour (Fig. 40). B is an improved form of the instrument, 
 consisting, essentially, of a tambour, while attached to the membrane is a button, p, to be applied 
 over the apex beat. The movements of the air within the capsule are communicated by the tube, 
 /, to a recording tambour. Fig. 31, C, is the pansphygmograph of Brondgeest, which consists of 
 a Marey's tambour, in an iron horse-shoe frame, and adjustable by means of a screw, s. Burdon- 
 Sanderson's cardiograph is shown in T>. The button, p, carried by the spring, e, does not rest 
 upon the caoutchouc membrane, but on an aluminium plate attached to it. The apparatus is adjusted 
 to the chest by three supports. Fig. 31, E, shows a modified instrument on the same principle, by 
 Grummach and v. Knoll. In all these figures, the t indicates the exit tube, communicating with a 
 recording tambour (Fig. 40). D and E may be used for other purposes, eg., for the pulse, so that 
 they are polygraphs. See also Fig. 72.] 
 
 Fig. 33. 
 
 I. Schematic horizontal section through the heart and lungs, and the thoracic walls, to show the change of shape 
 which the hase of the heart undergoes during contraction of the ventricle— i, 2, transverse diameter of the ven- 
 tricle during diastole ; c, position of the thoracic wall during diastole ; a, b, transverse diameter of the heart 
 during systole, with e, the position of the anterior thoracic wall during systole. II. Side view of the heart — /, 
 apex during diastole; p, the same during systole (C. Ludwig and Henke). 
 
 Fig. 32, A, shows the cardiogram or the impulse curve of the heart of a healthy 
 man ; B, that of a dog, obtained by means of a sphygmograph. In both the 
 following points are to be noticed : a b, corresponds to the time of the pause and 
 the contraction of the auricles. As the atria contract in the direction of the axis 
 of the heart from the right and above toward the left and below, the apex of the 
 heart moves toward the intercostal space. The two or three smaller elevations are 
 perhaps caused by the contractions of the ends of the veins, the auricular appendi- 
 ces, and the atria themselves. 
 
 Some observers ascribe the small elevations occurring before b to the filling of the ventricle during 
 the diastole, whereby it is pressed against the intercostal space (Maurer, Griitzner). 
 
 The portion b c, which communicates the greatest impulse to the instrument and 
 also to one's hand when it is placed on the apex beat, is caused by the contraction 
 
CAUSE OF THE CARDIAC IMPULSE. 81 
 
 of the ventricles, and during it the first sound of the heart occurs. Frequently, but 
 erroneously, the cardiac impulse has been ascribed "to the contraction of the 
 ventricles alone. It, however, is due to all those conditions which cause an eleva- 
 tion in the region of the apex beat. 
 
 The cause of the ventricular impulse has been much discussed. It 
 depends upon the following : — 
 
 (i) The base of the heart (auriculo-ventricular groove) represents during 
 diastole a transversely-placed ellipse, while during contraction it has a more circular 
 figure. Thus, the long diameter of the ellipse is diminished in the cat from 28 to 
 22.5 mm. (C. Ludwig); the small diameter is increased (-fa to \), while the base 
 is brought nearer to the chest wall {Arnold, Ludwig), (Fig. 33, I). This alone 
 does not cause the impulse, but the basis of the heart, being hardened during the 
 systole and brought nearer to the chest wall, allows the apex to execute the 
 movement which causes the impulse [compare p. 82]. 
 
 (2) During relaxation, the ventricle lies with its apex obliquely downward, and 
 with its long axis in an oblique direction — so that the angles formed by the axis 
 of the ventricles with the diameter of the base are unequal — represents a regular 
 cone, with its axis at right angles to its base. Hence, the apex must be erected 
 from below and behind, forward and upward {Harvey — "cor sese erigere"), and 
 when hardened during systole presses itself into the intercostal space {Ludwig), 
 
 (Fig. 33,11). 
 
 (3) The ventricles undergo during systole a slight spiral twisting on their long 
 axis ("lateralem inclinationem " — Harvey), so that the apex is brought from 
 behind more forward, and thus a greater portion of the left ventricle is turned to 
 the front. This rotation is caused by the muscular fibres of the ventricles, which 
 proceed from that part of the fibrous rings between the auricles and ventricles 
 which lies next the anterior thoracic wall. The fibres pass from above obliquely 
 downward, and to the left, and also run in part upon the posterior surface of the 
 ventricles. When they contract in the axis of their direction, they tend to raise 
 the apex, and also to bring more of the posterior surface of the heart in relation 
 with the anterior thoracic wall {Harvey, Kurschner, Wilckens). This rotation is 
 favored by the slightly spiral arrangement of the aorta and pulmonary artery 
 {Kornitzer). 
 
 These are the most important causes, but minor causes are as follows : — 
 
 (4) The "reaction impulse'" or "recoil" is that movement which the ventricles 
 are said to undergo (like an exploded gun or rocket), at the moment when the 
 blood is discharged into the aorta and pulmonary artery, whereby the apex goes 
 in the opposite direction, i. e., downward and slightly outward {Alderson {1825), 
 Gutbrod, Skoda, Hiffelsheim). Landois, however, -has shown that the mass of 
 blood is discharged into the vessels 0.08 of a second after the beginning of the 
 systole, while the cardiac impulse occurs with the first sound. 
 
 (5) When the blood is discharged into the aorta and pulmonary artery, these 
 vessels are slightly elongated, owing to the increased blood pressure {Senac). As 
 the heart is suspended from above by these vessels, the apex is pressed slightly 
 downward and forward toward the intercostal space (?). 
 
 Guttmann and Jahn observed that the cardiac impulse disappeared after suddenly ligaturing the 
 aorta and pulmonary artery, while Chauveau and Rosenstein maintain that it persists after this 
 operation. 
 
 As the cardiac impulse is observed in the empty hearts of dead animals, (4) and 
 (5) are certainly of only second-rate importance. Filehne and Pentzoldt maintain 
 that the apex during systole does not move to the left and downward, as must be 
 the case in (4) and (5), but that it moves upward and to the right — a result 
 corroborated by v. Ziemssen. 
 
 [Barr attributes the cause of the impulse to the rigidity or hardening of the ventricle during 
 systole, to the rotatory movement and lengthening downward of the blood column in the aorta and 
 6 
 
82 CHANGE IN SHAPE OF HEART. 
 
 pulmonary artery, while toward the end of the systole the maximum of recoil takes place and also 
 contributes to cause it.] 
 
 It is to be remembered that as the apex is always applied to the chest wall, separated from it 
 merely by the thin margin of the lung, it only presses against the intercostal space during systole 
 
 (Kiwisch). 
 
 After the apex of the curve, c, has been reached at the end of the systole, the 
 curve falls rapidly, as the ventricles rapidly become relaxed. In the descending 
 part of the curve, at (/and e, are two elevations, which occur simultaneously with 
 the second sound. These are caused by the sudden closure of the semilunar valves, 
 which, occurring suddenly, is propagated through the axis of the ventricle to its 
 apex, and thus causes a vibration of the intercostal space ; d corresponds to the 
 closure of the aortic valves, and e to the closure of the pulmonary valves. The 
 closure of the valves in these two vessels is not simultaneous, but is separated by 
 an interval of 0.05 to o 09 sec. The aortic valves close sooner on account of the 
 greater blood pressure there (Landois {1876), Olt and Haas, Malbranc, Maurer, 
 Griiizner, Langendorff, v. Ziemssen, and Ter Gregorianz). 
 
 Complete diastolic relaxation of the ventricle occurs from e to/ in the curve. 
 It is clear, then, that the cardiac impulse is caused chiefly by the contraction of the 
 ventricles, while the auricular systole and the vibration caused by the closure of 
 the semilunar valves are also concerned in its production. 
 
 [Change in Shape of Heart. — The experiments of Ludwig and Hesse on 
 the heart of the dog show that the shape of the ventricles varies remarkably 
 
 Fig. 34. Fig. 35. 
 
 Projection of a dog's heart. Left lateral surface. 
 
 Posterior surface . 
 
 in systole and diastole, and that the shape of the heart as found post-mortem is 
 not its natural shape.] 
 
 [Method. — Bleed a dog rapidly .from the carotids, defibnnate the blood, expose the heart, tie 
 graduated straight tubes into the pulmonary artery and aorta, and ligature the auricular vessels. 
 Pour the blood into the heart until it is dilated under a pressure equal to the mean arterial pressure 
 (150 mm.). The ventricles are in the diastolic phase, the auricles still pulsate. A plaster cast is 
 now rapidly made of the ventricles. This represents the diastolic phase. To obtain what may be 
 regarded as the systolic phase, a heart, similarly prepared but emptied of blood, is suddenly 
 plunged into a hot (50° C), saturated solution of potassic bichromate, when the heart gives one 
 rapid and final contraction and remains permanently contracted, owing to the heat rigor, its proteids 
 being coagulated (§ 295). This is the systolic phase. Little pins with twisted points are pre- 
 viously inserted in the organ, to mark certain parts of both hearts, for comparison.] 
 
 [In diastole, the shape of the ventricle is hemispheroidal, the apex being 
 rounded, while the posterior surface is flatter than the anterior (Fig. 34). In the 
 plane of the ventricular base, the greatest diameter is from right to left, and the 
 shortest from base to apex. The conus arteriosus is above the plane of the base. 
 During systole, the apex is more pointed, the ventricle more conical, while all the 
 diameters in the plane of the base are equally diminished, hence the vertical 
 measurement from base to apex is longer now than either of the diameters at the 
 base (Fig. 35). The conus arteriosus sinks toward the plane of the base, while 
 the base of the ventricle becomes more circular, so that the difference of the 
 
TIME OCCUPIED BY THE CARDIAC MOVEMENTS. 
 
 83 
 
 curvatures of the anterior and posterior surfaces vanishes (Fig. 36). In all these 
 figures the shaded part represents diastole and the clear part systole. The most 
 remarkable point is that the vertical measurement remains unchanged. This 
 refers to the left ventricle, which, of course, forms the apex ; the right is shortened. 
 The plane of the ventricular base in systole is about one-half of what it is in dias- 
 tole, and as shown in Fig. 38. Thus the heart is diminished in all its diameters 
 except one, the arterial orifices are scarcely affected, while the area of the auriculo- 
 ventricular orifices (M.T.) is diminished about one-half (Fig. 37). This is most 
 important in connection with the closure of the auriculo-ventricular valves ; as it 
 shows that the muscular fibres of the heart, by diminishing these orifices during 
 systole, greatly aid in the perfect closure of these valves. Thus we explain why 
 defective nutrition of the cardiac muscle may give rise to incompetency of these 
 valves, without the valves themselves being diseased (Macalister).~\ 
 
 [In order to account for the vertical diameter remaining unchanged, we may 
 represent the ventricular fibres as consisting of three layers, viz., an inner and 
 outer set, more or less longitudinal, and a middle set, circular. Both sets will 
 tend when they contract to diminish the cavity, but the shortening of the longi- 
 tudinal layers is compensated for by the contraction, i. e., the elongation pro- 
 duced by the circular set.] 
 
 [In order to obtain the shape of the cavities, dogs were taken of the same litter and as nearly 
 alike as possible. One heart was filled with blood, as already described, and placed in a cool solu- 
 
 FiG. 36. 
 
 Fig. 37. 
 
 Fig. 38. 
 
 Anterior surface. 
 
 A, aorta ; PA, pulmonary 
 artery ; M, mitral, and 
 T, tricuspid orifice. 
 
 Projection of the base in sys- 
 tole and diastole RV, 
 right, and LV, left ven- 
 tricle {LudivigandHesie). 
 
 tion of potassic bichromate, whereby it was slowly hardened in the diastolic form, while the othe 
 was plunged, as before, in a hot solution. Casts were then made of the cavities.] 
 
 51. THE TIME OCCUPIED BY THE CARDIAC MOVEMENTS.— Methods.— 
 
 The time occupied by the Various phases of the movements of the heart may be determined by study- 
 ing the apex-beat curve. 
 
 (1) If we know at what rate the plate on which the curve was obtained moved during the experi- 
 ment, of course all that is necessary is to measure the distance, and so calculate the time occupied 
 by any event (see Pulse, \ 67). 
 
 (2) It is preferable, however, to cause a tuning fork, whose rate of vibration is known, to write 
 its vibrations under the curve of the apex beat, or the curve may be written upon a plate attached to 
 a vibrating tuning fork (Fig. 32, D, E). Such a curve contains fine teeth, caused by the vibrations 
 of the tuning fork. D and E are curves obtained from the cardiac impulse in this way from healthy 
 students. In D the notch d\s not indicated. Each complete vibration of the tuning fork, reckoned 
 from apex to apex of the teeth = 0.01613 second, so that it is simply necessary to count the number 
 of teeth and multiply, to obtain the time. The values obtained vary within certain limits, even in 
 health. 
 
 Pause and Contraction of Auricles. — The value of a b = pause -f con- 
 traction of the auricles, is subject to the greatest variation, and depends chiefly 
 upon the number of heart beats per minute. The more quickly the heart beats, 
 the smaller is the pause, and conversely. In some curves, even when the heart 
 beats slowly, it is scarcely possible to distinguish the auricular contraction (indi- 
 
31. E 
 
 84 DURATION OF CARDIAC MOVEMENTS. 
 
 cated by a rise) from the part of the curve corresponding to the pause (indicated 
 by a horizontal line). In one case (heart beats 55 per minute) the pause = 0.4 
 second, the auricular contraction = 0.177 second. In Fig. 32, A, the time occu- 
 pied by the pause + the auricular contraction (74 beats per minute) = 0.5 second. 
 In D, a b= 19 to 20 vibrations = 0.32 second ; in E = 26 vibrations = 0.42 
 second. 
 
 Ventricular Systole. — The ventricular systole is calculated from the begin- 
 ning of the contraction b, to e when the semilunar valves are closed ; it lasts from 
 the first to the second sound. It also varies somewhat, but is more constant. When 
 the heart beats rapidly, it is somewhat less — during slow action, greater. In E = 
 0.32 second; in D = 0.29 second; with 55 beats per minute Landois found it = 
 0.34, with a very high rate of beating = 0.199 second. 
 
 When the ventricles beat feebly, they contract more slowly, as can be shown by applying the 
 registering apparatus to the heart of an animal just killed. In Fig. 39, from the ventricle of a 
 rabbit just killed, the slow heart beats, B, are seen to last longest. 
 
 In calculating the time occupied by the ventricular systole we must remember — (1) The time 
 between the two sounds of the heart, i. <?., from the beginning of the first to the end of the second 
 sound (b to e). 
 
 (2) The time the blood flows into the aorta, which comes to an end at the depression between c 
 and d (in Fig. 31, E). Its commencement, however, does not coincide with b, as the aortic valves 
 open 0.085 {Landois) to 0.073 (Rive) second after the beginning of the ventricular systole. Hence 
 the aortic current lasts 0.08 to 0.09 second. 
 
 This is calculated in the following way : The time between the first sound of the heart and the 
 
 Fig. 39. 
 
 Curves obtained from the ventricle of a rabbit, and written upon a vibrating plate attached to a tuning fork (vibration 
 = 0.01613 second). A, tolerably soon after death ; B, from the dying ventricle. 
 
 pulse in the axillary artery is 0.137 second, and of this time 0.052 second is occupied in the propa- 
 gation of the pulse wave along the 30 cm. of artery lying between the root of the aorta and the 
 axilla. Thus the pulse wave in the aorta occurs 0.137 minus 0.052 = 0.085 second after the begin- 
 ning of the first sound. The current in the pulmonary artery is interrupted in the depression 
 between d and e. 
 
 (3) Lastly, the time occupied by the muscular contraction of the ventricle, which begins at b, 
 reaches its greatest extent at c, and is completely relaxed at/ The apex of the curve c, may be 
 higher or lower according to the flexibility of the intercostal space, hence the position of c varies. 
 In hypertrophy with dilatation of the left ventricle, the duration of the ventricular contraction does 
 not greatly exceed the normal. 
 
 The time which elapses between d and e, i. e., between the complete closure of 
 the aortic and pulmonary valves, is greater the more the pressure in the aorta 
 exceeds that in the pulmonary artery, as the valves are closed by the pressure from 
 above, and the difference in time may be 0.05 second, or even double that time, 
 in which case the second sound appears double (compare § 54). If the aortic 
 pressure diminishes while that in the pulmonary artery rises, d and e may be so near 
 each other that they are no longer marked as distinct elements in the curve. 
 
 The time, ef, during which the ventricles relax varies somewhat : o. 1 second 
 may be taken as a mean. 
 
 Accelerated Cardiac Action. — When the action of the heart is greatly accelerated, the pause 
 is considerably shortened in the first instance (Dondeis), and to a less extent the time of contraction 
 of the auricles and ventricles. When the pulse rate is very rapid, the systole of the atria coincides 
 with the closure of the arterial valves of the preceding contraction, as is shown in Fig. 32, C (dog). 
 
ENDOCARDIAL PRESSURE. 
 
 85 
 
 In registering the cardiac impulse, the apparatus is separated by a greater or less extent of soft 
 parts from the heart itself, so that in all cases the intercostal tissues do not follow exactly the move- 
 ments of the heart, and thus the curve obtained may not coincide mathematically with the movements 
 of the heart. It is desirable that curves be obtained from persons whose hearts are exposed, i. e., in 
 cases of Ectopia cordis. 
 
 Cleft Sternum. —Gibson inscribed cardiograms from the heart of a man with cleft sternum. The 
 following were the results obtained : Auricular contraction = 0.115; ventricular contraction (6. d) 
 1=0.28; difference between closure of valves {d, *) = o.09; ventricular diastole (<,/) = o.it; 
 pause = 0.45 second. 
 
 [Ventricular Systole. — Chapman has calculated the duration of the ventricular systole for 
 varying frequency of the heart beat, as follows, in sees : — 
 
 Frequency 
 per Min. 
 
 Duration of Systole. 
 
 Frequency 
 per Min. 
 
 Duration of Systole. 
 
 46-50 
 
 .3600 (normal). 
 
 f 86- 90 
 i 86- 90 
 
 .3200 (exertion and normal). 
 
 51-55 
 
 .3425 (normal). 
 
 ■2800 (bath). 
 
 / 56-60 
 \ 56-60 
 
 .3200 (bath). 
 
 91- 95 
 
 .2690 (mixed cases). 
 
 .3460 (normal). 
 
 f 96-IOO 
 \ 96-100 
 
 .2730 (normal). 
 
 61-65 
 
 .3200 (mixed cases). 
 
 .2540 (bath). 
 
 66-75 
 
 .3200 (mixed cases). 
 
 IOI-IO5 
 
 .2543 (bath). 
 
 71-75 
 
 .3033 (bath). 
 
 106-1 to 
 
 .2675 (exertion only). 
 
 ( 76-80 
 I 76-80 
 
 .3300 (exertion and normal). 
 
 m-115 
 
 .2475 (mixed cases). 
 
 .3032 (bath). 
 
 1 16-120 
 
 .2350 (mixed cases). 
 
 / 81-85 
 i 81-85 
 
 .3250 (exertion and normal). 
 
 130 
 
 .2100 (exertion). 
 
 .3030 (bath). 
 
 
 
 Fig. 40. 
 
 These results were obtained by measurements of tracings of cardiograms taken after a Turkish 
 bath, or after exertion.] 
 
 Endocardial Pressure. — In large mammals, such as the horse, Chauveau and 
 Marey determined the duration of the events 
 that occur within the heart, and also the 
 endocardial pressure, by means of a cardiac 
 sound. Small elastic bags attached to tubes 
 were introduced through the jugular vein 
 into the right auricle and ventricle. Each 
 of these tubes was connected with a register- 
 ing tambour (Fig. 40), and simultaneous 
 tracings of the variations of pressure within 
 the cavities of the heart were obtained by 
 causing the writing points of the levers of 
 the tambours to write upon a revolving 
 cylinder. 
 
 Fig. 41, A, gives the result obtained when the elastic 
 bag was placed in the right auricle, introduced through 
 the jugular vein and superior vena cava ; B, when it 
 was pushed through the tricuspid valve into the right 
 ventricle ; D, in the root of the aorta, pushed in through 
 the carotid ; C, pushed past the semilunar valves into 
 the left ventricle ; while at E a similar bag has been 
 placed externally between the heart's apex and the 
 inner wall of the chest. In all cases v = auricular 
 contraction ; V, that of the ventricle ; s, closure of semilunar valves, sooner in C than B; P = pause. 
 
 Method. — The cardiac sound consists of a tube containing two separate air passages, and in con- 
 nection with each of these there is a small elastic bag or ampulla. One of the bags is fixed to the 
 free end of the sound, and communicates with one of the air passages. The other bag is placed in 
 connection with the second air passage in the sound, and at such a distance that, when the former 
 bag lies within the ventricle, the latter is in the auricle. Each bag and air tube communicating with 
 it is connected with a Marey's tambour (Fig. 40), provided with a lever which inscribes its move- 
 ments upon a revolving cylinder. Any variation of pressure within the auricle or ventricle will 
 affect the elastic ampullae, and thus raise or depress the lever. Care must be taken that the writing 
 points of the levers are placed exactly above each other. A tracing of the cardiac impulse is taken 
 simultaneously by means of a cardiograph attached to a separate tambour. 
 
 Marey's registering tambour, consisting of a metallic 
 capsule, T, with thin india rubber stretched over 
 it, and bearing an aluminium disk, which acts 
 upon the writing lever, H. By means of a thick- 
 walled caoutchouc tube, it may be connected 
 with any system containing air, so as to record 
 variations of pressure. 
 
86 PATHOLOGICAL DISTURBANCES OF THE CARDIAC IMPULSE. 
 
 It has still to be determined whether the auricles and ventricles act alternately, 
 so that at the moment of the beginning of the ventricular contraction the auricles 
 relax, or whether the ventricles are contracted while the auricles still remain 
 slightly contracted, so that the whole heart is contracted for a short time at least. 
 The latter view was supported by Harvey, Donders, Schiff, and others, while 
 Haller and many of the more recent observers support the view that the action of 
 the auricles and ventricles alternates. In the case of Frau Serafin, whose heart 
 was exposed, v. Ziemssen and Ter Gregorianz obtained curves from the auricles, 
 which showed that the contraction of the auricles continued even after the com- 
 mencement of the ventricular systole. In Marey's curve (Fig. 41) the contrac- 
 tion of the ventricle is represented as following that of the auricle. 
 
 Fig. 41. 
 
 ■■ Right Auricle. 
 
 - Right Ventricle. 
 
 - Left Ventricle. 
 
 Aorta. 
 
 "Cardiac Impulse. 
 
 Curves obtained from the heart by the cardiac sound (Chauveau and Marey). 
 
 52. PATHOLOGICAL DISTURBANCES OF THE CARDIAC IMPULSE.— 
 Change in the Position of the Apex Beat. — The position of the cardiac impulse is changed — 
 (1) by the accumulation of fluids (serum, pus, blood) or gas in one pleural cavity. A copious 
 effusion into the left pleural cavity compresses the lung, and may displace the heart toward the 
 right side, while effusion on the right side may push the heart more to the left. As the right 
 heart must make a greater effort to propel the blood through the compressed lung, the cardiac 
 impulse is usually increased. Advanced emphysema of the lung, causing the diaphragm to be 
 pressed downward, displaces the heart downward and inward, while conversely the pushing or 
 pulling up of the diaphragm (by contraction of the lung, or through pressure from below) causes 
 the apex beat to be displaced upward (even to the third intercostal space), and also slightly to the 
 left. Thickening of the muscular walls and dilatation of the cavities of the left ventricle (hyper- 
 trophy with dilatation) make that ventricle longer and broader, while the increased cardiac impulse 
 
 - 
 
VARIATIONS OF THE CARDIAC IMPULSE. 
 
 87 
 
 may be felt to the left of the mammary line, and in the axillary line in the sixth, seventh, or even 
 eighth intercostal space. Hypertrophy, with dilatation of the right side, increases the breadth of 
 the heart, while the cardiac impulse is felt more to the right, even to the right of the sternum, and 
 at the same time it may be slightly beyond the left mammary line. In the rare cases where the 
 heart is transposed, the apex beat is felt on the right side. When the cardiac impulse goes to the 
 left of the left mammary line, or to the right of the parasternal line, the heart is increased in breadth, 
 and there is hypertrophy of the heart. A greatly increased cardiac impulse may extend to several 
 intercostal spaces. 
 
 The cardiac impulse is abnormally weakened during atrophy and degeneration of the cardiac 
 muscle, or by weakening of the innervation of the cardiac ganglia. It is also weakened when the 
 heart is separated from the chest wall owing to the collection of the fluids or air in the pericardium, 
 or by a greatly distended left lung; and, indeed, when the left side of the chest is filled with fluid, 
 the cardiac impulse may be extinguished. The same occurs when the left ventricle is very imper- 
 
 FlG. 42. 
 
 Various forms of curves obtained from the cardiac impulse, a, b, contraction of auricles ; 6, c, ventricular systole ; 
 
 d, closure of aortic, and e of pulmonary valves ; e, A diastole of ventricle ; P, Q, hypertrophy and dilatation of 
 the left ventricle ; E, stenosis of the aortic orifice ; F, mitralinsufficiency ; G, mitral stenosis ; L, nervous palpi- 
 tation in Basedow's disease ; M, case of so-called hemisystole. 
 
 fectly filled during its contraction (in consequence of marked narrowing of the mitral orifice), 
 or when it can only empty itself very slowly and gradually, as during marked narrowing of the 
 aortic orifice. 
 
 An increase of the cardiac impulse occurs during hypertrophy of the walls, as well as under the 
 influence of various stimuli (psychical, inflammatory, febrile, toxic) which affect the cardiac ganglia. 
 Great hypertrophy of the left ventricle causes the heart to heave, so that a part of the left chest wall 
 may be raised and also vibrate during systole. 
 
 A pulling in of the anterior wall of the chest during cardiac systole occurs in the third and 
 fourth interspaces, not unfrequently under normal circumstances, sometimes during increased cardiac 
 action, and in eccentric hypertrophy of the ventricles. As the heart's apex is slightly displaced, and 
 the ventricle becomes slightly smaller during its systole, the empty space is filled by the yielding 
 soft parts of the intercostal space. When the heart is united with the pericardium and the sur- 
 rounding connective tissue, which renders systolic locomotion of the heart impossible, retraction 
 
88 THE HEART SOUNDS. 
 
 of the chest wall during systole takes the place of the cardiac impulse [Skoda). During the 
 diastole a diastolic cardiac impulse of the corresponding part of the chest wall may be said to 
 occur. 
 
 Changes in the cardiac impulse are best ascertained by taking graphic representations of the 
 cardiac impulse, and studying the curves so obtained. This method has been largely followed by 
 many clinicians. 
 
 In all the following curves, a, b, means auricular contraction ; b, c, ventricular contraction ; d, 
 closure of the aortic valves, and e of the pulmonary; e,f, the time the ventricle is relaxed 
 (Fig. 42). 
 
 In curve P (much reduced), taken from a case of marked hypertrophy with dilatation, the 
 ventricular contraction, b, c, is usually very great, while the time occupied by the contraction is not 
 much increased. P and Q were obtained from a man suffering from marked eccentric hypertrophy 
 of the left ventricle, in consequence of insufficiency of the aortic valves. Curve Q was taken 
 intentionally over the auriculo-ventricular groove, where retraction of the chest wall occurred during 
 systole ; nevertheless, the individual events occurring in the heart are indicated. 
 
 Fig. E is from a case of aortic stenosis. The auricular contraction (a, b) lasts only a short 
 time ; the ventricular systole is obviously lengthened, and after a short elevation (b, c) shows a 
 series of fine indentations (c, e) caused by the blood being pressed through the narrowed and 
 roughened aorta. 
 
 ■Fig. F, from a case of insufficiency of the mitral valve, shows («, b) well marked on account 
 of the increased activity of the left auricle, while the shock (d) from the closure of the aortic valves 
 is small, on account of the diminished tension in the arterial system. On the other hand, the shock 
 from the accentuated pulmonary sound (e) is iery great, and is in the apex of the curve. On 
 account of the great tension in the pulmonary artery, the second pulmonary tone may be so strong, 
 and succeed the second aortic sound (d) so rapidly, that both almost merge completely into each 
 other (H and K). 
 
 The curve of stenosis of the mitral orifice (G) shows a long, irregular-notched auricular 
 contraction (a, b) caused by the blood being forced through an irregular narrow orifice. The ventricu- 
 lar contraction (b, c) is feeble, on account of its being imperfectly filled. The closures of the two 
 valves, d and e, are relatively far apart, and one can hear distinctly a reduplicated second sound. 
 The aortic valves close rapidly, because the aorta is imperfectly supplied with blood, while the 
 more copious inflow of blood into the pulmonary artery causes a later closure of its valves 
 (Geigel). 
 
 If the heart beats rapidly and feebly — if the blood pressure in the aorta and pulmonary artery 
 be low, the signs of closure of the pulmonary valves may be absent — as in curve L — taken from a 
 girl suffering from nervous palpitation and morbus Basedowii. 
 
 In very rare cases of insufficiency of the mitral valve, it has been observed that at certain times 
 both ventricles contract simultaneously, as in a normal heart, but that this alternates with a con- 
 dition where the right ventricle alone seems to contract. Cutve M is such a curve, obtained by 
 Malbranc, who called this condition intermittent hemisystole. The first curve (I) is like a 
 normal curve, during which the whole heart acted as usual. The curve II, however, is caused by 
 the right side of the heart alone ; it wants the closure of the aortic valves, d, and there was no 
 pulse in the arteries. Owing to insufficiency of the triscupid valve, the same person had a venous 
 pulse with every cardiac impulse, so that the arterial and venous pulses first occurred together, and 
 then the venous pulse alone occurred. 
 
 In these cases (Skoda, v. Bamberger, Leyden) the mitral insufficiency leads to the right ventricle 
 being over-distended, while the left is nearly empty, so that the right side requires to contract more 
 energetically than the left. It does not seem that the ri^ht ventricle alone contracts in these cases, 
 but rather that the action of the left side is very feeble. 
 
 53. THE HEART SOUNDS.— On listening over the region of the heart 
 in a healthy man, either with the ear applied directly to the chest wall, or by means 
 of a stethoEcope (Laennec, J8ip), we hear two characteristic sounds, the so-called 
 " heart sounds." Harvey was acquainted with these sounds, but they have 
 been more carefully studied by clinicians since the time of Laennec. The two 
 sounds are called first and second, and together they correspond to a single car- 
 diac cycle. These sounds are separated by silences, so that as far as the sounds 
 are concerned, during a cardiac cycle we have, as in Fig. 43 — 
 
 1. The first sound. 
 
 2. The first or short silence. 
 
 3. The second sound. 
 
 4. The second or long silence. 
 
 [This diagram shows the relation of the events occurring in the heart itself to 
 the sounds and silences (§ 48).] 
 
THE HEART SOUNDS. 
 
 89 
 
 Fig 43. 
 
 Relative Duration. — There is no absolute duration of each phase of a cardiac 
 cycle, but we may take the average duration calculated 
 from the measurements of Gibson in a case of fissure of 
 the sternum to be as follows : — 
 
 Auricular systole, .112 sec. 
 Ventricular systole, .368 " 
 Ventricular diastole, .578 " 
 
 Cardiac cycle, 
 
 1.058 sec. 
 
 Suppose we divide the cycle into tenths ( Walshe), then 
 the first sound will last j^, the first silence -j-j-, the second 
 sound 3%, and the long silence -^ of the entire period. 
 
 The first sound [long or systolic] is somewhat duller, 
 twice as long, booming, and one-third or one-fourth 
 deeper, than the second sound ; it is less sharply defined 
 at first, and is synchronous with the systole of the ven- 
 tricles {Turner). The second sound [short or dias- 
 tolic] is clearer, sharper, shorter, more sudden, and is 
 one-third to one-fourth higher ; it is sharply defined and synchronous with the 
 closure of the semilunar valves. 
 
 The sounds emitted during each cardiac, cycle have been compared to the pro- 
 nunciation of the syllables lubb, dup. Or the result may be expressed thus — 
 
 Scheme of a cardiac cycle, after 
 Gairdner and Sharpey. The 
 inner circle shows what 
 events occur in the heart, 
 and the outer, the relation of 
 the sounds and silences to 
 these events. 
 
 —A - 
 
 =l to !i 
 
 V 
 
 Bu 
 
 tup. 
 
 Bu 
 
 w 
 
 tup. 
 
 [It is to be remembered that in reality four sounds are produced in the heart, \ 
 but the two first sounds occur together and the two second, so that only a single | 
 first and a single second sound are heard.] f 
 
 The causes of the first sound are due to two conditions. As the sound is 
 heard in an excised heart in which the movements of the valves are arrested, and 
 also when the finger is introduced into the auriculo-ventricular orifices so as to 
 prevent the closure of the valves (C. Ludwig and Dogiel), one of the chief factors 
 lies in the " muscle sound" produced by the contracting muscular fibres of the 
 ventricles ( Williams, i8jj). This sound is supported and increased by the sound 
 produced by the tension and vibration of the auriculo-ventricular valves and 
 their chordae tendineae at the moment of the ventricular systole {Rouanet, Kiwisch, 
 Bayer, Giese). Wintrich, by means of proper resonators, has been able so tol 
 analyze the first sound as to distinguish the clear, short, valvular part from thej 
 deep, long, muscular sound. 
 
 The muscle sound produced by transversely-striped muscle does not occur with a simple contrac- 
 tion, but only when several contractions are superposed to produce tetanus (J 303). The ventricular 
 contraction is only a simple contraction, but it lasts considerably longer than the contraction of other 
 muscles, and herein lies the cause of the occurrence of the muscle sound during the ventricular 
 cc ntraction. 
 
 Defective Heart Sounds. — Tn certain conditions (typhus, fatty degeneration of the heart) 
 where the muscular substance of the heart is much weakened, the first sound may be completely 
 inaudible. In aortic insufficiency, in consequence of the reflux of blood from the aorta into the 
 ventricle, the mitral valve is gradually stretched, and sometimes even before the beginning of the 
 ventricular systole the first sound may be absent. Both pathological cases show that for the pro- 
 duction of the first sound, muscle sound and valve sound must eventually work together, and that 
 the tone is altered, or may even disappear, when one of these causes is absent. [Yeo and Barrett 
 state that the sound is purely muscular (?).] 
 
90 
 
 CAUSES OF THE HEART SOUNDS. 
 
 The cause of the second sound is, undoubtedly, due to the prompt closure, 
 and, therefore, sudden stretching or tension, of the semilunar valves of the aorta 
 and pulmonary artery, so that it is purely a valvular sound (Carswell and Rouanet, 
 1830). Perhaps it is augmented by the sudden vibration of the fluid particles in 
 ■the large arterial trunks. As already pointed out (p. 82), the aortic and pulmo- 
 
 Fig. 44. 
 
 The heart — its several parts and great vessels in relation to the front of the thorax. The lungs are collapsed to their 
 normal extent, as after death, exposing the heart. The outlines of the several parts of the heart are indicated 
 by very fine dotted lines. The area of propagation of valvular murmurs is marked out by more visible dotted 
 lines. A, the circle of mitral murmur, corresponds to the left apex The broad and somewhat diffused are-i, 
 roughly triangular, is the region -of tricuspid murmurs, and corresponds generally with the right ventricle, where 
 it is least covered'by lung. The letter C is in its centre. The circumscribed circular area, D. is the part oyer 
 which the pulmonic arterial murmurs are commonly heard loudest. In many cases it is an inch, or even more, 
 lower down, corresponding to the conus arteriosus of the right ventricle, where it touches the wall of the thorax. 
 The internal organs and parts of organs are indicated by letters as follows: r. au right auricle, traced in fine 
 dotting ; a o, arch of aorta, seen in the first intercostal space, and traced in fine dotting on the sternum ; v. i, the 
 innominate veins ; r v, right ventricle ; I. z», left ventricle. 
 
 nary valves do not close simultaneously. Usually, however, the difference in 
 time is so small that both valves make one sound, but the second sound may be 
 double or divided when, through increase of the difference of pressure in the 
 aorta and pulmonary artery, the interval becomes longer. Even in health this 
 
VARIATIONS OF THE HEART SOUNDS. 91 
 
 may be the case, as occurs at the end of inspiratiqn or the beginning of expiration 
 (v. Dusch). 
 
 [The second sound has all the characters of a valvular sound. That the aortic 
 valves are concerned in its production is proved by introducing a curved wire 
 through the left carotid artery and hooking up one or more segments of the valve, 
 when the sound is modified, and it may disappear or be replaced by an abnormal 
 sound or "murmur" {Hope). Again, when these valves are diseased, the sound 
 is altered, and it may be accompanied, or even displaced, by murmurs.] 
 
 Where the Sounds are Heard Loudest. — The sound produced by the 
 tricuspid valve is heard loudest at the junction of the lower right costal cartilages 
 with the sternum ; as the mitral valve lies more to the left and deeper in the chest, 
 and is covered in front by the arterial orifice, the mitral sound is best heard at 
 the apex beat, or immediately above it, where a strip of the left ventricle lies next 
 the chest wall. [The sound is conducted to the part nearest the ear of the listener 
 by the muscular substance of the heart.] The aortic and pulmonary orifices lie 
 so close together that it is convenient to listen for the second {aortic) sound in 
 the direction of the aorta, where it comes nearest to the surface, i.e., over the 
 second right costal cartilage, or aortic cartilage, close to its junction with the 
 sternum. The sound, although produced at the semilunar valves, is carried 
 upward by the column of blood and by the walls of the aorta. The sound pro- 
 duced by the pulmonary artery is heard most distinctly over the third left costal 
 cartilage, somewhat to the left and external to the margin of the sternum (Fig. 44). 
 
 54. VARIATIONS OF THE HEART SOUNDS.— An increase of the first sound of 
 both ventricles indicates a more energetic contraction of the ventricular muscle and a simultaneously 
 greater and more sudden tension of the auriculo-ventricular valves. An increase of the second 
 sound is a sign of increased tension in the interior of the corresponding large arteries. Hence, 
 increase of the second (pulmonary) sound indicates overfilling and excessive tension in the pulmonary 
 circuit. 
 
 Feeble, weak action of the heart, as well as abnormal want of blood in the heart, causes weak 
 heart sounds, which is the case in degenerations of the heart muscle. 
 
 Irregularities in structure of the individual valves may cause the heart sounds to become " impure." 
 If a pathological cavity, filled with air, be so placed, and of such a form as to act as a resonator to 
 the heart sounds, they may assume a "metallic" character. The first and second sounds may be 
 "reduplicated" or [although "duplication" is a. more accurate term {Barr)~\ doubled. The 
 reduplication of the first sound is explained by the tension of the tricuspid and that of the mitral 
 valves not occurring simultaneously. Sometimes a sound is produced by a hypertrophied auricle 
 producing an audible presystolic sound, i.e., a sound or "murmur," preceding the first sound. 
 As the aortic and pulmonary valves do not close quite simultaneously, a reduplicated second sound 
 is only an increase of a physiological condition {Landois). All conditions which cause the aortic 
 valves to close rapidly (diminished amount of blood in the left ventricle) and the pulmonary valves 
 to close later (congestion of the right ventricle — both conditions together in mitral stenosis), favor 
 the production of a reduplicated second sound. 
 
 Cardiac Murmurs. — If irregularities occur in the valves, either in cases of stenosis or in in- 
 sufficiency, so that the blood is subjected to vibratory oscillations and friction, then, instead of the 
 heart sounds, other sounds — murmurs or bruits — arise or accompany these. A combination of these 
 sounds is always accompanied by disturbances of the circulation. [These murmurs may be produced 
 within the heart when they are termed endocardial, or outside it when they are called exocardial 
 murmurs. But other murmurs are due to changes in the quality or amount of the blood, when they 
 are spoken of as haemic murmurs. In the study of all murmurs, note their rhythm or exact relation 
 to the normal sounds, their point of maximum intensity and the direction in which the murmur is 
 propagated^ It is rare that tumors or other deposits projecting into the ventricles cause murmurs, 
 unless there be present at the same time lesions of the valves and disturbances of the circulation. 
 The cardiac murmurs or bruits are always related to the systole or diastole, and usually the systolic 
 are more accentuated and louder. Sometimes they are so loud that the thorax trembles under their 
 irregular oscillations {fremitus, fremissement cataire). 
 
 In cases where diastolic murmurs are heard there are always anatomical changes in the cardiac 
 mechanism. These are insufficiency of the arterial valves, or stenosis of the auriculo-ventricular 
 orifices (usually the left). Systolic murmurs do not always necessitate a disturbance in the cardiac 
 mechanism. They may occur on the left side, owing to insufficiency of the mitral valve, stenosis of 
 the aorta, and in calcification and dilatation of the ascending part of the aorta. These murmurs 
 occur very much less frequently on the right side, and are due to insufficiency of the tricuspid and 
 stenosis of the pulmonary orifice. 
 
92 PHYSICAL EXAMINATION OF THE HEART. 
 
 Functional Murmurs. — Systolic murmurs often occur without any valvular lesion, although 
 they are always less loud, and are caused by abnormal vibrations of the valves or arterial walls. 
 They occur most frequently at the orifice of the pulmonary artery [and are generally heard at the 
 base], less frequently at the mitral, and still less frequently at the aortic or the tricuspid orifice. 
 Anaemia, general malnutrition, acute febrile affections, are the causes of these murmurs. [Some of 
 these are due to an altered condition of the blood, and are called hamic, and others to defective 
 cardiac muscular nutrition and are called dynamic ( Walshe)']. 
 
 Sounds may also occur during a certain stage of inflammation of the pericardium (pericarditis) 
 from the roughened surfaces of this membrane rubbing upon each other. Audible friction sounds 
 are thus produced, and the vibration may even be perceptible to touch. [These are "friction 
 sounds," and quite distinct from sounds produced within the heart itself.]' 
 
 55. DURATION OF THE MOVEMENTS OF THE HEART.— 
 
 That the heart continues to beat for some time after it is cut out of the body, was 
 known to Cleanthes, a contemporary of Herophilus, 300 B.C. The movement 
 lasts longer in cold-blooded animals (frog, turtle, fish) — extending even to days — 
 than in mammals. A rabbit's heart beats from 3 minutes up to 36 minutes after 
 it is cut out of the body. The average of many experiments is about n minutes. 
 Panum found the last trace of contraction to occur in the right auricle (rabbit) 
 15 hours after death; in a mouse's heart, 46 hours; in a dog's, 96 hours. An 
 excised frog's heart beats, at the longest, 2j^ days {Valentin). In a human 
 embryo (third month) the heart was found beating after 4 hours. In this con- 
 dition stimulation causes an increase and acceleration of the action. Afterward, 
 ■the ventricular contraction first becomes weaker, and soon each auricular con- 
 traction is not followed by a ventricular contraction, two or more of the former 
 being succeeded by only one of the latter. At the same time the ventricles 
 contract more slowly (Fig. 39), and soon stop altogether, while the auricles still 
 continue to beat. If the ventricles be stimulated directly, as by pricking them 
 with a pin, they may execute a contraction. The left auricle soon ceases to beat, 
 while the right auricle still continues to contract. The right auricular appendix 
 continues to beat longest, as was observed by Galen and Cardanus (1550). The 
 term "ultimum moriens " is applied to it. Similar observations have been made 
 upon the hearts of persons who have been executed. 
 
 If the heart has ceased to beat, it may be excited to contract for a short time 
 by direct stimulation (Harvey), more especially by heat ; even under these cir- 
 cumstances the auricles and their appendices are the last parts to cease contracting. 
 As a general rule, direct stimulation, although it may cause the heart to act more 
 vigorously for a short time, brings it to rest sooner. In such cases, therefore, the 
 regular sequence of events ceases, and there is usually a twitching movement of 
 the muscular fibres of the heart. C. Ludwig found that, even after the excitability 
 is extinguished in the mammalian heart, it may be restored by injecting arterial 
 blood into the coronary arteries : lesion of these vessels is followed by enfeebled 
 action of the heart (§ 47). Hammer found that in a man whose left coronary 
 artery was plugged, the pulse fell from 80 to 8 beats per minute. 
 
 Action of Gases on the Heart. — During its activity the heart uses O, and produces C0 2 so 
 that it beats longest in pure O (12 hours) (Castell), and not so long in N, — H (1 hour) — C0 2 (10 
 minutes), =C0 (42 minutes) — CI (2 minutes), or in a vacuum (20 to 30 minutes) (Boyle, 1670; 
 Fontana, Tiedemann, 1847), even when there is watery vapor present to prevent evaporation. If 
 the heart be reintroduced into O it begins to beat again. [A frog's heart ceases to beat in compressed 
 O (10-12 atmospheres) in about one -third of the time it would do were it simply excised and left to 
 itself (K. B. Lehmann). An excised heart suspended in ordinary air beats three to four times as 
 long as a heart which is placed upon a glass plate.] A heart which has ceased to contract sponta- 
 neously may contract when an electrical stimulus is applied to it, but it does not do so for a longer 
 time than other muscles (Budge). 
 
 [56. PHYSICAL EXAMINATION OF THE HEART.]— [The 
 
 physical methods of diagnosis enable us to obtain precise knowledge regarding the 
 actual state of the heart. The methods available are : — 
 
i. Inspection. 
 2. Palpation. 
 
 THE CARDIAC NERVES. 93 
 
 3. Percussion. 
 
 4. Auscultation. 
 
 To arrive at a correct diagnosis all the methods must be employed. J 
 
 [Inspection. — The person is supposed to have his chest exposed and to be in the recumbent posi- 
 tion. It is important to remember the limits of the heart. The base corresponds to a line joining 
 the upper margins of the third costal cartilages, the apex to the fifth interspace, while transversely it 
 extends from a little to the right of the sternum to within a little of the left nipple; this area occu- 
 pied by the heart being called the deep cardiac region. By the eye we can detect any alteration 
 in the configuration of the preecordia, bulging or retraction of the region as a whole or of the inter- 
 costal spaces, and we may detect variations in the position, character, extent of the cardiac impulse, 
 or the presence of other visible pulsations.] 
 
 [Palpation. — By placing the whole hand flat upon the praecordia, we can ascertain the presence 
 or absence, the situation and extent, and any alterations in the characters of the apex beat ; or we 
 may detect the existence of abnormal pulsations, vibrations, thrills, or friction in this region. In 
 feeling for the apex beat, if it be at all feeble, it is well to make the patient lean forward. Of 
 course, it must be remembered that the whole heart may be displaced by tumors or accumulations of 
 fluids pressing upon it, i. e., conditions external to itself, or the apex beat may be displaced from 
 causes within the heart itself, as in hypertrophy of the left ventricle.] 
 
 [Percussion. — As the heart is a solid organ, and is surrounded by the lungs, which contain air, 
 it is evident that the sound emitted by striking the chest over the region of the former must be dif- 
 ferent from that produced over the latter. Not only is there a difference in the sound or note emitted, 
 but the " sensation of resistance " which one feels on percussing the two organs is different. We may 
 ascertain — 
 
 1. The superficial or absolute cardiac dullness. 
 
 2. The deep or relative dullness.] 
 
 [Superficial Cardiac Dullness. — This, theoretically, is the part of the heart in direct contact 
 with the chest wall and uncovered by lung, but obviously as the lungs vary in size during respiration, 
 it must be smaller during inspiration and larger during expiration. It forms a roughly triangular 
 space, whose base cannot be accurately determined, as the heart dullness merges into that of the 
 liver, situate below it, but it corresponds to a horizontal line 2)4 inches long, extending from the 
 apex beat to the middle of the sternum. The internal side corresponding to the left edge of the 
 sternum is 2 inches long, and reaches from the junction of the fourth costal cartilage with the ster- 
 num — apex of the triangle — to the sternal end of the base line. The superior, outer, or oblique line, 
 3 inches in length, is somewhat curved, and passes downward and outward from the apex of the 
 triangle to the apex of the heart.] 
 
 [Deep Cardiac Dullness. — By this method theoretically we seek to define the exact limits of 
 the heart as a whole, and thus to ascertain its absolute size, and of course, percussion has to be done 
 through a certain thickness of lung tissue, and hence one must strike the pleximeter forcibly. It 
 extends vertically from the third rib and ends at the sixth, but owing to the cardiac merging in the 
 hepatic dullness, this lower limit cannot be accurately ascertained ; while transversely at the fourth 
 rib it extends from just within the nipple line to slightly beyond the right of the sternum.] 
 
 [By these means we may detect increase in the size of the heart or alterations in the relation of the 
 lungs to the heart, fluid in pericardium, etc.] 
 
 [Auscultation. — This is one of the most valuable methods, for by it we can detect variations and 
 modifications in the healthy sounds of the heart, the rhythm and frequency of the heart beat, the 
 existence of abnormal sounds, and their exact relation to the normal sounds, also their characters 
 and relation to the cardiac cycle, and the direction in which these sounds are propagated ( j) 54).] 
 
 57. INNERVATION OF THE HEART, CARDIAC NERVES. 
 
 — [Intra- and Extra-Cardiac Nervous Mechanism. — When the heart is 
 removed from the body, or when all the nerves which pass to it are divided, it 
 still beats for some time, so that its movements must depend upon some mechan- 
 ism situated within itself. The ordinary rhythmical movements of the heart are 
 undoubtedly associated with the presence of nerve ganglia, which exist in the 
 substance of the heart — the intra-cardiac 'ganglia. But the movements of the heart 
 are influenced by nervous impulses which reach it from without, so that there falls 
 to be studied an intra-cardiac and an extra-cardiac nervous mechanism.] 
 
 The cardiac plexus is composed of the following nerves : (1) The cardiac 
 branches of the vagus, the branch of the same name from the external branch of 
 the superior laryngeal, a branch from the inferior laryngeal, and sometimes 
 branches from the pulmonary plexus of the vagus (more numerous on the right 
 side) ; (2) the superior, middle, inferior, and lowest cardiac branches of the three 
 cervical ganglia and the first thoracic ganglia of the sympathetic ; (3) the incon- 
 
94 
 
 THE FROG S HEART. 
 
 stant twig of the descending branch of the hypoglossal nerve, which, according to 
 Liischka, arises from the upper cervical ganglia. From the plexus there proceed 
 — the deep and the superficial nerves (the latter usually at the division of the pul- 
 monary artery under the arch of the aorta, and containing a ganglion) (§ 370). 
 The following nerves may be separately traced from the plexus : — 
 
 (a) The plexus coronarius dexter and sinister {Scarpa), which contains 
 the vasomotor nerves for these vessels (physiological proof still wanting) as well as 
 the nerves (sensory ?) proceeding from them (to the pericardium ?). 
 
 (b) Intra-Cardiac Nerves and Ganglia. — The nerves lying in the grooves 
 of the heart and in its substance, containing numerous ganglia {Hemak), which are 
 regarded as the automatic motor centres of the heart. A nervous ring containing 
 numerous ganglia corresponds to the margin of the septum atriorum ; there is 
 another in the auriculo-ventricular groove. Where the two meet, they exchange 
 fibres. The ganglia usually lie near the pericardium. In mammals the two 
 largest ganglia lie near the orifice of the superior vena cava — in birds the largest 
 ganglion (containing thousands of ganglionic cells) lies posteriorly where the longi- 
 tudinal and transverse sulci cross each other. Fine branches, also provided with 
 small ganglia, proceed from these ganglia, and penetrate the muscular walls of the 
 auricles and ventricles. 
 
 Fig. 46. 
 
 Heart of frog from the front. V, single ventricle ; Ad, As, right 
 and left auricles ; B, bulbus arteriosus ; i, carotid, 2, aorta, 
 and 3', pulmo-cutaneous arteries ; C, carotid gland (Ecker). 
 
 vVp. 
 
 A.s.- 
 A.]v- 
 
 m 
 
 -C.Stl. 
 
 -Ad. 
 
 
 Heart of frog from behind, s.v., sinus venosus 
 opened ; ci, inferior ; csd, ess, right and 
 left superior vense cavse ; vfi. , pulmonary 
 vein ; Ad, and As, right and left auricles ; 
 Ap, communication between the right and 
 left auricle (JScker). 
 
 [Frog's Heart. — The frog's heart consists of the sinus venosus, into which open the single 
 inferior and the two superior venae cavae (Fig. 46). There are two auricles; the right one commu- 
 nicates with the sinus venosus, and opens into the single ventricle ; the left auricle also opens into the 
 single ventricle (Fig. 45, v), and in the latter are mixed the venous blood returned by the right 
 auricle and the arterial blood from the left auricle. The aorta with its bulbus arteriosus conducts 
 the blood from the ventricle (Figs. 46, 49a). The various orifices 1 are guarded by projections of 
 tissue, which act like valves. The two auricles are completely separated by a septum. This septum 
 ends posteriorly in a free concave margin (Fig. 49), so as to divide the auriculo-ventricular orifice 
 into a right and a left orifice. Each orifice is guarded by two thick, fleshy valves, which close it.] 
 
 [Nerves. — The two cardiac branches of the vagi — the nervi cardiaci — proceed to the poste- 
 rior surface of the sinus venosus, and where the latter joins the auricle they interlace, and are mixed 
 with a number of ganglion cells (Figs. 47, 49a). This spot isealled Remak's ganglion, is some- 
 times single, at others double* and it can be seen.as a white " crescent " when the heart is lifted up 
 and looked at from behind (Fig. 46). The cardiac nerves proceed downward on the auricular 
 septum, exchanging fibres in their course to join two ganglia at the auriculo-ventricular groove, 
 and known as Bidder's Ganglia (Figs. 47, 49a. It has been stated by one observer that the 
 bulbus arteriosus contains ganglionic cells, but this is denied by others.] 
 
 According to Openchowsky, every part of the heart (frog, triton, tortoise) contains nerve fibres 
 which are connected with every muscular fibre. In the auricles, at the end of the non-medullated 
 fibre, a tri-radiate nucleus exists which gives off fibrils to the muscular bundles. 
 
 There is a network of fine nerve fibres distributed immediately under the endocardium ; these 
 fibres act partly in a centripetal direction on the cardiac ganglia, and are partly motor for the endo- 
 cardial muscles. The parietal layer of the pericardium contains (sensory) nerve fibres. The fol- 
 
MOTOR CENTRES OF THE HEART. 
 
 95 
 
 lowing kinds of nerve cells are found — unipolar cells, the single processes of which afterward divide ; 
 bipolar pyriform cells- (Fig. 48), which in the frog possess a straight («) and usually, also, a spiral 
 process (0). 
 
 58. THE AUTOMATIC MOTOR CENTRES OF THE HEART. 
 
 — (1) We must assume that the nervous centres which excite the cardiac move- 
 
 Fig. 47. 
 
 Fig. 48. 
 
 Auricular septum of a frog's heart, a, anterior, and/, poste- 
 rior branch , of the cardiac vagus; B, Bidder's ganglion 
 (Ecker). 
 
 Pyriform ganglionic bi-polar nerve-cell 
 from the heart of a frog m, sheath; 
 M, straight process ; o, spiral pro- 
 
 ments, and maintain the rhythm of these movements, lie within the heart, and 
 that they are, probably, represented by the ganglia. 
 
 (2) There are — not one, but several of these centres in the heart, which are 
 connected with each other by conducting paths. As long as the heart is intact, 
 all its parts are made to move in rhythmical sequence from a principal central 
 point, an impulse being conducted from this centre through the conducting paths 
 
 Fig. 493. 
 
 Longitudinal section of frog's heart ; left side shows «, 
 auricle ; v, ventricle ; s, auricular septum ; p, pul- 
 monary vein, with a sound, /*, projecting into left 
 auricle ; v, ventricle ; c, c / , sound projecting from 
 right auricle into ventricle ; «. upper, and « r lower 
 cardiac nerves. 
 
 Scheme ot nerves of frog's heart. R. Remak's, 
 and B, Bidder's ganglia ; S. V., sinus venosuff; 
 A, auricles ; V, ventricle ; B. A., bulbus arte- 
 riosus ; vag. vagi (after Brunton). 
 
 {Ponders). What the "discharging forces " of these regular progressive move- 
 ments are is unknown. If, however, the heart be subjected to the action of diffuse 
 stimuli {e.g., strong electrical currents), all the centres are thrown into action, 
 and a spasm-like action of the heart occurs. The dominating centre lies in the 
 auricles, hence the regular progressive movement usually starts from them. If the 
 
96 EXPERIMENTS ON THE HEART. 
 
 excitability is diminished (e.g., by touching the septum with opium — Ludwig, 
 Hoffa), other centres seem to undertake this function, in which case the move- 
 ment may extend from the ventricles to the auricles. If a heart be cut into 
 pieces, so that the individual pieces still remain connected with each other, the 
 regular peristaltic or wave-like movements proceeding from the auricles to the 
 ventricle may continue for a long time (Donders, Engelmanri). If the heart, 
 however, be completely divided into two distinct pieces (auricle and ventricle), 
 the movements of both parts continue, but not in the same sequence — they beat 
 at different rates. According to Kronecker and Schmey, in the dog's heart there 
 is a spot above the lower limit of the upper third of the ventricular septum which, 
 when it is injured, brings the heart to a standstill ; this has been called a coordi- 
 nating centre. 
 
 (3) All stimuli of moderate strength applied directly to the heart cause at first 
 an increase of the rhythmical heart beats ; stronger stimuli cause a diminution, 
 and it may be paralysis, which is often preceded by a convulsive movement. 
 Increased activity exhausts the energy of the heart sooner. 
 
 (4) The auricular centres seem to be more excitable than those of the ventricle ; 
 hence, in a heart left to itself the auricles pulsate longest. 
 
 (5) The heart may be excited (reflexly) from its inner surface. Weak stimuli 
 applied to the inner surface of the heart greatly accelerate the heart's action, the 
 stimulus required being much feebler than that applied to the external surface of 
 the heart. Strong stimuli, which bring the heart to rest, also act more easily 
 when applied to the inner surface than when they are applied to its outer surface 
 (Henry, 1832). The ventricle is always the part first to be paralyzed. 
 
 (6) In order that the heart may continue to contract, it is necessary that it be 
 supplied with a fluid which, in addition to O (Ludwig, Volkmann, Goltz), must 
 contain the necessary nutritive materials. The most perfect fluid, of course, is 
 blood. Hence, the heart, after a time, ceases to beat in an indifferent fluid (0.6 
 per cent, sodium chloride), but its activity may be revived by supplying it with a 
 proper nutritive fluid. 
 
 Cardiac Nutritive Fluids. — These nutritive fluids are such as contain serum albumin, e.g., blood, 
 serum or lymph. Serum retains its nutritive properties even after it has been subjected to diffusion 
 [Martins and Kronecker). Milk and whey (v. Otl), normal saline solution (0.6 per cent. NaCl) 
 mixed with blood, albumin or peptone and 0.3 per cent, sodium carbonate (Kronecker, Meruno- 
 wicz and Stiinon) a trace of caustic soda ( Gaule), or a solution of the salts of serum, are suitable. 
 Alkaline solution of soda revives a feebly beating heart by neutralizing the acid formed in the 
 cardiac muscle {S. Ringer). 
 
 (7) The independent pulsations of parts of the heart which are devoid of ganglia 
 show that the presence of ganglia is not absolutely necessary in order to have 
 rhythmical pulsation. Direct stimulation of the heart may cause these movements. 
 But the ganglia are more excitable than the heart muscle itself, and they conduct 
 the impulses which lead to the regular alternating action of the various parts of 
 the heart, so that under normal circumstances we must assume that the action of 
 the heart is governed by the ganglia. 
 
 The chief experiments upon which the above statements are based consist of 
 two classes: (1) Where the heart is incised or divided; and (2) where it is 
 
 STIMULATED DIRECTLY. 
 
 (I) Experiments by cutting and ligaturing the heart. These experiments 
 have been made chiefly upon the heart of the frog. 
 
 The Ligature experiments are performed by tightening and then relaxing a 
 ligature placed around the heart, so that the physiological connection is destroyed, 
 while the anatomical or mechanical connections (continuity of the cardiac wall, 
 intact condition of its cavities) still exist. The most important of these experi- 
 ments are — 
 
 (1) Stannius's Experiment. — If the sinus venosus of a frog's heart be 
 separated from the auricles, either by an incision or by a ligature, the auricles and 
 
SECTION OF THE HEART. 97 
 
 ventricle stand still in diastole, while the veins and the remainder of the sinus 
 continue to beat (Fig. 50, 1). If a second incision be made at the auriculo- 
 ventricular groove, as a rule, the ventricle begins at once to beat again, while the 
 auricles remain in the condition of diastolic rest. [Thus, the sinus venosus and 
 ventricle continue to beat, while the auricle stands still, but the two former no 
 longer beat with the same rhythm ; the ventricle usually beats more slowly, as is 
 shown in Fig. 50, 2, by the large zig-zags.] According to the position of the 
 second ligature or incision, the auricles may also beat along with the ventricles, 
 or the auricles alone may beat, while the ventricles remain at rest (1852). 
 
 Theoretical. — Various explanations of these experiments have been given : (a) Remak's gan- 
 glion in the sinus venosus is distinguished by its great excitability, while Bidder's ganglion in the 
 auriculo- ventricular groove is less excitable ; in the normal condition of the heart the motor impulse 
 is carried from the former to the tatter. If the sinus venosus be separated from the heart, Remak's 
 ganglion has no action on the heart. The heart stops, for two reasons — first, because Bidder's gan- 
 glion alone has not sufficient energy to excite it to action, and because the inhibitory fibres of the 
 vagus going to the heart have been stimulated by being divided at this point (Jleidenhain). [That 
 stimulation of the inhibitory fibres of the vagus is not the 
 cause of the standstill, is proved by the fact that the stand- 
 still occurs even after the administration of atropine, which 
 paralyzes the cardiac inhibitory mechanism.] The passive 
 heart, however, may be made to contract by mechanically 
 stimulating Bidder's ganglion, e. g., by a slight prick with a 
 needle in the auriculo-ventricular groove (H. Muni), or by 
 the action of a constant current of moderate strength (Eck- 
 hard), the ventricular pulsation at the same time preceding ^ 
 
 the auricular (v. Bezold, Bernstein). If the auriculo-ven- Stannius's experiment. Scheme after Brun- 
 tricular groove be divided, the ventricle pulsates again, ton. A, auricle, V, ventr., SV, sinus 
 
 because Bidder's ganglion has been stimulated by the act of v 1" ?. us ' , The ?*'"? i inl ; s . indica ' e 
 
 ,. ... ., .., * .. .. ,, - , • - t which parts continue to beat; m 2 the 
 
 dividing it ; while, at the same time, the ventricle IS with- ventricle beats at a different rate, 
 
 drawn from the inhibitory influence of the vagus produced 
 
 by the first division at the sinus venosus. If the line of separation is so made that Bidder's gan- 
 glion remains attached to the auricles, these pulsate, and the ventricle rests ; if it be divided into 
 halves, the auricles and ventricles pulsate, each half being excited by the portion of the ganglion in 
 relation with it. (b) According to another view, both Remak's (a) and Bidder's ganglia (b) are 
 motor centres, but in the auricles there is in addition an inhibitory ganglionic system (e) (Bezold, 
 Traube). Under normal circumstances a + b is stronger than c, while c is stronger than a or b 
 separately. If the sinus venosus be separated it beats in virtue of a; on the other hand, the heart 
 rests because c is stronger than b. If the section be made at the level of the auriculo ventricular 
 groove, the auricles stand still, owing to c, while the ventricle beats, owing to b. 
 
 (2) If the ventricle of a frog's heart be separated from the rest of the heart by 
 means of a ligature, or by an incision carried through it at the level of the 
 auriculo-ventricular groove, the sinus and atria pulsate undisturbed as before 
 (Descartes, 1644), but the ventricle stands still in diastole. Local stimulation of 
 the ventricle causes a single contraction. If the incision be so made that the 
 lower margin of the auricular septum remains attached to the ventricle, the latter 
 pulsates (Rosenberger, 1850). Even the ventricles of a rabbit's heart, when 
 separated with a part of the auricles in connection with them, pulsate {Tigerstedf). 
 
 [Gaskell's Clamp. — Gaskell uses a clamp, regulated by a fhillimetre screw, to compress the heart, 
 and thus to obstruct the passage of impulses from one part of the heart to the other, or to " block " 
 the way, the pulsations of the auricles and ventricles being separately registered, as described at p. 
 101. By compressing the heart at the auriculo-ventricular groove, the ratio of auricular and ven- 
 tricular beats alters, and instead of being I : I, there may be 2, 3, or more auricular beats for each 
 
 A II III IV "I 
 
 beat of the ventricle, expressed thus : — -, -, — , — . 
 
 V I I 1 J 
 
 (3) Section of the Heart. — Engelmann's recent experiments show that if 
 the ventricle of a frog's heart be cut up into two or more strips in a zig-zag way, 
 so that the individual parts still remain connected with each other by muscular 
 tissue, the strips still beat in a regularly progressive, rhythmical manner, provided 
 one strip is caused to contract. The rapidity of the transmission is about 10 to 
 30 mm. per sec. (Engelmann). Hence, it appears that the conducting paths for 
 
 7 
 
98 
 
 ACTION OF FLUIDS ON THE HEART. 
 
 the impulse causing the contraction are not nervous, but must be the contractile 
 mass itself. It has not been proved that nerve fibres proceed from the ganglia to 
 all the muscles. 
 
 [According to Marchand's experiments, it takes a very long time for the excitement to pass from 
 the auricles to the ventricle — a much longer time, in fact, than it would require to conduct the 
 excitement through muscle — so that it is probable that the propagation of the impulse from the 
 auricles to the ventricle is conducted by nervous channels to the auriculo-ventricular nervous appa- 
 ratus. In fact, in the mammalian heart the muscular fibres of the auricles are quite distinct from 
 those of the ventricle.] 
 
 (4) It is usually stated that when the apex of a frog's heart is severed from the 
 rest of the heart, it no longer pulsates (Heidenhain, Goltz), but such an apex, if 
 stimulated mechanically, responds with a single contraction. 
 
 Action of Fluids on the Heart. — Haller was of opinion that the venous 
 blood was the natural stimulus which caused the heart to contract. That this is 
 not so, is proved at once by the fact that the heart beats rhythmically when it 
 contains no blood. 
 
 Fig. 51. 
 
 Fig. 52. 
 
 Scheme of a frog manometer, a, h, Mari- 
 otte's flasks for the nutrient fluids ; s, 
 stop-cock; c, cannula; m, manometer; 
 h, heart ; d, glass cup for h; e, £*, elec- 
 trodes ; cyl, revolving cylinder. 
 
 Double-way or perfusion cannula (nat. size) 
 for a frog's heart, c, for fixing an elec- 
 trode ; d, the heart is tied over the 
 flanges, preventing it from slipping out ; 
 e, section of d. 
 
 Blood and other fluids which are supplied to an excised heart are not the cause 
 of its rhythmical movements, but only the conditions on which these movements 
 depend. Thus, a heart which is too feeble to contract may be made to do so by 
 supplying it with a fluid containing proteids, when a latent intra-cardiac mechan- 
 ism is brought into action, the albuminous or other fluid merely supplying the 
 pabulum for the excitable elements. 
 
 [Methods. — The study of the action of fluids upon the excised frog's heart has been rendered 
 possible by the invention of Ludwig's " frog manometer." The apparatus has been improved 
 by Ludwig's pupils, and already numerous important results have been obtained. The apparatus 
 (Fig. 51) consists of (1) a double- way cannula, c, which is tied into the heart, h ; (2) a manometer, 
 m, connected with c, and registering the movements of its mercury on a revolving cylinder, cyl ; 
 (3) two Mariotte's flasks, a and b, which are connected with the other limb of the cannula. Either 
 a or b can be placed in communication with the interior of the heart by means of the stop-cock, s. 
 The fluid in one graduated tube may be poisoned, and the other not ; d is a glass vessel for fluid, in 
 which the heart pulsates, e' and e are electrodes, e is inserted into the fluid in d, e' is attached to the 
 German silver cannula which is shown in Fig. 52.] 
 
 [In the tonometer of Roy (Fig. 53) the ventricle, h, or the whole heart, is placed in an air-tight 
 
ACTION OF FLUIDS ON THE HEART. 
 
 99 
 
 chamber, o, filled with oil, or with oil and normal saline solution. As before, a " perfusion " cannula 
 is tied into the heart. A piston,^*, works up and down in a cylinder, and is adjusted by means of a 
 thin flexible animal membrane, such as is used by perfumers. Attached to the piston by means of a 
 thread is a writing lever, /, which records the variations of pressure within the chamber, o. When 
 the ventricle contracts, it becomes smaller, diminishes the pressure within o, and hence the piston 
 and lever rise ; conversely, when the heart dilates, the lever and piston descend. Variations in the 
 volume of the ventricle may be registered, without in any way interfering with the flow of fluids 
 through it.] 
 
 [Two preparations of the frog's heart have been used — (i) The "heart," in which case the 
 cannula is introduced into the heart through the sinus venosus, and a ligature is tied over it around 
 the auricle, or it may be the sinus venosus. Thus the auriculo-ventricular ganglia and other nervous 
 structures remain in the preparation. This was the heart preparation employed by Luciani and 
 Rossbach. (2) In the " heart apex," or apex preparation, the cannula is introduced as before, but 
 the ligature is lied on it over the ventricle, several millimetres below the auriculo-ventricular groove, 
 so that this preparation contains none of the auriculo-ventricular ganglia, and, according to the usual 
 statement, this part of the heart is devoid of nerve ganglia. This is the preparation which was used 
 by Bowditch, Kronecker and Stirling, Merunowicz, and others. The first effect of the application 
 of the ligature in both cases is, that both preparations cease to beat, but the '■ heart" usually resumes 
 its ryhthmical contractions within several minutes, while the "heart apex" does not contract spon- 
 taneously until after a much longer time {10 to 90 mins. )]. 
 
 [If the " heart apex " be filled with a 0.6 per cent, solution of common salt, the contractions are 
 
 Roy's apparatus or tonometer for the heart. h. heart ; o, air-tight chamber ; /, piston ; /, writing lever ; 
 
 e, outflow tube. 
 
 at first of greater extent, but they afterward cease, and the preparation passes into a condition of 
 "apparent death;" while if the action of the fluid be prolonged, the heart may not contract at all, 
 even when it is stimulated electrically or mechanically. It may be made, however, to pulsate again, 
 if it be supplied with saline solution containing blood (1 to 10 per cent.). The " Stille " or state of 
 quiescence may last 90 mins. (Kronecker and Merunowicz). If the ventricle be nipped with wire 
 forceps at the junction of the upper with its middle third, so as to separate the lower two-thirds of 
 the ventricle physiologically but not anatomically from the rest of the heart, then the apex will cease 
 to contract, although it is still supplied with the frog's own blood (Bernstein, Bowditch). The 
 physiologically isolated apex may be made to beat by clamping the aortic branches so as to prevent 
 blood passing out of the heart, and thus raising the intra-cardiac pressure. The rate of the beat of 
 the apex is independent of and slower than that of the rest of the heart. This experiment proves 
 that the amount of pressure within the apex cavity is an important factor in the causation of the 
 spontaneous beats of the ap2x (Gaskell). If blood serum, to which a trace of delphinin is added, 
 be transfused or "perfused" through the heart, it begins to beat within a minute, continues to beat 
 for several seconds, and then stands still in diastole (Bowditch). Quinine (Schtschepotjew) and a 
 mixture of atropine and muscarin have a similar action (v. Basch). These experiments show that, 
 provided no nervous apparatus exists within the heart apex, the cause of the varying contraction is 
 to be sought for in the musculature of the heart (Kronecker), and that the stimulus necessary for the 
 systole of the heart's apex may arise within itself (Aubert). If there is no nervous apparatus of any 
 kind present, then we must assume that the heart muscle may execute rhythmical movements inde- 
 pendently of the presence of any nervous mechanism, although it is usually assumed that the ganglia 
 
100 
 
 ACTION OF HEAT ON THE HEART. 
 
 excite the heart muscle to pulsate rhythmically. It is by no means definitely proved that the heart 
 apex is devoid of all nervous structures, which may act as originators of these rhythmical impulses.] 
 
 [Action of Drugs. — If the heart apex contains no nervous structures, it must form a good object 
 for the study of the action of drugs on the cardiac muscle. Some of these have been mentioned 
 already. Ringer finds that a calcium salt makes the contractions higher and longer. Dilute acids 
 added to saline solution, c. g., lactic, cause complete relaxation of the cardiac musculature, while 
 dilute alkalies produce an opposite effect or tonic contraction, even though the apex be not pulsating. 
 The action of a dilute acid may be set aside by a dilute alkali and vice versa. Digitalin, antiarin, 
 barium, and veratria act like alkalies, while saponin, muscarin, and pilocarpin have the effect of 
 acids (g 6s).] 
 
 [The "Heart" preparation in many respects behaves like the foregoing, i. e„ it is exhausted 
 after a time by the continued application of normal saline solution (0.6 per cent. NaCl), while its 
 activity may be restored by supplying it with albuminous and other fluids (p. 98).] 
 
 [(5) Luciani found that such a heart, when filled with pure serum, produced 
 groups of pulsations with a long diastolic pause between every two groups (Fig. 54). 
 The successive beats in each group assume a " staircase " character (p. 102). These 
 periodic groups undergo many changes ; they occur when the heart is filled with 
 pure serum free from blood corpuscles, and they disappear and give place to 
 regular pulsations when defibrinated blood or serum containing haemoglobin or 
 normal saline solution (Jfossoach) is used. They also occur when the blood within 
 the heart has become dark colored, i. e., when it has been deprived of certain of 
 its constituents, and if a trace of veratrin be added to bright red blood they 
 occur.] 
 
 (6) The same apparatus permits of the application of electrical stimuli to either 
 
 Fig. 54. 
 
 Four groups of pulsations with intervening pauses, as obtained by Luciani, with their ' 
 points on the abscissa were marked every 10 seconds. 
 
 staircase " character. The 
 
 of the above-named preparations. An apex preparation, when stimulated with 
 even a weak induction shock, always gives its maximal contraction, and when a 
 tetanizing current is applied tetanus does not occur (Kronecker and Stirling). 
 When the opening and closing shocks of a sufficiently strong constant current are 
 applied to the heart apex, it contracts with each closing or opening shock. [When 
 a constant current is applied to the lower two-thirds of the ventricle (heart apex), 
 under certain conditions the apex contracts rhythmically. This is an important 
 fact in connection with any theory of the cardiac beat.] 
 
 (7) If the bulbus aortas (frog) be ligatured, it still pulsates, provided the 
 internal pressure be moderate. Should it cease to beat, a single stimulus makes it 
 respond by a series of contractions. Increase of temperature to 35 C, and 
 raising the pressure within it, increase the number of pulsations {Engelmanri). 
 
 (II) Direct Stimulation of the Heart. — All direct cardiac stimuli act 
 more energetically on the inner than on the outer surface of the heart. If strong 
 stimuli are applied for too long a time, the ventricle is the part first paralyzed. 
 
 (a) Thermal Stimuli. — [Heat affects the number or frequency and the amplitude of the 
 pulsations, as well as the duration of the systole and diastole and the excitability of the heart.] 
 Descartes (1614) observed that heat increases the number of pulsations of an eel's heart. A. v. 
 Humboldt found that when a frog's heart was placed in lukewarm water, the number of beats 
 increased from 12 to 40 per minute. As the temperature increases, the number of beats is at first 
 considerably increased, but afterward the beats again become fewer, and if the temperature is 
 raised above a certain limit the heart stands still, the myosin of which its fibres consist is coagulated, 
 
ACTION OF MECHANICAL AND ELECTRICAL STIMULI. 
 
 101 
 
 and "heat rigor" occurs. Even before this stage is reached, 
 however, the heart may stand still, the muscular fibres appear- 
 ing to remain contracted. The ventricles usually cease to beat 
 before the auricles (Schelske). The size and extent of the'con- 
 tractions increase up to about 20° C, but above this point they 
 diminish (Fig. 55). The time occupied by any single con- 
 traction at 20 C is only about T \y of the time occupied by a 
 contraction occurring at 5 C. 
 
 A heart which has been warmed is capable of reacting pretty 
 rapidly to intermittent stimuli, while a heart at a low tempera- 
 ture reacts only to stimuli occurring at a considerable interval. 
 If a frog be kept in a cold place its heart beats slowly and 
 does little work, but if the heart be supplied with the extract 
 of a frog which has been kept warm, it is rendered more 
 capable of doing work (Gaule). 
 
 Cold. — When the temperature of the blood is diminished, 
 the heart beats slower (Kielmeyer, 1793). A frog's heart 
 placed between two watch glasses and laid on ice, beats very 
 much slower (Ludwig, 1861). The pulsations of a frog's 
 heart stop when the heart is exposed to a.temperature of 4 C. 
 to 0° (£. Cyon). If a frog's heart be taken out of warm waler, 
 and suddenly placed upon ice, it beats more rapidly, and con- 
 versely, if it be taken from ice and placed over warm water, it 
 beats more slowly at first and more rapidly afterward (Aristaw). 
 
 Fig. 55. 
 
 fU-v*J'. «i_a_oC. 
 
 Fig. a, contractions ot a frog's heart at 19 C. ; 5, at 34 C. ; c, at 3 C. 
 
 [Methods. — The effect of heat on a heart may be studied by the aid of the frog manometer, the 
 fluid in which the heart is placed being raised to any temperature required. For demonstration 
 purposes, the heart of a pithed frog is excised and placed on a glass slide under a light lever, such 
 as a straw. The slide is warmed by means of a spirit lamp. In this way the frequency and ampli- 
 tude of the contractions are readily made visible at a distance.] 
 
 [Gaskell fixes the heart by means of a clamp placed round the auriculo-ventricular groove, 
 while levers are placed horizontally above and below the heart. These levers are fixed to part of 
 the auricles and to the apex by means of threads. Each part of the heart attached to a lever, as it 
 contracts, pulls upon its own lever, so that the extent and duration of each contraction may be 
 registered. This method is applicable for studying the effect of the vagus and other nerves upon 
 the heart.] 
 
 (6) Mechanical Stimuli. — Pressure applied externally to the heart accelerates its action. In 
 the case of Frau Serafin, v. Ziemssen found that slight pressure on the auriculo-ventricular groove 
 caused a second short contraction of both ventricles after the heart beat. Strong pressure causes a 
 very irregular action of the cardiac muscle. This may readily be produced by compressing the 
 freshly-excised heart of a dog between the fingers. 
 
 The intra-cardiac pressure also affects the heart beat (p. 99). If the pressure within the heart 
 be increased, the heart beats are gradually increased; if it be diminished, the number of beats 
 diminishes (Ludwig and Thiry). If the intra-cardiac pressure be very greatly increased, the heart's 
 action becomes very irregular and slower [Heidenhain). A heart which has ceased to beat 
 may, under certain circumstances, be caused to execute a single contraction, if it be stimulated 
 mechanically. 
 
 U) Electrical Stimuli. — A constant electrical current of moderate strength increases the number 
 of heart beats, v. Ziemssen found, in the case of Frau Serafin (§ 47, 3), that the number of beats 
 was doubled when a constant uninterrupted strong current was passed through the ventricles. If 
 the constant current be very strong, or if tetanizing induction currents be used, the cardiac muscle 
 a«sumes a condition resembling, but not identical with, tetanus [Ludwig and Hoffa), and, of course, 
 this results in a fall of the blood pressure [Sigm. Mayer). 
 
J 02 ACTION OF ELECTRICAL STIMULI ON THE HEART. 
 
 When a single induction shock is applied to the ventricle of a frog's heart during systole, it 
 has no apparent effect ; but if it is applied during diastole, the succeeding contraction takes place 
 sooner. The auricles behave in a similar manner. While they are contracted, an induction shock 
 has no effect; if, however, the stimulus is applied during diastole, it causes a contraction, which is 
 followed by systole of the ventricle (Jfildebrand). Even when strong tetanizing induction shocks 
 are applied to the heart, they do not produce tetanus of the entire cardiac musculature, or, as it is 
 said, "the heart knows no tetanus" (Kronecker and Stirling). Small, white, local, wheal-like ele- 
 vations — such as occur when the intestinal musculature is stimulated — appear between the elec- 
 trodes. They may last several minutes. A frog's heart, which yields weak and irregular contrac- 
 tions, may be made to execute regular rhythmical contractions synchronous with the stimuli, if 
 electrical stimuli are used (Bowditch). In this case the weakest stimuli (which are still active) 
 behave like the stronger stimuli — even with the weak stimulus, the heart always gives the strongest 
 contraction possible. Hence, this minimal electrical stimulus is as effective as a " maximal " stimulus 
 (Kronecker and Stirling). 
 
 Human Heart. — v. Ziemssen found that he could not alter the heart beats of the human heart 
 (Frau Serafin, \ 47, 3), even with strong induction currents. The ventricular diastole seemed to 
 be less complete, and there were irregularities in its contraction. By opening and closing, or by 
 reversing a strong constant current applied to the heart, the number of beats was increased, and the 
 increase corresponded with the number of electrical stimuli; thus, when the electrical stimuli were 
 120, 140, 180, the number of heart beats was the same, the pulse beforehand being 80. When 180 
 shocks per minute were applied, the action of the heart assumed the characters of the pulsus 
 alternans (<j 70, 4). Minimal stimuli were also found to act like maximal stimuli. The normal 
 pulse rate of 80 was reduced to 60 and 50, when the number of shocks was reduced in the same 
 ratio. The rhythm became, at the same time, somewhat irregular. In these experiments a strong 
 current is required, and v. Basch found that the same was true for the frog's heart. Even in healthy 
 persons, v. Ziems en ascertained that the energy and rhythm of the heart could be. modified by 
 passing an electrical current through the uninjured chest wall. [In Frau Serafin's case, the elec- 
 trodes were applied to the heart, separated from it merely by the pericardium. Ziemssen found 
 that the faradic current did not modify the heart's action when the thorax was intact, but that the 
 constant current did, if of sufficient strength. Herbert and Dixon Mann obtained negative results 
 with both kinds of electricity in the normal thorax.] 
 
 [Method — The apparatus (Fig. 52) is also well adapted for studying the effect of electrical 
 currents upon the heart. Bowditch, Kronecker and Stirling, and other observers, used the " heart 
 apex," as it does not contract spontaneously for some time after the ligature is applied. One elec- 
 trode is attached to the cannula, and the other is placed in the fluid in which the heart is bathed.] 
 
 [Opening induction shocks, if of sufficient strength, cause the heart to contract, while weak 
 stimuli have no effect; on the other hand, moderate stimuli, when they do cause the heart to con- 
 tract, always cause a maximal contraction, so that a minimal stimulus acts at the same time like a 
 maximal stimulus. The heart either contracts or it does not contract, and when it contracts, the 
 result is always a "maximal" contraction. Bowditch found that the excitability of the heart 
 was increased by its own movements, so that after a heart had once contracted, the strength 
 of the stimulus required to excite the next contraction may be greatly diminished, and yet the 
 stimulus be effectual. Usually, the amplitude of the first beat so produced is not so great as 
 the second beat, and the second is less than the third, so that a " staircase " (" Treppe ") of beats 
 of successively greater extent were produced (Fig. 54). This staircase arrangement occurs even when 
 the strength of the stimulus is kept constant, so that the production of one contraction facilitates 
 the occurrence of the succeeding one. A staircase arrangement of the pulsations is also seen in 
 Luciani's groups (p. 100). The question, whether a stimulus will cause a contraction, depends 
 upon what particular phase the heart is in when the shock is applied. Even comparatively weak 
 stimuli will cause a heart to contract, provided the stimuli are applied at the proper moment and in 
 the proper tempo, i. t., to say, they become what are called " infallible." If stimuli are applied to 
 the heart at intervals which are longer than the time the heart takes to execute its contraction, they 
 are effectual or " adequate ; " but if they are applied before the period of pulsation comes to an 
 end, then they are ineffectual (Kronecker). It is quite clear, therefore, that the relation of the 
 strengtii of the stimulus to the extent of the contraction of the cardiac muscle is quite different from 
 what occurs in a muscle of the skeleton, where, within certain limits, the amplitude of the contrac- 
 tion bears a relation to the stimulus, while in the heart the contraction is always maximal.^ 
 
 (d) Chemical Stimuli. — Many chemical substances, when applied in a dilute solution to the 
 inner surface of the heart, increase the heart beats, while if they are concentrated or allowed to act 
 too long, they diminish the heart beats and paralyze it. Bile (Budge), bile salts (Rohrig) diminish 
 the heart beats (also when they are absorbed into the blood, as in jaundice) ; in very dilute solu- 
 tions, both increase the heart beats (Landois). A similar result is produced by acetic, tartaric, citric, 
 (Bobrik) and phosphoric acids (Leyden). Chloroform and ether, applied to the inner surface, 
 rapidly diminish the heart beats, and then paralyze it; but very small quantities of ether (1 per 
 cent.) accelerate the heart beat of the frog (Kronecker and M' ' GregorRoberlson), while a solution 
 of \% to 2 per cent, passed through the heart, arrests it temporarily or completely. Dilute solu- 
 tions of opium, strychnia or alcohol applied to the endocardium increase the heart beats (C. 
 
NATURE OF A CARDIAC CONTRACTION. 103 
 
 Ludwig) ; if concentrated, they rapidly arrest its action. Chloral-hydrate paralyzes the heart (P. 
 v. Rokitansky). 
 
 Action of Gases. — When blood containing different gases was passed through a frog's heart, 
 Klug found that blood containing sulphurous acid rapidly and completely killed the heart ; chlorine 
 stimulated the heart at first, and ultimately killed it; and laughing gas rapidly killed it also. Blood 
 containing sulphuretted hydrogen paralyzed the heart without stimulating it. Carbonic oxide also 
 paralyzed it, but if fresh blood was transfused the heart recovered. [Blood containing O excites the 
 heart (Caslell), while the presence of much C0 2 paralyzes it, and the presence of C0 2 is more 
 injurious than the want of O. H and N have no effect.] 
 
 Rossbach found on stimulating the ventricle of a frog's heart at a circumscribed area, either 
 mechanically, chemically, or electrically, during systole, that the part so stimulated relaxes in partial 
 diastole. The immediate direct after effect of this stimulation is, that the muscular fibres in the part 
 irritated remain somewhat shriveled. This part ceases to act, and has lost its vital functions. If 
 the stimulus is applied during diastole, the part irritated always relaxes sooner, and its diastole lasts 
 longer than does that of the parts which were not stimulated. If weak stimuli are allowed to act 
 for a long time upon any part of the ventricle of a frog's heart, the part so stimulated always relaxes 
 sooner than the non-stimulated parts, and its diastole is also prolonged. 
 
 Cardiac Poisons are those substances whose action is characterized by special effects upon the 
 movements of the heart. Among these are neutral salts of potash. [Until 1863 it was believed 
 that these salts were just as slightly active on the heart as the soda salts, but Bernard and Grandeau 
 showed that very small doses of these salts produced death, the heart standing still in diastole. An 
 excised frog's heart ceases to beat after one-half to one minute, when it is placed in a 2 per cent, 
 solution of potassic chloride.] Even a very dilute solution of yellow prussiate of potash injected 
 into the heart of a frog causes the ventricle to stand still in systole. 
 
 As early as 1691, Clayton and Moulin showed the poisonous action of potassium sulphate and 
 alum, as compared with the non-poisonous action of sodium chloride, which was demonstrated by 
 Courten, in 1679. Antiar (Java arrow poison) causes the ventricle to stand still in systole and the 
 auricles in diastole. Some heart poisons, in small doses, diminish the heart's action, and in large 
 doses not unfrequently accelerate it, e. g., digitalis, morphia, nicotin. Others, when given in small 
 doses, accelerate its action, and in large doses slow it — veratria, aconitin, camphor. 
 
 Special Actions of Cardiac Poisons. — The complicated actions of various poisons upon the 
 heart have led observers to suppose that there are various intra-cardiac mechanisms on which these 
 substances may act. Besides the muscular fibres of the heart and its automatic ganglia, some toxi- 
 cologists assume that there are inhibitory ganglia into which the inhibitory fibres of the vagus pass, 
 and accelerator ganglia, which are connected with the accelerating nerve fibres of the heart. Both 
 the inhibitory and accelerator ganglia are connected with the automatic ganglia by conducting 
 channels. , 
 
 Muscarin stimulates permanently the inhibitory ganglia, so that the heart stands still (Schmiede- 
 berg and Koppe). As atropin and daturin paralyze these ganglia, the stand-still of the heart brought 
 about by muscarin may be set aside by atropin. [If a frog's heart be excised and placed in a watch 
 glass, and a few drops of a very dilute solution of muscarin be placed on it with a pipette, it ceases 
 to beat within a few minutes, and will not beat again. If, however, the muscarin be removed, and 
 a solution of atropine applied to the heart, it will resume its contractions after a short time.] Physos- 
 tigmin [Calabar bean] excites the energy of the cardiac muscle to such an extent, that stimulation 
 of the vagus no longer causes the heart to stand still. Iodine-aldehyd, chloroform, and chloral- 
 hydrate paralyze the automatic ganglia. The heart stands still, and it cannot be made to contract 
 again by atropine. The cardiac muscle itself remains excitable after the action of muscarin and 
 iodine-aldehyd, so that if it be stimulated it contracts. [According to Gaskell, antiarin and digitalin 
 solutions produce an alteration in the condition of the muscular tissue of the apex of the heart of 
 the same nature as that produced by the action of a very dilute alkali solution, while the action of a 
 blood solution containing muscarin closely resembles that of a dilute acid solution (p. ioo, \ 65).] 
 
 [Nature of a Cardiac Contraction. — The question as to whether this is a 
 simple contraction or a compound tetanic contraction has been much discussed. 
 This much is certain, that the systolic contraction of the heart is of very much 
 longer duration (8 to 10 times) than the contraction of a skeletal muscle produced 
 by stimulation of its motor nerve. When the sciatic nerve of a nerve muscle 
 preparation (" rheoscopic limb ") is adjusted upon a contracting heart, a simple 
 secondary twitch of the limb, and not a tetanic spasm, is produced when the 
 heart (auricle or ventricle) contracts. This of itself is not sufficient proof that the 
 systole is a simple spasm, for tetanus of a muscle does not in all cases give rise to 
 secondary tetanus in the leg of a rheoscopic limb. Thus, a simple " initial " con- 
 traction occurs when the nerve is applied to a muscle tetanized by the action of 
 strychnia, and the contracted diaphgram gives a similar result. The question 
 whether the heart can be tetanized, has been answered in the negative, and as yet 
 
104 
 
 •THE CAKDIO-PNEUMATIC MOVEMENT. 
 
 it has not been shown that the heart can be tetanized in the same way that a skel- 
 etal muscle is tetanized.] 
 
 The peripheral or extra-cardiac nerves will be discussed in connection with 
 the Nervous System (§ 369 and 370). 
 
 59. THE CARDIO-PNEUMATIC MOVEMENT.— As the heart 
 within the thorax occupies a smaller space during the systole than during the dias- 
 tole, it follows that when the glottis is open, air must be drawn into the chest when 
 the heart contracts; whenever the heart relaxes, i. <?., during diastole, air must be 
 expelled through the open glottis. But we must also take into account the degree 
 to which the larger intra-thoracic vessels are filled with blood. These movements 
 of the air within the lungs, although slight, seem to be of importance in hybernat- 
 ing animals. In animals in this condition, the agitation of the gases in the lungs 
 favors the exchange of C0 2 and O in the lungs, and this slow current of air is 
 sufficient to aerate the blood passing through the lungs. [Ceradini called the 
 diminution of the volume of the entire heart which occurs during systole meio- 
 cardia, and the subsequent increase of volume when the heart is distended to its 
 maximum, auxocardia.] 
 
 Fig. 56. 
 
 Landois' cardio-pneumograph, and the curves obtained therewith. A and B, from man ; i and 2 correspond to the 
 periods of the first and second heart sounds ; C, from dog; B, method of using the apparatus. * 
 
 Method. — The cardio-pneumatic movements, i. e., the movement of the respiratory gases de- 
 pendent on the movements of the heart and great vessels, may be demonstrated in animals and man. 
 A manometric flame may be used. Insert one limb of a Y-tube into the opened trachea of an 
 animal, while the other limb passes to a small gas jet, and connect the other tube with a gas jet. 
 It is clear that the movements of the heart will affect the column of gas, and thus affect the flame. 
 Large animals previously curarized are best. It may also be done in man by inserting the tube 
 into one nostril, while the other nostril and the mouth are closed. [A simpler and less irritating 
 plan is to fill a wide curved glass tube with tobacco smoke, and insert one end of the tube into one 
 nostril while the other nostril and the mouth are closed. If the glottis be kept open, and respiration 
 be stopped, then the movements of the column of smoke within the tube are obvious.] 
 
 Cardio- Pneumograph. — Ceradini employed a special instrument, while Landois uses his cardio- 
 pneumograph, which consists of a tube (D), about I inch in diameter and 6 to 8 inches in length ; 
 the tube is bent at a right angle, and communicates with a small metal capsule about the size of a 
 saucer (T), over which a membrane composed of collodion and castor oil is loosely stretched. To 
 this membrane is attached a glass rod (H) used as a writing style, which records its movements on 
 a glass plate (S) moved by clock work. A small valve (K) is placed on the side of the tube (D), 
 which enables the experimenter to breathe when necessary. The tube ( D) is held in an air-tight 
 manner between the lips, the nostrils being closed, the glottis open, and respiration stopped. Fig. 
 56, A, B, C, are curves obtained in this way. In them we observe — 
 
INFLUENCE OF THE RESPIRATION ON THE HEART. 105 
 
 (a) At the moment of the first sound (i), the respiratory gases undergo a sharp expiratory move- 
 ment, because at the moment of the first part of the ventricular systole the blood of the ventricle has 
 not left the thorax, while venous blood is streaming into the right auricle through the venae cavae, 
 and because the dilating branches of the pulmonary artery compress the accompanying bronchi. 
 The blood of the right ventricle has not yet left the thorax, it passes merely into the pulmonary 
 circuit. The expiratory movement is diminished somewhat by (a) the muscular mass of the ventricle 
 occupying slightly less bulk during the contraction, and (b) owing to the thoracic cavity being slightly 
 increased by the fifth intercostal space being pushed forward by the cardiac impulse. 
 
 (b) Immediately after (i ) there follows a strong inspiratory current of the respiratory gases. As 
 soon as the blood from the root of the aorta reaches that part of the aorta lying outside the thorax, 
 more blood leaves the chest than passes into it simultaneously through the venae cava;. 
 
 (c) After the second sound (at 2), indicated sometimes by a slight depression in the apex of the 
 curve, the arterial blood accumulates, and hence there is another expiratory movement in the curve. 
 
 («") The peripheral wave movements of the blood from the thorax cause another inspiratory 
 movement of the gases. 
 
 (e) More blood flows into the chest through the veins, and the next heart beat occurs. 
 
 60. INFLUENCE OF THE RESPIRATORY PRESSURE ON 
 THE DILATATION AND CONTRACTION OF THE HEART. 
 
 — The variation in pressure to which all the intra-thoracic organs are subjected, 
 owing to the increase and decrease in the size of the chest caused by the respi- 
 ratory movements, exerts an influence on the movements of the heart, as was 
 proved by Carson in 1820, and by Donders in 1854. Examine first the relations 
 in different passive conditions of the thorax, when the glottis is open. 
 
 The diastolic dilatation of the cavities of the heart (excluding the pressure of 
 the venous blood and the elastic stretching of the relaxed muscle wall) is funda- 
 mentally due to the elastic traction of the lungs. This is stronger the more the 
 lungs are distended (inspiration), and is less active the more the lungs are con- 
 tracted (expiration). Hence it follows : — 
 
 (1) When the greatest possible expiratory effort is made (of course, with the 
 glottis open) only a small amount of blood flows into the cavities of the heart ; 
 the heart in diastole is small and contains a small amount of blood. Hence the 
 systole must also be small, which further gives rise to a small pulse beat. 
 
 (2) On taking the greatest possible inspiration, and therefore causing the 
 greatest stretching of the elastic tissue of the lungs, the elastic traction of the 
 lungs is, of course, greatest (30 mm. Hg — Donders). This force may act so 
 energetically as to interfere with the contraction of the thin-walled atria and 
 appendices, in consequence of which these cavities do not completely empty 
 themselves into the ventricles. The heart is in a state of great distention in 
 diastole, and is filled with blood ; nevertheless, in consequence of the limited 
 action of the auricles, only small pulse beats are observed. In several individuals 
 Donders found the pulse to be smaller and slower ; afterward it became larger 
 and faster. 
 
 (3) When the chest is in a position of moderate rest, whereby the elastic 
 traction is moderate (7.5 mm. Hg — Donders), we have the condition most 
 favorable to the action of the heart — sufficient diastolic dilatation of the cavities 
 of the heart, as well as unhindered emptying of them during systole. 
 
 A very important factor is the influence exerted upon the action of the heart, 
 by the voluntary increase or diminution of the intra-thoracic pressure. 
 
 (1) Valsalva's Experiment. — If the thorax is fixed in the position of 
 deepest inspiration, and the glottis be then closed, and if a powerful expiratory 
 effort be made by bringing into action all the expiratory muscles, so as to contract 
 the chest, the cavities of the heart are so compressed that the circulation of the 
 blood is temporarily interrupted. In this expiratory phase the elastic traction is 
 very limited, and the air in the lungs being under a high pressure also acts upon 
 the heart and the intra-thoracic great vessels. No blood can pass into the thorax 
 from without ; hence the visible veins swell up and become congested, the blood 
 in the lungs is rapidly forced into the left ventricle by the compressed air in the 
 lungs, and the blood soon passes out of the chest. Hence the lungs and the 
 
106 
 
 INFLUENCE OF THE RESPIRATION ON THE HEART. 
 
 heart contain little blood. Hence, also, there is a greater supply of blood in the 
 systemic than in the pulmonary circulation and the heart. The heart sounds dis- 
 appear, and the pulse is absent {£. H. Weber, Danders). 
 
 (2) J. Miiller's Experiment. — Conversely, if after the deepest possible 
 expiration the glottis be closed, and the chest be now dilated with a great inspira- 
 tory effort, the heart is powerfully dilated, the elastric traction of the lungs, and 
 the very attenuated air in these organs act so as to dilate the cavities of the heart 
 in the direction of the lungs. More blood flows into the right heart, and in pro- 
 portion as the right auricle and ventricle can overcome the traction outward, the 
 blood vessels of the lungs become filled with blood, and thus partly occupy the 
 lung space. Much less blood is driven out of the left heart, so that the pulse may 
 disappear. Hence, the heart is distended with blood and the lungs are congested, 
 
 Fig. 57. 
 
 Apparatus for demonstrating the action of inspiration, IT, and expiration, I, on the heart and on the blood stream. 
 P, p, lungs ; H, h, heart ; L, /, closed glottis ; M, m, manometers : E, e, ingoing blood stream, vein ; A, a, out- 
 going blood stream, artery ; D, diaphragm during expiration ; d, during inspiration. 
 
 while the aortic system contains a small amount of blood, i. <?., the systemic cir- 
 culation is comparatively empty, while the heart and the pulmonary vessels are 
 engorged with blood. 
 
 In normal respiration the air in the lungs during inspiration is under slight 
 pressure, while during expiration the pressure is higher, so that these conditions 
 favor the circulation ; inspiration favors the supply of blood (and lymph) through 
 the venae cavse, and favors the occurrence of diastole. In operations where the 
 axillary or jugular vein is cut, air may be sucked into the circulation during inspira- 
 tion, and cause death. Expiration favors the flow of blood in the aorta and its 
 branches, and aids the systolic emptying of the heart. The arrangement of the 
 valves of the heart causes the blood to move in a definite direction through it. 
 
 The elastic traction of the lungs aids the lesser circulation through the lungs 
 
INFLUENCE OF THE RESPIRATION ON THE HEART. 107 
 
 within the chest ; the blood of the pulmonary capillaries is exposed to the pressure 
 of the air in the lungs, while the blood in the pulmonary veins is exposed to a 
 less pressure, as the elastic traction of the lungs, by dilating the left auricle, favors 
 the outflow from the capillaries into the left auricle. The elastic traction of the 
 lungs acts slightly as a disturbing agent on the right ventricle, and, therefore, on 
 the movement of blood through the pulmonary artery, owing to the overpowering 
 force of the blood stream through the pulmonary artery, as against the elastic 
 traction of the lungs (Danders). 
 
 The above apparatus (Fig. 57) shows the effect of the inspiratory and expiratory movements on 
 the dilatation of the heart, and on the blood stream in the large blood vessels. The large glass vessel 
 represents the thorax ; the elastic membrane, D, the diaphragm ; P, /, the lungs ; L, the trachea 
 supplied with a stop-cock to represent the glottis ; H, the heart ; E, the venae cavse ; A, the aorta. 
 If the glottis be closed, and the expiratory phase imitated by pushing up D as in I, the air in P, P is 
 compressed, the heart, H, is compressed, the venous valve closes, the arterial is opened, and the 
 fluid is driven out through A. The manometer, M, indicates the intra- thoracic pressure. If the 
 glottis be closed, and the inspiratory phase imitated, as in W,p,p and h are dilated, the venous 
 ' valve opens, the arterial valve closes ; hence, venous blood flows from e into the heart. Thus, 
 inspiration always favors the venous stream, and hinders the arterial ; while expiration hinders the 
 venous, and favors the arterial stream. If the glottis L and / be open, the air in P, P, /, p will be 
 changed during the respiratory movements D and d, so that the action on the heart and blood 
 vessels will be diminished, but it will still persist, although to a much less extent. 
 
THE CIRCULATION. 
 
 61. THE FLOW OF FLUIDS THROUGH TUBES.— Toricelli's Theorem (1643^ 
 
 states that the velocity of efflux (v) of a fluid — through an opening at 
 the bottom of a cylindrical vessel — is exactly the same as the velocity 
 which a body falling freely would acquire, were it to fall from the 
 surface of the fluid to the base of the orifice of the outflow. If h be the 
 height of the propelling force, the velocity of efflux is given by the 
 formula — 
 
 v = j/ 2 g h (where g = 9.8 metres). 
 
 The rapidity of outflow increases (as shown experimentally) with increase 
 in the height of the propelling force, h. The former occurs in the ratio, 
 I, 2, 3, when h increases in the ratio, I, 4, 9, i. e., the velocity of efflux 
 is as the square root of the height of the propelling force. Hence, it fol- 
 lows that the velocity of efflux depends upon the height of the liquid 
 above the orifice of outflow, and not upon the nature of the fluid. 
 
 Resistance. — Toricelli's theorem, however, is only valid when all 
 resistance to the outflow is absent ; but, in fact, in every physical experi- 
 ment such resistance exists. Hence, the propelling force, k, has not only 
 to cause the efflux of the fluid, but has also to overcome resistance. 
 These two forces may be expressed by the heights of two columns of 
 water placed over each other, viz., by the height of the column of water 
 causing the outflow, F, and the height of the column, D, which over- 
 comes the resistance opposed to the outflow of the fluid. So that 
 h = F + D. 
 
 62. PROPELLING FORCE— VELOCITY OF THE CURRENT, AND LAT- 
 ERAL PRESSURE. — In the case of a fluid flowing through a tube, which it fills completely, 
 we have to consider the propelling force, h, causing the fluid to flow through the various sections of- 
 the tube. The amount of the propelling force depends upon two factors : — 
 
 (1) On the velocity of the cui rent, v ; 
 
 (2) On the pressure (amount of resistance) to which the fluid is subjected at the various parts of 
 the tube, D. 
 
 ( 1 ) The velocity of the current, v, is estimated — (a) from the lumen, /, of the tube ; and (B) from 
 the quantity of fluid, q, which flows through the tube in the unit of time. So that v = a : I. Both 
 values, q as well as /, can be accurately measured. (The circumference of a round tube whose 
 
 diameter = *^is 3.14.1/. The sectional area (lumen of the tube) is /=i-5 .d*). Having in this 
 
 4 
 way determined v, from it we may calculate the height of the column of fluid, F, which will give this 
 velocity, ;'. e., the height from which a body must fall in vacuo, in order to attain the velocity, v. 
 
 v 2 
 In this case F = — (where g= the distance traversed by a falling body in I sec. = 4.9 metres). 
 
 (2) The pressure, D (amount of resistance), is measured directly by placing manometers at 
 different parts of the tube (Fig. 59). 
 
 The propelling force at any part of the tube is 
 
 A = F + D; 
 
 Cylindrical vessel filled with 
 water, k, height of the 
 column of fluid ; D, 
 height of column of fluid 
 required to overcome the 
 resistance ; and F, height 
 of column of fluid caus- 
 ing the efflux. 
 
 h = — -f D. {Bonders) 
 
 This is proved experimentally by taking a tall cylindrical vessel, A, of sufficient size, which is kept 
 filled with water at a constant level, h. The outflow rigid tube, a, b, has in connection with it a 
 number of tubes placed vertically, I, 2, 3, constituting a piezometer. At the end of the tube, i, there 
 is an opening with a short tube fixed in it, from which the water issues to a constant height, provided 
 the level of h is kept constant. The height to which it rises depends on the height of the column, 
 of fluid causing the velocity, F. As the pressure in the manometric tubes, D 1 D z , D s , can be read 
 off directly, the propelling force of the water at the sections of the tubes, I, II, III, is — 
 
 /5 = F + D 1 ; F + D^; F + D*. 
 
 108 
 
ESTIMATION OF RESISTANCE. 
 
 109 
 
 At the end of the tube, b, where D* = O, A = F + O, i. e., A = F. In the cylinder itself it is the 
 constant pressure, A, which causes the movement of the fluid. 
 
 It is clear that the propelling force of the water gradually diminishes as we pass from the part 
 where the fluid passes out of the cylinder into the tube toward the end of the tube, b. The water 
 in the pressure cylinder, falling from the height, A, only rises as high as F at b. This diminution of 
 the propelling power is due to the presence of resistances, which oppose the current in the tube, 
 i. e., part of the energy is transformed into heat. As the propelling power at b is represented only by 
 F, while in the vessel it is A, the difference must be due to the sum of the resistances, D = k — F; 
 hence it follows that h = F + D. [Bonders). 
 
 ESTIMATION OF RESISTANCE.— Estimation of the Resistance.— When a fluid 
 flows through a tube of uniform calibre, the propelling force, A, diminishes from point to point, pn 
 account of the uniformly acting resistance, hence the sum of the resistances in the whole tube is 
 directly proportional to its length. In a uniformly wide tube, fluid flows through each sectional 
 area with equal velocity, hence v and also F are equal in all parts of the tube. The diminution 
 which A (propelling force) undergoes can only occur from a diminution of pressure D, as F remains 
 the same throughout (and A = F + D). Experiment with the pressure cylinder shows that, as a 
 matter of fact, the pressure toward the outflow end of the tube becomes gradually diminished. 
 
 In a uniformly wide tube, tAe AeigAt of tAe pressure in tAe manometers expresses tAe resistances 
 opposed to tAe current of fluid wAicA it Aas to overcome in its course from tAe point investigated to 
 tAe free orifice of efflux. 
 
 Nature of the Resistance. — The resistance opposed to the flow of a fluid depends upon the 
 cohesion of the particles of the fluid among themselves. During the current, the outer layer of 
 fluid which is next the wall of the tube, and which moistens it, is at rest (Girard, Poiseuille). 
 
 A cylindrical vessel filled with water, a, /<, outflow tube, along which are placed at intervals vertical tubes, i , 2 , 3 , to 
 
 estimate the pressure. 
 
 All the other layers of fluid, which may be represented as so many cylindrical layers, one inside the 
 other, move more rapidly as we proceed toward the axis of the tube, the axial thread or stream 
 being the most rapidly moving part of the liquid. On account of the movement of the cylindrical 
 layers, one within the other, a part of the propelling energy must be used up. The amount of the 
 resistance greatly depends upon the amount of tAe cohesive force which the particles of the fluid 
 have for each other ; the more firmly the particles cohere with each other, the greater will be the 
 resistance, and vice versd. Hence, the sticky blood current experiences greater resistance than water 
 or ether. 
 
 Heat diminishes the cohesion of the particles, hence it also diminishes the resistance to the flow 
 of a current. These resistances are first developed by, and result from, the movement of the particles 
 of the fluid, they being, as it were, torn from each other. The more rapid tAe current, therefore, 
 i. e., the larger the number of particles of fluid which are pulled asunder in the unit of time, the 
 greater will be tAe sum of tAe resistance. As already mentioned, the layer of _fluid lying next the 
 tube, and moistening it, is at rest, hence the material which composes the tube exerts no influence 
 on the resistance. " 
 
 EFFECT OF TUBES OF UNEQUAL CALIBRE.— Unequal Diameter.— When 
 the velocity of the current is uniform, the resistance depends upon the diameter of the tube — the 
 smaller the diameter, the greater the resistance ; the greater the diameter, the less the resistance. 
 The resistance in narrow tubes, however, increases more rapidly than the diameter of the tube 
 decreases, as has been proved experimentally. 
 
 In tubes of unequal calibre, at different parts of their course, the velocity of the current varies — 
 it is slower in the wide part of the tube and more rapid in the narrow parts. As a general rule, in 
 
110 MOVEMENT OF FLUIDS IN ELASTIC TUBES. 
 
 tubes of unequal diameter the velocity of the current is inversely proportional to the diameter of the 
 corresponding section of the tube; i. e., if the tube be cylindrical, it is inversely proportional to the 
 square of the diameter of the circular transverse section. In tubes of uniform diameter, the pro- 
 pelling force of the moving fluid diminishes uniformly from point to point, but in tubes of unequal 
 calibre it does not diminish uniformly. As the resistance is greater in narrow tubes, of course the 
 propelling force must diminish more rapidly in them than in wide tubes. Hence, within the wide 
 parts of the tube the pressure is greater than the sum of the resistances still to be overcome, while 
 in the narrow portions it is less than these. 
 
 Tortuosities and Bending of the Vessels add new resistance, and the fluid presses more 
 strongly on the convex side than on the concave side of the bend, and there the resistance to the 
 flqw is greater than on the concave side. 
 
 Division of a tube into two or more branches is a source of resistance, and diminishes the pro- 
 pelling power. When a tube divides into two smaller tubes, of course some of the particles of the 
 fluid are retarded, while others are accelerated, on account of the unequal velocities of the different 
 layers of the fluid. Many particles which had the greatest velocity in the axial layer come to lie 
 more toward the side of the tube, where they move more slowly; and, conversely, many of those 
 lying in the outer layers reach the centre, where they move more rapidly. Hence, some of the 
 propelling force is used up in this process, and the pulling asunder of the particles where the tube 
 divides acts in a similar manner. If two tubes join to form one tube, new resistance is thereby 
 caused, which must diminish the propelling force. The sum of the mean velocities in both branches 
 is independent of the angle at which division takes place [Jacobson). If a branch be opened from 
 a tube, the principal current is accelerated to a considerable extent, no matter at what angle the 
 .branch may be given off. 
 
 63. CURRENTS THROUGH CAPILLARY TUBES.— Poiseuille proved, experiment- 
 ally, that the flow in the capillaries is subject to special conditions : — 
 
 (1) The quantity of fluid which flows out of the same capillary tube is proportional to the 
 pressure. 
 
 (2) The time necessary for a given quantity of fluid to flow out (with the like pressure, diameter 
 of tube and temperature), is proportional to the length of the tubes. 
 
 (3) The product of the outflow (other things being equal) is as the fourth power of the diameter. 
 
 (4) The velocity of the current is proportional to the pressure and to the square of the diameter, 
 and inversely proportional to the length of the tube. 
 
 (5) The resistance in the capillaries is proportional to the velocity of the current. 
 
 64. MOVEMENT OF FLUIDS AND WAVE MOTION IN ELASTIC TUBES.— 
 
 ( 1 ) When an uninterrupted uniform current flows through an elastic tube, it follows exactly the 
 same laws as if the tube had rigid walls. If the propelling power increases or diminishes, the 
 elastic tubes become wider or narrower, and they behave, as far as the movement of the fluid is 
 concerned, as wider or narrower rigid tubes. 
 
 (2) Wave Motion. — If, however, more fluid be forced in jerks into an elastic tube, i.e., inter- 
 ruptedly, the first part of the tube dilates suddenly, corresponding to the quantity of fluid propelled 
 into it. The jerk communicates an oscillatory movement to the particles of the fluid, which is 
 communicated to all the fluid particles from the beginning to the end ot the tube ; a positive wave is 
 thus rapidly propagated throughout the whole length of the tube. If we imagine the elastic tube to 
 be closed at its peripheral end, the positive wave will be reflected from the point of occlusion, and 
 it may be propagated to and iro through the tube until it finally disappears. In such a closed tube 
 a sudden jet of fluid produces only a wave movement, i.e., only a vibratory movement, or an altera- 
 tion in the shape of the liquid, there being no actual translation of the particles along the tube. 
 
 (3) If, however, fluid be pumped interruptedly or by jerks into an elastic tube filled with fluid, 
 in which there is already a continuous current, the movement of the current is combined with the 
 wave movement. We must carefully distinguish the movement of the current of the fluid, i.e., 
 the translation of a mass of fluid through the tube, from the wave movement, the oscillatory move- 
 ment, or movement of change of form in the column of fluid. In the former, the particles are 
 actually translated, while in the latter they merely vibrate. The current in elastic tubes is slower 
 than the wave movement, which is propagated with great rapidity. 
 
 This last case obtains in the arterial system. '1 he blood in the arteries is already in a state of 
 continual movement, directed from the aorta to the capillaries (movement of the current of blood) ; 
 by means of the systole of the left ventricle, a quantity of fluid is suddenly pumped into the aorta, 
 and causes a positive wave [pulse wave), which is propagated with great rapidity to the terminations 
 of the arteries, while the current of the blood itself moves much more slowly. 
 
 Rigid and Elastic Tubes. — It is of importance to contrast the movement of fluids in rigid and 
 in elastic tubes. If a certain quantity of fluid be forced into a rigid lube under a certain pressure, 
 the same quantity of fluid will flow out at once at the other end of the tube, provided there be no 
 special resistance. In an elastic tube, immediately after the forcing in of a certain quantity of fluid, 
 at first only a small quantity flows out, and the remainder flows out only after the propelling force 
 has ceased to act. 
 
 If an equal quantity of fluid be periodically injected into a rigid tube, with each jerk an equal 
 
STRUCTURE OF ARTERIES. 
 
 Ill 
 
 quantity is forced out at the other end of the tube, and the outflow lasts exactly as long as the jerk 
 or the contraction, and the pause between two periods of outflow is exactly the same as between 
 the two jerks or contractions. In an elastic tube it is different, as the outflow continues for a time 
 after the jerk; hence, it follows that a continuous outflow current will be produced in elastic tubes 
 when the time between two jerks is made shorter than the duration of the outflow after the jerk has 
 been completed. When fluid is pumped periodically into rigid tubes, it causes a sharp, abrupt out- 
 flow synchronous with the inflow, and the outflow becomes continuous only when the inflow is con- 
 tinuous and uninterrupted. In elastic tubes an intermittent current, under the above conditions, 
 causes a continuous outflow, which is increased with the systole or contraction. 
 
 65. STRUCTURE AND PROPERTIES OF THE BLOOD 
 VESSELS. — In the body, the large vessels carry the blood to and from the 
 various tissues and organs, while the thin-walled capillaries bring the blood into 
 intimate relation with the tissues. Through the excessively thin walls of the 
 capillaries the fluid part of the blood transudes, to nourish the tissues outside the 
 capillaries. [At the same time, fluids pass from the tissues into the blood. Thus, 
 there is an exchange between the blood and the fluids of the tissues. The fluid, 
 after it passes into the tissues, constitutes the lymph, and acts like a stream irrigat- 
 ing the tissue elements.] 
 
 I. The Arteries are distinguished from veins by their thicker walls, due to the 
 greater development of smooth, muscular and elastic tissues; the middle coat 
 (tunica media) of the arteries is specially thick, 
 while the outer coat (t. adventitia) is relatively thin. 
 [The absence of valves is by no means a character- 
 istic feature.] 
 
 The arteries consist of three coats (Fig. 60). 
 (1) The Tunica intima, or inner coat, consists 
 of a layer of {a) irregular, long, fusiform, nucle- 
 ated, squamous cells, forming the excessively thin, 
 transparent endothelium {His, 1866), immediately 
 in contact with the blood stream. [Like other 
 endothelial cells, these cells are held together by a 
 cement substance which is blackened by the action 
 of silver nitrate.] 
 
 Outside this lies a very thin, more or less fibrous, 
 layer — sub-epithelial layer — in which numerous 
 spindle or branched protoplasmic cells lie em- 
 bedded within a corresponding system of plasma 
 canals. Outside this is an elastic lamina (J>), 
 which, in the smallest arteries, is a structureless or 
 fibrous elastic membrane — in arteries of medium 
 size it is a fenestrated membrane (Henle), while in 
 the largest arteries there may be several layers of 
 elastic laminae or fenestrated elastic membrane 
 mixed with connective tissue. [In some arteries 
 the elastic membrane is distinctly fibrous, the fibres 
 being chiefly arranged longitudinally. It may be 
 stripped off, when it forms a brittle elastic mem- 
 brane, which has a great tendency to curl up at its 
 margins. In a transverse section of a middle- 
 sized artery it appears as a bright, wavy line, but 
 the curves are probably produced by the partial collapse of the vessel. It forms 
 an important guide to the pathologist in enabling him to determine which coat of 
 the artery is diseased.] 
 
 • In middle-sized and large arteries a few non-striped muscular fibres are disposed 
 longitudinally between the elastic plates or laminae (K. Bardeleben). Along with 
 the circular muscular fibres of the middle coat, they may act so as to narrow the 
 artery, and they may also aid in keeping the lumen of the vessel open and of 
 
 Small artery, to show the various layers 
 which compose its walls, a, endothe- 
 lium ; b t internal elastic lamina ; e, cir- 
 lar muscular fibres of the middle coat ; 
 d, the connective-tissue outer coat (t. 
 adventitia). 
 
112 STRUCTURE OF ARTERIES. 
 
 uniform calibre. It is not probable that when they act by themselves they dilate 
 the vessel. 
 
 (2) The Tunica media, or middle coat, contains much non-striped muscle (e), 
 which in the smallest arteries consists of transversely disposed non-striped muscu- 
 lar fibres lying between the endothelium and the T. adventitia, while a finely 
 granular tissue with few elastic fibres forms the bond of union between them. As 
 we proceed from the very smallest to the small arteries, the number of muscular 
 fibres become so great as to form a well-marked fibrous ring of non-striped muscle, 
 in which there is comparatively little connective tissue. In the large arteries the 
 amount of connective tissue is considerably increased, and between the layers of 
 fine connective tissue numerous (as many as 50) thick, elastic, fibrous or fenes- 
 trated laminae are concentrically arranged. 
 
 A few non-striped fibres lie scattered among these, and some of them are 
 arranged transversely, while a few have an oblique or longitudinal direction. 
 
 The first part of the aorta and pulmonary artery, and the retinal arteries are devoid of muscle. 
 The descending aorta, common iliac, and popliteal have longitudinal fibres between the transverse 
 ones. Longitudinal bundles lying inside the media occur in the renal, splenic and internal sper- 
 
 Fig. 61. 
 
 Capillaries. The outlines of the endothelial cells marked off from each other by the cement which is blackened by 
 the action of silver nitrate. The nuclei of the cells are obvious. 
 
 matic arteries. Longitudinal bundles occur both on the outer and inner surfaces of the umbilical 
 arteries, which are very muscular. 
 
 (3) The Tunica adventitia, or outer coat, in the smallest arteries consists of 
 a structureless membrane with a few connective-tissue corpuscles attached to it ; in 
 somewhat larger arteries there is a layer of fine, fibrous, elastic tissue mixed with 
 bundles of fibrillar connective tissue (d). In arteries of middle size, and in the 
 largest arteries the chief mass consists of bundles of fibrillar connective tissue con- 
 taining connective-tissue corpuscles. The bundles cross each other in a variety 
 of directions, and fat cells often lie between them. Next the media there are 
 numerous fibrous or fenestrated elastic lamellae. In medium-sized and small 
 arteries the elastic tissue next the media takes the form of an independent elastic 
 membrane (Henle's external elastic membrane). Bundles of non-striped muscle, 
 arranged longitudinally, occur in the adventitia of the arteries of the penis, and 
 in the renal, splenic, spermatic, iliac, hypogastric and superior mesenteric arteries. 
 
 II. The capillaries, while retaining their diameter, divide and reunite so as to 
 form networks, whose shape and arrangement differ considerably in different tis- 
 sues. The diameter of the capillaries varies considerably, but as a general rule it 
 
STRUCTURE OF VEINS. 113 
 
 is such as to admit freely a single row of blood corpuscles. In the retina and 
 muscle the diameter is 5-6 jx, and in bone marrow, liver, and choroid 10-20 /x. 
 The tubes consist of a single layer of transparent, excessively thin, nucleated, 
 endothelial cells joined to each other by their margins (Hoyer, Auerbach, Eberth, 
 Aeby, 1865). 
 
 [The nuclei contain a well-marked intra-nuclear plexus of fibrils, like other nuclei.] The cells 
 are more fusiform in the smaller capillaries and more polygonal in the larger. The body of the 
 cell presents the characters of very faintly refractive protoplasm, but it is doubtful whether the body 
 of the cell is endowed with the property of contractility. 
 
 Action of Silver Nitrate.— If a dilute solution (}( per cent.) of silver 
 nitrate be injected into the blood vessels, the cement substance of the endothelium 
 and of the muscular fibres as well,] is revealed by the presence of the black "silver 
 lines. ' ' The blackened cement substance shows little specks and large black slits 
 at different points. It is not certain whether these are actual holes (J. Arnold) 
 through which colorless corpuscles may pass out of the vessels, or are merely 
 larger accumulations of the cement substance. 
 
 [Arnold called these small areas in the black silver lines when they are large stomata, and when 
 small stigmata. They are most numerous after venous congestion, and after the disturbances 
 which follow inflammation of a part {Cohnheim, Winiwarter). They are not always present. The 
 existence of cement substance between the cells may also be inferred from the fact that indigo- 
 sulphate of soda is deposited in it ( Thomd), and particles of cinnabar and China ink are fixed in it, 
 when these substances are injected into the blood (Foa).~\ 
 
 Fine anastomosing fibrils derived from non-medullated nerves terminate in 
 small end buds in relation with the capillary wall ; ganglia in connection with 
 capillary nerves occur only in the region of the sympathetic (Bremer and Wal- 
 deyer). 
 
 [If a capillary is examined in a perfectly fresh condition (while living) and with- 
 out the addition of any reagent, it is impossible to make out any line of demarca- 
 tion between adjacent cells, owing to the uniform refractive index of the entire 
 wall of the tube.] 
 
 The small vessels next in size to the capillaries and continuous with them have 
 a completely structureless covering in addition to the endothelium. 
 
 III. The veins are generally distinguished from the arteries by their lumen 
 being wider than the lumen of the corresponding arteries; their walls are thinner, 
 on account of the smaller amount of non-striped muscle and elastic tissue (the 
 non-striped muscle is not unfrequently arranged longitudinally in veins). They 
 are also more extensile (with the same strain). The adventitia is usually the 
 thickest coat. 
 
 The occurrence of valves is limited to the veins of certain areas. (1) The 
 T. intima consists of a layer of shorter and broader endothelial cells, under 
 which, in the smallest veins, there is a structureless elastic membrane, sub- 
 epithelial layer, which is fibrous in veins somewhat larger in size, but in all cases 
 is thinner than in the arteries. In large veins it may assume the characters of a 
 fenestrated membrane, which is double in some parts of the crural and iliac 
 veins. Isolated muscular fibres exist in the intima of the femoral and popliteal 
 veins. 
 
 (2) The T. media of the larger veins consists of alternate layers of elastic 
 and muscular tissue united to each other by a considerable amount of connective 
 tissue, but this coat is always thinner than in the corresponding arteries. This 
 coat diminishes in the following order in the following vessels : popliteal, veins 
 of the lower extremity, veins of the upper extremity, superior mesenteric, other 
 abdominal veins, hepatic, pulmonary, and coronary veins. The following veins 
 contain no muscle : veins of bone, central nervous system and its membranes, 
 retina, the superior cava, with the large trunks that open into it, the upper part 
 of the inferior cava. Of course, in these cases the media is very thin. In the 
 8 
 
114 
 
 PHYSICAL PROPERTIES OF THE BLOOD VESSELS. 
 
 Fig. 62. smallest veins the media is formed of fine con- 
 
 nective tissue, with very few muscular fibres 
 scattered in the inner part. 
 
 (3) The T. adventitia is thicker than that 
 of the corresponding arteries ; it contains much 
 connective tissue, usually arranged longitudin- 
 ally, and not much elastic tissue. Longitudinally 
 arranged muscular fibres occur in some veins 
 (renal, portal, inferior cava near the liver, veins 
 of the lower extremities). The valves consist 
 of fine fibrillar connective tissue with branched 
 cells. An elastic network exists on their convex 
 surface, and both surfaces are covered by endo- 
 thelium. The valves contain many muscular 
 fibres (Fig. 62). [Ranvier has shown that the 
 shape of the epithelial cells covering the two 
 surfaces of the valves differs. On the side over 
 which the blood passes, they are more elongated 
 than on the cardiac side of the valve, where the 
 long axes of the cell are placed transversely.] 
 
 The sinuses of the dura mater are spaces covered with 
 endothelium. The spaces are either duplicatures of the 
 membrane, or channels in the substance of the tissue itself. 
 
 Cavernous spaces we may imagine to arise by 
 numerous divisions and anastomoses of tolerably large 
 veins of unequal calibre. The vascular wall appears to 
 be much perforated and like a sponge, the internal space 
 being traversed by threads and strands of tissue, which 
 are covered with endothelium on their surfaces, that are 
 in contact with the blood. The surrounding wall consists 
 of connective tissue, which is often very tough, as in the 
 corpus cavernosum, and it not unfrequently contains non- 
 striped muscle. 
 
 Cavernous Formations of an analogous 
 nature on arteries are the carotid gland of the 
 'frog (Fig. 45), and a similar structure on the pulmonary arteries and aorta of the 
 turtle, and the coccygeal gland of man (Luschkd). The last structure is richly 
 supplied with sympathetic nerve fibres, and is a convoluted mass of ampullated 
 or fusiform dilatations of the middle sacral artery {Arnold), surrounded and 
 permeated by non-striped muscle [EbertK). 
 
 Vasa Vasorum. — [These are small vessels which nourish the coats of the arteries and veins. 
 They arise from one part of a vessel and enter the walls of the same or another vessel at a lower 
 level. They break up chiefly in the outer coat, and none enter the inner coat.J In structure they 
 resemble other small blood vessels. The blood circulating in the arterial or venous wall is returned 
 by small veins. 
 
 [Lymphatics. — There are no lymphatics on the inner surface of the muscular coat, or under 
 the intima in large arteries. They are numerous in a gelatinous layer immediately outside the 
 muscular coat, and the same relation obtains in large muscular veins and lymphatic trunks {Hoggari)^\ 
 
 Intercellular Blood Channels. — Intercellular blood channels of narrow calibre, and without 
 walls, occur in the granulation tissue of healing wounds. At first blood plasma alone is found 
 between the formative cells, but afterward the blood current forces blood corpuscles through the 
 channels. The first blood vessels in the developing chick are formed in a similar way from the 
 formative cells of the mesoblast. 
 
 Properties of the Blood Vessels. — The larger blood vessels are cylindrical 
 tubes composed of several layers of various tissues, more especially elastic tissue 
 and plain muscular fibres, and the whole is lined by a smooth layer of endothelium. 
 One of the most important properties is the contractility of the vascular wall, in 
 virtue of which the blood vessel becomes contracted, so that the calibre of the 
 
 ■ Longitudinal section of a vein at the level of 
 a valve, a, hyaline layer of the internal 
 coat ; b, elastic lamina ; c , groups of 
 smooth muscular fibres divided transverse- 
 ly ; d, longitudinal muscular fibres in the 
 adventitia. 
 
PHYSICAL PROPERTIES OF THE BLOOD VESSELS. 115 
 
 vessel, and therefore the supply of blood to a part, are altered. The contractility 
 is due to the plain muscular fibres, which are, for the most part, arranged circu- 
 larly. It is most marked in the small arteries, and of course is absent where no 
 muscular tissue occurs. The amount and intensity of the contraction depend upon 
 the development of the muscular tissue ; in fact, the two go hand-in-hand. [If 
 an artery be exposed in the living body it soon contracts under the stimulus of 
 the atmosphere {J. Hunter) acting upon the muscular fibres.] 
 
 [Action of Alkalies and Acids on the Vascular System. — Gaskell finds that very dilute 
 alkalies and acids have a remarkable effect on the blood vessels and also upon the heart. A very 
 dilute solution of lactic acid (I part to 10,000 parts of saline solution), passed through the blood 
 vessels of a frog, always enlarges the calibre of the blood vessels, while an alkaline solution (1 part 
 sodium hydrate to 10,000 or 20,000 parts saline solution) always diminishes their size, usually to 
 absolute closure, and indeed the artificial constriction of the blood vessels may be almost complete. 
 These fluids are antagonistic to each other as far as regards their action on the calibre of the arteries. 
 Microscopic observations which confirmed these results were also made on the blood vessels of the 
 mylo-hyoid muscle of the frog. Dilute alkaline solutions act on the heart in the same way. After 
 a series of beats, the ventricle stops beating, the stand still being in a state of contraction. Very 
 dilute lactic acid causes the ventricle to stand still in the position of complete relaxation. The 
 action of the acid and alkaline solutions are antagonistic in their action on the ventricle. Gaskell 
 attaches considerable importance to the "tonic" and "atonic" conditions of the whole vascular 
 system produced by very dilute solutions of alkalies and acids respectively.] 
 
 [Other Drugs. — Cash and Brunton find that dilute acids have a tendency to increase the 
 transudation through the vessels and produce (edema of the surrounding tissues. They also ob- 
 served that barium, calcium, strontium, copper, iron, and tin produce contraction of the blood vessels 
 when solutions of their salts are driven through them, while the same effect is produced by very 
 dilute solutions of potassium. Nicotin, atropin, and chloral differ in their action, according to the 
 dose. In these experiments the effect was ascertained by the amount of fluid which flowed out of 
 the vessels in a given time.] 
 
 That the capillaries undergo dilatation and contraction, owing to variations 
 in size of the protoplasmic elements of their walls, must be admitted. 
 
 Strieker has described capillaries as "protoplasm in tubes," and observed that they exhibited 
 movements when stimulated in living animals. Golubew described an active state of contraction of 
 the capillary wall, but he regarded the nuclei as the parts which underwent change. Tarchanoff 
 found that mechanical or electrical stimulation caused a change in the shape and size of the nuclei, 
 so that he regards these as the actively contractile parts. [Severini also attaches great importance 
 to the contractility of the capillaries and especially of their nuclei as influencing the blood stream. 
 Oxygen acts on the nuclei of the capillary wall (membrana nictitans of fro,;) and causes them to 
 swell, while C0 2 has an opposite effect. The circulation through a lung suddenly filled with O 
 or atmospheric air, is at first very rapid, but soon becomes small, while with C0 2 the circulation 
 remains constant.] Strieker's observations were made on the capillaries of tadpoles. These phe- 
 nomena became less marked as the animal became older. Rouget observed the same result in the 
 capillaries of new-born mammals. As the capillaries are excessively thin and delicate, and as they 
 are solt structures, it is obvious that the form of the individual cells must depend to a considerable 
 extent upon the degree to which the vessels are filled with blood. In vessels which are distended 
 with blood the endothelial cells are flattened, but when the capillaries are collapsed, they project 
 more or less into the lumen of the vessel (Jienaut). 
 
 It is a well-known fact that the capillaries present great variations in their diameter at different 
 times. As these variations are usually accompanied by a corresponding contraction or dilatation of 
 the arterioles, it is usually assumed that the variations in the diameter of the capillaries are due to 
 differences of the pressure within the capillaries themselves, viz, to the elasticity of their walls. 
 Every one is agreed that the capillaries are very elastic, but the experiments of Roy and Graham 
 Brown show that they are contractile as well as elastic, and these observers conclude that, under 
 normal conditions, it is by the contractility of the capillary wall as a whole that the diameter of 
 these vessels is changed, and to all appearance their contractility is constantly in action. " The 
 individual capillaries (in all probability) contract or expand in accordance with the requirements of 
 the tissues through which they pass. The regulation of the vascular blood flow is thus more com- 
 plete than is usually imagined" [Hoy and Graham Brown). 
 
 Physical Properties. — Among the physical properties of the blood vessels, 
 elasticity is the most important; their elasticity is small in amount, i. e., they 
 offer little resistance to any force applied to them so as to distend or elongate 
 them, but it is perfect in quality, i. e., the blood vessels rapidly regain their original 
 size and form after the force distending them is removed. 
 
116 THE PULSE. 
 
 [Uses of Elasticity. — The elasticity of the arteries is of the utmost importance in aiding the 
 conversion of the unequal movement of the blood in the large arteries into a uniform flow in the 
 capillaries. E. H. Weber compared the elastic wall of the arteries with the air in the air chamber 
 of a fire-engine. In both cases an elastic medium is acted upon— the air in the one case and the 
 elastic tissue in the other — which in turn presses upon the fluid, propelling it onward continually, 
 while the action of the pump or the heart, as the case may be, is intermittent. The ordinary spray 
 producer acts on this principle. A uniform spray or jet is obtained by pumping intermittently, but 
 only when the resistance is such as to bring into action the elasticity of the bag between the pump 
 and the spray orifice.] 
 
 According to E. H. Weber, Volkmann and Wertheim, the elongation of a blood vessel (and 
 most moist tissues) is not proportional to the weight used to extend it, the elongation being rela- 
 tively less with a large weight than with a small one, so that the curve of extension is nearly [or, 
 at least, bears a certain relation to] a hyperbola. 
 
 According to Wundt, we have not only to consider the extension produced aVfirsthy the weight, 
 but also the subsequent " elastic after-effect," which occurs gradually. The elongation which 
 takes place during the last few moments occurs so slowly and so gradually that it is well to observe 
 the effect by means of a magnifying lens. Variations from the general law occur to this extent, 
 that if a certain weight is exceeded, less extension, and, it may be, permanent elongation of the 
 artery not unfrequently occur. K. Bardeleben found, especially in veins elongated to 40 or 50 per 
 cent, of their original length, that when the weight employed increased by an equal amount each 
 time, the elongation was proportional to the square root of the weight. This is apart from any 
 elastic after-effect. Veins may be extended to at least 50 per cent, of their length without passing 
 the limit of their elasticity. 
 
 [Roy has made careful experiments upon the elastic properties of the arterial wall. A portion 
 of an artery, so that it could be distended by any desired internal pressure, was enclosed in a small 
 vessel containing olive oil. The small vessel with oil was arranged in the same way as in Fig. 53 
 for the heart. The variations of the contents were recorded by means of a lever writing on a revolv- 
 ing cylinder. The aorta and other large arteries were found to be most elastic and most disten- 
 sible at pressures corresponding more or less exactly to their normal blood pressure, while in veins 
 the relation between internal pressure and the cubic capacity is very different. In them the maxi- 
 mum of distensibility occurs with pressures immediately above zero. Speaking generally, the cubic 
 capacity of an artery is greatly increased by raising the intra-arterial tension, say from zero to about 
 the normal internal pressure which the artery sustains during life. Thus in the rabbit the capacity 
 of the aorta was quadrupled by raising the intra-arterial pressure from zero to 200 mm. Hg, while 
 that of the carotid was more than six times greater at that pressure than it was in the undistended 
 condition. The pulmonary artery is distinguished by its excessive elastic distensibility. Its capa- 
 city (rabbit) was increased more than twelve times on raising the internal pressure from zero to 
 about 36 mm. Hg. Veins, on the other hand, are distinguished by the relatively small increase in 
 thtir cubic capacity produced by greatly raising the internal pressure, so that the enormous changes 
 in the capacity of the veins during life are due less to differences in the pressure than to the great 
 differences in the quantity of blood which they contain {Roy).] 
 
 Pathological. — Interference with the nutrition of an artery alters its elasticity [and that in cases 
 where no structural changes can be found.] Marasmus preceding death causes the arteries to 
 become wider than normal {Roy). Age also influences their elasticity — in some old people they 
 become atheromatous and even calcified. [The ratio of expansion of strips of the aortic wall to 
 the weights employed to stretch them, remains much the same from childhood up to a certain age 
 [Roy).-\ 
 
 Cohesion. — Blood vessels are endowed with a very large amount of cohesion, 
 in virtue of which they are able to resist even considerable internal pressure with- 
 out giving way. The carotid of a sheep is ruptured only when fourteen times the 
 usual pressure it is called upon to bear is put upon it (Volkmann). A greater 
 pressure is required to rupture a vein than an artery with the same thickness of its 
 wall. The carotid of a dog resists 50 times the blood pressure, the jugular vein 
 about the half of this (Grehant and Quinquand). 
 
 Pathological. — The cohesion of the arteries is diminished, especially in old age. 
 
 66. THE PULSE— HISTORICAL.— Although the movement of the pulse in the super- 
 ficially placed arteries was known to the ancients, still the pulse, as it was affected by disease, was 
 more studied by the older physicians than the normal pulse. Hippocrates (460 to 337 B. c.) speaks 
 of the former as a<poyiJ.ui; y while Herophilus (300 B. c.) contrasted the normal pulse (naXfi6?) 
 with the pulse of disease (apuy/j.6^). He lays special stress upon the relative time occupied by 
 the dilatation and contraction of the arterial tube, and compares these phenomena with the notes of 
 music. He established the fact that the rhythm of the pulse varies in the newly-born, in the adult, 
 and in the aged. Further, he distinguished the size, fullness, quickness and frequency of the pulse. 
 Erasistratus ^f 280 B. c), a contemporary of Herophilus, made correct observations on the pulse 
 
INSTRUMENTS FOR INVESTIGATING THE PULSE. 
 
 117 
 
 wave. He points out that the pulse occurs sooner in arteries near the heart than in those placed 
 further away from it, because the pulse proceeding from the heart passes toward the periphery. 
 Erasistratus placed a cannula in the course of an artery, and he found that the pulse could still be 
 felt on the distal side of this point. Achigenes gave the time dicrotic pulse to a condition which he 
 had observed in febrile states. Galen (131 to 202 A. D.) gave more exact details as to the relations 
 of the dilatation and contraction of the arteries during the movement of the pulse, and supplied 
 much information on the pulse rhythm, and the influence of temperament, age, sex, period of the 
 year, climate, sleep and waking, cold and warm baths, on its rate and other qualities. Cusanus 
 (1565) was the first person to count the pulse beats with the aid of a watch. 
 
 67. INSTRUMENTS FOR INVESTIGATING THE PULSE.— 
 
 [The characters of the pulse may be investigated by: — 
 
 1. The eye (inspection.') 
 
 2. The finger (palpation.) 
 
 3. Instruments.] 
 
 [Two or three fingers are placed over the course of the radial artery, and the 
 various phenomena in connection with the pulse are noted. It takes much prac- 
 
 Fig. 6d. 
 
 Fig. 65 
 
 Poiseuille's pulse measurer, a, a, exposed artery; K, K, the box consisting of 
 two pieces ; <5, vertical tube, with scale attached. 
 
 Sphygmometer of Heris- 
 son and Chelius. 
 
 tice for the physician to acquire the tactus eruditus, and, notwithstanding the 
 value of instruments, every physician should make a careful study of the pulse 
 beat with his finger.] 
 
 The individual phases of the movement of the pulse could only be accurately 
 investigated by the application of instruments to the arteries. 
 
 (1) Poiseuille's Box Pulse Measurer (1829). — An artery (Fig. 63, a, a) is exposed and 
 placed in an oblong box (K, K) filled with an indifferent fluid. A vertical tube, with a scale 
 attached, communicates with the interior of the box. The column of fluid undergoes a variation 
 with every pulse beat. 
 
 (2) Herisson's Tubular Sphygmometer consists of a glass tube whose lower end is covered 
 with an elastic membrane (Fig. 64). The tube is partly filled with Hg. The membrane is placed 
 over the position of a pulsating artery, so that its beat causes a movement in the Hg. Chelius used 
 a similar instrument, and he succeeded with this instrument in showing the existence of the double 
 beat (dicrotism) in the normal pulse (1850). 
 
 (3) Vierordt's Sphygmograph (1855). — In this, one of the earliest sphygmographs, Vierordt 
 departed from the principle of a fluctuating fluid column, and adopted the principle of the lever. 
 
118 
 
 MAREY S SPHYGMOGRAPH. 
 
 Upon the artery rested a small pad, which moved a complicated system of levers. At first he used 
 a straw 6 inches long, which rested on the artery. The point of one of the levers inscribed its 
 movements upon a revolving cylinder. This instrument was soon discarded. 
 
 (4) Marey's Sphygmograph consists of a combination of a lever with an elastic spring. It 
 consists of an elastic spring (Fig. 65, A) fixed at one end, n, free at the other end, and provided 
 with an ivory pad,jj/, which is pressed by the spring upon the radial artery. On the upper surface 
 
 Fig. 65. 
 
 ( # # s 4 # 
 
 Scheme of Marey's sphygmograph. A, spring with ivory pad, _y, which rests on the artery; e, weak spring pressing 
 k into t\ v, writing lever; P, piece of smoked glass or paper moved by clockwork, U ; H, screw to limit excur- 
 sion of A : S, arrangement for fixing the instrument to the arm of the patient. 
 
 Fig. 66. 
 
 Marey's improved sphygmograph, as used when a tracing is taken. A, steel spring ; B, first lever ; C, writing lever ; 
 C, its free writing end ; D, screw for bringing B in contact with C ; G, slide with smoked paper : H , clockwork ; 
 L, screw for increasing the pressure ; M, dial indicating the amount of pressure ; K, K, straps for fixing the in- 
 strument to the arm, and the arm to the double-inclined plane or support (Byrom Branvwell) 
 
 Fig. 67. 
 
 Fig. 68. 
 
 [Fig. 67. — Scheme showing the essential part of the instrument when in working order, i. e., the turned up knife 
 edge, B", of the short lever in contact with the writing lever, C. Every movement of the steel spring at A", i. e , 
 the artery, will in this position be communicated to the writing lever.] 
 
 [Fig. 68.— Scheme showing the essential parts of the instrument after increase of the pressure. The knife edge, B", 
 is no longer in contact with the writing lever, and the movements of the steel spring, A", ?'. e., the artery, are no 
 longer communicated to it. In order to put the instrument into working order, the knife edge, B", must be raised 
 to the position indicated by the dotted lines. This is effected by means of the screw, D (Byrom Bramwelt).] 
 
 of the pad there is a vertically- placed fine-toothed rod, k, which is pressed upon by a weak spring, 
 e, so that its teeth dovetail with similar teeth in the small wheel, t, from whose axis there projects 
 a long, light, wooden lever, 7/, running nearly parallel with the elastic spring. This lever has a fine 
 style at its free end, s, which writes upon a smoked plate, P, moved by clockwork, U, in front of 
 the style. Marey's instrument, as improved by Mahomed and others, has been very largely used. 
 [Its more complete form, as in Fig. 66, where it is shown applied to the arm, consists of — (1) a 
 
DUDGEONS SPHYGMOGRAPH. 
 
 119 
 
 steel spring, A, which is provided with a pad resting on the artery, and moves with each movement 
 of the artery ; (2) the lever, C. which records the movement of the artery and spring in a magnified 
 form on the smoked paper, G ; (3) an arrangement, L, whereby the exact pressure exerted upon 
 the artery is indicated on the dial, M {Mahomed) ; (4) the clockwork, H, which moves the smoked 
 
 Fig. 69. 
 
 Dudgeun's sphygmograph. 
 
 Fig. 70. 
 
 Mode of applying Dudgeon's sphygmograph. 
 
 paper, G, at a uniform rate; ($) a framework, to which the various parts of the instrument are 
 attached, and by means of which the instrument is fastened to the arm by straps, K, K (Byrom 
 Bramwell)."] 
 
 [Application. — In applying the sphygmograph, cause the patient to seat himself beside a low 
 
120 
 
 BRONDGEEST S PAN SPHYGMOGRAPH. 
 
 Fig. 71. table, and place his arm on the double-in- 
 
 clined plane (Fig. 66). In the newer foim 
 of instrument, the lid of the box is so arranged 
 as to unfold to make this support. The fingers 
 ought to be semi-flexed. Mark the position 
 of the radial artery with ink. See that the 
 clockwork is wound up, and apply the ivory 
 pad exactly over the radial artery where it 
 lies upon the radius, fixing it to the arm by 
 the non-elastic straps K, K (Fig. 66). Fix 
 the slide holding the smoked paper in posi- 
 tion. The best japer to use is that with 
 a very smooth surface (albuminized or 
 enameled card), smoked over the flame of 
 a turpentine lamp or over a piece of burning camphor. The writing style is- so arranged as to 
 write upon the smoked paper with the least possible friction. The most important part of the 
 process is to regulate the pressure exerted upon the artery by means of the milled head, L. This 
 must be determined for each j.ulse, but the rule is to graduate the pressure until the greatest 
 
 Sphygmogram — pressure 2 ounces. 
 
 Scheme of Brondgeest's sphygmograph, on the principle of Upham and Marey's tambours. S , S', receiving and 
 recording (S, S') tambours with writing levers, Z and Z' ; K, K', conducting tubes ; p, over heart, p 1 over a 
 distant artery. Ihis illustration also shows the principles of Marey's cardiograph. 
 
 amplitude of movement of the lever is obtained. Set the clockwork going, and a tracing is 
 obtained, which must be " fixed" by dipping it in a rapidly-drying Varnish, e.g., photographic. In 
 every case, scratch on the tracing, with a needle, the name, date, and amount of pressure employed.] 
 
 [(5) Dudgeon's Sphygmograph. — This is a most convenient form of sphygmograph. Fig. 
 69 shows its actual size. 
 
 The instrument after being carefully adjusted upon the radial artery is kept in position by an 
 inelastic strap. The pressure of the spring is regulated, by the eccentric wheel, to any amount from 
 I to 5 ounces. As in other instruments, the tracing paper is moved in front of the writing needle 
 by means of clockwork. The writing levers are so adjusted that the movements of the artery are 
 magnified fifty times.] 
 
 [Fig. 7 1 is a sphygmogram taken with this instrument from a healthy individual. It represents a 
 perfect tracing; a, the vertical upward, systolic or percussion wave; b, apex; c, on the descent; d, 
 first tidal or predicrotic wave; e, aortic notch; f, dicrotic wave (Dudgeon).] 
 
 (6) Marey's Tambours are also employed for registering the movements of the pulse. They 
 are used in the same way as the pansphygmograph of Brondgeest. Fig. 72 shows their arrange- 
 ment. Two pairs of metallic cups (S, S and S', S", Upham's capsules) are pierced in the middle 
 by thin metal tubes, whose free ends are connected with caoutchouc tubes, K and K'. All the 
 four metallic vessels are covered with an elastic membrane. On S and S' are fixed two knob-like 
 
LANDOIS ANGIOGRAPH. 
 
 121 
 
 pads, p and /', which are applied to the pulsating arteries, and the metal arcs, B and B', retain 
 them in position. On the other tambours are arranged the writing levers, Z and Z'. Pressure on 
 the one tambour necessarily compresses the air and makes the other, with which it is connected, 
 expand, so as to move the writing lever. This arrangement does not give absolutely exact results ; 
 still, it is very easily used and is convenient. In Fig. 72 a double arrangement is shown, whereby 
 one instrument, B, may be placed over the heart, and the other, B', on a distinct artery. 
 
 Landois' Angiograph. — To a basal plate, G, G, are fixed two uptight supports,/, which carry 
 between them at their upper part the movable lever, d, r, carrying a rod bearing a pad, e, directed 
 downward, which rests on the pulse. The short arm carries a counterpoise, d, so as exactly to bal- 
 ance the long arm. The long arm has fixed to it at r a vertical rod provided with teeth, h, which 
 is pressed against a toothed wheel firmly fixed on the axis of the very light writing lever, e f, which 
 is supported between two uprights, q, fixed to the opposite end of the basal plate, G, G. The writ- 
 ing lever is equilibrated by means of a light weight. The writing needle, k, is fixed by a joint to e, 
 and it writes on the plate, /. The first-mentioned lever, d, r, carries a shallow cup, Q, just above 
 
 Fig. 73. 
 
 Scheme of Landois' angiograph. 
 
 the pad, into which weights may be put to press on the pulse. In this instrument the weight can 
 be measured and varied ; the writing lever moves vertically and not in a curve, as in Marey's appa- 
 ratus, which greatly facilitates the measuring of the curves (Fig. 73). 
 
 Other sphygmographs are used, both in this country and abroad, including that of Sommerbrodt, 
 which is a complicated form of Marey's sphygmograph, 
 
 and those of Pond and Mach. In choosing a sphyg- Fig. 74. 
 
 mograph, that instrument is to be preferred which 
 yields a curve corresponding most closely with the 
 variations of the pressure within the artery, in which 
 the resistance of the instrument is small, which gives 
 the largest curve, and in which the part in contact 
 with the artery is not greatly displaced from its position 
 of equilibrium (Mach). 
 
 Characters of a Pulse Curve. — In 
 
 every pulse curve — Sphygmogram or Arte- 
 riogram — we can distinguish the ascending 
 part (ascent) of the curve, the apex, and the 
 descending part (descent). Secondary eleva- 
 tions scarcely ever occur in the ascent, which 
 is usually represented by a straight line, 
 while they occur constantly in the descent. 
 Such elevations occurring in the descent are 
 called catacrotic, and those in the ascent, anacrotic (Landois). When the 
 recoil elevation or dicrotic wave occurs in a well-marked form in the descent, the 
 pulse is said to be dicrotic, and when it occurs twice tricrotic. 
 
 Measuring Pulse Curves. — If the smoked surface on which the tracing is inscribed is moved 
 at a uniform rate by means of the clockwork, then the height and length of the curve are measured 
 
 Pulse curve of the radial artery of a healthy stu- 
 dent, obtained by Landois' angiograph writing 
 upon a plate attached to a vibrating tuning 
 fork. Each double vibration corresponds to 
 0.01613 sec. 
 
122 
 
 LANDOIS GAS SPHYGMOSCOPE. 
 
 by means of an ordinary rule. If we know the rate at which the paper was moved, then it is easy 
 to calculate the duration of any event in the curve. For exact observation a low-power microscope 
 with a micrometer in the eye-piece should be used. 
 
 Landois' gas sphygmoscope. 
 
 , skin over artery ; &. metal plate ; p, g, gas ; 
 gas burner, y, to b. 
 
 ; q, caoutchouc tube attaching glass 
 
 Fig, 
 
 For the method of smoking the paper and fixing the tracings see p. 120. 
 
 It is very convenient to write the curve upon a plate of glass fixed to a tuning-fork kept in vibra- 
 tion. Every part of the curve shows little elevations (whose rate of vibration is known beforehand). 
 
 All that is required is to count the number of vibrations 
 in order to ascertain the duration of any part of the curve. 
 (Fig. 74). 
 
 Landois' Gas Sphygmoscope. — A superficially placed 
 
 artery communicates its movements to the overlying skin, and 
 
 also to any freely movable body in contact with the skin. In 
 
 .„ this instrument (Fig. 75) a thin layer of air over the pulsating 
 
 J M artery, a, is enclosed by means of a thin piece of metal, which 
 
 ?B is so adjusted that its concave side forms a tunnel of air over 
 
 the artery. The narrow space between the metallic wall, 6, 
 and the skin, a, is filled with ordinary gas, one end of the 
 metal shield being connected, by means of a tube, g, with the 
 gas supply, while to the other end there is attached, by means 
 of a short piece of caoutchouc, x, q, a bent glass tube, t, with 
 a very small aperture, which acts as a gas burner. The gas is 
 allowed to flow through the apparatus at a low pressure, and 
 is so regulated that the flame, v, is only a few millimetres in 
 height. The flame rises synchronously with every pulse beat, 
 and the dicrotic beat in the normal pulse is quite observable. 
 
 Czermak photographed a beam of light set in motion by the 
 movements of the pulse. 
 
 Hsemautography. — Expose a large artery of an animal, 
 and divide it so that the stream of blood issuing from it strikes 
 against a piece of paper drawn in front of the blood stream. 
 A curve (Fig. 76) is obtained which corresponds very closely 
 with the pulse tracing obtained from a normal artery. In 
 addition to the primary wave, P, there is a distinct "recoil 
 elevation," or dicrotic wave, R. and slight vibrations, e, e, due 
 to the variations in the elasticity of the arterial wall. The 
 interest which attaches to a curve obtained in this way is, that 
 it shows the movements occur in the blood itself, and are 
 communicated as waves to the arterial wall. By estimating 
 the amount of blood in the various parts of the curve we obtain a knowledge of the amount of blood 
 discharged by the divided artery during the systole and diastole (»', e., the narrowing and dilatation) 
 of the artery — the ratio is 7 : 10. Thus in the unit of time, during arterial dilatation, rather more 
 than twice as much blood flows out as happens during arterial contraction. 
 
 68. THE PULSE TRACING OR SPHYGMOGRAM.— Analysis. 
 
 — A sphygmogram or pulse tracing consists of a series of curves (Fig. 77) each 
 one of which corresponds with one beat of the heart. Each pulse curve consists of — 
 
 1. The line of ascent (a to b in Fig. 77). 
 
 2. The apex (P in Fig. 79, and b in Fig. 77). 
 
 3. The line of descent {b to h). 
 
 The line of ascent, up stroke, or percussion stroke {Mahomed) is nearly verti- 
 cal, and occurrs during the dilatation of the artery produced by the systole of the 
 
 Hxmautographic curve of the posterior 
 tibial artery of a large dog. P, pri- 
 mary pulse wave ; R, dicrotic or recoil 
 wave ; e, f, elevations due to elasticity. 
 
THE PULSE CURVE. 
 
 123 
 
 left ventricle, and occurs when the aortic valves are forced open and the ven- 
 tricular contents are projected into the arterial system. [The ascent is nearly 
 vertical, but in some cases, where the ventricle contracts very suddenly, as occa- 
 sionally happens in aortic regurgitation, it is quite vertical (Fig. 80).] 
 
 The apex or percussion wave {Mahomed) in a normal pulse is pointed. 
 
 The line of descent is gradual, and corresponds to the diminution of diameter 
 or contraction of the artery. It is interrupted by two completely distinct elevations 
 or secondary waves. The more distinct of the two occurs as a well-marked eleva- 
 tion about the middle of the descent (R in Fig. 79 and/in Fig. 77) ; it is called 
 the dicrotic ■wave, or, with reference to its mode of origin, the " recoil wave." 
 
 Fig. 77. 
 
 Sphygmogram of rxdial artery : pressure 2 oz. Each part of the curve between the base ot one up stroke and the 
 base of the next up stroke corresponds to a beat of the heart, so that this figure shows five heart beats and part 
 of a sixth ; a, b— the ascent, b, the apex of the up stroke, and b to h the descent, with an elevation, d, called 
 the first tidal or predicrotic wave, e, an angle or notch, the aortic notch, f, a second elevation, called the dicrotic 
 wave, g, a slight curve, sometimes called the second tidal wave. The descent is continued to h, where the ascent 
 of the next heart beat begins. 
 
 [As the descent corresponds to the time when blood is flowing out of the arte- 
 ries at the periphery into the capillaries, its direction will depend on the rapidity 
 of this outflow. Thus, it will be more rapid in paralysis of the arterioles and very 
 rapid in aortic regurgitation, where, of course, much of the blood flows backward 
 into the left ventricle (Fig. 80). In this case the artery will recoil suddenly from 
 under the finger or pad of the instrument, and this constitutes the " pulse of empty 
 arteries."] 
 
 The dicrotic 'wave, recoil wave [or aortic systolic wave {BramweW)~\ (Fig. 
 77), corresponds to the time following the closure of the aortic valves, and is pre- 
 ceded in the descent by a slight depression, the aortic notch. 
 
 Fig. 78. 
 
 Irregular pulse of mitral regurgitation. 
 
 [The tidal wave, or pre-dicrotic, occurs between the apex and the dicrotic 
 wave (Fig. Jjd). It has also been called the second ventricular systolic wave, as 
 it occurs after the first systolic wave or apex, and during the contraction of the 
 ventricle (BramweW). The tidal wave is best marked in a hard pulse, i. e. , where 
 the blood pressure is high, so that it is usually well marked in cirrhotic disease of 
 the kidney, accompanied by hypertrophy of the left ventricle.] 
 
 [In some cases, e. g., mitral regurgitation, the pre-dicrotic wave may be present in some pulse 
 beats and absent in others (Fig. 78), where the tidal wave is present in the largest pulse and absent 
 in the others, while the base line is uneven. In mitral stenosis, the amount of blood discharged 
 into the left ventricle frequently varies, hence the variations in the characters of the arterial pulse.] 
 
124 
 
 ORIGIN AND CHARACTERS OF THE DICROTIC WAVE. 
 
 There may be other secondary waves in the lower part of the descent. 
 
 [Respiratory or Base Line. — If a line be drawn so as to touch the bases of 
 all the up strokes, we obtain a. straight line, hence called by this name. The base 
 line is altered in disease and during forced respiration (§ 74).] 
 
 Fig. 
 
 vii 
 
 fi ^ ft 
 
 j 
 
 
 3 
 
 
 
 i k 
 
 
 
 fi 
 
 f. 
 
 A 
 
 JnaJ 
 
 J 
 
 w 
 
 
 1 
 
 A 
 \ 
 
 XIV 
 
 XV 
 
 I, II, III, Sphygmograms of carotid artery; IV, axillary; V to IX, radial; X, dicrotic radial pulse; XI, XIT, 
 crural ; XlII, posterior tibial : XIV, XV, pedal. In all the curves P indicates apex ; R, dicrotic wave; e, e, 
 elevations due to elasticity; K, elevation caused by closure of the semilunar valves of the aorta. 
 
 I. Origin and Characters of the Dicrotic Wave. — The dicrotic or 
 recoil wave, which is always present in a normal pulse, is caused thus : During 
 the ventricular systole, a mass of blood is propelled into the already full aorta, 
 whereby a positive wave is rapidly transmitted from the aorta throughout the 
 arterial system, even to the smallest arterioles, in which this primary wave is 
 extinguished. As soon as the semilunar valves are closed, and no more blood 
 flows into the arterial system, the arteries, which were previously distended 
 
CHARACTERS OF THE DICROTIC WAVE. 125 
 
 by the mass of blood suddenly thrown into them, recoil or contract, so that, 
 in virtue of the elasticity (and contractility) of their walls, they exert a counter- 
 pressure upon the column of blood, and thus the blood is forced onward. 
 There is a free passage for it toward the periphery, but toward the centre (heart) 
 it impinges upon the already closed semilunar valves. This develops a new posi- 
 tive wave, which is propagated peripherally through the arteries, where it disap- 
 pears in their finest branches. In those cases where there is sufficient time for the 
 complete development of the pulse curve (as in the short course of the carotids, 
 and in the arteries of the upper arm, but not in those of the lower extremity, on 
 account, of their length), a second reflected wave may be caused in exactly the 
 same way as the first. 
 
 Just as the pulse occurs later in the more peripherally placed ' arteries than in 
 those near the heart, so the secondary wave reflected from the closed aortic valves 
 must appear later in the peripheral arteries. Both kinds of waves — the primary- 
 pulse wave, the secondary, and, eventually, even the tertiary reflected wave — arise 
 in the same place, and take the same course, and the longer the course they have 
 to travel to any part of the arterial system, the later they arrive at their destination. 
 
 The following points regarding the dicrotic wave have been ascertained 
 experimentally : — 
 
 i. The dicrotic wave occurs later in the descending part of the curve the further 
 the artery experimented upon is distant from the heart {Landois, 1863). Compare 
 the curves, Figs. 74, 84, 88. 
 
 The shortest accessible course is that of the carotid, where the dicrotic wave reaches its maximum 
 0.35 to 0.37 sec. after the beginning of the pulse. In the upper extremity the apex of the dicrotic 
 wave is 0.36. to 0.38 to 0.40 sec. after the beginning of the pulse beat. The longest course is that 
 of the arteries of the lower extremity. The apex of the dicrotic wave occurs 0-45 to 0-52 to 0-59 
 sec. after the base of the curve. It varies with the height of the individual. 
 
 2. The dicrotic elevation in the descent is lower (Naumanri), and is less dis- 
 tinct {Landois), the further the artery is situated from the heart. This is just what 
 one would expect, viz., the longer the distance which the wave has to travel, the 
 less distinct it must become. 
 
 3. It is more pronounced in a pulse where the primary pulse wave is short and 
 energetic {Marey, Landois). It is greatest relatively when the systole of the heart 
 is short and energetic. 
 
 4. It is greater the lower the tension or pressure of the blood within the arte- 
 ries {Marey, Landois), [and is best developed in a soft pulse]. In Fig. 79, IX 
 and X were obtained when the tension of the arterial wall was low ; V and VI, 
 medium; and VII with high tension. 
 
 Conditions influencing Arterial Tension. — It is diminished at the beginning of inspira- 
 tion (<! 74), by hemorrhage, stoppage of the heart, heat, an elevated position of parts of the body, 
 amyl nitrite ; it is increased at the beginning of expiration by accelerated action of the heart, stimu- 
 lation of vasomotor nerves, diminished outflow of blood at the periphery, and by inflammatory con- 
 gestion (Knechl) ; further, by certain poisons, as lead ; compression of other large arterial trunks, 
 action of cold and electricity on the small cutaneous vessels, and by impeded outflow of venous 
 blood. When a large arterial trunk is exposed the stimulation 
 
 of the air causes it to contract, resulting in an increased ten- jr IG g Q 
 
 sion within the vessel. In many diseased conditions the arterial 
 tension is greatly increased — \e. g., in Blight's disease, where 
 the kidney is contracted ("granular"), and where the left 
 ventricle is hypertrophied] . 
 
 In all these conditions increased arterial tension is indicated 
 by the dicrotic wave being less high and less distinct, while 
 with diminished arterial tension it is a larger and apparently 
 more independent elevation. Moens has shown that the time 
 between the primary elevation and the dicrotic wave increases 
 with increase in the diameter of the tube, with diminution of 
 its thickness, and when its coefficient of elasticity diminishes. 
 
 [The dicrotic wave is absent or but slightly marked in cases 
 of atheroma and in aortic regurgitation (Fig. 80). In this 
 figure observe also the vertical character of the up stroke.] Aortic regurgitation. 
 
126' DICROTIC PULSE. 
 
 II. Origin and Characteristics of the Elastic Elevations. — Besides 
 the dicrotic wave, a number of small, less-marked elevations occur in the course 
 of the descent in a sphygmogram (Fig. 79, e, e). These elevations are caused 
 by the elastic tube being thrown into vibrations by the rapid energetic pulse 
 wave, just as an elastic membrane vibrates when it is suddenly stretched. The 
 artery also executes vibratory, movements when it passes suddenly from the 
 distended to the relaxed condition. These small elevations in the pulse curve, 
 caused by the elastic vibrations of the arterial wall, are called " elastic eleva- 
 tions " by Landois. 
 
 ( 1) The elastic vibrations increase in number in one and the same artery with 
 the degree of tension of the elastic arterial wall. A very high tension occurs in 
 the cold stage of intermittent fever, in which case these elevations are well marked. 
 ^2) If the tension of the arterial wall be greatly diminished these elevations 
 may disappear, so that, while diminished tension favors the production of the 
 dicrotic wave, it acts in the opposite way with reference to the "elastic eleva- 
 tions." (3) In diseases of the arterial walls affecting their elasticity, these eleva- 
 tions are either greatly diminished or entirely abolished. (4) The further the 
 arteries are distant from the heart, the higher are the elastic elevations. (5) 
 When the mean pressure within the arteries is increased by preventing the outflow 
 of blood from them, the elastic vibrations are higher and nearer the apex of the 
 curve. (6) They vary in number and length in the pulse curves obtained from 
 different arteries of the body. 
 
 Fig. 81. 
 
 Development of the Pulsus dicrotus. — P. caprizans ; P. monocrotus. 
 
 When the arm is held in an upright position, after five minutes the blood vessels empty themselves, 
 and collapse, while the elasticity of the arteries is diminished. 
 
 69. DICROTIC PULSE. — Sometimes during fever, especially when the temperature is high, 
 a dicrotic pulse maybe felt, each pulse beat, as it were, being composed of two beats (Fig. 79, X), 
 one beat being large and the other small, and more like an after beat. Both beats correspond to one 
 beat of the heart. The two beats are quite distinguishable by the touch. The phenomenon is only 
 an exaggerated condition of what occurs in a normal pulse. The sensible second beat is nothing more 
 than the greatly increased dicrotic elevation, which, under ordinary conditions, is not felt by the finger. 
 
 Conditions. — The occurrence of a dicrotic pulse is favored (I) by a short primary pulse wave, as 
 in fevers, where the heart beats rapidly. 
 
 (2) By diminished tension within the arterial system. A short systole and diminished arterial 
 blood pressure are the most favorable conditions for causing a dicrotic pulse. [So that dicrotism is 
 best marked in a soft pulse.] The double beat may be felt only at certain parts of the arterial 
 system, while at other parts only a single beat is felt. A favorite site is the radial artery of one or 
 other side, where conditions favorable to its occurrence appear to exist. This seems to be due to a 
 local diminution of the blood pressure in this area, owing to the paralysis of its vasomotor nerves 
 {Landois). If the tension be increased by compressing other large arterial trunks or the veins of the 
 part, the double beat becomes a simple pulse beat. The dicrotic pulse in fever seems to be due to 
 the increased temperature (39° to 40 C), whereby the artery is more distended, and the heart beat 
 is shorter, and more prompt (Jiiegel). 
 
 (3) It is absolutely necessary that the elasticity of the arterial wall be normal. The dicrotic 
 pulse does not occur in old persons with atheromatous arteries [Landois). 
 
CONDITIONS AFFECTING THE PULSE RATE. 
 
 127 
 
 Monocrotic Pulse. — In Fig. 81, A, B, C, we observe the gradual passage of the normal radial 
 curve, A, into the dicrotic beat, B and C, where the dicrotic wave, r, appears as an independent 
 elevation. If the frequency of the pulse increases more and more in fever, the next following pulse 
 beat may occur in the ascending part of the dicrotic wave, D, E, F, and it may even occur close to 
 the apex, G (P. caprizans). If the next following beat occurs in the depression, i, between the 
 primary elevation, p, and the dicrotic elevation, r, the latter entirely disappears, and the curve, H, 
 assumes what Landois calls the " monocrotic " type. 
 
 [Degrees of Dicrotism. — -When the aortic notch reaches the respiratory or base line, the tidal 
 wave having disappeared, the pulse is said to be fully dicrotic. 
 
 When the aortic notch falls below the base line, i. <?., below where the up stroke begins, the pulse 
 is said to be hyperdicrotic (Fig. 82). This form occurs during high fever (104 F.), and is usually 
 a grave sign, indicating exhaustion and the need for stimulants.] 
 
 70. CHARACTERS OF THE PULSE.— 1. Pulsus Frequens and Rarus.— Frequency. 
 
 — According as a greater or less number of beats occur in a given time, e. g., per minute, the pulse 
 is said to be frequent or rare. The normal rate, in man = 71 per minute, and somewhat more in 
 the female ; in fever it may exceed 120 (250 have been counted by Bowles), while in other diseases 
 it may fall to 40, and even 10 to 15 (de Haen), 17 (Hartog), and 14 (Cornil); but such cases are 
 rare, and are probably due to an affection of the cardiac nerves (g 41). The frequency of the pulse 
 is usually increased when the respirations are deeper, but not more numerous, i. e., rapid shallow 
 respirations do not affect the frequency of the pulse, but deep respirations do {Knoll). 
 
 2. Pulsus Celer and Tardus. — Celerity or Rapidity. — If the pulse wave is developed so 
 that the distention of the artery slowly reaches its height, and the relaxation also takes place gradu- . 
 ally, we have the p. tardus or slow pulse, the opposite condition gives rise to the p. celer or quick 
 pulse. The rapidity of the pulse is increased by quick action of the heart, power of expansion of 
 the arterial walls, easy efflux of blood owing to the dilatation of the small arteries, and by nearness 
 to the heart. [The quickness has reference to a single pulse beat, the frequency to a number of 
 beats.] In a quick pulse, the curve is high and the angle at the apex is acute ; while in a slow 
 pulse the ascent is low and the angle at the apex is large. 
 
 Fig. 82. 
 
 \Ay\AAAAMM/ 
 
 Hyperdicrotic pulse. 
 
 3. Conditions affecting the Pulse Rate. — Frequency in Health. — In man the normal pulse 
 rate = 71 to 72 beats per minute; in the female about 80. In some individuals the pulse rate may 
 be higher (90 to 100), in others lower (50), and such a fact must be borne in mind. The following 
 conditions influence it : — 
 (a) Age. 
 
 Beats per 
 Minute. 
 
 Newly born 130 to 140 
 
 1 year 120 to 130 
 
 2 years 105 
 
 3 " 100 
 
 4 " 97 
 
 5 " 94 to 90 
 
 10 " about 90 
 
 Beats per 
 Minute. 
 10 to 15 years 78 
 
 15 to 20 
 
 20 to 25 
 
 25 to 50 
 
 60 
 
 80 
 
 80 to 90 
 
 . . 7° 
 . . 7° 
 . 70 
 , . . 74 
 . . 79 
 over 80 
 
 (b) The length of the body has a certain relation to the frequency of the pulse. The follow- 
 ing results have been obtained by Czarnecki from the formulae of Volkmann and Rameaux : — 
 
 Length of Body 
 
 in 10 cm. 
 
 80 to 90. . 
 
 90 to IOO. . 
 
 100 to IIO. . 
 
 110 to 120. . 
 
 Pulse 
 
 Calculated. Observed. 
 
 . . 9° 
 
 . 86 
 
 . . 81 
 
 . ■ 78 
 
 120 to 130 75 
 
 130 to 140 72 
 
 103 
 91 
 87 
 84 
 78 
 76 
 
 Length of Body Pulse 
 
 in 10 cm. Calculated. Observed. 
 
 140 to 150 69 74 
 
 150 to 160 67 68 
 
 160 to 17,0 65 65 
 
 170 to 180 63 64 
 
 above 180 60 60 
 
 (c) The pulse rate is increased by muscular activity, by every increase of the arterial blood 
 pressure, by taking of food, increased temperature, painful sensations, by psychical disturbances, 
 and \in extreme debility~\. Increased heat, fever, or pyrexia increases the frequency, and, as a rule, 
 
128 
 
 VARIATIONS IN THE PULSE RHYTHM. 
 
 the increase varies with the height of the temperature. [Dr. Aitken states that an increase of the 
 temperature of i° F. above 98° F. corresponds with an increase of ten pulse beats per minute; 
 thus : — 
 
 Temp. 
 98° 
 
 99° 
 100 
 
 IOI° 
 102° 
 
 Pulse Rate. 
 
 Temp. F 
 
 . 60 
 
 103° 
 
 . • 7° 
 
 I O4 
 
 . 80 
 
 105° 
 
 80 
 
 106 
 
 . . IOO 
 
 
 Pulse Rate. 
 
 1 10 
 . 120 
 . 130 
 . 140 
 
 / 
 
 This is merely an approximate estimate.] It is more frequent when a person is standing than when 
 he lies down. Music accelerates the pulse and increases the blood pressure in dogs and men 
 {Dogiel). Exposure to increased barometric pressure diminishes the frequency. 
 
 The variation of the pulse rate during the day— 3 to 6 a.m. = 61 beats; 8 to.n^ a.m. = 
 74. It then falls toward 2 P.M. ; toward 3 (at dinner time) another increase takes place and goes 
 on until 6 to 8 p.m. = 70; and it falls until midnight = 54. It then rises again toward * a.m., 
 when it soon falls again, and afterward rises, as before, toward 3 to 6 a.m. 
 
 [Pulse Rate in Animals. 
 Per Min. 
 -^Elephant 25-28 
 
 ^Camel . 
 
 Giraffe . 
 "Horse . 
 -Ox. . 
 
 Tapir . 
 •Ass , . 
 •Pig . . 
 
 Lion, . 
 
 28-32 
 66, 
 
 36-40- 'Goat 
 
 45-50 
 
 44 
 46-50 
 70-80 
 
 Lioness . 
 Tiger. . 
 'Sheep . 
 
 Leopard . . . 
 Wolf (female) , 
 Hyaena . 
 ■Dog ... 
 
 40^ Cat. 
 
 Per Min. 
 
 68 
 
 74 
 
 70-80 
 
 70-80 
 
 60 
 
 96 
 
 55 
 
 90-100 
 
 120-140 
 
 Rabbit. 
 Mouse . 
 Goose . 
 Pigeon 
 J^flen . 
 Snake . 
 Carp . 
 ■Frog . 
 Salamander . 
 
 Per Min. 
 . I2O-I50 
 
 '5° 
 no 
 
 136 
 
 140 
 
 24 
 
 20 
 
 80 
 
 77 
 {Colin).] 
 
 Fig. 83. 
 
 Pulsus alternans. 
 
 4. Variations in the Pulse Rhythm. — On applying the fingers to the normal pulse, we feel beat 
 after beat occurring at apparently equal intervals. Sometimes in a normal series a beat is omitted 
 = pulsus intermittens, or intermittent pulse. [In feeling an intermittent pulse, we imagine 
 or have the impression that a beat is omitted. This may be due to a reflex arrest of the ventricular 
 contraction, caused by digestive derangement, in which case it has no great significance ; but if it 
 be due to failure of the ventricular action, intermittent pulse is a serious symptom, being frequently 
 present when the muscular walls are degenerated.] At other times the beats become smaller and 
 smaller, and after a certain time begin as large as before = p. myurus. When an extra beat is 
 ' intercalated in a normal series = p. intercurrens. The regular alternation of a high and a low 
 beat = p. alternans ( Traube) (Fig. 83). In the p. bigeminus of Traube the beats occur in 
 pairs, so that there is a longer pause after every two beats. Traube found that he could produce 
 this form of pulse in curarized dogs by stopping the artificial respiration for a long time. The p. 
 trigeminus and quadngeminus occur in the same way, but the irregularities occur after every 
 third and fourth beat. Knoll found that in animals such irregularities of the pulse were apt 
 to occur, as well as great irregularity in the rhythm generally, when there is great resistance 
 to the circulation, and consequently the heart has great demands upon its energy. The same 
 occurs in man, when an improper relation exists between the force of the cardiac muscle 
 and the work it has to do {Riegel). Complete irregularity of the heart's action is called 
 arhythmia cordis, 
 
 71. VARIATIONS IN THE STRENGTH, TENSION AND VOLUME OF THE 
 PULSE.— Compressibility. — The relative strength or compressibility of the pulse (p. fortis. 
 and debilis), 1, {., whether the pulse is strong or weak, is estimated by the weight which the pulse is 
 
THE PULSE CURVES OF VARIOUS ARTERIES. 129 
 
 able to raise. A sphygmograph, provided with an index indicating the amount of pressure exerted 
 upon the spring pressing upon the artery, may be used (Fig. 66). In this case, as soon as the 
 pressure exerted upon the artery overcomes the pulse beat, the lever ceases to move. The weight 
 employed indicates the strength of the pulse. [The finger may be, and generally is, used. The 
 finger is pressed upon the artery until the pulse beat in the artery beyond the point of pressure is 
 obliterated. In health it requires a pressure of several ounces to do this. Handfield Jones uses a 
 sphygmometer for this purpose. It is constructed like a cylindrical letter weight, and the pressure 
 is exerted by means of a spiral spring which has been carefully graduated.] The pulse is hard or 
 soft when the artery, according to the mean blood pressure, gives a feeling of greater or less resist- 
 ance to the finger, and this quite independent of the energy of the individual pulse beats (p. durus 
 and mollis). 
 
 In estimating the tension of the artery and the pulse, i. e., whether it is hard or soft, it is import- 
 ant to observe whether the artery has this quality only during the pulse wave, i. e., if it is hard 
 during diastole, or whether it is hard or soft during the period of rest of the arterial wall. All 
 arteries are harder and less compressible during the pulse beat than during the period of rest, but 
 an artery which is very hard during the pulse beat may be hard also during the pause between the 
 pulse beats, or it may be very soft, as in insufficiency of the aortic valves. In this case, after the sys- 
 tole of the left ventricle, owing to the incompetency of the aortic semilunar valves, a large amount 
 of blood flows back into the ventricle, so that the arteries are thereby suddenly rendered partially 
 empty. [The sudden collapse of the artery gives rise to the characteristic " pulse of unfilled 
 arteries." Fig. 80.] 
 
 Under similar conditions, the volume of the pulse is obvious from the size of the sphygmogram, 
 so that we speak of a large and a small pulse (p. magnus and parvus). Sometimes the pulse is so 
 thready and of such diminished volume that it can scarcely be felt. A large pulse occurs in disease 
 when, owing to hypertrophy of the left ventricle, a large amount of blood is forced into the aorta. 
 A small pulse occurs under the opposite condition, when a small amount of blood is forced into 
 the aorta, either from a diminution of the total amount of the blood, or from the aortic orifice being 
 narrowed [aortic stenosis], or from disease of the mitral valve; again, where the ventricle contracts 
 feebly, the pulse becomes small and thready. 
 
 Compare the two Radials. Sometimes the pulse differs on the two sides, or it may be absent on 
 one side. [The pulse wave in the two radials is often different when an aneurism is present on one 
 side.] 
 
 Angiometer. — Waldenburg constructed a " pulse clock" to register the tension, the diameter of 
 the artery, and the volume of the pulse upon a dial. It does not give a graphic tracing, the results 
 being marked by the position of an indicator. 
 
 72. THE PULSE CURVES OF VARIOUS ARTERIES.— 1. Carotid (Fig. 79, I, II, 
 III; Fig. 88, C and C t ). — The ascending part is very steep — the apex of the curve (Fig. 79, P) is 
 sharp and high. Below the apex there is a small notch — the " Aortic Notch " (Fig. 79, K) — 
 which depends on a positive wave formed in the root of the aorta, owing to the closure of the aortic 
 valves, and propagated with almost wholly undiminished energy into the carotid artery. Quite 
 close to this notch, if the curve be obtained with minimal friction, the first elastic vibration occurs 
 (Fig. 79, II, e). Above the middle of the descending part of the curve is the dicrotic elevation, R, 
 produced by the reflection of a positive wave from the already closed semilunar valves. The dicrotic 
 wave is relatively small, on account of the high tension in the carotid artery. After this the curve 
 falls rapidly, but in its lowest third two small elevations may be seen. Of these the former is due 
 to elastic vibration. The latter represents a second dicrotic wave (Fig. 79, III, R) (Landois, 
 Moens). Here there is a true tricrolism, which is more easily obtained from the carotid on account 
 of the shortness of the arterial channel. 
 
 2. Axillary Artery (Fig. 79, IV). — In this curve the ascent is very steep, while in the descent 
 near the apex there is a small (aortic) elevation, K, caused by a positive wave, produced by the 
 closure of the aortic valves. Below the middle there is a tolerably high dicrotic elevation, R, 
 higher than in the carotid curve ; because in the axillary artery the arterial tension is less, and per- 
 mits a greater development of the dicrotic wave. Further on, two or three small elastic vibrations 
 occur, e, e. 
 
 3. Radial Artery (Fig. 74; Fig. 79, V to X ; Fig, 88, R and R^.— The line of ascent (Fig. 
 79) is tolerably high and sudden — somewhat in the form of a long/. The apex, P, is well marked. 
 Below this, if the tension be high, two elastic vibrations may occur (V, e, e), but if it be low only 
 one (VI to IX, e). About the middle of the curve is the well-marked dicrotic elevation, R. 
 
 This wave is least pronounced in a. small, hard pulse, and when the artery is much distended 
 (Fig. 79, VII, R^ ; it is larger when the tension is low (Fig. 79, IX, R), and is greatest of all 
 when the pulse is dicrotic (X, R). Two or three small elastic.elevations occur in the lowest part of 
 the curve. 
 
 4. Femoral Artery (Fig. 79, XI, XII). — The ascent is steep and high — the apex of the curve is 
 not unfrequently broad, and in it the closure of the aortic valves (K) is indicated. The curve falls 
 rapidly toward its lowest third. The dicrotic elevation, R, occurs late after the beginning of the 
 curve, and there are also small elastic elevations (<?, e) . 
 
 9 
 
130 
 
 ANACROTISM. 
 
 Curve 01 posterior tibial. Written 
 by the angiograph upon a 
 vibrating plate attached to a 
 tuning fork. 
 
 I vibration is = 
 0.01613 sec. 
 
 Fig. 84. 5. Pedal Artery (Fig. 79, XIV, XV), and Posterior Tibial 
 
 (Fig. 84 and Fig. 79, XIII). — In pulse curves obtained from 
 these arteries, there are well-marked indications that the appa- 
 ratus (heart) producing the waves is placed at a considerable 
 distance. The ascent is oblique and low — the dicrotic elevation 
 occurs late. Two elastic vibrations ( Fig. 79, XIV, e, e) occur in 
 the descent, but they are very close to the apex, while the elastic 
 vibrations at the lower part of the curve are feebly marked. 
 Fig. 84 is from the posterior tibial. When measured, it gives 
 the following result : 
 
 ' I to 2 9.5 ' 
 
 I to 3 20 
 
 I to 4 30.5 
 
 I to 6 61 J 
 
 73. ANACROTISM. — As a general rule, the line of ascent of a pulse curve has the form of 
 anyj and is nearly vertical. The arterial walls are thrown into elastic vibration by the pulse beat, 
 and the number of vibrations depends greatly upon the tension of the arterial walls. 
 
 The distention of the artery, or what is the same thing, the ascent of the sphygmogram, usually 
 occurs so rapidly that it is equal to one elastic vibration. The elongated /-shape of the ascent is 
 fundamentally just a prolonged elastic vibration. When the number of vibrations causing the 
 elastic vibration, is small, and when the line of ascent is prolonged, two elevations occasionally occur 
 in the line of ascent. Such a condition may occur normally (Fig. 79, VIII at I and 2; X at 1 and 
 2). When a series of closely placed elastic vibrations occur in the upper part of the line of ascent, 
 so that the apex appears dentate and forms an angle with the line of ascent, then the condition 
 becomes one of Anacrotism (Fig. 85, a, a), which, when it becomes so marked, may be charac- 
 terized as pathological (Landois). Anacrotism'of the pulse occurs when the time of the influx of 
 the blood is longer than the time occupied by an elastic vibration. Hence it takes place : — 
 
 J^J 
 
 Anacrotic radial curves, a, a, the anacrotic parts. 
 
 (1) In dilatation and hypertrophy of the left ventricle, e.g., Fig. 85, A, a tracing from the 
 radial artery of a man suffering from contracted kidney. The large volume of blood expelled with 
 each systole requires a long time to dilate the tense arteries. 
 
 (2) When the extensibility of the arterial wall is diminished, even the normal amount of 
 blood expelled from the heart at every systole requires a long time to dilate the artery. This occurs 
 in old people, where the arteries tend to become rigid, e.g., in atheroma. Cold also stimulates the 
 arteries, so that they become less extensile. Within one hour after a tepid bath, the pulse assumes 
 the anacrotic form (Fig. 85, D) (G. v. Liebig). 
 
 (3) When the blood stagnates in consequence of great diminution in the velocity of the blood 
 stream, as occurs in paralyzed limbs, the volume of blood propelled into the artery at every systole 
 no longer produces the normal distention of the arterial coats, and anacrotic notches occur (Fig. 
 85, B). 
 
 (4) After ligature of an artery, when blood slowly reaches the peripheral part of the vessel 
 through a relatively small collateral circulation, it also occurs. If the brachial artery be compressed 
 so that blood slowly reaches the radial, the radial pulse may become anacrotic. It often occurs in 
 stenosis of the aorta, as the blood has difficulty in getting into the aorta (Fig. 85, C). 
 
 Recurrent Pulse. — If the radial artery be compressed at the wrist, the pulse 
 beat reappears on the distal side of the point of pressure through the arteries of 
 the palm of the hand {Janaud, Neiderf). The curve is anacrotic, and the 
 dicrotic wave is diminished, while the elastic elevations are increased. 
 
 (5 ) A special form of anacrotism occurs in cases of well-marked insufficiency of the aortic 
 valves. Practically, in these cases, the aorta remains permanently open. The contraction of the , 
 left auricle causes in the blood a wave motion, which is at once propagated through the open mouth 
 of the aorta into the large blood vessels. This wave is followed by the wave caused by the con- 
 
INFLUENCE OF RESPIRATORY MOVEMENTS ON PULSE CURVE. 131 
 
 traction of the hypertrophied left ventricle ; but, of course, the former wave is not so large as the 
 latter. In insufficiency of the aortic valves, the auricular wave occurs before the ventricular wave 
 in the ascending part of the curve. The auricular is well marked only in the large vessels, for it 
 becomes lost in the peripheral vessels. Fig. 86, I, was obtained from the carotid of a man suffering 
 from well-marked insufficiency of the aortic valves, with considerable hypertrophy of the left ventricle 
 and left auricle. The ascent is steep, caused by the force of the contracting heart. In the apex of 
 the curve are two projections ; A is the anacrotic auricular wave, and V is the ventricular wave. 
 Fig. 86, II, is a curve obtained from the subclavian artery of the same individual. In the femoral 
 artery, the auricular projection is only obtained when the friction of the writing style is reduced to 
 the minimum, and when it occurs, it immediately precedes the beginning of the ascent (Fig. 86, III, 
 a). The pulse curve, in cases of aortic insufficiency, is also characterized by — (i) its considerable 
 
 I. II. III. 
 
 I, II, III, curves with anacrotic elevations, a, in insufficiency ot the aortic valves. 
 
 height; (2) the rapid fall of the lever from the apex of the curve, because a large part of the blood 
 which is forced into the aorta regurgitates into the left ventricle when the ventricle relaxes ; (3) not 
 unfrequently, a projection occurs at the apex, due to the elastic vibration of the tense arterial wall ; 
 (4) the dicrotic wave (R) is small compared 'with the size of the curve itself, because the pulse 
 wave, owing to the lesion of the aortic valves, has not a sufficiently large surface to be reflected from 
 (Fig. 80). The great height of the curve is explained by the large amount of blood projected into 
 the aortic system by the greatly hypertrophied and dilated ventricle. 
 
 74. INFLUENCE OF THE RESPIRATORY MOVEMENTS 
 ON THE PULSE CURVE. — The respiratory movements influence the pulse 
 in two ways— (1) in a purely physical way, by diminishing the arterial pressure 
 during each inspiration and increasing it during expiration ; (2) the respiratory 
 
 Fig. 87. 
 
 Influence of the respiration upon the sphygmogram (after Riegel). J, during inspiration ; E, during expiration. 
 
 movements are accompanied by stimulation of the vasomotor centre, which 
 produces variations of the blood pressure. 
 
 1. Normal Respiration. — During inspiration, owing to the dilatation of the 
 thorax, more arterial blood is retained within the chest, while, at the same time, 
 venous blood is sucked into the right auricle by the aspiration of the thorax ; as a 
 consequence of this, the tension in the arteries during inspiration must be less. 
 The diminution of the chest during expiration favors the flow in the arteries, 
 while it retards the flow of the venous blood in the venae cavae, two factors which 
 raise the tension in the arterial system. The difference of pressure explains the 
 
132 
 
 VALSALVA S AND MULLER S EXPERIMENTS. 
 
 difference in the form of the pulse curve obtained during inspiration and expira- 
 tion, as in Fig. 87 and Fig. 79, I, III, IV, in which J indicates the part of the 
 curve which occurred during inspiration, and E the expiratory portion. The fol- 
 lowing are the points of difference : (1) The greater distention of the arteries 
 during expiration causes all the parts of the curve occurring during this phase to 
 be higher; (2) the line of ascent is lengthened during expiration, because the 
 expiratory thoracic movement helps to increase the force of the expiratory wave ; 
 (3) owing to the increase of the pressure, the dicrotic wave must be less during 
 expiration ; (4) for the same reason, the elastic elevations are more distinct and 
 occur higher in the curve near its apex. The frequency of the pulse is slightly 
 greater during expiration than during inspiration. 
 
 2. This purely mechanical effect of the respiratory movements is modified by 
 the simultaneous stimulation of the vasomotor centre which accompanies these 
 movements. At the beginning of inspiration the blood pressure in the arteries is 
 lowest, but it begins to rise during inspiration, and increases until the end of the 
 inspiratory act, reaching its maximum at the beginning of expiration. During 
 the remainder of the expiration the blood pressure falls until it reaches its lowest 
 level again at the beginning of inspiration (compare §85,/), the pulse curves are 
 
 Fig. 88. 
 
 C, 
 
 C, curve from the carotid, and R, radial, during Mailer's experiment; Ci, and R,, from the same vessels during Val- 
 salva s experiment. Curves written on a vibrating surface. 
 
 similarly modified, and exhibit the signs of greater or less tension of the arteries 
 corresponding to the phases of the respiratory movements {Klemensiewicz, Knoll, 
 Schreiber, Lowit). [There is, as it were, a displacement of the blood-pressure 
 curve relative to the respiratory curve.] 
 
 Forced Respiration.— With regard to the effect produced on the pulse curve 
 by a powerful expiration and a forced inspiration, observers are by no means 
 agreed. 
 
 Valsalva's Experiment. — Strong expiratory pressure is best produced by 
 closing the mouth and nose, and then making a great expiratory effort (§ 60) ; at 
 first there is increase of the blood pressure, while the form of the pulse waves re- 
 sembles that which occurs in ordinary expiration, the dicrotic wave being less 
 developed ; but, when the forced pressure is long continued, the pulse curves have 
 all the signs of diminished tension {Riegel, Frank, and Sommerbrodt). This effect 
 is due to the action of the vasomotor centre, which is affected reflexly from the 
 pulmonary nerves. We must assume that forced expiration, such as occurs in 
 Valsalva's experiment, acts by depressing the activity of the vasomotor centre 3 
 (§ 37 1 . n )- Coughing singing, and declaiming, act like Valsalva's experiment, 
 
INFLUENCE OF PRESSURE ON FORM OF PULSE CURVE. 133 
 
 while the frequency of the pulse is increased at the same time {Sommerbrodi). 
 After the cessation of Valsalva's experiment, the blood pressure rises above the 
 normal state {Sommerbrodf), almost as much as it fell below it ; the normal condi- 
 tion being restored within a few minutes (Lenzmann). 
 
 Miiller's Experiment. — When the thorax is in the expiratory phase, close 
 the mouth and nose, and take a deep inspiration so as forcibly to expand the 
 chest (§ 60). At first the pulse curves have the characteristic signs of diminished 
 tension, viz., a higher and more distinct dicrotic wave; then the tension can, by 
 nervous influences, be increased, just as in Fig. 88, where C and R are tracings 
 taken from the carotid and radial arteries respectively, during Miiller's experi- 
 ment, in which the dicrotic waves, r, r, indicate the diminished tension in the 
 vessels. In Q and R 1( taken from the same person during Valsalva's experiment, 
 the opposite condition occurs. 
 
 Compressed Air. — On expiring into a vessel resembling a spirometer (see Respiration), (Walden- 
 berg's respiration apparatus), and filled with compressed air, the same result is obtained as in Val- 
 salva's experiment — the blood pressure falls and the pulse beats increase ; conversely the inspira- 
 tion from this apparatus, of air under less pressure, acts like Miiller's experiment, i. e., it increases 
 the effect of the inspiration, and afterward increases the blood pressure, which may either remain 
 increased on continuing the experiment, or may fall (Lenzmann). 
 
 The inspiration of compressed air diminishes the mean blood pressure (Zuntz) and the after 
 effect continues for some time. The pulse is more frequent both during and after the experiment. 
 Expiration in rarefied air increases the blood pressure (Zuntz, Lenzmann). The effects which 
 depend upon the action of the nervous system do not occur to the same extent in all cases. Ex- 
 posure to compressed air in a pneumatic cabinet lowers the pulse curve, the elastic vibrations 
 
 Fig. 89. 
 
 Pulsus paradoxus (after Kussntaul). E, expiration ; J, inspiration. 
 
 become indistinct, and the dicrotic wave diminishes and may disappear (v. Vivenot). The heart's 
 beat is slowed and the blood pressure raised [Bert, Jacobsohn, Lazarus'). Exposure to rarefied air 
 causes the opposite result, which is a sign of diminished arterial tension. 
 
 Pulsus Paradoxus. — Under pathological conditions, especially when there is union of the heart 
 or its large vessels with the surrounding parts, the pulse during inspiration may be extremely small 
 and changed, or may even be absent (Fig. 89). This condition has been called pulsus paradoxus 
 (Griesinger, Kussmaul). 
 
 It depends upon a diminution of the arterial lumen during the inspiratory movement. Even in 
 health, it is possible, by a change of the inspiratory movement, to produce the p. paradoxus (Riegel, 
 Sommerbrodt). 
 
 75. INFLUENCE OF PRESSURE UPON THE FORM OF THE PULSE 
 CURVE. — It is most important to know the actual pressure which is applied to an artery 
 while a sphygmogram is being taken. The changes affect the form of the curve as well as the 
 
 relation of the individual parts thereof. In Fig. 90, a, b,c, d, e are radial curves ; a was taken 'P'kt. It/jL 1 ^^*- & 'V 
 with minimal pressure, b with 100, c, 200, d 250, and e 450 grammes pressure, while A, B, C, D .... y , / ja c^j. 
 show the relations as to the time of occurrence of the individual phenomena where the weight was Cd ,if' l<: 
 successively increased. The study of these curves yields the following results : (1) When the weight ' & \C 
 
 is small, the dicrotic wave is relatively less; the whole curve is high; (2) with a moderate weight"* l -' c ^' <f 
 (100 to 200 grammes) the dicrotic wave is bestmarked, the whole curve is somewhat lower; (3) on Lc£^t<-*x- a - 
 increasing the weight the size of the dicrotic wave again diminishes; (4) the fine elastic vibrations 1 ~ r ' - 
 
 preceding the dicrotic wave appear first when a weight of 220 to 300 grammes is used ; (5 ) thej>- jn ' l <rt ' j \ 
 rapidity of the pulse changes with increasing weight, the time occupied by the ascent becoming^/ f, V Y\ n. } 
 shorter, the descent becoming longer ; (6) the height of the entire curve decreases as the weight' uJ ~ , 
 
 increases. In every sphygmogram the pressure under which it was obtained ought always to be/.c,^, t'ttt C^CoC, 
 stated. 
 
 In Fig. 90, A, B are curves obtained from the radial artery of a healthy student. The pressure 
 exerted upon the artery for A was 100; B, 220 grms. (1 vibration =0.01613 sec). 
 
134 
 
 PROPAGATION OF PULSE WAVES IN ELASTIC TUBES. 
 
 If pressure be exerted upon an artery for a long time the strength of the pulse is gradually in- 
 creased. If, after subjecting an artery to considerable pressure, a lighter weight be used, not unfre- 
 quently the pulse curve assumes the form of a dicrotic pulse, owing to the greater development of 
 the dicrotic elevation. When strong pressure is applied, the blood is forced to find its way through 
 collateral channels. When the chief artery ceases to be compressed, the total area is, of course, 
 considerably and suddenly enlarged, which results in the production of a dicrotic elevation. Fig. 
 79, X, is such a dicrotic curve obtained after considerable pressure had been applied to the artery. 
 
 76. RAPIDITY OF TRANSMISSION OF PULSE WAVES.— 
 
 The pulse wave proceeds throughout the arterial system from the root of the aorta, 
 so that the pulse is felt sooner in parts lying near the heart than in the peripheral 
 arteries. E. H. Weber calculated the velocity of the pulse wave as 
 9.240 metres [28^ feet] per second, from the difference in time between 
 the pulse in the external maxillary artery and the dorsal artery of the foot. 
 Czermak showed that the elasticity was not equal in all the arteries, so that the 
 velocity of the pulse wave cannot be the same in all. The pulse wave is propa- 
 gated more slowly in the arteries with soft extensile walls than in arteries with 
 resistant and thick walls, so that it is transmitted more rapidly in the arteries of 
 the lower extremities than in those of the upper. It is still slower in children. 
 
 Fig. 90. 
 
 Various forms of curves (radial) obtained by gradually increasing the pressure. 
 
 77. PROPAGATION OF THE PULSE WAVE IN ELASTIC TUBES.— Waves 
 similar to the pulse may be produced in elastic tubes. (1) According to E. H. Weber, the velocity 
 of propagation of the waves is 11.205 metres per sec; according to Donders, 11-13 metres 
 (34-44 feet). (2) According to E. H. Weber increased internal tension causes only an inconsid- 
 erable decrease ; Rive found a great decrease ; Donders found no obvious difference ; while Marey 
 found an increased velocity. (3) Donders found the velocity to be the same in tubes 2 mm. in dia- 
 meter, as in wider tubes, but Marey believes that the velocity varies when the diameter of the tube 
 changes. (4) The velocity is less, the smaller the elastic coefficient. (5) The velocity increases 
 with increased thickness of the wall, while it diminishes when the specific gravity of the fluid 
 increases. 
 
 Moens has recently formulated the following laws as to the velocity of propagation of waves in 
 elastic tubes: (1) It is inversely proportional to the square root of the specific gravity of the 
 fluid ; (2) it is as the square root of the thickness of the wall, the lateral pressure being the same; 
 (3) it is inversely as the square root of the diameter of the tube, the lateral pressure being the 
 same ; (4) it is as the square root of the elastic coefficient of the wall of the tube, the lateral 
 pressure being the same ( Valentin.) 
 
 Experiments with Caoutchouc Tubes. — For this purpose Landois employs the following 
 apparatus (Fig. 91) : A large tuning fork, A (35 cm. long), carries on one of its arms a glass plate, 
 P (25 cm. long and 5 cm. broad), while the other arm is weighted, G. The tuning fork is fixed by 
 an iron holder, T, to a movable piece of wood, which can be pushed along with the hand in a 
 groove on a support', H, H. When the glass plate is smoked, the curved needle of the angiograph 
 writes its movements upon it. The fork, when it vibrates, makes little teeth in the curve, and the 
 
PROPAGATION OF PULSE WAVES IN ELASTIC TUBES. 
 
 135 
 
 value of each vibration is estimated beforehand. Every complete vibration in this instrument is 
 equal to 0.01613 second. 
 
 Velocity of the Waves in Elastic Tubes filled with Water or Mercury. — Take a soft, 
 extensible, elastic tube, A, 8.80 metres long, I mm. thick, and 7 mm. diameter. If I metre of the 
 tube is weighted with I kilo., it elongates 68 cm. An ampulla, B, capable of containing 50 ex., is 
 fixed to one end of the tube, while to the other end of the ampulla is fixed a mercurial mano- 
 meter, Q. 
 
 FIG. 91. 
 
 Instrument for measuring the velocity ot the pulse wave in an elastic tube containing water 01 mercury. A, tuning- 
 fork ; B, ampulla; A, elastic tube; P, glass plate smoked; Q, manometer; X, pad of lever of angiograph ; 
 writing style, D. 
 
 The tube, A, is shut close to the ampulla every time the pressure is measured, in order to obviate 
 the occurrence of oscillation in the mercury. A certain portion of the tube, say 8 metres, is 
 measured. The beginning, a, and end, b, of this stretch of tubing are placed under the pad, X, of 
 the angiograph. When a positive wave is produced by compressing the ampulla, the writing lever 
 is raised twice, the first time when the wave passes the first part of the tube, a, under the pad, and the 
 second time when the end part of the tube, b, is distended by the wave. The curve obtained is 
 shown in Fig. 92, in which the two elevations, 1 and 2, are obvious. The time between the two 
 
 Fig. 92. 
 
 Pulse curve rom an elastic tube registered upon a plate attached to a vibrating tuning fork. 
 
 may be ascertained by counting the number of vibrations of the tuning fork. The experiments 
 gave the following results : — 
 
 (A) The velocity of the wave is 1 1 .809 metres per second. 
 
 (B) The intravascular pressure has a decided influence on the velocity: thus, in the tube, A, 
 with 18 cm. (Hg) pressure, the velocity per metre = 0.093 second, while with 21 cm. pressure 
 (Hg) = 0.095 second per metre. 
 
 (C) The specific gravity of the liquid influences the velocity of the pulse wave. In mercury the 
 wave is propagated four times more slowly than in water {Marey and Landois). 
 
136 
 
 VELOCITY OF THE PULSE WAVE IN MAN. 
 
 (D) The velocity in a tube which is more rigid and not so extensile is greater than in a tube 
 which is easily distended. 
 
 78. VELOCITY OF THE PULSE WAVE IN MAN.— Landois obtained the follow- 
 ing results in a student whose height was 174 centimetres : Difference between carotid and radial 
 = 0.074 second (the distance being taken as 62 centimetres) ; carotid and femoral = 0.068 second; 
 femoral (inguinal region) and posterior tibial = 0.097 second (distance estimated at 91 centimetres). 
 Z. [Waller obtained between the heart and carotid o. 10 second ; heart and femoral, 0.18 second; 
 heart and dorsalis pedis, 0.22.] 
 
 The velocity of the pulse wave in the arteries of the upper extremities = 
 9.43 metres per second, and in those of the lower extremity 9.40 metres per 
 
 Fig. 93. 
 
 A, curve of radial artery on a vibrating surface (1 vib. = 0.01613 sec.) ; P, apex of curve; e, e, elastic vibrations; R, 
 dicrotic wave ; B, curve of same radial taken along with the heart beat ; v, H, P, contraction of the ventricle. 
 
 second [». <?., about 30 feet per second]. The velocity is greater in the less 
 extensile arteries of the lower extremities than in those of the upper limb. For 
 the same reason it is less in the peripheral arteries and in the yielding arteries of 
 children (Czermak). 
 
 E. H. Weber estimated the velocity at 9.24 metres per second ; Garrod, 9-10.8 metres ; Grashey, 
 8.5 metres; Moens, 8.3 metres, and with diminished pressure during Valsalva's experiment, 7.3 
 metres (J 60, 74). 
 
 Influencing Conditions. — In animals, hemorrhage (Haller), slowing of the heart produced by 
 stimulation of the vagus (Moens), section of the spinal cord, deep morphia narcosis, and dilatation 
 
 Fig. 94. 
 
 Curves of the carotid and posterior tibial, taken simultaneously with Brondgeest's pansphygmograph, writing upon a 
 vibrating plate attached to a tuning fork. The arrows indicate the identical moment of time in each curve. 
 
 of the blood vessels by heat, produce slowing ot the velocity, while stimulation of the spinal cord 
 accelerates it (Grunmach). 
 
 The wave length of the pulse wave is obtained by multiplying the dura- 
 tion of inflow of blood into the aorta, = 0.08 to 0.09 second (§ 51), by the velo- 
 city of the pulse wave. 
 
 Method. — Place the knobs of two tambours (Fig. 72) upon the two arteries to be investigated, 
 or place one over the apex beat and the other upon an artery. These receiving tambours are con- 
 nected with two registering tambours, as in Brondgeest's pansphygmograph ($ 67, Fig. 72),, so that 
 -their writing levers are directly over each other, and so arranged as to write simultaneously on one 
 
VIBRATIONS COMMUNICATED TO THE BODY BY THE HEART. 137 
 
 vibrating plate attached to a tuning fork. [Or they may be made to write upon a revolving cylinder, 
 whose rate of movement is ascertained by causing a tuning fork of a known rate of vibration to 
 write under them.] The apparatus is improved by using rigid tubes and filling them with water, in 
 which all impulses are rapidly communicated. In arteries which are distant from each other, or in 
 the case of the heart and an artery, the two knobs of the receiving tambours may be connected, by 
 means of a Y-tube, with one writing lever. In Fig. 93, B is a curve from the radial artery taken in 
 this way. In it v H P indicates contraction of the ventricle ; H, the apex of the ventricular contrac- 
 tion; P, the primary apex of the radial curve; v, the beginning of the ventricular contraction; p, 
 of the radial pulse. A is the curve of the radial artery alone. From these curves it is evident 
 that in this instance nine vibrations occur between the beginning of the ventricular contraction until 
 the beginning of the pulse in the radial artery = 0.15 second. 
 
 In Fig. 94 the difference between the carotid and the posterior tibial pulse = 0.137 sec. 
 
 Pathological. — In cases of diminished extensibility of the arteries, e.g., in atheroma (j! 77, L>), 
 the pulse wave is propagated more rapidly. Local dilatations of the arteries, as in aneurisms, 
 cause a retardation of the wave, and a similar result arises from local constrictions. Relaxation of 
 the walls of the vessels in high fever retards the movement (ffamernjk). 
 
 79. OTHER PULSATILE PHENOMENA.— 1. In the mouth and nose, when they 
 are filled with air, and the glottis closed, pulsatile phenomena (due to the arteries in their soft parts), 
 may be found communicating a movement to the contained air. The curves obtained are relatively 
 small, and closely resemble the curve of the carotid. A similar pulse is obtained in the tympanum 
 with intact membrana tympani, and when the soft parts of the tympanum are congested (Schwartze, 
 Troltsch). 
 
 2. Entoptical Pulse. — After violent exercise, an illumination, corresponding to each pulse beat, 
 occurs on a dark optical field. When the optical field is bright, an analogous darkening occurs 
 (Landois). The ophthalmoscope occasionally reveals pulsation of the retinal arteries {Jager), which 
 becomes marked in insufficiency of the aortic valves {Quincke, O. Becker, Helfreich). 
 
 3. Pulsatile Muscular Contraction. — The orbicularis palpebrarum muscle contracts under 
 similar conditions synchronously with the pulse ; and it is, perhaps, due to the pulse beat exciting 
 the sensory nerves reflexly. The brothers Weber found that not unfrequently, while walking, the 
 step and pulse gradually and involuntarily coincide. 
 
 4. When the legs are crossed as one sits in a chair, the leg which is supported is raised with each 
 pulse beat, and it gives also a second or dicrotic elevation. 
 
 5. If, while a person is quite quiet, the incisor teeth of the lower jaw be made just to touch the 
 upper incisors very lightly, we detect a double beat of the lower against the upper teeth, owing to 
 the pulse beat in the external maxillary artery raising the lower jaw. The second elevation is due 
 to the closure of the semilunar valves, and not to a dicrotic wave. 
 
 6. Brain and Fontanelles. — The large arteries at the base of the brain communicate a move- 
 ment to it, while similar movements occur with respiration — rising during expiration and falling 
 during inspiration. These movements are visible in the fontanelles of infants. The respiratory 
 movements depend upon variations in the amount of blood in the veins of the cranial cavity, and 
 also upon the respiratory variations of the blood pressure. 
 
 7. Among pathological phenomena are the beating in the epigastrium, e.g., in hypertrophy of 
 the right or left ventricle, caused, it may be, by deep insertion of the diaphragm, and it may be 
 partly by the beating of a dilated abdominal aorta or cceliac axis. 
 
 Abnormal dilatations (aneurisms) of the arteries cause an abnormal pulsation, while they pro- 
 duce a slowing in the velocity of the pulse wave in the corresponding artery. Hence the pulse 
 appears later in such an artery than in the artery on the healthy side. Hypertrophy and dilatation 
 of the left ventricle cause the arteries near the heart to pulsate strongly. In the analogous condition 
 of the right ventricle, the beat of the pulmonary artery may be seen and felt in the second left inter- 
 costal space. 
 
 80. VIBRATIONS COMMUNICATED TO THE BODY BY THE ACTION 
 OF THE HEART. — The beating of the heart and large arteries communicates vibrations to the 
 body as a whole ; the vibration being not simple but compound. 
 
 Gordon was the first to represent this pulsatory vibration graphically. If a person be placed in an 
 erect attitude in the scale pan of a large balance, the index oscillates, and its movements coincide 
 with the heart's movements {Gordon). 
 
 Method. — Landois employed the following arrangement (Fig. 95, I) : Take a long, four-sided 
 box, K, open at the top, and arrange several coils, a, b, of stout caoutchouc tubing round one end. 
 A wooden board, B, smaller than the opening in the box, is so placed that it rests with one end on 
 the caoutchouc tubing, and with the other on the narrow end of the box. The person to be experi- 
 mented upon, A, stands vertically and firmly on this board. A receiving tambour, p, is placed 
 against the surface of the board next the elastic tube, which registers the vibrations of the foot 
 support. Fig. Ill is a curve showing such vibrations, each heart beat being followed in this case by 
 four oscillations. To ascertain the relations and causes of these vibrations, it is necessary to obtain, 
 simultaneously, a tracing of the heart and the vibratory curve. For this purpose me the two tam- 
 bours of Brondgeest's pansphygmograph (§ 67, 6), placing one knob or pad over the heart and the 
 
138 VIBRATIONS COMMUNICATED TO THE BODY BY THE HEART. 
 
 other on the foot support, and allow the writing tambours to inscribe their vibrations on a glass plate 
 attached to a tuning fork. 
 
 In the lower or cardiac impulse curve (Fig. 96), the rapidly-rising part is due to the ventricular 
 systole. It contains eight vibrations (1 vib. = 0.01613 sec). The beginning of the ventriculai 
 systole is indicated in the figure by -36, -3, -17. 
 
 If the corresponding numbers in the upper or vibratory curve are studied, it is obvious that at the 
 
 Fig. 95. 
 
 II. 
 
 /A 
 
 1WMA 
 
 A^ 
 
 D W 
 
 /// ///£/LJ/ / 
 
 K I / 
 
 III. 
 
 I. Elastic support for registering the molar motions of the body — K, a wooden box ; B, feet ot patient ; p, cardio- 
 graph ; a, b, elastic tubing. II. Vibration curves of a healthy person. III. Similar curve obtained .from a 
 patient suffering from insufficiency of the aortic valves and great hypertrophy of the heart. 
 
 moment of ventricular systole the body makes a downward vibration, i.e., it exercises greater pressure 
 upon the foot support. Gordon interprets his curve as giving exactly the opposite result. This down- 
 ward motion, however, lasted only during five vibrations of the tuning fork ; during the last three 
 vibrations, corresponding to the systole,there is an ascent of the body corresponding to a less pressure 
 upon the foot plate. When the ventricle empties itself, it undergoes a movement in a downward 
 and outward direction — Gutbrodt's " reaction impulse." 
 
 In the upper curve, analogous numbers are employed to indicate the vibrations occurring simulta- 
 
 The upper curve is the vibration curve of a healthy person, and the lower one a tracing ot the apex beat. 
 
 neously, viz., -28, -n, -10. The closure ot the semilunar valves is well marked in the three heart 
 beats at 20, -20. This closure is indicated in analogous points in both curves, after which there is 
 a descent of the foot support, and this corresponds to the downward propagation of the pulse wave 
 through the aorta to the vessels of the feet. 
 
 Pathological. — In insufficiency of the aortic valves, as shown in Fig. §6.. III, the vibration 
 communicated to the body is very considerable. 6 y 
 
THE BLOOD CURRENT. 139 
 
 81. THE BLOOD CURRENT. — Cause.— The closed and much 
 branched vascular system, whose walls are endowed with elasticity and contrac- 
 tility, is not only completely filled with blood, but it is over-filled. The total 
 volume of the blood is somewhat greater than the capacity of the entire vascular 
 system. Hence, it follows that the mass of blood must exert pressure on the 
 walls of the entire system, thus causing a corresponding dilatation of the elastic 
 vascular walls (Brunner). This occurs only during life ; after death the muscles 
 of the vessels relax, and fluid passes into the tissues, so that the blood vessels 
 come to contain less fluid, and some of the vessels may be emptied. 
 
 If the blood were uniformly distributed throughout the vascular system, and 
 under the same pressure, it would remain in a position of equilibrium (as after 
 death). If, however, the pressure be raised in one section of the tube, the blood 
 will move from the part where the pressure is higher to where it is lower ; so that 
 the blood current is a result of the difference of pressure within the vas- 
 cular system. If either the aorta or the venae cavse be suddenly ligatured in a 
 living animal, the blood continues to flow, but gradually more slowly, until the 
 difference of pressure is equalized throughout the entire vascular system. 
 
 The velocity of the current will be greater the greater the difference of pressure, 
 and the less the resistance opposed to the blood stream. 
 
 The difference of pressure which causes the current is produced by the heart 
 (£. H. Weber). Both in the systemic and pulmonary circulations, the point of 
 highest pressure is in the root or beginning of the arterial system, while the point 
 of lowest pressure is in the terminal portion of the venous orifices at the heart. 
 Hence, the blood flows continually from the arteries through the capillaries into 
 the venous trunks. 
 
 The heart keeps up the difference of pressure required to produce this result ; 
 with each systole of the ventricles, a certain quantity of blood is forced into the 
 beginning of the arteries, while, at the same time, an equal amount flows from the 
 venous orifices into the auricles during their diastole {E. H. Weber). 
 
 Donders added another important fact, viz., that the action of the heart not 
 only causes the difference of pressure necessary to establish a blood current, but 
 it also raises the mean pressure within the vascular system. The termina- 
 tions of the veins at the heart are wider and more extensible than the arteries where 
 they arise from the heart (Fig. 133). As the heart propels a volume of blood 
 into the arteries equal to that which it receives from the veins, it follows that the 
 arterial pressure must rise more rapidly than the venous pressure diminishes, since 
 the arteries are not so wide nor so extensible as the veins. Thus the total pressure 
 must also increase. 
 
 Cause of Continuous Flow. — The volume of blood expelled from the ven- 
 tricles at every systole would give rise to a jerky or intermittent movement of the 
 blood stream — (1) if the tubes had rigid walls, as in such tubes any pressure 
 exerted upon their contents is propagated momentarily throughout the length of 
 the tube, and the motion of the fluid ceases when the propelling force ceases ; 
 (2) the flow would also be intermittent in character in elastic tubes if the time 
 between two successive systoles were longer than the duration of the current 
 necessary for the compensation of the difference of pressure caused by the systole. 
 If the time between two successive systoles be shorter than the time necessary to 
 equilibrate the pressure, the current will become continuous, provided the 
 resistance at the periphery of the tube be sufficiently great to bring the elasticity 
 of the tube into action. The more rapidly systole follows systole, the greater 
 becomes the difference of pressure, and the more distended the elastic walls. 
 Although the current thus produced is continuous, a sudden rise of pressure is 
 caused by the forcing in of a mass of blood at every systole, so that with every 
 systole there is a sudden jerk and acceleration of the blood stream corresponding to 
 the pulse (compare § 64). 
 
140 CURRENT IN THE CAPILLARIES. 
 
 This sudden jerk-like acceleration of the blood current is propagated through- 
 out the arterial system with the velocity of the pulse wave ; both phenomena are 
 due to the same fundamental cause. Every pulse beat causes a temporary rapid 
 progressive acceleration of the particles of the fluid. But just as the form move- 
 ment of the pulse is not a simple movement, neither is the pulsatile acceleration 
 a simple acceleration. It follows the course of the development of the pulse wave. 
 The pulse curve is the graphic representation of the pulsatory acceleration of the 
 blood stream. Every rise in the curve corresponds to an acceleration, every 
 depression to a retardation of the current. 
 
 [Method : Rigid and Elastic Tubes. — These facts are capable of demonstration by means 
 of very simple physical experiments. Tie a Higginson's syringe to a piece of an ordinary gas pipe. 
 On forcing water through the tube, by compressing the elastic pump, the water will flow out at the 
 other end of the tube in jets, while during the intervals of pulsation no water will flow out. As the 
 walls of the tube are rigid, just as much fluid flows out as is forced into the tube. If a similar 
 arrangement be made, and a long elastic tube be used,* a continuous outflow is obtained, provided 
 the pulsations occur with sufficient rapidity and the length of the tube, or the resistance at its 
 periphery, be sufficient to bring the elasticity of the tube in action. This can be done by putting a 
 narrow cannula in the outflow end of the tube, or by placing a clamp on it so as to diminish the 
 exit aperture. This apparatus converts the intermittent flow into a continuous current.] The fire 
 engine is a good example of the conversion of an intermittent inflow into a uniform outflow. The 
 air in the reservoir is in a state of elastic tension, and it represents the elasticity of the vascular walls. 
 When the pump is worked slowly, the outflow of the water occurs in jets, and is interrupted. If the 
 pumping movement be sufficiently rapid, the compressed air in the reservoir causes a continuous out- 
 flow, which is distinctly accelerated at every movement of the pump. [The ordinary spray-producer 
 is another good example.] 
 
 [Thus, there are two factors — a central one, the heart, and a peripheral one, 
 the amount of resistance in the arterioles. Either or both may be varied, and as 
 this is done so will the pressure and velocity vary.] 
 
 Current in the Capillaries. — In the capillary vessels the pulsatile accelera- 
 tion of the current ceases with the extinction of the pulse wave. The great re- 
 sistance which is offered to the current toward the capillary area causes both to 
 disappear. It is only when the capillaries are greatly dilated, and when the arterial 
 blood pressure is high, that the pulse is propagated through the capillaries into the 
 beginning of the veins. A pulse is observed in the veins of the sub-maxillary 
 gland after stimulation of the chorda tympani nerve, which contains the vascular 
 or vaso-dilator nerves for the blood vessels of this gland. If the finger be con- 
 stricted with an elastic band, so as to hinder the return of the venous blood, and 
 to increase the arterial blood pressure, while at the same time dilating the capil- 
 laries, an intermittent increased redness occurs, which corresponds with the well- 
 known throbbing sensation in the swollen finger. This is due to the capillary 
 pulse. [Roy and Graham Brown found that pulsatile phenomena were produced 
 in the capillaries by increasing the extra-vascular pressure (§ 86). Quincke called 
 attention to the capillary pulse, which can often be seen under the finger nails. 
 Extend the fingers completely, when a whitish area appears under the nails. A 
 red area near the free margin of the nail advances and retires with each pulse beat. 
 It is well marked in some diseased conditions of the heart, especially in incom- 
 petence of the aortic valves, and is probably produced by increased extra-vascular 
 pressure.] 
 
 82. SCHEMATA OF THE CIRCULATION.— E. H. Weber constructed a scheme of the 
 circulation. It consisted of a force-pump with properly arranged valves to represent the heart, por- 
 tions of gut for the arteries and veins, and a piece of glass tubing, containing a piece of sponge, to 
 represent the capillaries. Various schemes have been invented, including the very complicated one 
 of Marey [the extremely ingenious one of v. Thanhoffer, and the thoroughly practical one of 
 Rutherford.] 
 
 83. CAPACITY OF THE VENTRICLES.— Since the right and left 
 ventricles contract simultaneously, and just the same volume of blood passes 
 through the pulmonary as through the systemic circulation, it follows that the 
 
ESTIMATION OF THE BLOOD PRESSURE. 
 
 141 
 
 right ventricle must be just as capacious as the left. The capacity of the ven- 
 tricles has been estimated in the following ways : — 
 
 (i) Directly, by filling the dead ventricle with blood (Santorini, 1^24; Legallois and Collin). 
 This method is unsatisfactory and inaccurate. (2) All the vessels of the relaxed heart are ligatured, 
 the heart excised, and the contents of the cavities estimated (Abegg, 1848). (3) Volkmann estimated 
 the capacity to be j^ 7 of the body weight, i. e., for a man of 75 kilos. = 187.5 g rm s- [§ 5° (Lud- 
 
 wig and Hesse). J 
 
 84. ESTIMATION OF THE BLOOD PRESSURE. — (A) In Animals: (1) 
 Method of Hales. — The Rev. Stephen Hales (1727) was the first to introduce a long glass tube 
 into a blood vessel in order to estimate the blood pressure by measuring the height of the column of 
 blood, i. e., how high the blood rose in the tube. The tube was provided at its lower end with a 
 copper tube bent at a right angle (Pitot's tube). [The tube he used was one-sixth of an inch bore 
 and about nine feet long, and was inserted into the femoral artery of a horse. The height to which 
 the blood rose in the tube was noted, as well as the oscillations that, occurred with every pulsation. 
 From the height of the column of fluid he calculated the force of the heart.] 
 
 (2) The Hsmadynamometer of Poiseuille. — Thisobserver (1828) used a U-shaped tube par- J 
 tially filled with mercury — a manometer — which was brought into connection with a blood vessel ' 
 by means of a rigid tube. [The mercury oscillated with every pulsation, and the extent of the 
 
 Fig. 97. 
 
 I. Scheme of C. Ludwig's kymograph. II. Fick's spring kymograph. 
 
 oscillations was read off by means of a scale attached to the bent tube. He called the instrument a 1 
 h<zmadynamometer.~\ 
 
 [(3) Vierordt used a tube 5 or 6 feet long, and filled it with a solution of sodium carbonate, thus 
 preventing much blood from entering the tube, while at the same time the soda solution prevented 
 the coagulation of the blood.] 
 
 (4) C. Ludwig's Kymograph. — C. Ludwig employed a U-shaped mano- 
 meter of the same kind, but he placed a light float (Fig. 97, d, s) upon the sur- 
 face of the mercury in the open limb of the tube. A writing style, /, placed 
 transversely on the free end of the float, inscribed the movements of the float — 
 and, therefore, of the mercury — upon a cylinder, C, caused to revolve at a uniform 
 rate. This apparatus registered the height of the blood pressure, as well as the 
 pulsatile and other oscillations occurring in the mercury. Volkmann called this 
 instrument a kymograph or " wave writer. " The difference of the height of 
 the column of mercury, c, d, in both limbs of the tube indicates the pressure 
 within the vessel. If the height of the column of mercury be multiplied by 13.5, 
 this gives the height of the corresponding column of blood. Setschenow placed 
 
142 
 
 LUDWIGS KYMOGRAPH. 
 
 a stop-cock in the lower bend, h, of the tube. If this be closed so as just to pe 
 mit a small aperture of communication to remain, the pulsatile vibrations i 
 longer appear, and the apparatus indicates the mean pressure. By the term met 
 pressure is meant the limit q£ pressure^ above and.below which the oscillatio: 
 occurring in an ordinary blood pressure tracing range. [Briefly, it is the averq 
 elevation of the mercurial column.] 
 
 In a blood-pressure tracing, such as Fig. 99, each of the smaller waves corresponds tc 
 
 heart beat, the ascent corresponds to the systc 
 
 Fig. 98. 
 
 and the descent to the diastole. The large u 
 dulations are due to the respiratory mov 
 merits. It is clear that the heart beat is e 
 pressed as -a. simple rise and fall (Fig. 99), 
 that the curve of the heart beat obtained wi 
 a mercurialkymograph differs ffow a sphygm 
 graphic curve. A perfect recording instrume 
 ought to indicate the height of the blood prf 
 sure, and also the size, form, and duration 
 any wave motion communicated to it. Tl 
 mercurial manometer does not give the tn 
 form of the pulse wave, as the mercury, whi 
 once set in motion, executes vibrations of 
 own, owing to its great inertia, and thus tl 
 finer movements of the pulse wave are lo 
 Hence a mercurial kymograph is used for regi 
 tering the blood pressure, and not for obtainii 
 the exact form of the pulse wave. Instrumen 
 with less inertia, and with no vibrations pec 
 liar to themselves, are required for this purpos 
 [The theory of' the mercurial manometer h 
 been carefully worked out by Mach and also 1 
 v. Kries.] 
 
 [Method. — Expose the carotid of a chlora 
 ized rabbit, and isolate a portion of the vess 
 between two ligatures, or two spring clamr. 
 , . With a pair of scissors make an oblique slit in 
 J£^£i££&&&&$±£** artery and into it insert a straight gla 
 by a Foucault's regulator placed on the top of the box. cannula, directing the open end of the cannu 
 The disk, D, moved by the clockwork, presses upon the toward the heart. Fill the cannula with 
 S^ffcS a^rin g C th n e"onof 'JZ^^t Unrated solution of sodium carbonate, taki. 
 cause the cylinder to rotate at different rates. The care that no air bubbles enter, and connect 
 cylinder itself can be raised by the handle, v. On the -witb. the lead tube which goes to the descem 
 
 left side of the figure is a mercurial manometer. When ■ „ i;„,u ~r t-x.^ ~ ~~- n -. r >t- r Z tu« +„k« ...t,:, 
 
 the cylinder is used, it is covered with smoked smooth ln g llmb of the manometer. The tube whi( 
 paper. connects the artery with the manometer mu 
 
 be flexible and yet inelastic, and a lead tube 
 best. It is usual to connect a pressure bottle, containing a saturated solution of sodium carbo: 
 ate, by means of an elastic tube, with the tube attached to the manometer. This bottle can I 
 raised or lowered. Before beginning the experiment, raise the pressure bottle until there is &pos, 
 tive pressure of several inches of mercury in the manometer, or until the pressure is about equal 
 the estimated blood pressure, and then clamp the tube of the pressure bottle where it joins the les 
 tube. By having this positive pressure, the escape of blood from the artery into the solution 
 sodium carbonate is to a large extent avoided. When all is ready, the ligature on the cardiac sic 
 of the cannula is removed, and immediately the float begins to oscillate and inscribe its movemen 
 upon the recording surface. The fluid within the artery exerts pressure latterly upon the sodiu 
 carbonate solution, and this in turn transmits it to the mercury.] 
 
 [Precautions. — In taking a blood-pressure tracing, after seeing that the apparatus is perfe( 
 care must be taken that the animal is perfectly quiescent, as every movement causes a rise of tl 
 blood pressure. This may be secured by giving curara and keeping up artificial respiration, or 1 
 carefully regulated inhalation of ether. When a drug is to be injected to test its action, if it be i: 
 troduced into the jugular vein, it is apt to affect the heart directly. This may be avoided by injec 
 ing it into a vein of the leg, the peritoneum, or under the skin. The solution of the drug must n 
 contain particles which will block up the capillaries. Care should also be taken that the carbona 
 of soda does not flow back into the artery.] 
 
 [Continuous Tracing. — When we have occasion to take a tracing for any length of time, 
 must be written upon a strip of paper which is moved at a uniform rate in front of the writing sty 
 on the float (Fig. 98). Various arrangements are employed for this purpose, but it is usual to cau 
 
 Ludwig 
 m 
 b- 
 
SPRING KYMOGRAPH. 
 
 143 
 
 a cylinder to revolve so as to unfold a roll or riband of paper placed on a movable bobbin. As the 
 cylinder revolves, it gradually winds off the strip of paper, which is kept applied to the revolving 
 surface by ivory friction wheels. In Fick's complicated kymograph a long strip of smoked paper 
 is used. The writing style may consist of a sable brush, or a fine glass pen filled with aniline blue 
 dissolved in water, to which a little alcohol and glycerine are added.] 
 
 [In order to measure the height of the pressure, we must know the position of the abscissa 
 or line of no pressure, and it may be recorded at the same time as the blood pressure or 
 afterward.] 
 
 [In Fig. 99, O — x is the zero line or abscissa, and the height of the vertical lines or ordinates 
 may be measured by the millimetre scale on the left of the figure. The height of the blood pres- 
 sure is obtained by drawing ordinates from the curve to the abscissa, measuring their length, and 
 multiplying by two.] 
 
 (5) Spring Kymograph. — A. Fick (1864) constructed a " hollow spring 
 kymograph," on the principle of Bourdon's manometer (Fig, <yi, II). 
 
 Fig. 99. 
 
 Blood pressure curve of the carotid ol a dog obtained with a mercurial manometer, O — jr = line ot no pressure, zero 
 line, or abscissa ; y—y* is the blood pressure tracing with small waves, each one caused by a heart beat, and the 
 large waves due to the respiration. A millimetre scale shows the height of the pressure in millimetres of 
 mercury. 
 
 A hollow C-shaped metallic spring, F, is filled with alcohol. One end of the hollow spring is 
 closed, and the other end, covered by a membrane, is brought into connection with a blood vessel 
 by a junction piece filled with a solution of sodium carbonate. As soon as the communication 
 with the artery is opened, the pressure rises, and the spring, of course, tends to straighten itself. To 
 the closed end, b, there is fixed a vertical rod attached to a series of levers, h, i, k, e, one of which 
 writes its movements upon a surface moving at a uniform rate. The blood pressure and the 
 periodic variations of the pulse are both recorded, although the latter is not done with absolute 
 accuracy. 
 
 • [Hering improved Fick's instrument (Fig. loo), a, b, c, is the hollow spring filled with alcohol, 
 and communicating at a with the lead tube, d, passing to the cannula in the artery. To c is attached 
 a series of light wooden levers with a writing style s. The lower part of 4 dips into a vessel, e, 
 filled with oil or glycerine, which serves to damp the vibrations of the levers. At f is a syringe 
 communicating with the tube, d, filled with solution of sodic carbonate, and used for regulating the 
 amount of fluid in the tube connecting the manometer with the blood vessel. The whole apparatus 
 can be raised or lowered on the toothed rod, h, by means of the millhead opposite g, to which all 
 the parts of the apparatus are attached.] 
 
144 
 
 FICK S FLAT SPRING KYMOGRAPH. 
 
 (6) Fick's Flat Spring Kymograph. — Fig. 101 shows Fick's latest arrangement. The narrov 
 tube, a, a (i mm. diam.) is placed in connection with a blood vessel by means of the cannula, c 
 and over its vertical expanded end, A, is fixed a caoutchouc membrane, with a projecting point, j 
 which presses against a horizontal spring, F, joined to a writing lever, H, by an intermediate piece 
 b. The whole is held in the metallic frame, R R. 
 
 In order to estimate the absolute pressure, the instrument must be compared previously with i 
 mercurial manometer. 
 
 Fig. ioo. 
 
 \ . Fick's spring manometer, as improved by Hering. 
 
 (B) In man the blood pressure may be estimated by means of. (i) A properly 
 graduated sphygmograph (§67). The pressure required to abolish the move- 
 ment of the lever indicates approximately the vascular tension. Schobel investi- 
 gated the radial pulse in a healthy student, and obtained a mean blood pressure 
 equal to 550 grammes. 
 
 (2) By a manometric method v. Basch estimated the blood pressure. He 
 
 Fig. ioi. 
 
 Fick's flat spring kymograph. 
 
 placed a capsule containing fluid upon a pulsating artery, while the capsule itself 
 communicated with a mercurial manometer. As soon as the pressure within the 
 manometer slightly exceeded that within the artery, the artery was compressed so 
 that a sphygmograph placed on a peripheral portion of the vessel ceased to beat. 
 [This instrument v. Basch called a Sphygmomanometer.] Both arrange- 
 ments, however, do not give the exact pressure within the artery ; they only indi- 
 
BLOOD PRESSURE IN THE ARTERIES. 
 
 145 
 
 cate the pressure which is required to compress the artery and the overlying soft 
 parts. The pressure required to compress the arterial walls, however, is very small 
 compared with the blood pressure. It is only 4 mm. Hg. v. Basch estimated 
 the pressure in the radial artery of a healthy man to be 135 to 165 millimetres of 
 mercury. 
 
 Variations. — In children the blood pressure increases with age, height, and weight. In the 
 superficial temporal artery, from 2 to 3 years, it is = 97 mm. ; from 12 to 13 years, 113 mm. Hg. 
 {A. Eckert, c. \ 100). The blood pressure is raised immediately after bodily movements ; it is 
 higher when a person is in the horizontal position than when sitting, and in sitting than in standing 
 (Friedmann). After a cold as well as after a warm bath (Z. Lehmanri), the first effect is an 
 increase of blood pressure and of the quantity of urine [Grefberg). 
 
 85. BLOOD PRESSURE IN THE ARTERIES.— The following 
 results have been obtained by experiment on systemic arteries : — 
 
 (a) Mean Blood Pressure. — The blood pressure is very considerable, vary- 
 ing within pretty wide limits : in the large arteries of large mammals, and per- 
 haps in man, it is =140 to 160 millimetres [5.4 to 6.4 inches] of a mercurial 
 column. 
 
 The following results have been obtained, those marked thus * by Poiseuille, and those -\- by 
 Volkmann : — 
 
 * Carotid, Horse, 161 mm. 
 
 + 
 * 
 
 " 122 to 214 mm. 
 Dog, 151 mm. 
 
 " 130 to 190mm. [Ludwig). 
 Goat, 118 to 135 mm. 
 Rabbit, 90 mm. 
 Fowl, 88 to 171 mm. 
 
 -\- Aorta of frog, 22 to 29 mm. 
 
 -j- Gill artery of Pike, 35 to 84 mm. 
 Brachial artery of man during an ope- 
 ration, no to 120 mm. (Faivre). 
 Perhaps too low, owing to the in- 
 jury. 
 
 Fig. 102. 
 
 B.R 
 
 r 
 
 H 
 LV. 
 
 R.A. 
 
 Scheme of the height ot the blood pressure, in A, the arteries ; C, 
 capillaries, and V, veins; O-O, is the abscissa or line of no 
 pressure ; L. V., left ventricle, and R. A., right auricle ; B. P., 
 the height of the blood pressure. 
 
 E. Albert estimated the blood pressure by means of a manometer, placed in connection with the 
 anterior tibial artery of a boy whose leg was to be amputated, to be ioo to 160 mm. Hg. The ele- 
 vation with each pulse beat was 1 7 to 
 20 mm. ; coughing raised it to 20 to 30 
 mm. ; tight bandaging of the healthy 
 leg, 15 mm. ; while passive elevation 
 of the body, whereby the hydrostatic 
 action of the column of blood was 
 brought into play, raised it 40 mm. 
 
 The pressure in the aorta of mam- 
 mals varies from 200 to 250 mm. Hg. 
 As a general rule, the blood pressure in 
 large animals is higher than in small 
 animals, because in the former the blood 
 channel is considerably longer, and 
 there is greater resistance to be over- 
 come. In very young and in very old 
 animals the pressure is lower than in 
 individuals in the prime of life. 
 
 The arterial pressure in the foetus is scarcely the half of that of the newly-born, while the venous 
 pressure is higher, the difference of pressure between arterial and venous blood being scarcely half 
 so great as in adult animals (Cohnstein and Zuntz). 
 
 The Arterial blood pressure is highest in the aorta, and falls as we pass 
 toward the smaller vessels, but the fall is very gradual, as shown in Fig. 102. 
 
 A great fall takes place as we pass from the area of the arterioles into the capil- 
 lary area (C), while it is less in the venous area, and negative near the heart, as 
 indicated in the dotted line passing below the abscissa, so that the pressure is 
 lowest in the cardiac ends of the venae cavas (compare Fig. 108). 
 
 (6) Branching of the Blood Vessels. — Within the large arteries the blood 
 pressure diminishes relatively little as we pass toward the periphery, because the 
 difference of the resistance in the different sections of large tubes is very small. 
 As soon, however, as the arteries begin to divide frequently, and undergo a con- 
 siderable diminution in their lumen, the blood pressure in them rapidly diminishes, 
 
146 RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE CURVE. 
 
 because the propelling energy of the blood is much weakened, owing to the resist- 
 ance which it has to overcome (§ 99). 
 
 (/) Amount of Blood. — -The blood pressure is increased with greater filling 
 of the arteries, and vice versa ; hence it 
 
 Increases 
 
 1. With increased and accelerated action 
 
 of the heart ; 
 
 2. In plethoric persons; 
 
 3. After considerable increase of the quan- 
 
 tity of blood by direct transfusion, 
 or after a copious meal. 
 
 Decreases 
 
 1 . During diminished and enfeebled action 
 
 of the heart ; 
 
 2. In anaemic persons ; 
 
 3. After hemorrhage or considerable ex- 
 
 cretions from the blood by sweating, 
 the urine, severe diarrhoea. 
 
 The blood pressure does not vary in the same proportion as the variations in the amount of blood. 
 The vascular system, La virtue of its muscular tissue, has the property, within liberally wide limits, 
 of accommodating itself to larger or smaller quantities of blood ( C. Ludwig and Worm Miiller, \ 
 102, d). [In fact, a large amount of blood may be transfused without materially raising the blood 
 pressure.] Small and moderate hemorrhages (in the dog to 2.8 per cent, of the body weight) have 
 no obvious effect on the blood pressure. After a slight loss of blood the pressure may even rise- [jjj 
 ( Worm Miiller). If a large amount of blood be withdrawn, it causes a great fall of the blood ', 
 pressure (ffales, Magendie), and when hemorrhage occurs to 4-6 per cent, of the body weight, the ,! 
 blood pressure = o. The transfusion of a moderate amount of blood does not raise the mean arte- 
 rial blood pressure. [There are important practical deductions from these experiments, viz., that 
 the blood pressure cannot be diminished directly by moderate bloodletting, and that the blood 
 pressure is not necessarily high in plethoric persons.] 
 
 (d) Capacity of the Vessels. — The arterial pressure rises when the capacity ; 
 of the arterial system is diminished, and conversely. The plain, circularly- ' ,%i 
 disposed muscular fibres of the arteries are the chief agents concerned in this pro- 
 cess. When they relax, the arterial blood pressure falls, and when they contract, 
 it rises. These actions of muscular fibres are controlled and regulated by the 
 action of the vasomotor nerves (§ 371). 
 
 (<?) Collateral Vessels. — The arterial pressure within a given area of the 
 vascular system must rise or fall according as the neighboring areas are diminished, 
 whether by the application of pressure, or a ligature, or are rendered impervious, 
 or as these areas dilate. The application of cold or warmth to limited areas of 
 the body — increasing or diminishing the atmospheric pressure on a part — the 
 paralysis or stimulation of certain vasomotor areas (§ 371), all produce remark- 
 able variations in the blood pressure. [The effect of dilatation of a large vascu- 
 lar area on the arterial pressure is well shown by what happens when the blood 
 vessels of the abdomen are dilated. If the central end of the superior car- 
 diac nerve of a rabbit be stimulated, after a few seconds the blood vessels of the 
 abdomen dilate, and gradually there is a steady fall of the blood pressure in the 
 systemic arteries. Fig. 103 is a blood-pressure tracing showing the height of the 
 blood pressure before stimulation, a. The stimulation was continued from a to b, 
 and after a certain latent period there is a steady fall of the blood pressure. The 
 nerve which causes this reflex dilatation of the abdominal blood vessels, and con- 
 sequent lowering of the blood pressure, is also called the depressor nerve.] 
 
 (/) Respiratory Undulations. — The arterial pressure also undergoes regu- 
 lar variations or undulations owing to the respiratory movements. These undula- 
 tions are called respiratory undulations (Figs. 99 and 104). Stated broadly, 
 during every strong inspiration the blood pressure falls, and during expiration it 
 rises (§ 74). This is not quite correct (see below). These undulations may be 
 explained by the fact that, with every expiration, the blood in the aorta is sub- 
 jected to an increase of pressure through the compressed air in the chest ; with 
 every inspiration, on the other hand, it is diminished, owing to the rarefaction of 
 the air in the lungs acting upon the aorta. Besides, the inspiratory movements of 
 the chest aspirate blood from the venas cavee toward the heart, while expiration 
 retards it, and thus influences the blood pressure. The undulations are most 
 marked in the arteries lying nearest to the heart. The respiratory undulations are 
 
RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE CURVE. 147 
 
 due in part to a stimulation or condition of excitement of the vasomotor centre, 
 which runs parallel with the respiratory movements. This stimulation of the 
 vasomotor centre causes the arteries to contract, and thus the blood pressure is 
 raised. The variations in the pressure which depend upon a varying activity of 
 the vasomotor centre are known as the "curves of Traube and Hering" (p. 
 
 Fig. 103. 
 
 Kymography tracing showing the effect on the blood pressure of stimulation of the central end of the depressor 
 nerve in the rabbit. Stimulation began at a and ended at b; o-x, the abscissa. 
 
 148). In Fig. 104 are represented a blood pressure tracing and a curve of the 
 movements of respiration (thick line) taken simultaneously in a dog by C. Ludwig 
 and Einbrodt. The blood -pressure tracing was obtained from the carotid artery, 
 while the pressure within the thorax was measured by means of a manometer 
 placed in connection with one pleural cavity. In this curve, when expiration 
 
 Fig. 104. 
 
 Kymographic blood-pressure tracing (upper, thin line), and respiration curve (lower, thick line), taken simultaneously. 
 ex, expiration ; in, inspiration ; c, c, heart beats. The large curves in the blood-pressure tracing are due to 
 respirations {Ludwig and Einbrodt.') 
 
 begins (at ex), and as the expiratory pressure rises, the blood pressure rises, while 
 when inspiration begins (at in) both fall. The blood curve, however, begins to 
 rise (at c) before expiration commences, i. e. , during the last part of the act of 
 inspiration. This is due to the contraction of the arteries, caused by impulses 
 sent from the vasomotor centre. It is also aided by the circumstance that during 
 
148 TRAUBE-HERING CURVES. 
 
 inspiration there is an increased inflow of venous blood to the heart, so that when 
 it contracts more blood is forced into the arteries. [The maxima and minima of 
 the two curves do not coincide exactly, but in addition the number of pulse beats 
 is greater in the ascent than in the descent. This is well marked in a blood- 
 pressure tracing from a dog's carotid, while in a rabbit this difference of the pulse 
 rate is but slightly marked. The smaller number of pulse beats during the descent, 
 — i. e., during the greater part of expiration — is due to the activity of the cardio- 
 inhibitory centre in the medulla oblongata. This is proved by the fact, that sec- 
 tion of both vagi in the dog causes the difference of pulse rate to disappear, while 
 other conditions remain the same as before, except that the heart beats more 
 rapidly. It would seem that during the ascent, the cardio-inhibitory centre is 
 comparatively inactive. It is clear, therefore, that the respiratory and cardio- 
 inhibitory centres in the medulla oblongata act, to a certain extent, in unison, 
 so that it is reasonable to suppose that other centres situated in close proximity to 
 these may also act in unison with them, or, as it were, "in sympathy." As 
 already stated, the vaso-motor centre is also in action during a particular part 
 of the time.] 
 
 [If a dog be curarized and artificial respiration established, the respiratory 
 undulations still occur, although in a modified form. In artificial respiration, the 
 mechaniaal conditions, as regards the intra-thoracic pressure, are exactly the reverse 
 of those which obtain during ordinary respiration. Air is forced into the chest 
 during artificial respiration, so that the pressure within the chest is increased during 
 inspiration, while in ordinary inspiration the pressure is diminished. Thus, the 
 same mechanical explanation will not suffice for both cases.] 
 
 If the artificial respiration be suddenly interrupted in a curarized animal, the 
 blood pressure rises steadily and rapidly. This rise is due to the stimulation of 
 the vasomotor centre in the medulla oblongata by the impure blood. This causes 
 contraction of the small arteries throughout the body, which retards the outflow 
 from the large arteries, and thus the pressure within them is raised. [Stated 
 broadly, the arterial pressure depends on the central organ — the heart, and on 
 the condition of the peripheral organs: — the small arteries. Both are influenced 
 by the nervous system. If the action of the vasomotor centre be eliminated by 
 dividing the spinal cord in the cervical region, arrest of the respiration causes a 
 very slight rise of the blood pressure ; hence, it is evident that venous blood acts 
 but slightly on the heart, or on any local peripheral nervous mechanism, or on the 
 muscular fibres of the arteries. This experiment shows that it is the vasomotor 
 centre which is specially acted upon by the venous blood.] 
 
 [Traube-Hering Curves. — The following experiment proves that the varying 
 activity of the vasomotor centres suffices to produce undulations in the blood- 
 pressure tracing. Take a dog, curarize it, expose both vagi and establish artificial 
 respiration ; then estimate the blood pressure in the carotid. After section of the 
 vagi, the heart will continue to beat more rapidly, but it will be undisturbed by 
 the cardio-inhibitory centre. Thus the central factor in the causation of the blood 
 pressure remains constant. Suddenly interrupt the respiration, and, as already 
 stated, the blood pressure will rise steadily and uniformly, owing to the stimula- 
 tion of the vasomotor centre by the venous blood. In this case the peripheral 
 factor or state of tension of the small arteries throughout the body is influenced 
 by the condition of the nerve centre which controls their action. After a time, 
 the blood pressure tracing shows a series of bold curves higher than the original 
 tracing. These can only be due to an alteration in the state of the small arteries, 
 brought about by a condition of rhythmical activity of the vasomotor centre. 
 These curves were described and figured by Traube, and are called the Traube or 
 Traube-Hering curves. As in other conditions, stimulation gives place to exhaus- 
 tion, and soon the venous blood paralyzes the vasomotor centre and the small 
 arteries relax, blood flows freely out of the larger arteries, and the blood pressure 
 rapidly sinks. ■ Variations in the blood pressure have been observed" after a 
 
VARIATIONS OF THE BLOOD PRESSURE. 149 
 
 mechanical pump has been substituted for the heart, i.e., after all respiratory 
 movements have been set aside, so that the only factor which would account for 
 the phenomena of the Traube-Hering curves is the variation in the peripheral 
 resistance in the small arteries, determined by the condition of the vasomotor 
 centre.] 
 
 Variations. — The respiratory undulations of the blood pressure become more pronounced the 
 greater the force of the respirations, which produce greater variations of the intra-thoracic pressure. 
 In man, the diminution of the pressure within the trachea is I mm. Hg, during tranquil inspiration, 
 while during forced respiration, when the respiratory passage is closed, it may be 57 mm. Con- 
 versely, during ordinary expiration, the pressure is increased within the trachea 2-3 mm. Hg, while 
 during forced expiration, owing to the compression of the abdominal muscles, it may reach 87 
 mm. Hg. 
 
 Other Factors. — The increase of the blood pressure during inspiration, as well as the fall during 
 expiration, must; in-^parfj^e'pend'Upon'rhe 'pressure ,: witbiri»th"e*abd«rh¥n\ As the diaphragm descends 
 during inspiration, it presses upon the abdominal contents, including the abdominal vessels, whereby 
 
 Fig. 105. 
 
 Blood pressure tracing taken with a mercurial kymograph irom the carotid of a rabbit; o-x, abscissa; vagus nerve 
 stimulated between the vertical lines, a and b. 
 
 the blood pressure must be increased. The reverse effect occurs during expiration {Schweinburg). 
 [Section of both phrenic nerves and opening of the abdominal cavity cause the respiratory undula- 
 tions almost entirely to disappear. The respiratory undulations, therefore, depend in great part 
 upon the changes of the abdominal pressure and the effect of these changes on the amount of blood 
 in the abdominal vessels. When making a blood-pressure experiment, pressure upon the abdomen 
 of the animal with the hand causes the blood pressure to rise rapidly.] 
 
 (g) Variations with each Pulse Beat. — The mean arterial pressure under- 
 goes a variation with each heart beat ox pulse beat, causing the so-called pulsatory 
 undulations (Fig. 104, c). The mass of blood forced into the arteries with 
 each ventricular systole causes a positive wave and an increase of the pressure cor- 
 responding with it, which, of course, corresponds, in its development and in its 
 form, with the pulse curve. 
 
 In the large arteries, Volkmann found the increase during the heart beat to be = ^ (horse) and 
 IT ( ( '°g) °f tne tota ' pressure. 
 
150 RELATION OF BLOOD PRESSURE TO PULSE RATE. 
 
 None of the apparatus described in \ 84 gives an exact representation of the pulse curve. They 
 all show simply a rise and fall — a simple curve. The sphygmograph alone gives a true expression 
 of the undulations in the blood pressure which are due to the heart beat. 
 
 (h) Arrest of the Heart's Action. — If the heart's action be arrested or 
 interrupted by continued stimulation of the vagus (Brunner, 1855), or by a 
 high positive respiratory pressure (Einbrodf), the arterial blood pressure falls 
 enormously, while it rises in the veins as the blood flows into them from the 
 arteries to equilibrate the difference of pressure in the two sets of vessels. This 
 experiment shows that, even when the difference of pressure is almost entirely set 
 aside, the passive blood presses upon the arterial walls, i.e., on account of the 
 overfilling of the blood vessels, a slight pressure is exerted upon the walls, even 
 when there is no circulation (Brunner). [As already stated, the arterial pressure 
 depends on the condition of the central organ — the heart — and on the peripheral 
 organs— the small arteries. If the action of the heart be arrested, then the blood 
 pressure rapidly falls. Fig. 105 shows the effect on the blood pressure, of arrest- 
 ing the action of the heart, by stimulation of the peripheral end of the vagus. 
 There is a sudden fall of the arterial pressure, as shown by the rapid fall of the 
 curve from #.] 
 
 [Variations in Animals. — The pressure in the arterial system depends upon the balance between 
 the inflow and the outflow, i. c, upon the heart and the state of the arterioles. But it is to be 
 noted that the central factor, the heart, varies in different animals. In the rabbit the heart normally 
 beats rapidly, so that section of the vagi does not cause any great increase in the number of beats, 
 nor is the blood pressure much raised thereby. In the dog, on the other hand, the beats are 
 considerably increased by section of the vagi, while the blood pressure rises considerably. 
 Atropin paralyzes the cardiac terminations of the vagus, and thereby trebles the number of heart 
 beats in the dog, while it only raises it 25 per cent, in the rabbit ; in man, again, the number may 
 be doubled. As Burton has shown, this difference of the initial number of heart beats and the 
 action of the vagus have important relations to the action of drugs on the blood pressure. For 
 example, if an intact rabbit be caused to inhale amyl nitrite, the blood pressure falls at once 
 and rapidly, while in the dog the fall may be slight. - The pulse of the dog, however, is greatly 
 accelerated, so much so as to be nearly as rapid as that of the rabbit. In both, the vessels are 
 dilated, but in the dog, notwithstanding this dilatation, which per se would cause the pressure to 
 fall, the heart of the dog beats now so rapidly as to compensate for this, and thus keep the 
 blood pressure nearly normal ; while the increased rate of beating in the rabbit is not sufficient 
 for this purpose. If the vagi in the dog be divided, the subsequent inhalation of amyl nitrite 
 causes a fall of blood pressure like that in the rabbit (Brunt<m).~\ 
 
 [Relation of Blood Pressure to Pulse Rate. — When the blood pressure 
 rises in an intact animal, as a rule the pulse rate falls, owing to stimulation of the 
 vagus centre increasing the cardio-inhibitory action, while a fall of blood pressure 
 is accompanied by an increase of the number of pulse beats, for the opposite rea- 
 son, the action of the medullary cardio-inhibitory centre being increased. But 
 the blood pressure may be increased either by the action of the heart or the arte- 
 rioles. If we divide the vagi, the pulse beats more quickly, and in some animals 
 the blood pressure rises ; in this case, the rise in the two curves occurs together, 
 and if the vagi be stimulated there is a sudden fall of the blood pressure, due to 
 arrest of the heart's action, so that again the two curves are parallel. If the arte- 
 rioles contract, the blood pressure rises, but by and by the pulse rate falls, owing 
 to the cardio-inhibitory action of the vagus ; while, on the other hand, if the arte- 
 rioles are dilated, the blood pressure falls, and the heart beats faster. Thus, in 
 both of these cases the pulse curve and blood-pressure curve run in opposite direc- 
 tions. These results only obtain when the vagi are intact (Brunton).~\ 
 
 For the effects of the nervous system upon the blood pressure, see " Vasomotor Centre " (§ 
 
 370- 
 
 Pathological. — In persons suffering from granular or contracted kidney and sclerosis of the 
 arteries, in lead poisoning, and after the injection of ergotin, which causes contraction of the 
 small arteries, it is found, on employing the method of v. Basch, that the blood pressure is raised. 
 It is also increased in cases of cardiac hypertrophy with dilatation, and by digitalis in cardiac , 
 affections, while it falls after the injection of morphia (Kristeller). The blood pressure falls in fever 
 [Wetzel), a fact also indicated in the sphygmogram (§ 69). In chlorosis and phthisis the blood 
 pressure is low ( Waldeniurg). 
 
BLOOD PRESSURE IN THE CAPILLARIES. 151 
 
 86. BLOOD PRESSURE IN THE CAPILLARIES.— Methods.— Direct estimation of 
 the capillary pressure is not possible, on account of the smallness of the capillary tubes. If a glass 
 plate of known dimensions be placed on a portion of the skin rich in blood vessels, and if it be 
 weighted until the capillaries become pale, we obtain approximately the pressure necessary to over- 
 come the capillary pressure. N. v. Kries placed a small glass plate (Figs. 106, 107) 2.5-5 s 1- mm., 
 on a suitable part of the skin, eg., the skin at the root of the nail on the terminal phalanx, or on the 
 ear in man, and on the gum in rabbits. Into a scale pan attached to this, weights were placed until 
 the skin became pale. The pressure in the capillaries of the hand, when the hand is raised, Kries 
 found to be 24 mm. Hg. j when the hand hangs down, 54 mm. Hg. ; in the ear, 20 mm. ; and in 
 the gum of a rabbit, 32 mm. 
 
 [Roy and Graham Brown ascertained the hydrostatic pressure necessary to occlude the vessels in 
 transparent parts placed under the microscope, e.g., the web of a frog's foot, tongue or mesentery of 
 a frog, the tails of newts and small fishes. The upper surface of the part to be investigated, e.g., the 
 web of a frog's foot, is made just to touch a thin glass plate. The under surface is in contact with 
 a delicate transparent membrane covering the upper end of a small brass cylinder, whose lower end 
 contains a piece of glass fitted air-tight into it. The interior of the brass cylinder communicates by 
 means of a tube with an arrangement for obtaining any desired pressure, and the amount of the 
 pressure is indicated by a manometer. Air pressure is used, and this is obtained by compressing a 
 caoutchouc bag between two brass plates. The membrane to be investigated lies between two trans- 
 parent media, an upper one of glass and a lower one of transparent membrane, on which the pres- 
 sure acts. Any change in the vessels is observable by means of the microscope. These observers 
 
 Fig. 106. 
 
 Fig. 107. 
 
 Apparatus used by v. Kries for estimating the capillary pressure — a, the small square of glass. In Fig. 106 the scale 
 pan for the weights is below, and in Fig. 107 above. 
 
 conclude from their experiments that the capillaries are contractile, and that their contractility is, to all 
 appearance, in constant action. The regulation of the peripheral blood stream is due not only to • 
 the cerebro-spinal vasomotor centres, but also to independent peripheral vasomotor mechanisms, 
 which may be nervous in their nature, or are due to some direct action on the walls of the vessels 
 (p. 115).] 
 
 Conditions Influencing Capillary Pressure. — The intra-capillary blood 
 pressure in a given area increases — (1) When the afferent small arteries dilate. 
 When they are dilated, the blood pressure within the large arteries is propagated 
 more easily into them. (2) By increasing the pressure in the small afferent arte- 
 ries. (3) By narrowing the diameter of the veins leading from the capillary area. 
 Closure of the veins may quadruple the pressure (v. Kries). (4) By increasing 
 the pressure in the veins, e.g. , by altering the position of a limb). A diminution 
 of the capillary pressure is caused by the opposite conditions. 
 
 Changes in the diameter of the capillaries influence the internal pressure. We have to con- 
 sider the movements of the capillary wall itself (protoplasm movements, Strieker — p. 115), as well 
 as the pressure, swelling and consistence of the surrounding tissues. The resistance to the blood 
 stream is greatest in the capillary area, and it is evident that the blood in a long capillary must exert 
 more pressure at the commencement than at the end of the capillary ; in the- middle of the capillary 
 area the blood pressure is just about one-half of the pressure within the large arteries (Bonders). 
 
152 
 
 BLOOD PRESSURE IN THE VEINS. 
 
 The capillary pressure must also vary in different parts of the body. Thus, the pressure within the 
 intestinal capillaries, in those constituting the glomeruli of the kidney, and in those of lower limbs 
 when the person is in the erect posture, must be greater than in other regions, depending, in the 
 former cases, partly upon the double resistance caused by two sets of capillaries, and in the latter 
 case partly on purely hydrostatic causes. 
 
 87. BLOOD PRESSURE IN THE VEINS.— In the large venous 
 
 trunks near the heart (innominate, subclavian, jugular) a mean negative pressure 
 of about — o. 1 mm. Hg. prevails {H. Jacobsori). Hence, the lymph stream can flow 
 unhindered. As the distance of the veins from the heart increases, there is a gradual 
 increase of the lateral pressure; in the external facial vein (sheep) = -f- 3 mm.; 
 brachial, 4.1 mm., and in its branches 9 mm.; crural, 11. 4 mm. (jacobson). 
 [The pressure is said to be negative when it is less than that of the atmosphere.] 
 
 [The gradual fall of the blood pressure from the capillary area (C) to the venous 
 area (V) is shown in Fig. 108, while within the thorax, where the veins terminate 
 in the right auricle, the pressure is negative.] 
 
 Conditions Influencing the Venous Pressure. — (1) All conditions which 
 diminish the difference of pressure between the arterial and venous systems increase 
 the venous pressure, and vice versa. 
 
 (2) General plethora of blood increases it ; anaemia diminishes it. 
 
 (3) Respiration, or the aspiration of the thorax, affects specially the pressure in 
 the veins near the heart; during inspiration, owing to the diminished tension, 
 blood flows toward the chest, while during expiration it is retarded. The effects 
 are greater the deeper the respiratory movement, and these may be very great 
 when the respiratory passages are closed (§ 60). 
 
 [When a vein is exposed at the root of the neck, it collapses during inspiration, and fill" during 
 expiration — a fact which was known to Valsalva. The respiratory movements do not affect the 
 venous stream in peripheral veins. The veins of the neck and face become distended with blood 
 during crying, and on making violent expiratory efforts, as in blowing upon a wind instrument, 
 while every surgeon is well acquainted with the fact that air is particularly apt to be sucked into the 
 veins, especially in operations near the root of the neck. This is due to the negative intra-thoracic 
 pressure occurring during inspiration.] 
 
 (4) Aspiration of the Heart. - 
 
 Fig. 108. 
 
 -Blood is sucked or aspirated into the auricles 
 when they dilate (p. 77), so that there is a double 
 aspiration — one synchronous with inspiration, and 
 the other, which is but slight, synchronous with 
 the heart beat. There is a corresponding retarda- 
 tion of the blood stream in the venae cavae, caused 
 by the contraction of the auricle (see p. 75, a). 
 The respiratory and cardiac undulations are occa- 
 sionally observable in the jugular vein of a healthy 
 person (§ 99). 
 
 [Braune showed that the femoral vein under Poupart's 
 ligament collapsed when the lower limb was rotated out- 
 ward and backward, but filled again when the limb was 
 restored to its former position. All the veins which open 
 into the femoral vein have valves, which permit blood to 
 pass into the femoral vein, but prevent its reBux. This 
 mechanism acts, to a slight degree, as a kind of suction and 
 pressure apparatus when a person walks, and thus favors the 
 onward movement of the blood.] 
 
 (5) Changes in the position of the limbs or of 
 the body, for hydrostatic reasons, greatly alter 
 the venous pressure. The veins of the lower ex- 
 tremity bear the greatest pressure, while, at the 
 same time, they contain most muscle {K. Bardeleben, §65). Hence, when these 
 muscles, from any cause, become insufficient, dilatations occur in the veins, giving 
 rise to the production of varicose veins. 
 
 Scheme of the blood pressure. H, heart ; a, 
 auricle; v, ventricle; A, arterial; C, 
 capillary; and V, venous areas. The 
 circle indicates the parts within the tho- 
 rax ; B. P., pressure in the aorta. 
 
BLOOD PRESSURE IN THE PULMONARY ARTERY. 153 
 
 [(6) Movements of the Voluntary Muscles. — Veins which lie between muscles 
 are compressed when these muscles contract, and as valves exist in the veins, the 
 flow of the blood is accelerated toward the heart ; if the outflow of blood be 
 obstructed in any way, then the venous pressure on the distal side of the obstruc- 
 tion may be greatly increased. When a fillet is tied on the upper arm, and the 
 person moves the muscles of the forearm, the superficial veins become turgid, and 
 can be distinctly traced on the surface of the limb.] 
 
 [(7) Gravity exercises a greater effect upon the blood stream in the extensile 
 veins than upon the stream in the arteries. It acts on the distribution of the 
 blood, and thus indirectly on the motion of the blood stream. It favors the 
 emptying of descending veins, and retards the emptying of ascending veins, so 
 that the pressure becomes less in the former and greater in the latter. If the posi- 
 tion of the limb be changed, the conditions of pressure are also altered {Pas- 
 chutin). If a person be, suspended with the head " hanging downward, the face 
 soon becomes turgid, the position of the body favoring the inflow of blood 
 through the arteries, and retarding the outflow through the veins. If the hand 
 hangs down it contains more blood in the veins than if it is held for a short time 
 over the head, when it becomes pale and bloodless. As Lister has shown, the 
 condition of the vessels in the limb are influenced not only by the position of the 
 limb, but also by the fact that a nervous mechanism is called into play.] 
 
 [Ligature of the Portal Vein. — The pressure and other conditions vary in particular veins. 
 Thus, if the portal vein be ligatured, there is congestion of the capillaries and rootlets of the portal 
 vein, and dilatation of all the blood vessels in the abdomen, and gradually nearly all the blood of 
 the animal accumulates within its belly, so that, paradoxical as it may seem, an animal may be bled 
 into its own belly. As a consequence of sudden and complete ligature of this vein, the arterial blood 
 pressure gradually and rapidly falls, and the animal dies very quickly. If the ligature be removed 
 before the blood pressure falls too much, the animal may recover. [Schiff and Lautenbach regard 
 the symptoms as due chiefly to the action of a poison, for when the blood of the portal vein in an 
 animal treated in this way is injected into a frog, it causes death within a few hours, while the ordi- 
 nary blood of the portal vein has no such effect.] 
 
 Ligature of the Veins of a Limb. — The effect of ligaturing or compressing all the veins of a 
 limb is well seen in cases where a bandage has been applied too tightly. It leads to congestion and 
 increase of pressure within the veins and capillaries, increased transudation of fluid through the capil- 
 laries, and consequent cedema of the parts beyond the obstruction. Ligature of one vein does not 
 always produce cedema, but if several veins of a limb be ligatured, and the vasomotor nerves be 
 divided at the same time, the rapid production of cedema is ensured. In pathological cases the 
 pressure of a tumor upon a large vein may produce similar results (§ 203).] 
 
 88. BLOOD PRESSURE IN THE PULMONARY ARTERY. —Methods. — (1) 
 Direct estimation of the blood pressure in the pulmonary artery by opening the chest was made 
 by C. Ludwig and Beutner (1850). Artificial respiration was kept up, and the manometer was 
 placed in connection with the left branch of the pulmonary artery. The circulation through the 
 left lung of cats and rabbits was thereby completely cut off, and in dogs to a great extent inter- 
 rupted. There was an additional disturbing element, viz., the removal of the elastic force of the 
 lungs owing to the opening of the chest, whereby the venous blood no longer flows normally into 
 the right heart, while the right heart itself is under the full pressure of the atmosphere. 
 
 The estimated pressure in the dog = 29.6; in the cat = 17.6; in the rabbit, 12 mm. Hg., i. e., 
 in the dog 3 times, the rabbit 4 times, and the- cat 5 times less than the carotid-pressure. 
 
 (2) Hering (1850) experimented upon a calf with ectopia cordis. He introduced glass tubes 
 directly into the heart, by pushing them through the muscular walls of the ventricles. The blood 
 rose to the height of 21 inches in the right tube, and 33.4 inches in the left 
 
 (3) Chauveau and Faivre (1856) introduced a catheter through the jugular vein into the right 
 ventricle, and placed it in connection with a recording tambour (p. 85). 
 
 Indirect measurements have been made by comparing the relative thickness of the walls of 
 the right and left ventricles, or the walls of the pulmonary artery and aorta, for there must be a re- 
 lation between the pressure and the thickness of the muscle in the two cases. 
 
 Beutner and Marey estimated the relation of the pulmonary artery to the aortic 
 pressure as 1 to 3 ; Goltz and Gaule as 2 to 5 ; Fick and Badoud found a pres- 
 sure of 60 mm. in the pulmonary artery of the dog, and in the carotid in mm. 
 Hg. The blood pressure within the pulmonary artery of a child is relatively 
 higher than in the adult (Beneke). 
 
154 BLOOD PRESSURE IN THE PULMONARY ARTERY. 
 
 Elastic Tension of Lungs. — The lungs within the chest are kept in a state 
 of distention, owing to the fact that a negative pressure exists on their outer pleural 
 surface. When the glottis is open, the inner surface of the lung and the walls of 
 the capillaries in the pulmonary air vesicles are exposed to the full pressure of the 
 air. The heart and the large blood vessels within the chest are not exposed to the 
 full pressure of the atmosphere, but only to the pressure which corresponds to the 
 atmospheric pressure minus the pressure exerted by the elastic traction of the 
 lungs (§ 60). The trunks of the pulmonary artery and veins are subjected to the 
 same conditions of pressure. The elastic traction of the lungs is greater the more 
 they are distended. The blood of the pulmonary capillaries will, therefore, tend 
 to flow toward the large blood vessels. As the elastic traction of the lungs acts 
 chiefly on the thin-walled pulmonary veins, while the semilunar valves of the 
 pulmonary artery, as well as the systole of the right ventricle, prevent the blood 
 from flowing backward, it follows that the blood in the capillaries of the lesser 
 circulation must flow toward the pulmonary veins. 
 
 If tubes with thin walls be placed in the walls of an elastic distensible bag, the 
 lumen of these tubes changes according to the manner in which the bag enclosing 
 them is distended. If the bag be directly inflated so as to increase the pressure 
 within it, the lumen of the tubes is diminished {Funke and Latschenberger). If 
 the bag be placed within a closed space, and the tension within this space be 
 diminished so that the bag thereby becomes distended, the tubes in its wall dilate. 
 In the latter case — viz. , by negative aspiration — the lungs are kept distended 
 within the thorax, hence the blood vessels of the lungs containing air are wider 
 than those of collapsed lungs ( Quincke and Pfeiffer, Bowditch and Garland, De 
 Jager). Hence also, more blood flows through the lungs distended within the 
 thorax than through collapsed lungs. The dilatation which takes place during in- 
 spiration acts in a similar manner. The negative pressure that obtains within the' 
 lungs during inspiration causes a considerable dilatation of the pulmonary veins 
 into which the blood of the lungs flows readily, while the blood under high pres- 
 sure in the thick-walled pulmonary artery scarcely undergoes any alteration. The 
 velocity of the blood stream in the pulmonary vessels is accelerated during inspi- 
 ration ( De Jager, Lalesque.) 
 
 The blood pressure in the pulmonary circuit is raised when the lungs are inflated. 
 Contraction of small arteries, which causes an increase of the blood pressure in 
 the systemic circulation, also raises the pressure in the pulmonary circuit, because 
 more blood flows to the right side of the heart {v. Openchowski). 
 
 The vessels of the pulmonary circulation are very distensible and their tonus 
 is slight. [Occlusion of one branch of the pulmonary artery does not raise the 
 pressure within the aorta (Beutner). Even when one pulmonary artery is plugged 
 with an embolon of paraffin, the pressure within the aortic system is not raised . 
 {Lichtheini). Thus, when a large branch of the pulmonary artery becomes im- 
 pervious, the obstruction is rapidly compensated, and this is not due to the action 
 of the nervous system. The vasomotor system has much less effect upon the 
 pulmonary blood vessels than upon those of the systemic circulation {Badoud, ' 
 Hofmokl, Lichtheini). The compensation seems to be due chiefly to the great dis- 
 tensibility and dilatation of the pulmonary vessels {Lichtheini).} 
 
 We know little of the effect of physiological conditions upon the pulmonary 
 artery. According to Lichtheim suspension of the respiration causes an increase of 
 the pressure. [In one experiment he found that pressure within the pulmonary 
 artery was increased, while it was not increased in the carotid, and he regards this 
 experiment as proving the existence of vasomotor nerves in the lung.] Morel 
 found that electrical and mechanical stimulation of the abdominal organs caused a 
 considerable rise of pressure in the pulmonary artery (dog). 
 
 During the act of great straining, the blood at first flows rapidly out of the pulmonary veins and 
 afterward- ceases to flow, because the inflow of blood in the pulmonary vessels is interfered with. 
 As soon as the straining ceases, blood flows rapidly into the pulmonary vessels (Lalesque). 
 
MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM. 155 
 
 Severini found that the blood stream through the lungs is greater and more rapid when the 
 lungs are filled with air rich in C0 2 than when the air within them is rich in O. He supposes 
 that these gases act upon the vascular ganglia within the lung, and thus affect the diameter of 
 the vessels. 
 
 Pathological. — Increase of the pressure within the area of the pulmonary artery occurs frequently 
 in man, in certain cases of heart disease. In these cases the second pulmonary sound is always 
 accentuated, while the elevation caused thereby in the cardiogram is always more marked and 
 occurs earlier (j! 52). 
 
 [Action of Drugs. — The action of drugs on the pulmonary circulation may be tested by Holm- 
 gren's apparatus, which permits of distention of the lung and retention of the normal circulation in 
 the frog. Cold contracts the pulmonary capillaries to one-third of their diameter (Brunton), and 
 anaesthetics arrest the pulmonary circulation, chloroform being most and ether least active, while 
 ethidene is intermediate in its effect [A>P Kendrick, Coats, Newman).~\ 
 
 [Influence of the Nervous System. — The pulmonary circulation is much 
 less dependent on the nervous system than the systemic circulation. Very con- 
 siderable variations of the blood pressure within the other parts of the body may 
 occur, while the pressure within the right heart and pulmonary artery is but slightly 
 affected thereby. The pressure is increased by electrical stimulation of the me- 
 dulla oblongata, and it falls when the medulla is destroyed. Section and stimula- 
 tion of the central or peripheral ends of the vagi, stimulation of the splanchnics, 
 and of the central end of the sciatic, have but a minimal influence on the pressure 
 of the pulmonary artery (Aubert)^\ 
 
 8g. MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM.— 
 
 Methods: (1) A. W Volkmann's Haemadromometer. — A glass tube of the shape of a hair- 
 pin, 60-130 cm. long and 2 or 3 mm. broad, with a scale etched on it, or attached to it, is fixed to a 
 metallic basal plate, B, so that each limb passes to a stop-cock with three channels. The basal plate 
 is perforated along its length, and carries at each end short cannulse, c, c, which are tied into the 
 ends of a divided artery. The whole apparatus is first filled with water [or, better, with salt solu- 
 tion]. The stop-cocks are moved simultaneously, as they are attached to a toothed wheel, and have 
 at first the position given in Fig. 109, 1, so that the blood simply flows through the hole in the basal 
 piece, i.e., directly from, one end of the artery to the other. If at a given moment the stop-cock is 
 turned in the direction indicated in Fig. 109, II, the blood has to pass through the glass tube, and 
 the time it takes to make the circuit is noted, and as the length of the tube is known, we can easily 
 calculate the velocity of the blood. 
 
 Volkmann found the velocity to be in the carotid (dog) = 205 to 35 7 mm. ; 
 carotid (horse) — 306 ; maxillary (horse) = 232 ; metatarsal = 56 mm. per second. 
 The method has very obvious defects arising from the narrowness of the tube ; the 
 introduction of such a tube offers new resistance, while there are no respiratory or 
 pulse variations observable in the stream in the glass tube. 
 
 (2) C. Ludwig and Dogiel (1867) devised a stromuhr or rheometer for 
 measuring the amount of blood which passed through an artery in a given time 
 (Fig. 1 10). It consists of two glass bulbs, A and B, of exactly the same capacity. 
 These bulbs communicate with each other above, their lower ends being fixed, by 
 means of the tubes, c and d, to the metal disk, e e x . This disk rotates round the 
 axis, X Y, so that, after a complete revolution, the tube c communicates with f, 
 and d with g; f and g are provided with horizontally placed cannulae, h and k, 
 which are tied into the ends of the divided artery. The cannula h is fixed in 
 the central end, and k in the peripheral end of the artery {e.g., carotid); the 
 bulb, A, is filled with oil and B with defibrinated blood ; at a certain moment the 
 communication through h is opened, the blood flows in, driving the oil before it, 
 and passes into B, while the defibrinated blood flows through k into the peripheral 
 part of the artery. As soon as the oil reaches m — a moment which is instantly 
 noted, or, what is better, inscribed upon a revolving cylinder — the bulbs, A, B, 
 are rotated upon the axis, X, Y, so that B comes to occupy the position of A. 
 The same experiment is repeated, and can be continued for a long time. The 
 quantity of blood which passes in the unit of time (1 sec.) is calculated from 
 the time necessary to fill the bulb with blood. Important results are obtained by 
 means of this instrument. 
 
156 MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM. 
 
 [As peptone injected into the blood prevents it from coagulating (dog), this fact has been turned 
 to account in using the rheometer.] 
 
 Fig. iio. 
 
 X 
 
 Fig. 109. 
 
 Volkmann's haemadromometer (B). I, blood flows from 
 artery to artery ; II, blood must pass through the 
 glass tube of B ; c, c, cannula; for the divided 
 artery. 
 
 Fig. hi. 
 
 Vierordt's hsematachometer. A, glass ; e, 
 trance : a, exit cannula ; p t pendulum. 
 
 Ludwig & Dogiel's stromuhr or rheometer. 
 X, Y, axis of rotation ; A, B, glass 
 bulbs ; h, k, cannula; inserted in the di- 
 vided artery ; e, e lr rotates on g,f; c, 
 d, tubes. 
 
 (3) Vierordt's Hsematachometer (1858) consists of 
 asmallmeta! box (Fig. m) with parallel glass sides. To 
 the narrow sides of the box are fitted an entrance, e, and an 
 exit cannula, a. In its interior is suspended, against the 
 entrance opening, a pendulum, p, whose vibrations may 
 be read off on a curved scale. [This instrument, as well 
 as Volkmann's apparatus, have only an historical interest.] 
 
 (4) Chauveau and Lortet's (Dromograph) (i860) 
 is constructed on the same principle. A tube, A, B (Fig. 
 112) of sufficient diameter, with a side tube fixed to it, 
 C, which can be placed in connection with a manometer, 
 is introduced into the carotid artery of a horse. At a a 
 small piece is cut out and provided with a covering of 
 
VELOCITY OF THE BLOOD IN THE BLOOD VESSELS. 
 
 157 
 
 gutta-percha which has a small hole in it; through this a light pendulum, a, b, with a long index, b, 
 projects into the tube, i. e., into the blood current, which causes the pendulum to vibrate, and the 
 extent of the vibrations can be read off on a scale, S, S. G is an arrangement to permit the instru- 
 ment to be held. Both this and the former instrument are tested beforehand with a stream of water 
 sent through them with varying velocities. 
 
 Fig. 112. 
 
 Dromograph. A, B, tube inserted in artery ; C, lateral tube connected with a manometer ; b, index moving in ; 
 caoutchouc membrane, a ; G handle. Ill, curve obtained by dromograph. 
 
 Fig. 113. 
 
 The curve of the velocity may be written off on a smoked glass, moving paral- 
 lel with the index, b. The dromograph curve, III, shows the primary elevation, 
 P, and the dicrotic elevation, R. 
 
 90. VELOCITY OF THE BLOOD IN ARTERIES, CAPIL- 
 LARIES AND VEINS. — (1) Division of Vessels. — In estimating the 
 velocity of the blodd, it is important to remember that the sectional area of all 
 the branches of the aorta becomes greater as 
 we proceed from the aorta toward the capil- 
 laries, so that the capillary area is 700 times 
 greater than the sectional area of the aorta 
 \Vierordf). As the veins join and form 
 larger trunks, the venous area gradually be- 
 comes smaller, but the sectional area of the 
 venous orifices at the heart is greater than 
 that of the corresponding arterial orifices. 
 [This is shown in Fig. 113. We may repre- 
 sent the result as two cones placed base to 
 base, the bases meeting in the capillary area 
 (Kiiss). The sectional area of the venous 
 orifice (V) is represented larger than that of 
 the arterial (A). The increased sectional area influences the velocity of 
 the blood current, while the resistance affects the pressure.] 
 
 The common iliacs are an exception ; the sum of their sectional areas is less than that of the 
 aorta; the sections of the four pulmonary veins are together less than that of the pulmonary artery. 
 
 (2) Sectional Area. — An equal quantity of blood must pass through every 
 section of the circulatory system, through the pulmonic as well as through the 
 
 Scheme of the sectional area. 
 V, venous orifice. 
 
 A, arterial, and 
 
158 VELOCITY OF THE BLOOD IN THE BLOOD VESSELS. 
 
 systemic circulation, so that the same amount of blood must pass through the 
 pulmonary artery and aorta, notwithstanding the very unequal blood pressure in 
 these two vessels. 
 
 (3) Lumen. — The velocity of the current, therefore, in various sections of 
 the vessels must be inversely as their lumen. 
 
 (4) Capillaries. — Hence, the velocity must diminish very considerably as we 
 pass from the root of the aorta and the pulmonary artery toward the capillaries, 
 so that the velocity in the capillaries of mammals = 0.8 millimetre per sec. ; 
 frog = 0.53 mm. {E. H. Weber); man = 0.6 to 0.9 (C. Vierordt). According 
 to A. W. Volkmann, the blood in mammalian capillaries flows 500 times slower 
 than the blood in the aorta. Hence, on this view, the total sectional area of all 
 the capillaries must be 500 times greater than that of the aorta. Donders found 
 the velocity of the stream in the small afferent arteries to be 10 times faster than 
 in the capillaries. 
 
 Veins. — The current becomes accelerated in the veins, but in the larger 
 trunks it is 0.5 to 0.75 times less than in the corresponding arteries. 
 
 (5) Mean Blood Pressure. — The velocity of the blood does not depend 
 upon the mean blood pressure, so that it may be the same in congested and in 
 anaemic parts {Volkmann, Hering). 
 
 (6) Difference of Pressure. — On the other hand, the velocity in any sec- 
 tion of a vessel is dependent on the difference of the pressure which exists at the 
 commencement and at the end of that particular section of a blood vessel ; it 
 depends, therefore, on (1) the vis a tergo (J. <?., the action of the heart), and (2) 
 on the amount of the resistance at the periphery (dilatation or contraction of the 
 small vessels) {C. Ludwig and DogieT). 
 
 Corresponding to the smaller difference in the arterial and venous pressure in the foetus (§ 85), 
 the velocity of blood is less in this case {Cohnstein and Zuntz). 
 
 (7) Pulsatory Acceleration. — With every pulse beat 'a corresponding accelera- 
 tion of the blood current (as well as of the blood pressure) takes place in the 
 arteries (pp. 149, 156). In large vessels, Vierordt found the increase of the 
 velocity during the systole to be greater by ^ to J^ than the velocity during the 
 diastole. The variations in the velocity caused by the heart beat are recorded in 
 Fig. 112, obtained by Chauveau's dromograph from the carotid of a horse. The 
 velocity curve corresponds with a sphygmogram — P represents the primary eleva- 
 tion and R the dicrotic wave. This acceleration, as well as the pulse, disappears 
 in the capillaries. A pulsatory acceleration, more rapid during its first phase, is 
 observable in the small arteries, although these are not themselves distended 
 thereby. 
 
 (8) Respiratory Effect. — Every inspiration retards the velocity in the arter- 
 i ies, every expiration aids it somewhat ; but the value of these agencies is very 
 
 small. 
 
 If we compare what has already been said regarding the effect of the respiration on the contrac- 
 tion and dilatation of the heart and on the blood stream (g 60), it is clear that respiration favors 
 the blood stream, so does artificial respiration. When artificial respiration is interrupted, the 
 blood stream becomes slower (Dogiel). If the suspension of respiration lasts somewhat longer, the 
 current is again accelerated on account of the dyspnceic stimulation of the vasomotor centre 
 {Heidenhain) (see Vasomotor Centre, \ 371, 1). 
 
 (9) Conditions Affecting Velocity in the Veins. — Many circumstances 
 affect the velocity of the blood in the veins. (1) There are regular variations in the 
 large veins near the heart {Valsalva) due to the respiration and the movements of 
 the heart (§ 50 and 60). (2) Irregular variations due to pressure, e. g., from 
 contracting muscles (§ 87), friction on the skin in the direction or against the 
 direction of the venous current ; the position of a limb or of the body. The 
 pump-like action of the veins of the groin on moving the leg has been referred to 
 (§ 87). When the lower limb is extended and rotated outward, the femoral 
 
WORK OF THE HEART. 159 
 
 vein in the iliac fossa collapses, owing to an internal negative pressure ; when the 
 thigh is flexed and raised it fills, under a positive pressure (Braune). A similar 
 condition obtains in walking. 
 
 91. ESTIMATION OF THE CAPACITY OF THE VENTRICLES.— Vierordt cal- 
 culated the capacity of the left ventricle from the velocity of the blood stream, and the amount of 
 blood discharged per second by the right carotid, right subclavian, the two coronary arteries, and 
 the aorta below the origin of the innominate artery. He estimated that with every systole of the 
 heart, 172 cubic centimetres (equal to 182 grammes or 6 oz.) of blood was discharged into tht 
 aorta; this, therefore, must he the capacity of the left ventricle (compare <S 83). 
 
 92. THE DURATION OF THE CIRCULATION.— The question 
 as to how long the blood takes to make a complete circuit through the course 
 of the circulation was first answered by Hering (1829) in the case of the horse. 
 He injected a 2 per cent, solution of potassium ferrocyanide into a special vein, 
 and ascertained (by means of ferric chloride) when this substance' appeared in the- 
 blood taken from the corresponding vein on the opposite side of the body. The 
 ferrocyanide may also be injected into the central or cardiac end of the jugular 
 vein, and the time noted at which its presence is detected in the blood of the 
 peripheral end of the same vein. Vierordt (1858) improved this method by 
 placing under the corresponding vein of the opposite side a rotating disk, on which 
 was fixed a number of cups at regular intervals. The first appearance of the potas- 
 sium ferrocyanide is detected by adding ferric chloride to the serum, which separ- 
 ates from the samples of blood after they have stood for a time. The duration of 
 the circulation is as follows : — 
 
 . seconds. 
 
 Horse, , . 
 
 . . 31.5 seconds. 
 
 Hedgehog, 7.61 
 
 Dog, . . 
 
 . . 16.7 " 
 
 Cat, 6.69 
 
 Rabbit, . 
 
 . ■ 7-79 " 
 
 Goose, 10.86 
 
 Duck, . . 
 
 . 10.64 seconds. 
 
 Buzzard, , 
 
 . 6.73 
 
 Fowl, . 
 
 . . 5-17 
 
 Results. — When these numbers are compared with the frequency of the normal 
 pulse beat in the corresponding animals, the following deductions are obtained : 
 
 (1) The mean time required for the circulation is accomplished during 27 heart 
 beats, i. e., for man = 32.2 seconds, supposing the heart to beat 72 times per 
 minute. 
 
 (2) Generally, the mean time for the circulation in two warm-blooded animals 
 is inversely as the frequency of the pulse beats. 
 
 Conditions Influencing the Time. — The time is influenced by the follow- 
 ing factors : 
 
 1. Long vascular channels {e.g., from the metartarsal vein of one foot to the other foot) re- 
 quire a longer time than short channels (as between the jugulars). The difference may be equal to 
 10 per cent, of the time required to complete the entire circuit. 
 
 2. In young animals (with shorter vascular channels and higher pulse rate) the time is shorter 
 than in old animals. 
 
 3. Rapid and Energetic cardiac contractions (as during muscular exercise) diminish the time. 
 Hence rapid and at the same time less energetic contractions (as after section of both vagi), and 
 slow but vigorous systoles (e. g., after slight stimulation of the vagus) have no effect. 
 
 C. Vierordt estimated the quantity of blood in a man, in the following manner. In all warm- 
 blooded animals, 27 systoles correspond to the time for completing the circulation. Hence, the 
 total mass of the blood must be equal to 27 times the capacity of the ventricle, i. c, in man, 187.5 
 grms. X 27 = 5062.5 grms. This is equal to ^ s of the body weight in a person weighing 65.8 
 kilos, (compare \ 49). 
 
 It is not to be forgotten that the salt used is to some extent poisonous (p. 103), but Hermann uses 
 the corresponding innocuous soda salt (25 per cent.). 
 
 Pathological. — The duration of the circulation seems to be increased during septic fever (E. 
 Wolff). 
 
 93. WORK OF THE HEART.— Johann Alfons Borelli (1679) and Julius Robert Mayer 
 estimated the work done by the heart. The work of a motor is expressed in kilogramme metres, 
 i. e., the number of kilos, which the motor can raise in the unit of time to the height of 1 metre. 
 
 The left ventricle expels 0.188 kilo, of blood {Volkmann) with each systole, 
 and in doing so it overcomes the pressure in the aorta, which is equal to a column 
 of blood 3.21 metres in height (^Bonders). [The amount of blood expelled from 
 
160 BLOOD CURRENT IN THE SMALLEST VESSELS. 
 
 each ventricle during the systole is about 180 grms. (6 oz.). It is forced out 
 against a pressure of 250 mm. Hg. = 3.21 metres of blood.] The work of the 
 heart at each systole is 0.188 X 3-21 = o. 604 kilogramme metres. If the number 
 of beats = 75 per minute, then the work of the left ventricle in 24 hours = 
 (0.604 X 75 X 60 X 24) = 65,230 kilogramme metres. While the " work " done 
 by the right ventricle is about one-third that of the left, and therefore = 21,740 
 kilogramme metres. Both' ventricles do work equal to 86,970 kilogramme metres. 
 A workman during eight hours produces 300,000 kilogramme metres, /. e, about 
 four times as much as the heart. As the whole of the work of the heart is con- 
 sumed in overcoming the resistance within the circulation, or rather is converted 
 into heat, the body must be partly warmed thereby (425.5 gramme metres are 
 equal to 1 heat unit, i. <?., the force required to raise 425.5 grammes to the height 
 of 1 metre may be made to raise the temperature of 1 cubic centimetre of water 
 i° C.) So that 204,000 "heat units" are obtained from the transformation of 
 the kinetic energy of the heart. 
 
 One gramme of coal when burned yields 8080 heat units, so that the heart yields 
 as much energy for heating the body as if about 25 grammes of coal were burned 
 within it to produce heat. 
 
 94. BLOOD CURRENT IN THE SMALLER VESSELS.— 
 Methods. — The most important observations for this purpose are made by means 
 of the microscope on transparent parts of living animals. Malpighi was the 
 first to observe the circulation in this way in the lung of a frog (1661). 
 
 The following parts have been employed : The tails of tadpoles and small fishes ; the web, 
 tongue, mesentery, and lungs of curarized frogs ( Cowper, 1704) ; the wing of the bat, the third eye- 
 lid of the pigeon or fowl ; the mesentery ; the vessels of the liver of frogs and newts ( Gruithuisen), 
 of the pia mater of rabbits, of the skin on the belly of the frog, of the mucous membrane of the 
 inner surface of the human lip {Hater's Cheilangioscope, 1879); °f ' ne conjunctiva of the eyeball 
 and eyelids. All these may be examined by reflected light. 
 
 [Holmgren's Method. — In studying the circulation in the frog's lung, it must be inflated. A 
 cannula with a bulge on its free end is placed in the larynx, while to the other end is fixed a piece 
 of caoutchouc tubing. The lung is inflated and then the caoutchouc tube is closed, after which the 
 lung is placed in a chamber with glass above and below, and examined microscopically.] 
 
 [Entoptical appearances of the circulation [Purkinje, iSij). Under certain conditions a 
 person may detect the movement of the blood- corpuscles within the blood vessels of his own eye. 
 The best method is that of Rood, viz., to look at the sky through a dark-blue glass, or through sev- 
 eral pieces of cobalt glass placed over each other {Helmholtz).~\ 
 
 Form and Arrangement of Capillaries. — Regarding the form and arrangement of the 
 capillaries, we find that : — 
 
 1 . The diameter, which in the finest permits only the passage of single corpuscles in a row — 
 one behind the other — may vary from 5 ft to 2 /j., so that two or more corpuscles may move 
 abreast when the capillary is at its widest. 
 
 2. The length is about 0.5 mm. They terminate in small veins. 
 
 3. The number is very variable, and the capillaries are most numerous in those tissues where 
 the metabolism is most active, as in lungs, liver, muscles — less numerous in the sclerotic and in 
 the nerve trunks. 
 
 4. They form numerous anastomoses, and give rise to networks, whose form and arrangement are 
 largely determined by the arrangement of the tissue elements themselves. They form simple loops in 
 the skin, and polygonal networks in the serous membranes, and on the surface of many gland tubes; 
 they occur in the form of elongated networks, with short connecting branches in muscle and nerve, as 
 well as between the straight tubules of the kidney ; they converge radially toward a central point in 
 the lobules of the liver, and form arches in the free margins of the iris, and on the limit of the 
 sclerotic and cornea. 
 
 [A great contrast as to the vascularity of two adjacent parts is seen in the gray and white 
 matter of the brain, the former being very vascular, the latter but slightly so.] 
 
 [Direct termination of Arteries in Veins. — Arteries sometimes terminate directly in veins, 
 without the intervention of capillaries, e.g., in the ear of the rabbit, in the terminal phalanges 
 of the fingers and toes in man and some animals, in the cavernous tissue of the penis (I/byer). 
 They may be regarded as secondary channels which protect the circulation of adjacent parts, 
 and they may also be related to the heat-regulating mechanisms of peripheral parts (ffoyer).] 
 
 End Arteries. — In connection with -the termination of arteries in capillaries, it is important 
 to ascertain if the arterioles are " end or terminal arteries,'' i. e., if they do not form any fur- 
 
CAPILLARY CIRCULATION. 161 
 
 ther anastomoses with other similar arterioles, but terminate directly in capillaries, and thus 
 only communicate by capillaries with neighboring arterioles — or the arteries may anastomose with 
 other arteries just before they break up into capillaries. This distinction is important in connection 
 with the nutrition of parts supplied by such arteries (Coknheim). 
 
 Capillary Circulation. — On observing the capillary circulation, we notice 
 that the red corpuscles move only in the axis of the current (axial current), while 
 the lateral transparent plasma current flowing on each side of this central thread 
 is free from these corpuscles. [The axial current is the more rapid.] This plasma 
 layer or " Poiseuille's space " is seen in the smallest arteries and veins, where 
 | is taken up with the axial current, and the plasma layer occupies \ on each side 
 of it (Fig. 114). A great many, but not all, of the colorless corpuscles run in 
 this layer. It is much less distinct in the capillaries. Rud. Wagner stated that it 
 is absent in the finest vessels of the lung and gills [although Gunning was unable 
 to confirm this statement.] The colored corpuscles move in the smallest capillaries 
 in single file, one after the other ; in the larger vessels several corpuscles may move 
 abreast, with a gliding motion, and in their course they may turn over and even 
 be twisted if any obstruction is offered to the blood stream. As a general rule, 
 in these vessels the movement is uniform, but at a sharp bend of the vessel it may 
 partly be retarded and partly accelerated. Where a vessel divides, not unfre- 
 quently a corpuscle remains upon the projecting angle of the division, and is 
 doubled over it so that its ends project into the two branches of the tube. There 
 it may remain for a time, until it is dislodged, when it . soon regains its original 
 form, on account of its elasticity. Not unfrequently we see a red corpuscle becom- 
 ing bent where two vessels meet, but on all occasions it rapidly regains its original 
 form. This is a good proof of the elasticity of the colored corpuscles. 
 
 Colorless Corpuscles. — The motion of the colorless corpuscles is quite dif- 
 ferent in character ; they roll directly on the vascular wall, moistened on their 
 peripheral zone by the plasma in Poiseuille's space, their other surface being in 
 contact with the thread of colored corpuscles in the centre of the stream. 
 Schklarewsky has shown by physical experiments, that the particles of least spe- 
 cific gravity in all capillaries (e.g., of glass) are pressed toward the wall, while 
 those of greater specific gravity remain in the middle of the stream. [Graphite 
 and particles of carmine were suspended in water, and caused to circulate through 
 capillary tubes placed under a microscope, when the graphite kept the centre of 
 the stream, and the carmine moved in the layer next the wall of the tube.] 
 
 When the colorless corpuscles reach the wall of the vessel, they must roll along, 
 partly on account of their surface being sticky, whereby they readily adhere to the 
 vessel, and partly because one surface is directed toward the axis of the vessel 
 where the movement is most rapid, and where they receive impulses directly from 
 the rapidly moving colored blood corpuscles (Ponders). The rolling motion is 
 not always uniform; not unfrequently it is retrograde in direction, which seems to 
 be due to an irregular adhesion to the vascular wall. Their slower movement (10 
 to 1 2 times slower than the red corpuscles) is partly due to their stickiness, and 
 partly to the fact that as they are placed near the wall, a large part of their surface 
 lies in the peripheral threads of the fluid, which, of course, move more slowly (in 
 fact the layer of fluid next the wall is passive — p. 109). 
 
 [D. J. Hamilton finds that, when a frog's web is examined in a vertical posi- 
 tion, by far the greater proportion of leucocytes float on the upper surface, and 
 only a few on the lower surface, of a small blood vessel. In experiments to deter- 
 mine why the colored corpuscles float or glide exclusively in the axial stream, 
 while a great many, but not all, of the leucocytes roll in the peripheral layers, 
 Hamilton ascertained that the nearer the suspended body approaches to the spe- 
 cific gravity of the liquid in which it is immersed, the more it tends to occupy 
 the centre of the stream. He is of opinion that the phenomenon of the separa- 
 tion of the blood corpuscles in the circulating fluid is due to the colorless cor- 
 puscles being specifically lighter, and the colored either of the same or of 
 
162 
 
 DIAPEDESIS. 
 
 very slightly greater specific gravity than the blood plasma. Hamilton contro- 
 verts the statement of Schklarewsky, and he finds that it is the relative specific 
 gravity of a body which ultimately determines its position in a tube. These 
 experiments point to the immense importance of a due relation subsisting between 
 the specific gravity of the blood plasma and that of the corpuscles.] 
 
 In the vessels first formed in the incubated egg, as well as in those of young tadpoles, the move- 
 ment of the blood from the heart occurs in jerks {Spallanaani, 1768). 
 
 The velocity of the blood stream is influenced by the diameter of the vessels, 
 which undergo periodic changes of calibre. This change occurs not only in 
 vessels provided with muscular fibres, but also in the capillaries, which vary in 
 diameter, owing to the contraction of the cells composing their walls (p. 115). 
 
 The amount of water in the blood is of importance, as when it is increased the 
 circulation is facilitated and accelerated {C. A. Ewald) (§ 62). 
 
 The velocity of the blood is greater m the pulmonary than in the systemic 
 capillaries {Hales, 1727) ; hence, we must conclude that the total sectional area 
 of the pulmonary capillaries is less than that of all the systemic capillaries. 
 
 95. PASSAGE OF THE BLOOD CORPUSCLES OUT OF THE VESSELS— 
 DIAPEDESIS. — Diapedesis. — If the circulation be studied in the vessels of the mesentery, we 
 may observe colorless corpuscles passing out of the vessels in greater or less numbers (Fig. 114). 
 The mere contact with the air suffices to excite slight inflammation. At first, the colorless cor- 
 puscles in the plasma space move more slowly ; several accumulate near each other, and adhere to 
 the walls — soon they bore into the wall ; ultimately they pass quite through it, and may wander for a 
 distance into the perivascular tissues. It is doubtful whether they pass through the so-called 
 " stomata " which exist between the endothelial cells, or whether they simply pass through the 
 cement substance between the endothelial cells (p. 113). This process is called Diapedesis, and 
 consists of several acts : (a) The adhesion of lymph cells or colorless corpuscles to the inner surface 
 of the vessel (after moving more slowly along the wall up to this point), (b) They send processes 
 
 into and through the vascular wall, (c) The body 
 of the cell is drawn after or follows the processes, 
 whereby the corpuscle appears constricted in the 
 centre (Fig. 114, c). (d) The complete passage 
 of the corpuscle through the wall, and its further 
 motion in virtue of its own amoeboid movements. 
 Hering observed that in large vessels with peri- 
 vascular lymph spaces, the corpuscles passed into 
 these latter, hence, cells are found in lymph 
 before it has passed through lymphatic glands. The 
 cause of the diapedesis is partly due to the inde- 
 pendent locomotion of the corpuscles, and it is 
 partly a physical act, viz., a filtration of the colloid 
 mass of the cell under the force of the blood 
 pressure {Hering) — in the latter respect depending ; 
 upon the intravascular pressure and the velocity I 
 of the blood stream. Hering regards this process,' I 
 
 c ., ", , ., . , r . . j. and even the passage of the colored corpuscles ' 
 
 Small vessel of the mesentery of a frog, showing the 4 , t_ ..,_ , ,, , r 
 
 diapedesis of the colorless corpuscles. 10, ■w, vas- ™p u g n tne vascular wall, as a normal p rocess^ 
 cular walls ; a, a, Poiseuille's space ; r, r, red por^-The red corpuscles pass out of the vessels when 
 puscles; /, /, colorless corpuscles adhering to the the venous outflow is obstructed, which also causes 
 wall, and c, c. m various stages of extrusion ; /if. . , - ... r , , ' 
 
 extruded corpuscles. ' v the transudation of plasma through the vascular 
 
 wall. The plasma carries. the colored corpuscles 
 along with it, and at the moment of their passage through the wall they assume extraordinary 
 shapes, owing to the tension put upon them, regaining their shape as soon as they pass out {Cohn- 
 heitri). - - 
 
 This remarkable phenomenon was described by Waller in 1846. It was recently redescribed by 
 Cohnheim, and according to him the ou t- wanderi ng is a s ign of infl ammation, and the colorless cor- 
 puscles which accumulate in the tissues are to be~regardecT as pus corpuscles, which may undergo 
 further increase by division. 
 
 Stasis. — When a strong stimulus acts on a vascular part, hyperaemic redness and swelling occur. 
 Microscopic observation shows that the capillaries and the small vessels are dilated and overfilled 
 with blood corpuscles; in some cases a temporary narrowing precedes the dilatation; simultaneously 
 the velocity of the stream changes; rarely there is a temporary acceleration, more frequently it be- 
 comes slower. If the action of the stimulus or irritant be continued, the retardation becomes con- 
 
 Fig. 
 
MOVEMENT OF THE BLOOD IN THE VEINS. 163 
 
 siderable, the stream moves in jerks, then follows a to and fro movement of the blood column — 
 a sign that stagnation has taken place in other vascular areas. At last, the blood stream comes 
 completely to a standstill — stasis — and the blood vessels are plugged with blood corpuscles. 
 Numerous colorless blood corpuscles are found in the stationary blood. While these various 
 processes are taking place, the colorless corpuscles — more rarely the red — pass out of the vessels. 
 Under favorable circumstances the stasis may disappear. The swelling which occurs in the neigh- 
 borhood of inflamed parts is chiefly due to the exudation of plasma into the surrounding tissues. 
 [The vapor of chloroform causes hyperaemia of the web (Lzs/er).] 
 
 96. MOVEMENT OF THE BLOOD IN THE VEINS.— As already 
 mentioned, in the smallest veins coming from the capillaries the blood stream is 
 more rapid than in the capillaries themselves, but less so than in the correspond- 
 ing arteries. The stream is uniform, and if no other conditions interfered with 
 it, the venous stream toward the heart ought to be uniform, but many circum- 
 stances affect the stream in different parts of its course. Among these are: (1) 
 The relative laxness, great distensibility and the ready compressibility of the walls, 
 even of the thickest veins. (2) The incomplete filling of the veins, which does not 
 amount to any considerable' distention of their walls. (3) The numerous and free 
 anastomoses between adjoining veins, not only between veins lying in the same 
 plane, but also between superficial and deep veins. Hence, if the course of the 
 blood be obstructed in one direction, it readily finds another outlet. (4) The 
 presence of numerous valves, which permit the blood stream to move only in a 
 centripetal direction (Fabricius ab Aquapendente). They are absent from the 
 smallest veins, and are most numerous in those of middle size. 
 
 Law of the Position of Valves. — The venous valves always have two pouches, and are placed 
 at definite intervals, which correspond to the I, 2, 3, or n th power of a certain " fundamental dis- 
 tance," which is = 7 mm. for the lower extremity and 5.5 mm. for the upper. Many of the origi- 
 nal valves disappear. On the proximal side of every valve a lateral branch opens into the vein, 
 while on the distal side of each branch lies a valve. The same is true for the lymphatics (JC 
 Bardeleberi). 
 
 Effect of Pressure. — As soon as pressure is applied to the veins, the next 
 lowest valves close, and those immediately above the seat of pressure open and 
 allow the blood to move freely toward the heart. The pressure may be exerted 
 from without, as by anything placed against the body ; the thickened contracted 
 muscles, especially the muscles of the limbs, compress the veins. That the blood 
 flows out of a divided vein more rapidly when the muscles contract, is shown 
 during venesection. If the muscles are kept contracted, the venous blood 
 passing out of the muscles collects in the passive parts, e. g., in the cutaneous 
 veins. The pulsatile pressure of the arteries accompanying the veins favors the 
 venous current (Ozanam). From a hydrostatic point of view, the valves are 
 of considerable importance, as they serve to divide the column of blood into 
 segments {e. g., in the crural vein in the erect attitude), so that the fine blood 
 vessels in the foot are not subjected to the whole amount of the hydrostatic 
 pressure in the veins. 
 
 The velocity of the venous blood has been measured directly (with the hsemadromometer and 
 the strotmihr — \ 89). Volkmann found it to be 225 mm. per sec. in the jugular vein. Reil ob- 
 served that lyi times more blood flowed from an arterial orifice than from a venous orifice of the 
 same size. The velocity of the venous current obviously depends upon the sectional area of the 
 vessel. Borelli estimated the capacity of the venous system to be 4 times greater than that of 
 the arterial ; while, according to Haller, the ratio is 9 to 4. 
 
 Large Veins. — As we proceed from the small veins toward the venae cavae, the 
 sectional area of the veins, taken as a whole, becomes less, so that the velocity of 
 the current increases in the same ratio. The velocity of the current in the vena? 
 cavae may be about half of that in the aorta {Haller). 
 
 As the pulmonary veins are narrower than the pulmonary artery, the blood 
 moves more rapidly in the former. 
 
 [Active pulsation occurs in the veins of the wing of the bat [Schiff).~\ \ 
 
164 VENOUS MURMURS. 
 
 97. SOUNDS OF BRUITS WITHIN ARTERIES.— These murmurs, sounds or bruits, 
 occur either spontaneously, or are produced by the application of external pressure, whereby the 
 lumen of the vessel is diminished. In four-fifths of all healthy men, two sounds — corresponding 
 in duration and other characters to the two heart sounds — are heard in the carotid ( Conrad, Weil). 
 Sometimes only the second heart sound is distinguishable, as its place of origin is near to the carotid. 
 They are not true arterial sounds, but are simply "propagated heart sounds." 
 
 Arterial Sounds or murmurs are readily produced by pressing upon a strong- 
 artery, e.g., the crural in the inguinal region, so as to leave only a narrow passage 
 for the blood (" stenosal murmur "). A fine blood stream passes with great: 
 rapidity and force through this narrow part into a wider portion of the artery 
 lying behind the point of compression. Thus arises the "pressure stream " {P. 
 Niemeyer), or the " fluid vein " (" Veine fluide " of Chauveau). The particles- 
 of the fluid are thrown into rapid oscillation, and undergo vibratory movements,, 
 and by their movements produce the sound within the peripheral dilated portion 
 of the tube. A sound is produced in the fluid by pressure {Corrigan, Heynsius). 
 The sounds are not caused by vibrations of the vascular wall, as supposed by 
 Bouillaud. < 
 
 A murmur of this sort is the "sub-clavicular murmur " (Roser), occasionally heard during 
 systole in the subclavian artery ; it occurs when the two layers of the pleura adhere to the apex of 
 the lung (especially in tubercular diseases of the lungs), whereby the subclavian artery undergoes a 
 local constriction due to its being made tense and slightly curved [Friedreich). This result is indi- 
 cated in a diminution or absence of the pulse wave in the radial artery ( Weil). 
 
 Arterial murmurs are favored by — (i) Sufficient delicacy and elasticity of the 
 arterial walls (Th. Weber). (2) Diminished peripheral resistance, e.g., an easy 
 outflow of the fluid at the end of the stream (KiwiscK). (3) Accelerated current 
 in the vascular system generally. (4) A considerable difference of the pressure 
 in the narrow and wide portions of the tube {Marey). (5) Large calibre of the- 
 arteries. 
 
 It is obvious that arterial murmurs will occur in the human body — (a) When, owing to patho- 
 logical conditions, the arterial tube is dilated at one part, into which the blood current is forcibly 
 poured from the normal narrow tube. Dilatations of this sort are called aneurisms, within whichi 
 murmurs are generally audible, [b) When pressure is exerted upon an artery, e.g., by the pressure 
 of the greatly enlarged arteries during pregnancy, or by a large tumor pressing upon a large artery. 
 (c) A murmur corresponding to each pulse beat is heard, especially where two or more large arteries 
 lie together; hence, during pregnancy, we hear the uterine murmur, or placental bruit, or souffle- 
 in the greatly dilated uterine arteries. It is much less distinct in the umbilical arteries of the cord 
 (umbilical murmurs). Similar sounds are heard through the thin walls of the head of infants. 
 [Fisher, 1833). A murmur due to the systole of the heart is often heard in the carotid (Jurasz). 
 In such cases where no source of external pressure is discoverable, and when no aneurism is present, 
 the spontaneously occurring sounds are favored, when at the moment of arterial rest (cardiac systole) 
 the arterial walls are distended to the slightest extent, and when during the movement of the pulse 
 (cardiac diastole) the tension is most rapid ( Traube, Weil), i. e., when the low systolic minimum, 
 tension of the arterial wall passes rapidly into the high maximum tension. This is especially the 
 case in insufficiency of the aortic valves, in which case the sounds in the arteries are audible over a 
 wide area. If the minimum tension of the arterial wall is relatively great, even during diastole, the 
 sounds in the arteries are greatly diminished. 
 
 In insufficiency of the aortic valves, characteristic sounds may be heard in the crural artery. 
 If pressure be exerted upon the artery, a double blowing murmur is heard ; the first one is due to a. 
 large mass of blood being propelled into the artery synchronously with the heart beat, the second to 
 the fact that a large quantity of blood flows back into the heart during diastole (Duroziez, 1S61). 
 If no pressure be exercised two sounds are heard, and these seem to be due to a wave propagated 
 into the arteries by the auricles and ventricles respectively [Landois) — compare \ 73, Fig. 86, III. 
 In atheroma a double sound may sometimes be heard (§ 73, 2). 
 
 98. VENOUS MURMURS.— I. Bruit de Diable— This sound is. 
 heard above the clavicles, in the furrow between the two heads of the sterno- 
 mastoid, most frequently on the right side, and in 40 per cent, of all persons 
 examined. It is either a continuous or a rhythmical murmur, occurring during the 
 diastole of the heart or during inspiration ; it has a whistling or rushing character,, 
 or even a musical quality, and arises within the bulb of the common jugular vein- 
 
THE VENOUS PULSE. 165 
 
 When this sound is heard without pressure being exerted by the stethoscope, it 
 is a pathological phenomenon. If, however, pressure be exerted, and if, at the 
 same time, the person examined turns his head to the opposite side, a similar sound 
 is heard in nearly all cases (Weil). The pathological bruit de diable occurs 
 especially in anaemic persons, in lead poisoning, syphilitic and scrofulous persons, 
 sometimes in young persons, and less frequently in elderly people. Sometimes a 
 thrill of the vascular wall may be felt. 
 
 Causes. — It is due to the vibration of the blood flowing in from the relatively 
 narrow part of the common jugular vein into the wide bulbous portion of the 
 vessel, and seems to occur chiefly when the walls of a thin part of the vein lie 
 close to each other, so that the current must purl through it. It is clear that pres- 
 sure from without, or lateral pressure, as by turning the head to the opposite side, 
 must favor its occurrence. Its intensity will be increased when the velocity of the 
 stream is increased, hence inspiration and the diastolic action of the heart (both 
 of which assist the venous current) increase it. The erect attitude acts in a similar 
 manner. A similar bruit is sometimes, though rarely, heard in the subclavian, 
 axillary, thyroid (scrofula), facial, innominate and crural veins and superior cava. 
 
 II. Regurgitant Murmurs. — On making a sudden effort, a murmur maybe heard in the crural 
 vein during expiration, which is caused by a centrifugal current of blood, owing to the incompetence 
 or absence of the valves in this region. If the valves at the jugular bulb are not tight, there may 
 be a bruit with expiration {expiratory jugular vein bruit — ffamernjk), or during the cardiac systole 
 (systolic jugular vein bruit — v. Bamberger). 
 
 III. Valvular Sounds in Veins. — When the tricuspid valve is incompetent, during the ventri- 
 cular systole a large volume of blood is propelled backward into the venee cavse. The venous valves 
 are closed suddenly thereby and a sound produced. This occurs at the bulb or dilatation on the 
 jugular vein (v. Bamberger), and in the crural vein at the groin (N. Freidreicli), i. e., only as long 
 as the valves are competent. Forced expiration may cause a valvular sound in the crural vein. No 
 sound is heard in the veins under perfectly normal circumstances. 
 
 99. THE VENOUS PULSE— PHLEBOGRAM. -Methods.— A tracing of the move- 
 ments of a vein, taken with a lightly-weighted sphygmograph, has a characteristic form, and is 
 called a phlebogram (Fig. 115). In order to interpret the various events of the phlebogram it is 
 most important to record simultaneously the event that takes place in the heart. The auricular 
 contraction (compare Fig. 41 ) is synchronous with a b ; be, with the ventricular systole, during which 
 time the first sound occurs, while a b is a presystolic movement. The carotid pulse coincides nearly 
 with the apex of the cardiogram, i. e., almost simultaneously with the descending limb of the phle- 
 bogram (Jiiegel). 
 
 Occasionally in healthy individuals a pulsatile movement, synchronous with the 
 action of the heart, may be observed in the common jugular vein. It is either 
 confined to the lower part of the vein, the so-called bulb, or extends further up 
 along the trunk of the vein. In the latter case, the valves above the bulb are 
 insufficient, which is by no means rare, even in health. The wave motion passes 
 from below upward, and is most obvious when the person is in the passive hori- 
 zontal position, and it is more frequent on the right side, because the right vein 
 lies nearer the heart than the left. 
 
 The venous pulse resembles very closely the tracing of the cardiac impulse 
 (Landois). Compare Fig. 115, 1, with Fig. 32. 
 
 It is obvious that, as the jugular vein is in direct communication with the right 
 auricle, and as the pressure within it is low, the systole of the right auricle must 
 cause a positive wave to be propagated toward the peripheral end of the jugular 
 vein. Fig. 115, 9 and 10, are venous pulse tracings of a healthy person with 
 insufficiency of the valves of the jugular vein. In these curves, the part a, b 
 corresponds to the contraction of the auricle. Occasionally this part consists of 
 two elevations, corresponding to the contraction of the atrium and auricle 
 respectively. As the blood in the right auricle receives an impulse from the 
 sudden tension of the triscupid valve synchronous with the systole of the right 
 ventricle, there is a positive wave in the jugular vein in Fig. 115, 9 and 10, indi- 
 cated by b, c. Lastly, the sudden closure of the pulmonary valves may even be 
 
166 
 
 THE VENOUS PULSE. 
 
 indicated (<?). As the aorta lies in direct relation with the pulmonary artery, the 
 sudden closure of its valves may also be indicated (Fig. 115, 9, at d). During 
 the diastole of the auricle and ventricle, blood flows into the heart, so that the 
 vein partly collapses and the lever of the recording instrument descends (Riegel, 
 Fran(ois-Franck) . 
 
 Sinus and Retinal Pulse. — The blood in the sinuses of the brain also undergoes a pulsatile 
 movement, owing to the fact that during cardiac diastole much blood flows into the veins (Mosso). 
 Under favorable circumstances, this movement may be propagated into the veins of the retina, con- 
 stituting the venous retinal pulse of the older observers (Helfreich). 
 
 Jugular Vein Pulse. — The venous pulse in the jugular vein is far better marked in insufficiency 
 of the tricuspid valve, and the vein may pulsate violently, but if its valves be perfect the pulse is not 
 propagated along the vein, so that a pulse in the jugular vein is not necessarily a sign of insuffi- 
 ciency of the tricuspid valve, but only of insufficiency of the valve of the jugular vein {Friedreich). 
 
 Liver Pulse. — The ventricular systole is propagated into the valveless inferior vena cava, and 
 
 Fig. 115. 
 
 Various forms of venous pulses, chiefly after Friedreich' — i-S from insufficiency of the tricuspid ; 9 and 10. pulse ot 
 the jugular vein of a healthy person. In all the curves, a, b = contraction of the right auricle ; 6, c, of the right 
 ventricle ; d, closure of the aortic valves ; e, closure of the pulmonary valves ; e,f, diastole of the right ventricle. 
 
 causes the liver pulse. With each systole blood passes into the hepatic veins, so that the liver 
 undergoes a systolic swelling and injection. 
 
 Fig. 115, 2-8, are curves of the pulse in the common jugular vein (after Friedreich). Although 
 at first sight the curves appear to be very different, they all agree in this, that the various events 
 occurring in the heart during a cardiac revolution are indicated more or less completely. In all 
 the curves, a,b = auricular contraction. The auricle, when it contracts, excites a positive wave in 
 the veins (Gendrin (1843), Marey, Friedreich). The elevation, b, c, is caused by the large blood 
 wave produced in the veins, owing to the emptying of the ventricle. It is always, greater, of 
 course, in insufficiency of the tricuspid valves than under normal circumstances (Fig. 115, 9 and 
 10). In the latter case, the closure of the tricuspid valve causes only a slight wave motion in the 
 auricle. The apex, c, of this wave may be higher or lower, according to the tension in the vein 
 and the pressure exerted by the sphygmograph. As a general rule, at least one notch (4, 5, 6, e) 
 follows the apex, due to the prompt closure of the valves of the pulmonary artery. The closure of 
 the closely adjacent aortic valves may cause a small secondary wave near to e (as in 1 and 2, d). 
 The curve falls toward f, corresponding to the diastole of the heart. 
 
 A well-marked venous pulse occurs when the right auricle is greatly congested, as in cases of 
 insufficiency of the mitral valve or stenosis of the same orifice. In rare cases, in addition to the 
 
PLETHYSMOGRAPHY. 167 
 
 pulse in the common jugular vein, the external jugular, the facial, thyroid, external thoracic veins, 
 or even the veins of the upper and lower extremities may pulsate. 
 
 A similar pulsation must occur in the pulmonary veins in mitral insufficiency, but, of course, the 
 result is not visible. 
 
 On rare occasions, a pulse occurs in the veins on the back of the hand and foot, owing to the 
 arterial pulse being propagated through the capillaries into the veins. This may occur under 
 normal circumstances, when the peripheral ends of the arteries become dilated and relaxed 
 [Quincke), or when the blood pressure within these vessels rises rapidly and falls as suddenly, as in 
 insufficiency of the aortic valves. 
 
 In progressive effusion into the pericardium, at first the carotid pulse becomes smaller and the 
 venous pulse larger ; beyond a certain pressure, the latter ceases [Siegel). 
 
 100. DISTRIBUTION OF THE BLOOD.— Methods.— The methods adopted do not 
 give exact results. J. Ranke ligatured the parts during life, removed them, and investigated the 
 amount of blood while the tissues were still warm. 
 
 In the rabbit, one-fourth of the total amount of the blood is found in each of 
 the following : a, in the passive muscles ; b, in the liver ; c, in the organs of the 
 circulation (heart and great vessels) ; d, in all other parts together {J. Ranke). 
 
 Influencing Conditions. — The amount of blood is influenced by — (i ) the anatomical distribution 
 (vascularity or the reverse) of the vessels as a whole ; (2) the diameter of the vessels, which depends 
 upon physiological causes — (a) on the blood pressure within the vessels; (b) on the condition of 
 the vasomotor or vaso-dilator nerves ; (c) on the condition of the tissues themselves, e.g., the vessels 
 of the intestine during absorption ; by the vessels of muscle during muscular contraction ; of 
 vessels in inflamed parts. 
 
 Activity of an Organ. — The most important factor, however, is the state of 
 activity of the organ itself ; hence, the saying, " ubi irritatio, ibi affluxus." We 
 may instance the congestion of the salivary glands and the gastric mucous mem- 
 brane during digestion, and the increased vascularity of muscles during contrac- 
 tion. As the activity of organs varies at different times, the amount of blood in 
 the part or organ goes hand in hand with the variations in its state of activity (_/". 
 Ranke). When some organs are congested others are at rest ; during digestion, 
 there is muscular relaxation and less mental activity ; violent muscular exertion 
 retardsdigestion — during great congestion of the cutaneous vessels the activity of 
 the kidneys diminishes. Many organs (heart, muscles of respiration, certain 
 nerve centres) seem always to be in a nearly uniform state of activity and vascu- 
 larity. 
 
 During the activity of an organ, the amount of blood in it may be increased 30 
 per cent. , nay even 47 per cent. The motor organs of young muscular persons 
 are relatively more vascular than those of old and feeble persons (_/. Ranke). 
 
 During a condition of mental activity, the carotid is dilated, the dicrotic wave in the carotid curve is 
 increased (the radial shows the opposite condition), and the pulse is increased in frequency [Gley). 
 
 In the condition of increased activity, a more rapid renewal "of the blood seems 
 to occur ; after muscular exertion the duration of the circulation diminishes 
 ( Vierordt). 
 
 Age. — The development of the heart and large vessels determines a different distribution of the 
 blood in the child from that which obtains in the adult. The heart is relatively small from infancy 
 up to puberty, the vessels are relatively large ; while after puberty the heart is large, and the vessels 
 are relatively smaller. Hence, it follows that the blood pressure in the arteries of the systemic cir- 
 culation must be lower in the child than in the adult. The pulmonary artery is relatively wide in 
 the child, while the aorta is relatively small ; after puberty both vessels have nearly the same size. 
 Hence, it follows that the blood pressure in the pulmonary vessels of the child is relatively higher 
 than that in the adult {Beneke). 
 
 101. PLETHYSMOGRAPHY.— Plethysmograph.— In order to esti- 
 mate and register the amount of blood in a limb, Mosso devised an instrument 
 (Fig. 116), which he termed a Plethysmograph. It is constructed on the same 
 principle as the less perfect apparatus of Chelius and Fick. 
 
 It consists of a long cylindrical glass vessel, G, suited to accommodate a limb. The opening 
 through which the limb is introduced is closed with caoutchouc, and the vessel is filled with water. 
 
168 
 
 TRANSFUSION OF BLOOD. 
 
 There is an opening in the side of the vessel in which a manometer tube, filled to a certain height 
 with water, is fixed. As the arm is enlarged owing to the increased supply of arterial blood passing 
 into it at each pulse beat, of course, the water column in the manometer is raised. Fick placed a 
 float upon the surface of the water, and thus enabled the variations in the volume of the fluid to be 
 inscribed on a revolving cylinder. The curve obtained resembled the pulse curve ; it was even 
 dicrotic. In Fig. 116 the movement of the fluid is represented as conveyed to a Marey's tambour, 
 T, similar to the recording apparatus employed in Brondgeest's Pansphygmograph (Figs. 40, 72). 
 
 Results. — From the curve obtained we learn that — (1) the pulsatile variations 
 in the volume are similar to the pulse curve. As the venous current is regarded as 
 uniform in the passive limb, every increase of the volume curve indicates a greater 
 velocity of the arterial current toward the periphery, and vice versa {Fick). (2) 
 The respiratory undulations correspond to similar variations in the blood pressure 
 tracing (§ 85,/). Vigorous respiration and cessation of the respiration cause a 
 diminution of the volume. The limb swells during straining (v. BascK) and 
 coughing, but diminishes during sighing. (3) Certain periodic undulations occur, 
 due to the regular periodic contractions of the small arteries. (4) Other undula- 
 tions, due to various accidental causes, affect the blood pressure : changes of the 
 position of a limb acting hydrostatically, and dilatation or contraction of the 
 vessels in other vascular regions. (5) Movement of the muscles of the limb under 
 observation causes diminution of volume (experiment of Fr. Glisson, 1677) ; as 
 the venous current is accelerated, the musculature is also very slightly diminished in 
 
 Fig. 116. 
 
 Mosso's Plethysmograph. G, glass vessel for holding a limb ; F, flask for varying the water pressure in G; 
 
 T, recording apparatus. 
 
 volume, even when the intra-muscular vessels are dilated. (6) Mental exercise 
 causes a diminution in the volume of the limb, and so does sleep (Mosso). Music 
 influences the blood pressure in dogs, the pressure rising or fajling under different 
 conditions. The stimulation of the auditory nerve is transmitted to the medulla 
 oblongata, where it acts so as to cause acceleration of the action of the heart 
 {Dogiel). Compression of the afferent artery causes a decrease, and compression 
 of the vein an increase in the volume of the limb {Mosso). 
 
 102. TRANSFUSION OF BLOOD.— Transfusion is the introduction of 
 blood from one animal into the vascular system of another animal. 
 
 Historical. — The first indication of direct transfusion from blood vessel to blood vessel dates 
 from the time of Cardanus, in 1556. After the discovery of the circulation in England, J. Potter 
 (1638) evolved the idea of the transfusion of blood. Numerous experiments were made on ani. 
 mals. New blood was transfused, in order to restore life in animals that had been bled. Boyle 
 and Lower conducted these and other experiments. The. blood of the same species, as well as the 
 blood of other species, was employed. The first case of transfusion on man was performed by 
 Jean Denis, in Paris (1667), lamb's blood being used. At the present time, when transfusion is 
 practiced on man, only human blood is used. 
 
 (a) The red corpuscles are the most important elements in connection with 
 the restorative powers of the blood. They seem to preserve their functions even 
 
TRANSFUSION OF BLOOD. 169 
 
 in blood which has been defibrinated outside the body {Prevost and Dumas, 1821). 
 The effect of various reagents upon them has already been noticed (§ 4, A). 
 
 (d) With regard to the gases of the blood corpuscles, oxygenated (arterial) 
 blood never acts injuriously ; but venous blood overcharged with carbonic acid 
 ought only to be transfused when the respiration is sufficient to oxygenate the 
 blood as it passes through the pulmonary capillaries, whereby venous is transformed 
 into arterial blood. If the respiratory movements have ceased, or are imperfectly 
 performed, the blood becomes rapidly richer in carbonic acid, and in this condi- 
 tion reaches the heart ; thence it is propelled into the blood vessels of the medulla 
 oblongata, where it acts as a powerful stimulus of the respiratory centre, causing 
 dyspnoea, convulsions and death. 
 
 (V) The fibrin, or the substances from which it is formed (§ 29), do not seem 
 to play any part in connection with the restorative powers of the blood ; hence, 
 defibrinated blood performs all the functions of non-defibrinated blood within the 
 body {Panum, Landois). 
 
 id) The investigations of Worm Miiller showed that an excess of 83 per cent, 
 of blood might be transfused into the vascular system of an animal without pro- 
 ducing any injurious effects. Hence it follows that the vascular system has the 
 power of accommodating large quantities of blood within it. That the vascular 
 system can accommodate itself to a diminished amount of blood has been known 
 for a long time (§85, c). [It is very important to observe that the transfusion 
 of a large quantity of blood does not materially or permanently raise the blood 
 pressure.] 
 
 When Employed. — The transfusion of blood is used — (1) in acute anaemia 
 (§41, I), e.g., after copious hemorrhage. New blood from the same species of 
 animal is introduced directly into the vessels, to supply the place of the blood 
 lost by the hemorrhage. 
 
 (2) In cases of poisoning, where the blood has been rendered useless by being 
 mixed with a poisonous substance, and hence is unable to support life. In such 
 cases, remove a considerable quantity of the blood, and replace it by fresh blood. 
 Carbonic oxide is a poison of this kind {KUhne), and its effects on the body have 
 already been described (§ 16). A similar practice is indicated on poisoning with 
 ether, chloral, chloroform, opium, morphia, strychnine, cobra poison and such 
 substances as dissolve the blood corpuscles, e.g., potassic chlorate. 
 
 (3) Under certain pathological conditions, the blood may become so altered 
 in quality as to be unable to support life. The morphological elements of the 
 blood may be altered, and so may the relative proportion of its other constituents. 
 Among these conditions may be cited the pathological condition of uraemia, due, 
 it maybe, to the accumulation of urea or the products of its decomposition within 
 the blood [or to the retention of the potash and other urinary salts (Feltz and 
 Ritter)~\ ; accumulation of the biliary constituents in the blood (Chblaemia), and 
 great increase of the carbonic acid. All these three conditions, when very pro- 
 nounced, may cause death. In these cases, part of the impure blood maybe 
 replaced by normal human blood {Landois). 
 
 Among conditions where the morphological constituents of the blood are altered 
 qualitatively or quantitatively are : hydraemia (excessive amount of water in the 
 blood, §41, 1) ; oligocythemia (abnormal diminution of red corpuscles). When 
 these conditions are highly developed, more especially in pernicious anaemia (§ 10, 
 2), healthy blood may be substituted. Transfusion is not suited for persons 
 suffering from leukaemia (compare p. 33). 
 
 After Effects. — A quarter or half an hour after normal blood has been injected 
 into the blood vessels of a man, there is a greater or less febrile reaction, according 
 to the amount of blood transfused (Fever, § 220). 
 
 Operation. — The operative procedure to be adopted in the process of transfusion varies according 
 as defibrinated or non-defibrinated .blood is used. In order to defibrinate blood, some blood is 
 withdrawn from the vein of a healthy man in the ordinary way; it is collected in an open vessel 
 
170 TRANSFUSION OF BLOOD. 
 
 and whipped or beaten with a glass rod until all the fibrin is completely removed from it. It is then 
 filtered through an atlas filter, heated to the temperature of the body (by placing it in warm water), 
 and injected, by means of a syringe, into an artery opened for the purpose. A vein (e. g., basilic 
 or great saphenous) may be selected for the transfusion, in which case the blood is driven in in the 
 direction of the heart; if an artery is selected (radial or posterior tibial), the blood is injected 
 toward the periphery (//titer) or toward the heart (Landois, Schafer). 
 
 Dangers. — It is most important not to permit the entrance of air into the circulation, for if it be 
 introduced in sufficient quantity, it may cause death. When air enters the circulation it reaches the 
 right side of the heart, where, owing to the movement of the blood, it forms air bubbles and makes 
 a froth. The air .bubbles are pumped into the branches of the pulmonary artery, in which they be- 
 come impacted, arrest the pulmonary circulation, and rapidly cause death. 
 
 If non-defibrinated human blood is used, the blood may be passed directly from the arm of the 
 giver to the arm of the receiver by means of a flexible tube. The tube used must be filled with 
 normal saline solution to prevent the entrance of air. [J. Duncan collects the blood shed during 
 an operation in a 5 per cent, solution of sodic phosphate (Pavy), and injects the mixture, especially 
 where much blood has been lost previously.] 
 
 Peritoneal Transfusion. — Recently, the injection of defibrinated blood into the peritoneal 
 cavity has been recommended. The blood so injected is absorbed (Ponfick). Even after twenty 
 minutes the number of blood corpuscles in the blood of the recipient (rabbit) is increased, and the 
 number is greatest on the first or second day (Bbaozero and Golgi). The operation, -however, may 
 cause death, and one fatal case, owing to peritonitis, is recorded (Mosler). It is evident that this 
 method of transfusion is not applicable in cases where blood must be introduced into the circulation 
 as rapidly as possible (e. g., after severe hemorrhage or in certain cases of poisoning). [Blood has 
 been injected into the subcutaneous cellular tissue of the abdomen in cases of great debility]. 
 
 Heterogeneous Blood. — The blood of animals ought never to be transfused into the blood ves- 
 sels of man. Some surgeons have transfused blood directly from the carotid of a lamb into the 
 human subject. It is to be remembered, however, that the blood corpuscles of the sheep are rapidly 
 dissolved by human blood, so that the active constituents of the blood are rendered useless ( Lan- 
 dois). As a general rule, the blood serum of some mammals dissolves the blood corpuscles of other 
 mammals ($ 5, 5). 
 
 Solution of the Blood Corpuscles. — The serum of dog's blood is a powerful solvent, while 
 that of the blood of the horse and rabbit dissolves corpuscles relatively slowly. The blood corpus- 
 cles of mammals vary very greatly with reference to their power to resist the solvent action of the 
 serum of other animals. The red blood corpuscles of rabbit's blood are rapidly dissolved by the 
 blood serum of other animals, whilst those of the cat and dog resist the solvent action much longer. 
 Solution of the corpuscles occurs in defibrinated as well as in ordinary blood. When the blood of 
 a rabbit or lamb is injected into the blood vessels of a dog, they are dissolved in a few minutes. If 
 blood be withdrawn by pricking the skin with a needle, the partially dissolved corpuscles may be 
 detected. 
 
 Liberation of Hemoglobin and Hemoglobinuria. — As a result of the solution of the col- 
 ored corpuscles, the blood plasma is reddened by the liberated haemoglobin. Part of the dissolved 
 material may be used up in the body of the recipient, some of it for the formation of bile, but if 
 the solution of the corpuscles has been extensive, the haemoglobin is excreted in the urine (hsemo- 
 globinuria) in less amount in the intestine, the bronchi, and the serous cavities (Panum). Bloody 
 urine has been observed in man after the injection of 100 grammes of lamb's blood. Even some 
 of the recipient's blood corpuscles are dissolved by the serum of the transfused blood, c. g., on 
 transfusing dog's blood into man. In the rabbit, whose corpuscles are readily dissolved, the trans- 
 fusion of the blood serum of the dog, man, pig, sheep, or cat produces serious symptoms, and even 
 death. The dog, whose corpuscles are more resistant, bears transfusion of other kinds of blood 
 well. 
 
 Dangers. — When foreign or heterogeneous blood (z. e., blood from a different species) is trans- 
 fused, two phenomena, which may be dangerous to life, occur : — 
 
 (1) Before the c:rpuscles are dissolved they usually run together and form sticky masses, consist- 
 ing of 10 or 12 corpuscles, which are apt to occlude capillaries. After a time they give up their 
 haemoglobin, leaving the stroma, which yields a sticky, fibrin- like mass that may occlude fine vessels 
 
 («30- 
 
 (2) The presence of a • large ^quantity- of 'dissolved-haemoglobin may cause extensive coagulation 
 within the bloodvessels. The injection of dissolved haemoglobin causes extensive coagulations 
 (A T aunyn and Francken). 
 
 The coagulation occurs usually in the venous system and in the larger vessels, and may cause 
 death either suddenly or after a considerable time. 
 
 Dissolved haemoglobin seems greatly to increase the activity of the fibrin ferment (§ 30), perhaps 
 by accelerating the decomposition of the colorless corpuscles. Haemoglobin exposed to the air 
 gradually loses this property ; and the fibrin ferment, when in contact with haemoglobin, is either 
 destroyed or rendered less active (Sachssendahl). 
 
 Vascular Symptoms. — As a result of the above-named causes of occlusion of the vessels, there 
 are often signs of the circulation being impeded in various organs. In man, after transfusion of 
 
TRANSFUSION OF KLOOD. 171 
 
 lamb's blood, the skin is bluish red, in consequence of the stagnation of blood in the cutaneous 
 vessels. Difficulty of breathing occurs from obstruction in the capillaries of the lung ; while there 
 may be rupture of small bronchial vessels, causing sanguineous expectoration. The dyspnoea may 
 increase, especially when the circulation through the medulla oblongata — the seat of the respiratory 
 centre — is interfered with. In the digestive tract, for the same reason, increased peristalsis, evacua- 
 tion of the contents of the rectum, vomiting, and abdominal pain may occur. These phenomena 
 are explained by the fact that disturbances of the circulation in the intestinal vessels cause increased 
 peristaltic movements. Degeneration of the parenchyma of the kidney occurs as a result of the 
 occlusion of some of the renal vessels. The uriniferous tubules become plugged with cylinders of 
 coagulated albumin (Ponfick). Owing to the occlusion of numerous small muscular branches the 
 muscles may become stiff, or coagulation of their myosin may occur. Other symptoms, referable to 
 the nervous system, the sense organs and heart, are all due to the interference with the circulation 
 through them. An important symptom is the occurrence of a considerable amount of fever half an 
 hour or so after the transfusion of heterogeneous blood. When many vessels are occluded, rupture 
 of some small blood vessels may take place. This explains the occurrence of slight yet persistent 
 hemorrhages, which occur on the free surfaces of the mucous and serous membranes, and in the 
 parenchyma of organs, as well as in wounds. The blood coagulates with difficulty, and imper- 
 fectly. 
 
 Transfusion of other Fluids. — Other substances have been transfused. Normal Saline So- 
 lution (0.6 per cent. NaCl) aids the circulation in a purely mechanical way (Goltz), and it even 
 excites the circulation (Kronecker, Sander, Ott). In severe aaamia this fluid cannot'inaintain life 
 (Eulenburg and Landois). The injection of Peptone, even in moderate amount, is dangerous to 
 life, as it causes paralysis of the vessels. The injection of Milk is accompanied with danger; fever 
 occurs after the injection, and the milk globules cause the occlusion of many vessels, producing sub- 
 sequent degenerations. Fat may appear in the urine, and there may be fatty infiltration of the 
 urinary tubules. The urine contains sugar and albumin, the liver cells often contain fatty granules, 
 and the weight of the body diminishes. If too large a quantity of milk be transfused, death occurs. 
 When unboiled milk is injected, numerous bacteria are developed in the blood (Schafer). 
 
THE BLOOD GLANDS 
 
 103. — I. THE SPLEEN. — Structure. — The spleen is covered by the peritoneum, except at 
 the hilus. Under this serous covering there is a tough, thick, elastic, fibrous capsule, which 
 closely invests the organ and gives a covering to the vessels which enter or leave it at the hilus, so 
 that fibrous tissue is carried into the organ along the course of the vessels. [The capsule cannot 
 be separated without tearing the splenic pulp.] Numerous trabecule pass into the spleen from 
 the deep surface of the capsule. These trabeculse branch and anastomose so as to produce a net- 
 work of sustentacular tissue, which is continuous with the connective tissue, prolonged inward and 
 surrounding the blood vessels (Fig. 117). Thus, the connective tissue in the spleen, as in other 
 viscera, is continuous throughout the organ. In this way an irregular dense network is formed, 
 corhparable to the meshes of a bath sponge. [This network is easily demonstrated by washing out 
 the pulp lying in its meshes by means of a stream of water, when a beautiful, soft, semi-elastic net- 
 work or framework of rounded and flattened threads is obtained.] 
 
 Fig. 117. 
 
 wemmsm^. 
 
 M' 'li'f/i/!^^^r~^~- 
 
 Trabecular of the spleen ot a cat with the splenic pulp washed out — a, 
 trabecular ; b, vein. 
 
 Fig. 118. 
 
 Spleen of a cat injected 
 with gelatine, showing 
 the adenoid reticulum. 
 
 The Capsule is composed of interlacing bundles of connective tissue mixed with numerous fine 
 fibres of elastic tissue and some non-striped muscular fibres. 
 
 Reticulum. — Within the meshes of the trabecular framework there is disposed a very delicate 
 network or reticulum of adenoid tissue {Billroth), which, with the other colored elements that fill 
 •up the meshes, constitute the splenic pulp (Fig. 118). The reticulum is continuous with the fibres 
 of the trabeculse. [If a fine section of the spleen be "pencilled" in water, so as to remove the 
 cellular elements, the preparation presents much the same characters as a section of a lymph gland 
 similarly treated, viz., a very fine network of adenoid tissue, continuous with, and surrounding the 
 walls of, the blood vessels. The spaces of this tissue are filled with lymph and blood corpuscles 
 {His).1 ' 
 
 The Pulp is a dark, reddish-colored semi-fluid material, which may be squeezed or washed out 
 of the meshes in which it lies. It contains a large number of colored blood corpuscles, and becomes 
 brighter when it is exposed to the action of the oxygen of the air. 
 
 Blood Vessels and Malpighian Corpuscles. — The large splenic artery splits up into several 
 branches before it enters the spleen, and it is accompanied in its course by the vein. Both vessels 
 and their branches are enclosed in a fibrous sheath, which becomes continuous with the trabeculse. 
 The smaller branches of the artery gradually lose this fibrous investment, and each one ultimately 
 divides into a group or pencil of arterioles (penicilli) which do not anastomose with each other. 
 [Thus each branch is terminal — a condition which is of great importance in connection with the 
 pathology of embolism or infarction of the vessels of the spleen.] At the points of division of the 
 branches of the artery, or scattered along their course, are small oval or globular masses of adenoid 
 tissue, about the size of a small millet seed (^ to ^ inch in diameter)— the Malpighian 
 corpuscles. [These bodies are visible to the naked eye as small, round or oval white structures, 
 about the size of a millet seed, in a section of a fresh spleen.] They are very numerous — [7000 
 
 172 
 
BLOOD VESSELS OF THE SPLEEN. 173 
 
 in man (Sappey)] — and are readily detected in the dark reddish pulp. We must be careful not to 
 mistake sections of the trabecular for them. These corpuscles consist of adenoid tissue, whose 
 meshes are loaded with lymph corpuscles, and they present exactly the same structure as the 
 solitary follicles of the intestine (compare Lymphatic Glands, \ 197). 
 
 [They are just small lymphatic accumulations around the arteries — peri-arterial masses of 
 adenoid tissue similar to those masses that occur in a slightly different form in other organs, c. g., 
 the lungs. In a section of the spleen the artery may pass through the centre of the mass or 
 through one side of it, and in some cases the tissue is collected unequally on opposite sides of the 
 vessel, so that it is lob-sided. They are not surrounded by any special envelope. In some animals 
 the lymphatic tissue is continued for some distance along the small arteries, so that to some extent it 
 resembles a perivascular sheath of adenoid tissue (W. Miiller, Schweigger-Seidel). In a well- 
 injected spleen, a few fine capillaries are to be found within these corpuscles (Sanders). The capil- 
 laries distributed in the substance of the Malpighian corpuscle (Fig. no) form a network, and 
 ultimately pour their blood into the spaces in the pulp. According to Robin and Legros, these 
 vessels are comparable to the vasa-vasorum of other blood vessels. According to Cadiat, the cor- 
 puscles are separated from the splenic pulp by a lymphatic sinus, which is traversed by efferent 
 capillaries passing to the pulp (Fig. 119).] 
 
 Connection of Arteries and Veins. — It is very difficult to determine what is the exact mode 
 of termination of the arteries within the spleen, more especially as it is extremely difficult to inject 
 the blood vessels of the spleen. According to Stieda, W. Miiller, Peremeschko and Klein, the 
 
 Fig. 119. 
 
 Malpighian corpuscle ot the spleen of a cat injected, a, artery around which the corpuscle is placed; b, meshes 
 of the pulp injected ; c, the artery of the corpuscle ramifying in the lymphatic tissue composing it. The clear 
 space around the corpuscle is the lymphatic sinus. 
 
 fine " capillary arteries " formed by the division of the small arteries do not open directly into the 
 capillary veins, but the connection between the arteries and veins is by means of the " intermediary 
 intercellular spaces" of the reticulum of the spleen; so that, according to this view, there is no 
 continuous channel lined throughout by epithelium connecting these vessels one with another. 
 Thus, the blood of the spleen flows into the spaces of the adenoid reticulum, just as the lymph 
 stream flows through the spaces in a lymph gland. According to Billroth and Kolliker, a closed 
 blood channel actually does exist between the capillary arteries and the veins, consisting of dilated 
 spaces (similar to those of erectile tissue). These intermediary spaces are said to be completely 
 lined by spindle-shaped epithelium, which abuts externally on the reticulum of the pulp. [Accord- 
 ing to Frey, owing to the walls of the terminal vessels being incomplete — there being clefts or spaces 
 between the cells composing them — the blood passes freely into spaces of the adenoid tissue of the 
 pulp " in the same way as the water of a river finds its way among the pebbles of its bed," these 
 " intermediary passages " being bounded directly by the cells and fibres of the network of the 
 pulp. From these passages the venous radicles arise. At first, their walls are imperfect and crib- 
 riform, and they often present peculiar transverse markings, due to the circular disposition of the 
 elastic fibres of the reticulum. The small veins have at first a different course from the arteries. 
 They anastomose freely, but they soon become ensheathed, and accompany the arteries in their 
 course.] 
 
 Elements of the Pulp. — The morphological elements are very various — (1) Lymph corpuscles 
 of various sizes, sometimes partly swollen, and at other times with granular contents, (2) Red 
 
174 FUNCTIONS OF THE SPLEEN. 
 
 blood corpuscles. (3) Transition forms between 1 and 2 [although this is denied by some observers 
 (§ 7, C)]. (4) Cells containing red blood corpuscles and pigment granules. [These cells exhibit 
 amoeboid movements.] (Compare \ 8.) 
 
 [The Lymphatics undoubtedly arise within the spleen. The lymphatics which leave the spleen 
 are not numerous {Kolliker). There are two systems— a superficial, capsular and trabecular system, 
 and a perivascular set. The superficial lymphatics in the capsule are rather more numerous. 
 Some of them seem to communicate with the lymphatics within the organ ( Tomsa, Kolliker). In 
 the horse's spleen they communicate with the lymphatics in the trabeculse and with the perivascular 
 lymphatics. The exact mode of origin of the perivascular system is unknown, but in part, at 
 least, it begins in the spaces of the adenoid tissue of the Malpighian corpuscles and perivascular 
 adenoid tissue, and runs along the arteries toward the hilus. There seem to be no afferent lym- 
 phatics in the spleen, such as exist in a lymphatic gland.] 
 
 The Nerves of the spleen are composed, for the most part, of non-medullated nerve fibres, and 
 run along with the artery. Their exact mode of termination is unknown, but they probably go to 
 the blood vessels and to the muscular tissue in the capsule and trabeculse. [They are well seen in 
 the spleen of the ox, and in their course very small ganglia, placed wide apart, have been- found" by 
 Remak and W. Stirling.] 
 
 Chemical Composition. — Several of the more highly oxidized stages of albuminous bodies 
 exist in the spleen. Besides the ordinary constituents of the blood, there exist leucin, tyrosin, 
 xanthin, hypoxanthin, also lactic, butyric, acetic, formic, succinic and uric acids, and, perhaps, 
 glycero-phosphoric acid (Salkowski) ; cholesterin, a glutin-like body, inosite, a pigment containing 
 iron, and even free iron oxide (Nasse). The ash is rich in phosphoric acid and iron — poor in 
 chlorine compounds. The splenic juice is alkaline in reaction; the specific gravity of the spleen == 
 1059-1066. [The watery extract of the spleen contains a proteid combined with iron.] 
 
 The Functions of the spleen are obscure, but we know some facts on which 
 to form a theory. [The spleen differs from other organs in that no very apparent 
 effect is produced by it, so that we must determine its uses in the economy from 
 a consideration of such facts as the following: (1) The effects of its removal or 
 extirpation. (2) The changes which the blood undergoes as it passes through it. 
 (3) Its chemical composition. (4) The results of experiments upon it. (5) The 
 effects of diseases.] 
 
 (1) Extirpation. — The spleen may be removed from an animal — old or young 
 — without the organism suffering any very obvious change {Galen"). The human 
 spleen has been successfully removed by Koberle, Pian, Zacaralla (1849), Credi 
 and others. As a result (compensatory ?), the lymphatic glands enlarge, but not 
 constantly, while the blood-forming activity of the red marrow of bone is in- 
 creased. Small brownish-red patches were observed in the intestines of frogs 
 after extirpation of the spleen. These new formations are regarded by some 
 observers as compensatory organs. Tizzoni asserts that new splenic structures are 
 formed in the omentum (horse, dog) after the destruction of the parenchyma and 
 blood vessels of the spleen. The spleen is absent extremely seldom (Meinhard, 
 Koch and Wachsmuth). 
 
 [The weight of the animal (dog) diminishes after the operation, but afterward increases. The 
 number of red blood corpuscles is lessened, reaching its minimum about the 150th to the 200th 
 day, while that of the colorless corpuscles is greater. The lymphatic glands (especially the internal, 
 and those in the neck, mesentery and groin) enlarge, while, on section, the cortical substance of 
 these structures is redder, owing to the great number of red corpuscles, many nucleated ( Gibson), 
 in the lymph spaces. The marrow of all the long bones (those of the foot excepted) becomes very 
 red and soft, with the characters of embryonic bone marrow. Such animals withstand hemorrhage 
 (to ]^ of the total amount of blood) without any specially bad results ( Tizzoni, Winogradow). 
 Schindeler observed that animals, after extirpation of the spleen, became very ravenous.] 
 
 Schiff stated, that after extirpation of the spleen, the pancreatic juice failed to digest proteids. 
 The evidence in support of this statement is unsatisfactory, and Mosler affirms that this operation 
 has no effect either on gastric or pancreatic digestion. Heidenhain also found a similar negative 
 result. The operation ought to be performed on young animals, as old animals often succumb to it. 
 
 [Regeneration. — After entire removal of the spleen, nodules of splenic tissue are reproduced 
 (fox), while new adenoid tissue is formed in the lymphatic glands and in Peyer's patches, the paren- 
 chyma of the former coming to resemble splenic tissue ( Tizzoni, Eternod).~\ 
 
 (2) According to Gerlach and Funke, the spleen is a blood-forming gland. 
 As already mentioned, the blood of the splenic vein contains far more colorless 
 corpuscles than the blood of the splenic artery (p. 31). Many of these corpus- 
 
CONTRACTION OF THE SPLEEN. 175 
 
 cles undergo fatty degeneration, and disappear in the blood stream ( Virchow). 
 That colorless blood corpuscles are formed within the spleen seems to be proved 
 by the enormous number of these corpuscles which are found in the blood 
 in cases of hyperplasia of the spleen or leukaemia {Bennett (1852), Virchow). 
 Bizzozero and Salvioli found that several days after severe hemorrhage, the ■ 
 spleen became enlarged, and its parenchyma contained numerous red nucleated 
 haematoblasts. 
 
 According to Schiff, extirpation of the spleen has no effect, either upon the absolute or relative 
 number of colored or colorless corpuscles. [According to Picard and Malassez, there is a tempor- 
 ary decrease in the number of the red corpuscles and their haemoglobin, and Gibson also finds a 
 primary decrease in the red and an increase in the number of the white corpuscles.] 
 
 (3) Other observers {Kolliker and Ecker) regard the spleen as an organ in 
 which colored blood corpuscles are destroyed, and they consider the large 
 protoplasmic cells containing, pigment. granules as a proof of this (p. 28). Ac- 
 cording to the observations of von Kusnetzow, these structures are merely lymph 
 corpuscles, which, in virtue of their amoeboid movements, have entangled colored 
 blood corpuscles. [Such corpuscles exhibit similar properties when placed upon 
 a warm stage.] Similar cells occur in extravasations of blood {Virchow). The 
 colored blood corpuscles within the lymph cells gradually become disintegrated, 
 and give rise to the production of granules of haematin and other derivatives of 
 haemoglobin. Hence, the spleen contains more iron than corresponds to the 
 amount of blood present in it. When we consider that the spleen contains a 
 large number of extractives derived from the decomposition of proteids, it is very 
 probable that colored blood corpuscles are destroyed in the spleen. Further, the 
 juice of the spleen contains salts similar to those that occur in the red blood cor- 
 puscles. 
 
 The blood from the spleen is said to have undergone other changes, but the following statement 
 must be accepted with caution : The blood of the splenic vein contains more water and fibrin ; its 
 red blood corpuscles are smaller, brighter, less flattened, more resistant, and do not form rouleaux; 
 its haemoglobin crystallizes more easily, and there is a large proportion of O during digestion. 
 
 [The spleen has very direct relations to the blood ; in it colored blood cor- 
 puscles undergo disintegration, it produces colorless corpuscles, and it is said to 
 transform white corpuscles into red {Credi Gibson).'] 
 
 (4) Contraction. — In virtue of the plain muscular fibres in its capsule and 
 trabeculse, the spleen undergoes variations in its volume {Kolliker). Stimulation 
 of the spleen {Rud. Wagner, 1849) or its nerves, by cold, electricity, quinine, 
 eucalyptus, ergot of rye, and other " splenic reagents " {Mosler), causes it to 
 contract, whereby it becomes paler, and its surface may even appear granular. 
 After a meal, the spleen increases in size, and it is usually largest about five hours 
 after digestion has begun, i. e., at a time when the digestive organs have almost 
 finished their work, and have again become less vascular. After a time it regains 
 its original volume. For this reason the spleen was formerly regarded as an ap- 
 paratus for regulating the amount of blood in the digestive organs. [The conges- 
 tion of the spleen after a meal is more probably related to the formation of new 
 colorless corpuscles than to the destruction of red corpuscles. It may be, however, 
 that some of the products of digestion are partially acted upon in the spleen, and 
 undergo further change in the liver.] There is a relation between the size of the 
 spleen and that of the liver, for it is found that when the spleen contracts — e. g., 
 by stimulation of its nerves — the liver becomes enlarged, as if it were injected 
 with more blood than usual {Drosdow and Botschetschkarow). 
 
 [Oncograph. — Botkin, and more recently Roy, have studied various condi- 
 tions which affect the size of the spleen. Roy's observations are most important. 
 He enclosed the spleen of a living animal (dog) in a box with rigid walls, and 
 filled with oil, after the manner of the plethysmograph (§ 101, 276). Any varia- 
 tions in the size of the organ caused a variation in the amount of oil within the 
 
176 INFLUENCE OF NERVES ON THE SPLEEN. 
 
 box, and these variations were recorded. This instrument Roy termed an " onco- 
 graph " (pyxos, volume). The blood pressure was recorded at the same time. 
 
 Roy finds that the circulation through the spleen is peculiar, and that it is not 
 due to the blood pressure within the arteries, but is carried on chiefly by a rhyth- 
 ■ mical contraction of the muscular fibres of the capsule and trabecule. The spleen 
 undergoes very regular rhythmical contractions (systole) and dilatations (dias- 
 tole). This alternation of systole and diastole may last for hours, and the two 
 events together occupy about one minute (Fig. 120). Changes in the arterial 
 blood pressure have comparatively little influence on the volume of the spleen. 
 The rhythmical contractions, although modified, still go on after section of the 
 splenic nerves. This would seem to indicate that the spleen has an independent 
 (nervous) mechanism within itself, causing its movements.] 
 
 Influence of Nerves. — Section of the splenic nerves causes an increase in 
 the size of the spleen ; and when the nerves at the hilum are extirpated it swells 
 and assumes a deep purple color. The nerves have their centre in the medulla 
 
 Fig. 120. 
 
 Tracing ot a splenic curve, reduced one-halt, taken with the oncograph. The upper line with large waves is the 
 splenic curve, each ascent corresponds to an increase, and each descent to a diminution in the volume of the 
 spleen. The curve beneath is a blodd-pressure tracing from the carotid artery. The lowest line indicates the 
 time,_ the interruptions of the marker occurring every two seconds. The vertical lines, a and b, give the relative 
 positions of the lever point of the oncograph, and of the point of the recording style of the kymograph respect- 
 ively {Roy). 
 
 oblongata, and so far they are comparable to vasomotor nerves. Stimulation of 
 the medulla oblongata, either directly or by means of asphyxiated blood, causes 
 contraction of the spleen [hence, -the spleen is " small and contracted " in death 
 from asphyxia]. The fibres proceed down the cord, and are probably joined by 
 other fibres derived from ganglion cells lying opposite the first to the fourth cer- 
 vical vertebrae, which cells also act on the spleen. The fibres leave the cord in 
 the dorsal region, enter the left splanchnic, pass through the semilunar ganglion, 
 and thus reach the splenic plexus (Jaschkowitz). Stimulation of the peripheral 
 ends of these nerves causes contraction of the spleen, and so does cold applied 
 to the spleen directly or over the region of the organ. In this last case the result 
 is brought about reflexly. Section or paralysis of these nerves causes dilatation, 
 and so does curara or continued narcosis (Belgak). [Botkin found that the appli- 
 cation of the induced current to the skin over the spleen, in a case of leukaemia, 
 caused well-marked contraction of the spleen in all its dimensions ; the spleen 
 becoming firmer, and its surface more irregular. The result lasted much longer 
 
THE THYMUS. 177 
 
 than the duration of the stimulus. The same occurred in a case of enlarged 
 lymphatic glands. After a time the organ began to enlarge. After every stimu- 
 lation the number of colorless corpuscles in the blood increased, and the condi- 
 tion of the patient improved.] 
 
 [There is a popular notion that the spleen is influenced by the condition of the 
 nervous system. Botkin found that depressing emotions increased its size, while 
 exhilarating ideas diminished it. The causes of these changes are referable not 
 only to changes in the amount of blood in the spleen, but also to the greater or 
 less degree of contraction of its muscular tissue. And it would appear that, like 
 the small arteries, the muscular tissue of the spleen is in a state of tonic con- 
 traction. The size of the spleen may be influenced reflexly. Thus, Tarchan- 
 off found that stimulation of the central end of the vagus, when the splanchnics 
 were intact, caused contraction of the spleen, while stimulation of the centra/. 
 end of the sciatic also caused contraction, but to a less degree. It is quite cer- 
 tain that all the phenomena are not due to the action of vasomotor nerves on the 
 splenic blood vessels. There is a certain amount of independent action of the 
 muscular fibres of the organ, and it is not improbable that the innervation of the 
 spleen is similar to the innervation of arteries, and that it has a motor centre in 
 the cord capable of being influenced reflexly by afferent nerves, while it also sends 
 out efferent impulses.] 
 
 [Roy confirmed most of these results, and found that stimulation of (i) the cen- 
 tral end of a sensory nerve ; (2) of the peripheral ends of both splanchnics ; 
 (3) of the peripheral ends of both vagi, caused contraction of the spleen. But 
 even after section of the splanchnics and vagi, stimulation of a sensory nerve 
 still caused contraction, so that there must be some other channel as yet unknown. 
 Bochefontaine found that electrical stimulation of certain parts of the cortex 
 cerebri produced contraction of the spleen.] Sensory nerves seem to occur only 
 in the peritoneum covering the spleen. 
 
 Pressure on the splenic vein causes enlargement of the spleen (Mosler) ; hence, increased 
 pressure in this vein (congestion of the portal vein, cessation of hemorrhoidal and menstrual dis- 
 charges) also cause its enlargement. With regard to the action of " splenic reagents," such as 
 quinine, on the contraction of the spleen, Binz is of opinion that this drug retards the formation 
 of the colorless blood corpuscles,- so that its chief function is interfered with and the organ becomes 
 less vascular. It is not definitely decided, however, whether it is contraction or dilatation of the 
 spleen that alters the proportion of red and white corpuscles in the blood. 
 
 Splenic Tumors. — The increase in size of the spleen in various diseases early attracted the 
 attention of physicians. The healthy spleen undergoes several variations in volume during the 
 course of a day, corresponding to the varying activity of the digestive organs. In this respect the 
 spleen resembles the arteries. In many fevers the spleen becomes greatly enlarged, probably due 
 to paralysis of its nerves. It is greatly increased in intermittent fever or ague, and often during the 
 course of typhus. When it becomes abnormally enlarged, and remains so after repeated attacks of 
 the ague, it is greatly hypertrophied and constitutes " ague cake." In cases of splenic leukaemia 
 it is greatly enlarged, and at the same time there is a great increase in the number of colorless cor- 
 puscles in the blood and also a decrease of the colored ones (j! io). 
 
 II. THE THYMUS. — During fcetal life this gland is largely developed, and it increases during 
 the first two or three years of life, remaining stationary until the tenth or fourteenth year, when it 
 begins to atrophy and undergo fatty degeneration. [The degeneration begins at the outer part of 
 each lobule and progress inward (His)."] 
 
 Structure.— [" It consists of an aggregation of lymph follicles (resembling the glands of Peyer) 
 or masses of adenoid tissue held together by a framework of connective tissue which contains blood 
 vessels, lymphatics, and a few nerves (Fig. 121). The framework of connective tissue gives off 
 septa which divide the gland into lobes, these being further subdivided by finer septa into lobules, 
 the lobules being separated by fine intra-lobular lamellae of connective tissue into follicles (0.5-1.5 
 mm.). These follicles make up the gland substance, and they are usually polygonal when seen in 
 a section. Each follicle consists of a cortical and a medullary part, and the matrix or frame- 
 work of both consists of a fine adenoid reticulum whose meshes are filled with lymph corpuscles " 
 (Fig. 122, a).] Many of these corpuscles exhibit various stages of disintegration. In the medulla 
 are found the concentric corpuscles of Hassall. [" They consist of a central granular part, 
 around which is disposed layers of flattened, nucleated, endothelial cells arranged concentrically. 
 When seen in a section they resemble the 'cell nests' of epithelioma (Fig. 122, b). They have 
 12 
 
178 
 
 THE THYROID. 
 
 also been compared to similar bodies which occur in the prostate. They are most numerous when 
 the gland undergoes its retrograde metamorphosis."] 
 
 Simon, His, and others described a convoluted blind canal, the " central canal," as occurring 
 within the gland, and on it the follicles were said to be placed. Other observers, Jendrassik and 
 Klein, either deny its existence or regard it merely as a lymphatic or an artificial product. Numer. 
 ous fine lymphatics penetrate into the interior of the organ, and many are distributed over its sur- 
 face, but their mode of origin is unknown. [They seem to be channels through which the lymph 
 corpuscles are conveyed away from the gland..] Numerous blood vessels are also distributed to 
 the septa and follicles (Fig. 121, c). 
 
 Chemical Composition. — Besides gelatin, albumin, soda albumin, there are sugar and fat, 
 leuchin, xanthin, hypoxanthin, formic, acetic, butyric, and succinic acids. Potash and phosphoric 
 acid are more abundant in the ash than soda, calcium, magnesium (? ammonium), chlorine, and 
 sulphuric acid (v. Gomp-Besanez). 
 
 Function. — As long as it exists, it seems to perform the functions of a true lymph gland. This 
 view is supported by the fact that in reptiles and amphibians, which do not possess lymph glands, 
 the thymus remains as a permanently active organ. That the thymus forms colorless corpuscles was 
 first maintained by Hewson, and confirmed by His and Jendrassik. [Extirpation (Friedleben) 
 gave few positive results, but chemical investigation shows that the parenchyma contains a large 
 number of products indicating considerable metabolic activity. The volume of the gland undergoes 
 variations both in health and disease.] 
 
 Section of the thymus gland of a cat, showing one 
 complete lobule with an outer cortical part, a 
 centre, 6. and parts of adjoining lobules, a, 
 lymphoid tissue ; c, blood vessels injected ; d, 
 connective tissue. 
 
 Elements of the thymus ( X 3°°)- <*. 
 lymph corpuscles ; b, concentric 
 corpuscle of Hassall. 
 
 III. THE THYROID. — Structure. — In a connective-tissue network rich in cells there lie 
 numerous completely closed sacs (0.04 to O.I mm. in diameter), which in the embryo and the 
 newly-born animal are composed of a membrana propria lined by a single layer of nucleated cubi- 
 cal cells (Fig. 123). The sacs contain a transparent, viscid, albuminous fluid. [Not unfrequently 
 the sacs contain many colored blood corpuscles (Baber). As in other glands there are lobes and 
 lobules.] Each sac is surrounded by a plexus of capillaries which do not penetrate the membrana 
 propria. There are also numerous lymphatics. At an early period the sacs dilate, their cellular 
 lining atrophies, and their contents undergo colloid degeneration. When the gland vesicles are 
 greatly enlarged " goitre " is produced. 
 
 The Chemical Composition of this gland has not been much investigated. In addition to the 
 ordinary constituents, leucin, xanthin, sarkin, lactic, succinic, and volatile fatty acids have been 
 found. 
 
 [Excision. — The effects differ, according to the animal operated on. This gland has been excised 
 in the human subject in cases of goitre. Reverdin pointed out that a peculiar condition resulted, 
 called Cachexia stumipriva, and practically the human being becomes a cretin. This operation, 
 therefore, is highly questionable when performed on man (Kocker). Rabbits endure the operation 
 well. Of dogs, only a very small number survive, nearly all die. The immediate effects are fibril- 
 lar contractions, which ultimately influence the gait of the animals, convulsions, anaesthesia, great 
 diminution of sensibility, loss of flesh, redness of the ears and intense heat of the skin (which dis- 
 appear after several days), difficulty in seizing and eating food, kerato-conjunctivitis, and frequently 
 disturbance of the rhythm of respiration with dyspnoea and spasms of the abdominal muscles [Schiff, 
 
THE THYROID. 
 
 179 
 
 Zesas,J. Wagner). The arterial blood contains about the same amount of O as venous blood. 
 Certain parts of the peripheral nerves undergo a kind of degeneration similar to that found after 
 nerve stretching. There is albuminuria and fall of the blood pressure (Albertoni and Tizzoni). 
 There is a great tendency for the animal to run backward. Death usually occurs between the 
 third and fourth day, the animals being comatose {Wagner). SchifF found that if one-half of 
 the gland was excised at once, and the other half a month afterward, death did not occur ; but 
 Wagner denies this, for he asserts that the remaining half hypertrophies, and if it be excised 
 death occurs, with the usual symptoms. In monkeys, five days after the operation, there are 
 symptoms of nervous disturbance. The animals have lost their appetite, there are fibrillar con- 
 tractions of the muscles of the face, hands, and feet, but the tremors disappear on voluntary effort. 
 The appetite returns and is increased, but notwithstanding, the animal grows thin and pale ; while 
 the tremors increase and affect all the muscles of the body. These tremors are of central origin, 
 because they disappear on dividing the nerve. Thus there is profound alteration of the motor 
 powers. Among the outward symptoms are puffiness of the eyelids, swelling of the abdomen, 
 increased hebetude, and dyspnoea, while afterward there is a fall of the temperature and imbecility ; 
 the tremors disappear, there is a pallor of the skin, and ultimately, after five to seven weeks, the 
 animals die in a comatose state. Thus there is a slow onset of hebetude, terminating in imbecility. 
 Very remarkable changes occur in the blood. There is a steady fall of the blood pressure, 
 
 Fig. 123. 
 
 Section of the thyroid gland ( X 250). a, small closed vesicles lined by low columnar epithelium ; 6, colloid 
 masses distending the vesicles ; c, connective tissue 1 between the vesicles. 
 
 oligemia (diminution of the red blood corpuscles) or rather profound anaemia, leucocythsemia 
 or leucocytosis, the colorless corpuscles being increased to the ratio of four to fourteen, and 
 lastly mucin is present in the blood, although normally it is not so. The salivary glands 
 are hypertrophied, owing to the presence of mucin, which is found even in the parotid, 
 although this is normally a serous gland (§ 141). The swelling of the abdomen is due to 
 hypertrophy of the great omentum. Mucin is found in the peritoneal fluid, and the spleen 
 is also enlarged. Thus these symptoms present many features in common with those of 
 Myxcedena described by Ord (v. Horsley).'] 
 
 [Stages. — Horsley distinguishes three stages. The first or neurotic exhibits constant tremors, 
 8 per second, and young animals do not appear to survive this stage. In the second or mucinoid 
 stage, mucin is deposited in the tissues and blood ; this change, however, is only seen to perfection 
 in monkeys. If these animals be kept at a high artificial temperature, their life is considerably 
 prolonged. In the third atrophic or marasmic period, the animals die of marasmus, while they 
 lose their excess of mucin. Age seems to exert an important influence in thyroidectomy ; young 
 dogs survive but a short time, while old dogs merely exhibit symptoms of indolence and incapacity ; 
 and as a matter of fact, the activity of the gland seems to be most active when tissue metabolism is 
 most active.] 
 
 [The following table, after Horsley, indicates the symptoms that follow : — 
 
180 
 
 THE SUPRARENAL CAPSULES. 
 Loss of the Function of the Thyroid Gland. 
 
 Stages. 
 
 Duration. 
 
 Symptoms. 
 
 Remarks. 
 
 I. Neurotic. 
 
 I to 2 weeks in 
 dogs; I to 3 
 weeks in mon- 
 
 Tremors, rigidity, 
 dyspnoea. 
 
 Young dogs and monkeys 
 alike die in this stage. 
 
 II. Mucinoid. 
 
 keys. 
 
 J to I weekin 
 dogs; 3 to 7 
 weeks in mon- 
 
 Commencing hebetude 
 and mucinoid degen- 
 eration of the connec- 
 tive tissues. 
 
 Dogs survive only to the 
 beginning of this stage ; 
 monkeys die at the end, 
 if not treated. 
 
 
 keys. 
 
 * 
 
 
 III. Atrophic. 
 
 5 to8weeks in 
 monkeys. 
 
 Complete imbecility and 
 atrophy of all tissues, 
 especially muscles. 
 
 Monkeys survive accord, 
 ing to the temperature 
 of the air-bath. 
 
 Fig. 124. 
 
 Functions. — The functions of the thyroid gland are very obscure. Perhaps it may be an 
 apparatus for regulating the blood supply to the head (?). It becomes enlarged in Basedow's 
 disease, in which there is great palpitation as well as protrusion of the eyeball [Exophthalmos], 
 which seem to depend upon a simultaneous stimulation of the accelerating nerve of the heart, and 
 the sympathetic fibres for the smooth muscles in the orbital cavity and the eyelids, as well as of the 
 inhibitory fibres of the vessels of the thyroid. In many localities it is common to find swelling of 
 the thyroid constituting goitre, which is sometimes, but far from invariably, associated with idiocy 
 and cretinism. [Horsley finds that its removal is the essential cause of myxoedena and cretinism. 
 He regards it (1) as a blood-forming gland, so that it has a hsemapoietic function, but Gibson 
 finds no grounds for supporting this view. During the anaemia resulting from its removal, the blood 
 of the thyroid vein contains 7 per cent, more red blood corpuscles than the corresponding artery 
 {Horsley). (2) It seems to regulate the formation of mucin in the body. After its removal the 
 
 normal metabolism is no longer maintained, and there is a 
 corresponding increasingly defective condition of nutrition.] 
 In the Tunicata, this gland, represented by a groove, 
 secretes a digestive fluid. In vertebrates, it is an organ 
 which has undergone a retrograde change (Gegenbaur). 
 
 IV. THE SUPRARENAL CAPSULES.— 
 Structure. — These organs are invested by a thin cap- 
 sule which sends processes into the interior of the organ. 
 They consist of an outer (broad) or cortical layer and an 
 inner (narrow) or medullary layer. The former is yellow- 
 ish in color, firm and striated, while the latter is softer 
 and deeper in tint. In the outermost zone of the cortex 
 (Fig. 124, b), the trabecular form polygonal meshes, 
 which contain the cells of the gland subs-tance ; in the 
 broader middle zone the meshes are elongated, and the 
 cells filling them are arranged in columns radiating out- 
 ward. Here the cells are transparent and nucleated, often 
 containing oil globules ; in the innermost narrow zone the 
 polygonal arrangement prevails, and the cells often contain 
 yellowish-brown pigment. In the medulla (c) the stroma 
 forms a reticulum containing groups of cells of very irreg- 
 ular shape. Numerous blood vessels occur in the gland, 
 especially in the cortex. [The nerves are extremely 
 numerous, and are derived from the renal and solar 
 plexuses. Many of the fibres are medullated. After 
 they enter the gland, numerous ganglionic cells occur in 
 the plexuses which they form. Indeed, some observers 
 regard the cells of the medulla as nervous. Undoubtedly, 
 numerous multipolar nerve cells exist within the gland.] — 
 (Eberth, Creighton, v. Brunti). 
 
 Chemical Composition. — The suprarenals contain 
 
 the constituents of connective tissue and nerve tissue ; 
 
 also leucin, hypoxanthin, benzoic, hippuric, and tauro- 
 
 Section of a human suprarenal capsule, a, cap- cholic acids, taurin, inosit, fats, and a body which becomes 
 
 ^if^at^SS^STEf^ pigmented >? oxidation Among inorganic substances 
 
 dulla ; d, blood vessels. potash and phosphoric acid are most abundant. 
 
HYPOPHYSIS CEREBRI. 181 
 
 The function of the suprarenal body is very obscure. It is noticeable, however, that in Addi- 
 son's disease ("bronzed skin "), which is perhaps primarily a nervous affection, these glands 
 have frequently, but not invariably, been found to be diseased. Owing to the injury to adjacent 
 abdominal organs extirpation of these organs is often, although not always, fatal ; in dogs pig- 
 mented patches have been found in the skin near the mouth. Brown- Sequard thinks they may be 
 concerned in preventing the over-production of pigment in the blood. 
 
 [Spectrum. — MacMunn finds that the medulla of the suprarenal bodies (in man. cat, dog, 
 guinea pig, rat, etc.) gives the spectrum of hsemochromogen ({! 18), while the cortex shows that of 
 what he calls histohaematin, the latter being a group of respiratory pigments. He finds that hoe- 
 mochromogen is only found in excretory organs (the bile, the liver) ; hence, he regards the medulla 
 as excretory, so that part of the function of the adrenals may be "to metamorphose effete haemo- 
 globin or hasmatin into haemachromogen," and when they are diseased, the effete pigment is not 
 removed ; hence, the pigmentation of the skin and mucous membranes. Taurocholic acid has been 
 found in the medulla ( Vulpian). MacMunn believes that " they have a large share in the down- 
 ward metamorphosis of coloring matter." Krukenberg regards the pigment as a pyrocatechin 
 compound.] 
 
 V. HYPOPHYSIS CEREBRI— COCCYGEAL AND CAROTID GLANDS.— The 
 
 hypophysis cerebri, or pituitary body, consists of an anterior lower or larger lobe, partly em- 
 bracing the posterior lower or smaller lobe. These two lobes are distinct in their structure and 
 development. The posterior lobe is a part of the brain, and belongs to the infundibulum. The 
 nervous elements are displaced by the ingrowth of connective tissue and blood vessels. The 
 anterior portion represents an inflected and much altered portion of ectoderm, from which it is 
 developed. It contains gland-like structures, with connective tissue, lymphatics and blood vessels, 
 the whole being surrounded by a capsule. According to Ecker and Mihalkowicz, it resembles the 
 suprarenal capsule in its structure, while, according to other observers, in some animals it is more 
 like the thyroid. Its functions are entirely unknown. 
 
 [Excision. — Horsley has removed this gland twice successfully in dogs, which lived from five to 
 six months. No nervous or othej symptoms were noticed, but when the cortex of the brain was 
 exposed and stimulated, a great increase in the excitability of the motor regions was induced, even 
 slight stimulation being followed by violent tetanus and prolonged epilepsy.] 
 
 Coccygeal and Carotid Glands. — The former, which lies on the tip of the coccyx, is composed, 
 to a large extent, of plexuses of small, more or less cavernous arteries, supported and enclosed by 
 septa and a capsule of connective tissue (Luschka). Between these lie polyhedral granular cells, 
 arranged in networks. The carotid gland (Fig. 45) has a similar structure (p. 114). Their func- 
 tions are quite unknown. Perhaps both organs may be regarded as the remains of embryonal blood 
 vessels (Arnold}. 
 
 104. COMPARATIVE. — The heart in fishes, as well as in the larva? of amphibians with 
 gills, is a simple venous heart, consisting of an auricle and a ventricle. The ventricle propels the 
 blood to the gills, where it is oxygenated (arterialized) ; thence it passes into the aorta, to be dis- 
 tributed to all parts of the body, and returns, through the capillaries of the body and the veins, to 
 the heart. The amphibians (frogs) have two auricles and one ventricle. From the latter there 
 proceeds one vessel which gives off the pulmonary arteries, and as the aorta supplies the rest of the 
 body with blood, the veins of the systemic circulation carry their blood to the right auricle ; those of 
 the lung into the left auricle. In fishes and amphibians there is a dilatation at the commencement 
 of the aorta, the bulbus arteriosus, which is partly provided with strong muscles. The reptiles 
 possess two separate auricles and two imperfectly-separated ventricles. The aorta and pulmonary 
 artery arise separately from the two latter chambers. The venous blood of the systemic and pulmo- 
 nary circulations flows separately into the right and left auricles, and the two streams are mixed in 
 the ventricle. In some reptiles, the opening in the ventricular septum seems capable of being closed. 
 The crocodile has two quite separate ventricles. The lower vertebrates have valves at the orifices 
 of the vente cavae, which are rudimentary in birds and some mammals. All birds and mammals 
 have two completely separate auricles and two separate ventricles. In the halicore, the apex of the 
 ventricles is deeply cleft. Some animals have accessory hearts, e.g., the eel,'in its caudal vein. They 
 are, very probably, lymph hearts (Robin). The veins of the wing of the bat pulsate (Schiff). The 
 lowest vertebrate, amphioxus, has no heart, but only a rhythmically-contracting vessel. 
 
 Among blood glands, the thymus and spleen occur throughout the vertebrata, the latter being 
 absent only in amphioxus and a few fishes. .1 
 
 Among invertebrata a closed vascular system, with pulsatile movement, occurs here and there, 
 e,g., among echinodermata (star fishes, sea urchins, holothurians) and the higher worms. The 
 insects have a pulsating "dorsal vessel" as the central organ of the circulation, which is a con- 
 tractile tube provided with valves and dilated by muscular action, the blood being propelled rhythmi- 
 cally in one direction into the spaces which lie among the tissues and organs, so that these animals 
 do not possess a closed vascular system. The mollusca have a heart, with a lacunar vascular 
 system. The cephalopods (cuttle fish) have three hearts — a simple arterial heart and two venous 
 simple gill hearts, each placed at the base of the gills. The vessels form a completely closed circuit. 
 
182 HISTORICAL RETROSPECT OF THE CIRCULATION. 
 
 The lowest animals have either a pulsatile vesicle, which propels the colorless juice into the tissues 
 (infusoria), or the vascular apparatus may be entirely absent. 
 
 105. HISTORICAL RETROSPECT.— The ancients held various theories regarding the 
 movement of the blood, but they knew nothing of its circulation. According to Aristotle (384 B. c), 
 the heart, the acropolis of the body, prepared in its cavities the blood, which streamed through the 
 1 arteries as a nutrient fluid to all parts of the body, but never returned to the heart. 
 
 With Herophilus and Erasistratus (300 B.c), the celebrated physicians of the Alexandrian school, 
 originated the erroneous view that the arteries contain air, which was supplied to them by the respi- 
 ration (hence the name artery). They were led to adopt this view from the empty condition of the 
 arteries after death. By experiments upon animals, Galen disproved this view (131—201 A.D.) — 
 " Whenever I injured an artery," he says, " blood always flowed from the wounded vessel. On tying 
 part of an artery between two ligatures, the part of the artery so included is always filled with 
 blood." 
 
 Still, the idea of a single centrifugal movement of the blood was retained, and it was assumed 
 that the right and left sides of the heart communicated directly, by means of openings in the septum 
 of the heart, until Vesalius showed that there are no openings in the septum. Michael Servetus 
 (the Spanish monk, burned at Geneva, at Calvin's instigation, in 1553) discovered the pulmonary 
 circulation. Cesalpinus confirmed this observation, and named it " Circulatio." Fabricius ab Aqua- 
 pendente (Padua, 1574) investigated the valves in the veins more carefully (although they were 
 known in the fifth century to Theodoretus, Bishop in Syria), and he was acquainted with the cen- 
 tripetal movement of the blood in the veins. Up to this time, it was imagined that the veins carried 
 blood from the centre to the periphery, although Vesalius was acquainted with the centripetal direc- 
 tion of the blood stream in the large venous trunks. At length, William Harvey, who was a 
 pupil of Fabricius (1604), demonstrated the complete circulation (1616-1619), and published his 
 great discovery in 1628. [For the history of the discovery of the circulation of the blood, see the 
 works of Willis on "W. Harvey," ''Servetus and Calvin," those of Kirchner, and the various 
 Harveian orations] 
 
 According to Hippocrates, the heart is the origin of all the vessels ; he was acquainted with the 
 large vessels arising from the heart, the valves, the chordae tendinese, the auricles, and the closure 
 of the semilunar valves. Aristotle was the first to apply the terms aorta and venae cavae ; the school 
 of Erasistratus used the term carotid, and indicated the functions of the venous valves. In Cicero a 
 distinction is drawn between arteries and veins. Celsus mentions that if a vein be struck below the 
 spot where a ligature has been applied to a limb, it bleeds, while Aretaeus (50 A. D.) knew that 
 arterial blood was bright and venous dark. Pliny (f 79 A. D.) described the pulsating fontanelle in 
 the child. Galen (131—203 A. D.) was acquainted with the existence of a bone in the septum of 
 the heart of large animals (ox, deer, elephant). He also surmised that the veins communicated 
 with the arteries by fine tubes. The demonstration of the capillaries, however, was only possible 
 by the use of the microscope, and employing this instrument, Malpighi (1661) was the first to 
 demonstrate the capillary circulation. Leuwenhoek (1674) described the capillary circulation more 
 carefully, as it may be seen in the web of the frog's foot and other transparent membranes. Blan- 
 card (1676) proved the existence of capillary passages by means of injections. William Cooper 
 (1697) proved that the same condition exists in warm-blooded animals, and Ruysch made similar 
 injections. Stenson (born 1638) established the muscular nature of the heart, although the Hippo- 
 cratic and Alexandrian schools had already surmised the fact. Cole proved that the sectional area 
 of the blood stream became wider toward the capillaries (1681). Joh. Alfons Borelli (1608-1679) 
 was the first to estimate the amount of work done by the heart. 
 
Physiology of Respiration. 
 
 The object of respiration is to supply the oxygen necessary for the oxidation 
 processes that go on in the body, as well as to remove the carbonic acid formed , 
 within the body. The most important organs for this purpose are the lungs. 
 There is an outer and an inner respiration — the former embraces the exchange 
 of gases between the external air and the blood gases of the respiratory organs 
 (lungs and skin) — the latter, the exchange of gases between the blood in the ca- 
 pillaries of the systemic circulation and the tissues of the body. 
 
 [The pulmonary apparatus consists of (i) an immense number of small sacs — 
 the air vesicles filled with air, and covered externally by a very dense plexus of 
 capillaries; (2) air passages — the nose, pharynx, larynx, trachea, and bronchi 
 communicating with (1) ; (3) the thorax with its muscles, acting like a pair of 
 bellows, and moving the air within the lungs.] 
 
 106. STRUCTURE OF THE AIR PASSAGES AND LUNGS.— The lungs are com- 
 pound tubular (racemose ?) glands, which separate C0 2 from the blood. Each lung is provided 
 with an excretory duct (bronchus) which joins the common respiratory passage of both lungs — the 
 trachea. 
 
 Trachea*. — The trachea and extra-pulmonary bronchi are similar in structure. The basis of the 
 trachea consists of a number (16-20) of C -shaped, incomplete cartilaginous hoops placed over each 
 other. These rings consist of hyaline ca rtilage, and are united to each other by means of tough,) 
 fibrous tissue containing much elastic tissue, the latter being arranged chiefly in a longitudinal direc-/ 
 tion. The function of the cartilages is to keep the tube open under varying conditions of pres ■ 
 sure. Pieces of cartilage having a similar function occur in the bronchi and their branches, but 
 they are absent from the bronchioles, which are less than I mm. in diameter. In the smaller bronchi 
 the cartilages are fewer and scattered more irregularly. [In a transverse section of a large intra- 
 pulmonary bronchus, two, three, or more pieces of cartilage, each invested by its perichondrium, 
 may be found.] At the points where the bronchi subdivide, the cartilages assume the form of ir- 
 regular plates embedded in the bronchial wall. 
 
 An external fibrous layer of connective tissue and elastic fibres covers the trachea and the extra- 
 pulmonary bronchi externally. Toward the oesophagus, the elastic elements are more numerous, 
 and there are also a few bundles of plain muscular fibres arranged longitudinally. Within this layer 
 there are bundles of non-striped muscular fibres which pass transversely between the cartilages 
 behind, and also in the intervals between the cartilages. [These pale reddish fibres constitute the 
 trachealis muscle, and are attached to the inner surfaces of the cartilages by means of elastic 
 tendons at a little distance from their free ends (Munniks, 1697). The arrangement varies in dif- 
 ferent animals — thus, in the cat, dog, rabbit, and rat the muscular fibres are attached to the external 
 surfaces of the cartilages, while in the pig, sheep, and ox they are attached to their internal sur- 
 faces (Stirling).} Some muscular fibres are arranged longitudinally external to the transverse fibres 
 (Kramer). The function of these muscular fibres is to prevent too great distention when there is ( 
 great pressure within the air passages. 
 
 The mucous membrane consists of a basis of very fine connective tissue, containing much 
 adenoid tissue with numerous lymph corpuscles. It also contains numerous elastic fibres, arranged 
 chiefly in a longitudinal direction under the basement membrane. They are also abundant in the 
 deep layers of the posterior part of the membrane opposite the intervals between the cartilages. A 
 small quantity of loose submucous connective tissue containing the large blood vessels, glands and 
 lymphatics unites the mucous membrane to the perichondrium of the cartilages. The epithelium 
 consists of a layer of columnar ciliated cells with several layers of immature cells under them. ' 
 [The superficial layer of cells is columnar and ciliated (Fig. 125, b), while those lying under them 
 present a variety of forms, and below all is a layer of somewhat flattened squames, c, resting on the 
 basement membrane, d. These squames constitute a layer quite distinct- from the basement mem- 
 brane, and they form the layer described as Debove's membrane. They are active germinating 
 cells, and play a most important part in Connection with the regeneration of the epithelium, after 
 the superficial layers have been shed, in such conditions as bronchitis (v. Drasch, Hamilton). Not 
 
 183 
 
184 
 
 STRUCTURE OF THE TRACHEA. 
 
 unfrequently a little viscid mucus (o) lies on the free ends of the cilia. In the intermediate layer, 
 the cells are more or less pyriform or battledore-shaped [Hamilton), with their long, tapering pro- 
 cess inserted among the deepest layer of squames. According to Drasch, this long process is 
 attached to one of these cells and is an outgrowth from it, the whole constituting a " foot cell."] 
 
 Underneath the epithelial is the homogeneous basement membrane, through which fine canals 
 pass, connecting the cement of the epithelium with spaces in the mucosa. [This membrane is well 
 marked in the human trachea, where it plays an important part in many pathological conditions, 
 e. g., bronchitis. It is stained bright red with picrocarmine.] The cilia act so as to carry any secre- 
 tion toward the larynx. Goblet cells exist between the ciliated columnar cells. Numerous small 
 compound tubular mucous glands occur in the mucous membrane, chiefly between the cartilages. 
 Their ducts open on the surface by means of a slightly funnel-shaped aperture into which the 
 ciliated epithelium is prolonged for a short distance. [The acini of some of these glands lie out- 
 side the trachealis muscle. The acini are lined by cubical or columnar secretory epithelium. In 
 some animals (dog) these cells are clear, and present the usual characters of a mucus-secreting 
 
 IfteS-: 
 
 Transverse section of part of a normal human bronchus (X 45°)- «, precipitated mucus on the surface of the ciliated 
 epithelium, b ; 6, ciliated columnar epithelium ; c, deep germinal layer of cells (Debove's membrane) ; d, elastic 
 basement membrane ; e, elastic fibres divided transversely (inner fibrous layer) ; f, bronchial muscle (non-striped) ; 
 g, outer fibrous layer with leucocytes and pigment granules (black) deposited in it. The lower part of the figure 
 shows a mass of adenoid tissue. 
 
 gland ; in man, some of the cells may be clear, and others " granular," but the appearance of the 
 cells depends upon the physiological state of activity.] These glands secrete the mucus, which 
 entangles particles inspired with the air, and is carried toward the larynx by ciliary action. 
 [Numerous lymphatics exist in the mucous and submucous coat, and not unfrequently small aggre- 
 gations of adenoid tissue occur (especially in the cat) in the mucous coat, usually around the ducts 
 of the glands. They are comparable to the solitary follicles of the alimentary tract.] The blood 
 vessels are not so numerous as in some other mucous membranes. [A plexus of nerves contain- 
 taining numerous ganglionic cells at the nodes exist on the posterior surface of the trachealis muscle. 
 The fibres are derived from the vagus, recurrent laryngeal aud sympathetic (C. Frankenhauser, W. 
 Stirling, Jfandarazi)."] 
 
 [The mucous membrane of the trachea and extra-pulmonary bronchi, therefore, consists 
 of the following layers from within outward : — 
 (i) Stratified columnar ciliated epithelium. 
 
STRUCTURE OF THE BRONCHI AND BRONCHIOLES. 185 
 
 (2) A layer of flattened cells (Debove's membrane). 
 
 (3) A clear homogeneous basement membrane. 
 
 (4) A basis of areolar tissue, with adenoid tissue and blood vessels, and outside this a layer 
 
 of longitudinal elastic fibres. 
 
 Outside this, again, is . the submucous coat, consisting of loose areolar tissue, with the larger 
 vessels, lymphatics, nerves and mucous glands.]- 
 
 [The Bronchi. — In structure the extra-pulmonary bronchi resemble the trachea. As they 
 pass into the lung they divide very frequently, and the branches do not anastomose. In the intra- 
 pulmonary bronchi the subdivisions become finer and finer, the finest branches being called 
 terminal bronchi, or bronchioles, which open separately into clusters of air vesicles.] 
 
 [Eparterial and Hyparterial Bronchi. — As the bronchi proceed, one main trunk passes into 
 the lung, running toward its base, and from it are given off branches dorsally and ventrally, and 
 these branches again subdivide. Aeby has shown that the relation of the branches to the pul- 
 monary artery is most important. In man one main branch comes off from the right bronchus and 
 proceeds to the upper right lobe, above the place where the pulmonary artery crosses the bronchus. 
 Such branches are called eparterial, and they are more numerous in birds. In man, all the branches, 
 both on the right and left side, come off below the point where the pulmonary artery crosses the 
 bronchus, and are called hyparterial bronchi (C Abey)^\ 
 
 [In the middle-sized intra-pulmonary bronchi, the usual characters of the mucous membrane 
 are retained, only it is thinner ; the cartilages assume the form of irregular plates situated in the 
 outer wall of the bronchus ; while the muscular fibres are disposed in a complete circle, constituting 
 the bronchial muscle (Fig. 125, /). When this muscle is contracted, or when the bronchus as a 
 whole is contracted, the mucous membrane is thrown into longitudinal folds, and opposite these 
 folds the elastic fibres form large elevations. This muscle is particularly well developed in the 
 smaller microscopic bronchi. Numerous elastic fibres, e, disposed longitudinally, exist under the 
 basement membrane, a". They are continuous with those of the trachea, and are prolonged 
 onward into the lung. The mucous membrane of the larger intra-pulmonary bronchi consists 
 of the following layers from within outward : — 
 
 (1) Stratified columnar ciliated epithelium (Fig. 125, b). 
 
 (2) Debove's membrane (Fig. 125, c). 
 
 (3) Transparent homogeneous basement membrane (Fig. 125, d). 
 
 (4) Areolar tissue with longitudinal elastic fibres (Fig. 125, e). 
 
 (5) A continuous layer of non-striped muscular fibres disposed circularly (bronchial muscle — 
 
 Fig. 125,/). 
 Outside this is the submucous coat, consisting of areolar tissue mixed with much adenoid tissue 
 (Fig. I25,£-), sometimes arranged in the form of cords, the lymph-follicular cords of Klein. It 
 also contains the acini of the numerous mucous glands, blood vessels and lymphatics. The ducts 
 of the glands perforate the muscular layer, and open on the free surface of the mucous membrane. 
 The submucous coat is connected by areolar tissue with the perichondrium of the cartilages. Out- 
 side the cartilages are the nerves and nerve ganglia accompanying the bronchial vessels. The 
 branches of the pulmonary artery and of the pulmonary vein usually lie on opposite sides of the 
 bronchus, while there are several branches of the bronchial arteries and veins. Fat cells also 
 occur in the peri -bronchial tissue.] 
 
 In the small bronchi the cartilages and glands disappear, but the circular muscular fibres are 
 well developed. They are lined by lower columnar ciliated epithelium, containing goblet cells. 
 
 Bronchioles. — After repeated subdivision, the bronchi form the " smallest bronchi " (about 0.5 
 to 1 mm.) or lobular bronchial tubes. Each tube is lined by a layer of cilated epithelium, but the 
 glands and cartilages have disappeared. These tubes have a few lateral alveoli or air cells com- 
 municating with them. Each smallest bronchus ends in a "respiratory bronchiole" (Kolliker), 
 which gradually becomes beset with more air cells, and in which squamous epithelium begins to 
 appear between the ciliated epithelial cells. [Each bronchiole opens into several wider alveolar 
 or lobular passages. Each passage is completely surrounded with air cells, and from it are given 
 off several similar but wider blind branches, the infundibula, which, in their turn, are beset on all 
 sides with alveoli or air cells. Several infundibula are connected with each bronchiole, and the 
 former are wider than the latter. Each bronchiole, with its alveolar passages, infundibula, and air 
 vesicles, is termed a lobule, whose base is directed outward, and whose apex may be regarded as a 
 terminal bronchus. The lung is made up of an immense number of these lobules, separated from 
 each other by septa of connective tissue, the interlobular septa (Fig. 128, e) which are continuous 
 on the one hand with the sub-pleural connective tissue, and on the other with the peri-bronchial con- 
 nective tissue.] 
 
 [It is evident that there is an alteration in the structure of the bronchi, as we proceed from the 
 larger to the smaller tubes. The cartilages and glands are the first structures to disappear. The 
 circular bronchial muscle is well developed in the smaller bronchi and bronchioles, and exists as a 
 continuous thin layer over the alveolar passages, but it is not continued over and between the air 
 cells. Elastic fibres, continuous, on the one hand, with those in the smaller bronchi, and on the 
 other with those in the walls of the air cells, lie outside the muscular fibres in the bronchioles and 
 infundibula. In the respiratory bronchioles, the ciliated epithelium is reduced to a single layer, and 
 
186 THE BLOOD VESSELS OF THE LUNG. 
 
 is mixed with the stratified form of epithelium, while where the alveolar passages open into the air 
 cells or alveoli, the epithelium is non-ciliated, low, and polyhedral.] 
 
 Alveoli or Air Cells. — The form of the air cells, which are 250 fi ( T Jj inch) in diameter, may 
 be more or less spherical, polygonal, or cup-shaped. They are disposed around and in communica- 
 tion with the alveolar passages. Their form is determined by the existence of a nearly structure- 
 less membrane, composed of slightly fibrillated connective tissue containing a few corpuscles. This 
 is surrounded by numerous fine elastic fibres, which give to the pulmonary parenchyma its well- 
 marked elastic characters (Fig. 127, <?, e). These fibres often bifurcate, and are arranged with ref- 
 erence to the alveolar wall. They are very resistant, and in some cases of lung disease may be 
 recognized in the sputum. A few non-striped muscular fibres exist in the delicate connective tissue 
 between adjoining air vesicles (Moleschott). These muscular fibres sometimes become greatly 
 developed in certain diseases (Arnold, W. Stirling). The air cells are lined by two kinds of cells — 
 (1) large, transparent, clear polygonal (nucleated?) squames or placoids (22-45 /*) lying over 
 and between the capillaries in the alveolar wall (Fig. 126, a) ; (2) small, irregular, " granular," 
 nucleated cells (7-15 /*) arranged singly or in groups (two or three) in the interstices between the 
 capillaries. They are well seen in a cat's lung (Fig. 126,1/). [When acted on with nitrate of 
 silver the cement substance bounding the clear cells is stained, but the small cells become of a uni- 
 form brown, granular appearance, so that they are readily recognized. Small holes or " pseudo- 
 Fir,. 126. 
 
 Air vesicles from a kitten whose lungs were injected with silver nitrate ( X 450). <*, outlines of fully developed 
 squamous epithelium ; b, alveolar wall; c, young epithelial cell losing its granular appearance ; d, aggregation 
 of young epithelial cells germinating. 
 
 stomata" seem to exist in the cement substance, and are most obvious in distended alveoli 
 (Klein). They open into the lymph-canalicular system of the alveolar wall (Klein), and through 
 them the lymph corpuscles, which are always to be found on the surface of the air vesicles, migrate, 
 and carry with them into the lymphatics particles of carbon derived from the air.] In the alveolar 
 walls is a very dense plexus of fine capillaries (Fig. 127, c), which lie more toward the cavity of 
 the air vesicle (Rainey), being covered only by the epithelial lining of the air cells. Between two 
 adjacent alveoli there is only a single layer of capillaries (man), and on the boundary line between 
 two air cells the course of the capillaries is twisted, thus projecting sometimes into the one alveolus, 
 sometimes into the other. 
 
 [The number of Alveoli is stated to be about 725 millions, a result obtained by measuring the 
 size of the air vesicles and ascertaining the amount of air in the lung after an ordinary inspiration, 
 and determining how much of this air is in the air vesicles and bronchi respectively. The superficial 
 area of the air vesicles is about 90 square metres, or 100 times greater than the surface of the body 
 (.8 to .9 sq. metre) (Rosenthal).] 
 
 The Blood vessels of the lung belong to two different systems : (A) Pulmonary vessels 
 (lesser circulation). The branches of the'pulmonary artery accompany the bronchi and are closely 
 applied to them. [As they proceed they branch, but the branches do not anastomose, and ultimately 
 they terminate in small arterioles which supply several adjacent alveoli, each arteriole splitting up 
 
THE PLEURA OF THE LUNG. 
 
 187 
 
 into capillaries for severala.it cells (Fig. 127, v, c). An efferent vein usually arises at the opposite 
 side of the air cells and carries away the purified blood from the capillaries. In their course these 
 veins unite to form the pulmonary veins, which are joined in their course by a few small bronchial 
 veins (Zuckerkandl). The veins usually anastomose in the earlier part of their course, while the 
 corresponding arteries do not.] Although the capillary plexus is very fine and dense, its sectional 
 area is less than the sectional area of the systemic capillaries, so that the blood stream in the pulmo- 
 nary capillaries must be more rapid than that in the capillaries of the body generally. The pulmo- 
 nary veins, unlike veins generally, are collectively narrower than the pulmonary artery (water is 
 given off in the lung), and they have no valves. [The pulmonary artery contains venous blood, 
 and the pulmonary veins pure or arterial blood.] 
 
 (B) The bronchial vessels represent the nutrient system of the lungs. They (1-3) arise from 
 the aorta (or intercostal arteries) and accompany the bronchi without anastomosing with the branches 
 of the pulmonary artery. In their course they give branches to the lymphatic glands at the hilum 
 of the lung, to the walls of the large blood vessels (vasa vasorum), the pulmonary pleura, the 
 bronchial walls, and the interlobular septa. The blood which issues from their capillaries is returned 
 
 Fig. 127. 
 
 Semi-diagrammatic representation of the air vesicles of the lung, v, v, blood vessels at the margins of an alveolus ; 
 c, c, its blood capillaries ; E, relation of the squamous epithelium of an alveolus to the capillaries in its wall ; /, 
 alveolar epithelium shown alone ; e, e, elastic tissue of the lung. 
 
 — partly by the pulmonary veins — hence, any considerable interference with the pulmonary circula- 
 tion causes congestion of the bronchial mucous membrane, resulting in a catarrhal condition of that 
 membrane. The greater part of the blood is returned by the bronchial veins which open into the 
 vena azygos, intercostal vein, or superior vena cava. The veins of the smaller bronchi (fourth order 
 onward) open into the pulmonary veins, and the anterior bronchial also communicate with the pul- 
 monary veins (Zuckerkandl). 
 
 [The Pleura. — Each pleural cavity is distinct, and is a large serous sac, which really belongs to 
 the lymphatic system of the lung. The pleura consists of two layers, visceral and parietal. The 
 visceral pleura covers the lung ; the parietal portion lines the wall of the chest, and the two layers 
 of the corresponding pleura are continuous with one another at the root of the lung. The visceral 
 pleura is the thicker, and may readily be separated from the inner surface of the chest. Structurally, 
 the pleura resembles a serous membrane, and consists of a thin layer of fibrous tissue covered by a 
 layer of endothelium. Under this layer, or the pleura proper, is a deep or sub-serous layer of looser 
 areolar tissue, containing many elastic fibres. The layer of the pleura pulmonalis of some animals, 
 as the guinea pig, contains a network of non-striped muscular fibres (Klein). Over the lung it is 
 
188 
 
 THE LYMPHATICS OF THE LUNG. 
 
 also continuous with the interlobular septa. The interlobular septa (Fig. 1 28, e) consist of bands 
 of fibrous tissue separating adjoining lobules, and they become continuous with the peri-bronchial 
 connective tissue entering the lung at its hilum. Thus the fibrous framework of the lung is continu- 
 ous throughout the lung, just as in other organs. The connection of the sub-pleural fibrous tissue 
 with the connective tissue within the substance of the lung, has most important pathological bearings. 
 The interlobular septa contain lymphatics and blood vessels. The endothelium covering the parietal 
 layer is of the ordinary squamous type, but on the pleura pulmonalis the cells are less flattened, 
 more polyhedral, and granular. They must necessarily vary in shape with changes in the volume 
 of the lung, so that they are more flattened when the lung is distended, as during inspiration (Klein). 
 The pleura contains many lymphatics, which communicate by means of stomata with the pleural 
 cavity.] 
 
 [The Lymphatics of the lung are numerous and are arranged in several systems. The various 
 air cells are connected with each other by very delicate connective tissue, and according to J. Ar- 
 nold in some parts this interstitial tissue presents characters like those of adenoid tissue ; so that the 
 lung is traversed by a system of juice canals or " Saft-canalchen."] [In the deep layer of the 
 
 Fig. 128. 
 
 Normal human lung (X 50 and reduced 5^). a, small bronchus ; b b, branches ot the pulmonary artery ; c, branch 
 of the pulmonary vein ; e, interlobular septa, continuous with the deep layer of the pleura, /. 
 
 pleura, there is (a) sub-pleural plexus of lymphatics partly derived from the pleura, but chiefly 
 from the lymph-canalicular system of the pleural alveoli. Some of these branches proceed to the 
 bronchial glands, but others pass into thei nterlobular septa, where they join (6) the perivascular 
 lymphatics which arise in the lymph-canalicular system of the alveoli. These trunks, provided 
 with valves, run alongside the pulmonary artery and vein, and in their course they form frequent 
 anastomoses. Special vessels arise within the walls of the bronchi and occur chiefly in the outer 
 coat of the latter, constituting (c) the peri-bronchial lymphatics, which anastomose with b. The 
 branches of these two sets run toward the bronchial glands. Not unfrequently (cat) masses of 
 adenoid tissue are found in the course of these lymphatics (Klein)."] The lymph-canalicular system 
 and the lymphatics become injected when fine colored particles are inspired, or are introduced into 
 the air cells artificially. The pigment particles pass through the semi-fluid cement substance into 
 the lymph-canalicular system and thence into the lymphatics (v. Wittich) ; or, according to Klein, 
 they pass through actual holes or pores in the cement (p. 186).] [This pigmentation is well seen 
 in coal miner's lung or anthracosis, where the particles of carbon pass into and are found in the 
 
PHYSICAL PROPERTIES OF THE LUNGS. 189 
 
 lymphatics. Sikorski and Kiittner showed that pigment reached the lymphatics this way during 
 life. If pigment, China ink, or indigo carmine be introduced into a frog's lung, it is found in the 
 lymphatic system of the lung. Ruppert, and also Schotielius, showed that the same result occuned 
 in dogs after the inhalation of charcoal, cinnabar, or precipitated Berlin blue, and von Ins after the 
 inhalation of silica. A. Schestopal used China ink and cinnabar suspended in % per cent, salt 
 solution.] Excessively fine lymph canals lie in the wall of the alveoli in the interspaces of the 
 capillaries, and there are slight dilatations at the points of crossing (Wydwozoff). According to 
 Pierret and Renaut every air cell of the lung of the ox is surrounded by a large lymph space, such 
 as occurs in the salivary glands. When a large quantity of fluid is injected into the lung it is 
 absorbed with great rapidity ; even blood corpuscles rapidly pass into the lymphatics. [Nothnagel 
 found that, if blood was sucked in the lung of a rabbit, the blood corpuscles were found within the 
 interstitial connective tissue of the lung after ■>,% to 5 minutes, from which he concludes that the 
 communications between the cavity of the air cells and the lymphatics must be very numerous.] 
 
 The superficial lymphatics of the pulmonary pleura communicate with the pleural cavity by 
 means of free openings or stomata [Klein), and the same is true of the lymphatics of the parietal 
 pleura, but these stomata are confined to limited areas over the diaphragmatic pleura. [The lymph- 
 atics in the costal pleura occur over the intercostal spaces and not over the ribs [Dybkowski)!\ The 
 large arteries of the lung are provided with lymphatics which lie between the middle and outer 
 coats [Grancher). [The movements of the lung during respiration are most important factors in 
 moving the lymph onward in the pulmonary lymphatics. The return of the lymph is prevented by 
 the presence of valves.] 
 
 [The Nerves of the lung are derived from the anterior and posterior pulmonary plexuses, and 
 consist of branches from the vagus and sympathetic. They enter the lungs and follow the distribu- 
 tion of the bronchi, several sections of nerve trunks being usually found in a transverse section of a 
 large bronchial tube. These nerves lie outside the cartilages, and are in close relation with the 
 branches of the bronchial arteries. Medullated and nonmedullated nerve fibres occur in the nerves, 
 which also contain numerous small ganglia [Remak, Klein, Stirling). In the lung of the calf 
 these ganglia are so large as to be microscopic. The exact mode of termination of the nerve fibres 
 within the lung has yet to be ascertained in mammals, but some fibres pass to the bronchial muscle, 
 others to the large blood vessels of the lung, and it is highly probable that the mucous glands are 
 also supplied with nerve filaments. In the comparatively simple lungs of the frog, nerves with 
 numerous nerve cells in their course are found [Arnold, Stirling), and in the very simple lung of 
 the newt, there are also numerous nerve cells disposed along the course of the intra-pulmonary 
 nerves. Some of these fibres terminate in the uniform layer of non-striped muscle which forms 
 part of the pulmonary wall in the frog and newt, and others end in the muscular coat of the pul- 
 monary blood vessels [Stirling). The functions of these ganglia are unknown, but they may be 
 compared to the nerve plexuses existing in the walls of the digestive tract.] 
 
 The Function of the Non-striped Muscle of the entire bronchial system 
 seems to be to offer a sufficient amount of resistance to increased pressure within the 
 air passages ; as in forced expiration, speaking, singing, blowing, etc. The vagus 
 is the motor nerve for these fibres, and according to Longet (1842), the "lung- 
 tonus " during increased tension depends upon these muscles. It is not proved 
 to what extent bronchial (spasmodic) asthma depends upon contraction of these 
 muscular fibres due to stimulation of the vagus. 
 
 [Effect of Nerves. — By connecting the interior of a small bronchus with an oncograph [\ 103) 
 in the case of curarized dogs (the thorax being opened), Graham Brown and Roy found that sec- 
 tion of one vagus causes a marked expansion of the bronchi of the corresponding lung, while 
 stimulation of the peripheral end of a divided vagus causes a powerful contraction of the bronchi 
 of both lungs. Stimulation of the central end of one vagus, the other being intact, also causes a 
 contraction (feebler) under the same circumstances. Especially in etherized dogs, expansion and 
 not contraction results. If both vagi be divided, no effect is produced by stimulation of the central 
 end of either vagus. It seems plain that the vagi contain centripetal or afferent fibres, which can 
 cause both expansion and contraction of the bronchi. Asphyxia causes contraction provided the 
 vagi are intact, but none if they are divided, although in etherized dogs expansion frequently occurs, 
 while stimulation of the central end of other sensory nerves has very rarely any, or if any, but a 
 slight effect on the calibre of the bronchi, so that in the dog, the only connection between the cere- 
 bro-spinal centres and.the bronchi is through the vagi]. 
 
 Chemistry. — In addition to connective, elastic, and muscular tissue, the lungs contain lecithin, 
 inosit, uric acid (taurin and leucin in the ox), guanin, xanthin (?), hypoxanthin (dog) —soda, pot- 
 ash, magnesium, oxide of iron, much phosphoric acid, also chlorine, sulphuric and silicic acids — in 
 diabetes sugar occurs — in purulent infiltration glycogen and sugar — in renal degeneration urea, oxalic 
 acid, and ammonia salts ; and in diseases where decomposition takes place, leucin and tryosin. 
 
 [Physical Properties of the Lungs. — The lungs, in virtue of the large 
 amount of elastic tissue which they contain, are endowed with great elasticity, 
 
190 MECHANISM OF RESPIRATION. 
 
 so that when the chest is opened they collapse. If a cannula with a small lateral 
 opening be tied into the trachea of a rabbit's or sheep's lungs, the lungs may be 
 inflated with a pair of bellows or elastic pump. After the artificial inflation, the 
 lungs, owing to their elasticity, collapse and expel the greater part of the air. As 
 much air remains within the light spongy tissue of the lungs, even after they are 
 removed from the body, a healthy lung floats in water. If the air cells are filled 
 with pathological fluids or blood, as in certain diseased conditions of the lung 
 (pneumonia), then the lungs, or parts thereof, may sink in water. The lungs of 
 the foetus, before respiration has taken place, sink in water, but after respiration 
 has been thoroughly established in the child, the lungs float. Hence, this hy- 
 drostatic test is largely used, in medico-legal cases, as a test of the child having 
 breathed.. If a healthy lung be squeezed between the fingers, it emits a peculiar 
 and characteristic fine, crackling sound, owing to the air within the air cells. A 
 i similar sound is heard on cutting the vesicular tissue of the lung. The color of 
 ' the lungs varies much ; in a young child it is rose-pink, but afterward it becomes 
 darker, especially in persons living in towns or a smoky atmosphere, owing to the 
 deposition of granules of carbon. In coal miners the lungs may become quite 
 black.] 
 
 [Excision of the Lung. — Dogs recover after the excision of one entire lung, and they even 
 survive the removal of portions of lung infected with tubercle (JBiotuH).] 
 
 107. MECHANISM OF RESPIRATION.— -The mechanism of respi- 
 ration consists in an alternate dilatation and contraction of the chest. The dila- 
 tation is called inspiration, the contraction, expiration. As the whole external 
 surface of both elastic lungs are applied directly and in an air-tight manner, by 
 their smooth, moist, pleural investment, to the inner wall of the chest, which is 
 covered by the parietal pleura, it is clear that the lungs must be distended with 
 every dilatation of the chest, and diminished by every contraction thereof. These 
 movements of the lungs, therefore, are entirely passive, and are dependent on 
 the thoracic movements {Galen.) 
 
 On account of their complete elasticity and their great extensibility, the lungs 
 are able to accommodate themselves to any variation in the size of the thoracic 
 cavity, without the two layers of the pleura becoming separated from each other. 
 As the capacity of the non-distended chest is greater than the volume of the col- 
 lapsed lungs after their removal from the body, it is clear that the lungs, even in 
 their natural position within the chest, are distended, i.e., they are in a certain 
 state of elastic tension (§ 60). The tension is greater, the more distended the 
 thoracic cavity, and vice versd. As soon as the pleural cavity is opened by per- 
 foration from without, the lungs, in virtue of their elasticity, collapse, and a space 
 filled with air is formed between the surface of the lungs and the inner surface of 
 the thoracic wall (pneumothorax). The lungs so affected are rendered useless 
 for respiration ; hence, a double pneumothorax causes death. 
 
 Pneumothorax. — It is also clear that, if the pulmonary pleura be perforated from within the 
 lung, air will pass from the respiratory passages into the pleural sac, and also give rise to pneumo- 
 thorax. 
 
 [Not unfrequently the surgeon is called on to open the chest, say, by removing a portion of a rib, 
 to allow of the free exit of pus from the pleural cavity. If this be done with proper precautions, 
 and if the external wound be allowed to heal, after a time the air in the pleural cavity becomes 
 absorbed, the collapsed lung tends to regain its original form, and again becomes functionally active.] 
 
 Estimation of Elastic Tension. — If a manometer be introduced through an intercostal space 
 into the pleural cavity, in a dead subject, we can measure, by means of a column of mercury, the 
 amount of the elastic tension required to keep the lung in its position. This is equal to 6 mm. in 
 the dead subject, as well as in the condition of expiration. If, however, the thorax be brought into 
 the position of inspiration, by the application of traction from without, the elastic tension may be 
 increased to 30 mm. Hg. (Bonders). 
 
 If the glottis be closed and a deep inspiration taken, the air within the lungs 
 must become rarified, because it has to fill a greater space. If the glottis be sud- 
 denly opened, the atmospheric air passes into the lungs until the air within the 
 
SPIROMETRY AND VITAL CAPACITY. 
 
 191 
 
 lungs has the same density as the atmosphere. Conversely, if the glottis be closed, 
 and if an expiratory effort be made, the air within the chest must be compressed. If 
 the glottis be suddenly opened, air passes out of the lungs until the pressure outside 
 and inside the lung is equal. As the glottis remains open during ordinary respira- 
 tion, the equilibration of" the pressure within and without the lungs will take place 
 gradually. During tranquil inspiration there is a slight negative pressure ; during 
 expiration, a slight positive pressure in the lungs; the former = i mm., the latter 
 2-3 mm. Hg. in the human trachea (measured in cases of wounds of the trachea). 
 
 108. QUANTITY OF GASES RESPIRED.— As the lungs within the 
 chest never give out all the air they contain, it is clear that only a part of the air 
 
 of the lungs is changed during inspiration and expiration 
 air will depend upon the depth of the respirations. 
 
 Hutchinson (1846) distinguishes the following points : — 
 
 (1) Residual Air is the volume of air which remains in the 
 chest after the most complete expiration. It is equal to 1230-1640 
 c. c. [100-130 cubic inches]. 
 
 (2) Reserve or Supplemental Air is the volume of air which 
 can be expelled from the chest after a normal quiet expiration. It is 
 equal to 1240-1800 c. c. [100 cubic inches]. 
 
 (3) Tidal Air is the volume of air which is taken in and given 
 out at each respiration. It is equal to 500 cubic centimetres [20 
 cubic inches]. 
 
 (4) Complemental Air is the volume of air that can be forcibly 
 inspired over and above what is taken in at a normal respiration. It 
 amounts to about 1500 c. c. [100-130 cubic inches]. 
 
 (5) Vital Capacity is the term applied to the 
 volume of air which can be forcibly expelled from the 
 chest after the deepest possible inspiration. It is equal 
 to 3772 c. c. (or 230 cubic inches) for an Englishman 
 {Hutchinson), and 3222 for a German (Jfmser). 
 
 Hence, after every quiet inspiration, both lungs con- 
 tain (1 + 2 + 3) = 3000 to 3900 c.cm. [220 cubic 
 inches]; after a quiet expiration (1 -f 2) = 2500 to 
 inches]. So that about \ to ^ of the air in the 
 lungs is subject to renewal at each respiration. 
 
 Estimation of Vital Capacity. — The esti- 
 mation of the vital capacity was formerly thought 
 to be of great consequence, but at the present time 
 not much importance is attached to it, nor is it fre- 
 quently measured in cases of disease. It. is esti- 
 mated by means of the spirometer of Hutchinson. 
 This instrument (Fig. 1 29), consists of a graduated 
 cylinder filled with water and inverted like a 
 gasometer over water, and balanced by means 
 of a counterpoise. Into this cylinder a tube 
 projects, and this tube is connected with a 
 mouth piece. The person to be experimented 
 upon takes the deepest possible inspiration, 
 closes his nostrils, and breathes forcibly into 
 the mouth piece of the tube. After doing so the 
 tube is closed. The cylinder is raised by the 
 air forced into it, and after the water inside 
 and outside the cylinder is equalized, the height 
 to which the cylinder is raised indicates the 
 amount of air expired, or the vital or respiratory 
 capacity. In a man of average height, 5 feet 8 
 inches, it is equal to 230 cubic inches. 
 
 The volume of this 
 
 COMPLEMENTAL 
 
 AIR, 
 
 TIDAL AIR, 
 20 
 
 RESERVE AIR 
 
 RESIDUAL AIR 
 
 3400 c.cm. 
 Fig. 129. 
 
 [200 cubic 
 
 Scheme of Hutchinson's Spirometer. 
 
192 
 
 TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. 
 
 The following circumstances affect the vital capacity : — 
 
 (i) The Height. — Every inch added to the height of persons between 5 and 6 feet, gives an 
 increase of the vital capacity = 130 c.c. [8 cubic inches.] 
 
 (2) The Body weight. — When the body weight exceeds the normal by 7 per cent., there is a 
 diminution of 37 c.c. of the vital capacity for every kilo, of increase. 
 
 (3) Age. — The vital capacity is at its maximum at 35; there is an annual decrease of 23.4 c.c. 
 from this age onward to 65, and backward to 15 years of age. 
 
 (4) Sex. — It is less in women than men, and even where there is the same circumference of 
 chest, and the same height in a man and a woman, the ratio is 10 : 7. 
 
 (5) Position. — More air is respired, in the erect than in the recumbent position. 
 
 (6) Disease. — Abdominal and thoracic diseases diminish it. 
 
 109. NUMBER OF RESPIRATIONS.— In the adult, the number of 
 respirations varies from 16 to 24 per minute, so that about 4 pulse beats occur 
 during each respiration. The number of respirations is influenced by many 
 conditions : — 
 
 (1) The Position of the Body. — In the adult, in the horizontal position, Guy counted 
 while sitting 19, while standing 22, respirations per minute. 
 
 (2) The Age. — Quetelet found the mean number of respirations in 300 individuals to be : — 
 
 '3. 
 
 Year. Respirations. 
 
 o to I, 44 1 Average 
 
 5, 26 [■ Number per 
 
 15 to 20, 20 J Minute. 
 
 Year. Respirations. 
 
 20 to 25, 18.7 I Average 
 
 25 to 30 16 >■ Number per 
 
 30 to 50 18.1 ) Minute. 
 
 (3) The State of Activity. — Gorham counted in children of 2 to 4 years of age, during stand- 
 ing 32, in sleep 24, respirations per minute. During bodily exertion the number of respirations 
 increases before the heart beats. [Very slight muscular exertion suffices to increase the frequency 
 of the respirations.] 
 
 [(4) The Temperature of the surrounding medium. — The respirations become more numerous 
 the higher the surrounding temperature, but this result only occurs when the actual temperature of 
 the blood is increased, as in fever. 
 
 (5) Digestion. — There is a slight variation during the course of the day, the increase being most 
 marked after mid- day dinner ( Vierordf). 
 
 (6) The Will can to a certain extent modify the number and also the depth of the respirations, 
 but after a short time the impulse to respire overcomes the voluntary impulse. 
 
 (7) The Gases of the Blood have a marked effect, and so has the heat of the blood in fever.] 
 [(8) In Animals — 
 
 Mammals. 
 
 Per Min. 
 6 
 
 Tiger 
 
 Lion, io v «Horse, 
 
 Taguar, n >k Ass, 
 
 Panther, 18 
 
 — Cat, . . 24 
 
 - Dog, 15 
 
 Dromedary, II 
 
 Giraffe 8-10 
 
 -■Ox 15-18 
 
 Squirrel, 70 
 
 -—Rabbit, 55 
 
 ~Rat (waking), 210 
 
 ^Rat (asleep), 100 
 
 Rhinoceros, 6-10 
 
 Mammals. 
 Hippopotamus, . . 
 
 Per Min. 
 
 I 
 
 . IO-I2 
 
 7 
 
 Birds. 
 
 Condor 6 
 
 Sparrow . . ... 90 
 
 Pigeon 30 
 
 Siskin 100 
 
 Canary , 
 
 Snake . 
 Tortoise 
 
 Reptiles. 
 
 18 
 
 5 
 12 
 
 Fish. 
 
 Kaja . . . 
 Torpedo . . 
 Perch . . . 
 Mullet . . . 
 Eel ... . 
 Hippocampus 
 
 Per Min. 
 
 • 5° 
 ■ 5' 
 
 • 30 
 . 60 
 
 • 5° 
 
 33 
 
 Invertebrata. 
 
 Crab 12 
 
 Mollusca 14-65 
 
 {P. Bert).] 
 
 [(9) In Disease. — The number may be greatly increased from many causes, e.g., in fever, 
 pleurisy and pneumonia, some heart diseases, or in certain cases of alteration of the blood, as in 
 ansemia ; and diminished where there is pressure on the respiratory centre in the medulla, in 
 coma. It is important to note the ratio of pulse beats to respirations.] 
 
 no. TIME OCCUPIED BY THE RESPIRATORY MOVE- 
 MENTS. — The time occupied in the various phases of a respiration can only be 
 accurately ascertained by obtaining a curve or pneumatogram of the respiratory, 
 movements. 
 
 Methods. — (1) Vierordt and C. Ludwig transferred the movements of a part of the chest wall 
 to a lever which inscribed its movements upon a revolving cylinder. Riegel (1873) constructed a 
 " double stethograph " on the same principle. This instrument is so arranged that one arm of the 
 
VARIOUS FORMS OF STETHOGRAPHS. 
 
 193 
 
 lever may be applied in connection with the healthy side of a person's chest, and the other on the 
 diseased side. 
 
 (2) An air tambour, such as is used in Brondgeest's pansphygmograph (Fig. 131, A) may be used. 
 It consists of a brass vessel, a, shaped like a small saucer. The mouth of the brass vessel is covered 
 
 Fig. 130. 
 
 Marey's stethograph. 
 
 with a double layer oi caoutchouc membrane, b, c, and air is forced in between the two layers until 
 the external membrane bulges outward. This is placed on the chest, and the apparatus is fixed in 
 position by means of the bands, d, d. The cavity of the tambour communicates by means of a 
 caoutchouc tube, s, with a recording tambour, which inscribes its movements upon a revolving cyl- 
 
 FlG. 131. 
 
 A, Brondgeest's tambour for registering the respiratory movements. 6, c, inner and outer caoutchouc membranes ; a, 
 the capsule; d t d, cords for fastening the instrument to the chest; S, tube to the recording tambour; B, nor- 
 mal respiratory curve obtained on a vibrating plate (each vibration = 0.01613 sec). 
 
 inder. Every dilatation of the chest compresses the membrane, and thus the air within the tambour 
 is also compressed. [A somewhat similar apparatus is used by Burdon-Sanderson, and called a 
 "recording stethograph." By it movements of the corresponding points on opposite sides of 
 the chest can be investigated.] 
 
 *3 
 
194 
 
 TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. 
 
 (3) A cannula or oesophageal sound may be introduced into that portion of the oesophagus which 
 lies in the chest, and a connection established with Marey's tambour, p. 85 (Rosenthal). [This 
 method also enables one to measure the intra-thoracic pressure. "\ 
 
 Marey's Stethograph or Pneumograph. — [There are two forms of this instrument, one modi- 
 fied by P. Bert and the more modern form (Fig. 130). A tambour (k) is fixed at right angles to a 
 thin elastic plate of steel (/)• The aluminium disk on the caoutchouc of the tambour is attached 
 to an upright [i), whose end lies in contact with a horizontal screw (g). Two arms (d, c) are 
 attached to opposite sides of the steel plate, and to them the belt (e) which fastens the instrument 
 to the chest is attached. When the chest expands these two arms are pulled asunder, the steel plate 
 is bent, and the tambour is affected, and any movement of the tambour is transmitted to a registering 
 tambour by the air in the tube (a).] 
 
 In the case of animals placed on their backs, Snellen introduced a long needle vertically through 
 the abdominal walls into the liver. Rosenthal opened the abdomen and applied a lever to the 
 under surface of the diaphragm, and thus registered its movements (Phrenograph). 
 
 The- curve (Fig. 131, B) was obtained by placing the tambour of a Brondgeest's 
 
 Fig. 132. 
 
 Fneumatograms obtained by means of Riegel's stethograph I, normal curves ; II, curve from a case 01 emphysema; 
 a, ascending limb ; b, apex ; c, descending limb of the curve. The small elevations are due to the cardiac * 
 impulse. 
 
 pansphygmograph upon the xiphoid process, and recording the movement upon a 
 plate attached to a vibrating tuning fork. The inspiration (ascending limb) begins 
 with moderate rapidity, is accelerated in the middle, and toward the end again 
 becomes slower. The expiration also begins with moderate rapidity, is then accel- < 
 erated, and becomes much slower at the latter part, so that the curve falls very 
 gradually. 
 
 Inspiration is slightly shorter than Expiration. — According to Sibson, the ratio 
 for an adult is as 6 to 7 ; in women, children and old people, 6 to 8 or 6 to 9. 
 Vierordt found the ratio to be 10 to 14. 1 (to 24.1); J. R. Ewald, 11 to 12. It 
 is only occasionally that cases occur where inspiration and expiration are equally*| 
 long, or where expiration is shorter than inspiration. When respiration proceeds ;| 
 quietly and regularly, there is usually no pause (complete rest of the chest walls) 
 between the inspiration and expiration (Riege!). The very flat part of the expira- j 
 
PATHOLOGICAL VARIATIONS OF RESPIRATORY MOVEMENTS. 195 
 
 tory curve has been wrongly regarded as due to a pause. Of course, we may make 
 a voluntary pause between two respirations, or at any part of a respiratory act. 
 
 Some observers, however, have described a pause as occurring between the end of expiration and 
 the beginning of the next inspiration (expiration pause), and also another pause at the end of inspi- 
 ration (inspiration pause). The latter is always of very short duration, and considerably shorter 
 than the former. 
 
 During very deep and slow respiration, there is usually an expiration pause, while it is almost 
 invariably absent during rapid breathing. An inspiration pause is always absent under normal cir- 
 cumstances, but it may occur under pathological conditions. 
 
 In certain parts of the respiratory curve slight irregularities may appear, which are sometimes 
 due to vibrations communicated to the thoracic walls by vigorous heart beats (Fig. 132). 
 
 The " type " of respiration may be ascertained by taking curves from various 
 parts during the respiratory movements. Hutchinson showed that in the female 
 the thorax is dilated chiefly by raising the sternum and the ribs (Respiratio cos- 
 talis), while in man, it is caused chiefly by a descent of the diaphragm (Respi- 
 ratio diaphragmatica or abdominalis). In the former there is the so-called 
 "costal type," in the latter the "abdominal or diaphragmatic type." 
 
 Forced Respiration. — This difference in the type of respiration in the sexes occurs only during 
 normal quiet respiration. During deep and forced respiration, in both sexes, the dilatation of the 
 chest is caused chiefly by raising the chest and the ribs. In man, the epigastrium may be pulled in 
 sooner than it is protruded. During sleep, the type of respiration in both sexes is thoracic, while, 
 at the same time, the inspiratory dilatation of the chest precedes the elevation of the abdominal 
 wall {Mosso). 
 
 It is not determined whether the costal type of respiration in the female depends upon the con- 
 striction of the chest by corsets or other causes (Sibson), or whether it is a natural adaptation to the 
 child-bearing function in women {Hutchinson). Some observers maintain that the difference of type 
 is quite distinct, even in sleep, when all constrictions are removed, and that similar differences are 
 noticeable in young children. This is denied by others, while a third class of observers hold that 
 the costal type occurs in children of both sexes, and they ascribe as a cause the greater flexibility 
 of the ribs of children and women, which permits the muscles of the chest to act more efficiently 
 upon the ribs. [When a child sucks, it breathes exclusively through the nose ; hence, catarrhal 
 conditions of the nasal mucous membrane are fraught with danger to the child.] 
 
 in. PATHOLOGICAL VARIATIONS OF THE RESPIRATORY MOVE- 
 MENTS. — [Examination of the Lungs. — The same methods that are applicable to the heart 
 — viz., I, Inspection ; II, Palpation; III, Percussion ; and IV, Auscultation — apply here also.] 
 
 [By Inspection we may determine the presence of symmetrical or unilateral alterations in the 
 shape of the chest, the presence of bulging or flattening at one part, and variations in the movement 
 of the chest walls. By Palpation, the presence or absence, character, seat and extent of any move- 
 ments are more carefully examined. But we may also study what is called Vocal fremitus (§ 117). 
 For Percussion (J 114); Auscultation (J 116).] 
 
 [In investigating the respiratory movements, we should observe (1) the frequency (fj 109 ) ; (2) 
 the type (g 1 10) ; (3) the nature, character and extent of the movements, noting, also, whether they 
 are accompanied by pain or not (J 1 10) ; (4) the rhythm.] 
 
 I. Changes in the Mode of Movement — In persons suffering from disease of the respiratory 
 organs, the dilatation of the chest may be diminished (to the extent of 5 or 6 cm. ) on both sides or 
 only on one side. In affections of the apex of the lung (in phthisis), the subnormal expansion of 
 the upper part of the wall of the chest may be considerable. Retraction of the soft parts of the 
 thoracic wall, the xiphoid process, and the parts where the lower ribs are inserted, occurs in cases 
 where air cannot freely enter the chest during inspiration, e. g., in narrowing of the larynx ; when 
 this retraction is confined to the upper part of the thoracic wall, it indicates that the portion of the 
 lung lying under the part so affected is less extensile and diseased. 
 
 Harrison's Groove. — In persons suffering from chronic difficulty of breathing, and in whom, 
 at the same time, the diaphragm acts energetically, there is a slight groove, which passes horizon- 
 tally outward from the xiphoid cartilage, caused by the pulling in of the soft parts and correspond- 
 ing to the insertion of the diaphragm. 
 
 The duration of inspiration is lengthened in persons suffering from narrowing of the trachea 
 or larynx; expiration is lengthened in cases of dilatation of the lung, as in emphysema, where all 
 the expiratory muscles must be brought into action (Fig. 132, II).- 
 
 II. Variations in the Rhythm. — When the respiratory apparatus is much affected, there is either 
 an increase or a deepening of the respirations, or both. When there is great difficulty of breathing, 
 this is called Dyspnoea. 
 
 Causes of Dyspnoea. — (1) Limitation of the exchange of the respiratory gases in the blood 
 due to — (a) diminution of the respiratory surface (as in some diseases of the lungs) ; (b) narrow- 
 
196 THE MUSCLES OF FORCED RESPIRATION. 
 
 ing of the respiratory passages ; (c) diminution of the red blood corpuscles ; {d) disturbances of the 
 respiratory mechanism [e. g., due to affections of the respiratory muscles or nerves, or painful affec- 
 tions of the chest wall) ; (e) impeded circulation through the lungs due to various forms of heart 
 disease. (2) Heat dyspncea. — The frequency of the respirations is increased m febrile conditions. 
 The warm blood acts as a direct irritant of the respiratory centre in the medulla oblongata, and 
 raises the number of respirations to 30-60 per minute ("Heat dyspncea"). If the carotids be 
 placed in warm tubes, so as to heat the blood going to the medulla oblongata, the same phenomena 
 are produced (A. Fick). See also "Respiratory centre" (g 368). 
 
 [Orthopncea. — Sometimes the difficulty of breathing is so great that the person can only respire in 
 the erect position, i. e., when he sits or is propped up in bed. This occurs frequently toward the 
 close of some heart affections, notably in mitral lesions ; dropsical conditions, especially of the 
 cavities, may be present.] 
 
 Cheyne-Stokes' Phenomenon. — This remarkable phenomenon occurs in certain diseases, 
 where the normal supply of blood to the brain is altered, or where the quality of the blood itself is 
 altered, e. g., in certain affections of the brain and heart, and in uraemic poisoning. Respiratory 
 pauses of one-half to three-quarters of a minute alternate with a short period (}4—)4 mm .) of in- 
 creased respiratory activity, and during this time 20-30 respirations occur. The respirations consti- 
 tuting this " series " are shallow at first; gradually they become deeper and more dyspnceic; and 
 finally become shallow or superficial again. Then follows the pause, and thus there is an alterna- 
 tion of pauses and series (or groups) of modified respirations. During the pause, the pupils are 
 contracted and inactive; and when the respirations begin, they dilate and become sensible to light ; 
 the eyeball is moved as a whole at the same time [Leuie). Hein observed that consciousness was 
 abolished during the pause, and that it returned when respiration commenced. A few muscular con- 
 tractions may occur toward the end of the pause (rare). 
 
 With regard to the causes of this phenomenon there is some doubt. According to Rosenbach, 
 the anomalous nutrition of the brain causes certain intracranial centres, especially the respiratory 
 centre, to be less excitable and to be sooner exhausted, and this condition reaches its maximum 
 during the respiratory pause. During the pause these centres recover, and they again become more 
 active. As soon as they are again exhausted, their activity ceases. Luciani also regards variations 
 in the excitability of the respiratory centre as the cause of the phenomenon, which he compares 
 with the periodic contraction of the heart ($ 58). He observed this phenomenon after injury to the 
 medulla oblongata above the respiratory centre, and after apnoea produced in animals deeply narco- 
 tized with opium. It also occurs in the last stages of asphyxia, during respiration in a closed space. 
 Mosso found a similar phenomenon normally in the hybernating dormouse (Myoxus) [and traces 
 of it even in normal sleep, while it is sometimes observed in poisoning by morphia or chloral]. 
 
 Periodic Respiration of Frogs. — If frogs be kept under water, or if the aorta be clamped, 
 after several hours, they become passive. If they be taken out of the water, or if the clamp be re- 
 moved from the aorta, they gradually recover and always exhibit the Cheyne-Stokes' phenomena. 
 In such frogs the blood current may be arrested temporarily, while the phenomenon itself remains 
 (Sokolow and Luchsinger). If the blood current be arrested by ligature of the aorta, or if the 
 frogs be bled, the respirations occur in groups. This is followed by a few single respirations, and 
 then the respiration ceases completely. During the pause between the periods, mechanical stimu- 
 lation of the skin causes the discharge of a group of respirations (Siebert and Langendorff). Mus- 
 carin and digitalin cause periodic respiration in frogs [which is not due to the action of these drugs 
 on the heart]. 
 
 112. GENERAL VIEW OF THE RESPIRATORY MUSCLES. 
 
 (A) Inspiration. 
 
 I. During Ordinary Inspiration are Active. 
 
 1. The diaphragm {Nervus phrenicus.) 
 
 2. The Mm. levatores costarum longi et breves {Rami posteriores Nn. dor- 
 satium). 
 
 3. The Mm. intercostales externi et intercartilaginei {Nn. intercostales). 
 
 II. During Forced Respiration are Active. 
 
 (a) Muscles of the Trunk. 
 
 1. The three Mm. scaleni {Rami musculares of the plexus cervicalis et brachi- 
 alis). 
 
 2. M. sternocleidomastoideus {Ram. externus N. accessorii~). 
 
 3. M. trapezius {R. externus N accessorii et Ram. musculares plexus cer- 
 vicalis). 
 
 4. M. pectoralis minor {Nn. thoracici anteriores). 
 
 5. M. serratus posticus superior {N. dorsalis scapula). 
 
THE ACTION OF THE DIAPHRAGM. 197 
 
 6. Mm. rhomboidei (N. dorsalis scapula). 
 
 7. Mm. extensores columnar vertebralis (Ram. posteriores nervorum dorsalium.) 
 [8. Mm. serratus anticus major (N. thoracicus longus). ? ?] 
 
 (b) Muscles of the Larynx. 
 
 1. M. sternohyoideus {Ram. descendens hgpoglossi). 
 
 2. M. sternothyreoideus (Ram. descendens hypoglossi). 
 
 3. M. crico-arytsenoideus posticus (N. laryngeus inferior vagi). 
 
 4. M. thyreo-arytsenoideus (N. laryngeus inferior vagi). 
 
 (c) Muscles of the Face. 
 
 1. M. dilatator narium anterior et posterior (N. facialis). 
 
 2. M. levator alae nasi (N. facialis). 
 
 3. The dilators of the mouth and nares, during forced respiration [" gasping 
 for breath " ] , (N. facialis) . 
 
 (d) Muscles of the Pharynx. 
 
 1. M. levator veli palatina (N. facialis). 
 
 2. M. azygos uvulae (N. facialis). 
 
 3. According to Garland, the pharynx is always narrowed. 
 
 (B) Expiration. 
 
 I. During Ordinary Respiration. 
 
 The thoracic cavity is diminished by the weight of the chest, the elasticity oi 
 the lungs, costal cartilages and abdominal muscles. 
 
 II. During Forced Expiration. 
 The Abdominal Muscles. 
 
 1. The abdominal muscles [including the obliquus externus and internus, and 
 transversalis abdominis] (JVh. abdominis internus anteriores e nervis inter costalibus, 
 8-12). 
 
 2. Mm. intercostales interni, so far as they lie between the osseous ribs, and the 
 Mm. infracostales (Nn. intercostales). 
 
 3. M. triangularis sterni (Nn. intercostales). 
 
 4. M. serratus posticus inferior (Ram externi nerv. dorsalium). 
 
 5. M. quadratus lumborum (Ram muscular e plexu lumbali). 
 
 113. ACTION OF THE INDIVIDUAL RESPIRATORY MUSCLES.— (A) In- 
 spiration. — (1) The Diaphragm arises from the cartilages and the adjoining osseous parts of the 
 lower six ribs (costal portion), by two thick processes or crura from the upper three or four lumbar 
 vertebrae, and a sternal portion from the back of the ensiform process. 
 
 It represents an arched double cupola or dome-shaped partition, directed toward the chest ; in the 
 larger concavity on the right side lies the liver, while the smaller arch on the left side is occupied 
 by the spleen and stomach. During the passive condition, these viscera are pressed against the 
 under surface of the diaphragm, by the elasticity of the abdominal walls and by the intra-abdominal 
 pressure, so that the arch of the diaphragm is pressed upward into the chest. The elastic traction 
 of the lungs also aids in producing this result. The greater part of the upper surface of the central 
 tendon of the diaphragm is united to the pericardium. The part on which the heart rests, and 
 which is perforated by the inferior vena cava (foramen quadrilatemm) is the deepest part of the 
 middle portion of the diaphragm during the passive condition. 
 
 Action of the Diaphragm. — When the diaphragm contracts, both arched 
 portions become flatter, and the chest is thereby elongated from above down- 
 ward. In this act, the lateral muscular parts of the diaphragm pass from an 
 arched condition - into a flatter form (Fig. 133), and during a forced inspiration, 
 the lowest lateral portions, which, during rest, are in contact with the chest wall, 
 
198 
 
 CHANGES IN THE CHEST. 
 
 Fie. 133- become separated from it. The middle of the 
 
 central tendon where the heart rests (fixed by- 
 means of the pericardium and inferior vena 
 cava) takes no share in this movement, espe- 
 cially in ordinary quiet breathing, but during 
 the deepest inspiration it sinks somewhat 
 (Hasse). 
 
 Undoubtedly, the diaphragm is the most powerful 
 agent in increasing the cavity of the chest. Briicke, 
 in fact, believes that in addition to increasing the 
 length of the thoracic cavity from above downward, it 
 also increases the transverse diameter of the lower part 
 of the chest. It presses upon the abdominal viscera 
 from above, and strives to press these outward, thus 
 tending to push out the adjoining thoracic wall. If the 
 contents of the abdomen are removed from a living 
 animal, every time the diaphragm contracts the ribs are 
 drawn inward (ffaller). This, of course, hinders the 
 chest from becoming wider below, hence the presence 
 of the abdominal viscera seems to be necessary for the 
 normal activity of the diaphragm. 
 
 Every contraction of the diaphragm, by increasing 
 the intra-abdominal pressure, favors the venous blood 
 current in the abdomen toward the vena cava inferior 
 (Hasse). 
 
 „ . , .. , ... , ., ., Phrenic Nerve. — The immense importance of the 
 
 Sagittal section through the second rib on the ... , ,. ..... , • T , 
 
 right side. This figure shows that when the diaphragm as the great inspiratory muscle is proved by 
 
 arched muscular part of the diaphragm con- the fact that, after both phrenic nerves (third and fourth 
 
 *S%££fr%£% i J££ &*<£<£& c rrl ne " es U re divided - death occurs {£udse> 
 
 ence of the lower part of the chest, so that Eulenkamp). The phrenic nerve contains some sen- 
 the chest is enlarged from above downward. sory fibres for the pleura, pericardium and a portion of 
 
 the diaphragm {Schreiber, Henle, Sc&walbe). 
 The contraction of the diaphragm is not to be regarded as a " simple mu scula r contraction," 
 since it lasts 4 to 8 times longer than a simple contraction ; it is rather a short tetanic contraction, 
 which we may arrest in any stage of its activity, without bringing into action any antagonistic 
 muscles [JCronecker aud Marckwald). 
 
 (2) The Elevators of the Rib. — The ribs at their vertebral ends (which lie much higher than 
 their sternal ends) are united by means of joints, by their heads and tubercles, to the bodies and 
 transverse processes of the vertebrae. A horizontal axis can be drawn through both joints, around 
 which the ribs can rotate upward and downward. If the axes of rotation of each pair of ribs be 
 prolonged on both sides until they meet in the middle line, the angles so formed are greatest above 
 (125 ), and smaller below (88°) (A. W. Volkmann). Owing to the ribs being curved, we can 
 imagine a plane which, in the passive (expiratory) condition of the chest, has a slope from behind 
 and inward to the front and outward. If the ribs move on their axis of rotation this plane be- 
 comes more horizontal, and the thoracic cavity is increased in its transverse diameter. As the axis 
 of rotation of the upper ribs runs in a more frontal, and that of the lower ribs in a more sagittal, 
 direction, the elevation of the upper ribs causes a greater increase from before backward, and the 
 lower ribs from within outward (as the movements of ribs which are directed downward are verti- 
 cal to the axis). The costal cartilages undergo a slight tension at the same time, which brings their 
 elasticity into play. 
 
 Changes in the Chest. — All "inspiratory muscles" which act directly upon 
 the chest wall, do so by raising the ribs : (a) When the ribs are raised, the inter- 
 costal spaces are widened, (b) When the upper ribs are raised, all the lower ribs 
 and the sternum must be elevated at the same time, because all the ribs are con- 
 nected with each other by means of the soft parts of the intercostal spaces, (c) 
 During inspiration, there is an elevation of the ribs and a dilatation of the inter- 
 costal spaces. (The lowest rib is an exception; during forced respiration, at least, 
 it is drawn downward.) (</) If, on a preparation of the chest, the ribs be raised as 
 in inspiration, we may regard all those muscles as elevators of the ribs whose origin 
 and insertion become approximated. Every one is agreed that the scaleni and leva- 
 tores costarum longi et breves, the serratus posticus superior, are inspiratory muscles. 
 These are the most important inspiratory muscles which act upon the ribs. 
 
INTERCOSTAL MUSCLES. 
 
 199 
 
 Intercostal Muscles. — With regard to the action of the intercostal muscles, 
 there is a great difference of opinion. According to the above experiment, the 
 external intercostals and the intercartilaginous parts of the internal intercostals act 
 as inspiratory muscles, while the remaining portions of the internal intercostals (as 
 far as they are covered by the external) are elongated when the ribs are raised, 
 while they shorten when the chest wall descends. A muscle shortens only during 
 its activity. The internal intercostals were regarded by Hamberger as depressors 
 of the ribs or expiratory muscles. 
 
 In Fig. 134, 1, when the rods, a and b (which represent the ribs), are raised, the intercostal space 
 must be widened {ef^>c d). On the opposite side of the figure, it is evident that when the rods 
 are raised, the line, g h, is shortened (i k<^ g h, direction of the external intercostals), / m is length- 
 ened (I m<^ n, direction of internal intercostals). Fig. 134, II, shows, that when the ribs are 
 raised, the intercartilaginei, indicated by g h, and the external intercostals, indicated by / k, are 
 shortened. When the ribs are raised, the position of the muscular fibres is indicated by the diagonal 
 of the rhomb becoming shorter. 
 
 Fig. 134. 
 
 Scheme of the action of the intercostal muscles. 
 
 The mode of action of the intercostal muscles is an old story, Galen (131-203 A.D.) regarding 
 the externals as inspiratory, the internals as expiratory. Hamberger (1727) accepted this proposition, 
 and considered the intercartilaginei also as inspiratory. Haller looked upon both the external and 
 internal intercostals as inspiratory, while Vesalius (1540) regarded both as expiratory. Landerer, 
 observing that the upper two or three intercostal spaces became narrower during inspiration, regarded 
 both as active during inspiration and expiration. They keep one rib attached to the other, so that 
 their action is to transmit any strain put upon them to the wall of the chest. On this view they will 
 be in action, even when the distance between their points of attachment becomes greater. Landois 
 regards the external intercostals and intercartilaginei as active only during inspiration, the internal 
 intercostals only during expiration. [Martin and Hartwell exposed the internal intercostals and 
 observed whether they contracted along with the diaphragm, or whether the contractions of these 
 two muscles alternate. As the result of their experiments, they conclude that " the internal inter- 
 costal muscles are expiratory throughout the whole extent, at least in the dog and cat ; and that in 
 the former animal they are almost ' ordinary ' muscles of respiration, while in the latter they are 
 ' extraordinary ' respiratory mucles."] Landois is of the opinion that the chief action of these mus- 
 cles is not to raise or depress the ribs, but rather that the external intercostals and the intercartilaginei 
 
200 MUSCLES OF FORCED EXPIRATION. 
 
 offer resistance to the inspiratory dilatation of the intercostal spaces, and to the simultaneously 
 increased elastic tension of the lungs. The internal intercostals act during powerful expiratory 
 efforts {e.g., coughing), and oppose the distention of the lungs and chest caused by this act. Unless 
 muscles were present to resist the uninterrupted tension and pressure, the intercostal substance 
 would become so distended that respiration would be impossible. [According to Rutherford, the inter- 
 nal intercostals are probably muscles of inspiration.] 
 
 The Pectoralis Minor and (? Serratus Anticus Major) can only act as 
 elevators of the ribs when the shoulders are fixed, partly by the rhomboidei, and 
 partly by fixing the shoulder joint and supporting the arms, as is done instinctively 
 by persons suffering from breathlessness. 
 
 (3) Muscles acting upon the Sternum, Clavicle and Vertebral 
 Column. — When the head is fixed by the muscles of the neck, the sternocleido- 
 mastoid can raise the manubrium sterni, and the sternal end of the clavicle so 
 that the thorax is raised and thereby dilated. The scaleni also aid in this act. The 
 clavicular portion of the trapezius may act in a similar although less energetic 
 manner. When the vertebral column is straightened, it causes an elevation of the 
 upper ribs, and a dilatation of the intercostal spaces which aid inspiration. Dur- 
 ing deep respiration, this straightening of the vertebral column takes place invol- 
 untarily. 
 
 (4) Laryngeal Movements. — During labored respiration, with every 
 inspiration the larynx descends and the glottis is opened. At the same time 
 the palate is raised, so as to permit a free passage to the air entering through 
 the mouth. 
 
 (5) Facial Movements. — During labored' respiration, the facial muscles are 
 involved ; there is an inspiratory dilatation of the nostrils (well marked in the horse 
 and rabbit). When the need for respiration is very great, the mouth is gradually 
 widened, and the person, as it were, gasps for breath. During expiration, the 
 muscles that are active during (4) and (5) relax, so that a position of equilibrium 
 is established without there being any active expiratory movement to counteract 
 the inspiratory movement. During inspiration the pharynx becomes narrower 
 ( Garland). 
 
 (B) Expiration. — Ordinary expiration occurs without the aid of muscles, 
 owing to the weight of the chest, which tends to fall into its normal position 
 from the position to which it was raised during inspiration. This is aided by the 
 elasticity of the various parts of the chest. When the costal cartilages are 
 raised, which is accompanied by a slight rotation of their lower margins from 
 below forward and upward, their elasticity is called into play. As soon, therefore, 
 as the inspiratory forces cease, the costal cartilages return to their normal position, 
 — i.e., the position of expiration — and tend to untwist themselves; at the same 
 time, the elasticity of the distended lungs draws upon the thoracic walls and 
 the diaphragm. Lastly, the tense and elastic abdominal walls, which, in 
 man chiefly, are stretched and pushed forward, tend to return to their non-dis- 
 tended, passive condition when the abdominal viscera are relieved from the 
 pressure of the contracted diaphragm. (When the position of the body is re- 
 versed, the action of the weight of the chest is removed ; but in place of it, there 
 is the weight of the viscera which press upon the diaphragm. ) 
 
 The abdominal muscles [obliquus internus and externus, transversalis abdo- 
 minis and levator ani] are always active during labored respiration. They act by 
 diminishing the abdominal cavity, and they press the abdominal contents upward 
 against the diaphragm. When they act simultaneously, the abdominal cavity is 
 diminished throughout its whole extent. The Triangularis sterni depresses 
 the sternal ends of the united cartilages and bones, from the third to sixth rib 
 downward ; and the Serratus posticus inferior depresses the four lowest ribs, 
 causing the others to follow. It is aided by the Quadratus lumborum, which 
 depresses the last rib. According to Henle, the serratus posticus inferior fixes 
 the lower ribs for the action of the slips of the diaphragm inserted into them, so 
 
RELATIVE DIMENSIONS OF THE CHEST. 
 
 201 
 
 that it acts during inspiration. According to Landerer, the downward movement 
 of the ribs in the lower part of the thorax dilates the chest. 
 
 In the erect position, when the vertebral column is fixed, deep inspiration and expiration naturally 
 alter the position of the centre of gravity, so that during inspiration, owing to the protrusion of 
 the thoracic and abdominal walls, the centre of gravity lies somewhat more to the front. Hence, 
 with each respiration there is an involuntary balancing of the body. During very deep inspiration, 
 the accompanying straightening of the vertebral column and the throwing backward of the head 
 compensate for the protrusion of the anterior walls of the trunk. 
 
 114. RELATIVE DIMENSIONS OF THE CHEST.— It is important, from a physi- 
 cian's point of view, to know the dimensions of the thorax, and also the variations it undergoes at 
 different parts. The diameter of the chest is ascertained by means of callipers ; the circumference, 
 with a flexible centimetre or other measure. 
 
 In strong men, the circumference of the upper part of the chest (immediately 
 under the arms) is 88 centimetres (34.3 inches), in females, 82 centimetres (32 
 inches)'; on the level of the ensiform 
 
 process, 82 centimetres (32 inches) and j- IG . 135. 
 
 78 centimetres (30.4 inches), respect- 
 ively. When the arms are placed hori- 
 zontally, during the phase of moderate 
 expiration, the circumference immedi- 
 ately under the nipple and the angles of 
 the scapulae is equal to half the length of 
 the body ; in man, 82, and during deep 
 inspiration 89 centimetres. The cir- 
 cumference at the level of the ensiform 
 cartilage is 6 centimetres less. In old 
 people, the circumference of the upper 
 part of the chest is diminished, so that 
 the lower part becomes the wider of the 
 two. The right half of the chest is 
 usually slightly larger than the left half, 
 owing to the greater development of the 
 muscles on that side. The long diam- 
 eter of the chest — from the clavicle to 
 the margin of the lowest rib — varies very much. 
 
 The transverse diameter in man, above and below, is 25 to 26 centimetres 
 (9.7 to 10.1 inches), in females 23 to 24 centimetres (8.9 to 9.2 inches) ; above 
 the nipple it is one centimetre more. The antero-posterior diameter (dis- 
 tance of anterior chest wall from the tip of a spinous process) in the upper 
 part of the chest is = 17 (6.6 inches), in the lower 19 centimetres (7.4 inches). 
 Valentin found that in man, during the deepest inspiration, the chest on a level 
 with the groove in the heart was increased about ^ to \, while Sibson estimates 
 the increase at the level of the nipple to be ^. 
 
 Thoracometer. — In order to obtain a knowledge of the degree of movement — rising or falling 
 — of the chest wall during respiration, various instruments have been invented. The thoracometer 
 of Sibson (Fig. 136) measures the elevation in different parts of the sternum. It consists of two 
 metallic bars placed at right angles to each other; one of them, A, is placed on the vertebral 
 column. On B there is placed a movable transverse bar, C, which carries on its free end a toothed 
 rod, Z, directed downward. The lower end of this rod is provided with a pad which rests on the 
 sternum, while its toothed edge drives a small wheel which moves an index, whose excursions are 
 indicated on a circle with a scale attached to it. 
 
 The Cyrtometer of Woillez is very useful. A brass chain, composed of movable links, is 
 applied in a definite direction to part of the chest wall, e. g., transversely on a level with the nipple, 
 or vertically upon the mammillary or axillary lines anteriorly. There are freely movable links at 
 two parts, which permit the chain to be easily removed, so that as a whole it still retains its form. 
 The chain is laid upon a sheet of paper, and a line drawn with a pencil around its inner margin 
 gives the form of the thorax (Fig. 135). [A lead wire answers the same purpose.] 
 
 Curve taken with the cyrtometer. Left side of the chest 
 retracted in a girl twelve years of age (Eickhorst). 
 
202 
 
 LIMITS OF THE LUNGS. 
 
 Limits of the Lungs. — The extent and boundaries of the lungs are ascer- 
 tained in the living subject by means of percussion, which consists in lightly- 
 tapping the chest wall by means of a hammer (percussion hammer). A small 
 
 Fig. 136. 
 
 Sibson's thoracometer. 
 
 Fig. 137. 
 
 I 
 
 Topography of the lungs and heart during inspiration and expiration {v. Dusck). k, I, upward limit ot margin 01 
 lung during deepest expiration; m, n, lower limit during deepest inspiration; t, t', t", triangular area where the 
 heart is uncovered by lung, dull percussion sound ; d, d', cP' , muffled percussion sound ; i, r, anterior margin of 
 left lung reaches this line during deep inspiration, and during deep expiration it recedes as far as^,^. 
 
 ivory or bony plate (pleximeter), held in the left hand, is laid on the chest, and 
 the hammer is made to strike this plate, whereby a sound is emitted, which sound 
 varies with the condition of the subjacent lung tissue. Whenever the lung sub- 
 
PATHOLOGICAL VARIATIONS OF THE PERCUSSION SOUNDS. 203 
 
 stance in contact with the chest wall contains air, a clear resonant tone or sound 
 — such as is obtained by striking a vessel containing air, a clear percussion sound 
 — is obtained. Where the lung does not contain air, a dull sound — like striking 
 a limb — is obtained. If the parts containing air be very thin, or are only partially 
 filled with air, the sound is "muffled." 
 
 Fig. 137 indicates the relations of the lungs to the anterior surface of the chest. 
 The apices of the lungs reach 3 to 7 centimetres (1.1 to 2.7 inches) above the 
 clavicles anteriorly, while posteriorly they extend from the spines of the scapulae 
 as high as the seventh spinous process. The lower margin of the right lung in the 
 passive position (moderate expiration) of the chest, commences at the right margin 
 of the sternum at the insertion of the sixth rib, runs under the right nipple, nearly 
 parallel to the upper border of the sixth rib, and descends a little in the axillary 
 line, to the upper margin of the seventh rib. On the left side (apart from the 
 position of the heart), the lower limit reaches as far down anteriorly as the right. 
 In Fig. 137 the line a, t, b, shows the lowest limit of the passive lungs. Posteri- 
 orly, both lungs reach as far down as the tenth rib. During the deepest inspiration, 
 the lungs descend anteriorly as far as between the sixth and seventh ribs, and 
 posteriorly to the eleventh rib — whereby the diaphragm is separated from the 
 thoracic wall (Fig. 133). During the deepest expiration, the lower margins of the 
 lungs are elevated almost as much as they descend during inspiration. In Fig. 
 137, m, n, indicates the margin of the right lung during deep inspiration ; h, I, 
 during deep expiration. 
 
 It is important to observe the relation of the margin of the left lung to the heart. 
 In Fig. 137 a somewhat triangular space, reaching from the middle of the point 
 of insertion of the fourth rib to the sixth rib on the left side of the sternum, is 
 indicated. In the passive chest, the heart lies in contact with the thoracic wall 
 in this triangular area (§ 56). This area is represented by the triangle /. f, t" , 
 and percussion over it gives a dull sound (superficial dullness). 
 
 In the area of the larger triangle d, d, d" , where the heart is separated from the 
 chest wall by the thin anterior margins of the lung, percussion gives a muffled 
 sound, while further outward a clear lung percussion sound is obtained. During 
 deep inspiration, the inner margin of the left lung reaches over the heart as far as 
 the insertion of the mediastinum, whereby the dull sound is limited to the smallest 
 triangle, t, i, i '. Conversely, during very complete expiration, the margin of the 
 lung recedes so far that the cardiac dullness embraces the space, /, e, J . 
 
 115. PATHOLOGICAL VARIATIONS OF THE PERCUSSION SOUNDS.— 
 Abnormal Dullness. — The normal clear resonant percussion sound of the lungs becomes muffled 
 when infiltration takes place into the lungs, so as to diminish the normal amount of air within them, 
 or when the lungs are compressed from without, e. g., by effusion of blood into the pleura. The 
 percussion sound becomes clearer when the chest wall is very thin, as in spare individuals, during 
 very deep inspiration, and especially in emphysema, where the air vesicles of certain parts of the 
 lung (apices and margins) become greatly dilated. 
 
 The pitch of the percussion sound ought also to be noted. It depends upon the greater or less 
 tension of the elastic pulmonary tissue, and on the elasticity of the thoracic wall. The tension of 
 the elastic tissue is increased during inspiration and diminished during expiration, so that even under 
 physiological conditions the pitch of the sound varies. 
 
 The sound is said to be tympanitic (Skoda) when it has a musical quality resembling in its 
 timbre the sound produced on a drum, and when it has a slight variation in pitch. If a caoutchouc 
 ball be placed near the ear, on tapping it gently, a well-marked tympanitic sound is heard, and the 
 sound is of higher pitch the smaller the diameter of the ball. A tympanitic sound is always pro 
 duced on tapping the trachea in the neck. A tympanitic sound produced over the chest is always 
 indicative of a diseased condition. It occurs in cases of cavities or vomicae within the substance of 
 the lung (the sound becomes deeper when the mouth, or better, the mouth and nose, are closed), 
 when air is present in one pleural cavity, as well as in conditions where the tension of the pulmon- 
 ary tissues is diminished. The tympanitic sound resembles the metallic tinkling which is heard in 
 large pathological cavities in the lungs, or which occurs when the pleural cavity contains air, and 
 when the conditions which permit a more uniform reflection of the sound waves within the cavity 
 are present. 
 
 [When a cavity, freely communicating with a large bronchus, exists in the upper and anterior 
 
204 PATHOLOGICAL RESPIRATORY SOUNDS. 
 
 part of the lung, a peculiar " cracked-pot " sound is heard on percussing over the part. Some 
 notion of this sound may be obtained by clasping the two hands so as to bring the palms nearly 
 together, leaving an air space between, and then striking them on the knee. When percussion is 
 made over a large cavity communicating with a bronchus, some of the air is expelled, and the sound 
 thereby emitted is blended with the fundamental note of the air in the cavity itself, the combination 
 of these two sounds thus producing the " cracked-pot " sound.] 
 
 Resistance. — When percussing a chest, we may determine whether the substance lying under 
 the portion of the chest under examination presents great or small resistance to the blow, either of 
 the percussion hammer or of the tips of the fingers, as the case may be, [e. g., in great pleuritic 
 effusion exerting much pressure on, and so distending the thorax walls] . 
 
 Phonometry. — If the stem of a vibrating tuning-fork be placed on the chest wall over a part 
 containing air, its sound is intensified ; but if it be placed over a portion of the lung which contains 
 little or no air its sound is enfeebled {yon Baas) . 
 
 Historical. — The actual discoverer of the art of percussion was Auenbrugger (f 1809). Piorry 
 and Skoda developed the art and theory of percussion, while Skoda originated and developed the 
 physical theory (1839). 
 
 116. THE NORMAL RESPIRATORY SOUNDS.— Normal Ves- 
 icular Sound. — If the ear directly, or through the medium of a stethoscope, be 
 placed in connection with the chest-wall, we hear over the entire area, where the 
 lung is in contact with the chest, the so-called " vesicular " sound, which is audi- 
 ble during inspiration, and its typical characters may be studied by listening in the 
 infrascapular region in an adult. It is a fine sighing or breezy sound [which 
 gradually increases in intensity until it reaches a maximum, and falls away before 
 expiration begins]. It is said to be caused by the sudden dilatation of the air 
 vesicles (hence "vesicular") during inspiration, and it is also ascribed to the 
 friction of the current of air entering the alveoli. The sound has, at one time, 
 a soft, at another, a sharper character ; the latter occurs constantly in children up 
 to 12 years of age. In their case, the sound is sharper, because the air, in enter- 
 ing vesicles one-third narrower, is subjected to greater friction. [This is followed 
 by an expiratory sound, which may be absent during quiet breathing. It is a feeble, 
 sighing sound, of an indistinct, soft character, caused by the air passing out of the 
 air vesicles, is three or four times shorter than the inspiratory, is loudest at first, 
 and soon disappears, the latter part of the expiratory act giving rise to no audible 
 sound. Its absence is not a sign of disease, but when it is prolonged and loud, 
 suspicion is aroused.] 
 
 Bronchial Respiration. — Within the larger air passages — larynx, trachea, 
 bronchi — during inspiration and expiration, there are loud, rough, harsh sounds 
 like a sharp h or ch — the "bronchial" — the laryngeal, tracheal, or "tubular" 
 sound, or breathing. [In normal bronchial breathing, as heard over the trachea, 
 there is a pause between the inspiratory and expiratory sounds, which are of nearly 
 equal duration and of about the same intensity throughout.] These sounds are also 
 heard between the scapulae, at the level of the fourth dorsal vertebra (bifurcation, 
 of trachea), and they occur also during expiration, being slightly louder on the 
 right side, owing to the slightly greater calibre of the right bronchus. 
 
 At all other parts of the chest, the vesicular sound obscures the tubular or bron- 
 chial sound. If the air vesicles are deprived of their air, the tubular breathing 
 becomes distinct. 
 
 It is asserted that, when lungs containing air are placed over the trachea, the tubular sound there 
 produced becomes vesicular. In this case, we must suppose that the vesicular sound arises from 
 the tubular breathing becoming weakened, and being- acoustically altered, by being conducted 
 through the lung alveoli (Baas, Penzoldt). A sighing sound is often produced at the apertures of 
 the nose and mouth during forced respiration. 
 
 117. PATHOLOGICAL RESPIRATORY SOUNDS.— Historical.— Although several 
 abnormal sounds in connection with diseases of the respiratory organs were known to Hippocrates 
 (succussion sound, friction and several catarrhal sounds) still, Laennec was the discoverer of the 
 method of auscultation (1816), while Skoda greatly extended our knowledge of its facts. 
 
 [The breath sounds heard in disease may be merely modifications of the normal vesicular or 
 bronchial sounds, or new sounds, such as friction sounds, rales or rhonchi.] 
 
 [Puerile Breathing is merely an exaggerated vesicular sound, so called because it resembles 
 
PRESSURE IN THE AIR PASSAGES DURING RESPIRATION. 205 
 
 the louder vesicular sound heard in children. It occurs when some part of the lung is unable to 
 act, and there is, as it were, extra work of the other parts to compensate, and thus the sound is 
 exaggerated.] 
 
 (i) Bronchial or Tubular Breathing occurs over the entire area of the lung, either when the 
 air vesicles are devoid of air, which may be caused by the exudation of fluid or solid constituents, 
 or when the lungs are compressed from without. In both cases vesicular sounds disappear, and the 
 condensed or solidified lung tissue conducts the tubular sound of the large bronchi to the surface of 
 the chest. [The sound heard over a hepatized lobe of the lung in pneumonia is a typical example.] 
 It also occurs in large cavities, with resistant' walls near the surface of the lung, provided these 
 cavities communicate with a large bronchus. [In this case it is termed Cavernous Breathing] . 
 
 (2) The amphoric sound is compared to that produced by blowing over the mouth of an empty 
 bottle. It occurs either when a cavity — at least the size of the fist — exists in the lung, which is so 
 blown into during respiration that a peculiar amphoric-like sound, with a metallic timbre called 
 metallic tinkling, is produced ; or when the lung still contains air, and is capable of expansion ; 
 as there is still air in the pleural cavity, it acts as a resonator, and causes an amphoric sound, 
 simultaneous with the change of air in the lungs. [The amphoric sound or echo and metallic tink- 
 ling are the only certain signs of the existence of a cavity in the lung.] 
 
 (3) If obstruction occurs in the course of the air passages of the lungs, various results may 
 accrue, according to the nature of the resistance : (a) owing to various causes, e. g., in the apices 
 of the lungs there may be partial swelling of the walls of the air tubes or infiltration into the air 
 cells which hinders the regular supply of air. In these cases, parts of the lung are not supplied 
 with air continuously; it only reaches them periodically. In these cases a cog-wheel sound 
 occurs. A similar sound may be heard occasionally in a. normal lung, when the muscles of the 
 chest contract in a periodic spasmodic manner, (d) When the air entering large bronchi causes the 
 formation of bubbles in the mucus which may have accumulated there, " mucous rales " are pro- 
 duced. They also occur in small spaces when the walls are separated from their fluid contents by 
 the air entering during inspiration, or when the walls, being adherent to each other, are suddenly 
 pulled asunder. The rales are distinguished as moist (when the contents are fluid), or as dry (when 
 the contents are sticky) ; they may be inspiratory, expiratory or continuous, or they may be coarse 
 or fine ; further, there is the very fine crepitation or crackling sound, and lastly, the metallic tink- 
 ling caused in large cavities through resonance. [Crepitation or Vesicular Rales are fine crepi- 
 tating sounds like those produced by rubbing a lock of hair between the fingers near one's ear ; they 
 occur only during inspiration, and are a proof that some air is entering the air vesicles. It is heard 
 in its typical form during the first stage of pneumonia, and seems to be produced by the bursting of 
 minute bubbles of air in a fluid.] (c) When the mucous membrane of the bronchi is greatly 
 swollen, or is so covered with viscid mucus that the air must force its way through, deep, sonorous 
 rhonchi (rhonchi sonori) may occur in the large air passages, and clear, shrill, sibilant sounds 
 (rhonchi sibilantes) in the smaller ones. [Rhonchi are usually due to catarrh or to affections of the 
 bronchial mucous membrane or bronchitis.] When there is extensive bronchial catarrh, not unfre- 
 quently we feel the chest-wall vibrating with the rale sounds (Bronchial fremitus). 
 
 (4) If fluid and air occur together in one pleural cavity in which the lung is collapsed, on shak- 
 ing the person's thorax vigorously, we hear a sound such as is produced when air and water are 
 shaken together in a bottle. This is the succussion sound of Hippocrates. Much more rarely, 
 this sound is heard under similar conditions in large pulmonary cavities. 
 
 (5) Pleural Friction. — When the two opposed surfaces of the pleura are inflamed, have 
 become soft, and are covered with exudation, they move over each other during respiration, and in 
 doing so give rise to friction sounds, which can be felt (often by the patient himself), and can also 
 be heard. The sound is comparable to the sound produced by bending new leather. 
 
 (6) Pectoral Fremitus. — When we speak or sing in a loud tone, the walls of the chest vibrate, 
 because the vibration of the vocal cords is propagated throughout the entire bronchial ramifications. 
 The vibration is, of course, greatest near the trachea and large bronchi. The ear cannot detect the 
 sounds distinctly; If there be much exudation or air in the pleura, or great accumulation of mucus 
 in the bronchi, the pectoral fremitus is diminished or altogether absent. [In health, when a person 
 speaks, the vocal resonance over the trachea, although loud, may be inarticulate, and on listening 
 over the sternum the sound is diminished and quite inarticulate ; while over the chest-wall gener- 
 ally, the sound, though distinct, is feeble.] 
 
 All conditions which cause bronchial breathing increase the pectoral fremitus. Under normal 
 circumstances, therefore, it is louder where bronchial breathing is heard normally. The ear hears 
 an intensified sound, which is called bronchophony [which is a sound like that heard normally 
 over the trachea or bronchi, but audible over the vesicular lung tissue. The conditions that cause it 
 are the same as those on which bronchial breathing depends, so that it is heard in pneumonia and 
 phthisis. If, through effusion into the pleura or inflammatory processes in the lung tissue, the 
 bronchi are pressed flat, a peculiar bleating sound (aegophony) may be heard.] 
 
 118. PRESSURE IN THE AIR PASSAGES AND THORAX 
 DURING RESPIRATION.— Respiratory Pressure.— If a manometer 
 be tied into the trachea of an animal, so that the respiration goes on completely 
 
206 PRESSURE IN THE AIR PASSAGES DURING RESPIRATION. 
 
 undisturbed, /. e., normal respiration, during every inspiration there is a nega- 
 tive pressure ( — 3 mm. Hg) and during expiration a positive pressure (Donders). 
 Donders placed the U-shaped manometer tube in one nostril, closed his mouth, 
 leaving the other nostril open, and respired quietly. During every quiet inspira- 
 tion the mercury showed a negative pressure of — 1 mm., and during expiration, 
 a positive pressure of 2-3 mm. (Hg). 
 
 Forced Respiration. — As soon as the air was inspired or expired with greater 
 force, the variations in pressure became very much greater, e.g., during speaking, 
 singing and coughing. The inspiratory pressure was = — 57 mm. (36-74), the 
 greatest expiratory pressure -f- 87 (82-100) mm. Hg {Donders). The pressure of 
 forced expiration therefore, is 30 mm. greater than the inspiratory pressure. 
 
 Resistance to Inspiration. — Notwithstanding this, we must not conclude 
 that the expiratory muscles act more powerfully than the inspiratory ; for during 
 inspiration, a variety of resistances have to be overcome, so that after these have 
 been met, there is only a residue of the force for the aspiration of the mercury. 
 The resistances to be overcome by the inspiratory muscles are — (1) The elastic 
 tension of the lungs, which during the deepest expirations = 6 mm. ; during the 
 deepest inspirations = 30 mm. Hg (§ 107). (2) The raising of the weight of 
 the chest. (3) The elastic torsion of the costal cartilages. (4) The depression 
 of the abdominal contents, and the elastic distention of the abdominal walls. All 
 these not inconsiderable resistances, which the inspiratory muscles have to over- 
 come, act during expiration, and aid the expiratory muscles. The forces con- 
 cerned in inspiration are decidedly much greater than those of expiration. 
 
 Intra-thoracic Pressure. — As the lungs within the chest, in virtue of their 
 elasticity, continually strive to collapse, necessarily they must cause a negative 
 pressure within the chest. This amounts in dogs during inspiration, to — 7.1 to 
 — 7.5 mm. Hg, and during expiration to — 4 mm. Hg (Heynsius). The cor- 
 responding values for man have been estimated at — 4.5 mm. Hg, and — 3 mm. 
 Hg, by Hutchinson. 
 
 [We must distinguish between respiratory pressure of the air within the respiratory passages, 
 and the intra-thoracic pressure. The former is the same as the atmospheric pressure when the chest 
 is passive, but less than it as the chest is being enlarged, and greater than it when it is being dimin- 
 ished in size. The intra-thoracic pressure is the pressure within the chest, but outside the lungs, 
 i.e., in the pleura, mediastinum, etc. It is negative, i.e., less than the atmospheric pressure, and 
 must vary with the degree of distention of the lungs.] 
 
 [Methods. — A direct estimation w,as made by Adamkiewicz and Jacobson. A trocar with its 
 stylette was forced into the fourth left intercostal space near the sternum and pushed into the peri- 
 cardium (sheep). The stylette was then withdrawn, and the trocar connected with a manometer, 
 and the negative pressure of — 3 to — 5 mm. Hg was obtained. During violent dyspnoea it was 
 — 9 mm. Hg. Rosenthal introduced an oesophageal sound with an elastic ampulla on its lower end 
 into the oesophagus, so that the ampulla came to lie opposite the posterior mediastinum. The sound 
 was connected with a registering tambour or manometer. During inspiration the manometer fell, 
 and during expiration it rose.] 
 
 Even the greatest inspiratory or expiratory pressure is always much less than the blood pressure 
 in the large arteries ; but if the pressure be calculated upon the entire respiratory surface of the 
 thorax, very considerable results are obtained. 
 
 Pneumatometer. — This instrument of Waldenburg is merely a mercurial manometer fixed to a 
 stand, and connected to an elastic tube with a suitable mouth piece, which is fitted over the mouth 
 and nose, while the variations of the Hg can be read off on a scale. [In the male, the expiratory 
 pressure is 90-120 mm. Hg, and the respiratory 70-100. The relations of the pressure during expi- 
 ration and inspiration are more important than the absolute pressure.] The inspiratory pressure is 
 diminished in nearly all diseases where the expansion of the lung is impaired [phthisis], or the 
 expiratory pressure is diminished, as in emphysema and asthma. 
 
 Effects of the first Respiration on the Thorax. — Until birth, the airless lungs are completely 
 collapsed (atelectic) within the chest, and fill it, so that on opening the chest in a dead foetus, pneumo- 
 thorax does not occur [Bernstein). Supposing, however, respiration to have been fully established 
 after birth, and air to have freely entered the lungs, if a manometer be placed in connection with 
 the trachea and the chest be opened, the manometer will register a pressure of 6 mm. Hg, due to 
 the collapse of the elastic lungs. Bernstein supposes that the thorax assumes a new permanent form, 
 due to the first respiratory distention; it is as if, owing to the respiratory elevation of the ribs, the 
 thorax had become permanently too large for the lungs, which are, therefore, kept permanently dis- 
 
PECULIARLY MODIFIED RESPIRATORY MOVEMENTS. 207 
 
 tended, but collapse as soon as air passes into the pleura. When a lung has once been filled with 
 air, it cannot be emptied by pressure from without, as the small bronchi are compressed before the air 
 can pass out of the alveoli. The expiratory muscles cannot possibly expel all the air from the lungs, 
 while the inspiratory muscular force is sufficient to distend the lungs beyond their elastic equilibrium. 
 Inspiration distends the lungs, increasing their elastic tension, while expiration diminishes the tension 
 without abolishing it. 
 
 119. APPENDIX TO RESPIRATION.— Nasal Breathing.— During 
 
 quiet respiration, we usually breathe — or ought to breathe — through the nostrils, 
 the mouth being closed. The current of air passes through the pharyngo-nasal 
 cavity — so that in its course during inspiration, it is (1) warmed and rendered 
 moist, and thus irritation of the mucous membrane of the air passages by the cold 
 air is prevented; (2) small particles of soot, or other foreign substances in the air, 
 adhere to, and become embedded in the mucus covering the somewhat tortuous 
 walls of the respiratory passages, and are carried outward by the agency of the 
 ciliated epithelium of the respiratory passages ; (3) disagreeable odors and certain 
 impurities are detected by the sense of smell. 
 
 If a lung be inflated, air constantly passes through the walls of the alveoli and trachea. This 
 also occurs during violent expiratory efforts (cutaneous emphysema in whooping cough), so that 
 pneumothorax may occur [J. R. Ewald and Koberts). 
 
 Pulmonary CEdema, or the exudation of lymph or serum into the pulmonary alveoli, occurs — 
 (1) When there is very great resistance to the blood stream in the aorta or its branches, e.g., by 
 ligaturing all the arteries going to the head (Sig. Mayer), or the arch of the aorta, so that only one 
 carotid remains pervious [Welch). (2) When the pulmonary veins are occluded. (3) When the 
 left ventricle, owing to mechanical injury, ceases to beat, while the right ventricle goes on contract- 
 ing ({! 47). These conditions produce at the same time anaemia of the vasomotor centre which 
 results in stimulation of that centre, and consequent contraction of all the small arteries. Thus the 
 blood stream through the veins to the right heart is favored, and this in its turn favors the produc- 
 tion of cedema of the lungs. 
 
 120. PECULIARLY MODIFIED RESPIRATORY MOVEMENTS.— (1) Cough- 
 ing. — Consists in a sudden violent expiratory explosion after a previous deep inspiration and closure 
 of the glottis, whereby the glottis is forced open, and any substance, fluid, gaseous, or solid, in 
 contact with the respiratory mucous membrane is violently ejected through the open mouth. It is 
 produced voluntarily or reflexly; in the latter case, it can be controlled by the will only to a limited 
 extent. 
 
 [Causes. — A cough may be discharged reflexly from a large number of surfaces : (1) A draught 
 of cold air striking the skin, especially of the upper part of the body. This may cause congestion 
 of blood in the air passages, this in turn exciting the cough. (2) More frequently it is discharged 
 from the respiratory mucous membrane, especially of the larynx, the sensory branches of the vagus 
 and the superior laryngeal nerve being the afferent nerves. A cough cannot be discharged from 
 every part of the larynx, thus there is none from the true vocal cords, but only from the glottis 
 respiratoria. All other parts of the larynx are inactive, and so is the trachea as far as the bifurca- 
 tion, where stimulation excites cough \Kohts, Vulpian). (3) Sometimes an offending body, such 
 as a pea or inspissated cerumen in the external auditory meatus, gives rise to coughing, the afferent 
 nerve being the auricular branch of the vagus. (4) There seems to be no doubt that there may be 
 a "gastric or stomach cough" produced by stimulation of the gastric branches of the vagus, espe- 
 cially in cases of indigestion, accompanied by irritation of the larynx and trachea. (5) Irritation of 
 the costal pleura and even of the cesophagus (Kohts). (6) Irritation of some parts of the nose. 
 (7) Sometimes also from irritation of the pharynx, as by an elongated uvula. (8) In some diseases 
 of the liver, spleen, and generative organs, when pressure is exerted on these parts.] 
 
 (2) Hawking, or clearing the throat. — An expiratory current is forced in a continuous stream 
 through the narrow space between the root of the tongue and the depressed soft palate, in order to 
 assist in the removal of foreign bodies. When the act is carried out periodically the closed glottis 
 is suddenly forced open, and it is comparable to a voluntary gentle cough. This act can only be 
 produced voluntarily. 
 
 (3) Sneezing consists in a sudden violent expiratory blast through the nose, for the removal of 
 mucus or foreign bodies (the mouth being rarely open) after a simple or repeated spasm-like inspi- 
 ration — the glottis remaining open. It is usually caused reflexly by stimulation of sensory nerve 
 fibres of the nose [nasal branch of the fifth nerve], or by sudden exposure to a bright light (Cassius 
 Felix, A.D. 97) [the afferent nerve is the optic]. This reflex act maybe interfered with to a certain 
 extent, or even prevented, by stimulation of sensory nerves, or firmly compressing the nose where 
 the nasal nerve issues. The continued use of sternutatories, as in persons who take snuff, dulls the 
 sensory nerves, so that they no longer act when stimulated reflexly. 
 
 [Sternutatories or Errhines, such as powdered ipecacuanha, snuff, and euphorbium, also 
 
208 PECULIARLY MODIFIED RESPIRATORY MOVEMENTS. 
 
 increase the secretion from the nasal glands. The afferent impulse sent to the respiratory centre 
 also affects the vasomotor centre, so that even when sneezing does not occur the blood pressure 
 throughout the body is raised.] 
 
 W4) Snoring occurs during respiration through the open. mouth, whereby the inspiratory and 
 expiratory stream of air throws the uvula and soft palate into vibration. It is involuntary, and 
 usually occurs during sleep, but it may be produced voluntarily. 
 
 (5) Gargling consists in the slow passage of the expiratory air current in the form of bubbles 
 through a fluid lying between the tongue and the soft palate, when the head is held backward. It 
 is a voluntary act. 
 
 (6) Crying, caused by emotional conditions, consists in short, deep inspirations, long expirations 
 with the glottis narrowed, relaxed facial and jaw muscles, secretion of tears, often combined with 
 plaintive inarticulate expressions. When crying is long continued, sudden and spasmodic involun- 
 tary contractions of the diaphragm occur, which cause the inspiratory sounds in the pharynx and 
 larynx known as sobbing. This is an involuntary act. 
 
 (7) Sighing is a prolonged inspiration, usually combined with a plaintive sound, often caused 
 involuntarily, owing to painful or unpleasant recollections. 
 
 (8) Laughing is due to short, rapid expiratory blasts through the tense vocal cords, which cause 
 a clear tone, and there are characteristic inarticulate sounds in the larynx, with vibrations of the soft 
 palate. The mouth is usually open, and the countenance has a characteristic expression, owing to 
 the action of the M. zygomaticus major. It is usually involuntary, and can only be suppressed, to 
 a certain degree, by the will (by forcibly closing the mouth and stopping respiration). 
 
 (9) Yawning is a prolonged deep inspiration occurring after successive attempts at numerous 
 inspirations — the mouth, fauces and glottis being wide open; expiration shorter — both acts often 
 
 ■ accompanied by prolonged characteristic sounds. It is quite involuntary, and is usually excited by 
 drowsiness or ennui. 
 
 [(10) Hiccough is due to a spasmodic involuntary contraction of the diaphragm, causing an 
 inspiration, which is arrested by the sudden closure of the glottis, so that a characteristic sound is 
 emitted. Not unfrequently it is due to irritation of the gastric mucous membrane, and sometimes it 
 is a very troublesome symptom in uraemic poisoning.] 
 
CHEMISTRY OF RESPIRATION. 
 
 121. QUANTITATIVE ESTIMATION OF CARBONIC ACID, OXYGEN, AND 
 WATERY VAPOR.— I. Estimation of C0 2 — 1. The volume of C0 2 is estimated by means 
 of the anthracometer (Fig. 138, II) of Vierordt. The volume of gas is collected in a graduated 
 tube, r r, provided with a bulb at one end (previously filled with water and carefully calibrated, 
 i. e., the exact amount which each part of the tube contains is accurately measured), and the tube is 
 closed. The lower end has a stop-cock, h, and to this is screwed a flask, n, completely filled with 
 a solution of caustic potash ; the stop-cock is then opened, the potash solution is allowed to ascend 
 into the tube, which is moved about until all the C0 2 unites with the potash to form potassium 
 carbonate. Hold the tube vertically and allow the potash to run back into the flask, close the stop- 
 cock, and remove the bottle with the potash. Place the stop-cock under water, open it and allow 
 the water to ascend in the tube, when the space in the tube occupied by the fluid indicates the volume 
 of C0 2 which is combined with the potash. 
 
 2. By Weight. — A large quantity of the mixture of gases which has to be investigated is made to 
 pass through a Liebig's bulb filled with caustic potash. The potash apparatus having been carefully 
 weighed beforehand, the increase of weight indicates the amount of C0 2 which has been taken up 
 by the potash from the air passed through it. 
 
 3. By Titration. — A large volume of the air to be investigated is conducted through a known 
 volume of a solution of barium hydrate. The CO z unites with the barium and forms barium car- 
 bonate. The fluid is neutralized with a standard solution of oxalic acid, and the more barium that 
 has united with the C0 2 the smaller will be the amount of oxalic acid used, and vice versa. 
 
 II. Estimation of Oxygen. — According to volume — (a) By the union of the O with potassium 
 pyrogallate. The same procedure is adopted as for the estimation of C0 2 , only the flask, n, is 
 filled with the pyrogallate solution instead of potash, [b) By explosion in an eudiometer (see Blood 
 gases, \ 35). 
 
 III. Estimation of Watery Vapor. — The air to be investigated is passed through a bulb con- 
 taining concentrated sulphuric acid, or through a tube filled with pieces of calcium chloride. The 
 amount of water is directly indicated by the increase of weight. 
 
 122. METHODS OF INVESTIGATION.— I. Collecting the Expired Air.— (1) The 
 air expired may be collected in the cylinder of the spirometer (jj 108), which is suspended in con- 
 centrated salt solution, to avoid the absorption of C0 2 . 
 
 The apparatus of Andral and Gavarret is thus used : The operator breathed several times into 
 a capacious cylinder (Fig. 138). A mouth piece (M) was placed air tight over the mouth,[while the 
 nostrils were closed. The direction of the respiratory current was regulated by two so-called 
 " Mailer's Valves " (mercurial), (a and b). With every inspiration, the bottle or valve, a (filled 
 below with Hg and hermetically closed above), permits the air inspired to pass to the lungs — during 
 every expiration, the expired air can pass only through b to the collecting cylinder, C. 
 
 (2) If the gases given off by the skin are to be collected, a limb, or whatever part is to be inves- 
 tigated, is secured in a closed vessel, and the gases so obtained are analyzed. 
 
 II. The most important apparatus for this purpose are those of — (a) Scharling (Fig. 139), which 
 consists of a closed box, A, of sufficient size to contain a man. It has two openings — an entrance 
 opening, z, and an exit, b. The latter is connected with an aspirator, C, a large barrel filled with 
 water. When the stop-cock, h, is opened, and the water flows out of the barrel, fresh air will rush 
 in continuously into the box, A, and the air mixed with the expired gases will be drawn toward C. 
 A Liebig's bulb, d, filled with caustic potash, is connected with the entrance tube, z, through which 
 the in-going air must pass, whereby it is completely deprived of C0 2 , so that the person experimented 
 on is supplied with air free from C0 2 . The air passing out by the exit tube, b, has, to pass first 
 through e, where it gives up its watery vapor to sulphuric acid, whereby the amount of watery vapor 
 is estimated by the increase of the weight of the apparatus, e. Afterward, the air passes through a 
 bulb,/, containing caustic potash, which absorbs all the C0 2 , while the tube, g, filled with sulphuric 
 acid, absorbs any watery vapor that may have come from /. The increase of weight of /and g 
 indicate the amount of C0 2 . The total volume of air used is known from the capacity of C. 
 
 (b) Regnault and Reiset's Apparatus is more complicated, and is used when it is necessary to 
 keep animals for some time under observation in a bell jar. It consists (Fig. 140) of a globe, R, 
 in which is placed the dog to be experimented on. Around this is placed a cylinder, g g (provided 
 with a thermometer, /), which may be used for calorimetric experiments. A tube, c, leads into the 
 
 14 209 
 
210 
 
 APPARATUS FOR EXAMINING RESPIRED AIR. 
 
 globe, R ; through this tube passes a known quantity of pure oxygen (Fig. 140, O). To absorb 
 any trace of C0 2 , a vessel containing potash (Fig. 140, C0 2 ) is placed in the course of the tube. 
 The vessel for measuring the O is emptied toward R, through a solution of calcium chloride from a 
 large pan (CaCl 2 ) provided with large flasks. Two tubes, d and e, lead from R, and are united by 
 caoutchouc tubes with the potash bulbs (KOH, 'Koh), which can be raised or depressed alternately 
 by means of the beam, W. In this way they aspirate alternately the air from R, and the caustic 
 
 Fig. J38. 
 
 © 
 
 ^ 
 
 a 
 
 I. Apparatus of Andral and Gavarret for collecting the expired air. C, large cylinder, to collect the air expired ; P, 
 weight, to balance cylinder ; a, b, two Mftller's valves ; M, mouth piece. II. Anthracometer of Vierordt. 
 
 potash absorbs the C0 2 . The increase of weight of these flasks after the experiment indicates the 
 amount of, C0 2 expired. The manometer,/ - , shows whether there is a difference of the pressure 
 outside and inside the globe, R. 
 
 (c) v. Pettenkofer has invented the most complete apparatus (Fig. 141). It consists of a cham- 
 ber, Z, with metallic walls, and provided with a door and a window. At a is an opening for the 
 
 Fig. 139. 
 
 Respiratory Apparatus of Scharling. d, bulb containing caustic potash, to absorb CO a from in-going air ; A, box for 
 man or animal experimented on ; e and r, tubes containing sulphuric acid, to absorb watery vapor ; f, potash 
 bulb, to absorb C0 2 given off; C, vessel filled with water, to aspirate air through the foregoing system; h, 
 stop-cock. 
 
 admission of air, while a large double suction pump, P P a (driven by means of a steam engine) 
 continually renews the air within the chamber. The air passes into a vessel, b, filled with pumice 
 stone saturated with sulphuric acid, in which it is dried ; it then passes through a large gas meter, c, 
 which measures the total amount of air passing through it. 
 
 After the air is measured, it is emptied outward by means of the pump, P Pj. From the chief 
 exit tube, x, of the chamber, provided with a small manometer, q, a narrow laterally placed tube, 
 
APPARATUS FOR EXAMINING RESPIRED AIR. 
 
 211 
 
 n, passes, conducting a small secondary stream, which is chemically investigated. This current 
 passes through the suction apparatus, M Mj (constructed on the principle of Miiller's mercurial 
 valve, and driven by a steam engine). Before reaching this apparatus, the air passes through the 
 
 Fig, 
 
 Scheme of the Respiration Apparatus of Regnault and Reiset. R, globe for animal; g g f outer casing for R, pro- 
 vided with a thermometer, t ; d and e , exit tubes to movable potash bulbs, KOH and K<?A ; O, in-going oxygen ; 
 C0 2 , vessel, to absorb any carbonic acid ; CaCl 3 , apparatus for estimating the amount of O supplied ; /, 
 manometer. 
 
 Fig. 141. 
 
 . Respiration Apparatus of v. Pettenkofer. Z, chamber for person experimented on ; x, exit tube with manometer, g ; 
 6, vessel with sulphuric acid ; C, gas meter ; P P lf pump; », secondary current, with, k, bulb; M M lt suc- 
 tion apparatus ; u, gas meter; N, stream for investigating air before it enters Z. 
 
212 COMPOSITION OF EXPIRED AIR. 
 
 bulb, K, filled with sulphuric acid, whose increase in weight indicates the amount of watery vapor. 
 After passing through M M 1? it goes through the tube, R, filled with baryta solution, which takes 
 up the C0 2 . The quantity of air which passes through the accessory current, », is measured by the 
 small gas meter, u, from which it passes outward. The second accessory stream, N, enables us to 
 investigate the air before it enters the chamber, and it is arranged in exactly the same way as n . 
 
 The increase of C0 2 and H 2 in the accessory stream, n {i.e., more than in N), indicates the 
 amount of C0 2 given off by the person in the chamber, Z. 
 
 123. COMPOSITION AND PROPERTIES OF ATMOSPHERIC 
 AIR. — 1. Dry Air contains : — 
 
 Gas. By Weight. By Volume. 
 
 O, 23.015 20.96 
 
 N, 76.985 79.02 
 
 C0 2 0.03-0.034 
 
 2. Aqueous Vapor is always present in the air, but it varies greatly in amount, 
 and generally increases with the increase of the temperature of the air. In con- 
 nection with the moisture of the air we distinguish (a) the absolute moisture, i.e., 
 the quantity of watery vapor which a volume of air contains in the form of vapor ; 
 and (f), the relative moisture, i. e., the amount of watery vapor which a volume of 
 air contains with respect to its temperature. 
 
 Experience shows that people generally can breathe most comfortably in an atmosphere which is not 
 completely saturated with aqueous vapor according to its temperature, but is only saturated to the 
 extent of 7° per cent. If the air be too dry it irritates the respiratory mucous membrane ; if too 
 moist, there is a disagreeable sensation, and if it be too warm, a feeling of closeness. Hence, it is 
 important to see that the proper amount of watery vapor is present in the air of our sitting rooms, 
 bedrooms, and hospital wards. 
 
 The absolute amount of moisture varies : In towns during the day it increases with increase of 
 temperature, and diminishes when the temperature falls ; it also varies with the direction of the 
 wind, season of the year, height above sea level. 
 
 The relative amount of moisture is greatest at sunrise, least at midday ; small on high mountains ; 
 greater in winter than in summer ; larger with a south or west wind than with a north or east wind. 
 
 The air in midsummer contains absolutely three times as much watery vapor as in midwinter, 
 nevertheless the air in summer is relatively drier than the air in winter. 
 
 3. The air Expands by Heat. Rudberg found that 1000 volumes of air, at 
 o°, expanded to 1365 when heated to ioo° C. 
 
 4. The Density of the air diminishes with increase of the height above the 
 sea-level. 
 
 124. COMPOSITION OF EXPIRED AIR.— 1. The expired air contains 
 more C0 2 — in normal respiration = 4.38 vols, per cent. (3.3 to 5.5 per cent.), 
 so that it contains nearly 100 times more C0 2 than the atmospheric air. 
 
 2. It contains less O (4.782 vols, per cent, less) than the atmospheric air, i. e., 
 it contains only 16.033 vols, per cent of O. 
 
 3. Respiratory Quotient. — Hence, during respiration, more O is taken into 
 the body from the air than C0 2 is given off {Lavoisier) ; so that the volume of 
 the expired air is ( 4^ gV ) smaller than the volume of the air inspired, both being 
 calculated as dry, at the same temperature, and at the same barometric pressure. 
 The relation of the O absorbed to the C0 2 given off is 4.38 : 4.782. This is 
 expressed by the " respiratory quotient " — 
 
 C0 2 / 4-38 \ , 
 
 ~o~( = 4^2) = °- 9 ° 6 ' 
 
 4. An excessively small quantity of N is added to the expired air (Regnault .'■■ 
 and Reisef). Segen found that all the N taken in with the food did not reappear 
 in the excreta (urine and faeces), and he assumed that a small part of it was given 
 off by the lungs.. 
 
 5. During ordinary respiration, the expired air is saturated with watery 
 vapor. It is evident, therefore, that when the watery vapor in the air varies, 
 the lungs give off different quantities of water from the body. The percentage 
 of watery vapor falls during rapid respiration {Moleschoti). 
 
CONDITIONS INFLUENCING THE EXCRETION OF C0 2 . 
 
 213 
 
 6. The expired air is warmer (36. 3 C). It is very near the Fig. 
 temperature of the body, and even although the temperature of 
 the surrounding atmosphere be very variable, the temperature of 
 the expired air still remains nearly the same. 
 
 The instrument (Fig. 142) was used by Valentin and Brunner to determine the 
 temperature of the expired air. It consists of a glass tube, A, A, with a mouth 
 piece, B, and in it is a fine thermometer, C. The operator breathes through the 
 nose and expires slowly through the mouth piece into the tube. 
 
 Temperature of Temperature of the 
 
 the Air. Expired Air. 
 °C. °C 
 
 — 6.3 + 29.8 
 
 + 17-19 + 36-2-37 
 
 + 41 + 38-1 
 
 + 34 +38-5 
 
 7. The diminution of the volume of the expired air mentioned 
 under (3) is far more than compensated by the warming which the 
 inspired air undergoes in the respiratory passages, so that the 
 volume of the expired air is one-ninth greater than the air inspired. 
 
 8. A very small quantity of ammonia is found in the expired 
 air (Regnault and Reisef) = 0.0204 gramme in 24 hours (Losseri) ; 
 it is probably derived from the blood, for blood exposed to the 
 air evolves ammonia (Brucke). 
 
 ' 9. Small quantities of H and CH 4 are expired, both being ab- 
 sorbed from the intestine. In herbivora, Reiset found that 30 
 litres of CH 4 were expired in 24 hours. 
 
 125. DAILY QUANTITY OF GASES EX- 
 CHANGED. — As under normal circumstances, more O is ab- 
 sorbed than there is C0 2 given off (equal volumes of O and C0 2 
 contain equal quantities of O), a part of the O must be used for 
 other oxidation processes in the body. According to the extent 
 of these latter processes, the ratio of the O taken in to the C0 2 
 given out — 
 
 /CO 2 \ 
 
 I -q— = 0.906 normally I must vary. 
 
 The amount of C0 2 given off may be less than the "mean " above stated. 
 The quantity of C0 2 alone is not a reliable indication of the entire exchange of 
 gases during respiration ; we must estimate simultaneously the amount of O 
 absorbed, and the C0 2 given off. 
 
 126. REVIEW OF DAILY GASEOUS INCOME AND EXPEN- 
 DITURE. 
 
 Income in 24 hours. 
 Oxygen — 
 744 grms. = 516.500 c.cmtr. ( Vierordt). 
 
 (At o° C. and mean barometric pressure.) 
 
 ( Vierordt). 
 
 [Scharling). 
 
 (Liebermeister). 
 
 (Panum). 
 
 {Ranke). 
 
 ( Valentin). 
 
 ( Vierordt). 
 
 127. CONDITIONS INFLUENCING THE GASEOUS EX- 
 CHANGES. — The formation of C0 2 , in all probability, consists of two dis- 
 tinct processes. First, compounds containing C0 2 seem to be formed in the 
 tissues, which are oxidation products of substances containing carbon. The second 
 process consists in the separation of this C0 2 , which, however, takes place without 
 
 Expenditure in 24 hours. 
 Carbonic Acid — 
 
 goo grms. = 455500 c.cmtr 
 36 grms. per hour. 
 
 32.8 to 33.4 grms " " 
 34 grms. " « 
 
 3'-5 to 33 g""s. " 
 Water — 640 grms. 
 330 grms. 
 
214 
 
 CONDITIONS INFLUENCING THE EXCRETION OF C0 2 . 
 
 the absorption of O. Both processes do not always occur simultaneously, and the 
 one process may exceed the other in extent (Z. Hermann, Pfluger). 
 
 According to Schmiedeberg, the oxidation in the tissues depends upon a synthesis with the libera- 
 tion of H 2 0, the blood supplying the necessary O. 
 
 The following circumstances affect these processes : — 
 
 i. Age. — Until the body is fully developed, the C0 2 given off increases, but 
 it diminishes as the bodily energies decay. Hence, in young persons the 
 absorbed is relatively greater than the C0 2 given off; at other periods, both values 
 are pretty constant. Example : — 
 
 Age — Years. 
 
 «5 
 16 
 
 18-20 
 20-24 
 40-60 
 60-80 
 
 In 24 hours. 
 
 CO- Gram, excreted. = Carbon. 
 
 443 gram. 
 
 766 " 
 
 9S " 
 
 1003 " 
 
 1074 " 
 
 889 " 
 
 810 " 
 
 121 Carbon. 
 
 209 
 
 259 
 
 274 
 
 293 
 242 
 221 
 
 O Absorbed Gram. 
 
 375 grammes. 
 652 " 
 809 
 
 854 " 
 914 
 
 757 
 689 
 
 The absolute amount of C0 2 given off is less in children than in adults ; but if 
 the C0 2 given off be calculated with reference to body weight, then, weight for 
 weight, a child gives off twice as much C0 2 as an adult. 
 
 2. Sex. — Males, from the eighth year onward to old age, give off about one- 
 third more C0 2 than females {Andral and Gavarref). This difference is more 
 marked at puberty, when the difference may rise to one-half. After cessation of 
 the menses, there is an increase, and in old age the amount of C0 2 given off 
 diminishes. Pregnancy increases the amount, owing to causes which are easily 
 understood. 
 
 3. The Constitution. — As a general rule, muscular, energetic persons use 
 more O and excrete more C0 2 than less active persons of the same weight. 
 
 4. Alternation of Day and Night. — The C0 2 given off is diminished about 
 one-fourth during sleep {Scharling). This diminution is caused by the constant 
 heat of the surroundings (bed), darkness, absence of muscular activity, and the 
 non-taking of food (see 5, 6, 7, 9). It does not seem that any O is stored up 
 during sleep {S. Lewin). After awaking in the morning, the respirations are 
 more rapid and deeper, and thus the amount of C0 2 given off is increased. It 
 decreases during the forenoon, until dinner, at midday, causes another increase. 
 It falls during the afternoon, and increases again after supper. 
 
 During hybernation, when no food is taken, and when the respirations cease, or are enormously 
 diminished, the respiratory exchange of gases is carried out by diffusion and by the cardio-pneumatic 
 movements (§ 59). The C0 2 given off falls to f z , the O taken in to ? V of what they are in the 
 waking condition ( Valentin). Much less C0 2 is given off than O taken in, so that the body weight 
 may increase through the excess of O. 
 
 5. Temperature of the Surroundings. — Cold-blooded Animals become 
 warmer when the temperature of their environment is raised, and they give off 
 more C0 2 in this condition than when they are cooler {Spallanzani~), e.g., a frog, 
 with the temperature of the surroundings at 39 C, excreted three times as much 
 C0 2 as when the temperature was 6° C. (Moleschott). 
 
 Warm-blooded Animals behave somewhat differently when the temperature 
 of the surrounding medium is changed. When the temperature of the animal is 
 lowered thereby, there is a considerable decrease in the amount of C0 2 given off, 
 as in cold-blooded animals ; but if the temperature of the animal be increased 
 
CONDITIONS INFLUENCING THE EXCRETION OF C0 2 . 
 
 215 
 
 (also in fever), the C0 2 is increased (C. Ludwig and Sanders-Ezn). Exactly the 
 reverse obtains when the temperature of the surroundings varies, and the bodily 
 temperature remains constant. As the cold of the surrounding medium increases, 
 the processes of oxidation within the body are increased through some as yet un- 
 known reflex mechanism ; the number and depth of the respirations increase, 
 whereby more O is taken in and more C0 2 is given out {Lavoisier). A man in 
 January uses 32.2 grammes O per hour; in July, only 31.7 grammes. In animals, 
 with the temperature of the surroundings at 8° C., the C0 2 given off was one-third 
 greater than with a temperature of 38 C. When the temperature of the air 
 increases — the body temperature remaining the same — the respiratory activity and 
 the C0 2 given off diminish, while the pulse remains nearly constant {Vierordt). 
 On passing suddenly from a cold to a warm medium, the amount of C0 2 is con- 
 siderably diminished ; and, conversely, on passing from a warm to a cold medium, 
 the amount is considerably increased (§214). 
 
 6. Muscular Exercise causes a considerable increase in the C0 2 given out 
 {Scharling), which may be three times greater during walking than during rest 
 {Ed. Smith). Ludwig and Sczelkow estimated the O taken in and the C0 2 given 
 off by a rabbit during rest, and when the muscles of the hind limbs were tetanized. 
 During tetanus, the O and C0 2 were increased considerably, but in tetanized 
 animals more O was given off in the C0 2 expired than was taken up simultaneously 
 during respiration. The passive animal absorbed nearly twice as much O as the 
 amount of C0 2 given off (§ 294). 
 
 7. Taking of food causes constantly a not inconsiderable increase in the C0 2 
 given off, which depends upon the quantity taken, and the increase generally 
 occurs about an hour after the chief meal — dinner ( Vierordt). During inanition, 
 the exchange of gases diminishes considerably until death occurs {Letellier). At 
 first the C0 2 given off diminishes more quickly than the O is taken up. The 
 quality of the food influences the C0 2 given off to this extent, that substances rich 
 in carbon (carbohydrates and fats) cause a greater excretion of C0 2 than substan- 
 ces which contain less C (albumins). Regnault and Reiset found that a dog gave 
 off 79 per cent, of the O inspired after a flesh diet, and 91 per cent, after a diet 
 of starch. If easily oxidizable substances (glycerine or lactate of soda) are injected 
 into the blood, the O taken in and the C0 2 given off undergo a considerable in- 
 crease {Ludwig and Scheremetjewsky). Alcohols, tea, and ethereal oils diminish 
 the C0 2 {Prout, Vierordt). [Ed. Smith found that the effects produced by alco- 
 holic drinks varied with the nature of the spirituous liquor. Thus brandy, whisky, 
 and gin diminish the amount ; while pure alcohol, rum, ale, and porter tend to 
 increase it.] 
 
 8. The Number and Depth of Respirations have practically no influence 
 on the formation of C0 2 , or the oxidation processes within the body, these being 
 regulated by the tissues themselves, by some mechanism as yet unknown {Pfluger). 
 They have a marked effect, however, upon the removal of the already formed C0 2 
 from the body. An increase in the number of respirations (their depth remaining 
 the same), as well as an increase of their depth, the number remaining the same, 
 cause an absolute increase in the amount of C0 2 given off, which, with reference to 
 the total amount of gases exchanged, is relatively diminished. The following 
 example from Vierordt illustrates this : — 
 
 No. of Resps. 
 per min. 
 
 Vol of Air. 
 
 ■ Amount of per cent. 
 
 co 2 . _ co 2 . 
 
 Depth of Resp. 
 
 Amount of per cent. 
 
 co 2 . - co 2 . 
 
 12 
 
 24 
 48 
 96 
 
 600O 
 I2000 
 24000 
 48000 
 
 258 c. cmtr. =4.3^ 
 420 " =. 3.5 " 
 
 744 " =3-i" 
 1392 " =2.9" 
 
 500 
 IOOO 
 ISOO 
 2000 
 3OOO 
 
 21 c. cmtr. r= 4.3% 
 36 " =3.6" 
 
 St " =3-4" 
 64 " = 3.2 " 
 72 " = 1.4" 
 
216 EXCHANGES OF GASES BETWEEN THE AIR AND THE BLOOD. 
 
 g. Exposure to a bright light causes an increase in the C0 2 given off in frogs (Molescfiott, 
 1833) ; in mammals and birds (Selmi and Piacentini) ; even in frogs deprived of their lungs (Fu- 
 bini) ; or in those whose spinal cord has been divided high up (Chasanowitz). The consumption 
 of O is increased at the same time (Pfliiger and v. Platen). The same results occur in blind per- 
 sons, although to a less degree. Bluish violet light is almost as active as white light, while red light 
 is less active (Moleschott and Fubini). 
 
 10. The experiments of Grehant on dogs, seem to show that intense inflammation of the bron- 
 chial mucous membrane influences the C0 2 given off. 
 
 11. Among poisons, thebaia increases the C0 2 given off, while morphia, codeia, narcein, nar- 
 cotin, papaverin, diminish it [Fubini). 
 
 128. DIFFUSION OF GASES WITHIN THE LUNGS.— The 
 air within the air vesicles contains most C0 2 and least O, and as we pass from the 
 small to the large bronchi and onward to the trachea, the composition of the air 
 gradually approaches more closely to that of the atmosphere {Allan and Pepys). 
 Hence, if the air expired be collected in two portions, the first half (i.e., 
 the air from the larger air passages), contains less C0 2 (3.7 vols, per cent.) than 
 the second half (5.4 vols, per cent.). This difference in the percentage of gases 
 gives rise to a diffusion of the gases within the air passages ; the C0 2 must diffuse 
 from the air vesicles outward, and the O from the atmosphere and nostrils inward 
 (§ 33)- This movement is aided by the cardio-pneumatic movement (Landois 
 § 59). In hybernating animals and in persons apparently but not actually dead, the 
 exchange of gases within the lungs can only occur in the above-mentioned ways. 
 
 For ordinary purposes this mechanism is insufficient, and there are added the 
 respiratory movements whereby atmospheric air is introduced into the larger air 
 passages, from which and into which the diffusion currents of O and C0 2 pass, 
 on account of the difference of tension of the gases. 
 
 129. EXCHANGE OF GASES BETWEEN THE BLOOD OF 
 THE PULMONARY CAPILLARIES AND THE AIR IN THE 
 AIR VESICLES. — This exchange of gases occurs almost exclusively through 
 the agency of chemical processes, and therefore independently of the diffusion of 
 gases. 
 
 Method. — It is important to ascertain the tension of the O and C0 2 in the venous blood of the 
 pulmonary capillaries. Pfliiger and Woltberg estimated the tension by " catheterizing the lungs." 
 An elastic catheter was introduced through an opening in the trachea of a dog into the bronchus 
 leading to the lowest lobe of the left lung. An elastic sac was placed round the catheter, and when 
 the latter was introduced into the bronchus, the sac around the catheter was distended so as to plug 
 the bronchus. No air could escape between the catheter and the wall of the bronchus. The outer 
 end of the catheter was closed at first, and the dog was allowed to respire quietly. After four 
 minutes the air in the air vesicles was completely in equilibrium with the blood gases. The air of 
 the lung was sucked out of the catheter by means of an air pump, and afterward analyzed. 
 
 Thus we may measure indirectly the tension of the O and C0 2 in the venous 
 blood of the pulmonary capillaries. The direct estimation of the gases in differ- 
 ent kinds of blood is made by shaking up the blood with another gas. The gases 
 so removed indicate directly the proportion of blood gases. 
 
 The following tabular arrangement indicates the tension and percentage of 
 and C0 2 in arterial and venous blood, in the atmosphere, and in the air of the 
 alveoli : — 
 
 I. 
 O-Tension in arterial blood = 29.6 mm. Hg 
 (corresponding to a mixture containing 3.9 
 vol. per cent, of O). 
 
 II. 
 C0 2 -Tension in arterial blood = 21 mm. Hg 
 (corresponding to 2.9 vol. per cent.). 
 
 III. 
 O-Tension in venous blood = 22 mm. Hg 
 (corresponding to 2.9 vol. per cent.) 
 
 IV. 
 C0 2 -Tension in venous blood = 4i mm. Hg 
 (corresponding to 5.4 vol. per cent.). 
 
 V. 
 O-Tension in the air of the alveoli of the cathe- 
 terized lung =27.44 mm. Hg (correspond- 
 ing to 3.6 vol. per cent.). 
 
 VI. 
 C0 2 -Tension in the air of the alveoli of the 
 catheterized lung = 27 mm. Hg (correspond- 
 ing to 3.56 vol. per cent.). 
 
ABSORPTION OF OXYGEN IN THE LUNGS. 
 
 217 
 
 VII. 
 sion in the atmosphere = 158 mm. Hg 
 responding to 20.8 vol. per cent.), 
 
 VIII. 
 
 C0 2 -Tensioninthe atmosphere =0.38 mm. Hg 
 
 (corresponding to 0.03-0.05 vol. per cent.). 
 
 ien we compare the tension of the O in the air (VII = 158 mm. Hg) with 
 ension of the O in venous blood (111;= 22 mm. Hg, or V= 27.44 mm. 
 we might be inclined to assume that the passage of the O from the air of 
 ir vesicles into the blood was due solely to diffusion of the gases ; and simi- 
 we might assume that the C0 2 of the venous blood (IV or VI) diffused 
 :he air vesicles, because the tension of the C0 2 in the air is much less (VIII). 
 ; are a number of facts, however, which prove that the exchange of the 
 in the lungs is chiefly due to chemical forces. 
 
 >sorption of O. — With regard to the absorption of O from the air in the 
 li into the venous blood of the lung capillaries, whereby the blood is arterial- 
 it is proved that this is a chemical process. The gas-free (reduced) 
 sglobin takes up O to form oxyhaemoglobin (§ 15, I). That this absorption 
 othing to do directly with the diffusion of gases, but is due to a chemical 
 lination of the atomic compounds, is shown by the fact that, when pure O 
 ipired, the blood does not take up more O than when atmospheric air is 
 ed ; further, that animals made to breathe in a limited closed space can 
 b almost all the O — even to traces — into their blood before suffocation 
 s. Of course, if the absorption of O were due to diffusion, in the former 
 nore O would be absorbed, while in the latter case the absorption of O could 
 ossibly occur to such an extent as it does. The law of diffusion comes into 
 n connection with the absorption of O to this extent, viz., that the O diffuses 
 the air cells of the lung into the blood plasma, where it reaches the blood 
 iscles floating in the plasma. The haemoglobin of the blood corpuscles forms 
 ce a chemical compound (oxyhemoglobin) with the O. 
 
 n in very rarefied air, such as is met with in the upper regions of the atmosphere during a 
 1 ascent, the absorption of O still remains independent of the partial pressure [Loth. Meyer, 
 '). But a much longer time is required for this process at the ordinary temperature of the 
 so that in rarefied air the absorption of O is greatly delayed, but is not diminished. This is 
 jse of death in aeronauts who have ascended so high that the atmospheric pressure is dimin- 
 one-third {Setsckenow). 
 
 xretion of C0 2 . — With regard to the excretion of C0 2 from the blood, we 
 remember that the C0 2 in the blood exists in two conditions. Part of the 
 forms a loose or feeble chemical compound, while another portion is more 
 r combined. The former is obtained by those means which remove gases 
 fluids containing them in a state of absorption, so that in removing the C0 2 
 
 the blood it is difficult to determine whether the C0 2 so removed obeyed 
 .w of diffusion, or if it was expelled by chemical means, 
 hough it is convenient to represent the excretion of C0 2 from the blood into 
 ;r vesicles of the lung, as due to equilibration of the tension of the C0 2 on 
 lite sides of the alveolar membrane, i. <?., to diffusion — nevertheless, chemi- 
 jrocesses play an important part in this act. The absorption of O by the 
 ;d corpuscles acts, at the same time, in expelling C0 2 . This is proved by 
 .ct that the expulsion of C0 2 from the blood takes place more readily when 
 iimultaneously admitted (Ludwig and Holmgren). 
 
 e free supply of O not only favors the removal of the C0 2 , which is loosely 
 ined, but it also favors the expulsion of that portion of the C0 2 which is more 
 r combined, and which can only be expelled by the addition of acids to the 
 
 {Ludwig, Schoffer and Sczelkow). That the oxygenated blood corpuscles 
 
 their oxyhemoglobin) are concerned in the removal of C0 2 is proved by 
 ct that C0 2 is more easily removed from serum which contains oxygenated 
 
 corpuscles than from serum charged with O. 
 
 le following scheme may serve to illustrate the extent to which diffusion 
 > into play. The O must pass through the alveolar membrane, AB — including 
 
218 DISSOCIATION OF GASES. 
 
 the alveolar epithelium and the wall of the capillaries — as well as the blood plasma, 
 to reach the haemoglobin of the blood corpuscles. Similarly, the C0 2 must leave 
 the salts of the plasma with which it is in combination, and diffuse in the opposite 
 direction, through the wall of the capillaries, the alveolar membrane and epithe- 
 lium, to reach t£e air vesicles. Let AB represent the alveolar membrane ; on the 
 
 Partial pressure of air in I *--0 2 O 
 
 alveoli of lung. 1 2 7 2744 
 
 a- — y~ 4 p—B 
 
 Tension of gases in venous J 41 22 
 
 blood of lung. | C0 2 '.'.'.'. . ........... 
 
 one side of it is represented the partial pressure of the C0 2 and O in the air 
 vesicles ; and on the other, the partial pressure of the C0 2 and O in the venous 
 blood entering the lung. The indexes indicate the direction of diffusion.] 
 
 Theories. — Various theories have been proposed to account for the expulsion of the C0 2 from 
 its state of chemical combination in the blood due to the action of the oxygenated blood corpuscles. 
 (a) It is possible that the C0 2 in the blood corpuscles (perhaps united with paraglobulin ? — 
 SetscAenow) is expelled by the O taken up; (6) the acid reaction of the haemoglobin [Preyer) may 
 act so as to expel the C0 2 out of the corpuscles and the plasma; (c) by the absorption of O volatile 
 fatty acids may be formed from the haemoglobin (Hoppe-Seyler). These acids may act so as to 
 expel the C0 2 . 
 
 Nature of the Process. — The exchange of gases between the blood and the 
 air in the lungs has been represented by Donders as due to the process of disso- 
 ciation. 
 
 130. DISSOCIATION OF GASES.— Many gases form true chemical 
 compounds with other bodies (7. e., they combine according to their equivalents), 
 when the contact of these bodies is effected under conditions such that the partial 
 pressure of the gases is high. The chemical compound formed under these con- 
 ditions is broken up, whenever the partial pressure is diminished, or when it 
 reaches a certain minimum level, which varies with the nature of the bodies 
 forming the compound. Thus, by increasing and diminishing the partial pressure 
 alternately, a chemical compound of the gas may be formed and again broken up. 
 This process is called dissociation of the gases. The minimal partial pressure 
 is constant for each of the different substances and gases, but temperature, as in 
 the case of the absorption of gases, has a great effect on the partial pressure ; with 
 increase of temperature the partial pressure, under which dissociation occurs, 
 diminishes. 
 
 As an example of the dissociation of a gas, take the case of calcium carbonate. When it is heated 
 in the air to 440 C, C0 2 is given off from its state of chemical combination, but is taken up again 
 and a chemical compound formed, which is changed into chalk when it cools. 
 
 Dissociation in the. Blood. — The chemical combinations containing C0 2 
 and those containing O within the blood stream behave in a similar manner, viz., 
 the salts of the plasma, which are combined with C0 2 , and the oxyhsemoglcbin. 
 If these compounds of O and C0 2 are placed under conditions where the partial 
 pressure of these gases is very low — i. e., in a medium containing a very small 
 amount of these gases, the compounds are dissociated, i. e. , they give off C0 2 or 
 O. If after being dissociated they are placed under conditions where, owing to 
 the large amount of these gases, the partial pressure of O or of C0 2 is high, these 
 gases are taken up again, and enter into a condition of chemical combination. 
 
 The haemoglobin of the blood in the pulmonary capillaries finds plenty of in 
 the alveoli ; hence, it unites with the O owing to the high partial pressure of the 
 O in the lung, and so forms the compound oxyhemoglobin. On its course through 
 the capillaries of the systemic circulation, the oxyhsemoglobin of the blood comes 
 into relation with tissues poor in O ; the oxyhasmoglobin is dissociated, the is 
 supplied to the tissues, and the blood freed from this O returns to the right heart, 
 and passes to the lungs, where it takes up the new O. 
 
INTERNAL RESPIRATION. 219 
 
 lie blood while circulating meets with most C0 2 in the tissues ; the high partial 
 >ure of the CO a in the tissues causes the C0 2 to unite with certain constituents 
 be blood so as to form chemical compounds, which carry the C0 2 from the 
 es to the lungs. In the air of the lungs, however, the partial pressure of the 
 is very low, dissociation of these chemical compounds occurs under the low 
 ial pressure, and the C0 2 passes into the air cells of the lung, from which it is 
 :lled during expiration. It is evident that the giving up of O from the blood 
 le tissues, and the absorption of C0 2 from the tissues, go on side by side and 
 place simultaneously, while in the lungs the reverse processes occur almost 
 iltaneously. 
 
 I. CUTANEOUS RESPIRATION. — Methods.— If a man or an animal be placed in the 
 ber of a respiratory apparatus (Scharling 's, ox v. Pettenkofer's), and if tubes be so arranged 
 he respiratory gases do not enter the chamber, of course we obtain only the "perspiration " of 
 kin in the chamber. It is less satisfactory to leave the head of the person outside the chamber 
 : the neck is fixed air tight in the wall of the chamber. The extent of the cutaneous respiration 
 limb may be ascertained by enclosing it in an air-tight vessel {R'dhrig) similar to that used for 
 rm in the plethysmograph (g 101). 
 
 ,oss by Skin. — A healthy man loses by the skin, in 24 hours, -^ of his body 
 fht (Seguin), which is greater than the loss by the lungs, in the ratio of 3 : 2 
 lentin, 1843). Only 10 grammes — 150 grains (Scharling), or it may be 3.9 
 times — £0 grains (Aubert), of the entire loss is due to the C0 2 given off by the 
 . The remainder of the excretion from the skin is due to water [^2-2 lbs. 
 y] containing a few salts in solution. When the surrounding temperature is 
 :d, the C0 2 is increased ( Gerlacfi), in fact it may be doubled (Auberi) ; 
 ent muscular exercise has the same effect. 
 
 • Absorbed. — The O taken up by the skin is either equal to (Hegnault and 
 ;et), or slightly less than, the C0 2 given off. As the C0 2 excreted by the skin 
 nly ffaf of that excreted by the lungs, while the O taken in = ^fo of that 
 :n in by the lungs, it is evident that the respiratory activity of the skin is very 
 it. Animals whose skin has been covered by an impermeable varnish die, not 
 1 suffocation, but from other causes (§ 225). 
 
 animals with a thin, moist epidermis (frog) the exchange of gases is much greater, and in 
 the skin so far supports the lungs in their function, and may even partly replace them function- 
 In mammals with thick, dry, cutaneous appendages, the exchange of gases is, again, much 
 :han in man. 
 
 32. INTERNAL RESPIRATION.— Where C0 2 is formed.— By 
 term " internal respiration " is understood the exchange of gases between 
 capillaries of the systemic circulation and the tissues of the various organs 
 lie body. As organic constituents of the tissues, during their activity, undergo 
 lual oxidation, and form, among other products C0 2 , we may assume — (1) 
 the chief focus for the absorption of O and the formation of C0 2 is to be 
 fht for within the tissues themselves. That the O from the blood in the 
 llaries rapidly penetrates or diffuses into the tissues is shown by the fact that 
 blood in the capillaries rapidly loses and gains C0 2 , while blood containing 
 ind kept warm outside the body, changes very slowly and incompletely. If 
 :ions of fresh tissues be placed in defibrinated blood containing O, then the O 
 dly disappears {Hoppe-Seyler). Frogs deprived of their blood exhibit an ex- 
 tige of gases almost as great as normal. This shows that the exchange of gases 
 t take place in the tissues themselves (Pfliiger and Oertmann). If the chief 
 lations took place in the blood and not in the tissues, then, during suffocation, 
 n O is excluded, the substances which use up O, i. e., those substances which 
 as reducing agents, ought to accumulate in the blood. But this is not the 
 :, for the blood of asphyxiated animals contains mere traces of reducing mate- 
 > (Pfluger). It is difficult to say how the O is absorbed by the tissues, and 
 t becomes of it immediately it comes in contact with the living elements of 
 tissues. Perhaps it is temporarily stored up, or it may form certain intermediate 
 
220 TENSION OF THE GASES IN CAVITIES AND LYMPH. 
 
 less oxidized compounds. This may be followed by a period of rapid formation 
 and excretion of C0 2 . On this supposition, it is evident that the absorption of 
 and the excretion of C0 2 need not occur to the same extent, so that the amount 
 of C0 2 given off at any period is not necessarily an index of the amount of 
 absorbed during the same period (§ 127). 
 
 [There are two views as to where the C0 2 is formed as the blood passes through 
 the tissues. One view is that the seat of oxidation is in the blood itself, and the 
 other is that it is formed in the tissues. If we knew the tension of the gases in 
 the tissues the problem would be easily solved, but we can only arrive at a knowl- 
 edge of this subject indirectly, in the following ways] : — 
 
 C0 2 in Cavities. — That the C0 2 is formed in the tissues is supported by the fact that the amount 
 of C0 2 in the fluids of the cavities of the body is greater than the CO a in the blood of the 
 capillaries. 
 
 Pfliiger and Strassburger found the tension of C0 2 to be, in 
 
 Mm. 
 
 Arterial blood . . . 21.28 Hg tension 
 
 Peritoneal cavity . . 58.5 " " 
 
 Acid urine .... 68.0 " " 
 
 Mm. 
 
 Bile 50.8 Hg tension. 
 
 Hydrocele fluid . . 46.5 " " 
 
 The large amount of C0 2 in these fluids can only arise from the C0 2 of the tissues passing into 
 them. 
 
 Gases of Lymph. — In the lymph of the ductus thoracicus the tension of C0 2 = 33.4 to 37.2 
 mm. Hg, which is greater than in arterial blood, but considerably less than in venous blood (41.0 
 mm. Hg). [Ltuhaig and Hammarsten, Tschiriew.~\ This does not entitle us to conclude lhat in 
 the tissues from which the lymph comes only a small quantity of C0 2 is formed, but rather that in 
 the lymph there is less attraction for the C0 2 formed in the tissues than in the blood of the capil- 
 laries, where chemical forces are active in causing it to combine, or that in the course of the long 
 lymph current the C0 2 is partly taken back to the tissues, or that C0 2 is formed in the blood itself. 
 Further, the muscles, which are by far fhe largest producers of C0 2 , contain few lymphatics, never- 
 theless they supply much C0 2 to the blood. The amount of free " non-fixed " C0 2 contained in 
 the juices and tissues indicates that the CO 2 passes from the tissues into the blood; still, Preyer 
 believes that in venous blood C0 2 undergoes chemical combination. The change of O and C0 2 
 varies much in the different tissues. The muscles are the most important organs, for in their active 
 condition they excrete a large amount of C0 2 , and use up much O. The O is so rapidly used up 
 by them that no free O can be pumped out of muscular tissue (L. Hermann). The exchange of 
 gases is more vigorous during the activity of the tissues. Nor are the salivary glands, kidneys, and 
 pancreas any exception, for although when these organs are actively secreting, the blood flows out 
 of the dilated veins in a bright red stream, still the relative diminution of C0 2 is more than com- 
 pensated by the increased volume of blood which passes through these organs. 
 
 Reductions by the Tissues. — The researches of Ehrlich have shown that in most tissues very 
 energetic reductions take place. If coloring matters, such as alizarin blue, indophenol blue, or 
 methyl blue, be introduced into the blood stream, the tissues are colored by them. Those tissues 
 or organs which have a particular affinity for O (e.g., liver, cortex of the kidney, and lungs), absorb 
 O from these pigments, and render them colorless. The pancreas and submaxillary gland scarcely 
 reduce them at all. 
 
 (2) In the blood itself, as in all tissues, O is used up and C0 2 is formed. This 
 is proved by the following facts : That blood withdrawn from the body becomes 
 poorer in O and richer in C0 2 ; that in the blood of asphyxia, free from 0, and 
 in the blood corpuscles (Afanassieff), there are slight traces of reducing agents, 
 which become oxidized on the addition of O [A. Schmidt). Still, this process is 
 comparatively insignificant as against that which occurs in all the other tissues. 
 That the walls of the vessels — more especially the muscular fibres in the walls of 
 the small arteries — use O and produce C0 2 is unquestionable, although it is so 
 slight that the blood in its whole arterial course undergoes no visible change. 
 
 Ludwig and his pupils have proved that C0 2 is actually formed in the blood. If the easily oxi- 
 dizable lactate of soda be mixed with blood, and this blood be caused to circulate in an excised but 
 still living organ, such as a lung or kidney, more O is used up and more C0 2 is formed than in 
 unmixed blood similarly transfused. 
 
 (3) That the tissues of the living lungs use O and give off C0 2 is probable. 
 When C. Ludwig and Miiller passed arterial blood through the blood vessels of a 
 lung deprived of air, the O was diminished and the C0 2 increased. 
 
RESPIRATION IN A CLOSED SPACE. 221 
 
 the total amount of C0 2 and O found in the entire blood, at any one time, 
 y 4 grammes, and as the daily excretion of C0 2 = 900 grammes, and the 
 :orbed daily = 744 grammes, it is clear that exchange of gases must go on 
 great rapidity, that the O absorbed must be used quickly, and the C0 2 must 
 pidly excreted. 
 
 , it is a striking fact that oxidation processes of such magnitude, as, e. g., the union of C to 
 C0 2 , occur at the relatively low temperature of the blood and the tissues. It has been 
 :d that the blood acts as an ozone producer, and transfers this active form of O to the tissues, 
 showed that the alkaline reaction of most of the juices and tissues favors the process of oxi- 
 . Numerous organic substances, which are not altered by O alone, become rapidly oxidized 
 presence of free alkalies, e. g., gallic acid, pyrogallic acid and sugar; while many organic 
 which are unaffected by ozone alone, are changed into carbonates, when in the form of alka- 
 Its ( Gorup-Besanez) ; and in the same way when they are introduced into the body in the 
 if acids, they are partly or wholly excreted in the urine, but when they are administered as 
 le compounds they are changed into carbonates. 
 
 5. RESPIRATION IN A CLOSED SPACE.— Respiration in a closed 
 lited space causes — (1) a gradual diminution of O ; (2") a simultaneous increase 
 ^z j (3) a diminution in the volume of the gases. If the space be of moderate 
 nsions, the animal uses up almost all the O contained therein (Nysteri), and 
 ultimately from spasms caused by the asphyxia. The O is absorbed, there- 
 -independently of the laws of absorption — by chemical means. The O in 
 lood is almost completely used up (Setschenow, § 129). In a larger closed 
 , the C0 2 accumulates rapidly, before the diminution of O is such as to 
 : the life of the animal. As C0 2 can only be excreted from the blood when 
 :nsion of the C0 2 in the blood is greater than the tension of C0 2 in the 
 s soon as the C0 2 in the surrounding air in the closed space becomes the 
 as in the blood, the C0 2 will be retained in the blood, and finally C0 2 may 
 Dack into the body. This occurs in a large closed space, when the amount 
 is still sufficient to support life, so that death occurs under these circum- 
 es (in rabbits) through poisoning with C0 2 causing diminished excitability, 
 if consciousness and lowering of temperature, but no spasms ( Worm Miiller). 
 ire O, animals breathe in a normal way ; the quantity of O absorbed and 
 )0 2 excreted is quite independent of the percentage of O, so that the former 
 •s through chemical agency independent of pressure (Regnault and Reiset, 
 ?r, Lukjanoui). In closed spaces filled with O, animals died by reabsorption 
 e C0 2 excreted. Worm Miiller found that rabbits died after absorbing C0 2 
 to half the volume of their body, although the air still contained 50 per 
 O. Animals can breathe quite quietly a mixture of air containing 14.8 per 
 (20.9 per cent, normal) ; with 7 per cent, they breathe with difficulty; with 
 )er cent, there is marked dyspnoea ; with 3 per cent. O there is tolerably 
 asphyxia (W. Miiller). The air expired by man normally contains 14 to 
 :r cent. O. According to Hempner, mammals placed in a mixture of gases 
 in O, use slightly less O. 
 
 pncea occurs when the respired air is deficient in O, as well as when it is overcharged with 
 But the dyspnoea in the former case is prolonged and severe ; in the latter, the respiratory 
 Y soon ceases. The want of O causes a greater and more prolonged increase of the blood 
 re than is caused by excess of C0 2 . Lastly, the consumption of O in the body is less affected 
 the O in the air is diminished than when there is excess of CO z . If air containing a dimin- 
 imount of O be respired, death is preceded by violent phenomena of excitement and spasms, 
 are absent in cases of death caused by breathing air overcharged with C0 2 . In poisoning 
 '0 2 , the excretion of C0 2 is greatly diminished, while with diminution of O, it is almost 
 nged (C. Friealander and E. Herter). 
 
 animals be supplied with a mixture of gases similar to the atmosphere, in 
 1 N is replaced by H, they breathe quite normally (Lavoisier and Seguin) ; 
 I undergoes no great change. 
 
 Bernard found that, when an animal breathed in a closed space, it became partially accus- 
 to the condition. On placing a bird under a bell-jar, it lived several hours; but if several 
 
222 PHENOMENA OF ASPHYXIA. 
 
 hours before its death another bird fresh from the outer air were placed under the same bell-jar, the 
 second bird died at once, with convulsions. 
 
 Frogs, when placed for several hours in air devoid of O, give off just as much C0 2 as in air 
 containing O, and they do this without any obvious disturbance (PJluger, Aubert). Hence, it 
 appears that the formation of C0 2 is independent of the absorption of O, and the C0 2 must be 
 formed from the decomposition of other compounds. Ultimately, however, complete motor paraly- 
 sis occurs, while the circulation remains undisturbed (Aubert). 
 
 [134. DYSPNCEA AND ASPHYXIA.J— [The causes of dyspnoea have 
 already been referred to (§ m), and those of asphyxia are referred to in detail 
 in § 368. If from any cause an animal be not supplied with a due amount of air, 
 normal respiration becomes greatly altered, passing through the phases of hyper- 
 pnoea, or increased respiration, dyspnoea or difficulty of breathing to the final 
 condition of suffocation or asphyxia. The phenomena of asphyxia may be 
 developed in an animal by closing its trachea by means of a clamp, and in fact 
 by any means which prevent the entrance of air or blood into the lungs. 
 
 The phenomena of asphyxia are usually divided into several stages : 1. 
 During the first stage there is hyperpncea, the respirations being deeper, more 
 frequent and labored. The extraordinary muscles of respiration — both those of 
 inspiration and expiration — referred to in § 118 are called into action, the condi- 
 tion of dyspnoea being rapidly produced, and the struggle for air becomes more 
 and more severe. During this time the oxygen of the blood is being used up, the 
 blood itself is becoming more and more venous. This venous blood circulating 
 in the medulla oblongata and spinal cord stimulates the respiratory centres, thus 
 causing these violent respirations. This stage usually lasts about a minute, and 
 gradually gives place to — 
 
 2. The second stage, when the inspiratory muscles become less active, while 
 those concerned in labored expiration contract energetically, and, indeed, almost 
 every muscle in the body may contract ; so that this stage of violent expiratory 
 efforts ends in general convulsions. The convulsions are due to stimulation of the 
 respiratory centres by the venous blood. The convulsive stage is short, and is 
 usually reached in a little over one minute. This storm is succeeded by — 
 
 3. The third stage, or stage of exhaustion, the transition being, usually, 
 somewhat sudden. This condition is brought about by the venous blood acting 
 on and paralyzing the respiratory centres. The pupils are widely dilated, con- 
 sciousness is abolished, and the activity of the reflex centres is so depressed that 
 it is impossible to discharge a reflex act, even from the cornea. The animal lies 
 almost motionless, with flaccid muscles, and, to all appearance, dead ; but every 
 now and again, at long intervals, it makes a few deep inspiratory efforts, showing 
 that the respiratory centres are not quite, but almost, paralyzed. Gradually, the 
 pauses become longer and the inspirations feebler and of a gasping character. As 
 the venous blood circulates in the spinal cord, it causes a large number of muscles 
 to contract, so that the animal extends its trunk and limbs. It makes one great 
 inspiratory spasm, the mouth being widely open and the nostrils dilated, and 
 ceases to breathe. After this stage, which is the longest and most variable, the 
 heart becomes paralyzed, partly from being over-distended with venous blood, 
 and partly, perhaps, from the action of the venous blood on the cardiac tissues, 
 so that the pulse can hardly be felt. To this pulseless condition the term 
 " asphyxia" ought properly to be applied. In connection with the resuscitation 
 of asphyxiated persons, it is important to note that the heart continues to beat 
 for a few seconds after the respiratory movements have ceased. 
 
 The whole series of phenomena occupies from 3 to 5 minutes, according to the 
 animal operated on, and depending, also, upon the suddenness with which the 
 trachea was closed. If the cause of suffocation act more slowly, the phenomena 
 are the same, only they are developed more slowly. 
 
 The Circulation. — The post-mortem appearances in man or in an animal are 
 generally well marked. The right side of the heart, the pulmonary artery, the 
 
THE CHANGES OF THE CIRCULATION DURING ASPHYXIA. 223 
 
 : cavse and the veins or the neck are engorged with dark venous blood. The 
 side is comparatively empty, because the rigor mortis of the left side of the 
 :, and the elastic recoil of the systemic arteries, force the blood toward the 
 mic veins. The blood itself is almost black, and is deprived of almost all 
 tygen, its haemoglobin being nearly all in the condition of reduced haemo- 
 in, while ordinary venous blood contains a considerable amount of oxyhae- 
 lobin as well as reduced Hb. The blood of an asphyxiated animal, practically, 
 dns none of the former and much of the latter. 
 
 is important to study the changes in the circulation in connection with the 
 ard phenomena exhibited by an animal during suffocation, 
 e may measure the blood pressure in any artery of an animal while it is being 
 yxiated, or we may open its chest, maintain artificial respiration, and place a 
 Dmeter in a systemic artery, e.g., the carotid, and another in a branch of the 
 lonary artery. In the latter case, we can watch the order of events in the 
 t itself, when the artificial inspiration is interrupted. It is well to study the 
 ts in both cases. 
 
 the blood pressure be measured in a systemic artery, e.g., the carotid, it is 
 d that the blood pressure rises very rapidly and to a great extent during the 
 and second stages ; the pulse beats at first are quicker, but soon become 
 er and more vigorous. During the third stage it falls rapidly to zero. The 
 t rise of the blood pressure during the first and second stages is chiefly due 
 le action of the venous blood on the vasomotor centre, causing constriction 
 le small systemic arteries. The peripheral resistance is thus greatly increased, 
 it tends to cause the heart to contract more vigorously ; but the slower and 
 5 vigorous beats of the heart are also partly due to the action of the venous 
 d on the cardio-inhibitory centre in the medulla. 
 
 the second method be adopted — viz., to open the chest — keep up artificial 
 nation, and measure the blood pressure in a branch of the pulmonary artery, 
 :ll as in a systemic artery — e.g., the carotid — we find that when the artificial 
 iration is stopped, in addition to the rise of the blood pressure indicated in 
 :arotid manometer, the cavities of the heart and the large veins near it are 
 )rged with venous blood. There is, however, but a slight comparative rise in 
 blood pressure in the pulmonary artery. This may be accounted for either by 
 julmonary artery not being influenced to the same extent as other arteries, by 
 vasomotor centre, or by its greater distensibility (Lichtheim — compare § 88). 
 as the heart itself is supplied through the coronary arteries with venous blood, its 
 >n soon becomes weakened ; each beat becomes feebler, so that soon the left 
 ricle ceases to contract, and is unable to overcome the great peripheral resist- 
 : in the systemic arteries, although the right ventricle may still be contracting, 
 he blood becomes more venous, the vasomotor centre becomes paralyzed, the 
 1 systemic arteries relax, and the blood flows from them into the veins, while 
 Dlood pressure in the carotid manometer rapidly falls. The left ventricle, 
 relieved from the great internal pressure, may execute a few feeble beats, but 
 can only be feeble, as its tissues have been subjected to the action of the very 
 ire blood. More and more blood accumulates in the right side, from the 
 es already mentioned. The violent inspiratory efforts in the early stages 
 ■ate blood from the veins toward the right side of the heart, but, of course, 
 factor is absent when the chest is opened.] 
 
 Convulsions during asphyxia occur only in warm-blooded animals, and 
 in frogs. If a drug when injected into a mammal excites convulsions, 
 does not do so in the frog, then it is usually concluded that the convulsions 
 due to its action on the circulation and respiration, and not to any direct 
 dating effect upon the motor centres. But if the drug excite convulsions 
 i in the mammal and frog, then it probably acts directly on the motor 
 res {Bruntoii).~\ 
 
224 ARTIFICIAL RESPIRATION IN ASPHYXIA. 
 
 [Recovery from the Condition of Asphyxia. — If the trachea of a dog be closed suddenl 
 and completely, the average duration of the respiratory movements is 4 minutes, 5 seconds, whil 
 the heart continues to beat for about 7 minutes. Recovery may be obtained if proper means b 
 adopted before the heart ceases to beat; but after this, never.] 
 
 [If a dog be drowned, the result is different. After complete submersion for \yi minutes 
 recovery did not take place. In the case of drowning, air passes out of the chest, and water i 
 inspired into and fills the air vesicles. It is rare for recovery to take place in a person deprived 
 air for more than five minutes. If the statements of sponge divers are to be trusted, a person ma; 
 become accustomed to the deprival of air for a longer time than usual. In cases where recover 
 takes place after a much longer period of submersion, it has been suggested that, in these cases 
 syncope occurs, the heart beats but feebly or not at all, so that the oxygen in the blood is not usee 
 up with the same rapidity. It is a well-known fact that newly-born and young puppies can be sub 
 merged for a long time before they are suffocated.] 
 
 Artificial Respiration in Asphyxia. — In cases of suspended animation, artificial respiratioi 
 must be performed. The first thing to be done is to remove any foreign substance from the 
 respiratory passages (mucus or oedematous fluids) in the newly-born or asphyxiated. In doubtful 
 cases, open the trachea and suck out any fluid by means of an elastic catheter (v. //titer). Recoursi 
 must in all cases be had to artificial respiration. There are several methods of dilating and com 
 pressing the chest so as to cause an exchange of gases. One method is to compress the chesl 
 rhythmically with the hands. 
 
 [Marshall Hall's Method. — "After clearing the mouth and throat, place the patient on th< 
 face, raising and supporting the chest wall on a folded coat or other article of dress. Turn thf 
 body very gently on the side and a little beyond, and then briskly on the face, back again, repeat 
 ing these measures cautiously, efficiently and perseveringly, about fifteen times in the minute, or once 
 every four or five seconds, occasionally varying the side. By placing the patient on the chest, the 
 weight of the body forces the air out ; when turned on the side, this pressure is removed, and ail 
 enters the chest. On each occasion that the body is replaced on the face, make uniform but effi- 
 cient pressure with brisk movement on the back between and below the shoulder-blades or bones on 
 each side, removing the pressure immediately before turning the body on the side. During the 
 whole of the operations let one person attend solely to the movements of the head and of the arm 
 placed under it."] 
 
 [Sylvester's Method. — " Place the patient on the back on the flat surface, inclined a little 
 upward from the feet ; raise and support the head and shoulders on a small, firm cushion or folded 
 article of dress placed under the shoulder-blades. Draw forward the patient's tongue, and keep it 
 projecting beyond the lips; an elastic band over the tongue and under the chin will answer this 
 purpose, or a piece of string or tape may be tied around them, or by raising the lower jaw, the 
 teeth may be made to retain the tongue in that position. Remove all tight clothing from about the 
 neck and chest, especially the braces." 
 
 " To Imitate the Movements of Breathing. — Standing at the patient's head, grasp the arms just 
 above the elbows, and draw the arms gently and steadily upward above the head, and keep them 
 stretched upward for two seconds. By this means air is drawn into the lungs. Then turn down 
 the patient's arms and press them gently and firmly for two seconds against the sides of the chest. 
 By this means air is pressed out of the lungs. Repeat these measures alternately, deliberately and 
 perseveringly, about fifteen times in a minute, until a spontaneous effort to respire is perceived, 
 immediately upon which cease to imitate the movements of breathing, and proceed to induce circu- 
 lation and warmtk."~\ 
 
 Howard advises rhythmical compression of tbe chest and abdomen by sitting like a rider astride 
 of the body, while Schuller advises that the lower ribs be seized from above with both hands and 
 raised, whereby the chest is dilated, especially when the thigh is pressed against the abdomen to 
 compress the abdominal walls. The chest is compressed by laying the hands flat upon the , hypo- 
 chondria. Artificial respiration acts favorably by supplying O to, as well as removing C0 2 from, 
 the blood; further, it aids the movement of the blood within the heart and in the large vessels of 
 the thorax. If the action of the heart has ceased, recovery is impossible. In asphyxiated newly- 
 born children, we must not cease to perform artificial respiration too soon. Even when the result 
 appears hopeless, we ought to persevere. Pfliiger and Zuntz observed that the reflex excitability of 
 the fcetal heart continued for several hours after the death of the mother. 
 
 Resuscitation by compressing the heart. — B6hm found that in the case of cats poisoned with 
 potash salts or chloroform, or asphyxiated, so as to arrest respiration and the action of the heart — 
 even for a period of forty minutes — and even when the pressure within the carotid had fallen to 
 zero, he could restore animation by rhythmical compression of the heart, combined with artificial 
 respiration. The compression of the heart causes a slight movement of the blood, while it acts at 
 the same time as a rhythmical cardiac stimulus. After recovery of the respiration, the reflex excit- 
 ability is restored, and gradually also voluntary movements. The animals are blind for several 
 days, the brain acts slowly, and the urine contains sugar. These experiments show how important 
 it is in cases of asphyxia to act at the same time upon the heart. 
 
 For physiological purposes, artificial respiration is often made use of, especially after poisoning 
 
ACCIDENTAL IMPURITIES OF THE AIR. 225 
 
 ;urara. Air is forced into the lungs by means of an elastic bag or bellows, attached to a 
 la tied in the trachea. The cannula has a small opening in the side of it to allow the expired 
 escape. 
 
 thological. — After the lungs have once been properly distended with air, it is impossible by 
 mount of direct compression of them to get rid of all the air. This is probably due to the 
 ire acting on the small bronchi, so as to squeeze them, before the air can be forced out of the 
 sides. If, however, a lung be filled with C0 2 , and be suspended in water, the C0 2 is 
 bed by the water, and the lungs become quite free from air and are atelectic {Hermann and 
 r). The atelectasis which sometimes occurs in the lung may thus be explained : If a bron- 
 is stopped with mucus or exudation, an accumulation of C0 2 in the air vesicles belonging to 
 ronchus occurs. If this C0 2 is absorbed by the blood or lymph, the corresponding area of the 
 will become atelectic. Sometimes there is spasm of the respiratory muscles, brought about 
 •ect or reflex stimulation of the respiratory centre. 
 
 i. RESPIRATION OF FOREIGN GASES, AND ABSORPTION BY THE 
 
 [GS. — No gas without a sufficient admixture of O can support life. Even with completely 
 
 uous and indifferent gases, if no O be mixed with them, they cause suffocation in 2 to 3 
 
 :es. 
 
 Completely indifferent Gases are N, H, CH 4 . The living blood of an animal breathing 
 
 gases yields no O to them (Pfliiger). 
 
 Poisonous Gases. — (a) Those that displace O, and form a permanent stable compound 
 the haemoglobin — (1) CO {\ 16 and 17). (2) CNH (hydrocyanic acid) displaces (?) O from 
 iglobin, with which it forms a more stable compound and kills exceedingly rapidly. It prevents 
 ng changed into ozone in the blood. Blood corpuscles charged with hydrocyanic acid lose 
 roperty of decomposing hydric peroxide into water and O {\ 17, 5)- 
 
 Narcotic Gases. — (1) C0 2 — v. Pettenkofer characterizes air containing O with 1 per cent. 
 
 Fig. 143. 
 
 Ciliated epithelium. . 
 
 .Clear disk. 
 
 - Intermediate forms. 
 
 Debove's membrane..- '*<^ . ^i^ Inner layer. 
 
 Ciliated epithelium from the larynx of a horse (Toldt), (see Fig. 125). 
 
 as "bad air;" still, air in a room containing this amount of C0 2 produces a disagreeable feeling 
 r from the impurities mixed with it than from the actual amount of C0 2 itself. Air containing 
 cent. C0 2 produces decided discomfort, and with 10 per cent, it endangers life, while larger 
 nts cause death with symptoms of coma. (2) N 2 (nitrous oxide) respired, mixed with £ 
 ne O, causes, after 1 to 2 minutes, a short temporary stage of excitement ("Laughing gas" of 
 avy), which is succeeded by unconsciousness, and afterward by an increased excretion of C0 2 . 
 )zonized air causes similar effects (Binz). 
 
 Reducing Gases. — (1) H 2 S (sulphuretted hydrogen) rapidly robs blood corpuscles of O, 
 1 H 2 being formed, and death occurs rapidly before the gas can decompose the haemoglobin 
 pe-Seyler). 
 
 PH S — Phosphuretted hydrogen is oxidized in the blood to form phosphoric acid and water, 
 decomposition of the haemoglobin (Dybkowski, Koschlakoff, and Popoff). 
 
 AsH 3 , arseniuretted hydrogen and SbH 3 , antimoniuretted hydrogen, act like PH 3 , but, in 
 ion, the haemoglobin passes out of the stroma and appears in the urine. 
 
 C 2 N 2 , cyanogen, absorbs O, and decomposes the blood {Rosenthal and Laschkewitsch). 
 '.. Irrespirable Gases, i. e., gases which, on entering the larynx, cause reflex spasm of the 
 5. When introduced into the trachea they cause inflammation and death. Under this category 
 
 hydrochloric, hydrofluoric, sulphurous, nitrous, and nitric acids, ammonia, chlorine, fluorine, 
 izone. 
 
 sorption takes place almost immediately through the lungs (strychnia, curara, potassic nitrate), 
 ar more rapidly than by injection under the skin. Colloids are absorbed more slowly {Peiper). 
 
 5. ACCIDENTAL IMPURITIES OF THE AIR.— Dust Particles.— Among these 
 ust particles, which occur in enormous amount suspended in the air, and thereby act injuriously 
 the respiratory organs. The ciliated epithelium of the respiratory passages eliminates a large 
 ler of them (Fig. 143). Some of them, however, reach the air vesicles of the lung, where they 
 
 J 5 
 
226 VENTILATION OF ROOMS. 
 
 penetrate the epithelium, reach the interstitial lung tissue and lymphatics, and so pass with the lymp] 
 stream into the bronchial glands. Particles of coal or charcoal are found in the lungs of all elderf 
 individuals, and blacken the alveoli. In moderate amount these black particles do not seem to d< 
 any harm in the tissues, but when there are large accumulations they give rise to lung affections 
 which lead to disintegration of these organs. [In coal miners, for example, the lung tissues alonj 
 the track of the lymphatics and in the bronchial glands are quite black, constituting " coal miners 
 lung."] In many trades various particles occur in the air; miners, grinders, stone-masons, file 
 makers, weavers, spinners, tobacco manufacturers, millers, and bakers, suffer from lung affection; 
 caused by the introduction of particles of various kinds inhaled during the time they are at work. 
 
 Germs. — There seems no doubt that the seeds of some contagious diseases may be inhaled 
 Diphtheritic bacteria (Micrococcus diphtheriticus — Bertel) become localized in the pharynx and ii 
 the larynx — glanders in the nose {Schiitz and Loffler) — measles in the bronchi — whooping cougl 
 in the bronchi — hay monads in the nose — the cocci of pulmonary inflammation {Klebs, Leichten 
 stern) in the pulmonary alveoli. Tuberculosis, according to R. Koch, is due to the introductioi 
 and development of the Bacillus tuberculosis in the lungs ; the bacillus being derived from the dus 
 of tuberculous sputa. The same seems to be the case with the Bacillus of leprosy [Hansen), anc 
 with Bacillus malarise, which is the cause of malaria {Klebs and Tomasi-Crudeli). The latte 
 organism thus reaches the blood ; it ehanges the Hb within the red blood corpuscles into melanii 
 (\ 10, 3), and causes them to break up [Marchiafava and Celli). The exciter of smallpox (Micro 
 coccus vaccinae) gains access to the blood in the same way {Keber, 1868), also the Spirillum 
 remittent fever (Fig. 20 — Obermeier, i8y^), the microbe of scarlet fever, etc. 
 
 Setds of disease pass into the mouth along with air, and also with the food, are swallowed, anc 
 undergo development in the intestinal tract, as is probably the case in cholera (Comma bacillus 
 R. Koch), [although that this bacillus is the cause of cholera is questioned by Klein and Gibbes] 
 dysentery and typhoid {Eberth, Klebs), and in anthrax which is due to Bacterium anthracis (Fig 
 21 — Pollender, 1854). 
 
 137. VENTILATION OF ROOMS.— Fresh Air and Cubic Space. — Fresh air is ai 
 necessary for the healthy as for the sick. Every healthy person ought to have a cubic space of, a 
 the very least, 800 cubic feet, and every sick person at the very least 1000 cubic feet of space. [Th( 
 cubic space allowed per individual varies greatly, but 1000 cubic feet is a fair average. If the ai; 
 in this space is to be kept sweet, so that the C0 2 does not exceed .06 per cent., 3000 cubic feet 
 air per hour must be supplied, i. e., the air in the space must be renewed three times per hour.] 
 
 In Prussia, in barracks, 420-500 cubic feet are allowed for every soldier, for hospital, 600-720 
 in England 600 cubic feet per head. 
 
 [Floor Space. — It is equally important to secure sufficient floor space, and this is especially thi 
 case in hospitals. If possible,. 100-120 square feet of floor space ought to be provided for eaci 
 patient in a hospital ward, and if it is obtainable a cubic space of 1500 cubic feet (Parkes). Inal 
 cases the minimum floor space should not be less than -^ of the cubic space.] 
 
 Overcrowding. — When there is overcrowding in a room 'the amount of C0 2 increases, v. Pet 
 tenkofer found the normal amount of C0 2 (.04 to .05 per 1000) increased in comfortable rooms t< 
 0.54-0.7 per 1000 ; in badly ventilated sick chambers = 2.4 ; in overcrowded auditoriums, 3.2 ; ii 
 pits = 4.9 ; in school rooms, 7.2 per 1000. Although it is not the quantity of C0 2 which makes thi 
 air of an overcrowded room injurious, but the excretions from the outer and inner surfaces of thi 
 body, which give a distinct odor to the air, quite recognizable by the sense of smell, still the amoun 
 of C0 2 is taken as an index of the presence and amount of these other deleterious substances 
 The question as to whether the ventilation of a room or ward occupied by persons is sufficient, i; 
 ascertained by estimating the amount of C0 2 . A room which does not give a disagreeable, some 
 what stuffy, odor has less than 0.7 per 1000 of C0 2 , while the ventilation is certainly insufficient i 
 the C0 2 = 1 per 1000. 
 
 As the air contains only 0.0005 cubic metre C0 2 in I cubic metre of air, and as an adult produce 
 hourly 0.0226 cubic metre C0 2 , calculation shows that every person requires 113 cubic metres 
 fresh air per hour, if the C0 2 is not to exceed 0.7 per 1000: for 0.7: 1000 = (0.0226 + *■)< 
 0.0005) : x, i. e., x = 1 13. 
 
 [Vitiating Products. — In a state of repose, an adult man gives off from 12 to 16 cubic feet 
 C0 2 in twenty-four hours, or on an average .6 cubic feet per hour. To this must be added a certaii 
 quantity of organic matter, which is extremely deleterious to health. While the C0 2 diffuse 
 readily and is easily disposed of by opening the windows, this is not the case with the organi 
 matter, which adheres to clothing, curtains, and furniture ; hence, to get rid of it, a room, and espe 
 ■ daily a sleeping apartment, requires to be well aired for a long time, together with the free admissioi 
 of sunlight. In considering the problem of ventilation, we must also remember that an adult give 
 off from 25 to 40 oz. of water by the skin and lungs. The nature of the organic matters is no 
 precisely known, but some of it is particulate, consisting of epithelium, fatty matters, and organi 
 vapors from the lungs and mouth {Parkes). It blackens sulphuric acid, and decolorizes a weal 
 solution of potassic permanganate. As a test, if we expire through distilled water, and this watc 
 be set aside for some time in a warm place, it will soon become fcetid.] 
 
 [We must also take into consideration the products of combustion ; thus 1 cubic foot of cos 
 gas, when bumed, destroys all the O in 8 cubic feet of air {Parkes). ] 
 
THE SPUTUM. 227 
 
 thods. — In ordinary rooms, where every person is allowed the necessary cubic space (looo 
 feet) the air is sufficiently renewed by means of the pores in the walls of the room, by the 
 lg and shutting of doors, and by the fireplace, provided the damper is kept open, 
 i most important to notice that the natural ventilation be not interlered with by dampness of the 
 for this influences the pores very greatly. At the same time, damp walls are injurious to 
 i by conducting away heat, and in them the germs of infectious diseases may develop (Lind- 
 
 atural Ventilation. — By this term is meant the ventilation brought about by the ordinary 
 acting in nature ; such as diffusion of gases, the action of winds, and the movements excited 
 ; to the different densities of air at unequal temperatures.] 
 
 rtificial Ventilation. — Various methods are in use for ventilating public buildings and dwell- 
 juses. Two principles are adopted for the former, viz., extraction and propulsion of air. 
 : former method the air is sucked out of the rooms by a fan or other apparatus, while in the 
 air is forced into the rooms, the air being previously heated to the necessary temperature.] 
 very convenient method of introducing air into a room, is by means of Tobin's tubes, 
 1 in the walls. The air enters through these tubes from the outside near the floor, and is 
 d up six or more feet, to an opening in the wall ; the cool air thus descends slowly. For a 
 ' room a convenient plan of window ventilation is that of H. Bird, viz. : Raise the lower 
 ind place under it, so as to fill up the opening, a piece of wood 3 or 4 inches high. Air will 
 pass in, in an upward direction, between the upper part of the lower sash frame and the lower 
 if the upper one.] 
 
 ; 8. FORMATION OF MUCUS IN THE RESPIRATORY PAS- 
 SES — SPUTUM. — The respiratory mucous membrane is covered normally 
 a thin layer of mucus (Fig. 125). By its presence this substance so far inhib- 
 le formation of new mucus by protecting the mucous glands from the action 
 old or other irritative agents. New mucus is secreted as that already formed 
 moved. An increased secretion accompanies congestion of the respiratory 
 ous membrane [or any local irritation]. Division of the nerves on one side of 
 :rachea (cat) causes redness of the tracheal mucous membrane and increased 
 :tion (RossbacK), [but the two processes do not stand in the relation of cause 
 effect]. [The secretion cannot be excited by stimulating the nerves going to 
 mucous membrane. This merely causes anaemia of the mucous membrane, 
 e the secretion continues.] 
 
 Fects of Reagents on the Mucous Secretion. — If ice be placed on the belly of an animal 
 1 to cause the animal to '* take a cold" the respiratory mucous membrane first becomes pale, 
 ifterward there is a copious mucous secretion, the membrane becoming deeply congested. The 
 :ion of sodium carbonate and ammonium chloride into the blood limits the secretion. The 
 application of alum, silver nitrate, or tannic acid, makes the mucous membrane turbid, and the 
 ehum is shed. The secretion is excited by apomorphin, emetin, pilocarpin, and ipecacuanha 
 1 given internally, while it is limited by atropin and morphia {Rossbach). 
 
 Expectorants favor the removal of the secretions from the air passages. This they may do 
 r by (a) altering the character and qualities of the secretion itself, or (b) by affecting the expul- 
 mechanism. Some of the drugs already mentioned are examples of the first class. The second 
 act chiefly by influencing the respiratory centre, such as ipecacuanha, strychnia, ammonia, 
 ;a; emetics also act energetically as expectorants, as in some cases of chronic bronchitis; 
 ith.and moisture of the air are also powerful adjuncts.] 
 
 lormal Sputum. — Under normal circumstances some mucus — mixed with a 
 s saliva — may be coughed up from the back of the throat. In catarrhal con- 
 jns of the respiratory mucous membrane, the sputum is greatly increased in 
 unt, and is often mixed with other characteristic products. Microscopic- 
 ', sputum contains — 
 
 . Epithelial Cells — chiefly squames from the mouth and pharynx (Fig. 144), 
 e rarely alveolar epithelium and ciliated epithelium (7) from the respiratory 
 ages. The epithelial cells are often altered, having undergone maceration or 
 :r changes. Thus some cells may have lost their cilia (6). 
 
 le epithelium of the alveoli (2) is squamous epithelium, the cells being two to four times the 
 3th of a colorless blood corpuscle. These cells occur chiefly in the morning sputum in indi- 
 ils over 30 years of age. In younger persons their presence indicates a pathological condition 
 le pulmonary parenchyma (Guttman,H. Schmidt, and Bizzozero). They often undergo fatty 
 neration, and they may contain pigment granules (3) ; or they may present the appearance of 
 
228 
 
 THE SPUTUM. 
 
 what Buhl has called " myelin degenerated cells" i. c, cells filled with clear refractive drops of vari 
 ous sizes, some colorless, others colored particles, the latter having been absorbed (4). Mucin ii 
 the form of myelin drops (5) is always present in sputum. 
 
 2. Lymphoid cells (9) are to be regarded as colorless blood corpuscles whicl 
 have wandered out of the blood vessels ; they are most numerous in yellow sputum 
 and less numerous in the clear, mucus-like excretion. The lymph cells often pre 
 sent alterations in their characters ; they may be shriveled up, fatty, or present ; 
 granular appearance. 
 
 The fluid substance of the sputum contains much mucus arising from the mucous 
 glands and goblet cells ; together with nuclein, and lecithin, and the constituent! 
 of saliva according to the amount of the latter mixed with the secretion. Albu 
 min occurs only during inflammation of the respiratory passages, and its amouni 
 increases with the degree of inflammation. Urea has been found in cases o: 
 nephritis. 
 
 F'G. 144. 
 
 Various objects found* in sputum. I, Detritus and particles of dust; 2, alveolar epithelium with pigment _; 3, fatty 
 and partly pigmented alveolar epithelium ; 4, alveolar epithelium containing myelin forms ; 5, free myelin forms ; 
 6, 7, ciliated epithelium, some changed, others without cilia ; 8, squamous epithelium from the mouth ; 9, leu- 
 cocytes ; io, elastic fibres ; n, fibrin cast of a small bronchus ; 12, leptothrix buccalis with cocci, bacteria, and 
 spirochaetae ; a, fatty acid crystals and free fatty granules ; b, haematoidin ; c, Charcot's crystals ; d, Cholesterin. 
 
 Pathological. — In cases of catarrh, the sputum is at first usually sticky and clear (sputa cruda), hut 
 later it becomes more firm and yellow (sputa cocta). Under pathological conditions there may be 
 found in the sputum — (a) red blood corpuscles, from rupture of a blood vessel, (i) Elastic 
 fibres (10) from disintegration of the alveoli of the lung; usually the bundles are fine, curved, and 
 the fibres branched. [In certain cases it is well to add a solution of caustic potash, which dissolves 
 most of the other elements, leaving the elastic fibres untouched.] Their presence always indicates 
 destruction of the lung tissue, (c) Colorless plugs of fibrin (n), casts of the smaller or larger 
 bronchi, occur in some cases of fibrinous exudation into the finer air passages, (d) Crystals of 
 various kinds — crystals of fatty acids (Fig. 144, a) in bundles of fine needles. They indicate great 
 decomposition of the stagnant secretion. Leucin and tyrosin crystals are rare ($ 269). Tyrosin 
 occurs in considerable amount when an old abscess breaks into the lungs (Leyden, Kannenberg). 
 Colorless, sharp-pointed, octagonal or rhombic plates — Charcot's crystals (c) — have been found 
 in the expectoration in asthma, and exudative affections of the bronchi. Hamatoidin (b) and 
 cholesterin crystals (d) occur much more rarely. 
 
 Fungi and other lowly organisms are taken in during inspiration (§ 136). The threads 
 of Leptothrix buccalis (12) detached from the teeth, are frequently found (| 147). Mycelium and 
 
ACTION OF DIMINISHED ATMOSPHERIC PRESSURE. 229 
 
 are found in thrush (Oidium albicans), especially in the mouths of sucking infants. In mal- 
 ts expectoration rod-shaped bacteria are present. In pulmonary gangrene are found monads, 
 rcomonad (Kannenberg) ; in pulmonary phthisis the tubercle bacillus {R. Koch) ; very rarely 
 l, which, however, is often found in gastric catarrh in the stomach, and also in the urine (Fig. 
 jo). 
 
 rsical Characters. — Sputum, with reference to its physical characters, is described as 
 s, muco-purulent, ox purulent. 
 
 lormal coloration of the sputum — red from blood. When the blood remains long in the 
 undergoes a regular series of changes, and tinges the sputum dark red, bluish brown, brown- 
 low, deep yellow, yellowish green, or grass green. The sputum is sometimes yellow in jaun- 
 The sputum may be tinged by what is inspired [as in the case of the "black spit" of miners]. 
 ; odor of the sputum is more or less unpleasant. It becomes very disagreeable when it has 
 led long in pathological lung cavities, and it is stinking in gangrene of the lung. 
 
 3. ACTION OF THE ATMOSPHERIC PRESSURE.— At the 
 
 al pressure of the atmosphere (height of the barometer, 760 millimetres Hg), 
 jre is exerted upon the entire surface of the body = 15,000 to 20,000 kilos., 
 ding to the extent of the superficial area {Galileo). This pressure acts equally 
 
 1 sides upon the body, and occurs also in all internal cavities containing air, 
 those that are constantly filled with air (the respiratory passages and the 
 s in the superior maxillary, frontal and ethmoid bones), and those that are 
 orarily in direct communication with the outer air (the digestive tract and 
 anum). As the. fluids of the body (blood, lymph, secretions, parenchymatous 
 >) are, practically, incompressible, their volume remains practically unchanged 
 r the pressure ; but they will absorb gases from the air corresponding to the 
 tiling pressure {i. e., the partial pressure of the individual gases), and accord- 
 3 their temperature (compare § 33.) 
 
 e solids consist of elementary parts (cells and fibres), each of which presents 
 a microscopic surface to the pressure, so that for each cell the prevailing 
 ure of the air can only be calculated at a few millimetres — a pressure under 
 h the most delicate histological tissues undergo development. As an example 
 e action of the pressure of the atmospheric pressure upon large masses, take 
 Drought about by the adhesion of the smooth, sticky, moist, articular surfaces 
 
 2 shoulder and hip joints. In these cases, the arm and the leg are supported 
 >ut the action of muscles. The thigh bone remains in its socket after section 
 
 1 the muscles and its capsule {Brothers Weber). Even when the cotyloid 
 y is perforated, the head of the femur does not fall out of its socket. The 
 lary barometric variations affect the respiration — a rise of the barometric 
 ure excites, while a fall diminishes, the respirations. The absolute amount 
 
 2 remains the same (§ 127, 8). 
 
 jreat Diminution of the Atmospheric Pressure, such as occurs in ballooning (highest 
 , 8600 metres), or in ascending mountains, causes a series of characteristic phenomena: (1) 
 asequence of the diminution of the pressure upon the parts directly in contact with the air, 
 ecome greatly congested ; hence, there is redness and swelling of the skin and free mucous 
 ranes; there may be hemorrhage from the nose, lungs, gums, turgidity of the cutaneous veins, 
 is secretion of sweat, great secretion of mucus. ( 2 ) A feeling of weight in the limbs, a press- 
 tward of the tympanic membrane (until the tension is equilibrated by opening the Eustachian 
 and, as a consequence, noises in the ears and difficulty of hearing. (3) In consequence of 
 minished tension of the O in the air (J 129), there is difficulty of breathing, pain in the chest, 
 by the respirations (and pulse) become more rapid, detper and irregular. When the atmo- 
 c pressure is diminished J--J, the amount of O in the blood is diminished {Bert, Frankel and 
 rt), the C0 2 is imperfectly removed from the blood, and, in consequence, there is diminished 
 ion within the body. When the atmospheric pressure is diminished to one-half, the amount 
 \ in arterial blood is lessened ; and the amount of N diminishes proportionplly with the de- 
 
 of the atmospheric pressure {Frankel and Geppert). The diminished tension of the air 
 its the vibrations of the vocal cords from occurring so forcibly, and, hence, the voice is feeble. 
 1 consequence of the amount of blood in the skin, the internal organs are relatively anaemic ; 
 , there is diminished secretion of urine, muscular weakness, disturbances of digestion, dullness 
 
 senses, and, it may be, unconsciousness, and all these phenomena are intensified by the con- 
 5 mentioned under (3). Some of the«e phenomena are modified by usage. The highest limit 
 ch a man may still retain his senses is placed by Tissandier at an elevation of 8000 metres 
 
230 HISTORICAL. 
 
 (280 mm. Hg). In dogs, the blood pressure falls, and the pulse becomes small and diminished ii 
 frequency when the atmospheric pressure falls to 200 mm. Hg. 
 
 Those who live upon high mountains suffer from a disease, mal de montagne, which consists 
 essentially, in the above symptoms, although it is sometimes complicated with anaemia of the interna 
 organs. Al. v. Humboldt found that in those who lived on the Andes the thorax was capacious 
 At 6000 to 8000 feet above sea level, water contains only one-third of the absorbed gases, so tha 
 fishes cannot live in it [Boussingault). Animals may be subjected to a further diminution of thi 
 atmospheric pressure by being placed under the receiver of an air pump. Birds die when thi 
 pressure is reduced to 120 mm. Hg; mammals, at 40 mm. Hg; frogs endure repeated evacuation 
 of the receiver, whereby they are much distended, owing to the escape of gases and water ; but afte 
 the entrance of air, they become greatly compressed. The cause of death in mammals is ascribec 
 by Hoppe-Seyler to the evolution of bubbles of gas in the blood; these bubbles stop up the capilla 
 ries and the circulation is arrested. Local diminution of the atmospheric pressure causes markec 
 congestion and swelling of the part, as occurs when a cupping glass is used. 
 
 Great Increase of the Atmospheric Pressure. — The phenomena which are, for the mosl 
 part, the reverse of the foregoing, have been observed in pneumatic cabinets and in diving bells 
 where men may work even under 4^ atmospheres pressure. The phenomena are : (1) Palenes: 
 and dryness of the external . surfaces, collapse of the cutaneous veins, diminution of perspiratior 
 and mucous secretions. (2) The tympanic membrane is pressed inward (until the air escape! 
 through the Eustachian tube, after causing a sharp sound), acute sounds are heard, pain in the ears 
 and difficulty of hearing. (3) A feeling of lightness and freshness during respiration, the respira 
 tion'becomes slower (by 2-4 per minute), inspiration easier and shorter, expiration lengthened, the 
 pause distinct. The capacity of the lungs increases, owing to the freer movement of the diaphragm 
 in consequence of the diminution of the intestinal gases. Owing to the more rapid oxidations ir 
 the body, muscular movement is easier and more active. The O absorbed and the C0 2 excreted 
 are increased. The venous blood is reddened. (4) Difficulty of speaking, alteration of the tone 
 of the voice, inability to whistle. (5) Increase of the urinary secretion, more muscular energy 
 more rapid metabolism, increased appetite, subjective feeling of warmth, pulse beats slower, and 
 pulse curve is lower (compare \ 74). In animals subjected to excessively high atmospheric pressure, 
 P. Bert found that the arterial blood contained 30 vols, per cent. O (at 760 mm. Hg) ; when the 
 amount rose to 35 vols, per cent, death occurred, with convulsions. Compressed air has been used 
 for therapeutical purposes, but in doing so a too rapid increase of the pressure is to be avoided, 
 Waldenburg has constructed such an apparatus, which may be used for the respiration of air undei 
 a greater or less pressure. 
 
 Frogs, when placed in comprfssed O (at 14 atmospheres), exhibit the same phenomena as il 
 they were in a vacuum, or pure N. There is paralysis of the central nervous system, sometimes 
 preceded by convulsions. The heart ceases to beat (not the lymph hearts), while the excitability 
 of the motor nerves is lost at the same time, and, lastly, the direct muscular excitability disappears 
 {K. B. Lehmann). An excised frog's heart placed in O, under a very high pressure (13 atmo- 
 spheres), scarcely beats one-fourth of the time during which it pulsates in air. If the heart be 
 exposed to the air again, it begins to beat ; so that compressed renders the vitality of the heart 
 latent before abolishing it. 
 
 Phosphorus retains its luminosity under a high pressure in O (Schonbein), but this is not the case 
 with the luminous organisms, e.g., Lampyris, and luminous bacteria [JC. B. Lehmann). A very 
 high atmospheric pressure is also injurious to plants. 
 
 140. COMPARATIVE AND HISTORICAL.— Mammals have lungs similar to those o( 
 
 . man. The lungs of birds are spongy, and united to the chest wall, while there are openings on 
 
 A their surface communicating with thin- walled " air sacs," which are placed among the viscera. The 
 
 lair sacs communicate with cavities in the bones, which give the latter great lightness {Aristotle). 
 
 The diaphragm is absent. In reptiles the Tungs are divided into greater and smaller compartments ; 
 
 in snakes one lung is abortive, while the other has the elongated form of the body. The amphibians 
 
 (frog) possess two simple lungs, each of which represents an enormous infundibulum with its alveoli. 
 
 The frog pumps air into its lungs by the contraction of its throat, the nostrils being closed and the 
 
 glot f is opened. When young — until their metamorphosis — frogs breathe like fishes, by means oi 
 
 gills. The perennibranchiate amphibians (Proteus) retain their gills throughout life. Among 
 
 fishes, which breathe by gills and use the O absorbed by the water, the Dipnoi have, in addition 
 
 to gills, a swim bladder, provided with afferent and efferent vessels, which is comparable to the lung. 
 
 f The Cobitis respires also with its intestine (Erman, 1808). Insects and centipedes respire by 
 
 " tracheae," which are branched canals distributed throughout the body ; they open on the surface 
 
 of the body by openings (stigmata), which can be closed. Spiders respire by means of tracheae 
 
 and tracheal sacs ; crabs, by gills. The molluscs and cephalopods have gills ; some gasteropods 
 
 have gills and others lunss. Among the lower invertebrata some breathe by gills, others by means 
 
 of a special " water vascular system," and others again by no special organs. 
 
 Historical. — Aristotle (384 B. c.) regarded the object of respiration to be the cooling of the body, 
 so as to moderate the internal warmth. He observed correctly that the warmest animals breathe 
 most actively, but in interpreting the fact he reversed the cause and effect. Galen (131-203 A. D.) 
 thought that the " soot " was removed from the body along with the expired water. The most im- 
 
HISTORICAL. 231 
 
 nt experiments on the mechanics of respiration date from Galen ; he observed that the lungs 
 yely follow the movements of the chest ; that the diaphragm is >t "' mr ef * mportant m usclg, of | 
 ration; that the external intercostals are inspiratory, and the internal, expiratory. HeTKvided 
 itercostal nerves and muscles, and observed that loss of voice occurred. On dividing the spinal 
 higher and higher, he found that as he did so the muscles of the thorax lying higher up became 
 yzed. Oribasius (360 A. D.) observed that in double pneumothorax both lungs collapsed, 
 lius (1540) first described artificial respiration as a means of restoring the beat of the heart, 
 rtghi (1661) described the structure of the lungs. J. A. Borelli (f 1679) gave the first funda- 
 al description of the mechanism of the respiratory movements. The chemical processes of 
 ration could only be known after the discovery of the individual gases therein concerned. Van 
 lont (t 1644) detected C0 2 . [Joseph Black (1757) discovered, by the following experiment, 
 CO 2 or " fixed air " is given out during expiration : Take two jars of lime water, breathe into 
 hrough a bent glass tube, and force ordinary air through the other, when a white precipitate of 
 nm carbonate will be found to occur in the former.] In 1774 Priestley discovered O. Lavoisier 
 ;ted N (1775), and ascertained the composition of atmospheric air, and he regarded the forma- 
 af C0 2 and H z O of the breath as a result of a combustion within the lungs themselves. J. 
 n-Houss (1730-1790) discovered the respiration of plants. Vogel and others proved the exist- 
 of CO 2 in venous blood, and Hoffmann and ethers that of O in arterial blood. The more 
 jlete conception of the exchange of gases was, however, only possible after Magnus had 
 cted'and analyzed the gases of arterial and venous blood ($ 36). 
 
Physiology of Digestion. 
 
 141. THE MOUTH AND ITS GLANDS.— The mucous membrane of the cavity of the 
 mouth, which becomes continuous with the skin at the red margin of the lips, has a number of 
 sebaceous glands in the region of the red part of the lip. The buccal mucous membrane consists 
 of bundles of fine fibrous tissue mixed with elastic fibres, which traverse it in every direction. 
 Papilla; — simple or compound — occur near the free surfaces. The submucous tissue, which is 
 directly continuous with the fibrous tissue of the mucous membrane itself, is thickest where the 
 mucous membrane is thickest, and densest where it is firmly fixed to the 
 Fig. 145. periosteum of the bone and to the gum ; it is thinnest where the mucous 
 
 membrane is most movable, and where there are most folds. The cavity 
 of the mouth is lined by stratified squamous epithelium (Fig. 145), 
 which is thickest, as a rule, where the longest papillae occur. 
 
 All the glands of the mouth, including the salivary 
 glands, may be divided into different classes, according to 
 the nature of their secretions. 
 
 1. The serous or albuminous glands [true salivary], 
 whose secretion contains a certain amount of albumin, e.g., 
 the human parotid. 
 
 2. The mucous glands, whose secretion, in addition to 
 some albumin, contains .the characteristic constituent 
 mucin. 
 
 3. The mixed [or muco-salivary~\ glands, some of the 
 acini secreting an albuminous fluid and other mucin, e.g., 
 the human maxillary gland {Heidenhain). The structure 
 
 e lpi°heuim" detachedTrom of these glands is referred to under the salivary glands. 
 
 Numerous mucous glands (labial, buccal, palatine, lingual, molar) 
 have the appearance of small macroscopic bodies lying in the sub-mucosa. They are branched 
 tubular glands, and the contents of their secretory cells consist partly of mucin, which is expelled 
 from them during secretion. The excretory ducts of these glands, which are lined by cylindrical 
 epithelium, are constricted where they enter the mouth. Not unfrequently one duct receives the 
 secretion of a neighboring gland. 
 
 The glands of the tongue form two groups which differ morphologically and physiologically. 
 (1) The mucous glands (Weber's glands), occurring chiefly near the "root of the tongue, are 
 branched tubular glands lined with clear, transparent, secretory cells whose nuclei are placed near the 
 attached end of the cells. The acini have a distinct membrana propria. (2) The serous glands 
 (Ebner's) are acinous glands occurring in the region of the circumvallate papillae (and in animals 
 near the papillae foliatae). They are lined with turbid granular epithelium with a central nucleus, 
 and they secrete saliva (Henle). (3) The glands of Blandin and Nuhn are placed near the tip of 
 the tongue, and consist of mucous and serous acini, so that they are mixed glands (Podwisotzky). 
 
 The blood vessels are moderately abundant, and the larger trunks lie in the sub mucosa, while 
 the finer twigs penetrate into the papillsa, where they form either a capillary network or simple 
 loops. 
 
 The larger lymphatics lie in the sub-mucosa, while the finer branches form a fine network 
 placed in the mucosa. The lymph follicles also belong to the lymphatic system ({S 197). On the 
 dorsum of the posterior part of the tongue they form an almost continuous layer. They are round 
 or oval (1-1.5 mm. in diameter), and placed in the sub-mucosa. They consist of adenoid tissue 
 loaded with lymph corpuscles. The outer part of the adenoid reticulum is compressed so as to form 
 a kind of capsule for each follicle. Similar follicles occur in the intestine as solitary follicles ; in 
 the small intestine they are collected together into Peyer's patches, and in the spleen they occur as 
 Malpighian corpuscles. On the dorsum of the tongue several of these follicles form a slightly 
 oval elevation, which is surrounded by connective tissue. In the centre of this elevation there is a 
 depression, into which a mucous gland opens, which fills the small crater with mucus (Fig. 146). 
 
 232 
 
THE SALIVARY GLANDS. 
 
 233 
 
 ; Tonsils have fundamentally the same structure. On their surface are a number of depres- 
 into which the ducts of small mucous glands open. These depressions are surrounded by 
 s (10-20) of lymph follicles, and the whole is environed by a capsule of connective tissue. 
 E. H. Weber discovered lymphatics in the neighborhood of the tonsils, Briicke referred these 
 ires to the lymphatic system. Large lymph spaces, communicating w ith lymphatics, occur in 
 :ighborhood of the tonsils, but as yet a direct connection between the spaces in the follicles 
 he lymph vessels has not been proved to exist. Similar structures occur in the tubal and 
 mgeal tonsils. [Stohr asserts that an enormous number of leucocytes wander out of the 
 >, solitary and Peyer's glands, and the adenoid tissue of the bronchial mucous membrane. The 
 jass out between the epithelial cells, but do not pass into the interior of the latter.] 
 rves. — Numerous medullated nerve fibres occur in the sub-mucosa, pass into the mucosa, and 
 late partly in the individual papillae in Krause's end bulbs, which are most abundant in the lips 
 jft palate, and not so numerous in the cheeks and in the floor of the mouth. The nerves ad- 
 :er not only to common sensation, but they also are the organs of transmission for tactile (heat 
 ressure) impressions. It is highly probable, however, that some nerve fibres end in fine ter- 
 fibrils, between the epithelial cells, such as occur in the cornea and elsewhere. 
 
 2. THE SALIVARY GLANDS.— Structure of the Ducts.— The 
 
 : pairs of salivary glands, sub-maxillary, sublingual, and parotid, are com- 
 d tubular glands. Fig. 148, A, shows a fine duct, terminating in the more or less 
 ■shaped alveoli or acini. [Each gland consists of a number of lobes, and 
 
 Fig. 146. 
 
 Closed follicle. 
 
 Mucous gland 
 
 Epithelium. 
 
 Closed follicles. 
 
 Mucous gland. 
 
 Section of a mucous follicle from the dorsum of the tongue (Schenk). 
 
 lobe in turn of a number of lobules, which again are composed of acini. 
 ;hese are held together by a framework of connective tissue. The larger 
 :hes of the duct lie between the lobules, and constitute the interlobular 
 :, giving branches to each lobule which they enter, constituting the intra- 
 lar ducts. These intralobular ducts branch and finally terminate in connection 
 the alveoli, by means of an intermediary or intercalary part. The larger 
 lobar and interlobular ducts consist of a membrana propria, strengthened 
 de with fibrous and elastic tissue, and in some places also 
 sn-striped muscle, while the ducts are lined by columnar 
 elial cells. In the largest branches there is a second row 
 laller cells, lying between the large cells and the mem- 
 1 propria. The intralobular ducts are lined by a single 
 of large cylindrical epithelium. As is shown in Fig 1 . 147, 
 ucleus occurs about the middle of the cell, while the outer 
 i. e. , next the basement membrane of the cell, is finely 
 ed longitudinally, which is due to fibrillae ; the inner half 
 the lumen is granular. The intermediary part is narrow, Rodded epithelium lin- 
 s lined by a single layer of flattened cells, each with an 2f n d d uct of a salivary 
 
 Fig. 
 
234 
 
 THE STRUCTURE OF THE SALIVARY GLANDS. 
 
 elongated oval nucleus. There is usually a narrow "neck," where the intr; 
 lobular duct becomes continuous with the intermediary part, and here the eel 
 are polyhedral {Klein). 
 
 The acini, or alveoli, are the parts where the actual process of secretion take 
 place. They vary somewhat in shape ; some are tubular, others branched, som 
 are dilated and resemble a Florence flask, and several of them usually open int 
 one intermediary part of a duct. Each alveolus is bounded by a basement men 
 brane, with a reticulate structure made up of nucleated, branched, and anastomo: 
 ing cells, so as to resemble a basket (D). There is a homogeneous membran 
 bounding the alveoli in addition to this basket-shaped structure. Immediate! 
 outside this membrane is a lymph space ( Giatiuzzi), and outside this again the nei 
 work of capillaries is distributed. [The extent to which this lymph space is fille 
 with lymph determines the distance of the capillaries from the membrana propri; 
 The inter-alveolar lymph spaces communicate with large lymph spaces betwee 
 the lobules, which in turn communicate with perivascular lymphatics around th 
 arteries and veins.] The lymphatics emerge from the gland at the hilum. 
 
 The secretory cells Vary in structure, according as the salivary gland : 
 
 A, duct and acini of the parotid gland of a dog : B, acini of the sub-maxillary gland of a dog ; c, refractive mucoi 
 cells ; d, granular half-moons of Gianuzzi ; C, similar alveoli after prolonged secretion ; D, basket-shaped tissi 
 investment of acinus ; F, entrance of a non-medullated nerve fibre into a secretory cell. 
 
 mucous [sub-maxillary and sublingual of the dog and cat], a serous [paroti 
 of man and mammals, and sub-maxillary of rabbit], or a mixed gland [huma 
 sub maxillary and sublingual]. 
 
 Mucous Acini. — The secretory cells of mucous glands, and . the mucot 
 acini of mixed glands (Fig. 149), are lined by a single layer of " mucin cells ' 
 {Heidenhain) (Fig. 148, B, e), which are large cells distended with mucin, or, i 
 least, with a hypothetical substance, mucigen, which yields mucin. The muci 
 cells are more or less spheroidal in shape,, clear, shining, highly refractive, an 
 nearly fill the acinus. The flattened nucleus is near the wall of the acinus. Eac 
 cell has a fine process which overlaps the fixed parts of the cell next to it. Owin 
 to the fact that the body of each cell is infiltrated with mucin, these cells do nc 
 stain with carmine, although the nucleus and its immediately investing protoplasi 
 do. Another kind of cell occurs in the sub-maxillary gland of the dog. 
 forms a half-moon-shaped structure lying in direct contact with the wall of th 
 acinus {Gianuzzi). Each " half-moon " or " crescent " consists of a numbf 
 of small, closely packed, angular, strongly albuminous cells with small ov: 
 nuclei, which, however, are separated only with difficulty. Hence, Heidenhai 
 
HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 
 
 235 
 
 called them "composite marginal cells" (B, d). They are granular, 
 er, devoid of mucin, and stain readily with pigments. [In the sub-maxillary 
 d of the cat there is a complete layer of these " marginal " carmine-staining 
 lying between the mucous cells and the membrana propria.] 
 Serous Acini. — In true serous glands (parotid of man and mammals) and 
 le serous acini of mixed glands, the acini are lined by a single layer of secre- 
 , columnar, finely granular cells, which, in the quiescent condition, completely 
 he acinus, so that scarcely any lumen is left. Just before secretion, or when 
 ; cells are quiescent, Langley has shown that they are large and filled with 
 erous granules, which obscure the presence of the nucleus. As secretion 
 s place, these granules seem to be used up or discharged into the lumen ; at 
 , the outer part of each cell gradually becomes clear and more transparent, 
 this condition spreads toward the inner part of the cell.] 
 n the mixed or muco-salivary glands (Klein) (e.g., human sub-maxillary), 
 i of the alveoli are mucous and others serous in their characters, but the 
 :r are always far more numerous, and the one kind of acinus is directly 
 inuous with the others (Fig. 149)-] 
 
 Fig. 149. 
 
 n of part of the human sub-maxillary gland. On the left of the figure is a group of serous alveoli, and on the 
 right a group of mucous alveoli. 
 
 [3. HISTOLOGICAL CHANGES DURING THE ACTIVITY 
 THE SALIVARY GLANDS.— [The condition of physiological activity 
 tie gland cells is accompanied by changes in the histological characters of the 
 story cells.] 
 
 Serous Glands. — The changes in the secretory cells have been carefully 
 ied in the parotid of the rabbit. The histological appearances vary some- 
 t, according as the glands are examined in the fresh condition or after harden- 
 in various reagents, such as absolute alcohol. When the gland is at rest, in 
 sparation hardened in alcohol, and stained with carmine, the cells consist of 
 le, almost uncolored substance, with a few fine granules, and a small, irregu- 
 red-stained, shriveled nucleus, devoid of nucleolus. The appearance of the 
 eus suggests the idea of its being shriveled by the action of the harden- 
 reagent (Fig. 150).] 
 
 During activity, if the gland be caused to secrete by stimulating the sym- 
 etic, all parts of the cells undergo a change (Fig. 150, 151). (1) The cells 
 inish somewhat in size; (2) the nuclei are no longer irregular, but round, 
 
236 HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 
 
 with a sharp contour and nucleoli ; (3) the substance of the cell itself is turbid 
 owing to the diminution of the clear substance, and the increase of the granules 
 especially near the nuclei; (4) at the same time, the whole cell stains more deep] 
 with carmine {Heidenhain).'] 
 
 [On studying the changes which occur in a living serous gland, Langle 
 found that, during rest, the substance of the cells of the parotid is pervaded b 
 fine granules, which are so numerous as to obscure the nucleus, while the outline 
 of the cells are indistinct. No lumen is visible in the acini during activity, thi 
 granules disappear from the outer zone of the cells, the cells themselves becoming 
 more distinct and smaller. After prolonged secretion, the granules largely dis 
 appear from the cell substance except quite near the inner margin. The cells an 
 smaller, their outlines more distinct, their round nuclei apparent, and the lumei 
 of the acini is wide and distinct. Thus, it is evident that, during rest, granule: 
 are manufactured, which disappear during the activity of the cells, the disappear 
 ance taking place from without inward. Similar changes occur in the cells 
 the pancreas.] 
 
 [Mucous Glands. — More complex changes occur in the mucous glands, sue! 
 as the sub-maxillary or orbital glands of the dog (Lavdovsky). The appearance: 
 vary according to the intensity and duration of the secretory activity. Th< 
 
 Fig. 150. Fig 151. 
 
 
 
 ^^^^^^^^ ^IP 13 ' 
 
 Sections of a "serous" gland. The parotid of a rabbit, Fig. 150, at rest; Fig. 151, after stimulation of the cervica 
 
 sympathetic. 
 
 mucous cells at rest are large, clear, and refractive, containing a flattened nucleui 
 (Fig. 148, B, c), surrounded with a small amount of protoplasm, and placed neai 
 the basement membrane. The clear substance does not stain with carmine, and 
 consists of mucigen lying in the wide spaces of an intracellular plexus of fibrils, 
 After prolonged secretion, produced, it may be, by strong and continued 
 stimulation of the chorda, the mucous cells of the sub-maxillary gland of the dog 
 undergo a great change.] The distended, refractive, and "mucous cells," whicl; 
 occur in the quiescent gland, and which do not stain with carmine, do not appeal 
 after the gland has been in a state of activity. Their place is taken by small, dark 
 protoplasmic cells devoid of mucin (Fig. 148, C). These cells readily stain witl 
 carmine, while their nucleus is scarcely, if at all, colored by the dye. Th( 
 researches of R. Heidenhain (1868) have shed much light on the secretory activit] 
 of the salivary glands. 
 
 The change may be produced in two ways. Either it is due to the "mucous cells" during 
 secretion becoming broken up, so that they yield their mucin directly to the saliva; in saliva ricl 
 in mucin, small microscopic pieces of mucin are found, and sometimes mucous cells themselves an 
 present. Or, we must assume that the mucous cells simply eliminate the mucin from their boiiie: 
 (Ewald, Stohr) ; while, after a period of rest, new mucin is formed. According to this view, th< 
 dark granular cells of the glands, after active secretion, are simply mucous cells, which have givei 
 out their mucin. If we assume, with Heidenhain, that the mucous cells break up, then thesi 
 
ACTION OF NERVES ON THE SECRETION OF SALIVA. 237 
 
 ir non mucous cells must be regarded as new formations produced by the proliferation and 
 i of the composite marginal cells, i. e., the crescents, or half-moons of Gianuzzi. 
 
 uring rest, the protoplasm seems to manufacture mucigen, which is changed 
 nd discharged as mucin in the secretion, when the gland is actively secreting. 
 , the cells become smaller, but the protoplasm of the cell seems to increase, 
 nucigen is manufactured during rest, and the cycle is repeated.] 
 
 \. THE NERVES OF THE SALIVARY GLANDS.— The nerves 
 ir the most part medullated, and enter at the hilum of the gland, where they 
 a rich plexus provided with ganglia between the lobules. [According to 
 i, there are no ganglia in the parotid gland.] (Krause, Reich, Schliiter.) 
 . the salivary glands are supplied by branches from two different nerves — 
 the sympathetic and from a cranial nerve. 
 
 The sympathetic nerve gives branches to (a) the sub-maxillary and the 
 igual giands, derived from the plexus on the external maxillary artery ; {/>) 
 3 parotid gland from the carotid plexus. 
 
 The facial nerve gives branches to the sub-maxillary and sublingual glands 
 the chorda tympani which accompanies the lingual branch of the fifth nerve, 
 branches to the parotid reach it in a roundabout way. They arise from the 
 anic branch of the glosso-pharyngeal nerve (dog). The tympanic plexus 
 ; fibres to the small superficial petrosal nerve {Eckhard), and with it these 
 i run to the anterior surface of the pyramid in the temporal bone, emerging 
 the skull through a fissure between the petrous and great wing of the sphenoid, 
 hen joining the otic ganglion. This ganglion sends branches to the auriculo- 
 oral nerve (itself derived from the third branch of the trigeminus), which, as 
 ises upward to the temporal region, under cover of the parotid, gives branches 
 is gland (v. WitticK). 
 
 le sub-maxillary ganglion, which gives branches to the sub-maxillary and 
 ngual glands, receives fibres from the tympanico-lingual nerve (Chorda tym- 
 I, as well as sympathetic fibres from the plexus on the external maxillary 
 
 V- 
 
 ;rmination of the Nerve Fibres. — With regard to the ultimate distribu- 
 of these nerves we can distinguish (r) the vasomotor nerves, which give 
 :hes to the walls of the blood vessels, and (2) the secretory nerves proper, 
 er states, with regard to the latter, that (a) medullated nerve fibres penetrate 
 cini; the sheath of Schwann (gray sheath) unites with the membrana propria 
 ie acinus ; the medullated fibre — still medullated — passes between the secre- 
 cells, where it divides and becomes non-medullated, and its axial cylinder 
 inates in connection with the nucleus of a secretory cell. [This, however, 
 t proved] (Fig. 148, F). 
 
 According to Pfliiger, some of the nerve fibres end in multipolar ganglion cells, which lie out- 
 le wall of the acinus, and these cells send branches to the secretory cells of the acini. [These 
 jrobably correspond to the branched cells of the basket-shaped structure.] 
 Again, he describes medullated fibres which enter the attached end of the cylindrical epithe- 
 ining the excretory ducts of the glands (E). Pfliiger thinks that those fibres entering the 
 directly are cerebral, while those with ganglia in their course are derived from the sympathetic 
 1. 
 
 ) The direct termination of nerve fibres has been observed in the salivary glands of the cock- 
 by Kupffer.] 
 
 5. ACTION OF THE NERVOUS SYSTEM ON THE SECRE- 
 iN OF SALIVA.— (A) Sub-maxillary Gland.— Stimulation of the facial 
 re at its origin {Ludwig and Rahri) causes a profuse secretion of a thin 
 ery saliva, which contains a very small amount of specific constituents 
 hard). Simultaneously with the act of secretion, the blood vessels of the 
 Is become dilated, and the capillaries are so distended that the pulsatile 
 :ment in the arteries is propagated into the veins. Nearly four times as much 
 i flows out of the veins (67. Bernard), the blood being of a bright red color, 
 
238 ACTION OF NERVES ON THE SECRETION OF SALIVA. 
 
 and contains one-third more O than the venous blood of the non-stimulate 
 gland. Notwithstanding this relatively high percentage of O, the secreting glan 
 uses more O than the passive gland (§ 131, 1). 
 
 [I. Stimulation of Chorda. — If a cannula be placed in Wharton's duct, e.g 
 in a dog, and the chorda tympani be divided, no secretion flows from the cannul; 
 On stimulating the peripheral end of the chorda tympani with an interrupted cu: 
 rent of electricity, the same results — copious secretion of saliva and vascular dili 
 tation, with increased flow of blood and lymph, through the gland — occur as whe 
 the origin of the seventh nerve itself is stimulated The watery saliva is calle 
 chorda saliva.] 
 
 Two functionally different kinds of nerve fibres occur in the facial nerve — (] 
 true secretory fibres, (2) vaso-dilator fibres. The increased amount of seen 
 tion is not due simply to the increased blood supply, as is proved below. 
 
 II. Stimulation of the sympathetic nerve causes a scanty amount of 
 very thick, sticky, mucous secretion (Eckhard), in which the specific salivar 
 constituents, mucin, and the salivary corpuscles are very abundant. The specifi 
 gravity of the saliva is raised from 1007 to 1010. Simultaneously the blood ves 
 sels become contracted, so that the blood flows more slowly from the veins, an 
 has a dark bluish color. 
 
 The sympathetic also contains two kinds of nerve fibres — (1) true secretor; 
 fibres, and (2) vaso-constrictor fibres. 
 
 [Electrical Variations during Secretion. — That changes in the electromotive properties < 
 glands occur during secretion was shown in the frog's skin by Roeber, Engelmann, and Hermani 
 Bayliss and Bradford find that the same is true of the sub-maxillary gland (dog). During secretio 
 the excitatory change on stimulating the chorda is a. positive variation of the current of rest (th 
 hilus of the gland becoming more positive), but it is frequently followed by a second phase of opp< 
 site sign. The latent period is always very short, about 0.37". Atropin abolishes the chord 
 variation. On stimulating the sympathetic, the excitatory change is of an opposite sign to fhi 
 of the chorda, and the hilus becomes less positive, so that there is a negative variation. It require 
 a more powerful stimulus, is less in amount, and its latent period is longer (2." -/*/'), while atropi 
 lessens but does not abolish it.] 
 
 Relation to Stimulus. — On stimulating the cerebral nerves, at first with a weak and graduall 
 with a stronger stimulus, there is a gradual development of the secretion in which the solid constiti 
 ents — occasionally the organic — are increased (Heidenhain). If a strong stimulus be applied for 
 long time, the secretion diminishes, becomes watery, and is poor in specific constituents, especial! 
 in the organic elements, which are more affected than the inorganic (C. Ludwig and Becker). Aftf 
 prolonged stimulation of the sympathetic, the secretion resembles the chorda saliva. It would seen 
 therefore, that the chorda and sympathetic saliva are not specifically distinct, but vary only in dt 
 gree. On continuing the stimulation of the nerves up to a certain maximal limit, the rapidity c 
 secretion becomes greater, and the percentage of salts also increases to a certain maximum, and thi 
 independently of the former condition of the glands. The percentage of organic constituents als 
 depends on the strength of the nervous stimulation, but not on this alone, as it is essentially contir 
 gent upon the condition of the gland before the secretion took place, and it also depends upon th 
 duration and intensity of the previous secretory activity. Very strong stimulation of the gland leave 
 an " after effect " which predisposes it to give off organic constituents into the secretion (Heiden 
 hain). A latent period of 1.2 sec. (Ifering) to 24 sec. (Ludwig) may elapse between the nerv 
 stimulation and the beginning of the secretion. 
 
 [Langley has shown that in the cat the sympathetic saliva of the sub-maxillary gland is less visci 
 than the chorda saliva. The following table from Langley shows the difference in percentage com 
 position between the chorda and sympathttic saliva in the cat : — 
 
 Jfof 
 Organic $ of Ash. Total # 
 
 Substance. of Solids. 
 
 Sympathetic saliva (weak 1 
 
 stimulation .... \ , °3535 0.4419 0.7954 
 
 Sympathetic saliva after 1 
 
 5 mgrm. atropin I o 5250 0.4540 0.9790 
 
 (strong stimulation), J 
 Chorda saliva (weak 1 , ,, „ 
 
 stimulation) . . . . } °' 86 5 66 °-33978 1.20544 
 
 Chorda saliva (stronger ) „ ,„ , 
 
 stimulation) \ . . . } °'4 2 598 0.27568 0.70^ 
 
ACTION OF NERVES ON THE SECRETION OF SALIVA. 239 
 
 lation to Blood Supply. — The secretion of saliva is not simply the result 
 amount of blood in the glands; that there is a factor independent of the 
 es in the state of the vessels is shown by the following facts : — 
 
 The secretory activity of the glands when their nerves are stimulated continues for some time 
 ie blood vessels of the gland have been ligatured (Ludwig, Czermack, Gianuzzi). [If the 
 f a rabbit be cut off, stimulation of the seventh nerve, above where the chorda leaves it, causes 
 of saliva, which cannot be accounted for on the supposition that the saliva already present in 
 ivary glands is forced out of them. Thus we may have secretion without a blood stream, 
 liva is really secreted from the lymph present in the lymph spaces of the gland {Ludwig.)~\ 
 
 Atropin and Daturin extinguish the activity of the secretory fibres in 
 lorda tympani {Keuchel), that do not affect the vaso-dilator fibres {Heiden- 
 . The same results occur after the injection of acids and alkalies into the 
 tory duct (Gianuzzi). 
 
 The pressure in the excretory duct of the salivary gland — measured by 
 s of a manometer tied into it — may be nearly twice as great as the pressure 
 a the arteries of the glands (Ludwig), or even in the carotid itself. The 
 ire in Wharton's duct may reach 200 mm. Hg. 
 
 Just as in the case of muscles and nerves, the salivary glands become fatigued or exhausted 
 rolonged action. The result may also be brought about by injecting acids or alkalies into the 
 vhich shows that the secretory activity of the gland is independent of the circulation [_Gian- 
 
 .ction of Atropin. — The vascular dilatation and the increased flow of 
 l due to the activity of the secretory cells, produced by stimulation of the 
 ia tympani, although they occur simultaneously, do not stand in the relation 
 mse and effect. We may cause vascular dilatation without an increased flow 
 liva, as already stated (2). If atropin be given to an animal, stimulation of 
 horda produces dilatation of the blood vessels, but no secretion of saliva, 
 pin paralyzes the secretory fibres, but not the vaso-dilator fibres (Fig. 152). 
 increased supply of blood, while not causing, yet favors the act of secretion, 
 lacing a larger amount of pabulum at the disposal of the secretory elements, 
 ells.] 
 
 iecretory Pressure. — The experiment described under (3) proves, in a 
 ite manner, that the passage of the water from the blood vessels, or at least 
 
 the lymph into the acini of the gland, cannot be due to the blood pressure ; 
 
 in fact, it is not a mere process of filtration such as occurs in the glomeruli of 
 kidney. In the case of the salivary gland, where the pressure within the 
 i may be double that of the arterial pressure, the water actually moves from 
 lymph spaces against very great resistance. We can only account for this 
 t by ascribing it to the secretory activity of the gland cells themselves, 
 ther the activities of the gland cells, as suggested by Heidenhain, are 
 rned directly by two distinct kinds of nerve fibres, a set of solid -secreting 
 s, and a set of water-secreting fibres, remains to be proved.] 
 
 these facts lead us to conclude that the nerves exercise a direct effect upon the secretory cells, 
 from their action on the blood vessels. This physiological consideration goes hand in hand 
 the anatomical fact of the direct continuity of nerve fibres with the secretory cells. When the 
 la tympani is extirpated on one side in young dogs, the sub-maxillary gland on that side does 
 evelop so much — its weight is 50 per cent less — while the mucous cells and the " crescents " 
 nailer than on the sound side {Bufalini). 
 
 uring secretion the temperature of the gland rises 1.5 C. (Zudwig), and 
 blood flowing from the veins is often warmer than the arterial blood. [The 
 :tro-motive changes are referred to at p. 238.] 
 
 Paralytic Secretion" of Saliva. — By this term is meant the continued 
 stion of a thin, watery saliva from the sub-maxillary gland, which occurs 
 lty-four hours after the section of the cerebral nerves (chorda of the seventh), 
 , those branches of them that go to this gland, whether the sympathetic be 
 ded or not (CI. Bernard). It increases until the eighth day, after which it 
 
240 REFLEX SECRETION OF SALIVA. 
 
 gradually diminishes, while the gland tissue degenerates. The injection o 
 small quantity of curara into the artery of the gland also causes it. 
 
 [Heidenhain showed that section of one chorda is followed by a continuous secretion of sal 
 from both sub-maxillary glands. The term " paralytic " secretion is applied to that which ta 
 place on the side on which the nerve is cut, and Langley proposes to call the secretion on the op 
 site side the antilytic. The condition of apncea (| 368) stops almost or entirely both the pa 
 lytic and antilytic secretion, while dyspnoea increases the flow in both cases; and as section of 
 sympathetic fibres to the gland (where the chorda is cut) arrests the paralytic secretion excited 
 dyspnoea, it is evident that both the paralytic secretion and the secretion following dyspnoea : 
 caused by stimuli traveling down the sympathetic fibres {Langley). In the later stages of the pa 
 lytic secretion, the cause is in the gland itself, for it goes on even if all the nerves passing to I 
 gland be divided, and is probably due to a local ner.re centre. In this stage the secretion 
 arrested by a large dose of chloroform. The paralytic secretion in the first stage, according 
 Langley, is owing to a venous condition of the blood acting on a central secretory centre wh( 
 excitability is increased ; and in the latter stages probably on local nerve centres within the glai 
 The fibres of the chorda in the cat are only partially degenerated thirteen days after section (Lar, 
 ley).-] 
 
 [Histological Changes. — In the gland during paralytic secretion, the gland cells of the alve 
 (serous, mucous and demilunes), diminish in size and show the typical "resting" appearance, e\ 
 to a greater extent than the normal resting gland (Langley).] 
 
 (B) Sublingual Gland. — Very probably the same relations obtain as in i 
 sub- maxillary gland. 
 
 Fig. 152. 
 
 Vessels vr BtAtfo 
 
 Diagram of a salivary gland (Brunton). 
 
 (C) Parotid Gland. — In the dog, stimulation of the sympathetic alone caus 
 no secretion ; it occurs when the glosso-pharyngeal branch to the parotid is simu 
 taneously excited. This branch may be reached within the tympanum in the tyn 
 panic plexus. A thick secretion containing much organic matter is theret 
 obtained. Stimulation of the cerebral branch alone yields a clear, thin, watei 
 secretion, containing a very small amount of organic substances, but a conside 
 able amount of the salts of the saliva {Heidenhain). 
 
 Reflex Secretion of Saliva. — [If a cannula be placed in Wharton's due 
 e. g., in a dog, during fasting, no saliva will flow out. If the mucous membrai 
 of the mouth be stimulated by a sapid substance placed on the tongue, there is 
 copious flow of saliva. If the sympathetic nerve be divided, secretion still talo 
 place when the mouth is stimulated, but if the chorda tympani be cut, secretic 
 no longer takes place. Hence, the secretion is due to a reflex act ; in this cas 
 the lingual is the afferent, and the chorda the efferent nerve carrying impulses fro 
 a centre situated in the medulla oblongata (Fig. 152).] In the intact body, tl 
 secretion of saliva occurs through a reflex stimulation of the nerves concernei 
 whereby, under normal circumstances, the secretion is always watery (chorda < 
 facial saliva). The centripetal or afferent nerve fibres concerned are — (: 
 The nerves of taste. (2) The sensory branches of the trigeminus of the enti: 
 
THEORY OF SALIVARY SECRETION. 241 
 
 y of the mouth and the glosso-pharyngeal (which appear to be capable of 
 j stimulated by mechanical stimuli, pressure, tension, displacement). The 
 iments of mastication also cause a secretion of saliva. Pfluger found that one- 
 more saliva was secreted on the side where mastication took place ; and CI. 
 ird observed that the secretion ceased in horses during the act of drinking. 
 The nerves of smell, excited by certain odors. (4) The gastric branches of 
 agus (Frerichs, Oehl). A rush of saliva into the mouth usually precedes the 
 f vomiting (§ 158). 
 
 The stimulation of distant sensory nerves, e.g., the central end of the sciatic — certainly 
 ;h a complicated reflex mechanism — causes a secretion of saliva ( Owsjannikow and Tschier- 
 
 Stimulation of the conjunctiva, e. g., by applying an irritating fluid to the eye of carnivorous 
 Is, causes a reflex secretion of saliva [AscAenbrandt). Perhaps the secretion of saliva which 
 imes occurs during pregnancy is caused in a similar reflex manner. 
 
 ie reflex centre for the secretion of saliva lies in the medulla oblongata, at 
 arigin of the seventh and ninth cranial nerves (Eckkard and Loeb). The 
 re for the sympathetic fibres is also placed here {Griitzner and Chlapowski) . 
 region is connected by nerve fibres with the cerebrum ; hence, the thought 
 savory morsel, sometimes, when one is hungry, causes a rapid secretion of a 
 watery fluid — [or, as we say, '* makes the mouth water "]. If the centre be 
 llated directly by a mechanical stimulus (puncture), salivation occurs, while 
 yxia has the same effect. The reflex secretion of saliva may be inhibited by 
 jlation of certain sensory nerves, e. g., by pulling out a loop of the intestine 
 vlow). Stimulation of the cortex cerebri of a dog, near the sulcus cruciatus, 
 "ten followed by secretion of saliva (Eulenberg and Landois, Bochefontaine, 
 noffand Heidenhain). Disease of the brain in man sometimes causes a secre- 
 of saliva, owing to the effects produced on the intracranial centre, 
 t long as there is no stimulation of the nerves, there is no secretion of saliva, 
 . sleep (MitscherlicK). Immediately after the section of all nerves, secretion 
 >, for a time, at least. 
 
 thological Conditions and Poisons. — Certain affections, as inflammation of the mouth, neu- 
 , ulcers of the mucous membrane, affections of the gums, due to teething or the prolonged ad- 
 tration of mercury, often produce a copious secretion of saliva (or ptyalism). Certain poisons 
 the same effect by direct stimulation of the nerves, as Calabar bean (Physostigminj, digitalin, 
 specially pilocarpin. Many poisons, especially the narcotics — above all, atropm — paralyze the: 
 ory nerves, so that there is a cessation of the secretion, and the mouth becomes dry ; while the 
 listration of muscarin in this condition causes secretion (Prevost). Pilocarpin acts on the 
 a tympani, causing a profuse secretion, and, if atropin be given, the secretion is again arrested. 
 ;rsely, if the secretion be arrested by atropin, it may be restored by the action of pilocarpin or 
 istigmin. Nicotin, in small doses, excites the secretory nerves, but in large doses paralyzes 
 (Heidenhain). Daturin, cicutin, and iodide of aethystrychnine, paralyze the chorda, 
 ialogogues are those drugs which increase the secretion of saliva. Some are topical, and 
 iffect when applied to the mouth. They excite secretion reflexly by ' acting on the sensory 
 s of the mouth. They include acids, and various pungent bodies, such as mustard, ginger, 
 lrum, tobacco, ether, and chloroform; but they do not all produce the same effect on the 
 nt or quality of the saliva ; others, the general sialogogues, cause salivation when introduced 
 he blood, physostigmin, nicotin, pilocarpin, muscarin. The drugs named act after all the 
 s going to the gland are divided, so that they stimulate the peripheral ends of the nerves in 
 ands. The two former also excite the central ends of the secretory nerves.] 
 xcretion by the Saliva. — Some drugs are excreted by the saliva. Iodide of potassium is 
 y eliminated by the kidneys, and also by the salivary glands, and so also is iodide of iron.] 
 nti- sialics are those substances which diminish the secretion of saliva, and they may take 
 upon any part of the reflex arc, i. e., on the mouth, the afferent nerves, the nerve centre and 
 it nerves, or upon the blood stream through the glands, or on the glands themselves. Opium 
 lorphia affect the centre ; large doses of physostigmin affect the blood supply ; but atropin is 
 ost powerful of all, as it paralyzes the terminations of the secretory nerves in the glands, e. g. , 
 lorda tympani, and even the sympathetic in the cat (but not in the dog) (Brunton).'\ 
 eory of Salivary Secretion.— Heidenhain has recently formulated the following theory 
 ling the secretion of saliva : " During the passive or quiescent condition of the gland, the 
 ic materials of the secretion are formed from and by the activity of the protoplasm of the 
 ory cells. A quiescent cell, which has been inactive for some time, therefore contains little 
 16 
 
242 THE PAROTID SALIVA. 
 
 protoplasm, and a large amount of these secretory substances. In an actively secreting gland, ther 
 are two processes occurring together, but independent of each other, and regulated by two differen 
 classes of nerve fibres ; secretory fibres cause the act of secretion, while trophic fibres cause chemica 
 processes within the cells, partly resulting in the formation of the soluble constituents of the secretion 
 and partly in the growth of the protoplasm. According to the number of both kinds of fibres presen 
 in a nerve passing to a gland, such nerve being stimulated, the secretion takes place more rapidl' 
 (cerebral nerve) or more slowly (sympathetic), while the secretion contains less or more solid con 
 stituents. The cerebral nerves contain many secretory fibres and few trophic fibres, while thi 
 sympathetic contains more trophic, but few secretory fibres. The rapidity and chemical compositioi 
 of the secretion vary according to the strength of the stimulus. During continued secretion, th< 
 supply of secretory materials in the gland cells is used up more rapidly than it is replaced by th< 
 activity of the protoplasm; hence, the amount of organic constituents diminishes, and the microscopii 
 characters of the cells are altered. The microscopic characters of the cells are altered also by th< 
 increase of the protoplasm, which takes place in an active gland. The mucous cells disappear, anc 
 seem to be dissolved after prolonged secretion, and their place is taken by other cells derived froir 
 the proliferation of the marginal cells. The energy which causes the current of fluid depends upor 
 the protoplasm of the gland cells." 
 
 The saliva is diminished in amount in man in cases of paralysis of the facial or sympathetic 
 nerves, as is observed in unilateral paralysis of these nerves. 
 
 146. THE SALIVA OF THE INDIVIDUAL GLANDS— (a) The 
 Parotid Saliva is obtained by placing a fine cannula in Steno's duct (Eckkartf) \ 
 it has an alkaline reaction, but during fasting, the first few drops may be neutral 
 or even acid on account of free C0 2 (Oehl) — its specific gravity is 1003 to 1004. 
 When allowed to stand it becomes turbid, and deposits, in addition to albuminous 
 matter, calcium carbonate, which is present in the fresh saliva in the form ol 
 bicarbonate. 
 
 Salivary calculi are formed in the ducts of the salivary glands owing to the deposition of lime 
 salts, and they contain only traces of the other salivary constituents : in the same way is formed the 
 tartar of the teeth, which contains many threads of leptothrix, and the remains of low organisms 
 which live in decomposing saliva in carious cavities between the teeth. 
 
 It contains small quantities (more abundant in the horse) of a globulin-like 
 body, and never seems to be without C N K S sulphocyanide of potassium (or 
 sodium — Treviranus, 1814), which, however, is absent in the sheep and dog 
 (Brettel). 
 
 The sulphocyanide gives a dark red color (ferric sulphocyanide) with ferric chloride. It also 
 reduces iodic acid when added to saliva, causing a yellow color from the liberation of iodine, which 
 may be detected at once by starch {Solera). 
 
 Among the organic substances the most important are ptyalin, and a small 
 amount of urea {Gobley), and traces of a volatile acid (Caproic?). 
 
 Mucin is absent, hence the parotid saliva is fluid, is not sticky, and can 
 readily be poured from one vessel into another. It contains 1.5 to 1.6 per cent, of 
 solids in man {Mitscherlich, van Setten), of which 0.3 to 1.0 per cent, is inorganic. 
 
 Of the inorganic constituents — the most abundant are potassium and sodium chlorides ; then 
 potassium; sodium, and calcium carbonates, some phosphates and a trace of an alkaline sulphate. 
 
 {U) The Sub-maxillary Saliva is obtained by placing a cannula in Wharton's 
 duct j it is alkaline, and may be strongly so. When allowed to stand for a long 
 ' time, fine crystals of calcium carbonate are deposited, together with an amorphous 
 albuminous body. It always contains mucin (which is precipitated by acetic 
 acid) ; hence, it is usually somewhat tenacious. Further, it contains ptyalin, but 
 in less amount than in parotid saliva; and, according to Oehl, only 0.0036 per 
 cent, of potassium sulphocyanide. 
 
 Chemical Composition. — Sub-maxillary saliva (dog) : — 
 
 Water 99'-4S P er 1000. 
 
 Organic Matter . . . 2.89 " " 
 
 t • M tl . cc \ 4-5° NaCI and CaCl,. 
 
 Inorganic Matter . . . 5.00 >■£,-. rr\ r< 1 2 j w • 11. 
 
 & J j 1. 10 LaCOj, Calcium and Magnesium phosphates. 
 
THE MIXED SALIVA IN THE MOUTH. 243 
 
 Mixed Saliva Parotid Sub-maxillary 
 
 (Human) (Human) (Dog) 
 
 (Jacubtrwitsch). {Hjppe-Seyler). {Herter). 
 
 :r 99-5 1 99-3 2 9944 
 
 0.48 0.68 0.59 
 
 e organic bodies (Ptyalin) ... . 0.13 1 / 0.066 
 
 ;lium, mucin 0.16 J " s * \0.17 
 
 mic salts 0.182 0.34 0.43 
 
 iic sulphocyanide 0.006 0.03 . . . 
 
 ic and sodic chlorides 0.084 ... • • ■ ] 
 
 ses. — Pfltiger found that 100 cubic centimetres of the saliva contained 0.6 to 64.7 C0 2 
 :ould be pumped out, and part required the addition of phosphoric acid) ; 0.8 N; or, in 100 
 is, 0.91 O ; 97.88 C0 2 , 1. 21 N. [It therefore contains much more C0 2 than venous blood.] 
 
 I The Sublingual Saliva is obtained by placing a very fine cannula in the 
 is Rivinianus (Oeki), is strongly alkaline in reaction, very sticky and cohesive, 
 rins much mucin, numerous salivary corpuscles and some potassium sulpho- 
 ide (Longei). 
 
 7. THE MIXED SALIVA IN THE MOUTH.— The fluid in the 
 :h is a mixture of the secretions from the salivary glands and the secretions 
 le mucous and other glands of the mouth. 
 
 ) Physical Characters. — The mixed saliva of the mouth is a somewhat 
 ;scent, tasteless, odorless, slightly glairy fluid, with a specific gravity of 1004 
 joe), and an alkaline reaction. The amount secreted in twenty-four hours 
 00 to 1500 grammes (7 to 50 oz.) ; according to Bidder and Schmidt, how- 
 , 1000 to 2000" grammes. The solid constituents = 5.8 per 1000. 
 
 mposition. — The solids are: Epithelium and mucus, 2.2; ptyalin and albumin, 1.4; salts, 
 potassium sulphocyanide, 0.04 per 1000. The ash contains, chiefly, potash, phosphoric acid 
 hlorine (HammerbacAer). 
 
 composition products of epithelium, salivary corpuscles, or the remains of food, may render 
 i temporarily, as after long fasting and after much speaking [Hoppe-Seyler). Even outside 
 ody, saliva containing much epithelium becomes acid before it putrefies (Gorup-Besanez). 
 reaction is acid in some cases of dyspepsia and in fever, owing to the stagnation and insufn- 
 secretion. 
 
 ) Microscopic Constituents. — (a) The salivary corpuscles are slightly 
 :r than the white blood corpuscles (8 to 1 1 //), and are nucleated protoplasmic 
 ular cells without an envelope. During their living condition, the particles 
 tieir interior exhibit molecular or Brownian movements. The dark granules 
 \ in the protoplasm are thrown into a trembling movement, from the motion 
 tie fluid in which they are suspended. This dancing motion stops when the 
 dies. 
 
 he Brownian movements of these suspended granules are purely physical, and are exhibited 
 fine microscopic particles suspended in a limpid fluid, c. g., gamboge rubbed up in water, 
 
 les of carmine, charcoal, etc.] 
 Pavement epithelial cells from the mucous membrane of the mouth and tongue ; they are 
 
 abundant in catarrh of the mouth (Fig. 145). 
 
 Living organisms, which live and thrive in the cavities of teeth nourished by the remains of 
 Among these are Leptothrix buccalis (Fig. 144, 12) and small bacteria-like organisms. The 
 
 Is of the leptothrix penetrate into the canals of the dentine and produce dental caries (Liller). 
 
 , bacteria, vibrios, spirilla and spirochaetse may also be found. 
 
 ) Chemical Properties. — (0) Organic Constituents. — Serum albumin 
 recipitated by heat and by the addition of alcohol. In saliva, mixed with 
 b. water and shaken up with C0 2 , a. globulin- like body is precipitated; mucin 
 rs in small amount. Among the extractives, the most important is ptyalin 
 -zelius) ; fats and urea occur only in traces. In twenty-four hours 130 milh- 
 lmes of potassium or sodium sulphocyanide are secreted. 
 ) Inorganic Constituents. — Sodium and potassium chlorides, potassium 
 tiate, alkaline and earthy phosphates, ferric phosphate. 
 
244 PHYSIOLOGICAL ACTION OF SALIVA. 
 
 Abnormal Constituents. — In diabetes mellitus, lactic acid, derived from a further decompoi 
 tion of grape sugar, is found (Lekmann). It dissolves the lime in the teeth, giving rise to diabel 
 dental caries. Frerichs found leucin, and Vulpian increase of albumin, in albuminuria. Or foreij 
 substances taken into the body, the following appear in the saliva : Mercury, potassium, iodine ai 
 bromine. 
 
 Saliva of New-born Children. — In new-born children, the parotid aloi 
 contains ptyalin. The diastatic ferment seems to be developed in the sub-maxillai 
 gland and pancreas at the earliest after two months. Hence, it is not advisable ( 
 give starchy food to infants. No ptyalin has been found in the saliva of infan 
 suffering from thrush (Oldium albicans — Zweifel). The diastatic action of sali\ 
 is not absolutely necessary for the suckling, feeding, as it does, upon milk. Tt 
 mouth, during the first two months, is not moist, but at a later period saliva is cop 
 ously secreted (Korowin) ; after the first six months, the salivary glands increas 
 considerably. The eruption of the teeth — owing to the irritation of the mucoi 
 membrane — produces a copious secretion of saliva. 
 
 148. PHYSIOLOGICAL ACTION OF _ SALIVA. — I. Diastati 
 Action. — The most important part played by saliva in digestion is its diastati 
 or amylolytic action (Leuchs, 183 1), i. e., the transformation of starch into dextn 
 and some form of sugar. This, is due to the ptyalin — a hydrolytic ferment c 
 enzym — which acts in very minute quantity, so that starch takes up water an 
 becomes soluble, the ferment itself undergoing no essential change in the process 
 [Ptyalin belongs to the group of unorganized ferments. Like all other ferments 
 it acts only within a certain range of temperature, being most active about 40 C 
 Its energy is permanently destroyed by boiling. It acts best in a slightly alkalin 
 or neutral medium.] 
 
 Action on Starch. — [Starch grains consist of granulose or starch enclosed b 
 coats of cellulose. Cellulose does not appear to be affected by saliva, so that saliv 
 acts but slowly on raw, unboiled starch. If the starch be boiled so as to swell u 
 the starch grains and rupture the cellulose envelopes, the amylolytic action take 
 place rapidly. If starch paste or starch mucilage, made by boiling, starch i; 
 water, be acted upon by saliva, especially at the temperature of the body, the firs 
 physical change observable is the liquefaction of the paste, the mixture becomin 
 more fluid and transparent. The change takes place in a few minutes. When th 
 action is continued, important chemical changes occur.] 
 
 According to O' Sullivan, Musculus, and v. Mering, the diastatic ferment c 
 saliva (and of the pancreas) by acting upon starch or glycogen forms dextrin ani 
 maltose (both soluble in water). Several closely allied varieties of dextrin 
 distinguishable by their color reactions, seem to be produced (Briicke). Ery 
 throdextrin is formed first ; it gives a red color with iodine ; then a reducin] 
 dextrin — achroodextrin, which gives no color reaction with iodine. The suga 
 formed by the action of ptyalin upon starch is maltose (C^H^Ou + H 2 0) 
 which is distinguished from grape sugar (C 12 H 24 12 ) by containing one molecul 
 less of water, which, however, it holds as a molecule of water of hydration, a 
 indicated in the formula given above (Ad. Mayer). [Maltose also differs froti 
 grape sugar in its greater rotatory power on polarized light, and in its less powe 
 of reducing cupric oxide. Thus, it will be seen that between the original starcl 
 and the final product, maltose, several intermediate bodies are formed. Th 
 starch gives a blue with iodine, but after it has been acted on for a time it gives 
 red or violet color, indicating the color of ery throdextrin, there being a simulta 
 neous production of sugar; but ultimately no color is obtained on adding iodine- 
 achroodextrin, which gives no color with iodine, and maltose being formed. Th 
 presence of the maltose is easily determined by testing with Fehling's solution.] 
 
 [Brown and Heron suggest that the final result of the transformation may b 
 represented by the equation — 
 
 io(C 12 H 20 O 10 )+8H 2 O = 8(C 12 H 22 O 11 ) + 2(C la H 20 O 10 ) 
 
 Soluble starch. Water. Maltose. Achroodextrin.] 
 
FUNCTIONS OF THE SALIVA. 245 
 
 Tie ferment slowly changes maltose into grape sugar or dextrose. This result 
 be brought about much more rapidly by boiling maltose with dilute sulphuric 
 ydrochloric acid.] Achroodextrin ultimately passes into maltose, and this 
 a into dextrose ; the other form of dextrin does not seem to undergo this 
 ige (Seegen's Dystropodextrin). For the further changes that maltose under- 
 in the intestine, see § 183, II, 2. 
 
 he formula of starch is usually expressed as C 6 H, O 5 , but the researches already mentioned, 
 hose of Brown and Heron, make it probable that it is more complex, which we may provision- 
 epresent by « (C 12 H 20 O 10 ). According to Musculus and Meyer, erythrodextrin is a mixture 
 xtrin and soluble starch.] 
 
 eparation of Ptyalin.— (1) Like all other hydrolytic ferments, it is carried down with any 
 us precipitate that is produced in the fluid which contains it. It is easily isolated from the 
 pitate. The saliva is acidulated with phosphoric acid, and lime-water is added until the reac- 
 becomes alkaline, when a precipitate of basic calcium phosphate occurs, which carries the 
 in along with it. This precipitate is collected on a filter and washed with water, which dissolves 
 tyalin, and from its watery solution it is precipitated by alcohol as white powder. It is redis- 
 d in water and reprecipitated, and is obtained pure (Cohnheim). 
 
 Glycerine or v. Wittich's Method. — The salivary glands [rat] are chopped up, placed in 
 ute alcohol for twenty-four hours, taken out and dried, and afterward placed in glycerine for 
 al days. The glycerine extracts the ptyalin. It is precipitated by alcohol from the glycerine 
 ct. 
 
 I William Roberts recommends the following solutions for extracting ferments from organs 
 1 contain them : (1) A 3 to 4 per cent, solution of a mixture of 2 parts of boracic acid and 
 ft borax. (1) Water, with 12 to 15 per cent, of alcohol. (3) I part chloroform to 200 of 
 
 astatic Action of Saliva. — (a) The diastatic or sugar- forming action is known by — (1) The 
 pearance of the starch. When a small quantity of starch is boiled with several hundred times 
 lume of water, starch mucilage is obtained, which strikes a blue color with iodine. If to a 
 . quantity of this starch a sufficient amount of saliva be added, and the mixture kept for some 
 at the temperature of the body, the blue color disappears. (2) The presence of sugar is proved 
 tly by using the tests for sugar (§ 149). 
 
 The action takes place more slowly in the cold than at the temperature of the body — its action 
 fcebled at 55 C, and destroyed at 75 C. (Paschutin). The most favorable temperature is 
 
 39° C. 
 
 The ptyalin itself does not seem to be changed during its action, but ptyalin which has been 
 for one experiment is less active when used the second time [Paschutin). 
 palin differs from diastase in so far that the latter first begins to act at -\- 66° C. Ptyalin 
 nposes salicin into saligenin and grape sugar (Frerichs and Stddlet), but it has no action on 
 sugar and amygdalin. 
 
 1 Saliva acts best in a slightly alkaline medium, but it also acts in a neutral and even in a 
 ;ly acid fluid ; strong acidity prevents its action. The ptyalin is only active in the stomach 
 1 the acidity is due to organic acids (lactic or butyric), and not when free hydrochloric acid is 
 nt {van de Velde). In both cases, however, dextrin is formed. Ptyalin is destroyed by hydro- 
 ic acid or digestion by pepsin (Chittenden and Griswold, Langley). Even butyric and lactic 
 
 formed from grape sugar in the stomach may prevent its action ; but if the acidity be neutral- 
 the action is resumed ( CI. Bernard). 
 
 The addition of common salt, ammonium chloride, or sodium sulphate (4 per cent, solution), 
 uses the activity of the ptyalin, and so do C0 2 , acetate of quinine, strychnia, morphia, curara, 
 I per cent, sulphuric acid, 
 
 ) Much alcohol and caustic potash destroy the ptyalin ; long exposure to the air weakens its 
 1, sodium carbonate and magnesium sulphate delay the action (Pfeiffer). Salicylic acid and 
 i atropin arrest the formation of sugar. 
 
 I Ptyalin acts very feebly and very gradually upon raw starch, only after 2 to 3 hours 
 jf) ; while upon boiled starch it acts rapidly. [Hence the necessity for boiling thoroughly all 
 ly foods.] 
 
 I The various kinds of starch are changed more or less rapidly, according to the amount of 
 ose which they contain ; raw potato starch after two to three hours, raw maize starch after 2 to 
 rates (Hammarsten). Starch cellulose is dissolved at 55° C. (Nageli). When the starches are 
 ered and boiled, they are changed with equal rapidity. 
 
 A mixture of the saliva from all the glands is more active than the saliva from any single 
 
 (Jakubowitsch), while mucin is inactive. 
 
 ffect of Tea. — W. Roberts finds that tea has an intensely inhibitory effect on salivary diges- 
 which is due to the large quantity of tannin contained in the tea leaf. Coffee and cocoa have 
 a slight effect on salivary digestion. The only way to mitigate the inhibitory effect of tea on 
 ry digestion is " not to sip the beverage with the meal, tut to eat first and drink afterward."] 
 
246 TESTS FOR SUGAR. 
 
 II. Saliva dissolves those substances which are soluble in water ; while the alka 
 line reaction enables it to dissolve some substances which are not soluble in wate 
 alone, but require the presence of an alkali. 
 
 III. Saliva moistens dry food and aids the formation of the " bolus," while b; 
 its mucin it aids the act of swallowing, the mucin being given off unchanged ii 
 the faeces. The ultimate fate of ptyalin is unknown. 
 
 [IV. Saliva also aids articulation, while according to Liebig, it carries dowi 
 into the stomach small quantities of O.] 
 
 [V. It is necessary to the sense of taste, to dissolve sapid substances, and brinj 
 them in relation with the end organs of the nerves of taste.] • 
 
 The presence of a peptone-forming ferment has recently been detected in saliva [Hiifner, Munh 
 Kiihne). This ferment is likewise said to occur in the saliva of the horse, which can also conver 
 cane sugar into invert sugar, and slightly emulsionize fats [Ellenberger and v. Hofmeister). Ac 
 cording to Hofmeister, the saliva of the sheep has a digestive action on cellulose. 
 
 Saliva has no action on proteids or on fats. 
 
 [Perfectly healthy human saliva has no poisonous properties. Those observers {Pasteur, Vul 
 pian and Gautier), who obtained poisonous results by injecting human saliva into animals probabl; 
 used an unhealthy saliva.] 
 
 149. TESTS FOR SUGAR.— (1) Trommer's Test depends upon th< 
 fact that in alkaline solutions sugar acts as a reducing agent ; in this case 1 
 metallic oxide is changed into a suboxide. To the fluid to be investigated, add % 
 of its volume of a solution of caustic potash (soda), specific gravity 1.25, and 1 
 few drops of a weak solution of cupric sulphate, which causes at first a bluish pre- 
 cipitate consisting of a hydrated cupric oxide, but it is redissolved, giving a cleai 
 blue fluid, if sugar be present. Heat the upper stratum of the fluid, and a yellow 
 or red ring of cuprous oxide is obtained, which indicates the presence of sugar : 
 2CuO — O = Cu 2 0. 
 
 The solution of hydrated cupric oxide is caused by other organic substances ; but the final stage 
 or the production of cuprous oxide, is obtained only with certain sugars — grape, fruit and mill 
 (but not cane) sugar. Fluids which are turbid must be previously filtered, and if they are highlj 
 colored they must be treated with basic lead acetate ; the lead acetate is afterward removed by th( 
 addition of sodium phosphate and subsequent filtration. If very small quantities of sugar ars 
 present along with compounds of ammonia, a yellow color instead of a yellow precipitate may b< 
 obtained. In doing the test, care must be taken not to add too much cupric sulphate. 
 
 [(2) Fehling's Solution is an alkaline solution of potassio-tartarate of copper, 
 Boil a small quantity of the deep-blue colored Fehling's solution in a test tube, 
 and add to the boiling test a few drops of the fluid supposed to contain the sugar. 
 If sugar be present the copper solution is reduced, giving a yellow or reddish pre- 
 cipitate. The reason for boiling the test itself is, that the solution is apt to de- 
 compose when kept for some time, when it is precipitated by heat alone. This 
 is one of the best and most reliable tests for the presence of sugar. In Pavy's 
 modification of this test, ammonia is used instead of a caustic alkali (§ 267).] 
 
 (3) Bottger's Test. — Alkaline bismuth oxide solution is best prepared, according to Nylander 
 as follows : 2 grms. bismuth subnitrate, 4 grms. potassic and sodic tartrate, 100 grms. caustic sodi 
 of 8 per cent. Add 1 c.c. to every 10 c.c of the fluid to be investigated. When boiled for severa 
 minutes, the sugar causes the reduction and deposits a black precipitate of metallic bismuth. [Ac 
 cording to Salkowski the urine of a person taking rhubarb gives the same reaction with this test.] 
 
 (4) Moore and Heller's Test. — Caustic potash or soda is added until the mixture is stronglj 
 alkaline ; it is afterward boiled. If sugar be present, a yellow, brown, or brownish-black colora 
 tion is obtained. If nitric acid be added, the odor of burned sugar (caramel) and formic acid i: 
 obtained. 
 
 (5) Mulder and Neubauer's Test. — A solution of indigo-carmine, rendered alkaline wit! 
 sodic carbonate, is added to the sugar solution until a slight bluish color is obtained. When th< 
 mixture is heated the color passes into purple, red and yellow. When shaken with atmospheric air 
 the fluid again becomes blue. 
 
 Other tests are described in Vol. ii, \ 266. 
 
 In all cases where albumin is present it must be removed — in urine by acidulating with acetii 
 acid and boiling ; in blood, by adding four times its volume of alcohol and afterward filtering 
 while the alcohol is expelled by heat. 
 
SOLEIL-VENTZKE S POLARIZATION APPARATUS. 
 
 247 
 
 Fig. 153. 
 
 o. QUANTITATIVE ESTIMATION OF SUGAR.— I. By Fermentation.— Into 
 
 jlass vessel (Fig. 153, a) a measured quantity (20 cm.) of 
 
 luid (sugar) is placed along with some yeast, while b con- 
 
 i concentrated sulphuric acid. The whole apparatus is 
 
 ;hed. When exposed to a sufficient temperature ( 10° to 40° 
 
 the sugar splits into two molecules of alcohol and two of 
 
 on dioxide, 
 
 C 6 H, 2 O e = 2(C 2 H 6 0) + 2(C0 2 ), 
 e sugar = 2 alcohol -(- 2 carbon dioxide ; and in addi- 
 there are formed traces of glycerine and succinic acid. 
 C0 2 escapes from b, and as it passes through the H 2 S0 4 , 
 yields to the latter its water. The apparatus is weighed 
 • two days, when the reaction is ended, and the amount 
 ugar is calculated from the loss of weight in the 20 cm. 
 uid. 100 parts of water-free sugar = 48.89 parts C0 2 , or 100 parts CO a correspond to 204.54 
 5 of sugar. 
 
 Fig. 154. 
 
 Apparatus for the quantitative estimation 
 of sugar by fermentation. 
 
 Soleil-Ventzke's polarization apparatus. 
 
 I. Titration. — By means of Fehling's solution, which consists of cupric sulphate, tartrate of 
 ish and soda, caustic soda, and water. It is made of such a strength that all the copper in 10 
 ic centimetres of the solution is reduced by 0.05 gramme of grape sugar {\ 267). 
 
 II. Circumpolarization. — The saccharimeter of Soleil-Ventzke may be used to determine the 
 nunt of sugar present. It may also be used for the quantitative estimation of albumin. Sugar 
 ites the ray of polarized light to the right and albumin to the left. The amount of rotation, or 
 
248 THE MOVEMENTS OF MASTICATION. 
 
 " specific rotatory power," is directly proportional to the amount of the rotating substance present 
 in the solution, so that the amount of rotation of the rays indicates the amount of the substance 
 present. 
 
 In Fig. 154 the light from the lamp falls upon a crystal of calc-spar. Two Nicol's prisms are 
 placed at v and s; v is movable round the axis of vision, while j is fixed. In m Soleil's double 
 plate of quartz is placed ; so that one-half of it rotates the ray of polarized light as much to the 
 right as the other rotates it to the left. In n the field of vision is covered by a plate of left rotatory 
 quartz. At b c is the compensator, composed of two right rotatory prisms of quartz, which can be 
 displaced laterally by the milled head, g, so that the polarized light passing through the apparatus 
 can be made to pass through a thicker or thinner layer of quartz. When these right rotatory prisms 
 are placed in a certain position, the rotation of the left rotatory quartz at n is exactly neutralized. In 
 this position the scale on the compensator has its nonius exactly at 0, and both halves of the double 
 plate at m appear to have the same color to the observer, who from v looks through the telescope 
 placed at e. Rotate the Nicol's prism at v until a bright rose-colored field is obtained. In this 
 position the telescope must be so adjusted that the vertical line bounding the two halves shall be 
 distinctly visible. The apparatus is now ready for use. 
 
 Fill a tube, 1 decimetre in length, with urine containing sugar or albumin, the urine being per- 
 fectly clear. The tube is placed between m and n By rotating the Nicol's prisms, v, the rose- 
 color is again obtained. The compensator at^ is then rotated until both halves of the field of vision 
 have exactly the same color. When this is obtained, read off on the scale the number of degrees 
 the nonius is displaced to the right (sugar) or to the left (albumin) from zero. The number of 
 degrees indicates directly the number of grammes of the rotating susbtance present in 100 c. c. of 
 the fluid. If the fluid is very dark-colored, it must be decolorized by filtering it through animal 
 charcoal (Seegen) [or the coloring matter may be precipitated by the addition of lead acetate.] If 
 the sugary urine contains albumin, the latter must be removed by boiling and filtration. A turbidity 
 not removed by filtration may be got rid of by adding a drop of acetic acid, or several drops of 
 sodic carbonate or milk of lime, and afterward filtering. 
 
 151. MECHANISM OF THE DIGESTIVE APPARATUS.— This 
 
 embraces the following acts : — 
 
 1. The introduction of the food ; the movements of mastication and those of 
 
 the tongue ; insalivation and the formation of the bolus of food. 
 
 2. Deglutition. 
 
 3. The movements of the stomach, of the small and large intestine. 
 
 4. The excretion of fsecal matters. 
 
 152. INTRODUCTION OF THE FOOD.— Fluids are taken into the 
 mouth in three ways : (1) By suction, the lips are applied air tight to the vessel 
 containing the fluid, while the tongue is retracted (the lower jaw being often 
 depressed) and acts like the piston in a suction pump, that causes the fluid to enter 
 the mouth. Herz found that the negative pressure caused by an infant while sucking 
 = 3 to 10 mm. Hg. (2) The fluid is lapped when it is brought into direct con- 
 tact with the lips, and is raised by aspiration and mixed with air so as to produce 
 a characteristic sound in the mouth. (3) Fluid may be poured into the mouth, 
 and, as a general rule,. the lips are applied closely to the vessel containing the 
 fluid. 
 
 The solids when they consist of small particles are licked up with the lips, aided 
 by the movements of the tongue. In the case of large masses, a part is bitten off 
 with the incisor teeth, and is afterward brought under the action of the molar 
 teeth by means of the lips, cheeks, and tongue. 
 
 153. THE MOVEMENTS OF MASTICATION.— The articulation of the jaw is pro- 
 vided with an interarticular cartilage ( Vidius, Ij6y) — the meniscus — which prevents direct pressure 
 being made upon the articular surface when the jaws are energetically closed, and which also 
 divides the joint into two cavities, one lying over the other. The capsule is so lax that, in addition 
 to the raising and depressing of the lower jaw, it permits of the lower jaw being displaced for- 
 ward upon the articular tubercle, whereby the meniscus moves with it, and covers the articular 
 surface. 
 
 The process of mastication consists of the following movements : — 
 
 (a) The elevation of the jaw is accomplished by the combined action of the 
 temporal, masseter, and internal pterygoid muscles. If the lower jaw was pre- 
 
STRUCTURE AND DEVELOPMENT OF THE TEETH. 249<f> 
 
 y so far depressed that its articular surface rested upon the tubercle, it now 
 
 backward upon the articular surface. 
 
 The depression of the lower jaw is caused by its own weight, aided by 
 
 :tion of the anterior bellies of the digastrics, the mylo- and genio-hyoid 
 
 latysma (Haller). The muscles act during forcible opening of the mouth. 
 
 lecessary fixation of the hyoid bone is obtained through the action of the 
 
 nd sterno-hyoid, and by the sterno -thyroid and thyro-hyoid. 
 
 n the articular surface of the lower jaw passes forward on to the tubercle, the external 
 
 ids actively aid in producing this (Birard). 
 
 Displacement of both or one articular surface forward or back- 
 . — During rest, when the mouth is closed, the incisor teeth of the lower 
 11 within the arch of the upper incisors. When in this position the jaw is 
 ded by the external pterygoids, whereby the articular surface passes on to 
 ubercle (and, therefore, downward), while the lateral teeth are thereby 
 ted from each other. The jaw is retracted by the internal pterygoids witti- 
 ly aid from the posterior fibres of the temporals. When one articular sur- 
 i carried forward, the jaw is protruded and retracted by the external and 
 al pterygoid of the same side. At the same time, there is a transverse 
 nent, whereby the back teeth of the protruded side are separated from each 
 
 ■ing mastication, when the individual movements of the lower jaw are vari- 
 combined, the food to be masticated is kept from passing outward by the 
 i of the muscles of the lips (orbicularis oris) and the buccinators, while the 
 e continually pushes the particles between the molar teeth. The energy of 
 uscles of mastication is regulated by the sensibility of the teeth, and the 
 liar sensibility of the muscles of mastication, as well as by the general sensi- 
 of the mucous membrane of the mouth and lips. At the same time, the 
 s mixed with saliva, the divided particles cohere, and are formed into a mass 
 us of a long, oval shape, by the muscles of the tongue, ready to be swallowed. 
 
 ves of Mastication. — The muscles of mastication and the buccinator receive their motor 
 from the third branch of the trigeminus ; the mylo-hyoid and the anterior belly of the digas- 
 ng supplied from the same source. The genio-, omo-, and sterno-hyoid, sternothyroid, and 
 yoid are supplied by the hypoglossal, while the facial supplies the posterior belly of the di- 
 
 the stylo-hyoid, the platysma, and the muscles of the lips. The general centre for the 
 s of mastication lies in the medulla oblongata ($ 367). 
 
 :n the mouth is closed, the jaws are kept in contact by the pressure of the air, as the cavity 
 mouth is rendered free from air, and the entrance of air is prevented anteriorly by the lips, 
 steriorly by the soft palate. The pressure exerted by the air is from 2 to 4 mm. Hg {Metzger 
 onders). 
 
 1 process of mastication is also influenced by guiding contact sensations from the mouth.] 
 ect on the Circulation. — Marey found that mastication trebled the velocity of the blood 
 
 in the carotid (horse), while Francois Frank observed that the circulation of the brain (in 
 » increased ; hence it is evident that mastication implies an increased supply of blood to the 
 :entres.] 
 
 STRUCTURE AND DEVELOPMENT OF THE TEETH.— A tooth is just a 
 of the mucous membrane of the gum which has undergone a characteristic development, 
 simplest form, as in the teeth of the lamprey, the connective-tissue basis of the papilla is 
 1 with many layers of corneous epithelium. In human teeth, part of the papilla is trans- 
 
 into a layer of calcified dentine, while the epithelium of the papilla produces the enamel, 
 ig of the tooth being covered by a thin accessory layer of bone, the crusta petrosa or 
 it. 
 
 dentine or ivory which surrounds the pulp cavity and the canal of the fang (Fig. 155) is 
 m, elastic and brittle. The matrix of bone, dentine, when treated in a certain way, presents 
 ar structure (v. Ebner). It is permeated by innumerable long, tortuous, wavy tubes — the 
 al tubules (Leeuwenhoek, 1678) — each of which communicates with the pulp cavity by 
 of a fine opening, and passes more or less horizontally outward as far as the outer layers of 
 itine. The tubules are bounded by an extremely resistant, thin, cuticular membrane, which 
 y resists the action of chemical reagents. These tubules are filled completely by soft fibres, 
 ibres of Tomes" (1840), which are merely greatly elongated and branched processes 
 odontoblasts of the pulp ( Waldeyer, 1685), 
 
^550 
 
 STRUCTURE AND DEVELOPMENT OF THE TEETH. 
 
 Fig. 
 
 — * Enamel. 
 
 Dentine. 
 
 Pulp Cavity. 
 
 The dentinal tubules, as well as the fibres of Tomes 
 anastomose throughout their entire extent by means 
 of fine processes. As the fibres approach the enamel, 
 which they do not penetrate, some of them bend or 
 themselves, and form a loop (Fig. 158, C), while 
 others pass into the " interglobular spaces " (Fig, 
 157) which are so abundant in the outer part 01 the 
 dentine (Czermak, 1850). The interglobular spaces 
 are small spaces bounded by curved surfaces. Cer- 
 tain curved lines, " Schreger's lines " (1800), may 
 be detected with the naked eye in the dentine (e. g., 
 of the elephant's tusk) running parallel with the 
 contour of the tooth. These are caused by the 
 fact that at these parts all the chief curves in the 
 dentinal tubules follow a similar course {Retzius, 
 
 '837Y 
 
 The enamel, the hardest substance in the body 
 (resembling apatite), covers the crown of the teeth. 
 It consists of hexagonal flattened prisms (Malpighi, 
 i8£>f) arranged side by side like a palisade (Fig. 158, 
 B and C). They are 3 to 5 fi (-5^55 i ncn ) broad, 
 not quite uniform in thickness, curved slightly in dif- 
 ferent directions, and owing to inequalities of thick- 
 ness, they exhibit transverse markings. They are 
 elongated, calcified, cylindrical, epithelial cells de- 
 rived from the dental papilla. Retzius described 
 dark brown lines running parallel with the outer 
 boundary of the enamel, due to the presence of 
 pigment (Fig. 155). The fully-formed enamel is 
 negatively doubly refractive and uniaxial, while the 
 developing enamel is positively doubly refractive 
 [Hoppe- Seyler) . 
 
 The cuticula or Nasmyth's membrane (1839) 
 covers the free surface of the enamel as a completely 
 
 structureless membrane, I to 2 /jl thick, but in quite young teeth it exhibits an epithelial structure, 
 
 and is derived from the outer epithelial layer of the enamel organ. 
 
 Fig. 157. 
 
 Fig. 156. 
 
 Cement. 
 
 Longitudinal section of an incisor tooth. 
 
 Transverse section of dentine — The 
 light rings are the walls of the 
 dentinal tubules ; the dark cen- 
 tres with the light points are 
 the fibres of Tomes lying in the 
 tubules. 
 
 Interglobular spaces in dentine (ScAeni). 
 
 tvZ \ , ? ^ ? unte , r > *778) or crusta petrosa, is a thin layer of bone covering the fang 
 (*ig. 159. a). rhe bone lacunae communicate directly with the dental tubules of the fang. 
 Haversian canals and lamella: are only found where the layer of cement is thick, and the formtr 
 may communicate with the pulp cavity {Salter). Very thin layers of cement may be devoid of 
 
CHEMISTRY OF A TOOTH. 
 
 251 
 
 bone corpuscles. Sharpey's fibres occur in the cement of the dog's tooth ( Waldeyer) ; while in the 
 horse's tooth single bone corpuscles are enveloped by a capsule (Gerber). In the periodontal 
 membrane, which is just the periosteum of the alveolus, coils of blood vessels similar to the renal 
 glomeruli occur. They anastomose with each other, and are surrounded by a delicate capsule of 
 connective tissue (C. Wedl). 
 
 Fig. 158. 
 
 Section of a tooth between the dentine and enamel, a, enamel ; c, dentinal tubules ; B, enamel prisms highly 
 magnified ; C, transverse sections of enamel prisms. 
 
 , 0.75, with traces of iron, fluorine, and 
 Fig. 159. 
 
 Chemistry of a Tooth. —The teeth consist of a gelatin-yielding matrix infiltrated with calcium 
 phosphate and carbonate (like bone). (1) The dentine contains — organic matter, 27.70 ; calcium 
 phosphate and carbonate, 72.06 ; magnesium phosphate, 
 sulphuric acid (Aeby, Hoppe-Seyler). 
 
 (2) The enamel contains an organic proteid matrix 
 allied to the substance of epithelium. It contains 3.60 
 organic matter and 96.00 of calcium phosphate and car- 
 bonate, 1.05 magnesium phosphate, with traces of cal- 
 cium fluoride and an insoluble chlorine compound. 
 
 (3) The cement is identical with bone. 
 
 The Pulp in a fully grown tooth represents the re- 
 mainder of the dental papilla around which the dentine 
 was deposited. It consists of a very vascular, indis- 
 tinctly fibrillar connective tissue, laden with cells. The 
 layers of cells, resembling epithelium, which lie in direct 
 contact with the dentine, are called odontoblasts ( Wal- 
 deyer, i86j), i. e., those cells which build up the dentine. 
 The cells send off long-branched processes into the den- 
 tinal tubules, while their nucleated bodies lie on the sur- 
 face of the pulp, and form connections by processes with 
 other cells of the pulp and with neighboring odonto- 
 blasts. Numerous non-medullated nerve fibres (sensory 
 from the trigeminus) whose mode of termination is 
 unknown, occur in the pulp. 
 
 The periosteum or periodontal membrane of the fang is, at the same time, the alveolar peri- 
 osteum, and consists of delicate connective tissue, with few elastic fibres and many nerves. 
 
 The gums are devoid of mucous glands, very vascular, and often provided with long vascular 
 papillae, which are sometimes compound. 
 
 Development of a Tooth. — It begins at the end of the second month of foetal life. Along the 
 whole length of the foetal gum is a thick projecting ridge (Fig. 160, a), composed of many layers 
 of epithelium. A depression, the dental groove, also filled with epithelium, occurs in the gum, and 
 runs along under the ridge. The dental groove becomes deeper throughout its entire length, and, 
 on transverse section, presents the appearance of a dilated flask (b), while, at the same time, it is 
 filled with elongated epithelial cells, which form the " enamel organ." A conical papillae (the 
 " dentine germ " grows up from the mucous tissue, of which the gum consists, toward the enamel 
 organ (Fig. 161, c), so that the apex of the papilla comes to have the enamel organ resting upon it, 
 like a double cap. Afterward, owing to the development of connective tissue, the parts of the 
 
 Transverse section of the fang, a, cement with 
 bone corpuscles ; b, dentine with dentinal 
 tubules ; c, boundary between both. 
 
252 
 
 ERUPTION OF THE TEETH. 
 
 enamel orean lying between and uniting the individual dentine germs disappear and gradually 
 rh^eTonnectWe tUsue forms a tooth sac Inclosing the papilla and .ts enamel organ Id). 
 ^ThrSthe^ceUs (Fig. 16,, 3) of the enamel organ "^^*<^«te^«* 
 rvlindrical and become calcified to form enamel prisms. The layer ot cells oi me aouDie cap, 
 Ss directed t3d the tooth sac (i), becomes flattened, fuses undergoes a horny transforms 
 tion and becomes the cuticula, while the cells which lie between both layers undergo an mterme- 
 dkte mlmorphosis so that they come to resemble the branched stellate cells of the mucous tissue 
 
 (2 tt, d :f ffiSTifgSEt superficial layer of the projecting connective tissue of the 
 dental papUlaowng to the calcification of the continuous layer of odontoblasts which occur there 
 m*s FoTand 162 k) During the process, fibres or branches of these cells are left unaffected, 
 ind g emt n as tnffibres of Tomes. Exactly'the same process occurs as in the formation of bone, 
 thVoTntoblaU forming around themselves a calcified matrix. The cement is formed from the 
 soft connective tissue of the dental alveolus. .,,,... • 1 1 
 
 DSS^DwiDg the development of the first (temporary or milk) teeth, a special enamel 
 oreaWFg 161,,) is formed near these, but it does not undergo development until the milk teeth 
 ZTshU ; even the papilla is wanting at first. When the permanent tooth begins to develop, it 
 opens into the alveolar wall of the milk teeth from below. 
 
 The tissue of this dental sac causes erosion, or eating away of the fang and even of the body, of 
 the milk teeth, without its blood vessels undergoing atrophy. Ihe chief agents in the absorption 
 are the amoeboid cells of the granulation tissue. [Multinuclear giant cells also erode the fangs of 
 the teeth.] 
 
 Dental ridge ; b, enamel 
 organ ; c, beginning of the 
 dentine germ ; d, first indi- 
 cation of the tooth sac. 
 
 a, Dental ridge; b, enamel organ with (i) 
 outer epithelium, (2^ middle stellate 
 layer, (3) enamel prism cell layer ; d, 
 dentine germ with blood vessels and 
 the long osteoblasts on the surface ; d, 
 tooth sac : e, secondary enamel germ. 
 
 , Dental ridge ; 6, enamel organ; 
 c, dentine germ ; f, enamel ; g, 
 dentine ; h, interval between 
 enamel organ and the position 
 of the tooth ; k, layer of odon- 
 toblasts. 
 
 Eruption of the Teeth. — The following is the order in which the twenty milk teeth cut the 
 gum, i.e., from the seventh month to the second year : Lower central incisors, upper central incisors, 
 upper lateral incisors, lower lateral incisors, first molar, canine, the second molars. 
 
 [The figures indicate in months the period of eruption of each tooth.] 
 
 Molars. 
 
 Canines. 
 
 Incisors. 
 
 Canines. 
 
 Molars. 
 
 24 12 
 
 18 
 
 9 7 7 9 
 
 18 
 
 24 12 
 
 [The permanent teeth succeed the milk teeth, the process beginning about the seventh year. 
 Ten teeth in each jaw take the place of the milk teeth, while six teeth appear further back in each 
 jaw. Thus, the total number of permanent teeth is thirty-two. As the sacs from which the perma- 
 nent teeth are developed are formed before birth, they merely undergo the same process of devel- 
 opment as the temporary teeth, only at a much later period. The last of the permanent molars — 
 the wisdom tooth— -may not cut the jaw until the seventeenth to the twenty-fifth year. At the sixth 
 year the jaw contains the largest number of teeth, as all the temporary teeth are present, and. in 
 addition, the crowns of all the permanent teeth, except the wisdom tooth, making forty-eight in all.] 
 
 [Eruption of Permanent Teeth. — The age at which each tooth cuts the gum is given in years 
 in the following table : — 
 
MOVEMENTS OF THE TONGUE. 
 
 253 
 
 Molars. 
 
 Bicuspid. 
 
 Canines. 
 
 Incisors. 
 
 Canines. 
 
 Bicuspid. 
 
 Molars. 
 
 17 12 
 
 to to 6 
 
 25 '3 
 
 IO 9 
 
 II to 12 
 
 8778 
 
 II to 12 
 
 9 IO 
 
 12 17 
 6 to to 
 
 13 25 
 
 [Action of Drugs on the Teeth. — All the conditions for putrefaction are evidently present in 
 the mouth, and when putrefaction occurs, the products (often acid) attack the dentine of the teeth 
 and hasten their decay. Hence, the necessity for thorough daily cleansing of the teeth and mouth. 
 The teeth may be cleaned by means of a soft tooth brush and water, with or without the use of any 
 of the numerous dentifrices, such as powdered chalk or charcoal. Astringents, such as catechu 
 and areca nut, are sometimes used. Mineral acids, of course, attack the teeth, and ought, when 
 taken, to be sucked through a tube.] 
 
 155. MOVEMENTS OF THE TONGUE.— The tongue, being a mus- 
 cular organ (Aretaeus, a.d. 81), and extremely mobile, plays an important part 
 in the process of mastication : (1) It keeps the food from passing from between 
 the molar teeth. (2) It collects into a bolus the finely divided food after it is 
 mixed with saliva. (3) When the tongue is raised, the bolus lying on its dorsum 
 is pushed backward into the pharynx, whence it passes into the oesophagus. 
 
 The muscular fibres of the tongue run in three directions — longitudinally, from 
 base to tip ; transversely, the fibres for the most part proceeding outward from the 
 vertically placed septum linguae ; vertically, from below upward. Some of the 
 muscles are confined to the tongue (intrinsic), while others (extrinsic) are attached 
 beyond it to the hyoid bone, lower jaw, the styloid process, and the palate. 
 
 Microscopically, the fibres are transversely striated, with a delicate sarcolemma, and very often 
 they are divided where they are inserted into the mucous membrane {Leeuwenkoek). The muscu- 
 lar bundles cross each other in various directions, and in the interspaces fat cells and glands occur. 
 
 On analyzing the lingual movements, we may distinguish changes in form and 
 changes in position : — 
 
 (1) Shortening and broadening by the longitudinal muscle, aided by the hyo- 
 glossus. 
 
 (2) Elongation and narrowing, by the transversus linguae. 
 
 (3) The dorsum rendered concave by the transversus and the simultaneous action 
 of the median vertical fibres. 
 
 (4) Arching of the dorsum — (a) Transversely, by contraction of the lowest 
 transverse bundles ; (J?) longitudinally, by the action of the lowest longitudinal 
 muscles. 
 
 (5) Protrusion, by the genio-glossus, while at the same time the tongue usually 
 becomes narrower and longer (2). 
 
 (6) Retraction, by the hyo-glossus and stylo-glossus, and (1) usually occurring 
 at the same time. 
 
 (7) Depression of the tongue into the floor of the mouth, by the hyo-glossus. 
 The floor of the mouth may be made deeper by simultaneously depressing the 
 hyoid bone. 
 
 (8) Elevation of the tongue toward the gums — (a) At the tip by the anterior 
 part of the longitudinal fibres ; (0) in the middle by elevating the entire hyoid 
 bone by the mylo-hyoid (JV. trigeminus) ; {c) at the root by the stylo-glossus and 
 palato-glossus, as well as indirectly by the stylo-hyoid (iV. facialis). 
 
 (9) Lateral movements, whereby the tip of the tongue passes to the right or 
 left ; these are caused by the contraction of the longitudinal fibres of one side. 
 
 Motor Nerves. — The proper motor nerve of the tongue is the hypoglossal. When this nerve is 
 divided or paralyzed on one side, the tip of the tongue lying in the floor of the mouth is directed 
 toward the sound side, because the tonus of the non- paralyzed longitudinal fibres shortens the sound 
 side slightly. If the tongue be protruded, however, the tip passes toward ins paralyzed side. This 
 arises from the direction of the genio-glossus (from the middle downward and outward), and the 
 
254 DEGLUTITION. 
 
 tongue follows the direction of its action. The tongues of animals which have been killed exhibit 
 fibrillar contractions of the muscles, sometimes lasting for a whole day (Cardan™, 1550). 
 
 156 DEGLUTITION.— The onward movements of the contents of the 
 digestive canal are effected by a special kind of action whereby the tube or canal 
 contracts upon its contents, and as this contraction proceeds along the tube, the 
 contents are thereby carried along. This is the " peristaltic movement, or 
 
 PC In thefirst and most complicated part of the act of deglutition, we distinguish 
 in order the following individual movements : — _ 
 
 (1) The aperture of the mouth is closed by the orbicularis oris (N. facialis). 
 
 (2) The jaws are pressed against each other by the muscles of mastication (2V. 
 trigeminus), while at the same time the lower jaw affords a fixed point for the ac- 
 tion of the muscles attached to it and the hyoid bone. 
 
 (3) The tip, middle, and root of the tongue, one after the other, are pressed 
 against the hard palate, whereby the contents of the mouth are propelled toward 
 the pharynx. 
 
 (4) When the bolus has passed the anterior palatine arch (the mucus of the 
 tonsillar glands making it slippery again), it is prevented from returning to the 
 mouth by the palato-glossi muscles, which lie in the anterior pillars of the fauces, 
 coming together like two side-screens or curtains, meeting the raised dorsum of 
 the tongue (Stylo-glossus — Dzondi, 183 1). 
 
 (5) The morsel is now behind the anterior palatine arch and the root of the 
 tongue, and has reached the pharynx, where it is subjected to the successive action 
 of the three pharyngeal constrictor muscles which propel it onward. The action 
 of the superior constrictor of the pharynx is always combined with a horizontal 
 elevation (Levator veli palatini ; N. facialis), and tension (Tensor veli palatini ; 
 N. trigeminus, otic ganglion) of the soft palate {Bidder, 1838). The upper con- 
 strictor presses (through the pterygo-pharyngeus) the posterior and lateral walls of 
 the pharynx tightly against the posterior margin of the horizontal tense soft palate 
 (Passavant), whereby the margins of the posterior palatine arches (palato-pharyn- 
 geus) are approximated. The pharyngo -nasal cavity is thus completely shut off, 
 so that the bolus cannot be pressed backward into the nasal cavity. 
 
 In persons with congenital or acquired defects of the soft palate, or cleft-palate, during swallow- 
 ing food passes into the nose. 
 
 The Elevation of the Soft Palate may be demonstrated by placing a light straw along the 
 floor of the nose, so that its posterior end rests on the soft palate. 
 
 During swallowing, the end projecting from the nose descends, because of the elevation of the 
 end resting on the soft palate. 
 
 (6) Falk and Kronecker assert that, by the energetic contraction of the muscles 
 which diminish the cavity of the mouth, especially the mylo-hyoid, the bolus is 
 projected into the pharynx and oesophagus. 
 
 If we make a series of efforts to swallow, one after the other (as in drinking), 
 contraction of the pharynx and oesophagus takes place only after the last effort. 
 
 Thus, each new act of deglutition in the mouth inhibits (by stimulation of the glosso-pharyngeal 
 nerve) the movements in the parts of the oesophageal tube situated below it. 
 
 (7) The bolus is propelled onward by the successive contraction of the upper, 
 middle, and lower constrictors of the pharynx until it passes into the oesophagus. 
 At the same time the entrance to the glottis is closed, else the morsel would. pass 
 into the larynx, or, as is generally said, would "pass the wrong way." 
 
 Duration.— According to Meltzer and Kronecker, the duration of deglutition in the mouth is 
 0.3 sec; then the constrictors of the pharynx contract 0.9 sec; afterward, the upper part of the 
 oesophagus; then after 1.8 sec. the middle; and after another 3 sec. the lower constrictor. The 
 closure of the cardia, after the entrance of the bolus into the stomach, is the final act in the total 
 series of movements. 
 
 Sounds during Deglutition.— If the region of the stomach be auscultated, during the act of 
 swallowing two sounds may be heard ; the first one is produced when the bolus is projected into 
 
NERVES CONCERNED IN DEGLUTITION. 255 
 
 the stomach ; the second occurs when the peristalsis, which takes place at the end of swallowing, 
 squeezes the contents of the oesophagus through the cardia (Meltzer, Zenker, Ewald). 
 
 The closure of the glottis is effected in the following manner: {a) The 
 whole larynx — the lower jaw being fixed — is raised upward and forward, while at 
 the same time the root of the tongue hangs over it. The hyoid bone is raised 
 forward and upward by the genio-hyoid, anterior belly of the digastric and mylo- 
 hyoid ; the larynx is approximated close to the hyoid bone by the thyro-hyoid 
 (Berengar, 1521). (fi) When the larynx is raised so that it comes to lie below 
 the overhanging root of the tongue, the epiglottis is pressed downward over the 
 entrance to the glottis, and the bolus passes over it. In addition, the epiglottis 
 is pulled down by the special muscular fibres of the reflector epiglottidis and 
 aryepiglotticus {Thiele). 
 
 Injury to the Epiglottis. — Intentional injury of the epiglottis in animals, or its destruction in 
 man, may cause fluids to "go the wrong way," i. c, into the glottis, while solid food can be swal- 
 lowed without disturbance. In dogs, at any rate, colored fluids placed on the root of the tongue 
 have been observed to pass directly into the pharynx without coming into contact with it, so as to 
 tinge the upper surface of the epiglottis [Magendie, Schiff). [The basis of the epiglottis is yellow 
 elastic cartilage, so that it shows no tendency to ossify, and always retains its elasticity.] 
 
 (c) Lastly, the closure of the glottis by the constrictors of the larynx (§ 313, 
 II, 2) also prevents the entrance of substances into the larynx (Czermak). 
 
 In order that the descending bolus may be prevented from carrying the pharynx 
 with it, the stylo-pharyngeus, salpingo-pharyngeus, and baseo-pharyngeus contract 
 upward when the constrictors act. 
 
 Nerves. — Deglutition is voluntary only during the time the bolus is in 
 the mouth. When the food passes through the palatine arch into the gullet 
 the act becomes involuntary, and is, in fact, a well-regulated reflex action. 
 When there is no bolus to be swallowed, voluntary movements of deglutition can 
 be accomplished only within the mouth ; the pharynx only takes up the move- 
 ment provided a bolus (food or saliva), mechanically excites the reflex act. The 
 afferent nerves, which, when mechanically stimulated, excite the involuntary act 
 of deglutition, are, according to Schrceder van der Kolk, the palatine branches of 
 the trigeminus (from the spheno-palatine ganglion) and the pharyngeal branches 
 of the vagus ( Waller, Prevost). The centre for the nerves concerned (for the 
 striped muscles) lies in the superior olives of the medulla oblongata. Swallowing 
 can be carried out when a person is unconscious, or after destruction of the cere- 
 brum, cerebellum, and pons (§ 367, 6). [Even in the deep coma of alcoholism, 
 the tube of a stomach pump is readily carried into the stomach reflexly, provided 
 the surgeon passes it back into the pharynx, to bring it within the action of the 
 constrictors of the pharynx.] 
 
 The nerves of the pharynx are derived from the pharyngeal plexus, which 
 receives branches from the vagus, glosso-pharyngeal, and sympathetic (§ 352, 4). 
 
 Within the oesophagus, whose stratified epithelium is moistened with the mucus 
 derived from the mucous glands in its walls, the downward movement is involun- 
 tary, and depends upon a complicated reflex movement discharged from the centre 
 for deglutition. There is a peristaltic movement of the outer longitudinal and 
 inner circular non-striped muscular fibres. 
 
 In the upper part of the oesophagus, which contains striped muscular fibres, the peristalsis takes 
 place more quickly than in the lower part. The movements of the oesophagus never occur inde- 
 pendently, but are always the continuation of a foregoing act of deglutition. If food be introduced 
 into the oesophagus through a hole in its wall, there it lies; and it is only carried downward when a 
 movement to swallow is made ( Volkmann). The peristalsis extends along the whole length of the 
 oesophagus, even when it is ligatured or when a part of it is removed (Mosso). If a dog be allowed 
 to swallow a piece of flesh tied to a string, so that the flesh goes half-way down the oesophagus, and 
 if the flesh be withdrawn, the peristalsis still passes downward [C. Ludwig and Wild). 
 
 The motor nerve of the oesophagus is the vagus (not the accessory fibres) ; after it is divided, 
 the food lodges in the lower part of the oesophagus. Very large and very small masses are swal- 
 lowed with more difficulty than those of moderate size. Dogs can swallow an olive-shaped body 
 
256 
 
 MOVEMENTS OF THE STOMACH. 
 
 weighted with a counterpoise of 450 grammes (Mosso). When the thorax is greatly distended, 
 in Muller's experiment, or greatly diminished, as in Valsalva's experiment (§ 60), deglutition 
 rendered more difficult. 
 
 Goltz observed that the oesophagus and stomach (frog) became greatly more excitable, i. e., tl 
 excitability of the ganglionic plexuses in their walls was increased, when the brain and spinal coi 
 or both vagi were destroyed. These organs contracted energetically after slight stimulation, whil 
 frogs, whose central nervous system was intact, swallowed fluids simply by peristalsis. Females an 
 sometimes men also, with marked weakening of the nervous system, as in hysteria, not unfrequentl 
 have similar spasmodic contractions of the oesophageal region [globus hystericus). After section ( 
 both vagi, Schiff observed spasmodic contraction of the oesophagus. 
 
 Every time one swallows the heart's action is accelerated, the blood pressure falls, the uecessit 
 for respiration diminishes, while many movements (labor pains, erection) are inhibited. Thes 
 effects are brought about reflexly (Kronecker and Meltzer, % 369). 
 
 [Structure of the (Esophagus. — The walls of the oesophagus are composed of three coats- 
 mucous, submucous, and muscular (Fig. 163). 
 
 The mucous coat is firm and is thrown into longitudinal folds, which disappear when the tub 
 is distended. It is lined by several layers of stratified squamous epithelium. The membrane itsel 
 is composed, especially at its inner part, of dense fibrous tissue, which projects in the form of pa 
 pillse. into the stratified epithelium. At its outer part is a continuous layer of non-striped musch 
 the muscularis mucosa. 
 
 The sub-mucous coat is thicker than the foregoing, and consists of loose connective tissue, wit] 
 
 Excretory duct. 
 
 Fig. 163. 
 
 Epithelium. 
 
 Connective tissue 
 with papilla;. 
 
 Mucous gland. 
 
 Circular mus- 
 cular fibres. 
 
 Longitudinal 
 - muscular fibres. 
 
 Injected capillaries 
 
 Mucous membram 
 with muscular! 
 mucosae. 
 
 Sub-mucosa. 
 
 Transverse section of part of the oesophagus {Sckenk). 
 
 the acini of. small compound tubular mucous glands imbedded in it. The ducts pierce the muscu- 
 laris mucosae to open on the inner surface of the tube. 
 
 The muscular coat consists of an inner, thicker, circular, and an outer, thinner, longitudinal 
 layer of non-striped muscle. In man the upper third of the gullet consists of striped muscular 
 fibres. Outside the muscular coat is a layer of fibrous tissue with elastic fibres. 
 
 As in the intestine, there are two plexuses of nerves with ganglia; one in the sub-mucous coat 
 (Meissners) and the other between the two muscular coats (Auerbach's), which are continuous with 
 those in the stomach and intestine. Blood vessels and numerous lymphatics lie in the mucous and 
 sub-mucous coats.] 
 
 157. MOVEMENTS OF THE STOMACH.-Position.— When the 
 
 stomach is empty, the great curvature is directed downward and the lesser up- 
 ward ; but when the organ is full, it rotates on an axis running horizontally 
 through the pylorus and cardia, so that the great curvature appears to be directed 
 to the front and the lesser backward. 
 
 <,rrtZ^ S - e ^ Dt °l th f- Muscular Fibres.-The non-striped muscular fibres of the stomach are 
 nW.ff tw f e dlr . ect ™ s ° r l a y ers . an o«ter longitudinal continuous with those of the ceso- 
 tV fihr« f™ ! T'lfl dev 5 1 ,°P ed al °"g Ae curvatures, especially the lesser. At the pylorus 
 
 T^he cirrfnl^fihrl f '"' and , become continuous with the longitudinal fibres of the duodenum. 
 The circular fibres form a complete layer, but at the pylorus they are well marked, and constitute 
 
VOMITING. 257 
 
 the pyloric sphincter muscle, or valve ; while at the cardia (inlet), such a muscular ring is absent 
 ( Gianuzzi). The innermost oblique or diagonal layer is incomplete. 
 
 The movements of the stomach are of two kinds — (i) The rotatory 
 or churning movements, whereby the parts of the wall of the stomach lying in 
 contact with the contents or ingesta glide to and fro with a slow rubbing move- 
 ment. Such movements seem to occur periodically, every period lasting several 
 minutes (Beaumont). By these movements the contents are moistened with the 
 gastric juice, while the masses of food are partly broken down. The formation of 
 hair balls in the stomach of dogs and oxen indicates that such rotatory movements 
 of the contents of the stomach take place. (2) The other kind of movement 
 consists in a periodically occurring peristalsis, whereby, as with a push, the por- 
 tions of the contents of the stomach first dissolved are forced into the duodenum. 
 They begin after a quarter of an hour (Busch), and recur until about five hours 
 after a meal (Beaumont). This peristalsis is most pronounced toward the pyloric 
 end, and the muscles of the pyloric sphincter relax to allow the contents to pass 
 into the duodenum. According to Riidinger, the longitudinal muscular fibres, 
 when they contract, especially when the pyloric end is filled, may act so as to 
 dilate the pylorus. 
 
 Gizzard. — The strongly muscular walls of the stomach of grain-eating birds effect a trituration 
 of the food. The mechanical force thereby exerted was often experimented upon by the older 
 physiologists, who found that glass balls and lead tubes, which could be compressed only by a 
 weight of 40 kilos., were broken or compressed in the stomach of a turkey. 
 
 Influence of Nerves on the Movements. — [The stomach is supplied by 
 the vagi and by the sympathetic, the right vagus being distributed to the posterior 
 surface, and the left to the anterior surface, of the organ.] The ganglionic plexus 
 of nerve fibres and nerve cells (AuerbacK s), which lies between the muscular 
 coats of the stomach, must be regarded as its proper motor centre, and to it motor 
 impulses are conducted by the vagi. Section of both vagi does not abolish, but it 
 diminishes the movements of the stomach. The muscular fibres of the cardia may 
 be excited to action, or their action inhibited, by fibres which run in the vagus 
 (Nn. constrictores, et dilatator cardial), (v. Openchowski). [If the vagi be divided 
 in the neck, there is a short temporary spasmodic contraction of the cardiac aper- 
 ture. On stimulating the peripheral end of the vagus with electricity, after a 
 latent period of a few seconds, the cardiac end contracts, more especially if the 
 stomach be distended, but the movements are slight if the stomach be empty. In 
 curarized dogs, the pylorus contracts with varying intensity, and irregularly 
 whether the vagi and splanchnics be intact or divided. Stimulation of the vagi 
 in the neck causes contraction of the pylorus, when the latent period may be seven 
 seconds. Stimulation of the splanchnics in the thorax arrests the spontaneous 
 pyloric contractions, the left splanchnic being more active than the right ( Oser). 
 
 Stimulation of the cceliac plexus causes movements in the stomach of ruminants 
 (Eckhard), perhaps indirectly through the effect upon the blood vessels. 
 
 Local electrical stimulation of the surface of the stomach causes circular constrictions of the. 
 organ, which disappear very gradually, while the movement is often propagated to other parts of 
 the gastric wall. When heated to 25 C, the excised empty stomach exhibits movements (Calli- 
 burces). Injury to the pedunculi cerebri, optic thalamus, medulla oblongata, and even to the cer- 
 vical part of the spinal cord, according to Schiff, causes paralysis of the vessels of certain areas of 
 the stomach, resulting in congestion and subsequent hemorrhage into the mucous membrane. [It 
 is no uncommon occurrence to find hemorrhage into the gastric mucous membrane of rabbits, aiter 
 they have been killed by a violent blow on the head.] 
 
 158, VOMITING. — Mechanism. — Vomiting is caused by contraction of 
 the walls of the stomach, whereby the pyloric sphincter is closed. It occurs most 
 easily when the stomach is distended — (dogs usually greatly distend the stomach 
 by swallowing air before they vomit) ; it readily occurs in infants, in whom the 
 cul-de-sac at the cardia is not developed. It is quite certain that in children 
 vomiting occurs through contraction of the walls of the stomach without the 
 
 !7 
 
258 VOMITING. 
 
 spasmodic action of the abdominal walls. When the vomiting is violent, t 
 abdominal muscles act energetically. [The act of vomiting is generally precedi 
 by a feeling of nausea, and usually there is a rush of saliva into the mouth, causi 
 by a reflex stimulation of afferent fibres in the gastric branches of the vagus, t] 
 efferent nerve being the chorda tympani. After this a deep inspiration is take 
 and the glottis closed, so that the diaphragm is firmly pressed downward again 
 the abdominal contents, and it is kept contracted ; the lower ribs are pulled i: 
 The diaphragm being kept contracted and the glottis closed, a violent expiratoi 
 effort is made, so that the contraction of the abdominal muscles acts upon tl 
 abdominal contents the stomach being forcibly compressed. The cardiac orific 
 is opened at the same time, and the contents of the stomach are ejected. Tl 
 chief agent seems to be the abdominal compression, but the walls of the stomac 
 also help, though only to a slight extent.] 
 
 The contraction of the walls of the stomach, which causes a general diminution of the gastr 
 cavity, is not a true anti-peristalsis, as can be seen in the stomach when it is exposed ( Galen). Tl 
 cardia is opened 'by the longitudinal muscular fibres (Sckiff), which pull toward the lower orifice i 
 the oesophagus, so that when the stomach is full they must act as dilators. The act of vomiting is pn 
 ceded by a ructus-like dilating movement of the intra-thoracic part of the oesophagus,' which 
 caused thus : The glottis is closed, inspiration occurs suddenly and violently, whereby the oesophagi 
 is distended by gases proceeding from the stomach (Liittich). The larynx and hyoid bone, by th 
 combined action of the the genio-hyoid, sterno-hyoid, sterno-thyroid and thyro-hyoid muscles ai 
 forcibly pulled forward, so that the air passes from the pharynx downward into the upper sectio 
 of the oesophagus {Landois). If the abdominal walls contract suddenly, and if this sudden iir 
 pulse be aided by the movements of. the stomach itself, the contents of the stomach are force 
 outward. During continued vomiting, anti-peristalsis of the duodenum may occur, whereby bil 
 passes into the stomach, and becomes mixed with its contents. 
 
 Children, in whom the fundus is absent, vomit more easily than adults. [In them also th 
 nervous system is more excitable.] The capacity of the stomach of a new-born child is « to 4 
 cubic centimetres; after 14 days, 153 to 160 c.c; at 2 years, 740 c.c. 
 
 Magendie was of opinion that the abdominal muscles alone were concerned in vomiting as h 
 found that vomiting occurred when he replaced the stomach by a bag. This was much too crud 
 an experiment. But it only succeeds when the lowest part of the oesophagus has been remove. 
 (Fanlmi, Schiff). The view of Gianuzzi, that the abdominal muscles are the chief factoi 
 because animals poisoned with curara— in whom these muscles are paralyzed, but not the walls 
 the stomach — cannot vomit, is too wide a deduction. 
 
 Influence of Nerves.— The centre for the movements concerned in vomit 
 ing lies in the medulla oblongata, and is in relation with the respiratory centre 
 as is shown by the fact that nausea may be overcome by rapid and deep respira 
 ^X In animals, vomiting may be inhibited by vigorous artificial respiration 
 On the other hand, the administration of certain emetics prevents the occurrenct 
 of apnoea [while emetics quicken the respirations]. 
 
 The act of vomiting is most easily excited by stimulation (chemically o) 
 mechanically) of the centripetal or afferent nerves of (1) the mucous membrane 
 of the soft palate, pharynx, root of the tongue (glossopharyngeal nerve), as b 3 
 ickhng the fauces with the finger or a feather; (2) the nervls of the stomach 
 (vagus and sympathetic) ; (3) stimulation of the uterine nerves (preenancv^ • (j 
 the mesenteric nerves (inflammation of the abdomen and hernia): (o nerves a 
 the urinary apparatus (passing a renal calculus); (6) nerves to the liver and gall 
 duct (vagus) ; (7) nerves to the lungs in phthisis (vagus). Vomiting is also pro 
 duced by ^stimulation of the vomiting centre. [The efferent impu Ises P are 
 ^ftX&SZSgffi"**' """ <™*^ «* -mach), Tnd inte? 
 
 A Zz^:t^£^l:x^ te? e appears to r , becaused b ^ h — 
 
 through the brain by a disagreeable smell ICckJ\ TZ u S T^ [ ll ""V also be excited 
 special sense.] Vomiting is^very common n diseJLs ^ T * ^ T P T Si0nS ° n the nerVeS « 
 
 r Xk s s ec ai°m rV *r$^£££ p-r v ™tn g e> ,nflammation ' hemor 
 
MOVEMENTS OF THE INTESTINE. 259 
 
 ing the surface of the exposed stomach (dog) ; and many chemical emetics, eg., mustard, cupric 
 and zinc sulphate and other metallic salts, act in this way. (2) Other substances cause vomiting 
 when they are introduced into the blood (without being first introduced into the stomach), and act 
 directly upon the vomiting centre, e.g., apomorphin. [These are general emetics.] (3) Lastly, 
 there are some substances which act in both ways, e.g., tartar emetic. Emetics may also remove 
 mucus from the lungs, and in this case it is probable that the emetic acts upon the respiratory cen- 
 tre, and so favors the respirations. [According to Lauder Brunton, cupric sulphate acts even when 
 injected into the blood.] The general emetics usually create considerable depression, while the 
 vomiting lasts longer than with local emetics. The former increase the salivary, gastric, and respi- 
 ratory secretions. 
 
 [Uses of Emetics. — Emetics are useful not only for removing from the stomach any offending 
 body, be it a poison or the products of imperfect or perverted gastric digestion, or bile which has 
 passed into the stomach, but foreign bodies impacted in the oesophagus may be got rid of on exciting 
 vomiting by the subcutaneous injection of apomorphin. As the diaphragm contracts vigorously dur- 
 ing vomiting, it compresses the liver, and thus bile is expelled into the duodenum, or the passage of 
 a small calculus along the bile-duct may be aided. They also are useful in removing mucus or 
 false membranes from the respiratory passages.] 
 
 [Anti-Emetics. — Vomiting may be allayed by local anti-emetics, such as ice, and many chemical 
 substances, such as bismuth, hydrocyanic acid, opium, and morphia, as well as by general remedies 
 which act on the vomiting centre. Some of the foregoing drugs perhaps act both locally and gener- 
 ally.] 
 
 Vomiting is analogous to the process of rumination in animals that chew the cud (\ 187). Some 
 persons can empty their stomach in this way. 
 
 159. MOVEMENTS OF THE INTESTINE.— Peristalsis.— The 
 
 best example of peristaltic movements is afforded by the small intestine ; the pro- 
 gressive narrowing of the tube proceeds from above downward, thus propelling 
 the contents before it. Freque'ntly after death, or when air acts freely upon the 
 gut, we may observe that the peristalsis develops at various parts of the intestine 
 simultaneously, whereby the loops of intestine present the appearance of a heap 
 of worms creeping among each other. The advance of new intestinal contents 
 again increases the movement. In the large intestine, the movements are more 
 sluggish and less extensive. The peristaltic movements may be seen and felt when 
 the abdominal walls are very thin, and also in hernial sacks. They are more lively \\ 
 in vegetable feeders than in carnivora. The peristalsis is perhaps conducted directly 
 through the muscular substance itself (as in the heart and ureter — Engelmann). 
 
 [Rate of Motion. — In a Thiry-Vella fistula ($ 183, II) Fubini estimated the rate of motion of a 
 smooth sphere of sealing wax. It took 55 sec. to travel 1 ctm. [| in.] ; an induction current greatly 
 increases the motion, 1 elm. in 10 seconds; NaCl does not affect it, but excites secretion; laudanum 
 paralyzes it.] 
 
 Method of Observation. — Open the abdomen of an animal under a .6 per cent, saline solution, 
 to prevent the exposure of the gut to air (Sanders and Braam-Houckgeest). 
 
 The ileo-colic valve (Bauhin's valve, 1579, known to Rondelet in 1554), as a 
 rule, prevents the contents of the large intestine from passing backward into the 
 small intestine. The movements of the stomach and intestine cease during sleep 
 {Busch). 
 
 However, when fluid is slowly introduced into the rectum through a tube, it may pass upward 
 into the intestine, and even go through the ileo-colic valve into the small intestine. 
 
 Muscarin excites very lively peristalsis of the intestines, which may be set aside by atropin 
 (Schmiedeberg and Koppe). 
 
 Pathological. — When any condition excites an acute inflammation of the intestinal mucous 
 membrane, catarrh is rapidly produced, and very strong contractions of the inflamed parts filled 
 with food take place. When these parts of the gut become empty, the movements are not stronger 
 than normal. If new material passes into the inflamed part, the peristalsis recurs, becomes more 
 lively than normal, and the result is diarrhoea (Nothnagel). Sometimes, a greatly contracted 
 part of the small intestine is pushed into the piece of gut directly continuous with it, giving 
 rise to invagination or intussusception. 
 
 Anti-peristalsis, i. e., a movement which sets in and travels in an upward direction toward the 1 
 stomach, does not occur normally. That such a condition takes place has been inferred from the 
 fact that, in cases where the intestine is occluded, called ileus, faecal matter is vomited. The most ' 
 recent experiments of Nothnagel throw doubt upon this view, as he failed to observe anti-peristalsis 
 in cases where the intestine was occluded artificially. The faecal odor of the ejecta may result from 
 the prolonged retention of the material within the small intestine. 
 
 '( 
 
260 
 
 EXCRETION OF FAECAL MATTER. 
 
 xfio EXCRETION OF FAECAL MATTER.— The contents of the 
 sman inS^e rLaL in itXuf See hours, and about twelve hours in the large 
 nTe^ni w^ry become less watery. The contents assume ^ character, o 
 feces, and become " formed " in the ower part of the grea t mt^ine. Jtae feces 
 are gradually carried along by the P^^.^J^S.SK 
 a little above that, part of the rectum which is grounded by both s^inctej to 
 internal sphincter consisting of non-striped, and the external ^ofstr pedmu c e. 
 
 Immediately after the feces have been expelled, the external spmncter ^rig. 
 l64 T and Fig i6 S ) usually contracts vigorously, and remains in this condition 
 for some tmie. g Afterward it relaxes, when the elasticity of the parts surrounding 
 
 Fig. 164. 
 
 The perinaeum and its muscles. 1, anus; 2, coccyx; 3, tuberosity; 4, sciatic ligament; 5, cotyloid cavity; B 
 bulbo-cavernosus muscle ; Ts, superficial transverse perineal muscle ; F, fascia of the deep transverse perinea 
 muscle; J, ischio-cavernosus muscle; M, obturator interims : S, external anal sphincter; L, levator ani; P 
 pyrifornns {Henle). 
 
 the anal opening, particularly of the two sphincters, suffices to keep the anus 
 closed. In the interval between two evacuations, there does not seem to be i 
 continued tonic contraction of the sphincters. As long as the feces lie above the 
 I rectum, they do not excite 'any conscious sensations, but the sensation of requir 
 \ing to go to stool occurs when the feces pass into the rectum. At the same time 
 the stimulation of the sensory nerves of the rectum causes a reflex excitement o 
 the sphincters. The centre for these movements (Budge's centrum ano-spinale 
 lies in the lumbar region of the spinal cord ; in the rabbit between the sixth an< 
 seventh, and in the dog at the fifth lumbar vertebra {Masius). 
 
 In animals, whose spinal cord is divided above the centre, a slight touch in the region of the ami 
 causes this orifice to contract, but after this lively reflex contraction, the sphincters relax again, an 
 
DEFECATION. 
 
 261 
 
 the anus may remain open for a time. This occurs, because the voluntary impulses which proceed 
 from the brain to cause the contraction of the external sphincter are absent. Landois observed that 
 in dogs with the posterior roots of their lower lumbar and sacral nerves divided the anus remained 
 open, and not unfrequently a mass of faeces remained half ejected. As the sensibility of the rectum 
 and anus was abolished in these animals, the sphincters could not contract reflexly, nor could there 
 be any voluntary contraction of the sphincters, the result of sensory impulses from the rectum. 
 
 The external sphincter can be contracted voluntarily from the cerebrum, like 
 any voluntary muscle, but the closure of the anus can only be effected up to a 
 certain degree. When the pressure from above is very great, the energetic peri- 
 stalsis at last overcomes the strongest voluntary impulses. Stimulation of the 
 peduncles of the cerebrum and of the spinal cord below this point causes contrac- 
 tion of the external sphincter. 
 
 Defecation. — The evacuation of the faeces, which in man usually occurs at 
 
 Fig. 165. 
 
 Levator ani and sphincter ani externus. 
 
 certain times, begins with a lively peristalsis of the large intestine, which passes 
 downward to the rectum. In order that the mass of faeces may not excite reflexly" 
 the sphincter muscles, in consequence of mechanical stimulation of the sensory 
 nerves of the rectum, there seems to be a centre which inhibits the reflex action 
 of the sphincters, which is called into play owing, as it appears, to voluntary im- 
 pulses. Its seat is in the brain ; Masius thinks it is in the optic thalami, from 
 whence fibres pass through the peduncles of the cerebrum to the lumbar part of 
 the spinal cord. When this inhibitory apparatus is in action, the fecal mass passes 
 through the anus, without causing it to close reflexly. 
 
 The strong peristalsis which precedes defecation can be aided, and to a certain 
 degree, excited by voluntary short movements of the external sphincter and 
 
262 INFLUENCE OF NERVES ON THE INTESTINE. 
 
 levator ani, whereby the plexus myentericus of the large intestine is stimulated 
 mechanically, thus causing lively peristaltic movements in the large intestine. 
 The expulsion of the feces is also aided by the pressure of the abdominal muscles, 
 and most efficiently when a deep inspiration is taken, so as to fix the diaphragm, 
 whereby the abdominal cavity is diminished to the greatest extent. The soft parts 
 of the floor of the pelvis during a strong effort at stool, are driven downward in 
 the form of a cone, causing the mucous membrane of the anus, which contains 
 much venous blood, to be everted. The function of the levator am (Figs 164, 
 165), is, to raise voluntarily the soft parts of the floor of the pelvis, and to pull 
 the anus to a certain extent upward over the descending fecal mass. At the same 
 time, it prevents the distention of the pelvic fascia. As the fibres of both leva- 
 tores converge below and become united with the fibres of the external sphincter, 
 they aid the latter, during energetic contraction of the sphincter ; or, as Hyrtl 
 puts it, the levatores are related to the anus, like the two cords of a tobacco pouch. 
 During the periods between the evacuation of the gut, the feces appear only to 
 reach the lower end of the sigmoid flexure. As a rule, from thence downward, 
 the rectum is normally devoid of feces. It seems that the strong circular fibres 
 of the muscular coat, which Nelaton has called sphincter ani tertius, when they 
 are well developed, contract and prevent the entrance of the feces. When the 
 tendency to the evacuation of the rectum is very pressing, the anus may be closed 
 more firmly from without, by energetically rotating the thigh outward, and con- 
 tracting the muscles of the gluteal region. 
 
 161. INFLUENCE OF NERVES AND OTHER CONDITIONS 
 ON THE INTESTINAL MOVEMENTS.— Auerbach's Plexus — 
 
 The intestinal canal contains an automatic motor centre within its walls — the. plexus 
 myentericus of Auerbach — which lies between the longitudinal and circular mus- 
 cular fibres of the gut. It is this plexus which enables the intestine when cut out 
 of the body to execute, apparently spontaneously, movements for some time. 
 
 [Structure. — The plexus of Auerbach consists of non-medullated nerve fibres which form a 
 dense network, groups of ganglion cells occurring at the nodes (Fig. 166}. A similar plexus 
 extends throughout the whole intestine between the longitudinal and circular muscular coats from 
 the oesophagus to the rectum. Branches are given off to the muscular bundles. A similar, but not 
 
 Iso rich a plexus lies in the submucous coat, Meissner's plexus, which gives branches to supply the 
 muscularis mucosae, the smooth muscular fibres of the villi, and the glands of the intestine (Fig. 
 167,1.] 
 
 1. If this centre is not affected by any stimulus, the movements of the intestine 
 cease — comparable to the condition of the medulla oblongata in apncea {Sig. Mayer 
 and v. Basch). The same is true — just as in the case of the respiration — during 
 intra-uterine life, in consequence of the foetal blood being well supplied with O. 
 This condition may be termed aperistalsis. It also occurs during sleep, perhaps 
 on account of the greater amount of O in the blood during that state. 
 
 2. When blood containing the normal amount of blood gases passes through 
 the intestinal blood vessels, the quiet peristaltic movements of health occur 
 (euperistalsis), provided no other stimulus be applied to the intestine. 
 
 3. All stimuli applied to the plexus myentericus increase the peristalsis, which 
 may become so very violent as to cause evacuation of the contents of the large 
 gut, and may even produce spasmodic contraction of the musculature of the intes- 
 tine. This condition may be termed dysperistalsis, corresponding to dyspnoea. 
 The condition of the blood flowing through the intestinal vessels'has a most impor- 
 tant effect on the peristaltic movements. 
 
 Condition of the Blood.— Dysperistalsis may be produced by (a) interrupting the circulation of 
 the blood in the intestines, no matter whether anaemia (as after compressing the aorta— Schiff) or 
 venous hyperemia be produced. The stimulating condition is the want of O, i. e , the increase of 
 C0 2 . Very slight disturbance in the intestinal blood vessels, e. g , venous congestion after copious 
 transfusion into the veins, whereby the abdominal and portal veins become congested, cause increased 
 peristalsis. The intestines become nodulated at one part and narrow at another, and involuntary 
 
INFLUENCE OF. NERVES ON THE INTESTINE. 
 
 263 
 
 evacuation of the faeces takes place when there is congestion, owing to the plugging of the intes- 
 tinal blood vessels when blood from another species of animal is used for transfusion (fj 102).' The 
 marked peristalsis which occurs on the approach of death is, undoubtedly, due to the derangements 
 of the circulation, and the consequent alteration of the amount of gases in the blood of the intes- 
 tine. The same is true of the increased movements of the intestines which occur as a result of 
 
 Fig. 166. 
 
 Plexus of Auerbach, prepared from the small intestine of a dog, by the action of gold chloride. The nerve cells are 
 shown at the nodes, while the fibrils proceding from the ganglia, and the anastomosing fibres, lie between the 
 muscular bundles. 
 
 Fig. 167. 
 
 Plexus of Meissner. a, ganglia; i, anastomosing fibres ; c, artery; d, vasomotor nerve fibres accompanying c. 
 
 psychical excitement, e. g., grief. The stimulus, in this case, passes from the cerebrum, through- 
 the medulla oblongata (vasomotor centre) to the intestinal nerves, and causes anaemia of the intes- 
 tine (corresponding to the pallor occurring elsewhere). When the normal condition of the circula- 
 tion is restored, the peristalsis diminishes. (6) Direct stimulation of the intestine, conducted to the 
 plexus myentericus, causes dysperistalsis ; direct exposure of the intestines to the air (stronger when 
 
264 IFFLUENCE OF NERVES ON THE INTESTINE. 
 
 C0 2 or CI is present), introduction of various irritating substances into the intestine, increased filling 
 of the intestine when there is any difficulty in emptying the gut (often in man), direct stimulation 
 of various kinds (also inflammation), all act upon the intestine, either from without or from within. 
 Induction shocks applied to a loop of intestine in a hernial sack cause lively peristalsis in the hernia. 
 The intestinal movements are favored by heat. ' 
 
 4. The continued application of strong stimuli causes the dysperistalsis to give 
 place to rest, owing to over-stimulation, which may be called " intestinal pa- 
 resis," or exhaustion. 
 
 This condition is absolutely different from the passive condition of the intestine in aperistalsis. 
 Continued congestion of the intestinal blood vessels ultimately causes intestinal paralysis, e.g., when 
 transfusion of foreign blood causes coagulation within these vessels (Landois). Filling the blood 
 vessels with " indifferent " fluids, after the peristalsis has been previously brought about by com- 
 pressing the aorta, also causes cessation of the movements (0. Nasse). The movements cease when 
 the intestines are cooled to 19° C. {Horwath), while severe inflammation of the intestine has a 
 similar effect. Under favorable circumstances, the intestine may recover from this condition. 
 Arterial blood admitted into the vessels of the exhausted intestine causes peristalsis, which at first • 
 is more vigorous than normal. 
 
 5. The continued application of strong stimuli causes complete paralysis of 
 the intestine, such as occurs after violent peritonitis, or inflammation of the mus- 
 culature or mucous coat in man. In this condition the intestine is greatly dis- 
 tended, as the paralyzed musculature does not offer sufficient resistance to the 
 intestinal gases which are expanded by the heat. This constitutes the condition 
 of meteorism. 
 
 Influence of Nerves. — With regard to the nerves of the intestine, stimula- 
 tion of the vagus increases the movements (of the small intestine), either by 
 conducting impressions to the plexus myentericus, or by causing contraction of 
 the stomach, which stimulates the intestine in a purely mechanical manner {Braam- 
 Houckgeesf). The splanchnic is (1) the inhibitory nerve of the small intestine 
 (Pfluger), but only as long as the circulation in the intestinal blood vessels is 
 undisturbed, and the blood in the capillaries does not become venous (Sigm. 
 Mayer and von Basch) ; when the latter condition occurs, stimulation of the 
 splanchnic increases the peristalsis. If arterial blood be freely supplied, the in- 
 hibitory action continues for some time {O. Nasse). Stimulation of the origin of 
 the splanchnics of the spinal cord in the dorsal region (under the same conditions), 
 and even when general tetanus has been produced by the administration of 
 strychnia, causes an inhibitory effect. O. Nasse concludes, from these experi- 
 ments, that the splanchnic contains — (2) inhibitory fibres, which are easily ex- 
 hausted by a venous condition of the blood, and also motor fibres, which remain 
 excitable for a longer time, because after death stimulation of the splanchnics 
 always causes peristalsis, just like stimulation of the vagus. (3) The splanchnic 
 is also the vasomotor nerve of all the intestinal blood vessels, so that it governs 
 the largest vascular area in the body. When it is stimulated, all the vessels of 
 the intestine which contain muscular fibres in their walls contract ; when it is 
 divided, they dilate. In the latter case, a large amount of blood accumulates 
 within the blood vessels of the abdomen, so that there is anaemia of the other 
 parts of the body, which may be so great as to cause death— owing to the defi- 
 cient supply of blood to the medulla oblongata. (4) The splanchnic is the sensory 
 nerve of the intestine, and as such, under certain circumstances, it may give rise 
 to extremely painful sensations. 
 
 As stimulation of the splanchnic contracts the blood vessels, von Basch has raised the question 
 •whether the intestine does not come to rest, owing to the want of the blood, which acts as a stim- 
 .v w f T a stimulus is applied to the splanchnic, the intestine ceases to move before 
 
 the blood vessels contract {vanBraam-Honckgeest); it would, therefore, seem that the stimulation 
 diminishes the excitability of the plexus myentericus 
 
 According to Engelmann and v. Brakel, the peristaltic movement is chiefly propagated by direct 
 muscular conduction, as in the heart and ureter, without the intervention of any nerfe fibres. 
 
EFFECT OF DRUGS ON THE INTESTINE. 265 
 
 [Effect of Nerves on the Rectum. — The nervi erigentes, when stimulated, cause the longi- 
 tudinal muscular fibres of the rectum to contract, while the circular muscular fibres are supplied by 
 the hypogastric nerves. Stimulation of the latter nerves also exerts an inhibitory effect on the lon- 
 gitudinal muscles. Stimulation of the erigentes inhibits not only the spontaneous movements of 
 the circular fibres of the rectum, but also those movements excited by stimulation of the hypogastric 
 nerves (Fellner.)] 
 
 [Artificial Circulation in the Intestine. — Ludwig and Salvioli, after exciting a loop of intes- 
 tine from an animal, tied a cannula into an artery and another into a vein. The arterial 
 cannula was connected with a vessel containing defibrinated blood, to which different drugs could 
 be added. A lever rested on the intestine, and registered its movements on a recording surface. 
 The intestine was kept in a warm chamber. As long as arterial blood was transfused, the intestine 
 was nearly quiescent, but when it was arrested, so that the blood became venous, a series of con- 
 tractions occurred. Nicotin diminished the flow of blood and quickened the intestinal movements, 
 while at the same time the circular muscular fibres remained contracted or tetanic. Tincture of 
 opium, in the proportion of .01 to .04 in the blood, causes at first contraction of the vessels and 
 lessens the amount of blood circulating in the intestine ; but it very rapidly increases — even to six 
 times — the amount of blood which transfuses, while at the same time the movements of the intes- 
 tine cease, the walls of the intestine being contracted.] 
 
 Effect of Drugs. — Among the reagents which act upon the intestinal movements, are: (i)( 
 Such as diminish the excitability of the plexus myentericus, i.e., which lessen or even abolish kites -i 
 tinal peristalsis, e.g., belladonna. (2) Such as stimulate the inhibitory fibres of the splanchnic, and | 
 in large doses paralyze them — opium, morphia {Nothnagel) ; 1 and 2 produce constipation. (3) 
 Other agents excite the motor apparatus — nicotin (even causing spasm of the intestine), muscarin, 
 caffein and many laxatives, which act as purgatives. The movements produced by muscarin are 
 abolished by atropin (Schmiedeberg and Kbppe). These substances accelerate the evacuation of the 
 intestine, and, owing to the rapid movement of the intestinal contents, only a small amount of water 
 is absorbed; so that the evacuations are frequently fluid. (4) Among purgatives, colocynth and 
 croton oil act as direct irritants. With regard to drugs of this sort, they seem to cause a watery | 
 transudation into the intestine (C. Schmidt, Moreau), just as croton oil causes vesicles when applied 
 to the skin. (5) Calomel is said to limit the absorptive activity of the intestinal wall, and to con-\ 
 trol the decompositions in the intestine. The stools are thin and greenish^ from the admixture-of \ 
 biliverdin. (6) Certain saline purgatives — sodium sulphate, magnesium sulphate, causes fluid | ( 
 evacuations by retaining the water in the intestine (Buchheim) ; and it is said that if they be 
 injected into the blood vessels of animals, they cause constipation (Aubert). 
 
 [Nothnagel finds that when a crystal of a potash salt is applied to the peritoneal surface of the 1 
 intestine of an animal whose abdomen is opened, it causes merely a local constriction of the mus- 1 
 cular fibres of the gut, while a sodium salt on the other hand excites a contraction which passes | 
 upward toward the stomach, and never toward the rectum. Perhaps this is due to the more power-" 
 ful stimulant action of the former. In any case it may serve as a useful guide to the surgeon, in | 
 determining which is the upper end of a piece of intestine during an operation on the intestines.] 
 
 [Action of Saline Cathartics. — From an extended investigation recently made by Matthew 
 Hay on the action of saline cathartics, it would appear certain that a salt exerts a genuine excito- 
 secretory action on the glands of the intestines, while at the same time, in virtue of its low diffusi- 
 bility, it impedes absorption. Thus, between stimulated secretion and impeded absorption there is _ 
 an accumulation of fluid within the canal, which, partly from ordinary dynamical laws, partly from- 
 a gentle stimulation of the peristaltic movements excited by distention, reaches the rectum and » 
 results in purgation. Purgation does not ensue when water is withheld from the diet for one or two 
 days previous to the administration of the salt in a concentrated form. This absence of effect is . 
 due to a deficiency of water in the blood, so that the blood cannot, through the intestinal glands,, 
 yield enough fluid to the salt in order to produce purgation. When a concentrated solution of a 
 salt is administered to an animal whose alimentary, canal is known, from a few hours' preliminary 
 fasting, to be empty, but whose blood is in a natural state of dilution, the blood becomes rapidly 
 very concentrated, and reaches the maximum of its concentration in from half an hour to an hour 
 and a half; within four hours the blood has gradually returned to its normal state of concentration 
 without having reabsorbed fluid from the intestine. It apparently recoups itself from the tissue 
 fluids. After a few days' abstention from water, the tissue fluids are so much diminished as not to 
 be able any longer to recoup the blood, and the blood itself gradually becomes concentrated; hence, 
 a concentrated saline solution fails to excite any secretion when administered.] 
 
 [It is also interesting in connection with saline cathartics that the salt — sulphate of magnesia or 
 sulphate of soda — becomes split up in the small intestine, and the acid is more rapidly absorbed 
 than the base. A portion of the absorbed acid shortly afterward returns to the intestines, evidently 
 through the intestinal glands. After the maximum of excretion of the acid has been reached, the 
 salt begins very slowly and gradually to disappear by absorption, which is checked only by the 
 occurrence of purgation. The salt does not purge when injected into the blood, and excites no 
 intestinal secretion ; nor does it purge when injected subcutaneously, unless on account of its caus- 
 ing local irritation of the abdominal subcutaneous tissue, which acts reftexly on the intestines, dila- 
 ting their blood vessels, and perhaps stimulating their muscular movements.] 
 
266 FUNDUS GLANDS OF THE SiUMAtn. 
 
 162 STRUCTURE OF THE STOMACH.— [The stomach receives 
 the bolus, and secretes a juice which acts on certain constituents of the food, , 
 while by its muscular walls it moves the latter within its own cavity, and after a 
 time expels the partially digested products toward the duodenum. J 
 
 Structure— [The walls of the stomach consist of four coats, which are, from • 
 without inward — 
 
 d) The serous layer, from the peritoneum. 
 
 2) The muscular layer, composed of three layers of non-stnped muscular fibres-(o), longi- 
 tudinal ;(£), circular ; (<r), oblique (ji 15). „u„ f : m „„J 
 
 (3) The submucous layer, of loose connective tissue, with larger blood vessels, lymphatics and 
 nerves. 
 
 (4) The mucous layer.'] 
 
 The well-developed mucous membrane of the stomach is thrown into a 
 series of folds or rugae, in the contracted condition of the organ. With the aid 
 of a hand lens, it is seen to be beset with small, irregular depressions 01 pits (Fig. 
 169). Throughout its entire extent it is covered by a single layer of moderately 
 tall, narrow, cylindrical epithelium, which seems to consist of mucus-secreting 
 
 Fig. 169. 
 
 Goblet cells of the Surface section of the dog's gastric mucous mem- 
 
 stomach, brane, showing the crater-like depressions or 
 
 pits, i,i f ; a, the elevations round i,i. 
 
 goblet cells (Fig. 168). The epithelium is sharply defined at the cardia from 
 the stratified epithelium of the oesophagus, and also at the pylorus, from the true 
 cylindrical epithelium with the striated disk in the duodenum. [The cells con- 
 tain a plexus of fibrils and in the passive condition seem to consist of two zones, 
 an outer clear part, next the lumen of the organ, consisting of a substance (muci- 
 gen) which yields mucus, the attached end of the cell being granular.] The oval 
 nucleus lies about the centre of the cells. Spindle-shaped, nucleated cells, pro- 
 bably for replacing the others, are said by Ebstein to occur at their bases. All 
 the cells are open at their free ends, so that the mucus is readily discharged, leav- 
 ing the cells empty (F. E. Schultze). Numerous tubular glands of two distinct 
 kinds are placed vertically, like rows of test tubes, in the mucous membrane.. 
 
 Fundus Glands. — On making a vertical section of the cardiac portion of 
 the gastric mucous membrane, and submitting it to microscopic examination, it is 
 seen to consist of a number of tubular glands placed side by side. These are the 
 fundus glands of Heidenhain, otherwise called peptic, or cardiac. Several gland 
 tubes, which are wider below, usually open into the short duct (Fig. 172). Each 
 gland consists of a structureless membrana propria with anastomosing branched 
 
p^TOric glands of the stomach. 
 
 267 
 
 cells in relation with it. The duct is lined by a layer of cells like those lining 
 the stomach, while the secretory part of the tubes is lined throughout by a 
 layer of granular, short, small, polyhedral, or columnar nucleated cells. These 
 cells border the very narrow lumen, and were called chief or principal cells by 
 
 Fig. 170. 
 
 I, Transverse section of a duct of a fundus gland — a, membrana propria; i, mucus-secreting goblet cells ; c, adenoid 
 interstitial substance. II, Transverse section of a fundus gland — a, chief cells ; h, parietal cells; r, -adenoid 
 tissue between the gland tubes; c, divided capillaries. 
 
 Heidenhain ; they are also known as central cells (Fig. 170, II, a), or adelomor- 
 phous (d8r)A.o<s, hidden). At various places between these cells and the membrana 
 propria are large, oval or angular, well-defined, granular, densely reticulated, 
 
 nucleated cells, the parietal 'cells of Heidenhain, the delo- 
 morphous cells of Rollett, or the oxyntic (acid forming) 
 cells of Langley (Fig. 170, II, h). They are most 
 numerous in the neck of the glands, and least so in the 
 deep blind end of the tubes. These cells are stained 
 deeply by osmic acid and aniline blue, so that they are 
 readily distinguished from the other cells. They bulge 
 out the membrana propria of the gland opposite where 
 they are placed. The parietal cells in man are said to 
 reach to the lumen of the gland tubes (JSt'dhr). Isolated 
 cells are sometimes found under the epithelium of the 
 surface of the stomach {Heidenhain), and occasionally 
 in individual pyloric glands (Stohr). The fundus glands 
 are most numerous (about five millions, according to Sap- 
 pey), and are of considerable size in the fundus. 
 
 2. The Pyloric Glands occur only in the region of 
 the pylorus, where the mucous membrane is more yellow- 
 ish-white in color (Fig. 171). These glands are gen- 
 erally branched at their lower ends, so that several tubes 
 open into a single duct [which, in contradistinction to 
 the duct of the other glands, is wide and long, extending 
 often to half the depth of the mucous membrane. The 
 duct is lined by epithelium like that lining the stomach, 
 while the secretory part is lined by a single layer of 
 short, finely granular, columnar cells, whose secretion is 
 quite different from that of the cells lining the duct. The 
 lumen is well defined. Nussbaum has occasionally found 
 other cells, which stain deeply with osmic acid, between 
 the bases of these. Ebstein regards these cells as form- 
 ing pepsin. It is to be remembered that the appearance 
 
 Fig. 171. 
 
 Isolated pyloric gland. 
 
268 
 
 LYMPHATICS AND NERVES OF THE STOMAUtt. 
 
 of the cells differs according to their state of physiological activity (Figs. 173, 
 
 ilT When they are exhausted they are smaller and more granular, owing to 
 
 the denser reticulation of their network; at any rate, they are granular in 
 
 preparations hardened in alcohol (Fig. i74)-J 
 
 . . .. „_ xi,. a u n ,u are suDDorted by very delicate connective tissue mixed with 
 
 Muscularis Mu c oss -The gland are sup^orey y ^ ^ na , rf non . stri d 
 
 adenoid tissue (Fig. 170). Belo *' hl L a " e it tW fine processes of smooth muscular fibres pass up 
 muscle, the museums mucosa, and from £ ll ^^fXe of the gastric mucous membrane. 
 
 Fig. 172. 
 
 Vertical section of the gastric mucous membrane, g, g, pits on the surface ; p, neck of a fundus gland opening into 
 a duct, g ; x, parietal, and_y, chief cells; a, v, c, artery, vein, capillaries; d, d, lymphatics, emptying into a 
 large trunk, e. 
 
 membrane of the cat, there is a clear homogeneous layer, which is stained red by picrocarmine, and 
 placed immediately internal to the muscularis mucosse. It is pierced by the processes passing from 
 the muscularis mucosae.] 
 
 Masses of adenoid tissue occur in the mucous membrane, especially near the pylorus, constitut- 
 ing lymph follicles, which are comparable to the solitary glands of the small intestine. 
 
 The Lymphatics are numerous, and begin close under the epithelium by dilated extremities 
 or loops (Fig. 172, aQ ; they run vertically, and anastomose in the mucosa between the gland tubes, 
 which they envelop in sinus- like spaces. They join large trunks in the mucosa; another plexus of 
 large vessels exists in the sub-mucosa (Loven). 
 
SECRETION OF GASTRIC JUICE. 269 
 
 [The Nerves. — A plexus of non-medullated nerve fibres and a few ganglion cells exist in the 
 muscular coat [Auerbach's), and another (Meissner' s) in the sub-mucosa.] 
 
 The Blood Vessels are very numerous. Small arterial branches, a, run in the sub-mucosa and 
 ascend between the glands to form a longitudinal capillary network, c, c, which forms a narrow net- 
 work under the epithelium, and between its meshes the , gland ducts open, g. The veins gradually 
 collect from this horizontal capillary network and run toward the large veins of the sub-mucosa, v. 
 
 163. THE GASTRIC JUICE.— Properties.— The gastric juice is a 
 tolerably clear, colorless fluid, with a strong acid reaction, sour taste, and peculiar 
 characteristic odor ; it rotates the plane of polarized light to the left (Hoppe-Sey- 
 ler). It is not rendered turbid by boiling, and resists putrefaction for a long time. 
 Its specific gravity = 1002.5 (dog, 1005), and it contains only y 2 per cent, of 
 solid constituents. The quantity of gastric juice secreted in twenty-four hours 
 was estimated by Beaumont, from observations upon Alexis St. Martin, who had 
 agastric fistula (1834) — at only 180 grms. daily (J); by Griinewald (1853), in a 
 similar case, as equal to 26.4 per cent, of the body weight; while Bidder and 
 Schmidt (from corresponding observations on dogs) estimated it as equal.tp 6^ 
 kilos, daily, corresponding to -fa of the body weight. It contains : — 
 
 (1) Pepsin {Th. Schwann, 1836), the characteristic nitrogenous hydrolytic 
 ferment or enzym, which dissolves proteids. E. Schiitz obtained 0.41 to 1.17 per 
 cent, from a fasting person, by means of the oesophageal sound. 
 
 (2) Hydrochloric Acid (Prout, 1824), 0.2 to 0.3 (Hichet, 0.8 to 2.1) per 
 1000 ; (in the dog, 0.52 per cent.). This occurs free in the gastric juice, as the 
 latter always contains more free chlorine than bases, to which it can be united 
 (C. Schmidt). Lactic acid is usually met with, but it arises from the fermentation I 
 of the carbohydrates of the food. [A solution of HC1 of this strength is made 
 by adding 6.5 c.c. of the ordinary commercial acid to 1 litre of water.] 
 
 Tests. — Free hydrochloric acid is detected by the following reactions : — 0.025 P er cent, solu- 
 tion of mythyl violet becomes blue ; or, alkaline solution of co-tropaeolin becomes lilac ; or, red 
 Bordeaux wine is treated with amylic alcohol until its color almost disappears — when, if dilute 
 hydrochloric acid be added, a rose color is obtained. 
 
 Lactic Acid. — The freshly prepared blue solution of 10 c.c. of a 4 per cent, solution of carbolic 
 acid, with 20 c.c. of distilled water, and 1 drop of liquor ferri perchloride, is changed to yellow by 
 lactic acid ( Uffelmann). 
 
 (3) The large amount of mucus which covers the surface of the mucous mem- 
 brane is to be regarded as the secretion from the goblet cells of the mucous mem- 
 brane (§ 162). 
 
 (4) Mineral Salts (2 per 1000). 
 
 They are chiefly sodium and potassium chlorides, less calcic chloride (ammonium chloride, also 
 in animals), and the compounds of phosphoric acid with lime, magnesium, and iron. 
 
 Among foreign substances, which may be introduced into the body, the following appear in the 
 gastric juice — HI, after the use of potassium iodide — potassium sulphocyanide, ferric lactate, and 
 sugar, and ammonium carbonate in uraemia. 
 
 [Composition. — Gastric juice (human) mixed with some saliva (C. Schmidt) — 
 
 Water 99-44 
 
 Solids 0.56 
 
 Organic substances (pepsin and peptones) 0.32 
 
 Free hydrochloric acid 0.25 
 
 Sodic chloride 0.14 
 
 Potassic chloride 0.05 
 
 Calcic chloride 0.006 
 
 Phosphates of lime, magnesia and iron 0.015.] 
 
 164. SECRETION OF GASTRIC JUICE.— After the discovery of the 
 two kinds of glands in the stomach, and after it was found that the fundus glands 
 contained two different forms of cells, the question as to whether the different 
 constituents of gastric juice were formed by different histological elements came to 
 be investigated. 
 
270 
 
 CHANGES IN THE GLANDS DURING SECRETION. 
 
 Changes of the Cells during Digestion. — During the course of digestion the cells of the fun 
 dus (and pyloric glands, dog) undergo important changes {Heidenhain, Ebstein). During hunge 
 the chief cells are clear and large, the parietal investing cells are small, the pyloric cells clear am 
 of moderate size. During the first six hours of digestion the chief cells become enlarged am 
 moderately turbid or granular, the parietal cells also enlarge, while the pyloric cells remaii 
 unchanged. The chief cells become diminished and more turbid or granular until the ninth houi 
 the parietal cells are still swollen, and the pyloric cells enlarge. During the last hours of digestioi 
 the chief cells again become larger and clearer, the parietal cells diminish, the pyloric cells decreasi 
 in size and become turbid (Figs. 173 and 174). 
 
 [Langley gives a different description of the appearances presented by these cells during differen 
 phases of secretory activity. The results may be reconciled by remembering that the gland cell; 
 were examined under different conditions. The secretory cells consist of a cell substance composec 
 
 Fig. 173. 
 
 Fig. 174. 
 
 
 » 
 
 mm 
 
 mm' 
 
 Section of the pyloric mucous membrane 
 {Ebstein), 
 
 Pyloric glands showing changes of the 
 cells during digestion (Ebstein). 
 
 ular appearance described by Heidenha n after secretin • observat, °" "* Heidenhain, but the gran- 
 hardening agent, alcohol. Wk found Sat t \Z V ^ pn ^ My d ™ ? the aCtion of the 
 acid, in some animals at least, thf chief cells a r^r a n^ a™ S condl " on ' ? after the use of ° smic 
 two zones are differentiated, an outer one which ^ H """* **, H durin S a state of activit y 
 
 ules, and an inner more or ess granular one rJn,^ 6 ^ ° Wmg -° ?* disa PP ea ™<* of the gran- 
 granular one. Granules reappear in the outer part after rest. During 
 
FORMATION OF HYDROCHLORIC ACID. 271 
 
 digestion, the parietal cells increase in size, but do not become granular. In all cells containing 
 much pepsinogen, distinct granules are present, and the quantity of pepsinogen varies directly 
 with the number and size of the granules. In the glands of some animals there is little differ- 
 ence between the resting and active phases (Langley). Compare Serous Glands, \ 143, and Pan- 
 creas, \ 168.] 
 
 " The Pepsin is formed in the chief cells (Heidenhairi). ' When these are clear 
 and large they contain much pepsin, when they are contracted and turbid the 
 amount is small (Grutzner). The pyloric glands are also said to secrete pepsin, but 
 only to a small extent (Ebstein, Grutzner, Klemensiewicz). Pepsin accumulates 
 during the first stage of hunger, and it is eliminated during digestion and also dur- 
 ing prolonged. hunger. According to Ebstein, Grutzner, and Langley, pepsin, as 
 such, is not present within the cells, but only as a " mother substance," a pepsin- 
 ogen substance (zymogen), or propepsin (Schiff), which occurs in the gran- 
 ules of the chief cells (Langley). This zymogen or mother substance, by itself, 
 has no effect upon proteids ; but if it be treated with hydrochloric acid or sodium 
 chloride, it is changed into pepsin. Pepsin and pepsinogen may be extracted 
 from the gastric mucous membrane by means of water free from acids. 
 
 The pyloric glands secrete pepsin, but no acid. Klemensiewicz ex- 
 cised in a living dog the pyloric portion ol the stomach, and afterward stitched 
 together the duodenum and the remaining part of the 
 stomach. Fig. 175. 
 
 Pyloric Fistula.— [In Fig. 175 P represents the excised 
 pyloric portion, C the cardiac. The parts a, u, and a' a' were 
 then stitched together, and the continuity of the organ established . 
 The lower end (d) of P was closed by sutures, while the edges of 
 P at o were stitched to the abdominal walls, thus making a pyloric 
 fistula.] 
 
 The excised pyloric part, with its vessels intact, he 
 stitched to the abdominal wall, after sewing its lower 
 end. The animals experimented on died, at the latest 
 after six days. The secretion of this part was thin, Diagram of Kiemensiewicz's experi- 
 alkaline, and contained 2 per cent, of solids, includ- ment (Stirling). 
 
 ing pepsin. 
 
 In the frog the alkaline glands of the oesophagus contain only chief cells which 
 produce pepsin ; while the stomach has glands which secrete acid (and perhaps 
 some pepsin), and are lined by parietal cells (Partsch, v. Swiecicki). 
 
 Among fishes the carps have no fundus glands in the stomach (Luchau). [The secreting por- 
 tions of glands of the cardiac sack (crop) of the herring are lined by a single layer of polygonal 
 cells (W. Stirling). 
 
 The hydrochloric acid is formed, according to Heidenhain, by the parietal 
 cells. It occurs on the free surface of the gastric mucous membrane as well as in 
 the ducts of the gastric glands. The deep parts of the glands are usually alkaline. 
 Free HC1 is detected in human gastric juice, within 45 minutes to 1 to 2 hours 
 after a moderate meal (van de Velde, and others), but in 10 to 15 minutes in a 
 fasting condition after drinking water (E. Frerichs) ; the amount gradually in- 
 creases during the process of digestion (Kretschy and Uffelmanri). 
 
 CI. Bernard injected potassium ferrocyanide, and afterward lactate of iron, into the veins of a dog. 
 After death, blue coloration occurred only in the upper acid layers of the mucous membrane. Never- 
 theless, we must assume that the hydrochloric acid is secreted in the parietal cells of the fundus of 
 the glands, and that it is rapidly carried to the surface along with the pepsin. Briicke neutralized 
 the surface of the gastric mucous membrane with magnesia usta, chopped up the mucous membrane 
 with water, and left it for some time, when the fluid had again an acid reaction. 
 
 With regard to the formation of a free acid, the following statements may 
 be noted : The parietal cells form the hydrochloric acid from the chlorides which 
 the mucous membrane takes up from the blood. According to Voit, the formation 
 
272 INFLUENCE OF NERVES ON THE SECRETION. 
 
 of acid ceases if chlorides be withheld from the food. The active agent is lactic 
 acid, which splits up sodium chloride and forms free HC1 {Mafy). The base set 
 free is excreted by the urine, rendering it at the same time less acid {Jones, Mafy). 
 The formation of acid is arrested during hunger. According to H. Schulz, watery 
 solutions of alkaline and earthy chlorides are decomposed, even at a low tempera- 
 ture, by C0 2 , free hydrochloric acid being formed. 
 
 Secretion. — When the stomach is empty, there is no secretion of gastric juice ; 
 this takes place only after appropriate (mechanical, thermal, or chemical) stimu- 
 lation. In the normal condition, it takes place immediately on the introduction 
 of food, but also of indigestible substances, such as stones. The mucous mem- 
 brane becomes red, and the circulation more active, so that the venous blood 
 becomes brighter. [That the vagi are concerned in this vascular dilatation, is 
 proved by the fact, that if both nerves be divided during digestion, the gastric 
 mucous membrane becomes pale {Rutherford') .] The secretion is probably caused 
 reflexly, and the centre is perhaps in the wall of the stomach itself /Meissner's 
 plexus in the sub-mucous coat). It is asserted that the idea of food; especially \ 
 during hunger, excites secretion. As yet we do not know the effect produced upon \ 
 the secretion by stimulation or destruction of other nerves, e. g., vagtis, sympa- 
 thetic. [There is no nerve passing to the stomach, whose stimulation causes a 
 secretion of gastric juice, as the chorda tympani does in the submaxillary gland.- ) 
 If the vagi be divided sufficiently low down not to interfere with respiration, the 
 introduction of food still causes a secretion of gastric juice ; even if the sympa- 
 thetic branches be divided at the same time., secretion still goes on {Heidenhain). 7 :-}, 
 This experiment points to the existence of local secretory centres in the stomach. 
 But there is evidence to show that there is some connection, perhaps indirect, 
 between the central nervous system and the gastric glands. Richet observed a 
 case of complete occlusion of the oesophagus in a woman, produced by swallow- 
 ing a caustic alkali. A gastric fistula was made, through which the person could 
 be nourished. On placing sugar or lemon juice in the person's mouth, Richet 
 observed secretion of gastric juice. In this case no saliva could be swallowed to 
 excite secretion, so that it must have taken place through some nervous channels. 
 Even the sight or smell of food caused secretion. Emotional states also are known 
 to interfere with gastric digestion.] 
 
 Effect of Absorption. — Heidenhain isolated a part of the mucous membrane 
 of the fundus so as to form a blind sack of it, and he found that mechanical stimu- 
 lation caused merely a scanty local secretion at the spots irritated. If, however, 
 at the same time, absorption of digested matter also occurred, secretion took place 
 over larger surfaces. [He distinguishes a primary and merely local secretion 
 excited by the mechanical stimulus of the ingesta, and a secondary depending on 
 absorption and extending to the whole of the mucous membrane.] 
 
 The statement of Schifl, that active gastric juice is secreted only after absorption of the so-called 
 peptogenic substances (especially dextrin), is denied. 
 
 Action of Alcohol. — Small doses of alcohol, introduced into the stomach, increase the secretion 
 of gastric juice; large doses arrest it. Artificial digestion is affected by 10 per cent, of alcohol 
 {Schiitz), is retarded by 20 per cent, and is arrested by stronger doses. Beer and wine hinder 
 digestion, and in an undiluted form they interfere with artificial digestion {Buchner). 
 
 The gastric juice, which passes into the duodenum after gastric digestion is 
 completed, is neutralized by the alkali of the intestinal mucous membrane and the 
 pancreatic juice [at the same time, a precipitate is formed and deposited on the 
 walls of the duodenum, and it carries the pepsin down with it]. Part of the 
 pepsin is reabsorbed as such, and is found in traces in the urine and muscle juice 
 {Brilcke). 
 
 If the gastric juice be completely discharged externally through a gastric fistula, 
 the alkalinity of the intestine is so strong that the urine becomes alkaline {Mafy). 
 
 The acid gastric juice of the new-born child is already fairly active ; casein is most easily di- 
 gested by it, then fibrin and the other proteids (Zweifel). When the amount of acid is too great 
 
METHODS OF OBTAINING GASTRIC JUICE. 273 
 
 in the stomach of sucklings, large," firm, indigestible masses of casein are apt to be formed {Simon, 
 Biedert — see Milk, \ 230). This occurs more especially after the use of cow's milk. 
 
 [Action of Drugs on Gastric Secretion. — Dilute alkalies, if given before food; saliva; some!! 
 substances called peptogens by Schiff, such as dextrin and peptones, alcohol and ether, all excite 1 
 secretion, the last being very powerful. When the secretion is excessively acid, antacids are given, 
 some diminishing the acidity in the stomach, as the carbonates and bicarbonates of the alkalies, 
 liquor potassse and the carbonate of magnesia; while the citrates and tartrates of the alkalies, 
 becoming converted into carbonates in their passage through the organism, diminish the acidity of 
 the urine.] 
 
 165. METHODS OF OBTAINING GASTRIC JUICE.— Historical.— Spallanzani caused 
 
 starving animals to swallow small pieces of sponge enclosed in perforated lead capsules, and after 
 a time, when the sponges had become saturated with gastric juice, he removed them from the 
 stomach. To avoid the admixture of saliva, the sponges are best introduced through an opening 
 in the oesophagus (Manassein). Starving animals were forced to swallow small stones, which 
 excited the secretion of gastric juice. After a time, the animals were killed, and the juice collected. 
 
 Dr. Beaumont (1825), an American physician, was the first to obtain human gastric juice, from 
 a Canadian named Alexis St. Martin, who was injured by a gunshot wound, whereby a permanent 
 .gastric fistula'wfe established. Various substances were introduced through the external openings 
 which waspartaBy covered with a fold of skin, and the time required for their solution was noted. 
 Bassow (i%^5, clondlot (1843), and Bardeleben (1849) were thereby led to make artificial gastric 
 fistulse. 
 
 Gastric Fistula. — The anterior abdominal wall is opened by a median incision just below the 
 ensiform cartilage, the stomach is exposed, and its anterior wall opened and afterward stitched to 
 Ine margins of the abdominal walls. A strong cannula is placed in the fistula thus formed. A 
 silver cannula, about an inch wide and with a flange, is introduced into the stomach, so that the 
 flange lies in contact with the gastric mucous membrane. The inner surface of the tube of the 
 cannula is provided with a screw, into which a similar cannula is screwed, and its flange comes in 
 
 contact with the abdominal wall. When the two are placed together, they have the form of — , where 
 
 a passes into b. [When the two parts of the cannula are screwed together, the flanges keep the 
 abdominal walls and gastric walls in contact until they become united organically.] As a rule, the 
 tube is kept corked. If the ducts of the salivary glands be tied, a. perfectly uncomplicated object 
 for investigation is obtained. 
 
 According to Leube, dilute human gastric juice may be obtained by means of a siphon-like tube 
 introduced into the stomach. Water is introduced first, and after a time it is withdrawn. 
 
 Artificial Gastric Juice. — An important advance was made when Eberle (1834) prepared " arti- 
 ficial gastric juice" by extracting the pepsin from the gastric mucous membrane with dilute hydro- 
 chloric acid. A certain degree of concentration, however, is required [Schwann). Four litres of 
 a watery solution of 0.8-1 .0-1. 7 of pure hydrochloric acid per 1000 (Briicke) are sufficient to 
 extract the chopped-up mucous membrane of the pig's stomach. Half a litre is infused with the 
 stomach and renewed every six hours. The collected fluid is afterward filtered (Hoppe-Seyler). 
 The substance to be digested is placed in this fluid, and the whole is kept at the temperature of the 
 body, but it is necessary to add a little HC1 from lime to time (Schwann). The HC1 may be re- 
 placed by ten times its volume of lactic acid (Lehmann) and also by nitric acid ; while oxalic, sul- 
 phuric, phosphoric, acetic, formic, succinic, tartaric and citric acids are much less active ; butyric 
 and salicylic acids are inactive. 
 
 Von Wittich's Glycerine Method. — (a) Glycerine extracts pepsin in a very pure form. The 
 mucous membrane is rubbed up with powdered glass until it forms a pulp, mixed with glycerine, 
 and allowed to stand for eight days. The fluid is pressed through cloth, and the filtrate mixed with 
 alcohol, thus precipitating the pepsin, which is washed with alcohol, and afterward dissolved in the 
 dilute HC1, to form an artificial digestive fluid. [The addition of a few drops of the glycerine 
 extract to dilute HC1 is sufficient for experiments on artificial digestion.] 
 
 (b) Or the mucous membrane may be placed for twenty-four hours in alcohol, and afterward dried 
 and extracted for eight days with glycerine. 
 
 (c) Wm. Roberts has used other agents for extracting enzyms (g 148). 
 
 Preparation of Pure Pepsin. — Briicke pours on the pounded mucous membrane of the pig's 
 stomach a 5 per cent, solution of phosphoric acid, and afterward adds lime water until the acid 
 reaction is scarcely distinguishable. A copious precipitate, which carries the pepsin with it, is pro- 
 duced. This precipitate is collected on cloth, repeatedly washed with water, and afterward dis- 
 solved in very dilute HC1. A copious precipitation is caused in this fluid by gradually adding to it 
 a mixture of cholesterin in four parts of alcohol and one of ether. The cholesterin pulp is col- 
 lected on a filter, washed with water containing acetic acid, and afterward with pure water. The 
 cholesterin pulp is placed in ether, to dissolve the cholesterin, and the ether is then removed. The 
 small watery deposit contains the pepsin in solution. 
 
 Properties. — Pepsin so prepared is a colloid substance ; it does not react, 
 like albumin, with the following tests, viz. : it does not give the xanthroprotein 
 18 
 
274 ACTION ON PROTEIDS. 
 
 reaction (§ 248), is not precipitated by acetic acid and potassium ferrocyanide, 
 nor by tannic acid, mercuric chloride, silver nitrate or iodine. In other respects, 
 it belongs to the group of albumins. It is rendered inactive in an acid fluid by 
 heating it to 55°-6o° C. (Ad. Mayer). 
 
 166. PROCESS OF GASTRIC DIGESTION.— [In the process of gas- 
 tric digestion we have to consider — 
 
 1. The secretion of gastric juice and its action on food. 
 
 2. The absorption of the products of this digestion. 
 
 3. The movement of the stomach itself.] 
 
 Chyme.— The finely divided mixture of food and gastric juice is called chyme. 
 The gastric juice acts upon certain constituents of chyme. 
 
 I. Action on Proteids. — Pepsin and the dilute hydrochloric acid, at 
 the temperature of the body, transform proteids into a soluble form, to which 
 Lehmann (1850) gave the name of " Peptone." During this change, they are 
 first transformed into a substance which has the characters of syntonin (Mulder). 
 Syntonin is an acid albumin or albuminate; when neutralized by an alkali [e.g., 
 sodium carbonate], the albuminate is again precipitated (§ 249, III). Fibrin or 
 coagulated proteids first becomes clear and swollen up. 
 
 An intermediate product is then formed, a body which, as it were, stands mid- 
 way between albumin and peptone. This is called propeptone (Schmidt-Mul- 
 heim), and is identical with Kiihne's hemialbumose. It is soluble in water, 
 acids, salts, and alkalies. The solutions are not precipitated by boiling but by 
 acetic acid and ferrocyanide of potassium, by acetic acid and saturation with NaCl 
 or MgSCv It is precipitated by nitric acid and adheres firmly to the walls of the 
 reagent glass ; it dissolves in nitric acid with the aid of heat, giving an intense 
 yellow color, and is again precipitated in the cold (£. Salkowski). 
 
 By the continued action of the gastric juice, the propeptone passes into a true 
 soluble peptone. The unchanged albumin behaves like an anhydride with 
 respect to the peptone. The formation of peptone is . due to the taking up of a 
 ■molecule of water, under the influence of the hydrolytic ferment pepsin, and the 
 action takes place most readily at the temperature of the body. Gelatin is changed 
 into a gelatin-peptone. 
 
 According to Kiihne, the proteid molecule contains two substances preformed ; antialburrin 
 and hemi-albumin. Gastric juice at first converts them into antialbumose and hemialbumose, and 
 both ultimately into anti-peptone and hemi-peptone (§ 170, II). Only the latter is split up by trypsin 
 into leucin and tyrosin (Kiihne and Chittenden). 
 
 The greater the amount of pepsin (within certain limits) the more rapidly does 
 the solution take place. The pepsin suffers scarcely any change, and if care be 
 taken to renew the hydrochloric acid so as to keep it at a uniform amount, the 
 pepsin can dissolve new quantities of albumin. Still, it seems that some pepsin is 
 used up in the process of digestion (Griitzner). Proteids are introduced into the 
 stomach either in a solid (coagulated) or fluid condition. Casein alone of the fluid 
 forms is precipitated or coagulated, and afterward dissolved. The non-coagulated 
 proteids are transformed into syntonin, without being previously coagulated, and are 
 then changed into propeptone and directly peptonized, i.e., actually dissolved. 
 
 Heat Disappears. — When albumin is digested by pepsin at the temperature 
 of the body, a not inconsiderable amount of heat disappears, as can be proved by 
 calorimetric experiment (Maly). Hence, the temperature of the chyme in the 
 stomach falls o°.2-o°.6 C. in two to three hours (V. Vintschgau and Dietl). 
 
 Coagulated albumin may be regarded as the anhydride of the fluid form, and 
 the latter again as the anhydride of peptone. The peptones, therefore, represent 
 the highest degree of hydration of the proteids. 
 
 Hence, peptones may be formed from proteids by those reagents which usually cause hydration, 
 viz., treatment with strong acids (from fibrin, with 0.2 HC1 — v. Wittich), caustic alkalies, putrefac- 
 tive, and various other ferments and ozone (Gorup-Besanez). 
 
ARTIFICIAL DIGESTION OF THE PROTEIDS. 275 
 
 The anhydride proteid has been prepared from the hydrated form. Henniger 
 and Hofmeister, by boiling pure peptone with dehydrating substances (anhydrous 
 acetic acid at 8o° C), have succeeded in decomposing it into a body resembling 
 syntonin. 
 
 Properties of Peptones. — (i) They are completely soluble in water. (2) They 
 diffuse very easily through membranes {Funke). (3) They filter quite easily 
 through the pores of animal membranes {Acker). (4) They are not precipitated 
 by boiling, nitric acid, acetic acid and potassium ferrocyanide, acetic acid and 
 saturation with common salt. (5) They are precipitated from neutral or feebly 
 acid solutions by mercuric chloride, tannic acid, bile acids, and phosphoro-wol- 
 framic acid {Brucke'). (6) With Millon's reagent they react like proteids, and 
 give a red color, and with nitric acid give the yellow xanthoprotein reaction. (7) 
 With caustic potash or soda and a small quantity of cupric sulphate [or Fehling's 
 solution] they give a beautiful purplish-red color (Biuret reaction). (8) They 
 rotate the plane of polarized light to the left. 
 
 The biuret reaction is obtained with propeptone, as well as with a form of albumin, which is 
 formed during artificial digestion and is soluble in alcohol. It is called Alkophyr by Brucke. 
 
 [Darby's fluid meat gives all the above reaction^, and is very useful for studying the tests for 
 peptones.] 
 
 The Rapidity of Solution of fibrin is tested by placing fibrin, which is swollen up by the action 
 of 0.2 per cent. HC1, in a filter, and adding the digestive fluid, observing the rapidity with which 
 the fluid, the altered fibrin, drops from the filter, and the fibrin disappears (Griiniagen). Or 
 the fibrin may be colored with carmine, swollen up in 0.1 per cent. HC1, and placed in the 
 digestive fluid. The more rapidly the fluid is colored red, the more energetic is the digestion 
 (Griitzner). 
 
 Preparation. — Pure peptones are prepared by taking fluid which contains them and neutral- 
 izing it with barium carbonate, evaporating upon a water bath, and filtering. The barium is 
 removed from the filtrate by the careful addition of sulphuric acid, and subsequent filtration 
 (hoppe-Seyler). 
 
 Ptomaines. — Brieger extracted from gastric peptones by amylic alcohol a peptone-free poison, 
 with actions like those of curara. It belongs to the group of ptomaines, i. t., alkaloids obtained 
 from dead bodies or decomposing proteids. 
 
 Peptones are undoubtedly those modifications of albumin or proteids which, 
 after their absorption from the intestinal canal into the blood, are destined to 
 make good the proteids used up in the human organism. By giving peptones 
 (instead of albumin) as food, life cannot only be maintained, but there may even 
 be an increase of the body weight {Plbsz and Maly, Adamkiewicz). After [or 
 before] being absorbed into the blood stream, peptones are re-transformed, first 
 into propeptone, and then into serum albumin (§ 192). 
 
 Conditions Affecting Gastric Digestion. — The presence of already- formed peptones inter, 
 feres with the action of the gastric juice, in so far as the greater concentration of the fluid interferes 
 with and limits the mobility of the fluid particles (Hoppe-Seyler). Boiling concentrated acids, 
 alum and tannic acid, alkalinity of the gastric juice (e. g., by the admixture of much saliva), abolish 
 the action, also sulphurous and arsenious acids and potassic iodide (Fubini and Mori). The salts 
 of the heavy metals, which cause precipitates with pepsin, peptone and mucin, interfere with gastric 
 digestion, and so do concentrated solutions of alkaline salts, common salt, magnesium and sodium 
 sulphates. A small quantity of NaCl increases the secretion ( Griitzner) and favors the action of 
 pepsin ( Wolbcrg). Alcohol precipitates the pepsin, but by the subsequent addition of water it is 
 redissolved, so that digestion goes on as before. Any means that prevent the proteid bodies from 
 swelling up, as by binding them firmly, impede digestion. Slightly over half a pint of cold water 
 does not seem to disturb healthy digestion, but it does so in cases of disease of the stomach. 
 Copious draughts of water and violent muscular exercise disturb digestion ; while warm clothing, 
 especially over the pit of the stomach, aids it. Menstruation retards gastric digestion. 
 
 [Artificial Digestion. — The action of gastric juice on proteids may be 
 observed outside the body, and we can prove, as is shown in the following table, 
 after Rutherford, that pepsin and an acid — e.g., hydrochloric, along with water — 
 are essential to the formation of gastric peptones : — 
 
276 
 
 ACTION ON OTHER CONSTITUENTS OF FOOD. 
 
 Beaker A. 
 
 Beaker B. 
 
 Beaker C. 
 
 Water. 
 
 Pepsin, 0.3 per cent. 
 
 Fibrin. 
 
 Water. 
 
 HCl, 0.2 per cent. 
 
 Fibrin. 
 
 Water. 
 
 Pepsin, 0.3 per cent. 
 
 HCl, 0.2 
 
 Fibrin. 
 
 Keep all in water bath at 38 C. 
 
 Unchanged. 
 
 Fibrin swells up, becomes clear, 
 and is changed into acid albu- 
 min or syntonin. 
 
 Fibrin ultimately changed 
 into peptone. 
 
 The two essential substances must also be present in certain proportions and 
 the acid must be present to a certain amount, and not exceed certain limits. The 
 fibrin is obtained by beating blood, and afterward washing and boiling it, to 
 destroy any traces of pepsin. The fibrin may be colored with carmine, and from 
 the rapidity with which the fibrin is dissolved, i. e. , the depth of the color of the 
 fluid, we may estimate the digestive power of the gastric juice. Similar experi- 
 ments may be made with unboiled white of egg mixed with nine volumes of 
 water, and filtered through muslin.] 
 
 [In all animals gastric digestion is essentially an acid digestion, and between 
 the native proteid, fibrin, albumin, or any other form of proteid, and the end- 
 product peptone, there are many intermediate substances or by-products, whose 
 properties and characters have still to be investigated. If the peptones be decom- 
 posed, small quantities of leucin and tyrosin are produced. W. Roberts obtained 
 a bitter substance during gastric digestion.] 
 
 [Exclusion of the Stomach. — Ogata finds that if the stomach be divided at the pyloric end so 
 as to exclude the stomach from the digestive apparatus, a dog can be nourished for a long time by 
 introducing food through the pylorus into the duodenum. Raw flesh so introduced is digested 
 more rapidly in the small intestine than in the stomach. 'The stomach not only digests but it acts 
 on the connective tissue of flesh so as to prepare the latter for intestinal digestion.] 
 
 II. Action on other Constituents of Food. — Milk coagulates when it 
 enters the stomach, owing to the precipitation of the casein, and in doing so it 
 entangles some of the milk globules. During the process of coagulation, heat is 
 given off (Mosso, Ad. Mayer). The free hydrochloric acid of the gastric juice is 
 itself sufficient to precipitate it ; the acid removes from the alkali albuminate or 
 casein the alkali which keeps it in solution. Hammarsten separated a special 
 -ferment from the gastric juice — quite distinct from pepsin — the milk-curdling 
 ferment which, quite independently of the acid, precipitates the casein either in 
 neutral or alkaline solutions. It is this ferment or rennet which is used to 
 coagulate casein in the making of cheese. [Rennet is an infusion of the fourth 
 stomach of the calf in brine (§ 231). The ferment which coagulates milk is quite 
 distinct from pepsin. If magnesic carbonate be added to an infusion of calf s 
 stomach, a precipitate is obtained. The clear fluid has strongly coagulating prop- 
 erties, while the precipitate is strongly peptic] 
 
 The action of the milk-curdling ferment is perhaps like the action of all ferments, a hydration of 
 casein (Ad. Meyer); it is greater in the presence of 0.2 HCl (Schumburg). 
 
 One part of the rennet ferment can precipitate 800,000 parts of casein. When casein coagulates, 
 two new proteids seem to be formed — the coagulated proteid which constitutes cheese, and a body 
 resembling peptone dissolved in the whey. The addition of calcium chloride accelerated, while 
 water retarded the coagulation (Hammarsten) — see Milk, \ 231. [A ferment similar to rennet is 
 contained in the seeds of Withania coagulant (S. Lea)."] 
 
 Casein is first precipitated in the stomach, then a body like syntonin is formed, and finally peptone. 
 During the process, a substance containing phosphorus and resembling nuclein appears (Lubavin). 
 
ACTION OF GASTRIC JUICE ON THE VARIOUS TISSUES. 277 
 
 There is a " lactic acid ferment " (Hammarsteri) also present, which changes 
 milk sugar into lactic acid. Part of the milk sugar is changed in the stomach and 
 intestine into grape sugar. 
 
 Action on Carbohydrates. — Gastric juice does not act as a solvent of 
 starch, inulin, ot gums. Cane sugar is slowly changed into grape sugar (Bouch- 
 ardat and Sandras (1S4J), Lehntanri). According to Uffelmann, the gastric 
 mucus, and according to Leube, the gastric acids, are the chief agents in this 
 process. 
 
 Albuminoids. — During the digestion of true cartilage, there is formed a 
 chondrin peptone, arid a body which gives the sugar reaction with Trommer's test. 
 Perfectly pure elastin yields an elastin peptone, similar to albumin peptone, and 
 hemi-elastin similar to hemi-albnmoseX-ff oriaczewsh"). 
 
 Fats formerly were stated not to be acted on, but the recent researches of Cash 
 and Ogata show that a small part of the fats is broken up into glycerine and fatty 
 acids. [On neutral olive oil being injected into the stomach of a dog, after several 
 hours — the pylorus being plugged with an elastic bag — it partly slips up and yields 
 oleic acid (Ogata). ] 
 
 [We still require further observations on the gastric digestion of fats. Richet observed in his case 
 of fistula that fatty matters remained a long time in the stomach, and Ludwig found the same result 
 in the dog. In some dyspeptics, rancid eructations often take place toward the end of gastric 
 digestion. W. Roberts suggests that there may be some slight decomposition of neutral fats and 
 liberation of fatty acids. In this connection, it is important to remember that fatty acids are liber- 
 ated from neutral fats by bacteroid ferments (zymophytes).] 
 
 III. Action of Gastric Juice on the Various Tissues. — (1) The gelatin-yielding sub- 
 stance (collagen) of all the connective tissues (connective tissue, white fibro-cartilage, and the matrix 
 of bone), as well as glutin, are dissolved and peptonized by the gastric juice ( Uffelmanti). 
 [Gelatin when acted on by gastric juice no longer solidifies in the cold, but a gelatin peptone is 
 formed, which is soluble and diffusible, although it differs from true peptone.] In the dog, con- 
 nective tissues are specially acted on in the stomach, while the other parts of organs used as food 
 are prepared for digestion in the small intestine, where the cellular and nuclear elements are 
 digested by the pancreatic juice (Bikfalvi).~\ (2) The structureless membranes (membranse 
 propria?) of glands, sarcolemma, Schwann's sheath of nerve fibres, capsule of the lens, the elastic 
 laminae of the cornea, the membranes of fat cells are dissolved, but the true elastic (fenestrated) 
 membranes and fibres are not affected. (3) Striped muscle, after solution of the sarcolemma, 
 breaks up transversely into disks, and, like non-striped muscle, is dissolved and forms a true soluble 
 peptone, but parts of the muscle always pass into the intestine. (4) The albuminous constituents 
 of the soft cellular elements of glands, stratified epithelium, endothelium, and lymph cells, form 
 peptones, but the nuclein of the nuclei does not seem to be dissolved. (5) The horny parts of 
 the epidermis, nails, hair, as well as chitin, silk, conchiolin, and spongin of the lower animals 
 are indigestible, and so are amyloid substance and wax. (6) The red blood corpuscles are dis- 
 solved, the haemoglobin decomposed into hsematin and a globulin-like substance ; the latter is pep- 
 tonized, while the former remains unchanged, and is partly absorbed and transformed into bile pig- 
 ment. Fibrin is easily dissolved to form propeptone and fibrin peptone. (7) Mucin, which is also 
 secreted by the goblet cells of the stomach, passes through the intestines unchanged. (8) Vege- 
 table fats are not affected by the gastric juice ; these cells yield their protoplasmic contents to form' 
 peptones, while the cellulose of the cell wall, in the case of man at least, remains undigested 
 
 (8 184)- 
 
 Why the Stomach does not digest itself. — That the stomach can digest living things is 
 shown by the following facts : The limb of a living frog was introduced through a gastric fistula 
 into the stomach of a dog [CI. Bernard) — The ear of a rabbit (Pavy) was also introduced — and 
 both were partly digested. The margins of a gastric ulcer and of gastric fistulas in man are attacked 
 by the gastric juice. John Hunter (1772) discussed the question as to why the stomach does not 
 digest itself. Not unfrequently after death the posterior wall of the stomach is found digested [more 
 especially if the person die after a full meal and the body be kept in a warm place, whereby the 
 contents of the stomach may escape into the peritoneum. CI. Bernard showed, that if a rabbit be 
 killed and placed in an oven at the temperature of the body, the walls of the stomach are attacked 
 by its own gastric juice. Fishes are also frequently found with their stomach partially digested 
 after death]. It would seem, therefore, that so long as the circulation continues, the tissues are pro- 
 tected from the action of the acid by the alkaline blood; this action cannot take place if the reac- 
 tion be alkaline (Pavy). Ligature of the arteries of the stomach, according to Pavy, causes diges- 
 tive softening of the gastric mucous membrane. The thick layer of mucus may also aid in protect- 
 ing the stomach from the action of its own gastric juice ( CI. Bernard). 
 
278 
 
 STRUCTURE OF THE PANCREAS. 
 
 167. GASES IN THE STOMACH. — The stomach always contains a 
 certain quantity of gases, which are derived partly from the gases swallowed with 
 the saliva, partly from gases which pass backward from the duodenum, and partly 
 from air swallowed directly. 
 
 If the larynx and hyoid bone ({> 158) are suddenly and forcibly raised upward and forward, there 
 passes into the space behind the larynx a considerable amount of air. which on the latter regaining 
 its position, is swallowed, owing to the peristalsis of the oesophagus. We can feel the passage of such 
 a mass of air as it passes along the oesophagus. In this way a considerable volume of air may be 
 swallowed. 
 
 The air in the stomach is constantly undergoing changes, whereby its O is 
 absorbed by the blood, and for 1 vol. of O absorbed 2 vols, of C0 2 are returned 
 to the stomach from the blood. Hence, the amount of O in the stomach is very 
 small, the C0 2 very considerable {Planer). 
 
 Gases in the Stomach. — Vol. per cent. {Planer). 
 
 Human Subject after Vegetable Diet. 
 
 Dog. 
 
 I. 
 
 II. 
 
 I. 
 After Animal Diet. 
 
 II. 
 
 After Legumes. 
 
 CO z , . . . 20.79 
 H, . . . 6.71 
 N, . . . 72.50 
 
 
 33-83 
 
 27.58 
 
 38.22 
 
 °-37 
 
 25.2 
 68.7 
 
 6.1 
 
 ". 32-9 
 
 .1 
 
 66.3 
 
 0.8 
 
 I 
 
 • ;A 
 
 ■?, 
 
 Fig. 176. 
 
 M 
 
 
 mam 
 
 By the acid of the stomach a part of the C0 2 is set free from the saliva, which 
 contains much C0 2 (§ 146). The N acts as an indifferent substance. 
 
 Abnormal development of gases in persons suffering from gastric catarrh, only occurs when 
 the gastric contents are neutral 'in reaction; during the butyric acid fermentation H and C0 2 are 
 formed, while the acetic acid and lactic acid fermentations do not cause the formation of gases. 
 Marsh gas (CH 4 ) has also been found, but it must come from the intestine, as it can only be formed 
 when no O is present ($ 184). 
 
 168. STRUCTURE OF THE PANCREAS.— The pancreas is built 
 on the type of compound tubular or acino- tubular glands, and in its general 
 arrangement into lobes, lobules and system of ducts and 
 acini, it corresponds exactly to the true salivary glands. 
 The epithelium lining the ducts is not at all, or only faintly, 
 striated. The acini are tubular or flask-shaped, and often 
 convoluted. They consist of a membrana propria, resem- 
 bling that of the salivary glands, lined by a single layer of 
 somewhat cylindrical cells, with a more or less conical apex 
 directed toward the very narrow lumen of the acini. [As 
 in the salivary glands, there is a narrow intermediary 
 part of the ducts opening into the acini, and lined by flat- 
 tened epithelium.] The cells lining the acini consist of two 
 zones (Fig. 176): — 
 
 (1) The smaller parietal layer (outer) is transparent, 
 homogeneous, sometimes faintly striated, and readily stained 
 with carmine and logwood; and (2) the inner layer 
 {Bernard' 1 s granular layer) is strongly granular, and stains 
 but slightly with carmine (Fig. 176). It undoubtedly contributes to the secretion 
 by giving off material, the granules being dissolved, and this zone becoming 
 smaller (Heidenhain). The spherical nucleus lies between the two zones. [The 
 lumen of the acini is very small, and spindle-shaped or branched cells (centro- 
 acinar cells) lie in it, and send their processes between the secretory cells, thus 
 
 nan 
 
 Jft* 
 
 ■ ■ :. 
 •■•.. • < 
 
 iiiiif 
 
 
 Section of the tubes of the 
 pancreas in the fresh 
 condition. 
 
THE PANCREATIC JUICE. 279 
 
 acting as supporting cells for the elements of the wall of the acini (Langerhans, 
 Podwisotzky).~\ During secretion there is a continuous change in the appearance 
 of the cell substance ; the granules of the inner zone dissolve in the secretion ; 
 the homogeneous substance of the outer zone is reversed and transformed into 
 granules, which pass toward the inner zone {Heidenhain, Kiihne and Led). 
 
 Changes in the Cells during Digestion. — During the first stage (6 to 10 hours) the granular 
 inner zone diminishes in size, the granules disappear, while the striated outer zone increases in size 
 (Fig 177, 2). In the second stage (10 to 20 hours) the inner zone is greatly enlarged arid granular, 
 while the outer zone is small (Fig. 177, 3). During hunger the outer zone again enlarges (Fig. 
 I77> ')■ I" a gland where paralytic secretion takes place, the gland is much diminished in size, 
 the cells are shriveled (Fig. 177, 4) and greatly changed {Heidenhain). According to Ogata, 
 some cells actually disappear during secretion. 
 
 Duct. — The axially-placed excretory duct consists of an inner thick and an outer loose wall of 
 connective and elastic tissues, lined by a single layer of non-striated columnar epithelium. Small 
 mucous glands lie in the largest trunks. The connective tissue separates the gland into lobes and 
 lobules. Non-medullated nerves, with ganglia in their course, pass to the acini, but their mode of 
 termination is unknown. The Hood vessels form a. rich capillary plexus round some acini, while 
 round others there are very few. Kiihne and Lea found peculiar small cells in groups between the 
 alveoli, and supplied with convoluted capillaries like glomeruli. Their significance is entirely 
 unknown. [They are probably lymphatic in their nature.] The lymphatics resemble those of the 
 salivary glands. The pancreas contains water, proteids, ferments, fats and salts. When a colored 
 injection is forced into the ducts under a high pressure, fine intercellular passages between the 
 secreting cells are formed (SaviottVs canals), but they are artificial products. 
 
 [In making experiments upon the pancreatic secretion, it is important to remember that the num- 
 ber of pancreatic ducts varies in different animals. In man there is just one duct opening along 
 
 Fig. 177. 
 
 Changes of the pancreatic cells in various stages of activity. 1, During hunger : 2, In the first stage of digestion ; 3 
 In the second stage ; 4, During paralytic secretion. 
 
 with the common bile duct at Vater's ampulla, at the junction of the middle and lower third of the 
 duodenum. The rabbit has two ducts, the larger opening separately about 14 inches (30 to 35 cm.) 
 below the entrance of the bile duct. The dog and cat have each two ducts opening separately.] 
 
 Chemistry — The fresh pancreas contains water, proteids, the ferments, fats and salts. In a 
 gland which has been exposed for some time, leucin, isoleucin (JVencii), butalin, tyrosin, often 
 xanthin and guanin are found : lactic and fatty acids seem to be formed from chemical decomposi- 
 tions taking place. 
 
 i6g. THE PANCREATIC JUICE.— Method of obtaining the pancreatic juice. Regner 
 de Graaf (1664) tied a cannula in the pancreatic duct of a dog, and collected the juice in a small 
 bag placed in the abdomen. Other experimenters brought the lube through the abdominal wall, 
 and made a temporary fistula, which after some days became inflamed, so that the cannula fell 
 out. To make a permanent fistula, a duodenal fistula (like a gastric fistula) is made, and Wir- 
 sung's duct is catheterized with a fine tube ; or the abdomen is opened (dog), and the pancreatic 
 duct is pulled forward and stitched to the abdominal wall, with which, in certain cases, it unites. 
 Heidenhain cuts out the part of the duodenum where the duct opens into it, from its continuity with 
 the intestine, and fixes it on the outside the abdominal wound. 
 
 Variations in Secretion. — The secretion obtained from a permanent fistula 
 is a copious, slightly active, watery secretion, containing much sodium carbonate; 
 while the thick fluid obtained from the fistula before inflammation sets in acts far 
 more energetically. This thick secretion, which is small in amount, is the normal 
 secretion. The copious watery secretion is perhaps caused by the increased trans- 
 udation from the dilated blood vessels (possibly, in consequence of the paralysis 
 of the vasomotor nerves). It is, therefore, in a certain sense, a " paralytic secre- 
 tion " (§145). The quantity varies much, according as the fluid is thick or 
 
280 DIGESTIVE ACTION OF THE PANCREATIC JUICE. 
 
 thin. During digestion, a large dog secretes i to 1.5 grammes of a thick secre- 
 tion ( CI. Bernard). Bidder and Schmidt obtained in twenty-four hours 35 to 1 1 7 
 grammes of a watery secretion per kilo, of a dog. 
 
 When the gland is not secreting, and is at rest, it is soft and of a pale yellowish- 
 red color, but during secretion it is red and turgid with blood, owing to the dila- 
 tation of the blood vessels. 
 
 The normal secretion is transparent, colorless, odorless, saltish to the taste, 
 and has a strong alkaline reaction, owing to the presence of sodium carbonate, 
 so that when an acid is added, C0 2 is given off. It contains albumin and alkali 
 albuminate ; like thin white of egg, it is sticky, somewhat viscid, flows with diffi- 
 culty, and is coagulated by heat into a white mass. In the cold, there separates 
 a jelly-like albuminous coagulum. Nitric, hydrochloric and sulphuric acids cause 
 a precipitate, while the precipitate caused by alcohol is redissolved by water. CI. 
 Bernard found in the pancreatic juice of a dog 8. 2 per cent, of organic substances, 
 and o. 8 per cent, of ash. The juice (dog) analyzed by Carl Schmidt contained in 
 1000 parts : — 
 
 (Organic 81.84 
 Inorganic 8.54 
 (like those of blood 
 serum). 
 
 Sodic Chloride 7.36 
 
 " Phosphate 0.45 
 
 " Sulphate 0.10 
 
 Soda 0.32 
 
 Lime 2.22 
 
 Magnesia 0.05 
 
 Potassic Sulphate 0.02 
 
 Ferric Oxide 0.02 
 
 The more rapid and more profuse the secretion, the poorer it is in organic substances ( Weinmann, 
 Bernstein), while the inorganic remain almost the same; nevertheless, the total quantity of solids 
 is greater than when the quantity secreted is small {Bernstein). Traces of leucin (Radziejewski) 
 and soaps are contained in the fresh juice. [It usually contains few or no structural elements. Any 
 structural elements present in the fresh juice, as well as its proteids, are digested by the peptone- 
 forming ferment of the juice, especially if the juice be kept for some time. If the fresh juice is 
 allowed to stand for some time, and then mixed with chlorine water, a red color is obtained.] 
 
 Concretions are rarely formed in the pancreatic ducts ; they usually consist of calcic carbonate. 
 Dextrose has been found in the juice in diabetes, and urea in jaundice. 
 
 The statement made by Schiff, that the pancreas secretes only after the absorption of dextrin, has 
 not been confirmed. The secretory activity of the pancreas is not dependent on the presence of 
 the spleen. 
 
 170. DIGESTIVE ACTION OF THE PANCREATIC JUICE.— 
 
 The presence of at least four hydroly tic ferments or enzymes makes the pancreatic 
 juice one of the most important digestive fluids in the body. 
 
 I. The Diastatic Action ( Valentin, 1844) is caused by a diastatic ferment, 
 amylopsin, a substance which seems to be identical with the saliva ferment ; but 
 it acts much more energetically than the ptyalin of saliva, on raw starch as well 
 as upon boiled starch ; at the temperature of the body the change is effected 
 almost at once, while it takes place more slowly at a low temperature. Glycogen 
 is changed into dextrin and grape sugar, and achroodextrin (Briicke's) into sugar. 
 Even cellulose is said to be dissolved {SchmulewilscK), and gum changed into 
 sugar by it [v. Voif), but inulin remains unchanged. 
 
 According to v. Mering and Musculus, the starch (as in the case of the saliva, \ 148) is changed 
 into maltose, a reducing dextrin, and grape sugar; so, also, is glycogen. Amylopsin changes 
 achroodextrin into maltose; at 40 C. maltose is slowly changed into dextrose {Brown and Heron), 
 but cane sugar is not changed into invertin. 
 
 The ferment is precipitated by alcohol, while it is extracted by glycerine without undergoing any 
 essential change. All conditions which destroy the diastatic action of saliva (& 148) similarly affect 
 its action, but the admixture with acid gastric juice (its acid being neutralized) or bile does not seem 
 to have any injurious influence. This ferment is absent from the pancreas of new-born children 
 (Korowin). 
 
 Preparation. — The ferment is isolated by the same methods as obtain for the saliva ptyalin 
 (J 148); but the tryptic ferment is precipitated at the same time. The addition of neutral salts (4 
 per cent, solution), e.g., potassium nitrate, common salt, ammonium chloride, increases the diastatic 
 action. 
 
DIGESTIVE ACTION OF THE PANCREATIC JUICE. 
 
 281 
 
 II. The Tryptic Action {CI. Bernard, i8js)> ° r tne action on proteids, 
 depends upon the presence of a hydrolytic ferment which Corvisart (1858) called 
 pancreatin, and W. Kiihne (1876) termed trypsin. Trypsin acts upon proteids 
 at the temperature of the body, when the reaction is alkaline, and changes them 
 first into a globulin-like substance (serum globulin, § 249, J. G. Oil), then into / 
 propeptone, and, lastly, into a true peptone, sometimes called tryptone. The/ 
 proteids do not swell up before they are changed into peptone [but they are 
 eroded or eaten away by the action of the juice]. When the proteid has been 
 previously swollen up by the action of an acid, or when' the reaction of the medium 
 is acid, the transformation is interfered with. . 
 
 Substances yielding gelatin, nuclein (Bokay) and Hb resist trypsin; glutin and swollen-up gelatin- 
 yielding substances are changed into gelatin peptone, but the latter undergoes no further change. 
 O-Hb is split up into albumin and hsemochromogen. In other respects, trypsin acts on tissues con- 
 taining albumins just like pepsin ($ 167, III) {Hoppe-Seyler). 
 
 Preparation. — Trypsin is never absent from the pancreas of new-born children {Zweifel\, and it 
 may be extracted by water, which, however, also dissolves the albumin. Kiihne has carefully sepa- 
 rated the albumin and obtained the ferment in a pure stale. It is soluble in water, insoluble in 
 alcohol. Pepsin and hydrochloric acid together act upon trypsin and destroy it; hence it is not 
 advisable to administer trypsin by the mouth, as it would be destroyed in the stomach [Ewald, 
 Mays). When dried it may be heated to 160° without injury (Salkowski). 
 
 Origin of Trypsin. — It is formed within the pancreas, from a " mother sub- 
 stance" or zymogen {Heidenhain), which takes up oxygen. The zymogen is 
 found in small amount, six to ten hours after a meal, in the inner zone of the se- 
 cretory cells, but after sixteen hours it is very abundant in the inner zone of the 
 cells. It is soluble in water and glycerine. Trypsin is formed in the watery solu- 
 tion from the zymogen, and the same result occurs when the pancreas is chopped 
 up and treated with strong alcohol ( W. Kiihne'). The addition of sodium chlo- 
 ride, carbonate, and glycocholate, favors the activity of the tryptic ferment {Hei- 
 denhain). [The following facts show that zymogen (Cu/mj, ferment), or, as it has 
 been called, trypsinogen, is the precursor of trypsin, that it exists in the gland 
 cells, and requires to be acted upon before trypsin is formed. If a glycerine ex- 
 tract be made of a pancreas taken from an animal just killed, and if another extract 
 be made from a pancreas which has been kept for twenty-four hours, it will be 
 found that an alkaline solution of the former has practically no effect on fibrin, ■ 
 while the latter is powerfully proteolytic. If a fresh and still warm, pancreas be 
 rubbed up with an equal volume of a 1 per cent, solution of acetic acid, and then / 
 extracted with glycerine, a powerfully proteolytic extract is at once obtained. ' 
 Trypsin is formed from zymogen by the action of acetic acid {Heidenhain). 
 There is reason to believe that trypsin is formed from zymogen by oxidation, 
 and that the former loses its proteolytic power after removal of its oxygen. . 
 The amount of zymogen present in the gland cells seems to depend upon 
 the number and size of the granules present in the inner granular zone of the 
 secretory cells.] 
 
 Disturbing Conditions. — The addition of NaCl, sodic glycocholate, and carbonate, increases 
 the activity of the ferment {Heidenhain), while MgS0 4 diminishes it {Pfeiffer). 
 
 [In dogs poisoned with CO, the trypsin no longer has any action on albumin and fibrin. An infu- 
 sion of the CO-pancreas becomes active when oxygen is driven through it {Herzen). Poisoning 
 with C0 2 , however, does not affect the tryptic activity.] 
 
 Further Effects. — When the trypsin is allowed to act upon the peptone 
 formed by its own action, the peptone is partly changed into the amido acid, leu- 
 cin, or amido- caproic acid (Ce'HflNO,, and tyrosin (C 9 H I1 NO !) '), which belongs to 
 the aromatic series {Kiihne, § 252, IV, 3). Hypoxanthin, xanthin {Salomon), and 
 asparaginic or amido-succinic acid (C 4 H 7 N0 4 ), are also formed during the diges- 
 tion of fibrin and gluten, and so are glutaminic acid (C 5 H 9 N0 4 "), amido-valerianic 
 and (CsHnNOii). Gelatin is first changed into a gelatin peptone, and afterward is 
 decomposed into glycin and ammonia. 
 
 
 Ik 
 
282 
 
 DIGESTIVE ACTION OF THE PANCREATIC JUICE. 
 
 Putrefactive Phenomena. — If the action of the pancreatic juice be still fur- 
 ther prolonged, especially if the reaction be alkaline, a body with a strong, stink- 
 ing, disagreeable faecal odor, indol (C 8 H,N), volatile fatty acids, skatol (C 9 H 9 N), 
 and phenol (C 6 H 6 0) and a substance which becomes red on the addition of chlo- 
 rine or bromine water {Bernard') are formed, while, at the same time, H, C0 2 , 
 H 2 S, CH 4 , and N are given off. The formation of indol and the other substances 
 just mentioned depends upon putrefaction (§ 184, III). Their formation is pre- 
 vented by the addition of calomel, salicylic acid, or thymol, which kills the organ- 
 isms upon which putrefaction depends (Hufner. Kilhne). 
 
 [Artificial Digestion. — If some fibrin be placed in pancreatic juice, or in a 1 
 per cent, solution of sodium carbonate containing the ferment trypsin, peptones 
 are rapidly formed. When we compare gastric with pancreatic digestion, 
 we find that there are marked differences. The fibrin in pancreatic digestion is 
 eroded, or eaten away, and never swells up. The process takes place in an alka- 
 line medium, and never in an acid one. In fact, a 1 per cent, solution of sodic 
 carbonate seems to play the same part in assisting trypsin that a .2 per cent, solu- 
 tion of HC1 does for pepsin in gastric digestion. In gastric digestion acid albu- 
 min or syntonin is formed in addition to the true peptones. In pancreatic diges- 
 tion a body resembling alkali albumin, which passes into a globulin-like body, and 
 ultimately into a tryptic peptone or tryptone is formed. , Of the peptones so 
 formed, one is called antipeptone, and it is not further changed, but part of the 
 proteid is changed in a by-product, hemipeptone. This body, when acted upon, 
 yields leucin and tyrosin. When putrefaction takes place, the bodies above men- 
 tioned are also formed. We might represent the action of trypsin thus : Proteid 
 + trypsin + 1 per cent, sodium carbonate, kept at 38 C. = formation of a 
 globulin-like body, and then antipeptone and hemipeptone are formed. 
 
 Antipeptone 
 
 undergoes no 
 further change. 
 
 yields. 
 
 Hemipeptone 
 
 yields. 
 
 Normal Digestive 
 Products. 
 
 Putrefactive Products. 
 
 Leucin, 
 Tyrosin, 
 Hypoxanthin, 
 Asparaginic Acid. 
 
 Indol, 
 Skatol, 
 Phenol, 
 
 Volatile Fatty Acids, 
 H, CO,, H 2 S, 
 CH 4 , N. 
 
 It seems that trypsin in pure water can act slowly upon fibrin to produce pep- 
 tone. Pepsin cannot do this without the aid of an acid.] 
 
 When proteids are boiled for a Ions; time with dilute H 2 S0 4 , we obtain peptone, then leucin and 
 tyrosin (Kiihne) ; gelatin yields glycin. Hypoxanthin and xanthin are obtained in the same way 
 by similarly boiling fibrin, and the former may even be obtained by boiling fibrin with water {Chit- 
 tenden). 
 
 Papain. — It is very remarkable that the juice of the green fruit of the papaya tree (Carica papaya) 
 1 possesses digestive properties {Roy, Wittmack), and the action is due to an albuminous peptonizing 
 ferment, closely related to trypsin, and called caricin or papain. [It forms a true peptone, an inter- 
 mediate body, leucin and tyrosin. It also contains a milk-coagulating ferment (Martin).] The 
 milky juice of the fig tree has a similar action. 
 
 According to Gorup-Besanez, sprouting malt, vetch, hop, hemp during sprouting, and the recep- 
 tacle of the artichoke, contain a peptonizing ferment. 
 
 Leucin, tyrosin, glutaminic and asparaginic acids, and xanthin are formed in the seeds of some 
 plants; hence we may assume that the processes of decomposition in some seeds are closely allied 
 to the fermentative actions that occur in the intestine (Salomon). 
 
 III. The action on neutral fats is twofold : (1) It acts upon fats so as to 
 form a fine permanent emulsion (Eberle). (2) It causes neutral fats to take up a 
 molecule of water and split into glycerine and their corresponding fatty acids : — 
 
 Tristearin. Water. 
 
 (C 5 ,H 110 O 6 ) + 3 (H 2 0) 
 
 Glycerine. 
 
 Stearic Acid. 
 
 (C 3 H 8 3 ) + 3(C 18 H 36 2 ). 
 
SECRETION OF PANCREATIC JUICE. 283 
 
 The latter result is due to the action of an easily decomposable fat-splitting fer- 
 ment {CI. Bernard), also called steapsin. Lecithin is decomposed by it into 
 glycero-phosphoric acid, neurin and fatty acids {Bokay). After the decomposi- 
 tion is completed, the fatty acids are partly saponified 'by the alkali of the pancre- 
 atic and intestinal juices and partly emulsionized by the alkaline intestinal juice 
 (_/". Munk). Both the soaps and emulsions are capable of being absorbed (§ 191). 
 
 Emulsification. — The most important change effected on fats in the small intestine is the pro- 
 duction of an emulsion, or their subdivision into exceedingly minute particles ($ 191). This is neces- 
 sary in order that the fats may be taken up by the lacteals. If the fat to be emulsified contains a free 
 fatty acid, i. e., if it be slightly rancid, and if the fluid with which it is mixed be alkaline, emulsifica- 
 tion takes place extremely rapidly (Brzicke). A drop of cod-liver oil, which in its unpurified condi- 
 tion always contains fatty acids, on being placed in a drop of 0.3 per cent, solution of soda, instantly 
 gives rise to an emulsion ( Gad). The excessively minute oil globules that compose the emulsion 
 are 'first covered with a layer of soap, which soon dissolves, and in the process small globules are 
 detached from the original oil globules. The fresh surface is again covered by a soap film, and the 
 process is repeated over and over again until an excessively fine emulsion is obtained (G. Quincke). 
 If the fat contain much fatty acid and the solution of soda be more concentrated, " myelin forms" 
 are obtained similar to those which are formed when fresh nerve fibres are teased in water (Briicke). 
 Animal oils emulsionize more readily than vegetable oils; castor oil does not emulsionize (Gad). 
 
 |"It is extremely difficult to obtain a perfectly neutral oil, as most oils contain a trace of a fatty 
 acid. In fact, if, on adding a weak solution of sodic carbonate to oil or fatty matters, fluid at the 
 temperature of the body, an emulsion is obtained, one may be sure that the oil contained a fatty 
 acid, so that Bernard's view about an " emulsive ferment " being necessary is not endorsed. The 
 fatty acid set free by the fat-splitting ferment enables the alkaline pancreatic juice at once to produce 
 an emulsion.] 
 
 Fat-Splitting Ferment. — This is a very unstable body, and must be prepared from the perfectly 
 fresh gland by rubbing it up with powdered glass, glycerine, and a 1 per cent, solution of sodic car- 
 bonate, and allowing it to stand for a day or two (GrUtzner). [This ferment is said to cause an 
 emulsion of oil and mucilage tinged blue with litmus at 40 C. to become red (Gamgee). In per- 
 forming this experiment notice that the mucilage is perfectly neutral, as gum arabic is frequently 
 acid] 
 
 [Pancreatic Extracts. — The action of the pancreas may be tested by making a watery extract 
 of a perfectly fresh gland. Such an extract always acts upon starch and generally upon fats, but 
 this extract and also the glycerine extract vary in their action upon proteids at different times. If 
 the extract — watery or glycerine — be made from the pancreas of a fasting animal, the tryptic action 
 is slight or absent, but is active if it be prepared from a gland 4 to 10 hours after a meal. The 
 pancreatic preparations of Benger, of Manchester, Savory and Moore, or Burroughs and Welcome, 
 all possess active diastatic and proteolytic properties.] 
 
 [Pancreas Salt. — Prosser- James proposes to employ common salt mixed with pepsin, which he 
 calls peptic salt ; and he advocates the use of another preparation composed of the pancreatic fer- 
 ments and common salt, pancreatic salt.] 
 
 The pancreas of new-born children contains trypsin and the fat-decomposing ferment, but not 
 the diastatic one (Zweifel). A slight diastatic action is obtained after two months, but the full effect 
 is not obtained until after the first year (Korowin). 
 
 IV. According to Kiihne and W. Roberts, the pancreas contains a milk-curd- 
 ling ferment, which may be extracted by means of a concentrated solution of 
 common salt. 
 
 171. THE SECRETION OF THE PANCREATIC JUICE.— 
 Rest and Activity. — As in other glands, we distinguish a quiescent state, during 
 which the gland is soft and pale, and a state of secretory activity, during which 
 the organ swells up and appears pale red. The latter condition only occurs after 
 a meal, and is caused probably in a reflex way, owing to stimulation of the nerves 
 of the stomach and duodenum. Kiihne and Lea found that all the lobules of the 
 gland were not active at the same time. The pancreas of the herbivora secretes 
 uninterruptedly [but in the dog secretion is not constant]. 
 
 Time of Secretion. — According to Bernstein and Heidenhain the secretion 
 begins to flow when food is introduced into the stomach, and reaches its maximum 
 2 to 3 hours thereafter. The amount falls toward the 5th or 7th hour, and rises 
 again (owing to the entrance of the chyme into the duodenum) toward the 9th 
 and nth hour, gradually falling toward the i7th-24th hour, until it ceases com- 
 pletely. When more food is taken the same process is repeated. As a general 
 
284 STRUCTURE OF THE LIVER. 
 
 rule, when the secretion occurs rapidly it contains less solids than when it takes 
 place slowly. 
 
 Condition of Blood Vessels. — During secretion, the blood vessels behave 
 like the blood vessels of the salivary glands after stimulation of the chorda — they 
 dilate, and the venous blood is bright red — thus, it is probable that a similar 
 nervous mechanism exists [but as yet no such mechanism has been discovered]. 
 The secretion is excreted at a pressure of more than 17 mm. Hg (rabbit). 
 
 Effect of Nerves upon the secretion. The nerves arise from the hepatic, 
 splenic, and superior mesenteric plexuses, together with branches from the vagus 
 and sympathetic. The secretion is excited by stimulation of the medulla 
 oblongata {Heidenhain and Landau), as well as by direct stimulation of the gland 
 itself by induction shocks {Kilhne and Led). [It is not arrested by section of 
 the cervical spinal cord.] The secretion is suppressed by atropin [in the dog, 
 but not the rabbit], by producing vomiting {CI. Bernard), by stimulation of the 
 central end of the vagus {C. Ludwig and Bernstein), as well as by stimulation of 
 other sensory nerves, e.g., the crural and sciatic {Afanassiew and Pawlow), 
 Extirpation of the nerves accompanying the blood vessels prevents the above- 
 named stimuli from acting. Under these circumstances a thin " paralytic 
 secretion " -with feeble digestive powers is formed, but its amount is not in- 
 fluenced by the taking of food {Bernstein). [Secretion is excited by the injection 
 of ether into the stomach.] 
 
 Extirpation of the gland may be performed {Sckiff), or the duct ligatured in animals (Frerichs), 
 without causing any very great change in their nutrition; the absorption of fat from the intestine 
 does not cease. After the duct is ligatured it may be again restored. Ligature of the duct may 
 cause the formation of cysts in the duct and atrophy of the gland substance [Pawlow). Pigeons 
 soon die after this operation {Langendorff). 
 
 [172. PREPARATION OF PEPTONIZED FOOD.]— [Peptonized 
 food may be given to patients whose digestion is feeble. Sir Wm. Roberts, of 
 Manchester, uses various forms of this food. Food may be peptonized either by 
 peptic or tryptic digestion, but the former is not so suitable as the latter, because 
 in peptic digestion the grateful odor and taste of the food are destroyed, while 
 bitter by-products are formed. Hence, Dr. Roberts employs pancreatic diges- 
 tion, which yields a more palatable and agreeable product. As tryspin is destroyed 
 
 r by gastric digestion, obviously it is useless to give extract of the pancreas to a 
 
 Inpatient along with his food.] 
 
 [Peptonized Milk. — " A pint of milk is diluted with a quarter of a pint of water and heated 
 to 60° C. Two or three teaspoonfuls of Benger's liquor pancreaticus, together with ten or twenty 
 grains of bicarbonate of soda, are then mixed therewith." Keep the mixture at 38 C. for about 
 two hours, and then boil it for two or three minutes, which arrests the ferment action.] 
 
 [Peptonized Gruel, prepared from oatmeal, or any farinaceous food, is more agreeable than 
 peptonized milk, as the bitter flavor does not appear to be developed in the pancreatic digestion of 
 vegetable proteids.] 
 
 Peptonized Milk Gruel yielded Roberts the most satisfactory results, as a complete and highly 
 nutritious food for weak digestions. Make a thick gruel from any farinaceous fot^d, e.g., oatmeal, 
 and while still hot add to it an equal volume of cold milk, when the mixture will have a tempera- 
 ture of. 52° C. (125° F.)'. To each pint of this mixture add two or three teaspoonfuls of liquor 
 pancreaticus and 20 grains of bicarbonate of soda. It is kept warm for two hours under a " cosey." 
 It is then boiled for a few minutes and strained. The bitterness of the digested milk is almost 
 completely covered by the sugar produced during the process {Roberts)."] 
 
 [Peptonized soups and beef tea have also been made and used with success, and have been 
 administered both by the mouth and rectum.] 
 
 [Peptonizing powders containing the proner proportions of ferment and sodic bicarbonate are 
 prepared by Benger, and Burroughs and Welcome.] 
 
 173. STRUCTURE OF THE LIVER.— The liver, the largest gland 
 in the body, consists of innumerable small lobules or acini, 1 to 2 millimetres 
 CsV to y 1 ^ inch) in diameter. These lobules are visible to the naked eye. All the 
 lobules have the same structure. 
 
STRUCTURE OF THE UVER. 
 
 285 
 
 1. The Connective Tissue and Capsule. — The liver is covered by a thin, fibrous, firmly 
 adherent capsule, which has on its free surface a layer of endothelium derived from the peritoneum. 
 The capsule sends fine septa into the organ between the lobules, but it is also continued into the 
 interior at the transverse fissure, where it surrounds the portal vein, hepatic artery, and bile duct, 
 and accompanies these structures as the Capsule of Glisson or interlobular connective tissue. 
 The spaces in which these three structures lie are known as portal canals. In some animals (pig, 
 camel, polar bear), the lobules are separated from each other by the somewhat lamellated connective 
 tissue of Glisson's capsule, but in man this is but slightly developed, so that adjoining lobules are 
 more or less fused. Very delicate connective tissue, but small in amount, is also found within the 
 lobules {Fleischl, Kupffer). Leucocytes are sometimes found in the tissue of Glisson's capsule. 
 
 2. Blood Vessels. — (a) Branches of the Venous System. — If the vena porta be traced from 
 its entrance into the liver at the portal fissure, it will be found to give off numerous branches lying 
 between the lobules, and ultimately forming small trunks which reach the periphery of the lobules, 
 
 Fig. 178. 
 
 I. Scheme of a liver lobule. — V. i, V. i t interlobular veins (portal) ; V. c, central or intralobular vein (hepatic) ; c, c, 
 capillaries between both; V. j, sub-lobular vein; V. », vena vascularis; A, A, branches of the hepatic artery, 
 giving branches, r, r, to Glisson's capsule and the larger vessels, and ultimately forming the venae vasculares at 
 i, i, opening into the intralobular capillaries ; g, branches of the bile ducts ; x, x, intralobular bile capillaries 
 between the liver cells ; d, d, position of the liver cells between the meshes of the blood capillaries. II, Isolated 
 liver cells — c, a blood capillary ; a, fine bile capillary channel. 
 
 where they form a rich plexus. These are the interlobular veins (Fig. 178, V. i). From these 
 veins numerous capillaries [c, c) are given off to the entire periphery of the lobule. The capillaries 
 converge toward the centre of the lobule. As they proceed inward, they form elongated meshes, 
 and between the capillaries lie rows or columns of liver cells (d, d). The capillaries are relatively 
 wide, and are so disposed as to lie between the edges of the columns of cells, and never between 
 the surfaces of two neighboring cells. The capillaries converge toward the centre of each lobule, 
 where they join to form one large vein, the intralobular or central vein (V. c), which traverses 
 each lobule, reaches its surface at one point, passes out, and joins similar veins from other lobules to 
 form the sublobular veins (V. s). These in turn unite to form wide veins, the origins of the 
 hepatic veins, which open into the vena cava inferior. 
 
 (d) Branches of the Hepatic Artery. — The branches of the hepatic artery accompany the 
 branches of the portal vein and bile duct in the portal canals between the lobules, and in their 
 course they give off capillaries to supply the walls of the portal vein and larger bile ducts. The 
 
286 
 
 STRUCTURE OF THE LIVER. 
 
 branches of the hepatic artery anastomose frequently where they lie between the lobules. On 
 reaching the periphery of the lobules, a certain number of capillaries are given off, which penetrate 
 the lobule and terminate in the capillaries of the portal vein (z, i). These capillaries, however, 
 which supply the walls of the portal vein and large bile ducts (r. r), terminate in veins which end 
 in the portal vein (V. n — Ferrein). Several branches — capsular — pass to the surface of the liver, 
 where they form a wide-meshed plexus under the peritoneum. The blood is returned by veins 
 which open into branches of the portal vein, 
 
 [Hepatic Zones. — Pathologists draw a sharp distinction between different zones within a hepatic 
 lobule. Thus the central area, capillaries and cells form the hepatic vein zone, which is specially 
 liable to cyanotic changes ; the area next the periphery of the lobule is the portal vein zone, whose 
 cells under certain circumstances are particularly apt to undergo fatty degeneration; while there is 
 an area lying midway between the two foregoing — the hepatic artery zone — which is specially 
 liable to amyloid or waxy degeneration.] 
 
 3. The Hepatic Cells (Fig. 178, li, a) are irregular polygonal cells of about ysss °f an i ncn 
 (34 to 45 /*) in diameter (Fig. 179). The arrangement of the capillaries within a lobule deter- 
 mines the arrangement of the liver cells. The liver cells form anastamosing columns which radiate 
 from the centre to the periphery of each lobule (Fig. 180). [The liver cells are usually stated to 
 be devoid of an envelope, although Haycraft states that they possess one. They usually contain 
 a single nucleus, with one or more nucleoli, but sometimes two nuclei occur. The protoplasm and 
 nucleus of each cell contains a plexus of fibrils, just like other epithelial cells. In some animals, 
 globules of oil and pigment granules are found in the cell protoplasm (Fig. 179).] Each cell is in 
 relation with the wide-meshed blood capillaries {a", d), and also with the much narrower meshwork 
 of bile ducts (I, x). 
 
 Effect of Foods. — It is important to observe that the appearance of the cells varies with the 
 
 Fig. 180. 
 
 Fig. 179. 
 
 Human liver cells The cell protoplasm contains 
 biliary coloring matter and oil globules, b ; d 
 has two nuclei. 
 
 
 Appearance of the liver cells after 
 witholding food for thirty- 
 six hours. 
 
 period of digestion. During hunger, the liver cells are finely granular and very cloudy (Fig. 180). 
 About thirteen hours after a full meal, especially of starchy food, they contain coarse glancing masses 
 of glycogen (Fig. 182, 2). The protoplasm near the surface of the cell is condensed, and a fine 
 network stretches toward the centre of the cell, and in it is suspended the nucleus {Kupffer, Hei- 
 denhain). [Afanassiew finds that if the formation of bile in the liver be increased (e.g., by section 
 of the hepatic nerves, or feeding with proteids), the cells are moderately enlarged in size, and con- 
 tain numerous granules which are proteid in their nature ; such cells resist the action of caustic 
 potash. When there is a great formation of glycogen (as after feeding with potatoes and sugar), 
 all the cells are very large and sharply defined, while their bodies are loaded with granules of gly- 
 cogen, the cells being so large as to compress the capillaries. These cells dissolve quickly in caustic 
 potash. The network within the cells is best seen after solution of the glycogen.] 
 
 4. The Bile Ducts. — The finest bile capillaries or canaliculi arise from the centre of the lobule, 
 and, indeed, throughout the whole lobule, they form a regular anastomosing network of very fine 
 tubes or channels. Each cell is surrounded by a polygonal — usually hexagonal — mesh (Fig. 178, 
 xx). The bile capillaries always lie in the middle of the surface between two adjoining cells 
 (II, a), where they form actual intercellular passages (Fig. 181) (Hering). [According to some 
 observers, they are merely excessively narrow channels (1 to 2 f- wide) in the cement substance 
 between the cells, while according to others, they have a distinct delicate wall {Fritsch, Miura). 
 The bile capillary network is much closer than the blood capillary network. [Thus, there are 
 three networks within each lobule — 
 
 (1) A network of blood capillaries; 
 
 (2) " hepatic cells ; 
 
 (3) " bile capillaries; (Fig. 181.] 
 
STRUCTURE OF THE LIVER. 
 
 287 
 
 Excessively minute intracellular passages are said to pass from the bile capillaries into the 
 interior of the liver cells, where they communicate with certain small .cavities or vacuoles (Asp, 
 Kupffer, Pfiuger — Fig. 182, 3). As the blood capillaries run along the edges of the liver cells, 
 and the bile capillaries between the opposed surfaces of adjacent cells, the two systems of canals 
 within the lobule are kept separate. Some bile capillaries run along the edges of the liver cells in 
 the human liver, especially during embryonic life (Zuckerkandi, loldt). Toward the peripheral 
 
 Fig. i8i. 
 
 Blood vessel. 
 
 Finest bile duct 
 divided. 
 
 Finest bile duct. 
 
 Finest bile duct. 
 
 Blood capillaries, finest bile ducts in their relative position in a rabbit's liver (E. Hering). 
 
 part of the lobule, the bile capillaries are larger, while adjoining channels anastomose and leave 
 the lobule, where they become interlobular ducts (g), which join with other similar ducts to form 
 larger interlobular bile ducts. These accompany the hepatic artery and portal vein, and leave the 
 liver at the transverse fissure. The finer interlobular ducts frequently anastomose in Glisson's cap- 
 sule (Asp), possess a structureless basement membrane, and are lined by a single layer of low, 
 polyhedral, epithelial cells. The larger interlobular ducts have a distinct wall consisting of con- 
 
 Fig. 183. 
 
 Fig. 182. 
 
 I 2 3 
 
 1, Liver cell during; fasting ; 2, containing masses 
 of glycogen; 3, a liver cell surrounded with 
 bile channels, trom which fine twigs proceed 
 into the cell substance, where they end in 
 vacuole-like enlargements. From a rabbit's 
 liver injected with Berlin blue from the bile 
 duct. 
 
 Circular 
 fibres. 
 
 Cylindrical 
 epithelium. , '& 
 
 mm 
 
 Interlobular bile duct (Human). 
 
 nective and elastic tissue, mixed with circularly disposed, smooth, muscular fibres (Fig. 183). 
 Capillaries are supplied to the wall, which is lined by a single layer of columnar epithelium. A 
 sub-mucosa occurs only in the largest bile ducts, and in the gall bladder. Smooth muscular fibres, 
 arranged in single bundles, occur in the largest ducts, and as longitudinal and circular layers in the 
 gall bladder, whose mucous membrane is provided with numerous folds and depressions. The 
 epithelium lining the gall bladder is cylindrical, with a distinct, clear disk, and between these cells 
 
288 CHEMICAL COMPOSITION OF THE LIVER CELLS. 
 
 are goblet cells. Small branched tubular mucous glands occur in the small bile ducts and in the 
 gall bladder. 
 
 Vasa Aberrantia are isolated bile ducts which occur on the surface of the liver, but have no 
 relation to any system of liver lobules. They occur at the sharp margin of the liver in the region 
 of the inferior vena cava, of the gall bladder, and of the parts near the portal fissure. It seems 
 that the liver lobules to which they originally belonged have atrophied and disappeared {Zuckerkandl 
 and Toldt). 
 
 (5) The Lymphatics begin as peri- capillary tubes around the capillaries within the lobules 
 (MacGillavry). They emerge from the lobule and run within the wall of the branches of the 
 hepatic and portal veins, and afterward surround the venous trunks (Fleischl, A. Budge), thus form- 
 ing the interlobular lymphatics. These unite to form larger trunks, which leave the liver partly at 
 the portal fissure, partly along with the hepatic veins, and partly at different points on the surface 
 of the organ. There is a narrow superficial meshwork of lymphatics under the peritoneum — sub- 
 peritoneal — which communicate with the thoracic lymphatics through the triangular ligament and 
 suspensorium, while on the under surface they communicate with the lymphatics of the interlobular 
 connective tissue. 
 
 (6) The Nerves consist partly of medullated and partly of non-medullated fibres from branches 
 of the sympathetic and left vagus to the hepatic plexus. They accompany the branches of the 
 hepatic artery, and ganglia occur on their branches within the liver. Some of the nerve fibres are 
 vasomotor in function, and according to Pliiger, other nerve fibres terminate directly in connection 
 with liver cells, although this observation has still to be confirmed. 
 
 Pathological. — The connective tissue between the lobules may undergo great increase in 
 amount, especially in alcohol and gin drinkers, and thus the substance of the lobules may be 
 greatly compressed, owing to the cicatricial contraction of the newly-formed connective tissue (cir- 
 rhosis of the liver). In such interlobular connective tissue, newly-formed bile ducts are found 
 (Cornil, Charcot arid others). 
 
 Ligature of the ductus choledochus [causes enlargement of the spleen (rabbit) and a diminu- 
 tion in the number of the blood corpuscles {Mackey)~\, and, after a lime, interstitial inflam- 
 mation of the liver. In rabbits and guinea pigs the liver parenchyma disappears, and its place is 
 taken by newly-formed connective tissue and bile ducts [Charcot and Gombault). In all these 
 cases of interstitial inflammation, there is proliferation of the epithelium of the bile ducts (Fod, 
 Salvioli). According to Beloussow, the dilated bile ducts partly burst, and partly (owing to 
 pressure) undergo necrosis, and thereafter in the neighborhood of these foci inflammatory reaction 
 sets in, with cell infiltration, formation of new connective tissue, and regenerative new formation of 
 bile ducts. 
 
 [Regeneration of the Liver. — Tizzoni finds that there may be partial regeneration and new 
 formation of liver lobules in the dog, the process being the same as that which occurs in the embry- 
 onic development of the organ, i. e., the growth of solid cylinders of liver cells, formed by the pre- 
 existing liver cells, which penetrate into the connective tissue uniting the edges of the wound. 
 These cells ultimately differentiate into hepatic cells and bile ducts. Griffini also confirms the fact 
 of the regeneration of the hepatic substance in the dog and rabbit, but he thinks that the new forma- 
 tion is developed by the outgrowth of the epithelial cells of the bile cells.] 
 
 174. CHEMICAL COMPOSITION OF THE LIVER CELLS.— 
 
 (1) Proteids. — The fresh, soft parenchyma of the liver is alkaline in reaction ; 
 after death, coagulation occurs, the cell contents appear turbid, the tissue becomes 
 friable, and gradually an acid reaction is developed. This process closely 
 resembles what occurs in muscle, and is due to the coagulation of a myosin-like 
 body, which is soluble during life, but after death undergoes spontaneous coagula- 
 tion (JPlosz). The liver contains other albuminous bodies; one coagulating at 45 
 C, another at 70 C, and one which is slightly soluble in dilute acids and alkalies. 
 The cell nuclei contain nuclein JPldsz). The connective tissue yields gelatin. 
 
 (2) Glycogen or Animal Starch — 1.2 to 2.6 per cent. —is most closely 
 related to inulin, is soluble in water, but diffuses with difficulty, is a true carbohy- 
 drate (C/. Bernard and v. Hensen, i8j 7), and has the formula 6(C 6 H 10 O 6 ) + 
 H 2 [Ktilz and Borntrager). It is stored up in the liver cells {Bock and Hoff- 
 man), in amorphous granules around the nuclei (Fig. 182, 2), but it is not uni- 
 formly distributed in all parts of the liver (v. WitticK). Like inulin, it gives a 
 deep red color with solution of iodine in iodide of potassium. It is changed into 
 dextrin and sugar by diastatic ferments, and when boiled with dilute mineral 
 acids, it yields grape sugar (§ 148, I ; § 170, I ; § 252, III). 
 
 Preparation of Glycogen.— Let a rabbit have a hearty meal, and kill it three or four hours 
 therealter. The liver is removed immediately after death ; it is cut into fine pieces, plunged into 
 
CHEMICAL COMPOSITION OF THE LIVER CELLS. 289 
 
 toiling water, and boiled for some lime in order to obtain a watery extract of the liver cells. [It is 
 placed in boiling water to de- troy the ferment supposed to be present in the liver, which would trans • 
 form the glycogen into grape sugar.] To the cold filtrate are added alternately dilute hydrochloric 
 acid and potassio-mercuric iodide as long as a precipitate occurs. The albuminates or proteids are 
 precipitated by the iodide compound in the presence of free HC1. It is then filtered, when a clear 
 opalescent fluid, containing the glycogen in solution, is obtained. The glycogen is precipitated 
 from the filtrate, as a while amorphous powder, on adding an excess of 70 to 80 per cent, alcohol. 
 The precipitate is washed with 60 per cent, and afterward with 95 per cent, alcohol, then with ether, 
 and lastly, with absolute alcohol; it is dried over sulphuric acid and weighed (Briicke). 
 
 Ferment. — [F. Eves asserts that the post-mortem conversion of sugar in the liver is not attribut- 
 able to a ferment action, and the rapid appearance of sugar in the liver after death is due to the 
 specific metabolic activity of the dying cells.] 
 
 Conditions which influence its amount. — If large quantities of starch, 
 milk-, fruit-, or cane-sugar, or glycerine, but not mannite or glycol (JLuchsinger), 
 or inosite {Kiilz), be added to the proteids of the food, the amount of glycogen 
 in the liver is very greatly increased (to 12 per cent, in the fowl), while a purely 
 albuminous or partly fatty diet diminishes it enormously. During hunger it almost 
 disappears {Pavy and Tscherinoff). The injection of dissolved carbohydrates 
 into a mesenteric vein of a starving rabbit causes the liver, previously free from 
 glycogen, to contain glycogen {Naunyri). 
 
 [Arsenic, phosphorus, and antimony destroy the glycogenic function of the liver, no glycogen 
 being present in the liver of animals poisoned with these drugs, so that puncture of the floor of the 
 fourth ventricle no longer causes glycosuria in them.] 
 
 During life, under normal conditions, the glycogen in the liver is either not 
 transformed into grape sugar {Pavy, Hitter, Eulenberg), or, what is more prob- 
 able, only a very small amount of it is so changed. The normal amount of sugar 
 in blood is 0.5 to 1 per 1000, although the blood of the hepatic vein contains 
 somewhat more. A considerable amount is transformed into sugar only when 
 there is a decided derangement of the hepatic circulation, and in these circum- 
 stances the blood of the hepatic vein contains more sugar. The glycogen under- 
 goes this change very rapidly after death, so that a liver which has been dead for 
 some time always contains more sugar and less glycogen. 
 
 The Diastatic ferment in the liver is small in amount, and can be obtained 
 from the extract of the liver cells by the same means as are applicable for obtain- 
 ing other similar ferments, such as pytalin ; but it does not seem to be formed 
 within the liver cells, but only passes very rapidly from the blood into them. The 
 ferment seems to be rapidly formed when the blood stream undergoes considerable 
 derangement {Ritter, Schiff). A similar ferment is formed when red blood cor- 
 puscles are dissolved (Tiegel), and, as there is a destruction of red blood corpus- 
 cles taking place continually within the liver, this is one source from which the 
 ferment may be formed, whereby minute quantities of sugar would be continually 
 formed in the liver. 
 
 If glycogen is injected into the blood, achroodejjtrin appears in the urine, and also haemoglobin, 
 as glycogen dissolves red blood corpuscles (Bokm, Hoffmann) . 
 
 Ligature of the bile duct causes decrease of the glycogen in the liver {v. Wittich) ; it appears as 
 if, after this operation, the liver loses the property of forming glycogen from the materials supplied 
 to it. 
 
 (3) The following substances have also been found in the liver cells : Fats, in 
 the form of highly refractive granules in the liver cells, as well as in the bile 
 ducts ; sometimes, when the food contains much fat (more abundant in drunkards 
 and the phthisical), olein, palmitin, stearin, volatile fatty acids, and sarcolactic 
 acid are found. 
 
 [Fatty Degeneration and Infiltration. — Fatty granules are of common occurrence within the 
 cells of the liver, and when they do not occur in too great amount, do not seem to interfere very 
 greatly with the functions of the liver cells. These fatty granules are common in disease, constitut- 
 ing fatty infiltration and degeneration, and in such cases.the cells within a lobule of the liver, next 
 the portal vein, are usually most highly charged with the fatty particles. Fatty particles occur if too 
 
 19 
 
290 DIABETES MELLITUS. 
 
 much fatty food be taken, and they are commonly found in the livers of stall fed animals, and the 
 well-known p&li-de-foie gras is largely composed of the livers of geese which have been fed on large 
 amounts of farinaceous food, and which have been subjected to other unfavorable hygienic condi- 
 tions. Fatty granules are recognized by their highly refractive appearance, by their solubility in 
 ether, and by being blackened by osmic acid.] 
 
 There are also found traces of cholesterin, minute quantities of urea, uric acid. [Leucin (? gu- 
 anin), sarkin, xanthin, cystin, and tyrosin occur pathologically in certain diseases where marked 
 chemical decompositions occur.] 
 
 (4) The inorganic substances found in the human liver are — potassium, 
 sodium, calcium, magnesium, iron, manganese, chlorine, and phosphoric, sul- 
 phuric, carbonic, and silicic acids ; while copper, zinc, lead, mercury, and ar- 
 senic may be accidentally deposited in the hepatic tissue. 
 
 175. DIABETES MELLITUS AND GLYCOSURIA.— [Glycosuria 
 
 is characterized by the presence of grape sugar in the urine. According to Briicke, 
 a trace of sugar exists normally in urine, and when this amount is increased, we 
 have glycosuria. When the normal amount of grape sugar in the blood (o. 1 2 to 
 0.33 per cent.) is increased, grape sugar appears in the urine. In Diabetes 
 Mellitus, grape sugar also appears in the urine, but this is really a serious dis- 
 ease, involving the alteration of many tissues, and distinguished by profound dis- 
 turbance of the whole metabolic activity, which leads to numerous pathological 
 changes and often to death. The appearance of grape sugar in urine does not, 
 necessarily, mean that a person is suffering from this disease]. 
 
 The formation of large quantities of grape sugar by the liver, and its passage 
 into the blood, and from the blood into the urine, are related to the above-men- 
 tioned normal conditions. Extirpation of the liver in frogs (Moleschott), or 
 destruction of the hepatic cells, as by fatty degeneration from poisoning with 
 phosphorus or arsenic {Salkowskt) do not cause this condition. It occurs for 
 several hours, however, after the injury of a certain part — the centre for the hepatic 
 vasomotor nerves — of the floor of the lower part of the fourth ventricle (CI. Ber- 
 nard 1 s piqure) ; also after section of the vasomotor channels in the spinal cord, 
 from above down to the exit of the nerves for the liver, viz., to the lumbar region, 
 and in the frog to the fourth vertebra (Schijf). When the vasomotor nerves, 
 which proceed from this centre to the liver, are cut or paralyzed in any part of 
 itheir course, mellituria or glycosuria is produced. All the nerve channels do not 
 irun through the spinal cord alone. A number of vasomotor nerves leave the spinal 
 cord higher up, pass into the sympathetic, and thus reach the liver; so that de- 
 struction of the superior (Pavy), as well as of the inferior cervical sympathetic 
 ganglion, and the first thoracic ganglion (£ckhard) of the abdominal sympathetic 
 (Klebs, Murik), and often of the splanchnic itself (Hensen, v. Graefe), produces 
 • diabetes. The paralysis of the blood vessels causes the liver to contain much 
 blood, and the intra-hepatic blood stream is slowed. The disturbance of the cir- 
 culation causes a great accumulation of sugar in the liver, as the blood ferment 
 .has time to act upon the glycogen and transform it into sugar. By stimulation of 
 .the sympathetic at the lowest cervical and first thoracic ganglion, the hepatic 
 wessels at the periphery of the liver lobules become contracted and pale' (Cyon, 
 .Aladoff). It is remarkable that glycosuria, when present, may be set aside by 
 section of the splanchnic nerves. This is explained by supposing that the enor- 
 mous dilatation and congestion, or the hyperemia, of the abdominal blood vessels 
 thereby produced, renders the liver anaemic. 
 
 A number of poisons which paralyze the. hepatic vasomotor nerves produce diabetes in a similar 
 way ; constantly after curara (when artificial respiration is not maintained), CO, amyl nitrite, ortho- 
 nitro-propionic acid and methyl delphinin ; another series of poisons in large doses are not constant 
 in. their effect— morphia, chloral hydrate HCN, H 2 S0 4 , mercury, alcohol [phlorizin (v. Mering)'], 
 and such infectious diseases as cholera, anthrax, diphtheria, typhoid and scarlatina. But congestion 
 of the liver produced in other ways appears to cause diabetes, e.g., after mechanical stimulation of 
 the liver. To this class belongs the injection of di'ute saliae solutions into the blood {Bock, Hoff- 
 mann), whereby either the change in form or'the solution of the colored blood corpuscles causes 
 
SOURCES OF GLYCOGEN. 291 
 
 the congestion. The circumstance that repeated blood letting makes the blood richer in sugar, may, 
 perhaps, be explained by the slowing of the circulation. [Injection of a solution of a neutral salt 
 into a ligatured loop of the small intestine sometimes causes mellituria [M. Hay).~\ 
 
 Continued stimulation of peripheral nerves may act reflexly upon the centre for 
 the vasomotor nerves of the liver. Diabetes has been observed to occur after 
 stimulation of the central end of the vagus {CI. Bernard, Eckhard, Ktilz, Lobeck), 
 and also after stimulation of the central end of the depressor nerve {Filehne). 
 Even section, and subsequent stimulation of the central end of the sciatic nerve, 
 causes diabetes {Sehiff, Kith, Bbhm and Hoffmann, Froning). This may explain 
 the occurrence of diabetes in people who suffer from sciatica. 
 
 [Tt may occur, also, after perverted nervous activity, as psychical excitement, neuralgias (sciatica, 
 trigeminal or occipital), concussion of the brain, as well as after certain injuries to the skull and 
 vertebral column and some cerebral diseases.] 
 
 According to Sehiff, the stagnation of blood in other vascular regions of the body may cause the 
 ferment to accumulate in the blood to such an extent that diabetes occurs. The glycosuria that occurs 
 after compression of the aorta or portal vein may, perhaps, be ascribed to this cause, but, perhaps, 
 the pressure produced by these procedures may paralyze certain nerves. According to Eckhard, 
 injury to the vermiform process of the cerebellum of the rabbit causes diabetes. In man, affections 
 of the above-named nervous regions cause diabetes. 
 
 [Tke Consequence of Disturbances of Digestion. — In most individuals the use of a large quantity 
 of sugar in the food is not followed by sugar in the urine ; but in some exceptional cases it is often 
 present, e.g., in persons suffering from gastric catarrh, especially if they are gouly.] 
 
 Theoretical. — In order to explain the more immediate cause of the^e phenomena, several hy- 
 potheses have been advanced : — 
 
 (a) The liver glycogen may be transformed, unhindered, into sugar, as the blood, in its passage 
 through the liver, deposits or gives up the ferment to the liver cells (see above). So that the normal 
 function of the vasomotor system of the liver, and its centre in the floor of the fourth ventricle, may 
 be regarded as, in a certain sense, an " inhibitory system " for the formation of sugar. 
 
 (b) If we assume that, under normal conditions, there is continually a small quantity of sugar 
 passing from the liver into the hepatic vein, we might explain the diabetes as due to the disappear- 
 ance of these decompositions — diminished burning up of the sugar in the blood — which are con- 
 stantly removing the sugar from the blood. In fact, diabetic persons have been found to consume 
 less O (v. Pettenkofer and Voii) and to have an increased formation of urea. 
 
 Sources of Glycogen. — The "mother substance" of the glycogen of 
 the liver has been variously stated to be the carbohydrates of the food {Pavy), 
 fats (olive oil, Salomon), glycerine {van Deen, Weiss), taurin and glycin (the latter 
 splitting into glycogen and urea — Heynsius and Kuthe), the proteids (CV. Bernard), 
 and gelatin (Salomon). If it is derived from the albumins, it must be formed 
 from a non-nitrogenous derivative thereof. 
 
 According to Seegen, the blood of the hepatic vein contains twice as much sugar (0.23 per cent.) 
 as that in the portal vein (o. II 9 per cent.) ; observations on dogs showed that the blood flowing 
 through the liver gives up over 400 grms. sugar. Hence, in carnivora, the greatest part of the C of 
 the animal food must pass into sugar, so that the formation of sugar in the liver and its decomposi- 
 tion in the blood, or in the organs traversed by the blood, must be a very important function of the 
 metabolism. Seegen is also of opinion that the liver glycogen takes no part in the formation of 
 sugar in the liver. 
 
 Rohmann found that the use of ammonia in rabbits considerably increased the formation of gly- 
 cogen. The excessive formation of acid in diabetes observed by Stadelmann unites with the 
 ammonia and diminishes considerably the formation of glycogen. 
 
 [Injection of Grape Sugar into the Blood. — When grape sugar is injected into the jugular 
 vein of a dog, only 33 per cent, at most is given off in the urine, while usually within two to five 
 hours the urine is free from sugar. Even within a few minutes after the injection only a certain 
 proportion (}4-/6) °f tne sugar is found in the blood; a part of the sugar has been detected in the 
 muscles, liver, and kidneys, but the fate of the remainder is not known. Immediately after the 
 injection, the amount of hsemoglobin and also of serum albumin is diminished (50 per cent.), which 
 is due to increase of the quantity of water within the vessels ; but within two hours this dispropor- 
 tion is restored to the normal stale {Brasol). In a curarized dog the injection of grape sugar into a 
 vein increases the blood pressure, but this effect is not observed after the injection of morphia and 
 chloral (Albertoni).'] 
 
 Effects of Food. — Rabbits whose livers have been rendered free from gly- 
 cogen by starvation, yield new glycogen from their livers when they are fed with 
 
292 THE FUNCTIONS OF THE LIVER. 
 
 cane sugar, grape sugar, maltose, or starch. Forced muscular movements soon 
 make the liver of dogs free from glycogen, exposure to cold diminishes its amount. 
 Dextrin and grape sugar occur in the dead liver (Limpricht, Kiilz), but in addition, 
 some glycogen is found for a considerable time after death in the liver and in the 
 muscles. 
 
 Other Situations. — Glycogen is by no means confined to the liver cells ; it occurs during foetal 
 life in all the tissues of the body of the embryo [including the embryonic skeleton [Paschutin)~\, 
 also in young animals [Kiihne], and in the placenta [Bernard]. In the adult it occurs in the tes- 
 ticle [Kiihne), in the muscles [Mac Donnel, O. JVasse), in numerous pathological products, in in- 
 flamed lungs [Kuhne), and also in the corresponding tissues of the lower animals. [It also occurs 
 in the ch< irionic villi ( CI. Bernard), in colorless blood corpuscles, in fresh pus cells which still 
 exhibit amoeboid movements, and, in fact, in all developing animal cells, with amoeboid movement ; 
 it is a never failing constituent in cartilage, and in the muscles and liver of invertebrata, such as the 
 oyster [Hoppe-Seyler). There is none in the fresh brain of the dog or rabbit, but it is found in the 
 brain in diabetic coma [Abeles).~\ 
 
 Persons suffering from diabetes require a large amount of food ; they suffer 
 greatly from thirst, and drink much fluid. They exhibit signs of marked emacia- 
 tion, when the loss of the body is greater than the supply. [In advanced diabetes 
 the glycogenic function of the liver is almost abolished, as was proved by remov- 
 ing with a trocar a small part of the liver from man (jEhrlich), when almost no 
 glycogen was found. The absorbed sugar in the portal vein passes directly into 
 the general circulation without being submitted to the action of the liver 
 (v. Frerichs).~] In severe cases, toward death, not unfrequently a peculiar 
 comatose condition — diabetic coma — occurs, when the breath often has the 
 odor of acetone, which is also found in the urine {Fetters). But neither 
 acetone nor its precursor, aceto-acetic acid, nor aethyl-diacetic acid, nor the 
 unknown substance in diabetic urine which gives the red color with ferric 
 chloride (v. JakscK), is the cause of the coma {Frerichs and Brieger). The 
 urinary tubules often show the signs of coagulation necrosis, which is recognized 
 by a clear, swollen-up condition of the dead cells (Ebstein). As yet there is 
 no satisfactory explanation of those rarer cases of " acetonaemia " without 
 diabetes {Kanlecti, Cantini, v. JakscK). 
 
 176. THE FUNCTIONS OF THE LIVER.— [In order to under- 
 stand the functions of the liver, we must remember its unique relation to the 
 vascular and digestive systems, whereby many of the products of gastric and in- 
 testinal digestion have to traverse it before they reach the blood, and, in fact, as 
 some of them traverse the liver they are altered. We have still much to learn re- 
 garding these offices of the liver, but it has several distinct functions — some 
 obvious, others not. (1) The liver secretes bile, which is formed by the hepatic 
 cells, and leaves the organ by the bile ducts, to be poured by them into the duo- 
 denum. (2) But the liver cells also form glycogen, which does not pass into the 
 ducts, but in some altered and diffusible form passes into the blood stream, and 
 leaves the liver by the hepatic veins. Hence, the study of the liver materially 
 influences our conception of a secreting organ. In this case, we have the pro- 
 ducts of its secretory activity leaving it by two different channels — the one by the 
 ducts, and the other by the blood stream. The liver, therefore, is a great store- 
 house of carbohydrates, and it serves them out to the economy as they are 
 required. All this points to the liver as being an organ intimately related to the 
 general metabolism of the body. (3) In a certain period of development it 
 is concerned in the formation of blood corpuscles (§ 7). (4) It has some relation 
 to the breaking up of blood corpuscles and the formation of urea and other 
 metabolic products (§ 20, § 177, 3). (5) Brunton attributes some importance to 
 the liver in connection with the arrest of certain substances absorbed from the 
 alimentary canal, whereby they are either destroyed, stored up in the liver, or, it 
 may be, prevented from entering the general circulation in too large amount. It 
 is possible that ptomains may be arrested in this way (§ 166).] 
 
THE BILE ACIDS. 293 
 
 177. CONSTITUENTS OF THE BILE. — Bile is a yellowish-brown 
 or dark green colored transparent fluid, with a sweetish, strongly bitter taste, 
 feeble musk- like odor and neutral reaction. The specific gravity of human bile 
 from the gall-bladder = 1026 to 1032, while that from a fistula = 1010 to ion 
 (Jacobsen). It contains — 
 
 (1) Mucus, which gives bile its sticky character, and not unfrequently makes 
 it alkaline, is the product of the mucous glands and the goblet cells of the mucous 
 membrane of the larger bile ducts. When bile is exposed to the air, the mucus 
 causes it to putrefy rapidly. It is precipitated by acetic acid or alcohol. 
 
 [Bile from the gall bladder, when poured from one vessel into another, shows the presence of 
 mucin in the form of thin threads connecting the fluids in the two vessels. When such bile is 
 treated with alcohol, it no longer exhibits this property, but flows like a non viscid watery fluid. 
 The bile formed in the ultimate bile ducts does not seem to contain mucin or mucus, but bile from 
 the gall bladder always does. It is formed from the mucous glands in the larger bile ducts 
 
 (« »73)-] 
 
 (2) The Bile Acids. — Glycocholic and taurocholic acids, so-called conjugate 
 acids, are united with soda (in traces with potash) to form glycocholate and 
 taurocholate of soda, which have a bitter taste. In human bile (as well as in that 
 of birds, many mammals and amphibians), taurocholic acid is most abundant ; in 
 other mammals (pig, ox) glycocholic acid is most abundant. These acids rotate 
 the plane of polarized light to the right. 
 
 [The bile from a biliary fistula is sometimes not bitter.] 
 
 (a) Glycocholic acid, C 26 H 43 N0 6 (first discovered and described as cholic acid 
 by Gmelin, and called by Lehmann glycocholic acid). When boiled with caustic 
 potash, or baryta water, or with dilute mineral acids, it takes up H 2 {Strecker), 
 and splits into — 
 
 Glycin ( = Glycocoll = Gelatin Sugar = Amido-acetic acid) = C 2 H 5 N0 2 . 
 
 + Cholalic acid (also called Cholic acid) = C 24 H 40 O 6 . 
 
 = Glycocholic acid + Water = C^H^NO, + H a O. 
 
 (b) Taurocholic acid, C 26 H 45 NSO„ when similarly treated, takes up water 
 and splits into — 
 
 Taurin ( = Amido-sethyl-sulphuric acid) = C 2 H,NSO s . 
 
 -\- Cholalic acid = C 24 H 40 O 5 . 
 
 = Taurocholic acid + Water .... = C 26 H 46 NSO, + H 2 {Strecker). 
 
 [Solutions of taurocholic acid are antiseptic, and if sufficiently strong interfere with the develop- 
 ment of bacteria, and prevent the alcoholic and lactic fermentations, as well as the tryptic and dias- 
 tatic action of the pancreas (Emich).~\ 
 
 Preparation of the Bile Acids — Bile is evaporated to )£ of its volume, rubbed up into a 
 paste with excess of animal charcoal, and dried at 100 C. The black mass is extracted with abso- 
 lute alcohol, which is filtered until it is clear. After a part of the alcohol has been removed by 
 distillation, the bile salts are precipitated in a resinous form, and on the addition of excess of ether 
 there is formed immediately a crystalline mass of glancing needles {Platner's " crystallized bile"). 
 The alkaline salts of the bile acids are freely soluble in water or alcohol, and insoluble in ether. 
 Neutral lead acetate precipitates the glycocholic acid — as lead glycocholate — from the solution of 
 both salts ; the precipitate is collected on a filter, dissolved in hot alcohol, and the lead is precipi- 
 tated as lead sulphide by H 2 S ; after removal of the lead sulphide, the addition of water precipitates 
 the isolated glycocholic acid. If, after precipitating the lead glycocholate, the filtrate be treated 
 with basic lead acetate, a precipitate of lead taurocholate is formed, from which the lead may be 
 obtained in the same way as described above (Strecker). 
 
 When human bile is similarly treated, instead of the " crystallized bile," a resinous non-crystal- 
 line precipitate is obtained. Boiling with baryta water isolates the cholalic acid from it, which is 
 obtained from its barium salt by adding hydrochloric acid. When dissolved in ether, it occurs in 
 the form of prismatic crystals if petroleum ether is added. The anthropocholic acid {C 1 8 H 2 8 4 
 — H. Bayer), so obtained is not soluble in water, but readily so in alcohol, and rotates the ray of 
 polarized light to the left. 
 
 With regard to the decomposition products of the bile acids, glycin, as 
 such, does not occur in the body, but only in the bile in combination with cholalic 
 
294 THE BILE ACIDS. 
 
 acid, in urine in combination with benzoic acid, as hippuric acid, and lastly, in 
 gelatin in complex combination. 
 
 Cholalic acid rotates the ray of polarized light to the right, and its chemical 
 composition is unknown ; perhaps it is to be regarded as benzoic acid, in which a 
 complex of atoms similar to oleic acid is introduced {Hoppe-Seylef). It occurs 
 free only in the intestine, where it is derived from the splitting up of taurocholic 
 acid, and it passes in part into the feces. It is insoluble in water, soluble in 
 alcohol, but soluble with difficulty in ether, from which it separates in prisms. 
 Its crystalline alkaline salts are readily soluble in water. 
 
 Cholalic acid is replaced in the bile of many animals by a nearly related acid, e. g., in pig's bile, 
 by hyo-cholalic acid (Strecker, Gundlach) ; in the bile of the goose, cheno-cholalic acid is present 
 (Marsson, Otto). 
 
 When cholalic acid is boiled with concentrated HC1, or dried at 200 C, it 
 becomes an anhydride, thus: — 
 
 Cholalic acid . . ■= C 24 H 40 O 5 , produces 
 
 Choloidinic acid . = C 2 _"' 
 
 Dyslysin . . . . = C 24 H:, 6 3 = H~ 2 0. 
 
 (Choloidinic acid is, however, improbably a mixture of cholalic acid and dyslysin; dyslysin, 
 when fused with caustic potash, is changed into cholalate of potash — Hoppe-Seyler). If anthro- 
 pocholic acid be heated to 185° C, it gives up 1 molecule of water, and yields anthropochol-dysly- 
 sin (Bayer). 
 
 By oxidation cholalic acid yields a tribasic acid, as yet uninvestigated, and a fair amount of 
 oxalic acid, but no fatty acids (Cleve). 
 
 Pettenkofer's Test. — The bile acids, cholalic acids, and their anhydrides, 
 when dissolved in water, yield on the addition of 2 /z concentrated sulphuric acid 
 (added in drops so as not to heat the fluid above fo° C), and several drops of a 
 10 per cent, solution of cane sugar, a reddish-purple transparent fluid, which 
 shows two absorption bands at E and F {Schenk). [A very good method is to 
 mix a few drops of the cane-sugar solution with the bile, and to shake the mix- 
 ture until a copious froth is obtained. Pour the sulphuric acid down the side of 
 the test tube, and then the characteristic color is seen in the froth. Any albumin 
 present must be removed before applying the test.] 
 
 According to Drechsel, it is better to add phosphoric acid, instead of sulphuric acid, until the fluid 
 is syrupy, then add the cane sugar, and afterward place the whole in boiling water. When investi- 
 gating the amount of bile acids in a liquid, the albumin must be removed beforehand, as it gives 
 a reaction similar to the bile acids, but in that case the red fluid has only one absorption band. If 
 only small quantities of bile acids are present, the fluid must in the first place be concentrated by 
 evaporation. 
 
 [Hay's Test for the Bile Acids. — This test depends on the fact, recently ascertained by 
 Matthew Hay in the course of an investigation which is not yet completed, that the bile acids or 
 their soluble salts have a remarkable lowering effect on the surface tension of fluids in which they 
 are dissolved. One part of glycoholic or taurocholic acid in 100,000 or 120,000 parts of water, per- 
 ceptibly lowers the surface tension of the water, and the lowering is very evident in a solution of 1 
 in 10,000. This lowering of the surface tension can, of course, be measured in the usual way by 
 means of a capillary tube. But Hay proposes, as a much more conven ent method, the throwing of 
 a small quantity of sulphur (sublimed or precipitated) on the surface of the fluid containing bile 
 acids. If the bile acids are present in greater proportion than I in 5000 or 10,000, the sulphur will 
 at once begin to sink, and will be wholly precipitated within one to two or three minutes. Precipi- 
 tation can even be observed, though it takes place much more slowly, in a solution of 1 in 120,000, 
 especially if the fluid is acidulated with a drop of a dilute mineral acid. Thrown on water, sulphur 
 does not sink, even after a week. No other substances in the body, except soaps, have the same 
 action as the bile acids — at least in anything like the same degree ; and soaps can be readily excluded 
 from the fluid under examination, either by precipitation with calcic or baric chloride or by decom- 
 position with a mineral acid, the earthy salts of the fatty acids, as also the liberated acids themselves, 
 being insoluble in water. Even outside the body, Hay has as yet found no substances, besides soaps, 
 which have the same powerful effect on the surface tension as the bile acids have. Hay has already 
 used the sulphur test with success for the detection of bile acids in urine. He attaches considerable 
 importance to this physical property of the bile acids in their role in digestion. — (Privately commu- 
 nicated).] 
 
THE BILE PIGMENTS. 295 
 
 The origin of the bile acids takes place within the liver. After its extirpa- 
 tion there is no accumulation of biliary matters in the blood (Joh. Mutter, Kunde, 
 Moleschotf). 
 
 How the formation of the nitrogenous bile acids is effected is quite unknown. They must be 
 obtained from the decomposition of albuminous materials, and it is important to note that the amount 
 of bile acids is increased by albuminous food. 
 
 Taurin contains part of the sulphur of albumin ; bile salts contain 4 to 4.6 per cent, of sulphur 
 (v. Voit), which may perhaps be derived from the stroma of the dissolved red blood corpuscles. 
 
 (3) The Bile Pigments. — The freshly secreted bile of man and many ani- 
 mals has a yellowish-brown color, due to the presence of bilirubin {Stadler). 
 When it remains for a considerable time in the gall bladder, or when alkaline bile 
 is exposed to the air, the bilirubin absorbs O and becomes changed into a green 
 pigment, biliverdin. This substance is present naturally, and is the chief pig- 
 ment in the bile of herbivora and cold-blooded animals. 
 
 (a) Bilirubin (C M H 36 N 4 6 ), is, according to Stadler and Maly, perhaps united 
 with an alkali ; it crystallizes in transparent fox-red clino-rhombic prisms. It is 
 insoluble in water, soluble in chloroform, by which substance it may be separated 
 from biliverdin, which is insoluble in chloroform. It unites as a monobasic acid 
 with alkalies, and as such is soluble. It is identical with Virchow's hsematoidin 
 (§ 20). 
 
 Preparation. — It is most easily prepared from the red (bilirubin chalk) gall stones of man or the 
 ox. The stones are pounded, and their chalk dissolved by hydrochloric acid ; the pigment is then 
 extracted with chloroform. 
 
 Source. — That bilirubin is derived from haemoglobin is very probable, considering its identity 
 with hsematoidin. Very probably red blood corpuscles are dissolved in the liver, and their haemo- 
 globin changed into bilirubin. 
 
 (b) Biliverdin {Heintz), d^^S^ii is simply an oxidized derivative of the 
 former, from which it can be obtained by various oxidation processes. It is readily 
 soluble in alcohol, very slightly so in ether, and not at all soluble in chloroform. 
 It occurs in considerable amount in the placenta of the bitch. As yet it has not 
 been retransformed by reducing agents into bilirubin. 
 
 Tests for Bile Pigments. — Bilirubin and biliverdin may occur in other 
 fluids, e. g., the urine, and are detected by the Gmelin- Heintz' reaction. 
 When nitric acid containing some nitrous acid is added to the liquid containing 
 these pigments, a play of colors is obtained, beginning with green (biliverdin), 
 blue, violet, red, ending with yellow. [This reaction is best done by placing a 
 drop of the liquid on a white porcelain plate, and adding a drop of the impure 
 nitric acid.] 
 
 (c) If when the blue color is reached, the oxidation process is arrested, bilicyanin (Heynsius, 
 Campbell), in acid solution blue (in alkaline violet), is obtained, which shows two ill-defined absorp- 
 tion bands near D (Jaffe). 
 
 (d) Bilifuscin occurs in small amount in decomposing bile and in gall stones = bilirubin 
 + H 2 0. 
 
 (e) Biliprasin (Stadler) als-> occurs = Bilirubin 4- H 2 -+- O. 
 
 (/) The yellow pigment, which results from the prolonged action of the oxidizing reagent, is the 
 choletelin (C 16 H 18 N,,O e ) of Maly; it is amorphous, and soluble in water, alcohol, acids, and 
 alkalies. 
 
 [Spectrum of Bile. — The bile of carnivorous animals is generally free from absorption bands, 
 except when acids are added to it, in which case the band of bilirubin is revealed. Bilirubin and 
 biliverdin yield characteristic spectra only when they are treated with nitric acid. The bile of some 
 animals yields bands, but when this is the case they are due to the presence of a derivative of 
 hsematin, and MacMunn calls this body Cholohaematin, which gives a three- or four-banded spec- 
 trum (ox, sheep).] 
 
 {g) Hydro-bilirubin. — Bilrubin absorbs H -\- H 2 (by putrefaction, or by the 
 treatment of alkaline watery solutions with the powerfully reducing sodium amal- 
 gam), and becomes converted into Maly's hydro-bilirubin (CjHuNiO,), which is 
 slightly soluble in water, and more easily soluble in solutions of salts, or alkalies, 
 
296 THE SECRETION OF BILE. 
 
 alcohol, ether, chloroform, and shows an absorption band at b, F. This substance, 
 which, according to Hammarsten, occurs in normal bile, is a constant coloring 
 matter of faeces, and was called stercobilin by Valulair and Masius, but is iden- 
 tical with hydro- bilirubin (Maly). It is, however, probably identical with the 
 urinary pigment urobilin of Jaffe {Stokvis, § 20). 
 
 [The bile of invertebrates contains none of the bile pigments present in vertebrates, although 
 hsemochromogen is found in the crayfish and pulmonate molluscs. In some organs, and in bile, a 
 pigment-like vegetable chlorophyll — entero-chlorophyll — is found, but whether it is derived from 
 without or formed within the organism, is not certain (MacMunn).'] 
 
 (4) Cholesterin, C 26 H„0(H 2 0), is an alcohol which rotates the ray of polar- 
 ized light to the left, and whose constitution is un- 
 
 ■lii* 4 " _ known ; it occurs also in blood, yelk, nervous matter 
 
 and [gall stones]. It forms transparent rhombic 
 plates, which, usually, have a small oblong piece cut 
 out of one corner (Figs. 184, and 144, d). It is 
 insoluble in water, soluble in hot alcohol, in ether 
 Crystals of ^oteterin, regularly and chloroform. It is kept in solution in the bile 
 
 by the bile salts. 
 
 Preparation..— It is most easily prepared from so-called white gall stones, which not unfrequently 
 consist almost entirely of cholesterin, by extracting them with hot alcohol after they are pulverized. 
 Crystals are excreted after evaporation of the alcohol. Tests. — They give a red color with sul- 
 phuric acid (5 vol. to 1 vol. H 2 0—MolescAoM), while they give a blue — as cellulose does — with 
 sulphuric acid and iodine. When dissolved in chloroform, one drop of concentrated sulphuric acid 
 causes a deep red color (H. Schiff). 
 
 (5) Among the other organic constituents of bile are : Lecithin (§ 23), or 
 its decomposition product, neurin (cholin), and glycero-phosphoric acid (into 
 which lecithin may be artificially transformed by boiling with baryta) ; Palmitin, 
 Stearin, Olein, as well as their soda soaps ; Diastatic Ferment (Jacobson, 
 v. WitticK); traces of Urea (JPicardy, (in ox bile, acetic acid and propionic acid, 
 united with glycerine and metals, Dogiel). 
 
 (6) Inorganic constituents of bile (0.6 to 1 per cent.) : — 
 
 They are — sodium chloride, potassium chloride, calcic and magnesic phosphate and much iron, 
 which in fresh bile gives the ordinary reactions for iron, so that iron must occur in one of its oxid- 
 ized compounds in the bile {Kunkel) ; manganese and silica. Gases. — Freshly secreted bile 
 contains in the dog more than 50 vol., and in the rabbit 109 vol. per cent. C0 2 [Pfliiger, Bogulju- 
 bow, Charles), partly united in alkalies, partly absorbed, the latter, however, being almost com- 
 pletely absorbed within the gall bladder. 
 
 The mean composition pf human bile is : — 
 
 Water 82 to 90 per cent. 
 
 Bile Salts 6 to 1 1 " 
 
 Fats and Soaps .... 2 " 
 
 Cholesterin 0.4 *' 
 
 Further, unchanged fat, probably, always passes into the bile, but is again absorbed therefrom 
 ( Virchow). The amount of S in dry dog's bile = 2.8 to 3.1 per cent., the N = 7 to 10 per cent. 
 \Spiro) ; the sulphur of the bile is not oxidized into sulphuric acid, but it appears as a sulphur 
 compound in the urine (Kunkel, v. Voil). 
 
 178. SECRETION OF BILE.— (1) The secretion of bile is not a 
 
 mere filtration of substances already existing in the blood of the liver, but it is a 
 chemical production of the characteristic biliary constituents, accompanied by 
 oxidation, within the hepatic cells, to which the blood of the gland only supplies 
 the raw material. The liver cells themselves undergo histological changes during 
 the process of digestion (Heidenhain, Kayser). It is secreted continually ; but 
 part is stored up in the gall bladder, and is poured out copiously during digestion. 
 The higher temperature of the blood of the hepatic vein, as well as the large 
 amount of C0 2 in the bile (Pfliiger), indicate that oxidations occur within the 
 liver. The water of the bile is not merely filtered through the blood capillaries, 
 as the pressure within the bile ducts may exceed that in the portal vein. 
 
 Lecithin 0.5 per cent. 
 
 Mucin 1 to 3 " 
 
 Ash 0.61 " 
 
CONDITIONS INFLUENCING THE SECRETION OF BILE. 297 
 
 (z) The quantity of bile was estimated by v. Wittich, from a biliary fistula, 
 at 533 cubic centimetres in twenty-four hours (some bile passed into the intestine) ; 
 by Westphalen, at 453 to 566 grm. [by Murchison, at 40 oz.] ; by Joh. Ranke, 
 on a biliary-pulmonary fistula, at 65 2 cubic centimetres. The last observation 
 gives 14 grm. (with 0.44 grm. solids) per kilo, of man in twenty hours. 
 
 Analogous values for animals are — I kilo, dog, 32 grm. (1.2 solids) — Kolliker, H. Mutter) ; 
 I kilo, rabbit, 137 grm. (2-5 solids); I kilo guinea pig, 176 grm. (5.2 solids) — {Bidder and 
 Schmidt). 
 
 (3) The excretion of bile into the intestines shows two maxima during one 
 period of digestion; the first, from three to five hours, and the second, from thir- 
 teen to fifteen hours after food. The cause is due to simultaneous reflex excite- 
 ment of the hepatic blood vessels, which become greatly dilated. 
 
 (4) The influence of food is very marked. The largest amount is secreted 
 after a flesh diet, with some fat added ; less after vegetable food ; a very small 
 amount with a pure fat diet ; it stops during hunger. Draughts of water increase 
 the amount, with a corresponding relative diminution of the solid constituents. 
 [The biliary solids are increased by food, reaching their maximum about one hour 
 after feeding]. 
 
 (5) The influence of blood supply is variable : — 
 
 [a) Secretion is greatly favored by a copious and rapid blood supply. The blood pressure is not 
 the prime factor, as ligature of the cava above the diaphragm, whereby the greatest blood pressure 
 occurs in the liver, arrests the secretion [Heidenhain). 
 
 [b) Simultaneous ligature of the hepatic artery (diameter, 5^ mm.) and the portal vein (diameter, 
 16 mm.) abolishes the secretion [Rohrig). These two vessels supply the raw material for the secre- 
 tion of bile. 
 
 (c) If the hepatic artery be ligatured, the portal vein alone supports the secretion [Simon, Sehiff, 
 Schmulewitsch, Asp). According to Kottmeier, Betz, Cohnheim, and Litten, ligature of the artery 
 or one of its branches ultimately causes necrosis of the parts supplied by that branch, and eventu- 
 ally of the entire liver, as this artery is the nutrient vessel of the liver. 
 
 (d) If the branch of the portal vein to the lobe be ligatured, there is only a slight secretion in 
 that lobe, so that the bile must be formed from the arterial blood [Schmulewitsch and Asp). Com- 
 plete ligature of the portal vein rapidly causes death. [The blood pressure falls rapidly and the 
 blood accumulates in the blood vessels of the abdomen. In fact, the accumulation of the blood 
 within the abdomen takes place to so great an extent, that practically the animal is bled into its 
 own abdomen (§ 87).] 
 
 Neither the ligature of the hepatic artery by itself [Sehiff, Bete), nor the gradual obliteration of 
 the portal vein by itself, causes the cessation of the secretion, but it is diminished. That sudden 
 ligature of the portal vein causes cessation is explained by the fact, that in addition to diminution of 
 the secretion, the enormous stagnation of blood in the rootlets of the portal vein in the abdominal 
 organs makes the liver very anaemic, and thus prevents it from secreting. 
 
 (1?) If the blood of the hepatic artery is allowed to pass into the portal vein (which has been liga- 
 tured on the peripheral side), secretion continues [Sehiff). 
 
 [/) Profuse loss of blood arrests the secretion of the bile, before the muscular and nervous appa- 
 ratus become paralyzed. A more copious supply of blood toother organs — e.g., to the muscles of 
 the trunk — during vigorous exercise, diminishes the secretion, while the transfusion of large quan- 
 tities of blood increases it [Landois) ; but if too high a pressure is caused in the portal vein, by 
 introducing blood from the carotid of another animal, it is diminished [Heidenhain). 
 
 [g) The Influence of Nerves. — All conditions which cause contraction of the abdominal 
 blood vessels, e.g., stimulation of the ansa Vieussenii, of the inferior cervical ganglion, of the hepatic 
 nerves [Afanassiew), of the splanchnics, of the spinal cord (either directly by strychnia, or reflexly 
 through stimulation of sensory nerves) affect the secretion ; and so do all conditions which cause 
 stagnation or congestion of the blood in the hepatic vessels (section of the splanchnic nerves, diabetic 
 puncture, \ 175), section of the cervical spinal cord [Heidenhain). Paralysis (ligature) of the 
 hepatic nerves causes at first an increase of the biliary secretion [Afanassiew). 
 
 [h) Portal and Hepatic Veins. — With regard to the raw material supplied to the liver by its 
 blood vessels, it is important to note the difference in the composition of the blood of the hepatic 
 and portal veins. The blood of the hepatic vein contains more sugar (?), lecithin, cholesterin 
 [Drosdoff), and blood corpuscles, but less albumin, fibrin, haemoglobin, fat, water, and salts. 
 
 [(«') Uffelmann observed that the flow of bile from a person with a biliary fistula was arrested 
 during fever.] 
 
 (6) The formation of bile is largely dependent upon the decomposition of 
 
298 
 
 EXCRETION OF BILE. 
 
 red blood corpuscles, as they supply the material necessary for the formation 
 of some of its constituents. 
 
 Hence, all conditions which cause solution of the colored blood corpuscles are accompanied by 
 an increased formation of bile (£ 1S0). 
 
 (7) Of course a normal condition of the hepatic cells is required for a normal 
 secretion of bile'. 
 
 Biliary Fistula:. — The mechanism of the biliary secretion is studied in animals by means of 
 biliary fistulse. Schwann opened the belly by a vertical incision a little to the right of the ensiform 
 process, cut into the fundus of the gall bladder, and sewed its margins to the edges of the wound in 
 the abdomen, and afterward introduced a cannula into the wound (Fig. 185). As a rule, all the 
 bile is discharged externally ; but to be quite certain that this is so, the common bile duct ought to 
 be tied between two ligatures, and divided. After a fistula is freshly made the secretion falls. This 
 depends upon the removal of the bile from the body. If bile be supplied the secretion is increased. 
 Regeneration of the divided bile duct may occur in dogs. v. Wittich observed a biliary fistula in 
 man. [A temporary biliary fistula may also be made. The abdomen is opened in the same way 
 as described above. A long, bent glass cannula is introduced and tied into the common bile duct, 
 and the cystic duct is ligatured or clamped (Fig. 185). The tube is brought out through the wound 
 in the abdomen. Necessarily all the bile must be discharged by the tube.] 
 
 [Influence of the Liver on Metabolism. — If the liver be excluded from the circulation, 
 remarkable changes must necessarily occur in the metabolism. In birds (the goose especially), 
 there is an anastomosis between the portal system of the liver and that of the kidneys, so that when 
 the portal circulation is interrupted in these animals, there is never any great congestion in the 
 abdominal organs. The goose dies generally eight to ten hours after the operation. The uric acid 
 
 Schwann's permanent fistula, and a temporary fistula. Aid, abdominal wall ; GB, gall bladder ; 
 INT, intestine, T, tube in temporary fistula {Stirling). 
 
 in the urine rapidly falls to a minimum (^ to ^ of normal) ; the chief constituent of the urine is 
 then sarcolactic acid, while in normal urine there is none ; the ammonia is increased {^Minkowski). 
 This experiment goes to indicate that uric acid is formed in the liver.] 
 
 [Dog. — If the liver be excluded from the portal circulation by connecting the portal vein with the 
 inferior vena cava, and ligaturing the hepatic artery, a dog will live, in the former case three to six 
 days and in the latter one to two. The liver does not undergo necrosis, nor does bile cease to be 
 secreted. The liver is nourished by the blood in the hepatic vein, the reflux in this vein being prob- 
 ably caused by the respiratory movements (S/olnikow). Noel Paton finds that in dogs, in a condi- 
 tion of nitrogenous balance, some drugs which increase the flow of bile {e.g., salicylate and benzoate 
 of soda, colchicum, perchloride of mercury, and euonymin), also increase the production of urea ; 
 hence, he concludes that the formation of urea in the liver bears a very direct relationship to the 
 secretion of bile (g 256).] 
 
 179. EXCRETION OF BILE.— In connection with the excretion of bile, 
 we must keep in view two distinct mechanisms. (1) The bile-secreting mech- 
 anism dependent upon the liver cells, which are always in a greater or less degree 
 of activity ; (2) the bile^expelling mechanism, which is specially active at cer- 
 tain periods of digestion (§ 178). 
 
 Excretion of Bile occurs — (1) owing to the continual pressure of the newly- 
 formed bile within the interlobular bile ducts forcing onward the bile in the ex- 
 cretory ducts. 
 
 (2) Owing to the interrupted periodic compression of the liver from above, by 
 
REABSORPTION OF BILE ; JAUNDICE. 299 
 
 the diaphragm, at every inspiration. Further, every inspiration assists the flow of 
 blood in the hepatic veins, and every respiratory increase of pressure within the 
 abdomen favors the current in the portal vein. 
 
 Tt is probable that the diminution of the secretion of bile, which occurs after bilateral division of 
 the vagi, is to be explained in this way ; still ,it is to be remembered, that the vagus sends branches 
 to the hepatic plexus. It is not decided whether the biliary excretion is diminished after section 
 of the phrenic nerves and paralysis of the abdominal muscles. 
 
 (3) Owing to the contraction of the smooth muscles of the larger bile ducts and 
 the gall-bladder. Stimulation of the spinal cord, from which the motor nerves 
 for these structures pass, causes acceleration of the outflow, which is afterward 
 followed by a diminished outflow (Heidenhain, J. Munk). Under normal condi- 
 tions, this stimulation seems to occur reflexly, and is caused by the passage of the 
 ingesta into the duodenum, which, at the same time, excites movement of this 
 part of the intestine. 
 
 (4) Direct stimulation of the liver (Pfluger), and reflex stimulation of the 
 spinal cord (Rohrig), diminish the excretion ; while extirpation of the hepatic 
 plexus (Pfluger), and injury to the floor of the fourth ventricle do not exert any 
 disturbing influence {Heidenhain). 
 
 (5) A relatively small amount of resistance causes bile to stagnate in the bile 
 ducts. 
 
 Secretion Pressure. — A manometer, tied into the gall-bladder of a guinea pig, supports a 
 column of 200 millimetres of water ; and secretion can take place under this pressure {Heidenhain, 
 Friedlander, Barisch). If this pressure be increased, or too long sustained, the watery bile passes 
 from the liver into the blood, even to the amount of four times the weight of the liver, thus caus- 
 ing solution of the red blood corpuscles by the absorbed bile ; and very soon thereafter haemoglobin 
 appears in the urine. [This fact is of practical importance, as duodenitis may give rise to symptoms 
 of jaundice, the resistance of the inflamed mucous membrane being sufficient to arrest the outflow 
 of bile.] 
 
 180. REABSORPTION OF BILE; JAUNDICE.— I. Absorption Jaundice.— When 
 an impediment or resistance is offered to the outflow of bile into the intestine, e. g., by a plug of 
 mucus, or a gall-stone which occludes the bile duct, or where a tumor or pressure from without 
 makes it impervious — the bile ducts become filled with bile and cause an enlargement of the liver. 
 The pressure within the bile ducts is increased. As soon as the pressure has reached a certain 
 amount, which it soon does when the bile duct is occluded (in the dog 275 mm. of a column of 
 bile— Afanassiew) — reabsorption of bile from the distended larger bile ducts takes place into the 
 lymphatics (not the blood vessels) of the liver [Saunders, 1795) ; the bile acids pass into the lym- 
 phatics of the liver. [The lymphatics can be seen at the portal fissure filled with a deep yellow- 
 colored lymph.] The lymph passes into the thoracic duct, and so into the blood (Fleischl, Kunkel, 
 Kufferalli \. Even when the pressure is very low within the portal vein, bile may pass into the 
 blood without any obstruction to the bile duct being present. This is the case in Icterus neona- 
 torum, as after ligature of the umbilical cord no more blood passes through the umbilical vein ; 
 further, in the icti-rus of hunger, " hunger jaundice " as the portal vein is relatively empty, owing 
 to the feeble absorption from the intestinal canal (CI. Bernard, Voit, Naunyn). 
 
 II. Cholaemia may also occur, owing to the excessive production of bile (hypercholia), the bile 
 not being all excreted into the inte-tlne, so that part of it is reabsorbed. This takes place when 
 there is solution of a great number of blood corpuscles (§ 178, 6), which yield material for the for- 
 mation of bile. Thick, inspissated bile accumulates in the bile ducts, so that stagnation, with sub- 
 sequent reabsorption of the bile, takes place (Afanassiew). The transfusion of heterogeneous 
 blood by dissolving colored blood corpuscles acts in this direction. Icterus is a common phe- 
 nomenon after too copious transfusion of the same blood. The blood corpuscles are dissolved by 
 the injection into the blood of heterogeneous blood serum (Landois) by the injection of bile acids 
 into the vessels (Frerichs), and by other salts, by phosphoric acid, water (Hermann), chloral, 
 inhalation of chloroform and ether (Nothnagel, Bernstein) ; the injection of dissolved haemoglobin 
 into the arteries (Kiihne), or into a loop of the small intestine, acts in the same way (Naunyn). 
 
 Icterus Neonatorum. — When, owing to compression of the placenta within the uterus, too 
 much blood is forced into the blood vessels of the newly-born infant, a part of the surplus blood 
 during the first few days becomes dissolved, part of the haemoglobin is converted into bilirubin, 
 thus causing jaundice ( Virchow, Violet). 
 
 Absorption Jaundice. — When the jaundice is caused by the absorption of 
 bile already formed in the liver, it is called hepatogenic or absorption jaundice, 
 The following are the symptoms: — 
 
300 INFLUENCE OF DRUGS ON THE SECRETION OF BILE. 
 
 Phenomena. — (i) Bile pigments and bile acids pass into the tissues of the body; hence, the 
 most pronounced external symptom is the yellowish tint or jaundice. The skin and the sclerotic 
 become deeply colored yellow. In pregnancy the foetus is also tinged. 
 
 (2) Bile pigments and bile acids pass into the urine (not into the saliva, tears or mucus), and 
 their presence is ascertained by the usual tests (g 177). When there is much bile pigment, the 
 urine is colored a deep yellowish-brown, and its froth is citron-yellow ; white strips of gelatin or 
 paper dipped into it also become colored. Occasionally bilirubin (= hsematoidin) crystals occur in 
 the urine ($ 266). 
 
 (3) The faeces are "clay-colored" (because the hydro-bilirubin of the bile is absent from the 
 fecal matter) — very hard (because the fluid of the bile does not pass into the intestine) ; contain 
 much fat (in globules and crystals), because the fat is not sufficiently digested in the intestine with- 
 out bile, so that more than 60 per cent, of the fat taken with the food reappears in the faces (v. 
 
 Voit) ; they have a very disagreeable odor, because bile normally greatly limits the putrefaction in 
 the intestine, [v. Voit finds that putrefaction does not take place if fats be withheld from the 
 food.] The aiacuation of the frees occurs slowly, partly owing to the hardness of the faeces, 
 partly because of the absence of the peristaltic movements of the intestine, owing to the want of 
 the stimulating action of the bile. 
 
 (4) The heart beats are generally diminished, e. g., to 40 per minute. This is due to the 
 action of the bile salts, which at first stimulate the cardiac ganglia, and then weaken them. The 
 injection of bile salts into the heart produces at first a temporary acceleration of the pulse (Lan- 
 dois), and afterward slowing (Rohrig). The same occurs when they are injected into the blood, 
 but in this case the stage of excitement is very short. The phenomenon is not affected by section 
 of the vagi. It is probable, that when the action of the bile salts ^s long continued they act upon 
 the heart muscle ( Traube). In addition to the action on the heart, there is slowing of the respi- 
 ration and diminution of temperature. 
 
 (5) That the nervous system, and perhaps also the muscles, are affected, either by the bile 
 salts or by the accumulation of cholesterin in the blood (Flint, K. Muller), is shown by the very 
 general relaxation, sensation of fatigue, weakness and drowsiness, lastly deep coma — sometimes 
 there is sleeplessness, itchiness of the skin, even mania, and spasms. Lowit, after injecting bile 
 into animals, observed phenomena referable to stimulation of the respiratory, cardio-inhibitory, and 
 vasomotor nerve centres. 
 
 (6) In very pronounced jaundice there may be "yellow vision " (Lucretius Carus), owing to the 
 impregnation of the retina and macula lutea with the bile pigment. 
 
 (7) The bile acids in the blood dissolve the red blood corpuscles. The haemoglobin is changed 
 into new bile pigment, and the globulin-like body of the haemoglobin may form urinary cylinders 
 or casts in the urinary tubules, which are ultimately washed out of the tubules by the urine (Noth- 
 nagel). 
 
 Passage of Substances into the Bile. — Various substances pass into the bile, such substances 
 being in the blood, viz., the metals (v. Sartoris, Mohnheim, Orfila) — copper, lead, zinc, nickel, 
 silver, bismuth (Wichert), arsenic, antimony, iron; these substances are also deposited in the 
 hepatic tissues. Potassium iodide, bromide, and sulphocyanide (Peiper), and turpentine also pass 
 into the bile, and, to a less degree, cane sugar and grape sugar (Mosler) ; sodium salicylate, and 
 carbolic acid (Peiper). If a large amount of water be injected into the blood, the bile becomes 
 albuminous (Mosler); mercuric and mercurous chlorides cause an increase of the water of the bile 
 (G. Scott). Sugar has been found in the bile in diabetes ; leucin and tyrosin in typhus, lactic acid 
 and albumin in other pathological conditions of this fluid. 
 
 [Influence of Drugs on the Secretion of Bile. — Two methods are adopted, one by means 
 of permanent fistulae, and the other by establishing temporary fistulas. The latter is the most satis- 
 factory method, and the experiments are usually made on fasting curarized dogs. A suitable cannula 
 is introduced into the common bile duct (Fig. 185), the animal is curarized, artificial respiration being 
 kept up, while the drug is injected into the stomach or intestine. Rohrig used this method, which 
 was improved by Rutherford and Vignal. Rohrig found that some purgatives, croton oil, colocynth, 
 jalap, aloes, rhubarb, senna, and other substances, increased the secretion of bile. Rutherford and 
 Vignal investigated the action of a large number of drugs on the bile-secreting mechanism. 
 They found that croton oil is a feeble hepatic stimulant, while podophyllin, aloes, colchicum, 
 euonymin, iridin, sanguinarin, ipecacuanha, colocynth, sodium phosphate, phytolaccin, sodium ben- 
 zoate, sodium salicylate, dilute nitrohydrochloric acid, ammonium phosphate, mercuric chloride (cor- 
 rosive sublimate), are all powerful, or very considerable, hepatic stimulants. They found that some 
 substances stimulate the intestinal glands, but not the liver, e. g., magnesium sulphate, castor oil, 
 gamboge, ammonium chloride, manganese sulphate, calomel. Other substances stimulate the liver 
 a< well as the intestinal glands, although not to the same extent, e. g., scammony (powerful intes- 
 tinal, feeble hepatic stimulant) ; colocynth excites both powerfully ; jalap, sodium sulphate, baptisin, 
 act with considerable power both on the liver and the intestinal glands. Calabar bean stimulates 
 the liver, and the increased secretion caused thereby may be reduced by sulphate of atropin, 
 although the latter drag, when given alone, does not notably affect the secretion of the bile. The 
 injection of water or bile slightly increases the secretion. In all cases where purgation was pro- 
 duced by purely intestinal stimulants, such as magnesium sulphate, gamboge, and castor oil, the 
 
FUNCTIONS OF THE BILE. 301 
 
 secretion of bile was diminished. In all such experiments it is most important that the temperature 
 of the animal be kept up by covering it with cotton wool, else the secretion of bile diminishes. 
 Paschkis's results on dogs differ considerably from those of Rutherford. He asserts that only the bile 
 acids (salts), of all the substances he investigated, excite a prompt and distinct cholagogue action.] 
 
 [As yet we cannot say definitely whether these substances stimulate the secretion of bile, by ex- . 
 citing the mucous membrane of the duodenum or other part of the small intestine, and thereby 
 inducing reflex excitement of the liver. Their action does not seem to be due to increase of the 
 blood stream through the liver. More probably, as Rutherford suggests, these drugs act directly on 
 the hepatic cells or their nerves. Acetate of lead directly depresses the biliary secretion, while some 
 substances affect it indirectly.] 
 
 Cholesteraemia. — Flint ascribes great importance to the excretion of cholesterin by the bile, 
 with reference to the metabolism of the nervous system. Cholesterin, which is a normal ingredient 
 of nervous tissue, is excreted by the bile ; and if it be retained in the blood " cholesteraemia," with 
 grave nervous symptoms, is said to occur. This, however, is problematical, and the phenomena 
 described are probably referable to the retention of the bile acids in the blood. 
 
 181. FUNCTIONS OF THE BILE.— [(i) Bile is concerned in the 
 digestion of certain food-stuffs; (2) part of it is absorbed; (3) part is excreted.] 
 
 (A) Bile plays an important part in the absorption of fats : — 
 
 (1) It emulsionizes neutral fats (§ 170, III), whereby the fatty granules pass 
 more readily through or between the cylindrical epithelium of the small intestine 
 into the lacteals. It does not decompose neutral fats into glycerine and a fatty 
 acid, as the pancreas does. 
 
 When, however, fatty acids are dissolved in -the bile (Lenz) the bile salts are decomposed, the 
 bile acids being set free, while the soda of the decomposed bile salts readily forms a soluble soap 
 with the fatty acids. These soaps are soluble in the bile, and increase considerably the emulsifying 
 power of this fluid. Bile can dissolve directly fatty acids to form an acid fluid, which has high 
 emulsionizing properties (Steiner). Emulsification is influenced by a 1 per cent solution of NaCl, or 
 Na 2 S0 4 {P/eiffer). 
 
 (2) As fluid fat flows more rapidly through capillary tubes when they are mois- 
 tened with bile, it is concluded that when the pores of the absorbing wall of the 
 small intestine are moistened with bile, the fatty particles pass more easily through 
 them. 
 
 (3) Filtration of fat takes place through a membrane moistened with bile or 
 bile salts under less pressure than when it is moistened with water or salt solutions 
 (v. Wistinghausen). 
 
 (4) As bile, like a solution of soap, has a certain relation to watery solutions, 
 as well as to fats, it permits effusion to take place between these two fluids, as the 
 membrane is moistened by both fluids (v. Wistinghausen^. 
 
 It is clear, therefore, that the bile is of great importance in the preparation and in the absorption of 
 fats. This is forcibly illustrated by experiments on animals, in which the bile is entirely discharged 
 externally through a fistula. Dogs under these conditions, absorbed at most 40 per cent, of the fat 
 taken with the food [60 per cent, being given off by the faeces, while a normal dog absorbs 99 per 
 cent, of the fat. The digestion of flesh and gelatine is not interfered with in dogs by the removal 
 of the bile (v. Voit).'] The chyle of such animals is very poor in fat, is not white, but transparent ; 
 the faeces, however, contain much fat, and are oily. Such animals are voracious (Nasse) ; the tissues 
 of the body contain little fat, even when the nutrition of the animals has not been much interfered 
 with. Persons suffering from disturbances of the biliary secretion, or from liver affections, ought, 
 therefore, to abstain from fatty food. 
 
 (B) Fresh bile contains a diastatic ferment which transforms starch into 
 sugar {Nasse, Jacobson, v. Wittich), and also glycogen into sugar {Bufalini'). 
 
 (C) Bile excites contractions of the muscular coats of the intestine, and 
 contributes thereby to absorption. 
 
 (1) The bile acids act as a stimulus to the muscles of the villi, which contract from time to 
 time, so that the contents of the lymph spaces [origins of the lacteals] are emptied toward the larger 
 lymphatics, and the villi are thus in a position to absorb more (Setoff). [The villi act like numerous 
 small pumps, and expel their contents, which are prevented from returning by the presence of valves 
 in the larger lymphatics.] 
 
 (2) The musculature of the intestine itself seems to be excited, perhaps through the agency 
 of the plexus myentericus. In animals with a biliary fistula, and in which the bile duct is obstructed, 
 
302 FATE OF THE BILE IN THE INTESTINE. 
 
 the intestinal peristalsis is greatly diminished, while the salts of the bile acids administered by the 
 mouth cause diarrhoea and vomiting (Leyden, Schiilein). As contraction of the intestine aids absorp- 
 tion, bile is also necessary, in this way, for the absorption of the dissolved food stuffs. 
 
 (D) The presence of bile seems to be necessary to the vital activity of the in- 
 testinal epithelium in its supposed function of being concerned in the absorption 
 of fatty particles (v. Thanhoffer, Rohmann). Compare (§ 190). 
 
 (E) The bile moistens the walls of the intestine, as it is copiously excreted. 
 It gives to the faeces their normal amount of water, so that they can be readily 
 evacuated. Animals with biliary fistula, or persons with obstruction of the bile 
 ducts, are very costive. The mucus of the bile aids the forward movement of the 
 ingesta through the intestinal canal. [Thus, in a certain sense, bile is a natural 
 purgative.] 
 
 (F) The bile diminishes putrefactive decomposition of the intestinal con- 
 tents {Bidder and Schmidt), especially with a fatty diet {Rohmann, v. Voif), § 190. 
 [Thus, it is an antiseptic, although this is doubted by v. Voit, p. 300).] 
 
 (G) When the strongly acid contents of the stomach pass into the duodenum, 
 the glycocholic acid is precipitated by the gastric acid, and carries the pepsin 
 with it (Burkart). Some of the albumin, which has been simply dissolved, but 
 as yet not peptonized, is also precipitated, but it does not seem that peptone or 
 propeptone are precipitated by the mixture of the bile acids QMaly and EmicK). 
 The bile salts are decomposed by the action of the gastric juice. When the mix- 
 ture is rendered alkaline by the pancreatic juice and the alkali derived from the 
 decomposition of the bile salts, the pancreatic juice acts energetically in this alka- 
 line medium {Moleschott). 
 
 [Taurocholic acid and its soda salts precipitate albumin, but not peptone ; glycocholic acid does 
 not precipitate albumin, so that in the intestine the peptone is separated from the albumin (and syn- 
 tonin), and may, therefore, be more readily absorbed, while the precipitate adhering to the intestinal 
 wall can be further digested (Maly and EmicK). Taurocholic acid behaves in the same way toward 
 gelatine peptone.] 
 
 Bilious Vomit. — When bile passes into the stomach, as in vomiting, the acid of the gastric juice 
 unites with the bases of the bile salts ; so that sodium chloride and free bile acids are formed, and 
 the acid reaction is thereby somewhat diminished. The bile acids are not effective for carrying on 
 gastric digestion; the neutralization also causes a precipitation of the pepsin and mucin. As soon, 
 however, as the walls of the stomach secrete new acid, the pepsin is redissolved. The bile which 
 passes into the stomach deranges gastric digestion, by shriveling the proteids, which can only be 
 peptonized when they are swollen up. 
 
 182. FATE OF THE BILE IN THE INTESTINE.— Some of the 
 
 biliary constituents are completely evacuated with the faeces, while others are re- 
 absorbed by the intestinal walls. 
 
 (1) Mucin passes unchanged into the faeces. 
 
 (2) The bile pigments are reduced, and are partly excreted with the faeces 
 as hydro-bilirubin (§ 177, 3 g), and partly as the identical end product, urobilin, by 
 the urine. 
 
 From Meconium hydro-bilirubin is absent, while crystalline bilirubin and biliverdin and an 
 unknown red oxidation product of it are present [bile acids, even taurocholic, and small traces of 
 fatty acids], (Zweifel). [So that it gives Gmelin's reaction.] Hence, no reduction — but rather 
 oxidation — processes occur in the foetal intestine (Hoppe-Seyler). 
 
 (Composition.— Dary gives 72.7 per cent, water, 23.6 mucus and epithelium, 1 per cent, fat and 
 cholesterin, and 3 per cent, bile pigments. Zweifel gives 79.78 per cent, water, and solids 20.22 
 per cent. It does not contain lecithin, but so much bilirubin that Hoppe-Seyler uses it as a good 
 source whence to obtain this pigment. It gives a spectrum of a body related to urobilin ( Vaulair, 
 MacMunn).'] 
 
 (3) Cholesterin is given off with the faeces. 
 
 (4) The bile salts are, for the most part, reabsorbed by the walls of the jeju- 
 num and ileum, to be reemployed in the animal's economy. Tappeiner found 
 them in the chyle of the thoracic duct ; minute quantities pass normally from the 
 blood into the urine. Only a very small amount of glycocholic acid appears 
 
THE INTESTINAL JUICE. 303 
 
 unchanged in the faeces. The taurocholic acid, as far as it is not absorbed, is 
 easily decomposed in the intestine, by the putrefactive processes, into cholalic 
 acid and taurin ; the former of these is found in the fasces, but the taurin, at least, 
 seems not to be constantly present. Part of the cholalic acid is absorbed, and 
 may unite in the liver either with glycin or taurin ( Weiss). 
 
 As putrefactive decomposition does not occur in the foetal intestine, unchanged taurocholic acid is 
 found in meconium {Zweifel). The anhydride stage of cholalic acid (the artificially-prepared 
 choloidinic acid?), dyslysin, is an artificial product, and does not occur in the faeces {ttoppe- 
 Seyler). 
 
 (5) The faeces contain mere traces of Lecithin ( Wegscheider, Bokay). 
 
 Impaired Nutrition. — The greatest part of the most important biliary constituents, the bile acids, 
 re-enter the blood, and thus is explained why animals with a biliary fistula, where all the bile is re- 
 moved (without the animal being allowed to lick the bile), rapidly lose weight. This depends 
 partly upon the digestion of the fats being interfered with, and also upon the direct loss of the bile 
 salts. If such dogs are to maintain their weight, they must eat twice as much food. In such cases, 
 carbohydrates most beneficially replace the fats. If the digestive apparatus is otherwise intact, the 
 animals, on account of their voracity, may even increase in weight, but the flesh and not the iat is 
 increased. 
 
 Bile partly an Excretion. — The fact that bile is secreted during the foetal 
 period, while none of the other digestive fluids are, proves it is an excretion. 
 
 The cholalic acid which is reabsorbed by the intestinal walls passes into the body, and seems 
 ultimately to be burned to form C0 2 and H 2 0. The glycin (with hippuric acid) forms urea, as the 
 urea is increased after the injection of glycin (fforsford, Schultzen, Nencki). The fate of taurin is 
 unknown. When large quantities are introduced into the human stomach, it reappears in the urine, 
 as tauro-carbamic acid, along with a small quantity of unchanged taurin. When injected subcuta- 
 neously into a rabbit, nearly all of it reappears in the urine. 
 
 [Practical. — In practice it is important to remember that bile once in the intestine is liable to 
 be absorbed unless it be carried down the intestine ; hence, it is one thing to give a drug which will 
 excite the secretion of bile, i. e., a hepatic stimulant, and another to have the bile so secreted ex- 
 pelled. It is wise, therefore, to give a drug which will do both, or at least to combine a hepatic 
 stimulant with one which will stimulate the musculature of the intestine as well. Active exercise, 
 whereby the diaphragm is vigorously called into action to compress the liver, will aid in the ex- 
 pulsion of the bile from the liver [Brunton).] 
 
 183. THE INTESTINAL JUICE.— Length of Intestine.— The human intestine is ten 
 times longer than the length of the body, as measured from the vertex to the anus. It is longer 
 comparatively than that of the omnivora [ffenning). Its minimum length is 507, its maximum 
 1 149 centimetres [17 to 35 feet]; its capacity is relatively greater in children (Beneke). [The 
 average length is 30 feet; 25 feet (small), and 5 to 6 feet large intestine.] In childhood the ab- 
 sorptive elements, in adults the secreto-chemical processes, appear to be most active (Baginsky). 
 
 The succus entericus is the digestive fluid secreted by the numerous glands 
 of the intestinal mucous membrane. The largest amount is produced by Lieber- 
 kiihn's glands, while in the duodenum there is added the scanty secretion of the 
 small compound Brunner's glands. 
 
 Brunner's glands are small, convoluted, branched, tubular glands, lying in the sub-mucosa of 
 the duodenum. Their fine ducts run inward, pierce the mucous membrane, and open at the bases 
 of the villi. The acini are lined by cylindrical cells, like those lining the pyloric glands. In fact, 
 Brunner's glands are structurally and anatomically identical with the pyloric glands of the stomach. 
 During hunger, the cells are turbid and small, while during digestion they are large and clear. 
 The glands receive nerve fibres from Meissner's plexus {Drasck). 
 
 I. The Secretion of Brunner's Glands. — The granular contents of the 
 secretory cells of these glands, which occur singly in man, but form a continuous 
 layer in the duodenum of the sheep, besides albuminous substances, consist'of 
 mucin and a ferment substance of unknown constitution. The watery extract of 
 the glands causes — (1) Solution of proteids at the temperature of the body 
 (Krolow). (2) It also has a diastatic (?) action. It does not appear to act upon 
 fats. [Brown and Heron have shown that the secretion of Brunner's glands, 
 more actively than any other glands of the intestines, converts maltose into 
 glucose.] 
 
304 
 
 lieberkUhn's glands. 
 
 On account of the smallness of the objects, such experiments are only made with great difficulty, 
 and, therefore, there is a considerable uncertainty with regard to the action of the secretion. 
 
 Lieb erkhun's glands are simply tubular glands resembling the ringer of a glove [or a test-tube] , 
 which lie closely packed, vertically near each other, in the mucous membrane (Fig. 186) ; they are 
 most numerous in the large intestine, owing to the absence of the villi in this region. They consist 
 of a structureless membrana propria lined by a layer of low cylindrical epithelium, between which 
 numerous goblet cells occur, the goblet cells being fewer in the small intestine and much more 
 numerous in the large (Fig. 201). The glands of the small intestine yield a thin secretion, while 
 those of the large intestine yield a large amount of sticky mucus from their goblet cells (Klose and 
 Heidenhain). [In a vertical section of the small intestine they lie at the base of villi (Fig. 186). 
 In transverse section they are shown in Fig. 187.] 
 
 II. The Secretion of Lieberkiihn's Glands, from the duodenum onward, 
 is the chief source of the intestinal juice. 
 
 Fig. 186. 
 
 Villi with epitbelium. 
 
 Lieberkiihn's glands. 
 Muscularis mucosae 
 
 Peyer's patch. 
 
 £- Circular muscle. 
 
 gg Longitudinal muscle. 
 
 Longitudinal section of the small intestine of a dog, through a Peyer's patch. 
 
 Intestinal Fistula. — The intestinal juice is obtained by making a Thiry's Fistula (1864). A 
 loop of the intestine of a dog is pulled forward (Fig. 188, 1), and a piece about 4 inches in length 
 is cut out, so that the continuity of the intestinal tube is broken, but the mesentery and its blood ves- 
 sels are not divided. One end of this tube is closed, and the other end is left open and stitched to 
 the abdominal wall (Fig. 188, 3). After the two ends of the intestine from which this piece was 
 taken have been carefully brought together with sutures , so as to establish the continuity of the 
 intestinal canal, animals still continue to live (Fig. 188, 2). The excised piece of intestine yields 
 a secretion which is uncontaminated with any other digestive secretion. [Thiry's method is very 
 unsatisfactory, as judged from the action of the separated loop in relation to medicaments, probably 
 owing to its mucous membrane becoming atrophied from disuse, or injured by inflammation.] 
 
ACTIONS OF THE INTESTINAL JUICE. 
 
 305 
 
 [Meade Smith has lately used a better method, in which he makes a small opening in the intes- 
 tine, through which he introduces two small, hollow and collapsed India-rubber balls, one above and 
 the other below the opening, which are then distended by inflation until they completely block a 
 certain length of the intestine. The loop thus blocked off having been previously well washed out, is 
 allowed to become filled with succus, which is secreted on the application of various stimuli. By means 
 of Bernard's gastric cannula ((I 165) inserted into the fistula in the loop, the secretion can be re- 
 moved when desired.] 
 
 [Vella's Fistula. — Open the belly of a dog, and pull out a loop (30 to 50 ctm.) [1 to 1^ feet] 
 of small intestine and ligature it ; dividing it above and below, re-establish the continuity of the 
 rest of the intestine. Stitch both ends of the loop of intestine into the wound in the linea alba 
 (Fig. 188, 4) so that there is a loop of intestine supplied by its blood vessels and nerves, isolated and 
 with an upper and lower aperture.] 
 
 Fig. 187. 
 
 Crypt. 
 
 Glandular epithelium. 
 
 'Blood vessel. 
 
 Cavity of the gland. ■ — 
 
 Transverse section of Lieberkiihn's follicles. 
 
 The intestinal juice of such fistulae flows spontaneously in very small amount, 
 and is increased during digestion ; it is increased — especially its mucus — by me- 
 chanical, chemical, and electrical stimuli ; at the same time, the mucous mem- 
 brane becomes red, so that 100 centimetres yield 13 to 18 grammes of this juice 
 in an hour ( Thiry, Masloff). 
 
 Characters. — The juice is light yellow, opalescent, thin, strongly alkaline, 
 specific gravity ion, evolves COi when an acid is added; it contains albumin 
 and ferments ; mucin occurs in the juice of the large intestine. Its composition 
 is — proteids = 0.80 per cent.; other organic substances = 0.73 per cent. ; salts, 
 0.88 per cent. ; among these — sodium carbonate, 0.32 to 0.34 per cent. ; water, 
 
 07.50 per cent. 
 
 y/ " V Fig. 188. 
 
 Scheme of Thiry's fistula 1,2,3. 4« Vella's fistula. A A' are stitched together ; 
 Abd. Abdominal wall {Stirling). 
 
 [The intestinal juice obtained by Meade Smith's method contained only 0.39 per cent, of organic 
 matter, and in this respect agreed closely with the juice which A. Moreau procured by dividing the 
 mesenteric nerves of a ligatured loop of intestine. The secretion of the large intestine is much 
 more viscid than that of the small intestine.] 
 
 Actions of Succus Entericus. — The digestive functions of the fluid of the 
 small intestine are — 
 
 (1) It has less diastatic action than either the saliva or the pancreatic juice 
 {Schiff, Busch, Quincke, Garland*), but it does not form maltose ; while the juice 
 of the large intestine is said to possess this property (Eichhorsf). v. Wittich ex- 
 tracted the ferment with a mixture of glycerine and water. 
 20 
 
306 ACTIONS OF THE INTESTINAL JUICE. 
 
 [The diastatic action of the small intestine is incomparably weaker than that of the saliva, or pan- 
 creatic juice, and barely exceeds that of the tissues and fluids of the bodies generally. A similarly 
 weak diastatic action is possessed by the secretion of the colon.] 
 
 (2) It converts maltose into grape sugar. It seems, therefore, to continue the 
 diastatic action of the saliva (§ 148) and pancreatic juice (§ 170) which usually 
 form only maltose. Thus maltose seems to be transformed into grape sugar by 
 the intestinal juice. 
 
 According to Bourquelot this action is due to the intestinal schizomycetes and not to the intestinal 
 juice as such, the saliva, the gastric juice, or invertin. The greater part of the maltose appears, 
 however, to be absorbed unchanged. 
 
 (3) Fibrin is slowly (by the trypsin and pepsin — Kiihne) peptonized {Thiry, 
 Leube) ; less easily albumin {Mas/off), fresh, casein, flesh, raw or cooked, vege- 
 table albumin {K'dlliker, Schiff) ; probably gelatin is also changed by a special 
 ferment into a solution which does not gelatinize {Eichhorsf). 
 
 [The ferment for this purpose is mainly contained in Brunner's glands, and in Peyer's patches 
 {Brown and Heron). ~\ 
 
 (4) Fats are only partly emulsionized {Schiff), and afterward decomposed 
 (Velld). 
 
 [M. Hay has never observed any emulsifying action. The appaient emulsification in certain 
 instances is due to shaking the alkaline juice with a rancid oil, containing free fatty acids, when a 
 certain quantity of a soap is at once formed.] 
 
 (5) According to CI. Bernard, invertin occurs in intestinal juice (this ferment 
 can also be extracted from yeast), whereby cane sugar (C, 2 H ra O u ) takes up water 
 (-(- H 2 0) and becomes converted into invert sugar, which is a mixture of left 
 rotating sugar (lsevulose, C 6 H 12 6 ) and of grape sugar (dextrose, C 6 H 12 6 ). Heat 
 seems to be absorbed during the process {Leube). (See Carbohydrates, § 252, for 
 the various kinds of sugar.) 
 
 [Hoppe-Seyler has suggested that this ferment is not a natural product of the body, but is intro- 
 duced from without with the food. Matthew Hay has recently disproved this theory by, among 
 other reasons, finding it to be invariably present in the intestine of the fcetus. It is found in every 
 portion of the small intestine, but not in the large intestine, nor in any other part of the body, and 
 is much less diffusible than diastase.] 
 
 [Effect of Drugs. — The subcutaneous injection of pilocarpin causes the mucous membrane of a 
 Vella's fistula {dog) to be congested, when a strongly alkaline, opalescent, watery, and slightly albu- 
 minous secretion is obtained. This secretion produces a reducing sugar, converts cane sugar into 
 invert sugar, emulsifies neutral fats, ultimately splitting them up, peptonizes proteids, and coagulates 
 milk, even although alkaline. The juice attacks the sarcous substance of muscle before the con- 
 nective tissues — the reverse of the gastric juice. The mucous membrane' in a Vella's fistula does 
 not atrophy. K. B. Lehmann finds that the succus entericus obtained from the intestine of a goat 
 by a Thiry-Vella fistula has no digestive action ( Vella).~\ 
 
 [Fate of the Ferments. — With regard to the digestive ferments, Langley is of opinion that 
 they ar&destroyed in the intestinal canal ; the diastatic ferment of saliva is destroyed by the free HC1 
 of the gastric juice ; pepsin and rennet are acted upon by the alka- 
 line salts of the pancreatic and intestinal juices, and by trypsin ; while 
 the diastatic and peptic ferments of the pancreas disappear under the 
 influence of the acid fermentation in the large intestine.] 
 
 The Action of the Nervous System on the secretion of the in- 
 testinal juice is not well determined. Section or stimulation of the 
 vagi has no apparent effect ; while extirpation of the large sympathetic 
 abdominal ganglia causes the intestinal canal to be filled with a watery 
 fluid, and gives rise to diarrhoea {Budge). This may be explained by 
 the paralysis of the vasomotor nerves, and also by the section of large 
 lymphatic vessels during the operation, whereby absorption is inter- 
 fered with and transudation is favored. 
 Scheme of Moreau's experiment Moreau's Experiment. — A similar result is caused by extirpation 
 {Stirling). of the nerves which accompany the blood vessels going to a loop of 
 
 intestine {Moreau), the blood vessels themselves being intact. [Moreau 
 placed four ligatures on a loop of intestine at equal distances from each other (Fig. 189). The liga- 
 tures were tied so that three loops of intestine were shut off. The nerves (N) to the middle loop 
 
FUNGI AS EXCITERS OF FERMENTATION. 
 
 307 
 
 were divided, and the intestine was replaced in the abdominal cavity. After a time, a very small 
 amount of secretion, or none at all, was found in two of the ligatured compartments of the gut, 
 i. e., in those with the nerves and blood vessels intact (1,3), but the compartment (2) whose nerves 
 had been divided contained a watery secretion. Perhaps the secretion which occurs after section of 
 the mesenteric nerves is a paralytic secretion.] 
 
 The secretion of the intestinal and gastric juices is diminished in man in certain nervous affec- 
 tions (hysteria, hypochondriasis, and various cerebral diseases) ; while in other conditions these 
 secretions are increased. 
 
 Excretion of Drugs. — If an isolated intestinal fistula be made, and various drugs administered, 
 experiment shows that the mucous membrane excretes iodine, bromine, lithium, sulphocyanides, but 
 not potassium ferrocyanide, arsenious or boracic acid (Quincke), or iron salts (Glaevecke). 
 
 In sucklings, not unfrequently a large amount of acid is formed when the fungi in the intestine 
 split up milk sugar or grape sugar into lactic acid (Leube). Starch changed into grape sugar may 
 undergo the same abnormal process; hence, infants ought not to be fed with starchy food. 
 
 184. FERMENTATION PROCESSES IN THE INTESTINE. 
 
 — Those processes which are to be regarded as fermentations or putrefactive pro- 
 cesses, are quite different from those caused by the action of distinct ferments 
 (Frerichs, Hoppe-Seyler). The putrefactive changes are connected with the 
 presence of lower organisms, so-called fermentation or putrefaction producers 
 (Nencki) : and they may develop in suitable media outside the body. The lower 
 organisms which cause the intestinal fermentation are swallowed with the food and 
 the drink, and also with the saliva. When they are introduced, fermentation and 
 putrefaction begin, and gases are evolved. 
 
 Intestinal Gases. — During the whole of the foetal period, until birth, this 
 fermentation cannot occur ; hence, gases are never present in the intestine of the 
 newly born (Breslau). The first air bubbles pass into the intestine with the saliva 
 which is swallowed, even before food has been taken. The germs of organisms 
 are thus introduced into the intestinal tract, and give rise to the formation of gases. 
 The evolution of intestinal gases goes hand-in-hand with the fermentations. At- 
 mospheric air is also swallowed, and an exchange of gases takes place in the intes- 
 tine, so that the composition of the intestinal gases depends upon various condi- 
 tions. 
 
 Kolbe and Ruge collected the gases from the anus of a man, and found in 100 
 vols. — 
 
 Food. 
 
 CO„. 
 
 H. 
 
 CH 4 . 
 
 N. 
 
 H 2 S. 
 
 Milk, 
 
 Flesh, 
 
 Peas, 
 
 16.8 
 12.4 
 21.0 
 
 43-3 
 2.1 
 4.0 
 
 0.9 
 
 27.5 
 
 55-9 
 
 38-3 
 
 57-8 
 18.9 
 
 Quantity 
 not estimated. 
 
 With regard to the formation of gas and the processes of fermentation, we 
 note — 
 
 1. Air bubbles are swallowed when the food is taken. The O thereof is 
 rapidly absorbed by the walls of the intestinal tract, so that in the lower part of 
 the large intestine, even traces of O are absent. In exchange, the blood vessels 
 in the intestinal wall give off C0 2 into the intestine, so that a part of the C0 2 in 
 the intestine is derived by diffusion from the blood. 
 
 2. H and C0 2 ,NH 3 , and CH 4 are also formed from the intestinal contents by 
 fermentation, which takes place even in the small intestine [Planer), 
 
 Fungi as Exciters of Fermentation. — The chief agents in the production of fermentations, 
 putrefaction, and other similar decompositions are undoubtedly the group of the fungi called 
 Schizomycetes. They are small unicellular organisms of various forms, globular (Micrococcus), 
 short rods (Bacterium), long rods (Bacillus), or spiral threads ( Vibrio, Spirillum, Spirochceta, Fig. 
 20). The mode of reproduction is by division, and they may either remain single or unite to form 
 colonies. Each organism is usually capable of some degree of motion. They produce profound 
 chemical changes in the fluids or media in which they grow and multiply, and these changes depend 
 
308 
 
 FERMENTATION OF THE CARBOHYDRATES. 
 
 upon the vital activity of their protoplasm. These minute microscopic organisms take certain con- 
 stituents from the " nutrient fluids " in which they live, and use them partly for building up their 
 own tissues and partly for their own metabolism. In these processes, some of the substances so 
 absorbed and assimilated undergo chemical changes, some ferments seem thereby to be produced, 
 which in their turn may act upon material present in the nutritive fluid. 
 
 These fungi consist of a capsule or envelope enclosing protoplasmic contents. Many of them 
 are provided with excessively delicate cilia, by means of which they move about. The new organ- 
 isms produced by the division of pre-existing ones, sometimes form large colonies visible to the 
 naked eye,. the individual fungi being united by a jelly-like mass, the whole constituting zoogloea 
 In some fungi, reproduction takes place by spores ; more especially when the nutrient fluids are 
 poor in nutritive materials. The bacteria form longer rods or threads which are jointed, and in 
 each joint or segment small (1-2 p.) highly refractive globules or spores are developed (Fig. 191, 7). 
 In some cases, as in the butyric acid fermentation, the rods become fusiform before spores are 
 formed. When the envelope of the mother cell is ruptured or destroyed, the spores are liberated, 
 and if they fall upon or into a suitable medium, they germinate and reproduce organisms similar to 
 those from which they sprung. The process of spore production is illustrated in Fig. 190, 7, 8, 9, 
 and in 1, 2, 3, 4 is shown the process of germination in the butyric acid fungus. The spores are 
 very tenacious of life ; they may be dried, when they resist death for a very long time ; some of 
 them are killed by being boiled. Some fungi exhibit their vital activities only in the presence of O 
 (Aerobes), while others require the exclusion of O (Anaerobes, Pasteur). According to the 
 products of their action, they are classified as follows: Those that produce fermentations (zymo- 
 
 V 
 
 Fig. 190. 
 
 a 
 
 3 %# 
 
 % 1 
 
 t 
 
 S4 
 
 >» 
 
 , Bacterium aceti. in the form of— cocci (1) ; diplococci (2) : short rods (3), and jointed threads (4, 5). B, Bacil- 
 lus butyricus — (1) isolated spores ; (2,3, 4) germinating condition of the spores ; (5, 6) short and long rods ; (7, 
 8, 9) formation of spores within a cellular fungus. 
 
 genie schizomycetes) ; those that produce pigments (chromogenic) ; those that produce disagreeable 
 odors, as during putrefaction (bromogenic) ; and those that, when introduced into the living tissues 
 of other organisms, produce pathological conditions, and even death (pathogenic). All these differ- 
 ent kinds occur in the human body. 
 
 When we consider that numerous fungi are introduced into the intestinal canal with the food and 
 drink— that the temperature and other conditions within this tube are specially favorable for their 
 development ; that there also they meet with sufficient pabulum for their development and repro- 
 duction—we cannot wonder that a rich crop of these organisms is met with in the intestine, and 
 that they produce there numerous fermentations. 
 
 I. Fermentation of the Carbohydrates.— (i) Bacterium lacticum 
 
 (Cohn), (Ferment lactique, Pasteur) are biscuit-shaped cells, 1.5-3 /* in length, 
 arranged in groups or isolated. They split up sugar into lactic acid ; 
 1 grape-sugar = C 6 H ]2 6 = 2(C 3 H 6 3 ) = 2 lactic acid. 
 Milk sugar (C ]2 H 22 O n ) may be split up by the same ferment causing it to take up 
 H 2 0, and forming 2 molecules of grape sugar, 2(C 6 H 12 6 ), which are again split 
 up into 4 molecules of lactic acid, 4(C 3 H 6 3 ). 
 
 The fungi which occur everywhere in the atmosphere are the cause of the spontaneous acidifica. 
 tion, and subsequent coagulation of milk [Milk (g 230).) 
 
FERMENTATION OF THE FATS. 309 
 
 (2) Bacillus butyricus (B. amylobacter, Van Tieghem ; Clostridium buty- 
 ricum, Vibrion butyrique, Pasteur), which in the presence of starch is often 
 colored blue by iodine, changes lactic acid into butyric acid, together with C0 2 
 and H (JPrazmowski). 
 
 C C 4 H 8 3 = 1 butyric acid. 
 2(C 3 H 6 3 ) lactic acid = < 2(C0 2 ) = 2 carbon dioxide. 
 
 ( 4 H = 4 hydrogen. 4 
 
 This fungus (Fig. 190, B) is a true anaerobe, and grows only in the absence of O. The lactic 
 acid fungus uses O very largely, and is, therefore, its natural precursor. The butyric acid fermenta- 
 tion is the last change undergone by many carbohydrates, especially by starch and inulin. It takes 
 place constantly in the fasces. 
 
 (3) A fungus, whose nature is not yet determined, causes alcohol to be formed 
 from carbo-hydrates (Jntz). The presence of yeast may cause the formation of 
 alcohol in the intestine, and in both cases also from milk sugar, which first 
 becomes changed into dextrose. 
 
 (4) Bacterium aceti (Fig. 190, A) converts alcohol into acetic acid outside the body. Alcohol 
 (CjjHjO) + O = C 2 H 4 ( Aldehyd) + H 2 0. Acetic acid (C 2 H 4 2 ) is formed from aldehyd by 
 oxidation. According to Nageli, the same fungus causes the formation of a small amount of C0 2 
 and H 2 0. As the acetic fermentation is arrested at 35° C, this fermentation cannot occur in the 
 intestine, and the acetic acid which is constantly found in the feces must be' derived from another 
 source. During putrefaction of the proteids with exclusion of air acetic acid is produced (Nencki) . 
 
 Fig. 191. 
 
 ? 
 
 12 3 4 
 
 Bacillus subttlis. I, spore ; 2, 3, 4, germination of the spore ; 5,6, short rods ; 7, jointed thread, with the formation 
 of spores in each segment or cell ; 8, short rods, some of them containing spores ; 9, spores in single short rods ; 
 10, fungus with a cilium. 
 
 (5) Starch and cellulose are partly dissolved by the schizomycetes of the 
 intestine. If cellulose be mixed with cloacal mucus (Hoppe-Seyler), or with the 
 contents of the intestine (Tappeiner), n molecules, [/z(C 6 H 10 O 6 )], take up n mole- 
 cules of water, + «(H 2 0), and produce three times n molecules C0 2 , and three 
 times n molecules of marsh gas 3 «(CH 4 ). 
 
 During the solution of cellulose, volatile acids (acetic and butyric) are evolved. When the cel- 
 lulose capsule is dissolved, the digestive juices can act upon the enclosed digestible parts of the 
 vegetable (Tappeiner, v. Knieriem). 
 
 (6) Fungi whose nature is unknown can partly transform starch (? and cellulose) 
 into sugar ; others excrete invertin e. g. , the Leukonostoc mesenteriodes, which 
 develops in the juice of turnips. Invertin changes cane . sugar into invert sugar 
 (§183,11,5). 
 
 II. Fermentation of the Fats (§251). — In certain putrefactive conditions, 
 organisms of an unknown nature cause natural fats to take up water and split into 
 glycerine and their corresponding fatty acid (§ 170). Glycerine — C 3 H 5 (HO) 3 — 
 is a triatomic alcohol, and is capable of undergoing several fermentations, accord- 
 ing to the fungus which acts upon it (§ 251). With a neutral reaction, in addition 
 to succinic acid, a number of fatty acids, H and C0 2 are formed. 
 
310 REACTION FOR INDOL. 
 
 Fitz found, under the influence of the hay bacillus (Bacillus subtilis, Fig. 191) alcohol with 
 caproic, butyric, and acetic acids; in other cases butylic alcohol is the chief product; van de Velde 
 found butyric, lactic, and traces of succinic acid with C0 2 , H 2 0, N. 
 
 The fatty acids, especially as chalk soaps, form an excellent material for fer- 
 mentation. Calcium formiate mixed with cloacal mucus ferments and yields cal- 
 cium carbonate, C0 2 and H ; calcium acetate, under the same conditions, produces 
 calcium carbonate, C0 2 and CH 4 . Among the oxy-acids, we are acquainted 
 with the fermentations of lactic, glycerinic, malic, tartaric, and citric acids. 
 
 According to Fitz, lactic acid (in combination with chalk), produces propionic and acetic acids, 
 C0 2 , H 2 0. Other ferments cause the formation of valerianic acid. Glycerinic acid, in addition 
 to alcohol and succinic acid, yields chiefly acetic acid ; malic acid forms succinic and acetic acid. 
 The other acids above enumerated yield somewhat similar products. 
 
 III. Fermentation of the Proteids (§ 249). — There do not seem to be 
 fungi of sufficient activity in the intestine to act upon undigested proteids and 
 their derivatives. Many schizomycetes, however, can produce a peptonizing fer- 
 ment. We have already seen that pancreatic digestion acts upon the proteids 
 (§ 170, II), forming, among other products, amido acids, leucin, tyrosin, and 
 other bodies. Under normal conditions, this is the greatest decomposition pro- 
 duced by the pancreatic juice. The putrefactive fermentation of the large intes- 
 tine causes further and more profound decompositions {Huffner, Nencki). Leu- 
 cin (C 6 Hi 3 N0 2 ), takes up two molecules of water, and yields valerianic acid 
 (C 5 Ci O 2 ) ammonia, C0 2 and 2(H 2 ) ; glycin, behaves in a similar manner. 
 Tyrosin (C 9 H n N0 3 ) is decomposed into indol (C S H,N), which is constantly 
 present in the intestine {Kuhne) along with C0 2 , H 2 0, H, {Nencki'). If O be 
 present, other decompositions take place. These putrefactive products are absent 
 from the intestinal canal of the foetus and the newly born {Senator). During the 
 putrefactive decomposition of proteids, C0 2 ,H 2 S, also H and CH 4 , are formed ; 
 the same result is obtained by boiling them with alkalies. Gelatin, under the 
 same conditions, yields much leucin and ammonia, C0 2 , acetic, butyric, and vale- 
 rianic acids, and glycin {Nencki). Mucin and nuclein undergo no change. Arti- 
 ficial pancreatic digestion experiments rapidly tend to undergo putrefaction. 
 
 The substance which causes the peculiar faecal odor is produced by putrefaction, but its nature is 
 not known. It clings so firmly to indol and skatol that these substances were formerly regarded as 
 the odorous bodies, but when they are prepared pure they are odorless [Bayer). The above men- 
 tioned putrefactive processes which also occur in pancreas undergoing decomposition, may be inter- 
 rupted by antiseptics (salicylic acid). The putrefactive products of the pancreas give a red color 
 or precipitate with chlorine water. 
 
 Indol. — Among the solid substances in the large intestine formed only by 
 putrefaction is indol (C 8 H 7 N), a substance which is also formed when proteids are 
 heated with alkalies, or by overheating them with water to 200 C. It is the stage 
 preceding the indican in the urine. If the products of the digestion of the pro- 
 teids — the peptones — are rapidly absorbed, there is only a slight formation of 
 indol ; but when absorption is slight, and putrefaction of the products of pan- 
 creatic digestion occurs, much indol is formed, and indican appears in the urine. 
 
 Jaffe found much indican in the urine in strangulated hernia, and when the small intestine was 
 obstructed. Landois observed the same after the transfusion of heterogeneous blood (j! 262, 1). 
 
 Reactions for Indol. — Acidulate strongly with HC1, and shake vigorously after adding a few 
 drops of turpentine. If there be an intense red color, the pigment is removed by ether. The sub- 
 stance which, after the digestion of fibrin by trypsin, and which gives a violet color with bromine 
 water ($ 170, 2), can be removed by chloroform. In addition to the last pigment, there is a second 
 one, which passes over during distillation, and which can be extracted from the distillate by ether. 
 Both substances seem to belong to the indigo group (Krukenberg). 
 
 A. Bayer prepared indigo-blue artificially from orthd-phenyl-propionic acid, by boiling it with dilute 
 caustic soda, after the addition of a little grape sugar. He obtained indol and skatol from indigo 
 blue. Hoppe-Seyler found that on- feeding rabbits with ortho-nitrophenyl-propionic acid, much 
 indican was present in the urine. 
 
PROCESSES IN THE LARGE INTESTINE. 311 
 
 Phenol (C 6 H 6 0j is formed by putrefaction in the intestine, and it is also 
 formed when fibrin and pancreatic juice putrefy outside the body {Baumann), 
 while Brieger found it constantly in the faeces. It seems to be increased by the 
 same circumstances that increase indol {Salkowski), as an excess of indican in 
 the urine is accompanied by an increase of phenyl sulphuric acid in that fluid 
 (§ 262). 
 
 From putrefying flesh and fibrin amido-phenyl propionic acid is obtained, as a decomposition 
 product of tyrosin. A part of this is transformed by putrefactive ferments into hydrocinnamic acid 
 (phenyl propionic acid). The latter is completely oxidized in the body into benzoic acid, and 
 appears as hippuric acid in the urine. Thus is explained the formation of hippuric acid from a 
 purely albuminous diet (£. and H. Salkowski). 
 
 ' Skatol (C 9 H 9 N) = methyl indol — {Brieger), is a constant human faacal sub- 
 stance, and has been prepared artificially by Nencki and Secretan from egg 
 albumin, by allowing it to putrefy for a long time under water. It also appears 
 in the urine as a sulphuric acid compound. The excretin of human faces, 
 described by Marcet, is related to cholesterin, but its history and constitution are 
 unknown. 
 
 According to the Brothers Salkowski, skatol and indol are both formed from a common substance 
 which exists preformed in albumen, and which, when it is decomposed, at one time yields more 
 indol, at another skatol, according as the hypothetical " indolfungus" or " skatol- fungus " is the 
 more abundant. 
 
 It is of the utmost importance, in connection with the processes of putrefac- 
 tion, to determine whether they take place when oxygen is excluded or not {Pas- 
 teur). When O is absent, reductions take place ; oxy-acids are reduced to 
 fatty acids, and H,CH 4 and H 2 S are formed ; while the H may produce further 
 reductions. If O be present the nascent H separates the molecule of free ordi- 
 nary oxygen ( = 2 ) into two atoms of active oxygen ( = O). Water is formed 
 on the one hand, while the second atom of O is a powerful oxidizing agent {Hoppe- 
 Seyler). 
 
 [It is not improbable that some substances, as sulphur, are in part rendered soluble and absorbed 
 by the action of the nascent hydrogen evolved by the schizomycetes, forming a soluble hydrogen 
 compound with the substance {Matthew Hay).\ 
 
 It is remarkable that the putrefactive processes, after the development of phenol, indol, skatol, 
 cresol, phenyl propionic and phenyl acetic acids are afterward limited, and after a certain concentra- 
 tion is reached they cease altogether. The putrefactive process produces antiseptic substances 
 which kill the micro-organisms ( Wernicli), so we may assume that these substances limit to a cer- 
 tain extent the putrefactive processes in the intestine. 
 
 The reaction of the intestine immediately below the stomach is acid, but the 
 pancreatic and intestinal juices cause a neutral and afterward an alkaline reaction, 
 which obtains along the whole small intestine. In the large intestine, the re- 
 action is generally acid, on account of the acid fermentation and the decomposi- 
 tion of the ingesta and the faeces. 
 
 185. PROCESSES IN THE LARGE INTESTINE.— Within the 
 large intestine, the fermentative and putrefactive processes are certainly more 
 prominent than the digestive processes proper, as only a very small amount of the 
 intestinal juice is found in it {Kiihne). The absorptive function of the large 
 intestine is greater than its secretory function, as at the beginning of the colon its 
 contents are thin and watery, but in the further course of the intestine they 
 become more solid. Water and the products of digestion in solution are not the 
 only substances absorbed, but under certain circumstances unchanged fluid egg- 
 albumin ( Voit and Bauer, Czerny and Latschenberger), milk and its proteids 
 {Eichhorsf), flesh juice, solution of gelatin, myosin with common salt, may also 
 be absorbed. Experiments with acid albumin, syntonin, or blood serum gave no 
 result. Toxic substances are certainly absorbed more rapidly than from the 
 stomach {Savory). [In the dog the secretion of the large intestine has no 
 
312 CHARACTERS OF THE M£CES. 
 
 digestive properties, but fats are absorbed in it. Klug and Koreck regard its 
 Lieberkiihnian glands not as secreting, but as absorbing structures.] The faecal 
 matters axe formed or rather shaped in trie lower part of the gut. The caecum of 
 many animals, e. g., rabbit, is of considerable size, and in it fermentation seems 
 to occur with considerable energy, giving rise to an acid reaction. In man, the 
 chief function of the caecum is absorption, as is shown by the great number of 
 lymphatics in its walls. From the lower part of the small intestine and the 
 caecum onward, the ingesta assume the faecal odor. 
 
 The amount of faeces is about [5 oz.] or 170 grms. (60 to 250 grms.) in 
 twenty-four hours ; but if much indigestible food be taken, it may be as much as 
 500 grms. The amount is less, and the absolute amount of solids is less, after a 
 diet of flesh and albumin, than after a vegetable diet. The faeces are rendered 
 lighter by the evolution of gases, and hence they float in water. 
 
 The consistence of the faeces depends on the amount of water present — it is 
 usually about 75 per cent. The amount of water depends partly on the food — 
 pure flesh diet causes relatively dry faeces, while substances rich in sugar yield 
 faeces with a relatively large amount of water. The quantity of water taken has 
 no effect upon the amount of water in the faeces. But the energy of the peristal- 
 sis has this effect, that the more energetic it is, the more watery the faeces are, 
 because sufficient time is not allowed for absorption of the fluid from the ingesta. 
 Paralysis of the blood and lymph vessels, or section of the nerves, leads to a 
 watery condition of the faeces (§ 183). 
 
 The reaction is often acid in consequence of lactic acid being developed from 
 the carbohydrates of the food. Numerous other acids produced by putrefaction 
 are also present (§ 184). If much ammonia be formed in the lower part of the 
 intestine, a neutral or even alkaline reaction may obtain. A copious secretion of 
 mucus favors the occurrence of a neutral reaction. 
 
 The odor, which is stronger after a flesh diet than after a vegetable diet, is 
 caused by some faecal products of putrefaction, which have not yet been isolated ; 
 also by volatile fatty acids and by sulphuretted hydrogen, when it is present. 
 
 The color of the faeces depends upon the amount of altered bile pigments 
 mixed with them, whereby a bright yellow to a dark brown color is obtained. 
 
 The color of the food is also of importance. If much blood be present in the food, the faeces 
 are almost brownish black, from haematin ; green vegetables = brownish green, from chlorophyll ; 
 bones (dog) = white, from the amount of lime; preparations of iron = black, from the formation 
 of sulphide of iron. 
 
 The faeces contain — 
 
 (1) The unchanged residue of animal or vegetable tissues used as food; hairs, 
 horny and elastic tissues ; most of the cellulose, woody fibres, spiral vessels of 
 vegetable cells, gum. 
 
 (2) Portions of digestible substances, especially when these have been taken. in 
 too large amount, or when they have not been sufficiently broken up by chewing. 
 Portions of muscular fibres, ham, tendon, cartilage, particles of fat, coagulated 
 albumin — vegetable cells from potatoes and vegetables, raw starch, etc. 
 
 All food yields a certain amount of residue — white bread, 3.7 per cent. ; rice, 4. 1 per cent. ; flesh, 
 4.7 per cent. ; potatoes, 9.4 per cent. ; cabbage, 14.9 per cent. ; black bread, 15 per cent. ; yellow 
 turnip, 20.7 per cent. (Rubner). 
 
 (3) The decomposition products of the bile pigments, which do not now give 
 the Gmelin-Heintz reaction ; as well as the altered bile acids (§ 177, 2). This 
 reaction, however, may be obtained in pathological stools, especially in those of 
 a green color ; unaltered bilirubin, biliverdin, glycocholic and taurocholic acids 
 occur in meconium {Zweifel, Hoppe-Seyler, § 182). 
 
 [MacMunn found no unchanged bile pigments in the faeces. A substance called stercobilin is 
 obtained from the faeces, and it closely resembles what has been called " febrile " urobilin, but it is 
 certainly different from normal urobilin.] 
 
COMPOSITION OF THE FAECES. 313 
 
 (4) Unchanged mucin and nuclein— -the latter occasionally after a diet of bread, 
 together with partially disintegrated cylindrical epithelium from the intestinal 
 canal, and occasionally drops of oil. Cholesterin is very rare. [Ten grains of a 
 substance, stercorin, said to be a modification of cholesterin, occur in the faeces 
 (Flint).] The less the mucus is mixed with the faeces, the lower the part of the 
 intestine from which it was derived (Nothnagel). 
 
 (5) After a milk diet, and also after a fatty diet, crystalline needles of lime 
 combined with fatty acids and chalk soaps constantly occur, even in sucklings 
 ( Wegscheider). Even unchanged masses of casein and fat occur during the milk 
 cure. Compounds of ammonia with the acids mentioned as the result of putre- 
 faction (§ 184, III) belong to the faecal matters (Brieger). 
 
 (6) Among inorganic residues, soluble salts rarely occur in the faeces, because 
 they diffuse readily, e. g., common salt, and the other alkaline chlorides, the com- 
 pounds of phosphoric acid, and some of those of sulphuric acid. The insoluble 
 compounds, of which ammoniaco-magnesic or triple phosphate, neutral calcic 
 phosphate, yellow-colored lime salts, calcium carbonate, and magnesium phos- 
 phate are the chief, form 70 per cent, of the ash. Some of these insoluble sub- 
 stances are derived from the food, as lime from bones, and in part they are 
 excreted after the food has been digested, as ashes are eliminated from food which 
 has been burned. 
 
 Fig. 192. 
 
 
 3 'fiji 
 
 L\(\\ 
 
 '" 1 
 
 Jim) 
 
 ^ Hill* 
 
 9 
 
 I, Bacterium coli commune; z, bacterium lactis aerogenes; 3 and 4, the large bacilli of Bienstock, with partial endo- 
 genous spore formation ; 5, the various stages in the development of the bacillus which causes the fermentation 
 of albumin. 
 
 Concretions. — The excretion of inorganic substances is sometimes so great, that they form in- 
 crustations around other faecal matters. Usually ammoniaco-magnesic phosphate occurs in large 
 crystals by itself, or it may be mixed with magnesium phosphate. 
 
 (7) Micro-organisms. — A considerable portion of normal faacal matter con- 
 sists of micrococci and micro-bacteria (Bacterium termo — Woodward, Nothnagel). 
 Bacillus subtilis is not very plentiful, while yeast is seldom absent (Frerichs, 
 Nothnagel'). 
 
 To isolate the individual fungi, Escherich has made pure cultivations from the intestinal con- 
 tents of sucklings, and Bienstock from adults. In the intestine of sucklings which have been 
 nourished entirely on their mother's milk, the Bacterium lactis aerogenes (Fig. 192, 2) causes the 
 lactic acid fermentation with the evolution of C0 2 and H, in the upper part of the canal where 
 still some milk sugar is unabsorbed. In the evacuations is the characteristic slender Bacterium 
 coli commune (Fig. 192, 1). In addition, occasionally there are other bacilli, cocci, spores of yeast, 
 and a mould (Escherich). 
 
 In the faeces of an adult, Bienstock detected two large forms of Bacilli (Fig. 192, 3, 4), closely 
 resembling Bacillus subtilis in form and size, but distinguished only from it by the form of its pure 
 cultivation, by the mode of growth of its spores, and by the absence of movements. These two 
 forms can be distinguished microscopically by the mode of their cultivation, which is either in the 
 form of a grape or a flat membrane. These two do not excite a fermentative action. A third 
 micrococcus-like, small, very slowly developing bacillus occurs in three-fourths of all stools. A 
 fourth kind (absent in sucklings) is the specific bacillus (<j 184, III), causing the decomposition of 
 albumin, resulting in the products of putrefaction and a faecal odor. This is the only bacillus that 
 excites these processes in the intestine ; but it does not decompose casein and alkali-albumin. In 
 Fig. 192, 5, a-g, the stages in the development of this bacillus are represented, but the stages from 
 c and g are absent in the faeces, and are found only in artificial cultivations. 
 
314 PATHOLOGICAL VARIATIONS OF DIGESTION. 
 
 If the faeces are simply investigated microscopically and without special precautions, there are 
 other fungi, some of which may be introduced through the anus. In stools that contain much 
 starch, the bacillus amylobacter, which is tinged blue with iodine, occurs (§ 184), and other small, 
 globular or rod-like fungi, which give a similar reaction (Notknagel, Uffelmann). 
 
 The changes of the intestinal contents have been studied on persons with an accidental intestinal 
 fistula, or an artificial anus. 
 
 186. PATHOLOGICAL VARIATIONS.— (A) The taking of food may be interfered with 
 by spasm of the muscles of mastication (usually accompanied by general spasms), stricture of the 
 oesophagus, by cicatrices after swallowing caustic fluids {e.g., caustic potash, mineral acids), or by 
 the presence of a tumor, such as cancer. Inflammation of all kinds in the. mouth or pharynx inter- 
 feres with the taking of food. Impossibility of swallowing occurs as part of the general phenomena 
 in disease of the medulla oblongata, in consequence of paralysis of the motor centre (superior olives) 
 for fhe,facial, vagus, and hypoglossal nerves, and also for the afferent or sensory fibres of the glosso- 
 pharyngeal, vagus and trigeminus. Stimulation or abnormal excitation of these parts causes spas- 
 modic swallowing and the disagreeable feeling of a constriction in the neck (globus hystericus). 
 
 (B) The secretion of saliva is diminished during inflammation of the salivary glands; occlusion 
 of their ducts by concretions (salivary calculi) ; also by the use of atropin, daturin, and during fever, 
 whereby the secretory (not the vasomotor) fibres of the chorda appear to be paralyzed ($145). 
 When the fever is very high, no saliva is secreted. The saliva secreted during moderate fever is 
 turbid and thick, and, usually, acid. As the fever increases, the diastatic action of the saliva dimin- 
 ishes {Uffelmann). The secretion is increased by stimulation of the buccal nerves (inflammation, 
 ulceration, trigeminal neuralgia), so that the saliva is secreted in great quantity. Mercury and jabo- 
 randi cause secretion of saliva, the former causing stomatitis, which excites the secretion of saliva 
 reflexly. Even diseases of the stomach accompanied by vomiting cause secretion of saliva. A 
 very thick, tenacious, sympathetic saliva occurs when there is violent stimulation of the vascular 
 system during sexual excitement, and also during certain psychical conditions. The reaction of the 
 saliva is acid in catarrh of the mouth, in fever, in consequence of decomposition of the buccal 
 epithelium, and in diabetes mellitus, in consequence of acid fermentation of the saliva, which 
 contains sugar. Hence, diabetic persons often suffer from carious teeth. Unless the mouth of an 
 infant be kept scrupulously clean, the saliva is apt to become acid. 
 
 (C) Disturbances in the activity of the musculature of the stomach may be due to paralysis 
 of the muscular layers, whereby the stomach becomes distended, and the ingesta remain a long 
 time in it. A special form of paralysis of the stomach is due to non-closure of the pylorus (Ebstein). 
 This may be due to disturbances of innervation of a central or peripheral nature, or there may be 
 actual paralysis of the pyloric sphincter, or anaesthesia of the pyloric mucous membrane, which 
 acts reflexly upon the sphincter muscle; and, lastly, it may be due to the reflex impulse not being 
 transferred to the efferent fibre within the nerve centre. Abnormal activity of the gastric muscula- 
 ture hastens the passage of the ingesta into the intestine ; vomiting often occurs. 
 
 Gastric digestion is delayed by violent bodily or mental exercise, and sometimes it is arrested 
 altogether. Sudden mental excitement may have the same effect. These effects are, very probably, 
 caused through the vasomotor nerves of the stomach. Feeble and imperfect digestion may be of a 
 purely nervous nature (Dyspepsia nervosa — Leube ; Neurasthenia gastrica — Burkart). An exces- 
 sive formation of acid may be due to nervous disturbance, and is called "nervous gastroxynsis," 
 / by Rossbach. 
 
 [Action of Alcohol, Tea, etc., in Digestion. — According to J. W. Fraser, all infused beverages, 
 tea, coffee, cocoa, retard the peptic digestion of proteids, with few exceptions. The ret arding actio n 
 is le ss with coffec ihan with tea. The tannic acid and volatile oil seem to be the" retarding ingi ecti- 
 ents in teas. Distilled Spirits — brandy, whisky, gin — have but a trifling retarding effect on the 
 digestive processes ; and when one considers their action on the secretory glands, it follows that in 
 moderate dietetic doses they promote digestion. Wines are highly inimical to salivary digestion, 
 but this is due to their acidity ; and this effect can be removed by the addition of an alkali. Wines 
 retard peptic digestion, the sparkling less than the still wines. Tea has an intensely inhibitory 
 action on salivary digestion— in fact, a small quantity paralyzes the action of salive — while coffee 
 has only a slight effect. This action of tea is due to the tannin. Tea, coffee and cocoa all retard 
 peptic digestion when they form 20 per cent, of the digestive mixture (W. Roberts, p. 245).] 
 
 Inflammatory or Catarrhal Affections of the stomach, as well as ulceration and new forma- 
 tions, interfere with digestion, and the same result is caused by eating too much food which is diffi- 
 cult of digestion, or taking too much highly-spiced sauces or alcohol. In the case of a dog suffer- 
 ing from chronic gastric catarrh, Grutzner observed that the secretion took place continuously, and 
 that the gastric juice contained little pepsin, was turbid, sticky, feebly acid, and even alkaline. The 
 introduction of food did not alter the secretion, so that in this condition the stomach really obtains 
 no rest. The chief cells of the gastric glands were turbid. Hence, in gastric catarrh we ought to 
 eat frequently, but take little at a time, while, at the same time, dilute (0.4 per cent.) hydrochloric 
 acid ought to be administered. Small doses of common salt seem to aid digestion. 
 
 [Absence of HC1. — HC1 is always absent in carcinoma of the stomach (van de Velde); amyloid 
 degeneration of the gastric mucous membrane (Edinger), and sometimes in fever. In all these 
 cases the acid reaction is due to lactic or butyric acid. The absence of HC1 in cancer of the stomach 
 
DIGESTION DURING FEVER AND ANAEMIA. 315 
 
 is an important diagnostic and prognostic symptom. It is not absent in simple dilatation of the 
 stomach. Test the contents of the stomach for free HC1 with tropaeolin (red color), methyl violet 
 (blue), and with ferric chloride and carbolic acid {Uffelmann). -fa per cent, of free HC1 causes 
 the amethyst-blue of the last to become steel-gray, while somewhat more discharges the color 
 altogether.] 
 
 [In testing for the presence of free lactic acid in the gastric contents, use a freshly-prepared 
 solution of 10 c. c. of 4 per cent, carbolic acid, 20 c. c. distilled water, and one drop of the officinal 
 liquor of the perchloride of iron. The amethyst-blue color is made yellow by adding y z to )/$ of 
 its volume of dilute lactic acid (1 per 1000). The lactic acid is easily extracted, by ether, from 
 the gastric contents, and the reaction can then be performed with the residue obtained after evapo- 
 rating the ether. A solution of 1 drop of the liquor perchloride in 50 c. c. of water is made yellow 
 by lactic acid (Uffelmann),~\ 
 
 Feeble Digestion may be caused either by imperfect formation of acid or pepsin, so that both 
 substances may be administered in such a condition. [It may also be due to deficient muscular 
 power in the wall of the stomach]. In other cases, lactic, butyric and acetic acids are formed, 
 owing to the presence of lowly organisms. In such cases, small doses of salicylic acid, together 
 with some hydrochloric acid, are useful (ffbppe-Seyler). Pepsin need not be given often, as it is 
 rarely absent, even from the diseased gastric mucous membrane. Albumin has been found in the 
 gastric juice in cases of gastric catarrh and cholera. 
 
 (D) Digestion during Fever and Anaemia. — Beaumont found that in the case of Alexis St. 
 Martin, when fever occurred, a small amount of gastric juice was secreted; the mucous membrane 
 was dry, red, and irritable. Dogs suffering from septicemic fever, or rendered anaemic by great loss 
 of blood, secrete gastric juice of feeble digestive power and containing little acid (Manassein). [In 
 acute diseases accompanied by fever, the inner cells of the fundus glands of the human stomach 
 may disappear (C. Kupffer.)~\ Hoppe-Seyler investigated the gastric juice of a typhus patient, in 
 which van de Velde found no free acid, and he found the same in gastric catarrh, fever, and in can- 
 cer of the stomach. The gastric juice of the typhus patient did not digest artificially, even after the 
 addition of hydrochloric acid. The diminution of acid, under these circumstances, favors the occur- 
 rence of a neutral reaction, so that, on the one hand, digestion cannot proceed, and on the other, 
 fermentative processes. (lactic and butyric acid fermentations with the evolution of gases) occur. 
 These results are associated with the presence of micro-organisms and Sarcina veniriculi {Good- 
 sir). He advises the "administration of hydrochloric acid and pepsin, and when there are symptoms 
 of fermentation, small doses of salicylic acid. Uffelmann found that the secretion of a peptone- 
 forming gastric juice ceased in fever, when the fever is severe at the outset, when a feeble condition 
 occurs, or when the temperature is very high. The amount of juice secreted is certainly diminished 
 during fever. The excitability of the mucous membrane is increased, so that vomiting readily 
 occurs. The increased excitability of the vasomotor nerves during fever (Heidenhain) is disadvan- 
 tageous for the secretion of the digestive fluids. Beaumont observed that fluids are rapidly ab- 
 sorbed from the stomach during fever, but the absorption of peptones is diminished on account of 
 the accompanying catarrhal condition of the stomach, and the altered functional activity of the 
 muscularis mucosae [Leube). 
 
 Many salts, when given in large amount, disturb gastric digestion, c. g., the sulphates. While 
 the alkaloids, morphia, strychnia, digitalin, narcotin, veratria, have a similar action ; quinine favors 
 it ( Wolberg). In some nervous individuals a " peristaltic unrest of the stomach," conjoined with a 
 dyspeptic condition, occurs (Kussmaul). [Professor James directs attention to the value of peptic 
 and pancreatic salts, which are preparations of common salt mixed with pepsin and the ferments of 
 the pancreas respectively.] 
 
 [Artificial Digestion is affected by various salts according to their nature and dilution. The 
 digestion of fibrin by pepsin goes on best without the addition of salts, being diminished by magnesic 
 sulphate, sodic carbonate and sulphate. The digestion of fibrin by pancreatic extract is accelerated 
 by sodic carbonate (Heidenhain), and retarded by MgS0 4 and Na 2 S0 4 . The diastatic action 
 of the saliva and pancreas on starch is greatly accelerated by NaCl (2 per cent.) while Na 2 CO a , 
 Na 2 S0 4 , MgS0 4 slow it (Pfeifer).] 
 
 According to Schiitz, artificial gastric digestion is retarded by a 2 per cent, solution of alcohol, 
 and also by a solution of salicylic acid (.06 to .1 per cent.). Buchner, however, finds that 10 per 
 cent, of alcohol does not affect artificial gastric digestion,- while above 20 per cent, arrests it. Beer 
 hinders digestion. 
 
 (E) In acute diseases, the secretion of bile is affected ; it becomes less in amount and more 
 watery, i. e., it contains less specific constituents. If the liver undergoes great structural change, the 
 secretion may be arrested. 
 
 (F) Gallstones When decomposition of the bile occurs, gall stones are formed in the gall 
 
 bladder or in the bile ducts. Some are white, and consist almost entirely of stratified layers of crys- 
 tals of cholesterin. The brown forms consist of bilirubin, lime and calcium carbonate, often 
 mixed with iron, copper, and manganese. The gall stones in the gall bladder become faceted by 
 rubbing against each other. The nucleus of the white stones often consists of 'chalk and bile color- 
 ing matters, together with nitrogenous residues, derived from shed epithelium, mucin, bile salts and 
 fats. Gall stones may occlude the bile duct and cause chokemia. When a small stone becomes 
 
316 COMPARATIVE PHYSIOLOGY OF DIGESTION. 
 
 impacted in a duct, it gives rise to excessive pain, constituting hepatic colic, and may even cause 
 rupture of the bile duct with its sharp edges. 
 
 (G) Nothing certain has been determined regarding the pancreatic secretion in disease, but in 
 fever it appears to be diminished in amount and digestive activity. The suppression of the pancre- 
 atic secretion [as by a cancerous tumor of the head of the pancreas] is often accompanied by the 
 appearance of fat in the form of globules or groups of crystals in the faeces. 
 
 ( H ) Constipation is a most important derangement of the digestive tract. It may be caused by 
 — ( i) Conditions which obstruct the normal channel, e.g., constriction of the gut from stricture — in 
 the large gut after dysentery, tumors, rotation on its axis of a loop of intestine (volvulus), or invagina- 
 tion, occlusion of a coil of gut in a hernial sac, or by the pressure of tumors or exudations from 
 without, or congenital absence of the anus. (2) Too great dryness of the contents, caused by too 
 little water in the articles of diet, dimiuution of the amount of the digestive secretions, e.g., of bile 
 in icterus ; or in consequence of much fluid being given off by other organs, as after copious secre- 
 tion of saliva, milk, or in fever. (3) Variations in the functional activity of the muscles and motor 
 nervous apparatus of the gut may cause constipation, owing to imperfect peristalsis. This condition 
 occurs in inflammations, degenerations, chronic catarrh, diaphragmatic inflammation. Affections of 
 the spinal cord, and sometimes also of the brain, are usually accompanied by slow evacuation of the 
 intestine. Whether diminished mental activity and hypochondriasis are the cause of, or are caused 
 by constipation is not proved. Spasmodic contraction of a part of the intestine may cause tempo- 
 rary retention of the intestinal contents, and, at the same time, give rise to great pain or colic ; the 
 same is true of spasm of the anal sphincter, which may be excited reflexly from the lower part of 
 the gut. The faecal masses in constipation are usually hard and dry, owing to the water being ab- 
 sorbed ; hence they form large masses or scybala within the large intestine, and these again give 
 rise to new resistance. 
 
 Among the reagents which prevent evacuation of the bowels, some paralyze the motor apparatus 
 temporarily, e.g., opium, morphia; some diminish the secretion of the intestinal mucous membrane, 
 and cause constriction of the blood vessels, as tannic acid, vegetables containing tannin, alum, chalk, 
 lead acetate, silver nitrate, bismuth nitrate. 
 
 (I) Increased evacuation of the intestinal contents is usually accompanied by a watery condition 
 of the faeces, constituting diarrhoea. 
 
 The causes are : — 
 
 1 . A too rapid movement of the contents through the intestine, chiefly through the large intestine, 
 so that there is not time for the normal amount of absorption to take place. The increased peristal- 
 sis depends upon stimulation of the motor nervous apparatus of the intestine usually of a reflex 
 nature. Rapid transit of the contents through the intestine, causes the evacuation of certain sub- 
 stances, which cannot be digested in so short a time. 
 
 2. The stools become thinner, from the presence of much water, mucus, and the admixture with 
 fat, and by eating fruit and vegetables. In rare cases, when the evacuations contain much mucin, 
 Charcot's crystals occur (Fig. 144, c). In ulceration of the intestine leucocytes (pus) are present 
 (Nothnagel). 
 
 3. Diarrhoea may occur as a consequence of disturbance of the diffusion processes through the 
 intestinal walls, as in affections of the epithelium, when it becomes swollen in inflammatory or 
 catarrhal conditions of the intestinal mucous membrane. [Irritation over the abdomen, as from the 
 subcutaneous injection of small quantities of saline solutions, causes diarrhoea (M. ffay).~\ 
 
 4. It may also be due to increased secretion into the intestine, as in capillary diffusion, when 
 magnesium sulphate in the intestine attracts water from the blood. 
 
 The same occurs in cholera, when the stools are copious and of a rice-water character, and are 
 loaded with epithelial cells from the villi. The transudation into the intestine is so great that the 
 blood in the arteries becomes very thick, and may even on this account cease to circulate. 
 
 Transudation into the intestine also takes place as a consequence of paralysis of the vasomotor 
 nerves of the intestine. This is perhaps the case in diarrhoea following upon a cold. Certain sub- 
 stances seem directly to excite the secretory organs of the intestines or their nerves, such as the 
 drastic purgatives (J 180). Pilocarpin injected into the blood causes great secretion (Masloff). 
 
 During febrile conditions, the secretion of the intestinal glands seems to be altered quantita- 
 tively and qualitatively, with simultaneous alteration of the functional activity of the musculature 
 and the organs of absorption, while the excitability of the mucous membrane is increased (Uffel- 
 mann). It is important to note that in many acute febrile diseases the amount of common salt in the 
 urine diminishes, and increases again as the fever subsides. 
 
 187. COMPARATIVE.— Salivary Glands. — Among Mammals the herbivora have larger 
 salivary glands than the carnivora ; while midway between both are the omnivora. The_wha]eJias 
 nos alivary gland s. The pinnipedia have a small parotid, which is absent in the echidna. The 
 dog^and many c*aTnivora have a special gland lying in the orbit, the orbital or zygomatic g land. In 
 Birds the salivary glands open at the angle of the mouth ; in them tEFparajSjEa^^r" Among 
 Reptiles the parotid of some species is so changed as to fqjjrC^jsorT'giahds ; the;tortbise has sub- 
 lingual glands ; reptiles have labial glands. The Amphibia andfTflrcsTiave merely small glands 
 scattered over the mouth. The salivary glands are large in Insects ; some of them secre.te formic 
 
HISTORICAL ACCOUNT OF DIGESTION. 317 
 
 acid. The salivary glands are well developed in molluscs, and the saliva of Dolium galea contains 
 more than 3 per cent, of free sulphuric acid (?). The cephalopods have double glands. 
 
 A Crop is not present in any mammal ; the stomach is either simple, as in man, or, as in many 
 rodents, it is divided into two halves, into a cardiac and a pyloric portion. The intestine is short in 
 flesh-eating animals and long in herbivora. The stomach of ruminants is compound, and consists 
 of four cavities. The first and largest is the paunch or rumen, then the reticulum. In these 
 two cavities, especially the former, the ingesta are softened and ■ undergo fermentation. They are 
 then returned to the mouth by the action of the voluntary muscular fibres, which reach to the 
 stomach. This is the process of rumination. The ingesta are chewed again in the mouth, and I 
 are again swallowed, but this time they enter the third cavity or psalterium — (which is absent in I 
 the camel) — and thence into the fourth stomach or abomasum in which the fermentative digestion 
 takes place. The caecum is a very large and important digestive organ in herbivora, and in most 
 rodents; it is small in man, and absent in carnivora. The oesophagus in grain- eating Birds not 
 unfrequently has a blind diverticulum or crop for softening the food. In the crop of pigeons during 
 the breeding season, there is formed a peculiar secretion — "pigeon's milk," which is used to feed 
 the young (J. Hunter). The stomach consists of a glandular proventriculus and a strong muscu- 
 lar stomach which is covered with horny epithelium and triturates the food. There are usually two 
 fluid diverticula on the small intestine near where it joins the large gut. In Fishes the intestinal 
 canal is usually simple ; the stomach is merely a dilatation of the tube ; and at the pylorus there 
 may be one, but usually many, blind glandular appendages (the appendices pyloricse). There are 
 usually longitudinal folds in the intestinal mucous membrane, but in some fishes, e. g., the shark, 
 there is a spiral valve. [It is curious to find that the inversive (cane-sugar) ferment is wanting in 
 the herbivora, as the cow, horse and sheep, but is present in the carnivora, as the dog and cat. It 
 is also met with in birds and reptiles, and in many of the invertebrates, as the ordinary earthworm 
 {Matthew Hay).~\ 
 
 In Amphibia and Reptiles the stomach is a simple dilatation ; the gut is larger in vegetable 
 feeders than in flesh feeders. T he liver is never absent in vertebrates, although the gall bladder 
 frequently is. The pancreas is absent in some, fishes. 
 
 Digestion in Plants. — The observations on the albumin-digesting power of some plants (Candy, 
 i8bg ; Ch. Darwin, 187s) are extremely interesting. The sun dew or drosera has a series of ten- 
 tacles on the surface of its leaves, and the tentacles are provided with glands. As soon as an insect 
 alights upon a leaf it is suddenly seized by the tentacles, the glands pour out an acid juice over the 
 prey, which is gradually digested ; all except the chitinous structures. The secretion, as well as 
 the subsequent absorption of the products of digestion, are accomplished by the activity of the pro- 
 toplasm of the cells of the leaves. The digestive juice contains a pepsin-like ferment and formic 
 acid. Similar phenomena are manifested by the Venus fly trap (Diona?a), by pinguicula, as well as 
 by the cavity of the altered leaves of nepenthes. About fifteen species of these " insectivorous " 
 or carnivorous plants are known. [The action of papain, and other ferments analogous in their 
 action to trypsin, are referred to in \ 170.] 
 
 188. HISTORICAL. — Digestion in the Mouth. — The Hippocratic school was acquainted 
 with the vessels of the teeth ; Aristotle ascribed an uninterrupted growth to these organs, and he 
 further noticed that animals that were provided with horns and had cloven hoofs, had an imperfect 
 set of teeth — the upper incisors were absent. It is curious to note that in some cases where men 
 have had an excessive formation of hairy appendages, the incisor teeth have been found to be badly 
 developed. The muscles of mastication were known at an early period; Vidius (f 1567) described 
 the temporo- maxillary articulation with its meniscus. The older observers regarded the saliva as 
 a solvent, and in addition, many bad qualities, especially in starving animals, were ascribed to it. 
 This arose from the knowledge of the saliva of mad animals, and the parotid saliva of poisonous 
 snakes. Human saliva, without organisms, is poisonous to birds ( Gautier). The salivary glands 
 have been known for a long time. Galen (131-203 a.d.) was acquainted with Wharton's duct, 
 and Aetius (270 A.D.) with the sub-maxillary and sublingual glands. Hapel de la Chenaye (1780) 
 obtained large quantities of saliva from a horse, in which he was the first to make a salivary fistula. 
 Spallanzani (1786) asserted that food mixed with saliva was more easily digested than food moist- 
 ened with water. Hamberger and Siehold investigated the reaction, consistence and specific gravity 
 of saliva, and found in it mucus, albumin, common salt, calcium and sodium phosphates. Berzelius 
 gave the name ptyalin to the characteristic organic constituent of saliva, but Leuchs (1831) was 
 the first to detect its diastatic action. 
 
 Gastric Digestion. — Digestion was formerly compared to boiling, whereby solution was effected. 
 According to Galen, only substances that have been dissolved\passed through the pylorus into the 
 intestine. He described the movements of the stomach and the peristalsis of the intestines. 
 Agli an gave names to the fourjtojnachs.pX. the rumin ant,;, Vidius (f 1567) noticed the numerous 
 smallapertures of the gastric glands. Van Helmont (f 1644) expressly notices the acidity of the 
 stomach. Reaumur (1752) knew that a juice was secreted by the stomach, which effected solution, 
 and with which he and Spallanzani performed experiments on digestion outside the body. Car- 
 minati (1785) found that the stomachs of carnivora during digestion secreted a very acid juice. 
 Prout (1824) discovered the hydrochloric acid of the gastric juice, Sprott and Boyd (1836) the 
 
318 HISTORICAL. 
 
 glands of the gastric mucous membrane, while Wasmann and Bischoff noted the two kinds of 
 gastric glands. After Beaumont (1834) had made his observations upon Alexis St. Martin, who 
 had a gastric fistula caused by a gunshot wound, Bassow (1842) and Blondlot (1843) made the first 
 artificial gastric fistulse upon animals. Eberle (1834) prepared artificial gastric juice. Mialhe 
 called albumin, when altered by gastric digestion, albuminose ; Lehmann, who investigated this 
 \ substance more carefully, gave it the name peptone. Schwann isolated pepsin (1836), and estab- 
 j lished the fact of its activity in the presence of hydrochloric acid. 
 
 Pancreas, Bile, Intestinal Digestion. — The Pancreas was known to the Hippocratic School ; 
 Maur. Hoffmann (1642) demonstrated its duct (fowl), and Wirsung described it in man. Regner 
 de Graaf (1664) collected the pancreatic juice from a fistula, and Tiedemann and Gmelin found it 
 to be alkaline, while Lauret and Lassaigne found that it resembled saliva. Valentin discovered its 
 diastatic action, Eberle its emulsionizing power, and CI. Bernard (1846) its tryptic and fat- splitting 
 properties. The last mentioned function was referred to by Purkinje and Pappenheim (1836). 
 
 Aristotle characterized the bile as a useless secretion ; according to Erasistratus (304 B. a), fine 
 invisible channels conduct the bile from the liver into the gall bladder. Aretaeus ascribed icterus 
 to obstruction of the bile duct. Benedetti (1493) described gall stones. According to Jasolinus 
 (1573), the gall bladder is emptied by its own contractions. Sylvius de la Boe noticed the lymph- 
 atics of the liver (1640) ; Walaeus, the connective tissue of the so-called capsule of Glisson (1641). 
 Haller indicated the uses of bile in the digestion of fats. 
 
 The liver cells were described by Henle, Purkinje, and Dutrochet (1838). Heynsius discovered 
 the urea, and CI. Bernard (1853) the sugar in the liver, and he and Hensen (1857) found glycogen 
 in the liver. Kiernan gave a more exact description of the hepatic blood vessels (1834). Beale 
 injected the lymphatics, and Gerlach the finest bile ducts. Schwann (1844) made the first biliary 
 fistula; Demarcay particularly referred to the combination of the bile acids with soda (1838); 
 Strecker discovered the soda compounds of both acids, ,and isolated them. 
 
 Corn. Celsus mentions nutrient enemata (3-5 A. D.). Fallopius (1561) described the valvulas 
 conniventes and villi of the intestinal mucous membrane, and the nervous plexus of the mesentery. 
 The agminated glands or patches of Peyer were known to Severinus (1645). 
 
Physiology of absorption. 
 
 Fig. 193. 
 
 Scheme of intestinal absorption. LAC, lac- 
 teal; T. D., thoracic duct; P. V. and H. 
 V., portal and hepatic veins; INT., intes- 
 tine. 
 
 189. THE ORGANS OF ABSORPTION.— [As most substances in 
 the state in which they are used for food are either insoluble or diffuse but imper- 
 fectly through membranes, the whole drift of the complicated digestive processes 
 is to render these substances soluble and diffusible, and thus fit them for absorp- 
 tion ; while most of the fats are emulsionized.] 
 
 The mucous membrane of the whole intestinal tract, as far, as it is covered by a 
 single layer of columnar epithelium, i. <f.,.from the' cardiac orifice of the stomach 
 to the anus — is adapted for absorption. The 
 mouth and oesophagus, lined as they are by 
 stratified squamous epithelium, are much less 
 adapted for this purpose. Still, poisoning is 
 caused by placing potassium cyanide in the 
 mouth. 
 
 The channels of absorption in the intestinal 
 tract are (Fig. 193) — (1) the capillaries 
 [direct], and (2) the lacteals [indirect] of the 
 mucous membrane. Almost the whole of the 
 substances absorbed by the former pass into 
 the rootlets of the portal vein, and traverse the 
 liver, while those that enter the lacteals really 
 pass into lymphatics, so that the chyle passes 
 through the thoracic duct, and is poured by it 
 into the blood, where the thoracic duct joins 
 the subclavian vein. 
 
 Absorption in the Stomach. — Watery solutions of salts, grape sugar, pep- 
 tone, poisons, and in a still higher degree alcoholic solutions of poisons are 
 absorbed. The empty stomach absorbs more rapidly than one filled with food ; 
 gastric catarrh delays absorption (Quetsch). After a copious diet of milk, fatty 
 granules have been found in the protoplasm of the goblet cells (Kblliker) ; so that 
 according to this view, the goblet cells have a double function, to secrete mucus 
 and to absorb nutrients. 
 
 Small Intestines. — The greatest area of absorption is undoubtedly the small 
 intestine, especially its upper half (Landois and Lepine~), owing to the presence 
 of the valvulse conniventes and the villi. 
 
 190. STRUCTURE OF THE SMALL AND LARGE INTES- 
 TINES. — [The wall of the small intestine consists of four coats; which from 
 without inward are named serous, muscular, submucous, and mucous. 
 
 The serous coat has the same structure as the peritoneum, *'. e., a thin basis of fibrous tissue 
 covered on its outer surface by endothelium. 
 
 The muscular coat consists of a thin outer longitudinal and an inner thicker circular layer of 
 non-striped muscular fibres (Fig. 186). 
 
 The submucous coat consists of loose connective tissue containing large blood vessels and 
 nerves, and it connects the muscular with the mucous coat.] 
 
 The mucous coat is the most internal coat, and its absorbing surface is largely increased by the 
 presence of the valvulae conniventes and villi. [The valvulse conniventes are permanent folds 
 of the mucous membrane of the small intestine, arranged across the long axis of the gut. They 
 
 319 
 
320 
 
 STRUCTURE OF A VILLUS. 
 Fig. 194. 
 
 Mucous membrane of the small intestine of the dog ; the lacteals are black, and the blood-vessels lighter, a, 
 artery ; b, lymphatic ; c, plexus of capillaries in the villi ; d, lacteal ; e, Lieberkiihn's glands. 
 
 Scheme of an intestinal villus. A, transverse section of part of a villus ; a, columnar epithelium with, b, clear disk ; 
 c, goblet cell ; *, i, adenoid reticulum ; d, d t spaces within the same and containing leucocytes, e t e ; f, section of 
 the central lacteal ; B, scheme of a cell with processes supposed to be projected from its interior ; C, columnar epi- 
 thelium after the absorption of fatty granules ; D, the columnar epithelium of a villus seen from above with a 
 goblet cell in the centre. 
 
STRUCTURE OF A VILLUS. 
 
 321 
 
 pass round a half or more of the inner surface of the gut. They begin a little below the com- 
 mencement of the duodenum, and are large and well marked in the duodenum, and remain so as 
 far as the upper half of the jejunum, where they begin to become smaller, and finally disappear 
 about the lower part of the ileum.] The villi are characteristic of the small intestine, and are 
 confined to it; they occur everywhere as closely-set projections over and between the valvulse con- 
 niventes (Fig. 194). When the inner surface of the mucous membrane is examined in water, it 
 has a velvety appearance owing to their presence. [They vary in length from -fa to ^ of an inch, 
 are most numerous and largest in the upper part of the intestine, duodenum, and jejunum, where 
 absorption is most active, but they are less abundant in the ileum. Their total number has been 
 calculated at four millions, by Krause.] Each villus is a projection of the entire mucous membrane, 
 so that it contains within itself representatives of all the tissue elements of the mucosa. The orifices 
 of the glands of Lieberkiihn open between the bases of villi (Fig. 197). 
 
 Each villus, be it cylindrical or conical in shape, is covered by a single layer of columnar 
 epithelium, whose protoplasm is reticulated, and contains a well-defined nucleus with an intra- 
 nuclear plexus of fibrils. The ends of the epithelial cells directed toward the gut are polygonal, 
 and present the appearance of a mosaic (Fig. 195, D). When looked at from the side, their free 
 surface is seen to be covered with a clear, highly refractive disk or " cuticula," which is marked 
 with vertical striae. These striae were supposed by K611iker to represent pores for the absorption of 
 
 Fig. 196. 
 
 Capillary. 
 
 Artery 
 
 Cylindrical epithelium. 
 
 Disk on the epithelium. 
 
 .Vein. 
 
 Injected blood vessels of a villus. 
 
 fatty particles, but this has not been confirmed, while Brettauer and Steinach regarded them as pro- 
 duced by prisms placed side by side. 
 
 According to some observers (v. Thanhoffer), however, this clear disk is the optical expression 
 of a thinning of the cell membrane, comparable to the thickened flange around the bottom of a 
 vessel, such as is used for collecting gases. On this supposition, the upper end of each cell is open, 
 and from it there projects pseudopodia-like bundles of protoplasmic processes (Fig. 195, B). These 
 processes are supposed to be extended beyond the margin of the cell and again rapidly retracted, 
 and in so acting they are said to carry the fatty particles into the interior of the cells, much as the 
 pseudopodia of an amoeba entangles its food. [This view has not been confirmed by a sufficient 
 number of observers.] Between the epithelial cells are the so-called goblet cells (Fig. 195, C). 
 [Each goblet cell is more or less like a chalice, narrower above and below, and broad in the middle, 
 with a tapering fixed extremity. The outer part of these cells is filled with a clear substance or 
 mucigen, which, on the addition of water, yields mucus. The mucigen lies in the intervals of a 
 fine network of fibrils, which pervades the cell protoplasm, while the protoplasm, containing a glob- 
 ular or triangular nucleus, is pushed into the lower part of the cell. These goblet cells are simply 
 altered columnar epithelial cells, which secrete mucus in their interior. They are more numerous 
 under certain conditions. Not unfrequenlly in sections of the mucous membrane of the gut, after 
 it is stained with logwood, we may see a deep blue plug of mucus partly exuded from these cells. 
 21 
 
322 
 
 STRUCTURE OF A VILLUS. 
 
 When looked at from above they give the appearance seen in Fig. 195, D.] The epithelial cells 
 are shed in enormous numbers in cholera, and in poisoning with arsenic and muscarin (Bohm). 
 
 [The epithelial cells covering the villus are placed upon a layer of squamous epithelium (base- 
 ment membrane) — the sub-epithelial membrane of Debove. This basement membrane is said 
 to be connected by processes with the so-called branched cells of the adenoid tissue of the villus, 
 while it also sends up processes between the epithelial covering.] 
 
 Adenoid Tissue of Villus. — The villus itself consists of a basis of adenoid tissue, containing in 
 its centre one or more lacteals, closely invested with a few longitudinal, smooth muscular fibres, 
 derived from the muscularis mucosae, and a plexus of blood vessels. The adenoid tissue of the 
 villus consists of a reticulum of fibrils with endothelial plates at its nodes. The spaces of the ade- 
 noid tissue form a spongy network of intercommunicating channels, containing stroma cells or leuro- 
 cytes (Fig. 195, A, V, e). These leucocytes, or lymph corpuscles, have been seen to contain fatty 
 granules, and they may, perhaps, play an important part in the absorption of fatty particles. 
 
 The lymphatic, or lacteal, lies in the axis of the villus (Fig. 194, d). By some observers the 
 lacteal is regarded merely as a space in the centre of the villus, but, more probably, it has a distinct 
 wall composed of endothelial cells, with apertures or stomata here and there between the cell plat's. 
 
 Fig. 197. 
 
 Section oi the mucous membrane of the small intestine, showing Lieberkiihn's glands, a, with irregular epithelium : 
 /', villi, cut short ; c, muscularis mucosae ; (/, submucous tissue. 
 
 These stomata place the interior of the lacteal in direct communication with the spaces of the adenoid 
 tissue. It is very probable that white blood corpuscles wander out of the blood vessels of the villi 
 into the spaces of the adenoid tissue, where they become loaded with fatty granules, and pass into 
 the central lacteal. Zuwarykin and Weidersheim suppose that the leucocytes pass from the paren- 
 chyma of the villus toward the epithelial layer, and even between the epithelial cells, from which 
 they return toward the axis of the villus, laden with substances which they have taken into their 
 interior ($ 192, II). 
 
 A small artery, placed eccentrically, passes into each villus (Fig. 196). In man, it begins to 
 divide about the middle of the villus, but in animals it usually runs to the apex before it divides. 
 The capillaries resulting from the division of the artery form a fine, dense network, placed super- 
 ficially, immediately under the epithelium of the surface. The blood is carried out of a villus by 
 one or two veins (Figs. 194, 196). 
 
 Non-striped Muscular Fibres are present in villi (Henle). Some are arranged longitudinally 
 from base to apex, immediately outside the central lacteal. When they contract, they tend to empty 
 the lacteal {Briicke). A few muscular fibres are placed more superficially, and run in a more 
 transverse direction. [The longitudinal bundles of non-striped muscle in the villi are connected 
 
STRUCTURE OF A VILLUS. 
 
 323 
 
 together by oblique strands ; while the longitudinal bundles shorten the villus, the oblique fibres 
 keep the lacteal open ; thus, the parenchyma of the villus is also compressed transversely, whereby 
 the products of absorption are forced into the lacteal. The muscles are fixed, by cement, to the 
 sub-epithelial basal membrane. The muscular fibres of the villi are direct prolongations of the 
 muscularis mucosae.] 
 
 Nerves pass into the villi from Meissner's plexus, lying in the submucous coat. The nerves to 
 
 Fig. iq8. 
 
 Section of a solitary follicle of the small intestine (human), showing — a, lymph follicle covered with epithelium (6) 
 which has fallen from the villi, c ; d, Lieberkiihn's follicle; e, muscularis mucosae; _/", submucous tissue. 
 
 Fig. 199. 
 
 Diagram of a vertical section of the mucous membrane of the small intestine of a dog, showing the closed follicles, 
 
 a a ; b, muscularis mucosae. 
 
 the villi are said to have small granular ganglionic cells in their course, and they terminate partly in 
 the muscular fibres and partly in the arteries of the villi. 
 
 [On making a vertical section of the mucous membrane of the small intestine, it is seen to 
 consist of a network of adenoid tissue loaded with leucpcytes. This tissue forms its basis, and in it 
 are placed vertically, side by side — like test tubes in a stand — immense numbers of simple tubular 
 
324 
 
 SOLITARY FOLLICLES. 
 
 glands — the Crypts of Lieberkiihn (Fig. 197).] [Kultschitzki finds that the connective tissue 
 framework of the mucous membrane of the small intestine is not true adenoid tissue, but a transi- 
 tion form between the latter and loose fibrous tissue.] They open above, at the bases of the villi, 
 while their closed lower extremity reaches almost to the muscularis mucosae. Each tube consists of 
 a basement membrane, lined by a single layer of columnar epithelium, leaving a wide lumen, the 
 cells lining them being continuous with those that cover the mucous membrane. Some goblet cells 
 
 Fig. 200. 
 
 Auerbach's plexus, shown in section (human), a, ganglionic cells ; b, nerve fibres ; c t section of the circular 
 muscular fibres ; d, longitudinal muscular fibres. 
 
 are often found between the columnar epithelium. Immediately below the bases of the follicles of 
 Lieberkiihn is the muscularis mucosae, consisting of two or three narrow layers of non-striped 
 muscular fibres, arranged circularly and longitudinally. [It is continuous with the muscularis 
 mucosae of the stomach, and extends throughout the whole intestine — not as a continuous layer, 
 but as a close network of bundles of smooth muscle {Kultschitzki). It sends fibres upward into 
 the villi (Fig. 198, e).] 
 
 Fig. 201. 
 
 Epithelium. 
 
 Lieberkiihn's glands. 
 
 Muscularis mucosas. 
 
 -^Submucous coat. 
 
 Mucous membrane . ' 
 
 Capillary. 
 
 Solitary follicle. 
 
 Circular fibres. 
 Muscular coat 
 
 Longitudinal fibres. 
 
 Longitudinal section of the large intestine. 
 
 [Brunner's Glands are compound tubular glands lying in and confined to the submucous coat 
 of the duodenum. Their ducts perforate the muscularis mucosae to open on the surface. They, 
 seem to be the homologues of the pyloric glands of the stomach.] 
 
 [Solitary Follicles are small round or oval white masses of adenoid tissue, with their deeper 
 parts embedded in the sub-mucosa, and their apices projecting into the mucosa of the intestine. 
 
ABSORPTION OF THE DIGESTED FOOD. 
 
 325 
 
 Fig. 202. 
 
 They begin at the pyloric end of the stomach and are found throughout the whole intestine. They 
 consist of small masses of adenoid tissue loaded with leucocytes (Fig. 198). They are well sup- 
 plied with blood vessels (J 197), although no lymphatic vessels enter them. They are surrounded 
 by lymphatics, and, in fact, they may be said to hang into a lymph stream. The distribution of 
 solitary follicles is fairly uniform in the small intestine; their number generally increases from the 
 stomach to the large intestine ; although there are considerable variations in different individuals, 
 there seems to be the same number of solitary follicles and Peyer's patches in the infant as in the 
 adult (Passow).~\ 
 
 [Peyer's glands, or agminated glands, consist of groups of lymph follicles like the foregoing 
 (Figs. 186, 199). The masses are often more or less fused together, their bases lie in the sub-mucosa, 
 while their summits project into the mucosa, where they are 
 covered merely by the columnar epithelium of the intestine. The 
 lymph corpuscles often project between the epithelium. The 
 patches so formed have their long axis in the axis of the intestine, 
 and they are always placed opposite the attachment of the mesen- 
 tery. Like the solitary glands, they are well supplied with blood 
 vessels, while around them is a dense plexus of lymphatics or 
 lacteals. They are most abundant in the lower part of the ileum. 
 These glands are specially affected in typhoid fever.] 
 
 Nerves of the Intestine. — Throughout the whole intestinal 
 tract there exists the plexus of Auerbach (Kig. 200), lying be- 
 tween the longitudinal and circular muscular coats. This plexus 
 consists of non-medullated nerves with groups of ganglionic cells 
 at the nodes. Fibres are given off by it to the muscular coats. 
 Connected by branches with the foregoing, and lying in the sub- 
 mucosa, is the plexus of Meissner, which is much finer, the 
 meshes being wider, the nodes smaller, but also provided with 
 ganglionic cells. It supplies the muscular fibres and arteries of 
 the mucosa, including those of the villi. It also supplies branches 
 to Lieberkiihn's glands (Drasc/i). Compare Figs. 166 and 167. 
 
 [Structure of the Large Intestine. — It has four coats like 
 those of the small intestine. The serous coat has the same 
 structure as that of the small intestine. The muscular coat has 
 external longitudinal fibres occurring all round the gut, but they 
 form three Hat, ribbon-like, longitudinal bands in the csecum and 
 colon (Fig. 201). Inside this coat arethe circular fibres. The 
 sub-mucosa is practically the same as that of the small intes- 
 tine.. The mucosa is characterized by negative characters. It 
 has no villi and no Peyer's patches, but otherwise it resembles 
 structurally the small intestine, consisting of a basis of adenoid 
 tissue with the simple tubular glands of Lieberkiihn (Fig. 202). 
 These glands are very numerous and somewhat longer than those 
 of the small intestine, and they always contain far more goblet 
 cells — about ten times as many. The cells lining them are de- 
 void of a clear disk. Solitary glands occur throughout the 
 entire length of the large intestine. At the bases of Lieberkiihn's 
 glands is the muscularis mucosae. The blood vessels and 
 nerves have a similar arrangement to those in the stomach.] 
 
 [Blood Vessels. — On looking down on an opaque injection 
 of the mucous membrane of the stomach, one sees a dense mesliwork of polygonal areas of 
 unequal size, with depressions here and there. The orifices are the orifices of the gastric glands, 
 each surrounded by a capillary. A somewhat similar appearance is seen in an opaque injection of 
 the mucous membrane of the large intestine, but in the latter the meshwork is uniform, all the 
 orifices (of Lieberkiihn's glands) being of the same size.] 
 
 191. ABSORPTION OF THE DIGESTED FOOD.— The physical 
 forces concerned are, endosmosis, diffusion and filtration. 
 
 All the constituents of the food, with the exception of the fats, which in part are changed into a 
 fine emulsion, are brought into a state of solution by the digestive processes. These substances 
 pass through the walls of the intestinal tract, either into the blood vessels of the mucous membrane 
 or into the beginning of the lymphatics. In this passage of the fluids two physical processes come 
 into play — endosmosis and diffusion, as well as filtration. 
 
 I. Endosmosis and diffusion occur between two fluids which are capable of forming an inti- 
 mate mixture wich each other, e. g., hydrochloric acid and water, but never between two fluids 
 which do not form a perfect mixture, such as oil and water. If two fluids capable of mixing with 
 each other, but of different compositions, be separated from each other by means of a septum with 
 physical pores (which occur even in a homogeneous membrane), an exchange of the constituents 
 
 Lieberkiihn's gland, from 
 intestine (dog). 
 
 large 
 
326 
 
 FORCES CONCERNED IN ABSORPTION. 
 
 Fig. 203. 
 R 
 
 in the fluids occurs until both fluids have the same composition. This exchange of fluids is termed 
 endosmosis or diosmosis. 
 
 If we remember that within the intestinal tract there are relatively concentrated solutions of those 
 substances which have been brought into solution by the digestive juices— peptone, sugar, soaps and 
 solutions of the salts — while separated from these by the porous mucous 
 membrane and the walls of the blood and lymph capillaries is the blood, 
 which contains relatively less of these substances, it is clear that an endos- 
 motic current must set in toward the blood and lymph vessels. 
 
 Diffusion. — If the two mixible fluids are placed in a vessel, the one fluid 
 over the other, but without being separated by a porous septum, an exchange 
 of the particles of the fluids also occurs, until the whole mixture is of uniform 
 composition. This process is called diffusion. 
 
 Conditions Influencing Diffusion. — Graham's investigations showed 
 that the rapidity of diffusion is influenced by a variety of conditions : ( I ) 
 The nature of the fluids themselves is of importance ; acids diffuse most 
 rapidly ; the alkaline salts more slowly ; and most slowly, fluid albumin, gela- 
 tin, gum, dextrin. These last do not crystallize, and do not form true solu- 
 tions. (2) The more concentrated the solutions, the greater the diffusion. 
 (3) Heat accelerates, while coal retards, the process. (4) If a solution of a 
 body which diffuses with difficulty be mixed with an easily diffusible one, the 
 former diffuses with still greater difficulty. (5) Dilute solutions of several 
 substances diffuse into each other without any difficulty, but if concentrated 
 solutions are employed, the process is retarded. (6) Double salts, one con- 
 stituent of which diffuses more readily than the other, may be chemically 
 separated by diffusion. 
 
 Endosmometer. — The exchange of the fluid particles takes place inde- 
 pendently of the hydrostatic pressure. Fig. 203 represents an endosmometer. 
 A glass cylinder is filled with distilled water, and into this is placed a flask, 
 J, without a bottom, instead of which a membrane, m, is tied on. A glass 
 tube, R, is fixed firmly by means of a cork into the neck of the flask. The 
 flask is filled up to the lower end of the tube with a concentrated salt solu- 
 tion, and is then placed in the cylindrical vessel until both fluids are on the 
 same level, j,. The fluid in the tube, R, soon begins to rise, because water 
 passes through the membrane into the concentrated solution in the flask, and 
 this independently of the hydrostatic pressure. Particles of the concentrated 
 salt solution pass into the cylinder and mix with the water, F. These out- 
 going and ingoing currents continue until the fluids without and within J are 
 of uniform composition, whereby the fluid in R always stands higher [e. g., at y), while it is lowered 
 in the cylinder. The circumstance of the level of the fluid within the tube being so high and 
 remaining so, is due to the fact that the pores in the membrane are too fine to allow the hydrostatic 
 pressure to act through them. 
 
 Endosmotic Equivalent. — Experiment has shown that equal weights of different soluble sub- 
 stances attract different amounts of distilled water through the membrane, i. e., a known weight of 
 a soluble substance (in the flask) can be exchanged by endosmosis for a definite weight of water. 
 The term endosmotic equivalent indicates the weight of distilled water that passes into the flask of 
 the endosmometer, in exchange for a known weight of the soluble substance {Jolly). For I grm. 
 alcohol 4.2 grms. water were exchanged ; while for 1 grm. NaCl 4.3 grms. water passed into the 
 endosmometer. The following numbers give the endosmotic equivalent of — 
 
 *T 
 
 ■"-''■ J[ 
 
 Endosmometer for os- 
 
 Acid potassium sulphate =■ 2.3 
 
 Common salt = 4.3 
 
 Sugar = 7-1 
 
 Sodium sulphate .... . . =n.6 
 
 Magnesium sulphate = 11.7 
 
 Potassium sulphate = 12.0 
 
 Sulphuric acid = 0.39 
 
 Potassium hydrate = 215.0 
 
 The amount of the substance which passes through the membrane into the water of the cylinder 
 is proportional to the concentration of the solution \Vierordt). If the water in the cylinder, there- 
 fore, be repeatedly renewed, the endosmosis takes place more rapidly and the process of equilibra- 
 tion is accelerated. The larger the pores of the membrane, and the smaller the molecules of the 
 substance in solution, the more rapid is the endosmosis. Hence, the rapidity of the endosmosis of 
 different substances varies — thus, the rapidity of sugar, sodium sulphate, common salt, and urea is 
 in the ratio of I : 1.1 : 5 : 9.5 (Eckhard, Hoffmann). 
 
 The endosmotic equivalent is not constant for each substance. It is influenced by — ( I ) The tem- 
 perature, which, as it increases, generally increases the endosmotic equivalent. (2) It also varies 
 with the degree of concentration of the osmotic solutions, being greater for dilute solutions of the 
 substances (C. Ludwig and Cloetta). 
 
 If a substance other than water be placed in the cylinder, an endosmotic current occurs on both 
 sides until complete equality is obtained. In this case, the currents in opposite directions disturb 
 each other. If two substances be dissolved in the water in the flask at the same time, they diffuse 
 
ABSORPTIVE ACTIVITY OF THE INTESTINAL WALL. 327 
 
 into water without affecting each other. (3) It also varies with membranes of varying porosity. 
 Common salt, which gives an endosmotic equivalent with a pig's bladder = 4.3, gives 6.4 when an 
 ox bladder is used; 2.9 with a swimming bladder; and 20.2 with a collodion membrane {Harzer). 
 Colloids. — There is a number of fluid substances which, on account of the great size of their 
 molecules, do not pass, or pass only with difficulty, through the pores of a membrane impregnated 
 with gelatinous bodies, which diffuse slowly. These substances are not actually in a true state of 
 solution, but exist in a very dilute condition of imbibition. Such substances are the fluid proteids, 
 starches, dextrin, gum, and gelatin. These diffuse when no septum is present, but diffuse with 
 difficulty or not at all through a porous septum. Graham called these substances colloids, because 
 when concentrated, they present a glue-like or gelatinous appearance ; further, they do not crystal- 
 lize, while those substances which diffuse readily are crystalline, and are called crystalloids. 
 Crystallizable substances may be separated from non-crystallizable by this process, which Graham 
 called dialysis. Mineral salts favor the passage of colloids through membranes (Baranetzky). 
 
 That Endosmosis takes place in the intestinal tract, through the mucous 
 membrane and the delicate membranes of the blood and lymph capillaries, can- 
 not be denied. On the one side of the membrane, within the intestine, are the 
 highly diffusible peptones, sugar, and soaps, and within the blood vessels are the 
 colloids which are scarcely diffusible, e.g., the proteids of blood and lymph. 
 
 II. Filtration is the passage of fluids through the coarse intermolecular pores of a membrane, 
 owing to pressure. The greater the pressure, and the larger and more numerous the pores, the 
 more rapidly does the fluid pass through the membrane ; increase of temperature also accelerates it. 
 Those substances which are imbibed by the membrane filter most rapidly, so that the same sub- 
 stance filters through different membranes with varying rapidity. The filtration is usually slower, 
 the greater the concentration of the fluid. The filter has the property of retaining some of the sub- 
 stances from the solution passing through it, c. g., colloid substances — or water (in dilute solutions 
 of nitre). In the former case, the filtrate is more dilute, in the latter more concentrated than before 
 filtration. Other substances filter without undergoing any change of concentration. Many mem- 
 branes behave differently, according to which surface is placed next to the fluid; thus the shell- 
 membrane of an egg permits filtration only from without inward ; [and the same is true to a much less 
 extent with filter paper ; the smooth side of the filter paper ought always to be placed next the fluid 
 to be filtered. The intact skin of the grape prevents the entrance of fungi]. There is a similar 
 difference with the gastric and intestinal mucous membrane. 
 
 [Filtration of Albumin. — Runeberg finds that the amount of albumin in pathological transuda- 
 tions varies with ( 1 ) the capillary area, being least in oedema of the subcutaneous tissue. (2) The 
 presence or absence of inflammatory processes in the vascular wall, non-inflammatory pleuritic effu- 
 sion containing 2 per cent., and inflammatory 6 per cent., of albumin. (3) The condition and 
 amount of albumin in the blood. The amount of albumin in the transudate never reaches, although 
 it sometimes approaches, that in blood. In ascites in general dropsy the amount is .03 to .04 per 
 cent. (4) The duration of the transudation. (5) Perhaps the blood pressure and the condition 
 of the circulation.] 
 
 [By using numerous layers of filter paper, many colloids and crystalloids are retained in the filter, 
 e.g., haemoglobin, albumin, and many coloring matters, especially anilin colors, the last being 
 arrested by glass-wool (ICrysins&i).~\ 
 
 Filtration of the soluble substance may take place from the canal of the digest- 
 ive tract when — (1) The intestine contracts and thus exerts pressure upon its 
 contents. This is possible when the tube is narrowed at two points, and the mus- 
 culature between these two points contracts upon the fluid contents. (2) Filtra- 
 tion, under negative pressure, may be caused by the villi (Briicke). When 
 the villi contract energetically, they empty their contents toward the blood and 
 lymph vessels. The lymph vessels remain empty, as the chyle is prevented from 
 passing backward into the origin of the lacteal within the villi, owing to the 
 presence of numerous valves in the lymphatics. When the villi pass again into 
 the relaxed condition, they again become filled with fluids from the intestinal 
 contents. 
 
 192. ABSORPTIVE ACTIVITY OF THE INTESTINAL 
 WALL. — The process of digestion produces from the food partly solutions and 
 partly finely divided emulsions, whose fine particles are said to be surrounded by 
 an albuminous envelope, the haptogen membrane [of Ascherson], whereby these 
 particles become more stable. Unchanged colloid substances may also be present 
 in the intestinal tract. 
 
328 ABSORPTION OF SOLUBLE CARBOHYDRATES AND PEPTONES. 
 
 I. Absorption of Solutions. — True solutions undoubtedly pass by endos- 
 mosis into the blood vessels and lymphatics of the intestinal walls, but numerous 
 facts indicate that the protoplasm of the cells of the tube take an active part in 
 the process of absorption. The forces concerned have not as yet been referred 
 simply to physical and chemical processes. 
 
 (i) The Inorganic substances. — Water and the soluble salts necessary 
 for nutrition are easily absorbed, the latter especially by the blood- and lymph 
 vessels. When saline solutions pass by endosmosis into the vessels, water must 
 pass from the intestinal vessels into the intestine. The amount of water, however, 
 is small, owing to the small endosmotic equivalent of the salts to be absorbed. 
 More salts are absorbed from concentrated than from dilute solutions (Funke). If 
 large quantities of salts, with a high endosmotic equivalent, are introduced into 
 the intestine, e.g., magnesium or sodium sulphate, these salts retain the water ne- 
 cessary for their solution, and thus diarrhoea is caused (Poiseuille, Buchheini). 
 Conversely, when these substances are injected into the blood a large quantity of 
 water passes from the intestine into the blood, so that constipation occurs, owing 
 to dryness of the intestinal contents (Aubert). [M. Hay concludes from his ex- 
 periments (§ 161), that salts, when placed in the intestines, do not abstract water 
 from the blood, or are themselves absorbed, in virtue of an endosmotic relation 
 being established between the blood and the saline solution in the intestines. Ab- 
 sorption is probably due to the filtration and diffusion, or processes of inhibition 
 other than endosmosis, as yet little understood. The result obtained by Aubert, 
 which is not constant, is mostly caused by the great diuresis which the injected 
 salts excites.] 
 
 Numerous inorganic substances, which do not occur in the body, are absorbed by endosmosis 
 from the intestine, e.g., dilute sulphuric acid, potassium iodide, chlorate, and bromide, and many 
 other salts. 
 
 (2) The soluble carbohydrates, such as the sugars, of which the chief rep- 
 resentatives are dextrose and maltose, with a relatively high endosmotic equiva- 
 lent. Cane sugar is changed by a special ferment into invert sugar (§ 183, 5). 
 Absorption appears to take place somewhat slowly, as only very small quantities 
 of grape sugar are found in the chyle vessels or the portal vein, at any time. 
 According to v. Merings the sugar passes from the intestine into the rootlets of the 
 portal vein ; dextrin also occurs in the portal vein. When the blood of the portal 
 vein is boiled with dilute sulphuric acid, the amount of sugar is increased (Nau- 
 ny?i). The amount of sugar absorbed depends upon the concentration of its solu- 
 tion in the intestine ; hence the amount of sugar in the blood is increased after a 
 diet containing much of this substance ( C. Schmidt and v. Becker), so that it may 
 appear in the urine; in which case the blood must contain at least 0.6 per cent, 
 of sugar (Lehmann and Uhle). A small amount of cane sugar has also been 
 found in the blood (CI. Bernard, Hoppe-Seyler). The sugar is used up in the 
 bodily metabolism; some of it is, perhaps, oxidized in the muscles (Zimmer). 
 [Compare effects of injecting grape sugar into the blood (§ 176).] 
 
 (3) The peptones have a small endosmotic equivalent (Funke), a 2 to 9 per 
 cent solution = 7 to 10. Owing to their great diffusibility they are readily absorbed, 
 and they are the chief representatives of the proteids which - are absorbed. The 
 amount absorbed depends upon the concentration of the solution in the intestine. 
 They pass into the blood vessels (Schmidt- Miilheim). When animals are fed on 
 peptones (with the necessary fat or sugar), they serve to maintain the body weight 
 (Maly, Plbsz and Gyorgyai). Only minute quantities of peptone have as yet been 
 found in the blood (Drosdorff) ; hence, it is assumed, either that they are rapidly 
 converted into true albuminous bodies, or that, in part at least, they undergo 
 further decompositions, with which we are as yet unacquainted. As, however, 
 they can compensate for the total metabolism of the proteids within the body, we 
 must assume that they are converted into proteids. Hofmeister supposes that the 
 
ABSORPTION OF FATTY PARTICLES. 329 
 
 leucocytes absorb the peptones and act as their carriers, much as the red corpus- 
 cles are oxygen carriers. They carry the peptones into the mucous membrane of 
 the stomach and small intestine, which are very rich in peptone at the fourth hour 
 of digestion. It is asserted by Salivoli that the mucous membrane possesses the 
 property of changing peptone into albumin. Only a part of the peptone passes 
 unchanged into the blood, and disappears from it after its passage through the 
 tissues. 
 
 [Injection of Peptone into Blood — When peptone is injected into the blood of an animal, 
 within twenty minutes thereafter no trace of the peptone is to be found in the blood, although it has 
 not been excreted by any of the organs. Peptone so injected prevents the blood of the dog (not of 
 the rabbit or pig) from coagulating (p. 48). Fano asserts that the peptone is taken up by the red 
 blood corpuscles, which thus become of greater specific gravity, and change it into globulin. After 
 three or more hours the corpuscles return the globulin to the blood, so that the corpuscles represent 
 a reserve store of proteid.] 
 
 (4) Unchanged true proteids filter with great difficulty, and much albumin 
 remains upon the filter. On account of their high endosmotic equivalent they 
 pass with extreme difficulty, and only in traces, through membranes. Neverthe- 
 less, it has been conclusively proved that unchanged proteids can be absorbed 
 {Brucke), e.g., casein, soluble myosin, alkali albuminate, albumin mixed with 
 common salt, gelatin {Voit, Bauer, Eichhorsi). They are absorbed even from the 
 large intestine (Cserny and Latschenberger), although the human large intestine 
 cannot absorb more than 6 grms. daily. But the amount of unchanged proteids 
 absorbed is always very much less than the amount of peptone. 
 
 Egg albumin without common salt, syntonin, serum albumin, and fibrin are not absorbed {Eich- 
 horsi'). Landois observed in the case of a' young man who took the whites of 14 to 20 eggs along 
 with NaCl, that albumin was given off by the urine for 4 to 10 hours thereafter. The amount of 
 albumin given off rose until the third day and ceased on the fifth day. The more albumin that was 
 taken the sooner the albuminuria appeared and the longer it lasted. The unchanged egg albumin 
 reappeared in the urine. If egg albumin be injected into the blood, part of it reappears in the 
 urine ($ 41, 2) (Stokvis, Lehmann). 
 
 (5) The soluble fat soaps represent only a fraction of the fats of the food 
 which are absorbed ; the greater part of the neutral fats being absorbed in the 
 form of very fine particles — as an emulsion (§ 192, II). The absorbed soaps have 
 been found in the chyle, and as the blood of the portal vein contains more soaps 
 during digestion than during hunger, it has been assumed that the soaps pass into 
 the intestinal blood capillaries. The investigations of Lenz, Bidder and Schmidt 
 render it probable that the organism can absorb only a limited amount of fat 
 within a given period ; the amount perhaps bears a relation to the amount of bile 
 and pancreatic juice. The maximum per 1 kilo, (cat) was 0.6 grm. of fat per 
 hour. 
 
 It appears as if the soaps reunite with glycerine in the parenchyma of the villi, 
 to form neutral fats, as Perewoznikoff and Will found, after injecting these two 
 ingredients into the intestinal canal. C. A. Ewald found that fat was formed 
 when soaps and glycerine were brought into contact with the fresh intestinal 
 mucous membrane. Perhaps this is the explanation of the observation of Bruch, 
 who found fatty particles within the blood vessels of the villi. 
 
 Absorption of other Substances. — Of soluble substances which are introduced into the intes- 
 tinal canal, some are absorbed and others are not. The following are absorbed : alcohol, part of 
 which appears in the urine (not in the expired air), viz., that part which is not changed into C0 2 
 and H 2 0, within the body; tartaric, citric, malic, and lactic acids; glycerine, inulin (Komanos) ; 
 gum and vegetable mucin, which give rise to the formation of glycogen in the liver. 
 
 Among coloring matters, alizarin (from madder), alkannet, indigo-sulphuric acid, and its soda 
 salt are absorbed ; hsematin is partly absorbed, while chlorophyll is not. Metallic salts seem to 
 be kept in solution by proteids, are perhaps absorbed along with them, and are partly carried by 
 the blood of the portal vein to the liver (ferric sulphate has been found in chyle). Numerous 
 poisons are very rapidly absorbed, e. g., hydrocyanic acid after a few seconds ; potassium cyanide 
 has been found in the chyle. [If salts (KI, sulphocyanide of ammonium) be injected into a liga- 
 
330 ABSORPTION OF FATTY PARTICLES. 
 
 hired loop of intestine (dog, cat, rabbit), these substances are absorbed both by the blood and lymph 
 Vessels, and in both nearly simultaneously (JC. B. Lekmann).~\ 
 
 II. Absorption of the smallest particles. — The largest amount of the fats 
 is absorbed in the form of a milk like emulsion, formed by the action of the 
 bile and the pancreatic juice, and consisting of excessively small granules of uni- 
 form size (§ 170, III ; § 181). The fats themselves are not chemically changed, 
 but remain as undecomposed neutral fats. The particles seem to be surrounded 
 by a delicate albuminous envelope, or haptogen membrane, partly derived from 
 the pancreatic juice [probably from its alkali albuminate]. The villi of the small 
 intestine are the chief organs concerned in the absorption of the fatty emulsion, 
 but the epithelium of the stomach and that of the large intestine also take a part. 
 The fatty granules are recognized in the villi — (1) Within the delicate canals? 
 (§ 190) in the clear band of the epithelium (Kolliker). [It is highly doubtful if 
 the vertical lines seen in the clear disk of the epithelium of the intestine are due 
 to pores.] (2) The protoplasm of the epithelial cells is loaded with fatty granules 
 of various sizes during the time of absorption, while the nuclei of the cells remain 
 free, although, from the amount of fat within the cells, it is often difficult to dis- 
 tinguish them. (3) The granules pass into the spaces of the parenchyma of the 
 villi ; these spaces communicate freely with each other. (4) The origin of the 
 lacteal in the axis of the villus is found to be filled with fatty granules. The 
 amount of fat in the chyle of a dog, after a fatty meal, is 8 to 10 per cent., while 
 the fat disappears from the blood within thirty hours. 
 
 Forces concerned. — With regard to the forces concerned in the absorp- 
 tion of fats, v. Wistinghausen proved, that when a porous membrane is moist- 
 ened with bile, the passage of fatty particles through it is thereby facilitated,, but 
 this fact alone does not explain the copious and rapid absorption of fats. It is 
 possible that the protoplasm of the epithelial cells is actively concerned in the 
 process, and that it takes the particles into its interior. Perhaps a fine proto- 
 plasmic process is thrown out by these cells, just as pseudopodia are thrown out 
 and retracted by lower organisms. It is possible that absorption may take place 
 through the open mouths of the goblet cells. The protoplasm of the epithelial 
 cells is in direct communication with the numerous protoplasmic lymph cells within 
 the reticulum of the villi, so that the particles may pass into these, and from them 
 through the stomata (?) between the endothelial cells into the central lacteal of the 
 villus. According to this view, the absorption of fatty particles, and perhaps also 
 the absorption of true proteids, is due to an active vital process, as indicated by 
 the observations of Briicke and v. Thanhoffer. This view is suported by the ob- 
 servation of Griinhagen, that the absorption of fatty particles in the frog is most 
 active at the temperature at which the motor phenomena of protoplasm are most 
 lively. That it is due to simple filtration alone is not a satisfactory explanation, 
 for the amount of fatty particles in the chyle is independent of the amount of 
 water in it. If absorption was chiefly due to filtration, we would expect that there 
 would most probably be a direct relation between the amount of water and fat 
 (Ludwig and Zawilsky). [The observations of Watney have led him to suppose 
 that the fatty particles do not pass through the cell protoplasm to reach the lacteal, 
 but that they pass through the cement substance between the epithelial cells cover- 
 ing a villus. If this view be correct, the absorbing surface is thereby greatly di- 
 minished.] 
 
 [Zuwarykin, and also Schafer, suggest that the leucocytes, which have been 
 observed between the columnar cells of the villi of the small intestine, are carriers 
 of at least part of the fat from the lumen of the gut to the lacteal ; they also, 
 perhaps, alter it for further use in the economy (p. 322). According to Zuwa- 
 rykin, Peyer's patches, in the rabbit, seem to be especially active in the absorp- 
 tion of fat, so that he attaches great importance to the leucocytes of the adenoid 
 tissue in the absorption of fat.] 
 
FEEDING WITH "NUTRIENT ENEMATA." 331 
 
 The activity of the cells of the intestine with pseudopodial processes may be studied in the intes- 
 tinal canal of Distomum hepaticum. Soramer has figured these pseudopodial processes actively ■ 
 engaged in the absorption of panicles from the intestine. Spina observed that the intestinal epi- 
 thelium of the larvas of flies shortened when they were stimulated with electricity, and absorbed 
 fluid from the intestinal canal. The cells of the villi of the frog also react to electrical stimulation. 
 The increase in the size of the cells occurs simultaneously with the contraction of the intestine. 
 Spina also supports the view that the cells, by virtue of their activity, possess the property of absorb- 
 ing fluid from the intestinal contents, and again giving it up. An exchange of fluids in the opposite 
 direction never takes place. 
 
 The statements of former observers, that particles of charcoal, pigments, and even mammalian 
 blood corpuscles (in the frog), were absorbed by the epithelial cells of the intestine, and passed into 
 the blood, are erroneous. Even for the absorption of completely fluid substances, endosmosis and 
 filtration seem to be scarcely sufficient. An active participation of the protoplasm of the cells seems 
 here also — in part, at least — to be necessary, else it is difficult to explain how very slight disturbances 
 in the activity of these cells— e.g., from intestinal catarrh — cause sudden variations of absorption, 
 and even the passage of fluids into the intestine. 
 
 If absorption was due to diffusion alone, when alcohol is injected into the intestine, water ought 
 to pass into the intestine, but this does not occur. Brieger found that the injection of a 0.5 to I 
 per cent, solution of salts into a ligatured loop of intestine did not cause water to pass into the intes- 
 tine; but it appeared when a 20 per cent, solution was injected. 
 
 193. INFLUENCE OF THE NERVOUS SYSTEM.— With regard 
 
 to the influence of the nervous system upon intestinal absorption we know very- 
 little. After extirpation of the semilunar ganglion {Budge), as well as after sec- 
 tion of the mesenteric nerves (Moreaii), the intestinal contents become more fluid 
 and are increased in amount (§ 183). This may be partly due to diminished 
 absorption. V. Thanhoffer states that he observed the protrusion of threads from 
 the epithelial cells of the small intestine only after the spinal cord, or the dorsal 
 nerves, had been divided for some time. 
 
 [Matthew Hay injected saline solutions directly into the exposed intestine. He found that a 20 
 per cent, solution of sulphate of soda always excites a profuse secretion, but that a 10 per cent, 
 solution only does so — or, rather, that it only increases in bulk, when injected in sufficient quantity 
 — a certain weight of salt failing to increase the bulk of the fluid secretion when dissolved as a 10 
 per cent, solution, but exciting a profuse secretion when forming a 20 per cent, solution. Secretion, 
 he has reason to believe, is active in both — perhaps, almost equally active; but absorption is greatly 
 impeded in the case of the concentrated salt, by its injurious action on the absorptive mechanism of 
 the mucous membrane. Moreau has recently maintained that, under such circumstances, there is, 
 actually, no absorption; but Hay has disproved this, by observing that strychnia injected into a loop 
 of intestine containing the concentrated salt, still causes death, although after an interval three times 
 longer than when the loop contains a 10 per cent, solution of the salt. Hay has also observed that 
 the local effect of a ligature applied to the intestine is to excite secretion from the mucous membrane 
 in its immediate vicinity, and, therefore, add to the bulk of the saline solution; whereas, the 
 reflex effect of a ligature, as exercised through the nervous system, is to diminish the quantity of 
 the secreted fluid in a remote portion of the intestine,, probably by stimulating and accelerating 
 absorption. Division of the vagi does not affect the nature or the quantity of the secretion.] 
 
 194. FEEDING WITH "NUTRIENT ENEMATA."— In cases where food cannot be 
 taken by the mouth, e. g., in stricture of the oesophagus, continued vomiting, etc., food is given per 
 rectum (Ce/sus, 3-5 A.D.). As the digestive activity of the large intestine is very slight, fluid food 
 ought, to be given in a condition ready to be absorbed, and this is best done by introducing it into 
 the rectum through a tube with a funnel attached, and allowing the food to pass in slowly by its 
 own weight. The patient must endeavor to retain the enema as long as possible. When the fluid 
 is slowly and gradually introduced, it may pass above the ileo-caecal valve. 
 
 Solutions of grape sugar, and, perhaps, a small amount of soap solution, are useful ; and among 
 nitrogenous substances, the commercial flesh-, bread- or milk peptones of Sanders-Ezn, Adam- 
 kiewicz, in Germany, and Darby's fluid meat, and Carnrick's beef peptonoids in this country, 
 are to be recommended. The amount of peptone required is 1 . 1 1 grms. per kilo, of body weight 
 (Catillon); less useful are buttermilk, egg albumin, with common salt. Leube uses a mixture of 
 150 grms. flesh, with 50 grms. pancreas and 100 grms. water, which he slowly injects into the rectum, 
 where the proteids are peptonized and absorbed. [Peptonized food prepared after the method of 
 Roberts is very useful (§ 172).] The method of nutrient enemata only permits imperfect nutrition, 
 and, at most, only % of the proteids necessary for maintaining the metabolism of the body is ab- 
 sorbed (v. Voit, Bauer). [Horace Dobell recommends that a "^ lb of cooked beef or mutton be 
 grated, and to it added 20 grms. of pancreas powder and the same of pepsin. Mix the whole in a 
 warm mortar, and add a tablespoonful of brandy and warm water, sufficient to make a semi-fluid 
 mass, which is to be injected into the rectum.] 
 
332 ORIGIN OF THE LYMPHATICS. 
 
 195. CHYLE VESSELS AND LYMPHATICS.— Lymphatics.— Within the tissues of 
 the body, and even in those tissues which do not contain blood vessels, e.g , the cornea, or in those 
 which contain few blood vessels, there exists a system of vessels or channels which contain the 
 juices of the tissues, and within these vessels the fluid always moves in a centripetal direction. 
 These canals arise within the tissues in a variety of ways, and unite in their course to form delicate, 
 and afterward thicker, tubes, which, ultimately, terminate in two large trunks which open at the 
 junction of the jugular and subclavian veins; that on the left side is the thoracic duct, and that on 
 the right, the right lymphatic trunk. 
 
 Lymph. — With regard to the lymph and its movements in different organs, it 
 is to be noticed that this occurs in different ways in different places. (1) In 
 many tissues, the lymphatics represent the nutrient channels, by which the 
 fluid which transudes through the neighboring vessels is distributed, as in the 
 cornea and in many connective tissues. (2) In many tissues, as in glands, e.g., 
 the salivary glands (Gianuzzi) and the testis, the lymph spaces are the chief 
 reservoirs for fluid, from which the cells, during the act of secretion, derive 
 the fluid necessary for that process. (3) The lymphatics have the general func- 
 tion of collecting the fluid which saturates the tissues, and carrying it back again 
 to the blood. The capillary blood system may be regarded as an irrigation 
 system, which supplies the tissues with nutrient fluids, while the lymphatic system 
 may be regarded as a drainage apparatus, which conducts away the fluids that 
 have transuded through the capillary walls. Some of the decomposition products 
 of the tissues — proofs of their retrogressive metabolism — become mixed with the 
 lymph stream, so that the lymphatics are, at the same time, absorbing vessels. 
 Substances introduced into the parenchyma of the tissues in other ways — e.g., by 
 subcutaneous injection — are partly absorbed by the lymphatics. A study of these 
 conditions shows that the lymphatic system represents an appendix of the blood- 
 vascular system, and, further, that there can be no lymph system when the 
 blood stream is completely arrested ; it acts only as a part of the whole, and with 
 the whole. 
 
 Lacteals. — When we speak of the lymphatics proper as against the chyle ves- 
 sels or lacteals, we do so from anatomical reasons, because the important and con- 
 siderable lymphatic channels coming from the whole of the intestinal tract are, 
 in a certain sense, a fairly independent province of the lymphatic vascular area, 
 and are endowed with a high absorptive activity, which, from ancient times, has 
 attracted the notice of observers. The contents of the chyle vessels or lacteals 
 are mixed with a large amount of fatty granules, giving the chyle a white color, 
 which distinguishes them at once from the clear, watery contents of the true 
 lymphatics. From a physiological point of view, however, the lacteals must be 
 classified with the lymphatics, for, as regards their structure and function, they are 
 true lymphatics, and their contents consist of true lymph mixed with a large 
 amount of absorbed substances, chiefly fatty granules. [The contents of the lac- 
 teals are white only during digestion, at other times they are clear, like lymph.] 
 
 196. ORIGIN OF THE LYMPHATICS.— The mode of origin of the 
 lymphatics varies within the different tissues. The following modes are known : — 
 
 I. Origin in Spaces. — Within the connective tissues (connective tissue proper, bone) are 
 numerous stellate, irregular, or branched spaces, which communicate with each other by numerous 
 tubular processes (Fig. 204, s) ; in these communicating spaces lie the cellular elements of these 
 tissues. These spaces, however, are not completely filled by the cells, but an interval exists be- 
 tween the body of the cell and the wall of the space, which is greater or less according to the con- 
 dition of movement of the protoplasmic cell. These spaces are the so-called "juice canals " or 
 " saft canalchen," and they represent the origin of the lymphatic vessels (v. Recklinghausen). As 
 they communicate with neighboring spaces, the movement of the lymph is provided for. The cells 
 which lie in the spaces, and which were formerly but erroneously regarded by Virchow as the ori- 
 gins of the lymphatics, exhibit amoeboid movements. Some of these cells remain permanently each 
 in its own space, within which, however, it may change its form — these are the so-called " fixed " 
 connective-tissue corpuscles, and bone corpuscles — while others merely wander or pass into these 
 spaces, and are called " wandering cells," or " leucocytes; " but the latter are merely lymph cor- 
 puscles, or colorless blood corpuscles which have passed out of the blood vessels into the origin of 
 
ORIGIN OF THE LYMPHATICS. 
 
 333 
 
 the lymphatics. These cells exhibit amoeboid movements. These spaces communicate with the small 
 tubular lymphatics — the so-called lymph capillaries (L). The spaces lie close together where they 
 pass into a lymph capillary (a). The lymph capillary, which is usually of greater diameter than 
 the blood capillary, generally lies in the middle of the space within the capillary arch (B). The 
 finest lymphatics are lined by a layer of delicate, nucleated endothelial cells (?, e), with characteristic 
 sinuous margins, whose characters are easily revealed by the action of silver nitrate (Fig. 205, 
 L). This substance blackens the cement substance which holds the endothelial cells together. Be- 
 tween the endothelial cells are small holes, or stomata, by means of which the lymph capillaries 
 communicate (at x) with the juice canals. 
 
 It is assumed that the blood vessels communicate with the juice canals {J. Ar- 
 nold, Thoma, Uskoff), and that fluid passes out of the thin-walled capillaries, 
 through their stomata, into these spaces (§ 65). This fluid nourishes the tissues, 
 the tissues take up the substances appropriate to each, while the effete materials 
 pass back into the spaces, and from these reach the lymphatics, which ultimately 
 discharge them into the venous blood. 
 
 Whether the cells within these spaces are actively concerned in the pouring out of the blood 
 
 Fig. 204. 
 
 Origin of lymphatics from the central tendon of the diaphragm of a rabbit (semi-diagrammatic) ; j, the juice 
 canals, communicating at x with the lymphatics ; a, origin of the lymphatics by the confluence of several juice 
 canals. The tissue has been stained with nitrate of silver. 
 
 plasma, or take part in its movement, is matter for conjecture. We can imagine that by contracting 
 their body, after it has been impregnated with fluid, this fluid may be propelled from space to space 
 toward the lymphatics. The leucocytes wander through these spaces until they pass into the 
 lymphatics. Fine particles which are contained in these spaces— «.£-., after tattooing the 
 skin, and even fatty particles after inunction — are absorbed by the leucocytes, and carried by them 
 to other parts of the body. [The pigment particles used to tattoo the finger are usually found within 
 the first lymphatic gland at the elbow.] 
 
 After what has been said regarding the passage of colorless blood corpuscles 
 through the stomata of the blood capillaries, or through the walls of the smaller 
 blood vessels (§ 95), the passage of cellular elements from the blood vessels into 
 the origin of the lymphatics is to be considered as a normal process (E. Hering). 
 Granular coloring matter passes from the blood into the protoplasmic body of the 
 cells within the lymph spaces ; and only when the granular pigment is in large 
 amount, does it appear as a granular injection in the branches of the juice spaces 
 {Uskoff). 
 
334 
 
 PERIVASCULAR SPACES. 
 
 (2) The origin of lymphatics within villi — i. e., of the chyle vessel or lacteal — has been de- 
 scribed (§ 190). The central lacteal communicates with the lacunar interstitial spaces in the ade- 
 noid tissue of the villus, and this again with the protoplasmic body of the epithelial cells. It is 
 assumed that the lymph corpuscles, which lie in the meshes of the adenoid tissue, pass into the 
 
 Fig. 205. 
 
 Central tendon of the diaphragm of the rabbit, stained with silver nitrate and viewed from the pleural side. L, 
 lymphatic with its sinuous endothelium; c t cells of the connective tissue brought into view by the silver 
 nitrate. 
 
 central lacteal (His), while new cells are continually passing out of the blood capillaries of the 
 villi into the tissue, where they perhaps undergo increase through division. 
 
 (3) Origin of lymphatics in perivascular spaces (Fig. 206). — The smallest blood vessels of 
 bone the central nervous system, retina, and the liver, are completely surrounded by wide lymph- 
 
 Fig. 206. 
 
 Fig. 207. 
 
 Perivascular lymphatics. A, aorta of tortoise ; 
 B, artery from the brain. 
 
 Stomata from the great lymph-sac of a frog. 
 a, stoma open ; b, half closed ; c, closed. 
 
 atic tubes, so that the blood vessels are completely bathed by a lymph stream. In the brain these 
 lymphatics are partly composed of delicate connective-tissue fibres, which traverse the lymph space 
 and become attached to the wall of the included blood vessel (Roth). Fig. 206, B, represents a 
 transverse section of a small blood vessel, B, from the brain ; / is the divided perivascular space. 
 
LYMPH FOLLICLES. 
 
 335 
 
 This space is called the perivascular space of His, but in addition to it the blood vessels of the brain 
 have a lymph space within the adventitia of the blood vessels (Virchow-Robin's space). It is partly 
 lined by a well defined endothelium. Where the blood vessels begin to increase considerably in 
 diameter, they pass through the wall of the lymphatics, and the two vessels afterward take sepa- 
 rate courses. In all cases, where there is a perivascular space, the passage of lymph and blood 
 corpuscles into the lymphatics is greatly facilitated. In the tortoise the large blood vessels are often 
 surrounded with perivascular lymphatics. Fig. 206, A, gives a representation of the aorta sur- 
 rounded by a perivascular space (Gegenbaur) which is visible to the unaided eye. In mammals the 
 perivascular spaces are microscopic. 
 
 (4) Origin in the form of interstitial slits within organs. — Within the testis the lymphatics 
 begin simply in the form of numerous slits, which occur between the coils and twists of the seminal 
 tubules. They take the form of elongated spaces bounded by the curved cylindrical surfaces of the 
 tubules. The surfaces, however, are covered with endothelium. The lymphatics of the testis get 
 independent walls after they leave the parenchyma of the organ. In many other glands the gland 
 substance is similarly surrounded by a lymph space. The blood vessels pour the lymph into these 
 spaces, and from them the secreting cells obtain the materials necessary for the formation of their 
 secretion. 
 
 (5) Origin by means of free stomata on the walls of the larger serous cavities (Fig. 207, a). 
 — The investigations of v. Recklinghausen, Ludwig, Dybkowsky, Schweigger-Seidel, Dogiel, and 
 others have shown that the old view of Mascagni, that the serous cavities freely communicate with 
 the lymphatics, is correct. The investigation of the serous surfaces is most easily accomplished on 
 the septum of the great abdominal lymph sack of the frog. Silver nitrate distinctly reveals the 
 presence of relatively large free openings or stomata lying between the endothelium. Each stoma 
 
 Fig. 208. 
 
 Two lymph follicles. A, a small follicle highly magnified, showing the adenoid reticulum ; B, a follicle less highly 
 magnified, showing injected blood vessels. 
 
 is bounded by several germinating cells, which have a granular appearance, and undergo a change 
 of shape, so that the size of the stoma depends upon the degree of contraction of these cells ; thus 
 the stoma may be open (a), half open, (b), or completely closed (c). These stomata are the origin of 
 the lymphatics. The serous cavities belong therefore to the lymphatic system, and fluids placed in 
 the serous cavities readily pass into the lymphatics. The cavities of the peritoneum, pleura, peri- 
 cardium, tunica vaginalis testis, arachnoid space, aqueous chambers of the eye (Schwalbe), and the 
 labyrinth of the ear, are true lymph cavities, and the fluid they contain is to be regarded as lymph. 
 
 (6) Free open pores have been observed on some mucous membranes, which are regarded as the 
 origin of lymphatics, e.g., in the bronchi (Klein) — the nasal mucous membrane (Hjalmar-Heiberg), 
 in the trachea and larynx. 
 
 Structure. — The larger lymphatics resemble in structure the veins of corresponding size. The 
 valves are particularly numerous in the lymphatics, so that a distended lymphatic resemble s a, 
 chain of pearls. [Lymphatics have dilatations here and there in their course (Fig. 205).] 
 
 197. LYMPH GLANDS.— The so-called lymphatic glands belong to 
 the lymph apparatus. They are incorrectly termed glands, as they are merely 
 much branched lacunar labyrinthine spaces composed of adenoid tissue, and inter- 
 calated in the course of the lymphatic vessels. 
 
 They are simple and compound lymph glands. 
 
 (1) The simple lymph glands, or, more correctly, lymph follicles, are small, rounded bodies, 
 about the size of a pin head. They consist of a mass of adenoid tissue (Fig. 208, A), i. <?., of a 
 very delicate network of fine recticular fibres with nuclei at their points of intersection, and in the 
 
336 LYMPHATIC GLANDS. 
 
 spaces of the meshwork lie the lymph and the lymph corpuscles. Near the surface, the tissue is 
 somewhat denser, where it forms a capsule, which is not however a true capsule, as it is permeated 
 with numerous small, sponge-like spaces. Small lymphatics come directly into contact with these 
 lymph follicles, and often cover their surface in the form of a close network. The surface of the 
 lymph follicles is not unfrequently placed in the wall of a lymph vessel, so that it is directly bathed 
 by the lymph stream. Although no direct canal like opening leads from the follicle into the 
 lymphatic stream in relation with it, a communication must exist, and this is obtained by the numer- 
 ous spaces in the follicle itself, so that a lymph follicle is a true lymphatic apparatus whose juices 
 and lymph corpuscles can pass into the nearest lymphatic (Briicke). The follicles are surrounded 
 by a network of blood vessels which send loops of capillaries into their interior (Fig. 208, B). We 
 may assume that lymph corpuscles pass from these capillaries into the follicle. 
 
 In connection with these follicles, including those of the back of the tongue, the solitary glands 
 of the intestine and the adenoid tissue in the bronchial tract, the tonsils, Peyer's patches, it is import- 
 ant to remember that enormous numbers of leucocytes pass out between the epithelial cells cover- 
 ing these follicles. The extruded leucocytes undergo disintegration subsequently (Ph. Stohr). 
 
 (2) The compound lymph glands— the so-called lymphatic glands — represent a collection 
 of lymph follicles, whose form is somewhat altered. Every lymph gland is covered externally with 
 a connective-tissue capsule (Fig. 209, c), which contains numerous non-striped muscular fibres (0. 
 Heyfelder). From its inner surface, numerous septa and trabeculse (tr) pass into the interior of the 
 gland, so that the gland substance is divided into a large number of compartments. These com- 
 
 Fig. 209. 
 
 Diagrammatic section of a lymphatic gland, a, /, afferent ; e, I, efferent lymphatics; C, cortical substance; M, 
 reticular cords of medulla ; /, s, lymph sinus ; c, capsule, with trabeculse, tr. [Skarpey) 
 
 partments in the cortical portion of the gland have a somewhat rounded form, and constitute the 
 alveoli, while in the medullary portion they have a more elongated and irregular form. [On making 
 a section of a lymph gland we can readily distinguish the cortical from the medullary portion of 
 the gland.] All the compartments are of equal dignity, and they all communicate with each other 
 by means of openings, so that the septa bound a rich network of spaces within the gland, which 
 communicate on all sides with each other. 
 
 These spaces are traversed by the follicular threads (Fig. 210, f,f). These represent the contents 
 of the spaces, but they are smaller than the spaces in which they lie, and do not come into contact 
 anywhere with the walls of the spaces. If we imagine the spaces to be injected with a mass, which 
 ultimately shrinks to one-half of its original volume, we obtain a conception of the relation of these 
 follicular threads to the spaces of the gland. The blood vessels of the gland (b) lie within these 
 follicular threads. They are surrounded by a tolerably thick crust of adenoid tissue, with very fine 
 meshes (x, x) filled with lymph corpuscles, and with its surface (0, 0) covered by the cells of the 
 adenoid reticulum, in such a way as to leave free communications through the narrow meshes. 
 
 Between the surface of the follicular threads and the inner wall of all the spaces, of the gland, 
 lies the lymph channel or lymph path (B, B), which is traversed by a reticulum of adenoid tissue, 
 containing relatively few lymph corpuscles. It is very probable that these lymph paths are lined 
 by endothelium (v. Recklinghausen). 
 
 The vasa afferentia (Fig. 209, a, I), of which there are usually several, expand upon the surface 
 
LYMPHATIC GLANDS. 
 
 337 
 
 of the gland, perforate the outer capsule, and pour their contents into the lymph paths (C) of the 
 gland. The vasa efferentia, which are less numerous than the afferentia, and come out at the 
 hilum, form large, wide, almost cavernous dilatations, and they anastomose near the gland (e, I). 
 Through them the lymph passes out at the opposite surface of the gland. The lymph percolates 
 through the gland, and passes along the lymph paths, which represent a kind of rete mirabile inter- 
 posed between the afferent and efferent lymph vessels. 
 
 During its passage through this complicated branched system of spaces, the movement of the 
 lymph through the gland is retarded, and, owing to the numerous resistances which occur in its 
 path, it has very little propulsive energy. The lymph corpuscles which lie in the meshes of the 
 adenoid reticulum are washed out of the gland by the lymph stream (Briicke). The lymph cor- 
 puscles lying within the follicular threads pass through the narrow meshes (O) into the lymph 
 paths. The formation of lymph corpuscles occurs either locally, from division of the pre-existing 
 cells, or new leucocytes wander out into the follicular threads. The movement of the lymph 
 
 Fig. 210. 
 
 Part of a lymphatic gland. A, Vas afferens ; B, B, lymph paths within the gland ; a, a, septa or trabecular seen on 
 edge ; f,f, follicular strand from the medulla ; x t x, its adenoid reticulum ; b, its blood vessels ; o, o, narrow 
 meshed part limiting the follicular strands from the lymph path. 
 
 through the gland is favored by the muscular action of the capsule. When the capsule contracts 
 energetically, it must compress the gland like a sponge, and the direction in which the fluid moves 
 is regulated by the position and arrangement of the valves. The researches of Teichmann, His, 
 Frey, Brttcke and v. Recklinghausen have chiefly contributed to the elucidation of the morpho- 
 logical and physiological relations of the lymph glands. 
 
 Chemistry. — In addition to the constituents of lymph, the following chemical substances have 
 been found in lymphatic glands : Leucin [Frerichs and Stadeler) and Xanthin. 
 
 198. PROPERTIES OF CHYLE AND LYMPH.— Chyle and 1 
 
 Lymph are albuminous, colorless, clear juices, containing lymph corpuscles, 
 
 which are identical with the colorless blood corpuscles (§ 9). In some places, 
 
 e.g., in the lymphatics of the spleen, especially in starving animals (JVasse), and 
 
 22 
 
338 COMPOSITION OF CHYLE. 
 
 in the thoracic duct, a few colored blood corpuscles have been found. The 
 lymph corpuscles are supplied to the lymph and chyle from the lymphatic glands 
 and the adenoid tissue. As to their source see § 200, 2. They also pass out of 
 the blood vessels and wander into the lymphatics. As red blood corpuscles have 
 also been seen to pass out of the blood vessels {Strieker, J. Arnold), this explains 
 the occasional presence of these corpuscles in some lymphatics ; but when the 
 pressure within the veins is high near the central orifice of the thoracic duct, red 
 blood corpuscles may pass into the thoracic duct. But we are not entitled to con- 
 clude from their pressure that lymph cells form red blood corpuscles. In addi- 
 tion, the chyle contains numerous fatty granules each surrounded with an albu- 
 minous envelope. [Thus the chyle, in addition to the constituents of the lymph, 
 contains, especially during digestion, a very large amount of fat, in the form of 
 the finely emulsionized fat of the food, which gives it its characteristic white or 
 milky appearance. During hunger, the fluid in the lacteals resembles ordinary 
 lymph. The fine fat granules constitute the so-called " molecular basis" of 
 the chyle.] 
 
 Composition of Lymph. — The lymph consists of a plasma with lymph 
 corpuscles suspended in it. The corpuscles — for the most part investigated in 
 the form of pus cells — consist of a swollen-up proteid and soluble paraglobulin, 
 together with lecithin, cerebrin, cholesterin and fat, while their nuclei yield nuclein. 
 Nuclein contains P, and is prepared by the artificial digestion of pus, as it alone 
 remains undigested ; it is soluble in alkalies, and is precipitated from this solution 
 by acids. It gives a feeble xanthoproteic reaction. When subjected to the pro- 
 longed action of alkalies and acids, it yields substances allied to albumin and 
 syntonin. Miescher found glycogen in the lymph corpuscles of serous fluids (§ 
 24). The lymph plasma contains the three so-called fibrin factors (§ 29), 
 derived very probably from the breaking up of lymph corpuscles. When lymph 
 is withdrawn from the body, these substances cause it to coagulate. Coagula- 
 tion occurs slowly, owing to the formation of a soft, jelly-like, small "lymph 
 clot," which contains most of the lymph corpuscles. The exuded fluid or 
 lymph serum contains alkali albuminate (precipitated by acids), serum albumin 
 (coagulated by heat), and. paraglobulin — the two latter occurring in the same pro- 
 portion as in blood serum •; 37 per cent, of the coagulable proteids is paraglobu- 
 lin (Salvioli). Peptone has been found in chyle (? and perhaps also in lymph) ; 
 also urea ( Wurtz), leucin and sugar. 
 
 (2) Chyle, which occurs within the lacteals of the intestinal tract, can only 
 be obtained in very small amount before it is mixed with lymph, and hence 
 the difficulty of investigating it. A few lymph corpuscles occur even in the 
 origin of lacteals within the villi, but their number increases in the vessels 
 beyond the intestine, more especially after the chyle has passed through the 
 mesenteric glands. The amount of solids which undergoes a great increase 
 during digestion, on the contrary, diminishes when chyle mixes with lymph. 
 After a diet rich in fatty matters, the chyle contains innumerable fatty granules 
 (2-4 /* in size). [This is the so-called "molecular basis" of the chyle.] The 
 amount of fibrin factors increases with the increase of lymph corpuscles, as 
 they are formed from the breaking up of the lymph corpuscles. Grohe found 
 a diastalic ferment in chyle, which was probably absorbed from the intestine, 
 occasionally sugar, to 2 per cent. {Colin); after much starchy food, lactates 
 have been found {Lehmann), peptone in the leucocytes (§ 192, I, 3), and traces 
 of urea and leucin ( Wurtz). 
 
 The Chyle of a person who was executed contained: — 
 
 Water 90.5 per cent. 
 
 Solids 95 " 
 
 Solid 
 
 'Fibrin trace. 
 
 Albumin 7.1 
 
 Fats 0.9 
 
 Extractives 1.0 
 
 Salts 0.4 
 
QUANTITY OF LYMPH AND CHYLE. 
 
 339 
 
 Cl. Schmidt found the following inorganic substances in iooo parts of chyle (horse) : — 
 
 Sodic chloride .... 5.84 
 
 Soda 1. 17 
 
 Potash 0.13 
 
 Sulphuric acid .... 0.05 
 Phosphoric acid .... 0.05 
 Calcic phosphate . . .0.20 
 
 Magnesic phosphate 
 Iron 
 
 . 0.05 
 , trace. 
 
 (3) The lymph obtained from the beginning of the lymphatic system also 
 contains very few lymph corpuscles ; it is clear, transparent and colorless, and 
 closely resembles the fluids of serous cavities. That the lymph coming from dif- 
 ferent tissues varies somewhat, is highly probable, but this has not been proved. 
 After lymph has passed through lymphatic glands, it contains more corpuscles, 
 and also more solids, especially albumin and fat. Ritter counted 8200 lymph 
 corpuscles in one cubic centimetre of the lymph of a dog. 
 
 Hensen and Dahnhardt obtained pure lymph in considerable quantity from a 
 lymphatic fistula in the leg of a man. It had an alkaline reaction and a saline 
 taste. It had the following composition, which may be compared with the com- 
 position of serous transudations : — 
 
 Pure Lymph 
 {Hensen &* Dahnhardt). 
 
 Cerebrospinal Fluid 
 (Hoppe-Seyler) . 
 
 Pericardial Fluid. 
 (z». Gorup-Besanez). 
 
 Salts . . 0.88 
 
 98.74 
 I.25 
 
 O.16 
 
 The cerebro-spinal fluid and ab- 
 dominal lymph contain a kind of 
 sugar (without the property of rotat- 
 ing polarized light — Hoppe-Seyler). 
 
 95-51 
 4.48 
 O.08 
 2.46 
 
 1.26 
 
 70 vol.% of C0 2 , 50% of which 
 could be pumped out, and zofo 
 by the addition of an acid. 
 
 100 parts of the Ash of Lymph contained the following substances :- 
 
 Sodium chloride . . . 74.48 
 
 Soda J0.36 
 
 Potash 3.26 
 
 Lime 0.98 
 
 Magnesia 0.27 
 
 Phosphoric acid . . .1.09 
 
 Sulphuric acid 1.28 
 
 Carbonic acid 8.21 
 
 Iron oxide 0.06 
 
 Just as in blood, potash and phosphoric acid are most abundant in the 
 corpuscles, while soda (chiefly sodium chloride) is most abundant in the 
 lymph serum. The potash and phosphoric acid compounds are most abundant 
 in cerebro-spinal fluid, according to C. Schmidt. The amount of water in the 
 lymph rises and falls with that of the blood. Gases. — Dog's lymph contains 
 much C0 2 — more than '40 vols, per cent., of which 17 per cent, can be pumped 
 out, and 23 per cent, expelled by acids, while there are only traces of O and 1.2 
 vols, per cent. N {Ludwig, Hammersteri). 
 
 The observation that when lymph is collected from large vessels and exposed to the air, it becomes 
 red [Funke), is, as yet, unexplained; but it is certainly not due to the formation of colored corpus- 
 cles from colorless ones, owing to contact with the O of the air. 
 
 199. QUANTITY OF LYMPH AND CHYLE.— When it is stated 
 that the total amount of the lymph and chyle passing through the large vessels 
 in twenty-four hours is equal to the amount of the blood {Bidder and C. Schmidt), 
 it must be remembered that this is merely a conjecture. Of this amount one-half 
 may be lymph and the other half chyle. The formation of lymph in the tissues 
 takes place continually, and without interruption. Nearly 6 kilos, of lymph were 
 collected in twenty-four hours from a lymphatic fistula in the arm of a woman, 
 by Gubler and Quevenne; 70 to 100 grms. were collected in 1^ to 2 hours from 
 the large lymph trunk in the neck of a young horse. The following conditions 
 affect the amount of chyle and lymph : — 
 
340 ORIGIN OF LYMPH. 
 
 (i) The amount of chyle undergoes very considerable increase during diges- 
 tion, more especially after a full meal, so that the lacteals of the mesentery and 
 intestine are distended with white or milky chyle. During hunger, the lymph 
 vessels are collapsed, so that it is difficult to see the large trunks. 
 
 (2) The amount of blood increases with the activity of the organ from which 
 it proceeds. Active or passive muscular movements greatly increase its amount. 
 Lesser obtained in this way 300 cubic centimetres of lymph from a fasting dog, 
 whereby its blood became so inspissated as to cause death. 
 
 (3) All conditions which increase the pressure upon the juices of the tissues 
 increase the amount of lymph, and vice versa. These conditions are : — 
 
 (o) An increase of the blood pressure, not only in the whole vascular system, but also in the 
 vessels of the corresponding organ, augments the amount of lymph and vice versa (Ludwig,Tomsa). 
 This, however, is doubtful, as has been shown by Paschutin and Emminghaus. [In order to increase 
 the amount of lymph depending upon pressure within the vessels, what must happen is increased 
 pressure within the capillaries and veins.] 
 
 (b) Ligature or obstruction of the efferent veins greatly increases the amount of lymph which 
 flows from the corresponding parts (Bidder, Emminghaus). It may be doubled in amount ( Weiss'). 
 Tight bandages cause a swelling of the parts on the peripheral side of the bandage, owing to a 
 copious effusion of lymph into the tissue (congestive cedema). 
 
 (c) An increased supply of arterial blood acts in the same way, but to a less degree. Paralysis 
 of the vasomotor nerves (Ludwig), or stimulation of vasodilator fibres (Gianuzzi), by increasing the 
 supply of blood, increases the amount of lymph ; while diminution of the blood supply, owing to 
 stimulation of vasomotor fibres or other causes, diminishes the amount. Even after ligature of both 
 carotids, as the head is still supplied with blood by the vertebrals, the lymph stream in the large 
 cervical lymphatic does not cease ( W. Krause). 
 
 (4) When the total amount of the blood is increased, by the injection of blood, serum, or milk 
 into the arteries, much fluid passes into the tissues and increases the formation of lymph. 
 
 (5) The formation of lymph still goes on for a short time after death, and after complete cessation 
 of the action of the heart, but only to a slight extent. If fresh blood be caused to circulate in the 
 body of an animal, while it is still warm, more lymph flows from the lymphatics ( Genersich). It 
 appears as if the tissues obtained plasma from the blood for a time after the stoppage of the circula- 
 tion. This, perhaps, explains the circumstance that some tissues — e.g., connective tissues — contain 
 more fluid alter death than during life, while the blood vessels have given out a considerable amount 
 of their plasma after death. 
 
 (6) The amount of lymph is increased under the influence of curara (Lesser, Paschutin), and so 
 is the amount of solids in the lymph. A large amount of lymph collects in the lymph sacs [especially 
 the sublingual] of frogs poisoned with curara, which is partly explained by the fact that the lymph 
 hearts are paralyzed by curara (Bidder). The amount of lymph is also increased in inflamed parts 
 (Lassar). 
 
 200. ORIGIN OF LYMPH.— (1) Origin of the Lymph Plasma.— 
 
 The lymph plasma may be regarded as fluid which has been pressed through the 
 walls of the blood vessels by the blood pressure, i. e., by filtration into the tissues. 
 The salts which pass most readily through membranes, go through nearly in the 
 same proportion as they exist in blood plasma — the fibrin factors to about two- 
 thirds, and albumin to about one-half of that in the blood. As in the case of other 
 filtration processes, the amount of lymph must increase with increasing pressure. 
 
 This was proved by Ludwig and Tomsa, who found that when they passed blood serum under 
 varying pressures through the blood vessels of an excised testis, the amount of transuded fluid which 
 flowed from the lymphatics varied with the pressure. This " artificial lymph " had a composition 
 similar to that of the natural lymph. Even the amount of albumin increased with increasing pressure. 
 The lymph plasma is mixed in the different tissues with the decomposition products, the results of 
 the metabolism of the tissues. 
 
 When the muscles are in action, not only is the lymph poured out more rapidly, 
 but more lymph is formed. The tendons and fasciae of the muscles of the skeleton, 
 which are provided with numerous small stomata, absorb the lymph from the 
 muscles. By the alternate contraction and relaxation of these fibrous structures, 
 they act like suction pumps, whereby the lymphatics are alternately filled and 
 emptied, while the lymph is propelled onward. Even passive movements act in 
 the same way. If solutions be injected under the fascia lata, they may be propelled 
 
MOVEMENT OF CHYLE AND LYMPH. 341 
 
 onward to the thoracic duct by passive movements of the limb (Ludwig, Schweigger- 
 Seidel, and Genersich). 
 
 (2) The Origin of the Lymph Corpuscles varies. — (1) A very consider- 
 able number of the lymph corpuscles are derived from the lymphatic glands ; 
 they are washed out of these glands into the vas efferens by the lymph stream, 
 hence, the lymph always contains more corpuscles after it has passed through a 
 lymph gland. Small, isolated lymph follicles permit corpuscles to pass through 
 their limiting layer into the lymph stream. (2) A second source is those organs 
 whose basis consists of adenoid tissue, and in whose meshes numerous lymph 
 corpuscles occur, e.g., the mucous membrane of the entire intestinal tract, red 
 marrow of bone, and the spleen (§ 103). In these cases the cells reach the origin 
 of the lymph stream by their own amoeboid movements. (3) As lymph corpuscles 
 are returned to the blood stream, where they appear as colorless blood corpuscles, 
 so they again pass out of the blood capillaries into the tissues, partly owing to 
 their amoeboid movements (Cohnheini), and they are partly expelled by the blood 
 pressure (Hering). In rare cases lymph corpuscles wander from lymphatic spaces 
 back again into the blood vessels (v. Recklinghausen). 
 
 Fine particles of cinnabar or milk globules introduced into the blood soon pass into the lymphatics, 
 and the vasomotor nerves do not afreet the process. The extrusion of particles is greater during 
 venous congestion than when the circulation is undisturbed, just as with diapedesis (| 95) ; inflam- 
 matory affections of the vascular wall also favor their passage. The vessels of the portal system are 
 especially pervious {Hiitimeyer). 
 
 (4) By division of the lymph corpuscles, and also by proliferation of 
 the fixed connective-tissue corpuscles (His). This process certainly occurs 
 during inflammation of many organs. This has been proved for the excised cor- 
 nea kept in a moist chamber (v. Recklinghausen, Hoffmann) ; the nuclei of the 
 cornea corpuscles proliferate also (Strieker, Norris). 
 
 That the connective-tissue corpuscles proliferate is shown by the enormous production of lymph 
 corpuscles in acute inflammations (with the formation of pus), e.g., in extensive erysipelas, and in- 
 flammatory purulent effusions into serous cavities, where the number of corpuscles is too great to be 
 explained by the wandering of blood corpuscles out of the blood vessels. 
 
 Decay of Lymph Corpuscles. — The lymph corpuscles disappear partly 
 where the lymphatics arise. The occurrence of the fibrin factors in the lymph — 
 formed as they are from the breaking up of lymph corpuscles — would seem to in- 
 dicate this. In inflammation of connective tissue, in addition to the formation of 
 numerous new lymph corpuscles, a considerable number seems to be dissolved ; 
 hence the lymph, and also the blood, in this case contains more fibrin. Lymph 
 corpuscles are also dissolved 'within the blood stream, and help to form the 
 fibrin factors. 
 
 201. MOVEMENT OF CHYLE AND LYMPH.— The ultimate 
 cause of the movement of the chyle and lymph depends upon the difference of 
 the pressure at the origin of the lymphatics, and the pressure where the thoracic 
 duct opens into the venous system. 
 
 (1) The forces which are active at the origin of the lymphatics are con- 
 cerned in moving the lymph, but these must vary according to the place of origin 
 — (a) The lacteals receive the first impulse toward the movements of their con- 
 tents — the chyle — from the contraction of the muscular fibres of the villi (pp. 
 322, 327). When these contract and shorten the axial lacteal is compressed, and 
 its contents forced in a centripetal direction toward the large lymphatic trunks. 
 When the villi relax, the numerous valves prevent the return of the chyle into the 
 villi, (b) Within those lymphatics which take the form of perivascular spaces, 
 every time the contained blood vessel is dilated the surrounding lymph will be 
 •pressed onward, (c) In the case of the pleural lymphatics with open mouths, 
 every inspiratory movement acts like a suction pump upon the lymph (Dyb- 
 kowsky), and the same is the case with the openings (stomata) of the lymphatics 
 
342 
 
 MOVEMENT OF THE LYMPH. 
 
 on the abdominal side of the diaphragm {Ludwig, Schweigger-Seidel). (d) In 
 the case of those vessels which begin by means of fine juice canals, the movement 
 of the lymph must largely depend upon the tension of the juices of the par- 
 enchyma, and this again must depend upon the tension or pressure in the blood 
 capillaries, so that the blood pressure acts like a vis a tergo in the rootlets of the 
 lymphatics. 
 
 [In some organs peculiar pumping arrangements are brought into action. As already men • 
 tioned, the abdominal surface of the central tendon of the diaphragm is provided with ftomata, or 
 open communications between the peritoneal cavity and the lymphatics in the substance of the ten- 
 don, v. Recklinghausen found that milk put upon the peritoneal surface of the central tendon 
 
 Fig. 211. 
 
 Section of central tendon of diaphragm. The injected lymph spaces, h and h, are black. At/ the walls of 
 the space are collapsed (Brunton, after Ludwig and Schweigger-Seidel). 
 
 showed little eddies caused by the roilk globules passing through the stomata and entering the lym- 
 phatics. The central tendon consists of two layers of fibrous tissue arranged in different directions 
 (Fig. 211, 6, c). When the diaphragm moves during respiration, these layers are alternately pressed 
 together and pulled apart. Thus the spaces are alternately dilated and contracted, lymph being 
 drawn into the lymphatics (Fig. 211, h) through the stomata.] 
 
 [Ludwig's Experiment. — Tie a respiration cannula in the trachea of a dead rabbit ; cut across 
 the body of the animal immediately below the diaphragm ; remove the viscera, and ligature the 
 vessels passing between the thorax and abdomen ; tie the thorax to a ring, and hang it up with the 
 head downward ; pour a solution of Berlin blue upon the peritoneal surface of the diaphragm; con- 
 nect the respiration cannula either with a pair of bellows or an apparatus for artificial respiration, 
 
 Fig. 212. 
 
 Injected lymph spaces from the fascia lata of the dog. The injected spaces are black in the figure 
 {Brunton, after Ludwig and Schweigger-Seidel). 
 
 and imitate the respiratory movements. After a few minutes the lymphatics are filled with a blue 
 injection showing a beautiful plexus.] 
 
 [The same kind of pumping mechanism exists over the costal pleura. The fascia covering the 
 muscles is another similar mechanism. The fascia consists of two layers of fibrous tissue, with in- 
 tervening lymphatics (Fig. 212). When a muscle contracts, lymph is forced out from between the 
 layers of the fascia, while when it relaxes, the lymph from the muscle, carrying with it some of the 
 waste products of muscular action, passes out of the muscle into the fascia, between the now partially 
 separated layers.] 
 
 (2) Within the lymph trunks themselves, the independent contraction of 
 their muscular fibres partly aids the lymph stream. Heller observed in the 
 mesentery of the guinea pig that the peristaltic movements of the lymphatic wall 
 
LYMPH HEARTS. 
 
 343 
 
 passed in a centripetal direction. The numerous valves prevent any reflux. 
 The contraction of the surrounding muscles, and every pressure upon the vessels 
 and the tissues aid the current {Ludwig, JVbll). If the outflow of blood from 
 the veins is interfered with, lymph flows copiously from the corresponding tissues 
 (Nasse, Tomsd). [If a cannula be tied in a lymphatic of a dog, a few drops of 
 lymph flow out at long intervals. But if even passive movements of the limb be 
 made, e. g. , simply flexing and extending the limb, the outflow becomes very con- 
 siderable and continuous.] 
 
 (3) The lymph glands, which occur in the course of the lymphatics, offer 
 very considerable resistance to the lymph stream, which must pass through the 
 lymph paths, whose spaces are traversed by adenoid tissue, and contain a few 
 lymph corpuscles. But this is, to a certain extent, compensated by the non-striped 
 muscle which exists in the capsule and trabeculae of the glands. When they con- 
 tract they force on the lymph, while the valves prevent its reflux. Enlarged 
 lymphatic glands have been seen to contract when stimulated electrically. [Bot- 
 kin has stimulated enlarged lymphatic glands with electricity in cases of leu- 
 kaemia.] 
 
 (4) As the lymph vessels gradually join and form larger vessels, and finally 
 
 Fig. 213. 
 
 Posterior pair or sacral lymph hearts (L) of the frog (Ecker). 
 
 form one trunk, the transverse section, or sectional area, diminishes, so that the 
 velocity of the current and the pressure are increased. Nevertheless, the velo- 
 city is always small ; it varied from 230 to 300 millimetres per minute in the large 
 lymphatic in the neck of a horse ( Weiss'), a fact which enables us to conclude 
 that the movement must be very slow in small vessels. The lateral pressure at 
 the same place was 10 to 20 mm., and in the dog 5 to 10 mm. of a weak solution 
 of soda ( Weiss, Noll), although it was found to he 12 mm. Hg in the thoracic 
 duct of a horse ( Weiss). 
 
 (5) The respiratory movements exercise a considerable influence upon the 
 lymph stream in the thoracic duct, and in the right lymphatic duct ; every inspira- 
 tion favors the passage of the venous blood, and also of the lymph toward the 
 heart, whereby the tension in the thoracic duct may even become negative {Bid- 
 der). [The diastolic suction of the heart, by diminishing the pressure in the sub- 
 clavian vein, also favors the inflow of lymph into the thorax.] 
 
 (6) Lymph hearts exist in certain cold-blooded animals (Panizza, Jok. Micller). The frog 
 has two axillary hearts (above the shoulder near the vertebral column, and two sacral hearts, one 
 on each side of the coccyx near the anus (Fig. 213, L). [If the skin covering them be reflected 
 they are brought into view at once.] They beat, but not synchronously, about sixty times per 
 
344 CEDEMA, DROPSY, AND SEROUS EFFUSIONS. 
 
 minute, and contain 10 cubic centimetres of lymph. They have transversely-striped muscular 
 fibres in their walls, and are also provided with nerve ganglia ( Waldeyer). The posterior pair 
 pump the lymph into the branch of the vena iliaca communicans, and the anterior pair into the 
 vena subscapularis. Their pulsation depends partly, but not exclusively, upon the spinal cord, for 
 if the cord be rapidly destroyed, they may cease to pulsate ( Volkmanh), but not unfrequently they 
 continue to pulsate after removal of the cord {Valentin, Luchsinger). A second source of their 
 pulsatile movements is to be sought for in Waldeyer's ganglia. Stimulation of the skin, intestine 
 or blood heart influences them reflexly — partly accelerating and partly retarding them. If the 
 coccygeal nerve, which connects the sacral hearts to the spinal cord, be divided, these effects do not 
 occur {v. Wittich). Strychnia accelerates their movements {Scherhej), and so does heating of the 
 spinal cord, but if the cord be cooled they are retarded {Fubini and Spalitta). A lymph heart 
 arrested by being exposed, or after the action of muscarin, can be caused to beat by filling it under 
 pressure, but this is not the case when the arrest is caused by destruction of its nerves [Boll, Lan- 
 gerdorff). Antiarin paralyzes the lymph heart and the blood heart at the same time ( Vintschgau], 
 while curara paralyzes the former alone {Bidder). In other amphibians, there are two lymph 
 hearts ; in the ostrich and cassowary and some swimming birds (Panizza), and in the embryo chick 
 (A. Budge) I or 2. They occur in some fishes, a. g., near the caudal vein of the eel. 
 
 (7) The nervous system has a direct effect upon the lymph stream) on 
 account of its connection with the muscles of the lymphatics and lymph glands, 
 and with the lymph hearts, where these exist. Further, Kiihne observed that the 
 cornea corpuscles contracted when the corneal nerves were stimulated. Goltz 
 also observed that when a dilute solution of common salt was injected under the 
 skin of a frog, it was rapidly absorbed, but if the central nervous system was 
 destroyed it was not absorbed. 
 
 If inflammation be produced in the posterior extremities of a dog, and if the sciatic nerve be 
 divided on one side, oedema and a simultaneous increase of the lymph stream occur on that side 
 (Jankowski). [A combination of congestion and inflammation greatly increases the lymph stream, 
 and this is still more the case when the nerves are divided at the same time.] 
 
 Ligature the leg of a frog, except the nerves, so as to arrest the circulation, and place the leg in 
 water ; it swells up very rapidly, but a dead limb does not swell up. So that absorption is inde- 
 pendent of the continuance of- the circulation. Section of the sciatic nerve, or destruction of the 
 spinal cord (but not section of the brain), arrests absorption {Lautenbach). 
 
 202. ABSORPTION OF PARENCHYMATOUS EFFUSIONS.— Fluids which pass 
 from the blood vessels into the spaces in the tissues, or those injected subcutaneously, are absorbed 
 chiefly by the blood vessels, but also by the lymphatics. Small particles, as after tattooing with cin- 
 nabar or China ink, may pass from the tissue spaces into the lymphatics — and so do blood cor- 
 puscles from extravasations of blood, and fat granules from the marrow of a broken bone. If all 
 the lymphatics of a part are ligatured, absorption takes place quite as rapidly as before (Magendie) ; 
 hence, absorbed fluid must pass through the thin membranes of the blood vessels. The correspond- 
 ing experiment of ligaturing all the blood vessels, when no absorption of the parenchymatous juices 
 takes place {Emmert, Henle, v. Dusch), does not prove that the lymphatics are not concerned in 
 absorption, for, after ligaturing the blood vessels of a part, of course, the formation of lymph, and 
 also the lymph stream, must cease. 
 
 When fluids are injected under the skin absorption takes place very rapidly — more rapidly 
 than when the substance is given by the mouth. The subcutaneous inj ection of many drugs is 
 now extensively used, but, of course, the substances used must not corrode, irritate, or coagulate 
 the tissues. Some substances do not act when given by the mouth, as snake poison, poisons 
 from dead bodies, or putrid things, although they act rapidly when introduced subcutaneously. If 
 emulsin be given by the mouth, and amygdalin be injected into the veins of an animal, hydro- 
 cyanic acid is not formed, as the emulsin seems to be destroyed in the alimentary canal. If the 
 emulsin, however, be injected into the blood, and the amygdalin be given by the mouth, the animal 
 is rapidly poisoned, owing to the formation of hydrocyanic acid, as the amygdalin is rapidly absorbed 
 from the intestinal canal. The amygdalin, a glucoside (C 20 H 27 NO 11 ), is acted upon by fresh 
 emulsin like a ferment; it takes up 2(H 2 0) and yields hydrocyanic acid (CHN), + oil of bitter 
 almonds (C,H e O), -f- sugar 2(C 6 H 12 6 ) — {CI. Bernard). When serum is injected subcuta- 
 neously, it is rapidly absorbed ; it is decomposed within the blood stream, and increases the amount 
 of urea. Albuminous solutions, oil, peptones, and sugars are also absorbed {Eichhorst). 
 
 203. CEDEMA, DROPSY, AND SEROUS EFFUSIONS.— [Dropsy. As aptly illus- 
 trated by Lauder Brunton, the lymph spaces may be represented by cisterns, each of which is pro- 
 vided with supply pipes — the arteries and capillaries; while there are two exit pipes— the veins and 
 lymphatics. In health, the balance between the inflow and outflow is such that the spaces are 
 merely moistened with fluid. When a cannula is placed in a lymphatic vessel in a dog, only a few 
 drops of lymph flow out at long intervals. Emminghaus found that if the veins of the limb be 
 
CEDEMA, DROPSY, AND SEROUS EFFUSIONS. 345 
 
 ligatured the lymph flows much more quickly. This is in part due to the increased transudation of 
 fluid from the small blood vessels, but, as Brunton suggests, it may also be due to fluid passing away 
 by the lymphatics when it can no longer be carried away by the veins. We cannot say what is the 
 relative share of the veins and lymphatics, nor in the above experiment do we know how much is 
 due to increased transudation or diminished absorption. When there is an undue accumulation of 
 fluid more or less like serum in the lymph spaces, we have the condition termed dropsy. When 
 there is general dropsy it is called anasarca.] 
 
 CEdema. — If the efferent veins and lymphatics of an organ be ligatured, or if resistance be 
 offered to the outflow of their contents, congestion and a copious transudation of lymph into the 
 tissues take place. These are most marked in the skin and subcutaneous cellular tissue. The soft 
 parts swell up, without pain or redness, and a doughy swelling, which pits on pressure with the 
 finger, results. These are the signs of lymph congestion, which is called oedema when the fluid 
 is watery and localized. 
 
 Under similar circumstances, lymph is«effused in the serous cavities. [In the peritoneum it is 
 ascites — thorax, hydrothorax — pericardium, hydro-pericardium — cranium, hydrocephalus — tunica 
 vaginalis, hydrocele — joints, hydrarthrosis, etc.] If, at the same time, a large number of colorless 
 blood corpuscles pass out of the blood vessels into the cavity, the fluid becomes more and more 
 like pus. In order that these corpuscles may proliferate, a considerable percentage of albumin is 
 necessary. When the pressure within the serous cavity rises above that in the small blood vessels, 
 water may pass into the blood. These sero-purulent effusions not unfrequently undergo changes, 
 and yield decomposition products, such as leucin, tyrosin, xanthin, kreatin, kreatinin (?), uric acid 
 (?), urea. Endothelium from the serous cavity [Quincke), sugar in pleuritic effusions (Eichhorst) 
 and in cedemas with little albumin (Rosenbach), cholesterin frequently in hydrocele fluid, and suc- 
 cinic acid in the fluid of echinococci, have all been found in these effusions. 
 
 The effusion of lymph may arise not only from pressure upon the lymphatics, but also from in- 
 flammation and thrombosis of the lymphatics themselves, in which cases not unfrequently new 
 lymphatics are formed, so that the communication is re-established. Sometimes the ductus tho- 
 racicus bursts, and lymph is poured directly into the abdomen or thorax. [Ligature of the thoracic 
 duct results in rupture of the receptaculum chyli and escape of chyle and lymph into the large 
 serous cavities (Ludwig).~\ 
 
 When dropsy or effusion of fluids occurs into serous cavities, there is always a greater transuda- 
 tion of fluid through the blood vessels. The abdominal blood vessels, and those which yield a 
 watery effusion under normal circumstances, are those most liable to be affected . 
 
 Transudation is favored by — (i) Venous congestion, so as to raise the blood pressure, in 
 which case the effusion usually contains little albumin and few lymph corpuscles, while the colored 
 corpuscles, on the contrary, are more numerous the greater the venous obstruction. Ranvier pro- 
 duced oedema artificially by ligaturing the vena cava in a dog, and at the same time dividing the 
 sciatic nerve. The paralytic dilatation of the blood vessels thereby produced caused an increased 
 amount of blood to pass to the limb, while the blood pressure was raised, and both factors favored 
 the transudation of fluid. [Ranvier's experiment proves that mere ligature of the venous trunk of 
 a limb by itself is not sufficient to cause oedema. The oedema is due to the concomitant paralysis of 
 the vasomotor nerves. If the motor roots of the sciatic nerve alone be divided along with ligature of 
 the vena cava, no oedema occurs, but if the vasomotor fibres are divided at the same time, the limb 
 rapidly becomes cedematous. There is such an increased transudation through the vascular walls 
 that the veins and lymphatics cannot remove it with sufficient rapidity, and oedema occurs. If there 
 be weakness of the vasomotor nerves, slight obstruction is sufficient to produce oedema (Lauder 
 Brunton).~\ When the leg veins are occluded with an injection of gypsum, oedema occurs 
 (Sotnischewsky). (2) Some unknown physical changes occur in the protoplasm of the endo- 
 thelium of the capillaries and blood vessels, which favor the transudation of albumin, haemoglobin, 
 and even blood corpuscles. This occurs when abnormal substances accumulate in the blood — e.g., 
 dissolved haemoglobin — and when the blood contains little O or albumin. The same has been ob- 
 served after exposure to too high temperatures, and the swelling of soft parts in the neighborhood 
 of an inflammatory focus seems due to the transudation of fluid through the altered vascular wall. 
 It is probable that a nervous influence may affect particular areas through its action on the blood 
 vessels of the part (it may be upon the protoplasm of the blood capillaries). The transudations of 
 this nature usually contain much albumin and many lymph corpuscles. (3) When the blood con- 
 tains a very large amount of water the tendency to transudation of fluid is increased. After a 
 time it may produce the changes indicated in (2), and when long continued may increase the permea- 
 bility of the vascular wall (Cohnheim). Watery lymphatic effusions, from watery blood — " cachec- 
 tic oedema " — occur in feeble and badly nourished individuals. [One of the commonest forms of 
 dropsy is the slight oedema of the legs in anaemic persons in whom the heart and lungs are healthy. 
 Many factors are involved — the blood pressure, watery condition of the blood, the condition of 
 nutrition of the capillaries, and probably a tendency to vasomotor paresis (Brunton)."] 
 
 [The fluid poured out varies according to the rapidity with which this occurs. In acute inflamma- 
 tion, effusion or exudation takes place rapidly, and the fluid contains the fibrin factors, so that it 
 tends to coagulate spontaneously. There is every gradation between the non-coagulable hydrocele 
 fluid and the coagulable exudation in inflammation. The fluids in different dropsies vary in com- 
 
346 COMPARATIVE AND HISTORICAL. 
 
 position, and some have more cells in them, depending on local causes, as in some situations absorp- 
 tion is more active than in others {fames). The pleural fluid contains most solids, then ascitic, 
 cerebro-spinal, and, lastly, that in the subcutaneous tissue.] 
 
 [(4) Ostroumoff found that stimulation of the lingual nerve not only causes the blood vessels of 
 the tongue to dilate, but the corresponding side of the tongue becomes oedematous. If a solution 
 of dilute hydrochloric acid or quinine ($ 145) be injected into the duct of the submaxillary gland, 
 and the chorda tympani stimulated, there is no secretion of saliva, but the gland becomes oedema- 
 tous. In an animal poisoned with atropin, stimulation of the chorda causes dilatation of the blood 
 vessels, although there is no secretion of saliva ; nevertheless, the gland does not become oedema- 
 tous (Heidenkain). As Brunton suggests, this experiment points to some action of atropin on the 
 blood vessels which has, hitherto, been entirely overlooked.] 
 
 204. COMPARATIVE PHYSIOLOGY.— In the frog large lymph sacs, lined with endo- 
 thelium, exist under the skin, while large lymph sacs lie in relation with the vertebral column — one 
 on each side — separated from the abdominal cavity by a*thin membrane, perforated with stomata. 
 This is the cysterna lymphatica magna of Panizzi. Some amphibians, and many reptiles, have 
 ■large lymph spaces under the skin, which occupy the whole of the dorsal region of the body. All 
 reptiles and the tailed amphibians have large elongated reservoirs for lymph along the course of the 
 aorta. The lymph apparatus of the tortoise (Fig. 206) is very extensive. The osseous fishes 
 have in the lateral parts of their backs an elongated lymph trunk, Which reaches from the tail to 
 the anterior fins, and is connected with the dilated lymphatic rootlets in the base of the tail and in 
 the fins. The largest internal lymph sinus is in the region of the oesophagus. Many birds possess 
 a sinus-like dilatation or lymph space in the region of the tail. The lymph spaces communicate 
 with the venous system — with valves properly arranged — usually in connection with the upper vena 
 cava. Lymph hearts have already been referred to (g 201, 6). In carnivora the lymph glands of 
 the mesentery are united into one large, compact mass, the so-called " pancreas Asellii." 
 
 205. HISTORICAL. — Although the Hippocratic School was acquainted with the lymph glands, 
 from their becoming swollen from time to time, and although Herophilus and Erasistratus had seen 
 the mesenteric glands, yet Aselli (1662) was the first who accurately described the lacteals of the 
 mesentery with their valves. Pecquet (1648) discovered the receptaculum chyli; Rudbeck and 
 Thorn. Bartholinus, the lymphatic vessels (1650-52) ; Eustachius (1563) was acquainted with the 
 thoracic duct, which Gassendus (1654) maintained that he was the first to see; Lister noticed that 
 the chyle became blue when indigo was injected into the intestine (1671); SSmmering observed 
 the separation of fibrin when lymph coagulated ; Reuss and Emmert discovered the lymph corpus- 
 cles. The chemical investigations date from the first quarter of this century ; they were carried out 
 by Lassaigne, Tiedemann, Gmelin and others. The last two observers noticed that the white color 
 of chyle was due to the presence of small, fatty granules. 
 
Physiology of animal Heat. 
 
 206. SOURCES OF HEAT.— Heat.— The heat of the body is an unin- 
 terrupted evolution of kinetic energy, which we must represent to ourselves as due 
 to vibrations of the corporeal atoms. The ultimate source of the heat is contained 
 in the potential energy taken into the body with the food, and with the O of the 
 air absorbed during respiration. The amount of heat formed depends upon the 
 amount of energy liberated (see Introduction). 
 
 The energy of the food stuffs may be called " latent heat," if we assume that 
 when they are used up in the body — chiefly by a process of combustion — kinetic 
 
 . Fig. 214. 
 
 Water calorimeter of Favre and Silbermann. 
 
 energy is liberated only in the form of heat. As a matter of fact, however, 
 mechanical energy and electrical energy are developed from the potential energy. 
 In order to obtain a unit measure for the energy liberated, it is advisable to ex- 
 press all the potential energy as heat units. 
 
 The Calorimeter. — This instrument enables us to transform the potential 
 energy of the food into heat, and, at the same time, to measure the number of 
 heat units produced. 
 
 347 
 
348 CHEMICAL SOURCES OF HEAT. 
 
 Favre and Silbermann used a water calorimeter (Fig. 214). The substance to be burned is 
 placed in a large cylindrical combustion chamber (K), suspended in a large cylindrical vessel (L) 
 filled with water (w), so that the combustion chamber is completely surrounded by the water. Three 
 tubes open into the upper part of the chamber; one of them (O) supplies the air which is necessary 
 for combustion ; it reaches almost to the bottom of the chamber ; the second tube (a) is fixed in the 
 middle of the lid, and is closed above with a thick glass plate, and on this is placed, at an angle, a 
 small mirror (s), which enables an observer to see into the interior of the chamber, and to observe 
 the process of combustion at c. The third tube (d) is used only when combustible gases are to be 
 burned in the chamber. It can be closed by means of a stop-cock. A lead tube (e, e) with many 
 twists on it, passes from the upper part of the chamber through the water, and finally opens at g. 
 The gaseous products of combustion pass out through this tube, and in doing so help to heat the 
 water. The cylindrical vessel with the water is closed with a lid which transmits the four tubes. 
 The water cylinder stands on four feet within a large cylinder (M), which is filled with some good 
 non-conductor of heat, and this again is placed in a large vessel filled with water (W). This is to 
 prevent any heat reaching the inner cylinder from without. A weighed quantity of the substance 
 (c) to be investigated, is placed in the combustion chamber. When combustion is ended, during 
 which the inner water must be repeatedly stirred, the temperature of the water is ascertained by 
 means of a delicate thermometer. If the increase of the temperature and the amount of water are 
 known, then it is easy to calculate the number of heat units produced by the combustion of a 
 known weight of the substance (see Introduction). 
 
 The ice calorimeter may also be used. The inner cylinder is filled with ice and not with water, 
 and ice is also placed in the outer cylinder, to prevent any heat from without from acting upon the 
 inner ice. The heat given off from the combustion chamber causes a certain amount of the ice to 
 melt, and the water thereby produced is collected and measured. It requires 79 heat units to melt 
 I grm. of ice to I grm. of water at o° C. 
 
 Just as in a calorimeter, although much more slowly, the food stuffs within our 
 body are burned up, oxygen being supplied, and thus potential energy is trans- 
 formed into kinetic energy, which in the case of a person at rest, i. <?., when the 
 muscles are inactive, almost completely appears in the form of heat (see Introduc- 
 tion). 
 
 Heat Units. — Favre, Silbermann, Frankland, Rechenberg, B. Danilewsky, and others have 
 made calorimetric experiments on the heat produced by food. Thus, I gramme of the following 
 dry substances yields heat units : — 
 
 Casein 
 
 S78S 
 
 Alcohol . 
 
 . 8 9S 8 
 
 Potatoes . . 
 
 ■ 3752 
 
 Stearin . 
 
 . 9036 
 
 Milk . . . 
 
 • 5°93 
 
 Falmitin . 
 
 . 8883 
 
 Bread . . 
 
 3984 
 
 Olein . . 
 
 • 8958 
 
 Rice . . . 
 
 . 3813 
 
 Glycerin . 
 
 • 4179 
 
 Starch . . . 
 
 • 4479 
 
 Leucin . 
 
 . 6141 
 
 Yelk of egg 
 
 . 6460 
 
 Creatin . 
 
 . 4118 
 
 Peptone . . .4914 
 Glutin . . . 5493 
 Chondrin . . 4909 
 Flesh extract 
 (Liebig) . . 3216 
 
 Grape sugar . 3939 
 
 Cane sugar . 4173 
 
 Milk sugar . . 4162 
 
 Vegetable fibrin 6231 
 
 Glutin . . 6141 
 
 Legumin . 5573 
 
 Blood fibrin . 5709 
 
 As albumin is only oxidized to the stage of urea, we must deduct the heat units obtainable from 
 • urea from those of albumin, and as I part of albumin yields in round numbers about \ of urea, we 
 ■ obtain about 5100 calories [^=2170 kilogram metres] for 1 grm. of albumin. 
 
 Isodynamic foods, i.e., those that produce a similar amount of heat; 100 grms. animal albumin 
 (after deducting the heat units of urea) = 52 fat, = 1 14 starch = 129 dextrose ; too grms. of vege- 
 table albumin = 55 fat, = 121 starch = 137 dextrose {Danilewsky). Rubner calculated that in 
 man, with a mixed diet, the available heat units for 1 grm. of albumin = 4100 ; I grm. fat = 9300 ; 
 and for I grm. carbohydrate = 4100 calories. 
 
 When we know the weight of any of the above-named substances consumed by 
 a man in twenty-four hours, a simple calculation enables us to determine how many 
 heat units are formed in the body by oxidation, i. e., provided the substance is 
 completely oxidized. 
 
 Sources of Heat. — The individual sources of heat are to be found in the 
 following : — 
 
 (1) In the transformation of the chemical constituents of the food, endowed with a 
 large amount of potential energy, into such substances as have little or no energy. 
 The organic substances used as food consist of C, H, O, N, so that there takes 
 place— (a) Combustion of C into CO,, of H into H 2 0, whereby heat is pro- 
 duced ; 1 grm. C burned to produce C0 2 yields 8080 heat units, while 1 grm. H 
 oxidized to H 2 yields 34,460 heat units. The O necessary for these purposes is 
 absorbed during respiration, so that, to a certain extent at least, the amount of 
 
PHYSICAL SOURCES OF HEAT. 349 
 
 heat produced may be estimated from the amount of O consumed. The same 
 consumption of O gives rise to the same amount of heat whether it is used to 
 oxidize H or C (JPjluger). There is a relation, amounting to cause and effect, 
 between the amount of heat produced in the body and the O consumed. The 
 cold-blooded animals, which consume little O, have a low temperature ; among 
 warm-blooded animals, i kilo, of a living rabbit takes up within a hour 0.914 grm. 
 O, and its body is heated to a mean of 38 C. 1 kilo of a living fowl uses 1.186 
 grms. O, and gives a mean temperature of 43.9° C. (Regnault and Reiset). The 
 amount of heat produced is the same whether the combustion occurs slowly or 
 quickly; the rapidity of the metabolism, therefore, affects the rapidity, but not 
 the absolute amount of heat production. The combustion of inorganic substances 
 in the body, such as the sulphur into sulphuric acid, the phosphorus into phosphoric 
 acid, is another, although very small, source of heat. 
 
 (b) In addition to the processes of combustion or oxidation, all those chemical 
 processes in our body, by which the amount of the available potential energy 
 which is present is diminished" in consequence of a greater satisfaction of atomic 
 affinities, lead to the production of heat. In all cases where atoms assume more 
 stable positions with their affinities satisfied, chemical energy passes into kinetic 
 thermal energy, as in the alcoholic fermentation of grape sugar, and other similar 
 processes. 
 
 Heat is also developed during the following chemical processes : — 
 
 (a) During the union of bases with acids (Andrews). The nature of the base determines the 
 amount of heat produced, while the nature of the acid is without effect. Only in those cases where 
 the acid, e.g., C0 2 , is unable to set aside the alkaline reaction, the amount of heat produced is less. 
 The formation of compounds of chlorine (e.g., in the stomach) produces heat. 
 
 (6) When a neutral salt is changed into a basic one (Andrews). In the blood the sulphuric and 
 phosphoric acids derived from the combustion of S and P are united with the alkalies of the blood 
 to form basic salts. The decomposition of the carbonates of the blood by lactic and phosphoric 
 acids forms a double source of heat, on the one hand, by the formation of a new salt, as well as by 
 the liberation of C0 2 , which is partly absorbed by the blood. 
 
 (c) The combination of haemoglobin with O (| 36). 
 
 In connection with those chemical processes, whereby the heat of the body is 
 produced, heat-absorbing intermediate compounds are not unfrequently formed. 
 Thus, in order that the final stage of more complete saturation of the affinities be 
 reached, intermediary atomic groups are formed, whereby heat is absorbed. Heat 
 is also absorbed when the solid aggregate condition is dissolved during retrogres- 
 sive processes. But these intermediary processes, whereby heat is lost, are very 
 small compared with the amount of heat liberated when the end products are 
 formed. 
 
 (2) Certain physical processes are a second source of heat : (a) The 
 transformation of the kinetic mechanical energy of internal organs, when 
 the work done is not transferred outside the body, produces heat. Thus the whole 
 of the kinetic energy of the heart is changed into heat, owing to the obstructions 
 which are opposed to the blood stream (§ 93). The same is true of the mechanical 
 energy evolved by many muscular viscera. The torsion of the costal cartilages, 
 the friction of the current of air in the respiratory organs and the ingesta in the 
 digestive tract, all yield heat. 
 
 An excessively minute amount of the mechanical energy of the heart is transferred to surrounding 
 bodies by the cardiac impulse and the superficial pulse beats, but this is infinitesimally small. During 
 respiration, when the respiratory gases and other substances are expired, a very small amount of 
 energy disappears externally, which does not become changed into heat. If we assume that the 
 daily work of the circulation exceeds 86,000 kilogram metres, the heat evolved is equal to 204,000 
 calories, in twenty-four hours ({} 93), which is sufficient to raise the temperature of a person of 
 medium size 2° C. 
 
 (i) When, owing to muscular activity, the body produces work which is trans- 
 ferred to external objects, e. g., when a man ascends a tower or mountain, or 
 throws a heavy weight, a portion of the kinetic energy passes into heat, owing to 
 
350 
 
 HOMOIOTHERMAL AND POIKILOTHERMAL ANIMALS. 
 
 friction of the muscles, tendons, and the articular surfaces, as well as to the shock 
 and pressure of the ends of the bones against each other. 
 
 (t) The electrical currents which occur in muscles, nerves, and glands very 
 ■ probably are changed into heat. The chemical processes which produce heat 
 evolve electricity, which is also changed into heat. This source of heat, however, 
 is very small. 
 
 {d) Other processes are the formation of heat from the absorption of C0 2 (ffenryi), by the con- 
 centration of water as it passes through membranes (Regnault and Pouillet), in imbibition (Mat- 
 teucci, 1834), formation of the solids, e. g., of chalk in the bones. After death, and In some patho- 
 logical processes during life, the coagulation of blood ( Valentin, Schiffer) and the production of 
 rigor mortis are sources of heat. 
 
 207. HOMOIOTHERMAL AND POIKILOTHERMAL ANI- 
 MALS. — In place of the old classification of animals into " cold blooded " 
 and " warm blooded," another basis of classification seems desirable, viz., the 
 relation of the temperature of the body to the temperature of the surrounding 
 medium. 
 
 Bergmann introduced the word homoiothermal for the warm-blooded ani- 
 mals (mammals and birds), because these animals can maintain a very uniform 
 temperature, even although the surrounding temperature be subject to considerable 
 variations. The so-called cold-blooded animals are called poikilothermal, 
 because the temperature of their bodies rises or falls, within wide limits, with the 
 heat of the surrounding medium. ' 
 
 When homoiothermal animals are kept for a long time in a cold medium, 
 their heat production is increased, and when they are kept for a long time in a 
 warm medium it is diminished. 
 
 Fordyce gave a proof of the nearly uniform temperature in man. A man remained ten minutes 
 in an oven containing very dry hot air (§ 218), and yet the temperature of the palm of his hand, 
 mouth, and urine was increased only a few tenths of a degree. Becquerel and Brechet investigated 
 the temperature of the human biceps (by means of thermo-electric needles), when the arm had been 
 one hour in ice, and yet the temperature of the muscular tissue was cooled only 0.2° C. The same 
 muscle did not undergo any increase in temperature, or at most o.2° C, when the man's arm was 
 placed for a quarter of an hour in water at 42° C. 
 
 If heat be rapidly abstracted (§ 225) or rapidly supplied (§ 221) to the body, 
 so as to produce rapid variation of the temperature, life is endangered. 
 
 Poikilothermal animals behave very differently; the temperature of their 
 bodies generally follows, although with considerable variations, the temperature of 
 the surroundings. When the temperature of the surroundings is increased, the 
 amount of heat produced is increased, and when the surrounding temperature 
 falls, the amount of heat evolved within the body also falls. 
 
 The following table shows very clearly the characters of poikilothermal animals, e. g. t frogs 
 (Rana esculenta), which were placed in air and water of varying temperatures. The frogs were 
 fixed to an iron support, and immersed up to the mouth. The temperature was measured by means 
 of a thermometer introduced through the mouth into the stomach. 
 
 In Water. 
 
 In Air. 
 
 Temperature of the 
 Water. 
 
 Temperature of Frog's 
 Stomach. 
 
 Temperature of the 
 Air. 
 
 Temperature of Frog's 
 Stomach. 
 
 41.0° c. 
 
 35-2 
 
 30.0 
 
 23.0 
 
 20.6 
 
 11.5 
 
 5-9 
 2.8 
 
 38.0° c. 
 
 34-3 
 29.6 
 22.6 
 20.7 
 12.9 
 
 8.0 
 
 S-3 
 
 40.4° c. 
 
 35.8 
 
 27.4 
 19.8 
 
 16.4 
 
 14.7 
 
 6.2 
 
 5-9 
 
 31.7° c. 
 
 24.2 
 19.7 
 15.6 
 14.6 
 10.2 
 7.6 
 
 8.6 
 
THERMO-ELECTRIC MEASUREMENT OF HEAT. 
 
 351 
 
 [Temperature of Different Animals. 
 
 Sparrow 
 
 Swallow . . 
 Gull . . . 
 
 Temp. 
 . . . 44-03 
 
 - - -37-8 
 
 Mammals. 
 
 Horse . . 
 Rat . . . 
 
 . . . 37.20 
 
 . 36.80-37.50 
 
 . 38.80 
 
 Hare . . . 
 
 . . . 3780 
 
 Cat . . . 
 Guinea pig 
 
 38.30-38.90 
 . . . . 38-80 
 
 Dog . . . 
 
 1 37-40 
 
 - - i 3900 
 
 (.39.60 
 
 Temp. 
 
 Panther 38.90 
 
 Mouse 41. 1 
 
 Dolphin 35.5 
 
 Sheep 
 
 Ape 35.50 
 
 Guinea pfg . . 35.76-38.00 
 Rabbit . . . 37.50-38.00 
 
 Ox 37.50 
 
 Ass 36.95 
 
 (Gavarret and Rosenthal)] 
 
 Birds. 
 
 Temp. 
 Thalassidroma . . . 40.30 
 
 Procellaria 40.80 
 
 Goose 41-70 
 
 f 39.08 
 
 • • 1 42.10 
 
 Pigeon . . . 41.80-42.50 
 
 Turkey 42.70 
 
 Guinea fowl .... 43.90 
 
 Duck j «.90 
 
 1 42.50 
 Crow 41.17 
 
 Reptiles. — Snakes, io°-iz°, but higher when incubating. Amphibians and fishes — 
 0-5 0- 3° above the temperature of the surroundings. Artkropoda — o.i°-5.8° above the 
 surroundings. Bees in a hive, 30°-32°, and when swarming, 40°. The following 
 animals have a temperature higher than the surrounding temperature : Cephalopods, 
 0.57 ; molluscs, 0.46 ; echinoderms, 0.40 : medusas, 0.27; polyps, 0.21 ° C. 
 
 208. ESTIMATION OF TEMPERATURE— THERMOMETRY.— 
 Thermometry. — By using thermometric apparatus, we are enabled to obtain informa- 
 tion regarding the degree of heat of the body to be investigated. For this purpose the 
 following methods are employed : — 
 
 (A) The Thermometer {Galileo, 1603). — Sanctorius made the first thermometric 
 observations on man (1626). Celsius (1701-1744) divided his thermometer into 100 
 parts, and each part was again divided into 10 parts, so that ^° C. could be easily 
 read off. All thermometers which have been used for a long time give too high read- 
 ings (Bellani), hence they should be compared, from time to time, with a normal 
 thermometer. When taking the temperature, the bulbs ought to be surrounded for fif- 
 teen minutes, and during the last five minutes the mercury column ought not to vary. 
 A very sensitive thermometer will indicate the temperature after seven seconds if the 
 urine stream be directed upon its bulb (Oertmann). Minimal and Maximal ther- 
 mometers are often of use to the physician. 
 
 Walferdin's metastatic thermometer (Fig. 215) is specially useful for compara- 
 tive observation. The tube is very narrow in comparison with the bulb, and in order 
 that the stem be not too long, it is constructed so that the amount of mercury can be 
 varied. A quantity of mercury is taken, so that with the temperature expected the 
 thread of mercury will stand about the middle of the stem. A small bulb at the upper 
 part of the stem receives the excess of Hg. Suppose a temperature between 37°-40°, 
 C. is to be measured, the bulb is first heated a little over 40" C, it is then suddenly 
 cooled, and shaken at the same time, so that the thread of mercury is thereby suddenly 
 broken above 40 . The tube is so narrow that 1° C. is equal to about 10 centimetres 
 of the length of the tube, so that T ^° C. is still 1 millimetre in length. The scale is 
 divided empirically, but the valve of the divisions must be compared with a normal 
 thermometer. 
 
 Kronecker and Meyer used very small maximal " outflow thermometers " (Dulong 
 and Petit), and caused them to pass through the intestinal canal, or through large blood 
 vessels. The mercury flows out of the short open tube, and, of course, more flows out 
 the higher the temperature. After these small tubes have passed through the animal, 
 a comparison is instituted with a normal thermometer, to determine at what tempera- 
 ture the mercury reaches the free margin of the tube. 
 
 (B) Thermo-electric Method. — This method enables us to determine the metas- 
 tatic temperature accurately and rapidly (Fig. 216, I). The thermo-electric galvano- 
 meter of Meissner and Meyerstein consists of a circular magnet (m), suspended by a 
 thread of silk (c), to which a small mirror (S) is attached. A large stationary bar 
 magnet (M) is placed near the magnet (m), so that the north poles (« and N) or both 
 magnets point in the same direction, and it is so arranged that the suspended magnet is 
 caused to point to the north by a minimal action of M. A thick copper wire (6, b) is 
 coiled several times round m (although in the figure it is represented as a single coil), 
 and the ends of the wire are soldered to two thermo elements, each composed of two 
 different metals, iron and German silver, the two similar free elements being united 
 by a wire (b^), so that the two thermo elements form part of a closed circuit. A 
 horizontal scale (K, K) is placed at a distance of 3 metres from the mirror, so that the 
 the scale are seen in the mirror. The scale itself rests upon a telescope (F) directed 
 mirror. The observer (B)'who looks through the telescope can see the divisions of the 
 
 Fig. 215. 
 
 w 
 
 Walferdin's 
 
 metastatic 
 
 thermometer. 
 
 divisions of 
 toward the 
 scale in the 
 
352 
 
 THERMO-ELECTRIC MEASUREMENT OF HEAT. 
 
 mirror. When the magnet, and with it the mirror, swing out of the magnetic meridian, the 
 observer notices other divisions of the scale in the mirror. When one of the thermo elements is 
 heated, an electrical current is produced, which passes from the iron to the German silver in the 
 heated couple, and causes a deviation of the suspended magnet. Suppose a person were swimming 
 in the direction of the current in the conducting wire, then the north pole of the magnet goes to 
 the north (Ampire). The tangent of the angle <p, through which the freely movable magnet is 
 diverted by a galvanic current, from its position of rest or zero, in the magnetic meridian, is the same 
 
 p 
 as the galvanic stream ; G is proportional to the magnetic energy D, i. *.. tang, tp = — • If G is 
 
 
 Scheme of thermo-electric arrangements for estimating the temperature. 
 
 to remain the same, and the tang. <p to be as large as possible, the magnetic energy must be dimin- 
 ished as much as possible. If the magnetism of the suspended magnet be indicated by m, and that 
 of the earth by T, the magnetic directing energy D = Tm, so that D can be diminished in two 
 ways : (l) by diminishing the magnetic moment of the suspended magnet, as may be done by using 
 a pair of astatic needles, such as are used in Nobili's galvanometer ; (2) and also by weakening 
 the magnetism of the earth, by placing an accessory stationary magnet (Hauy's rod) in the same 
 direction, and near the suspended magnet. An important arrangement for rapidly getting the mag- 
 net to zero is the dead-beat arrangement of Gauss (not figured in the scheme). It consists of a thick 
 copper cylinder, on which the wire of the coil is wound. This mass of copper may be regarded as 
 
TEMPERATURE TOPOGRAPHY. 353 
 
 a closed multiplicator with a very large transverse section. The vibrating magnet induces a current 
 of electricity in this closed circuit, whose intensity is greatest when the velocity of the excursion of 
 the magnet is greatest, and which takes the opposite direction as soon as the magnet returns toward 
 zero. These induced currents cause a diminution of the vibrations of the magnet in this way, that 
 the arc of vibration of the magnet diminishes very rapidly, almost in a geometrical progression. 
 The induced damping current is stronger, the less the resistance in the closed circuit, and in the 
 damper or dead-beat arrangement itself, the greater the section of the copper ring. This damping 
 arrangement limits the oscillation of the magnet, and it comes to rest rapidly and promptly afttr 
 three or four small vibrations, so that much time is saved. The angle of deviation is so small that 
 the angle itself may be taken instead of the tangent. 
 
 The thermo-electric needles of Dutrochet (II) may be placed in the circuit. They consist of 
 iron and German silver soldered at their points ; or the needles of Becquerel (III) may be used. 
 They consist of the same metals soldered in a straight line, one behind the other. The needles 
 must always be covered by a varnish, which will prevent the parenchymatous juices from acting 
 upon them, and so causing a current. Before the experiment we must determine what extent of ex- 
 cursion on the scale is obtained with a certain temperature. In order to determine this, a delicate 
 thermometer is fixed to each of the thermo couples, and both are placed in oil baths, which differ in 
 temperature — say by i° C. — as can be determined by the thermometer. When the current is closed, 
 the excursion on the scale will indicate 1° C. Suppose the excursion was 150 mm., then each mm. 
 of the scale would be equal to T £ 5 ° C. When this is determined, the two thermo needles may be 
 placed in the different tissues or organs of animals, and, of course, we obtain the difference of tem- 
 perature in these places. Or one thermo couple may be placed in a bath of constant temperature 
 (nearly that of the body), in which is placed a delicate thermometer, while the other needle is intro- 
 duced into the organ to be investigated. In this case, we obtain the difference of temperature be- 
 tween the tissue and the source of the constant heat. The electric current passes in the warmer 
 needle from the iron to the German silver, and thus through the wires of the apparatus. For small 
 differences of temperature, such as occur in the body, the thermo-electric energy is always propor- 
 tional to the difference of temperature of the two needles or couples. In place of a single pair of 
 needles several may be used, whereby the sensitiveness of the apparatus is greatly increased. Helm- 
 holtz found that by using sixteen antimony-bismuth couples he could detect an increase of ? ^Vl° C. 
 Schiffer prepared a simple thermo pile (IV) by soldering together alternately four pairs of wires of 
 iron (/) and German silver (o). These are placed in the two organs (A and B), which are to be 
 investigated, whereby a very high degree of exactness is obtained. 
 
 209. TEMPERATURE TOPOGRAPHY.— Although the blood, in 
 virtue of its continual motion, completing, as it does, the circulation in twenty- 
 three seconds, must exercise a very considerable influence on the equilibration of 
 the temperature in different organs, nevertheless a completely uniform temperature 
 does not exist, and the temperature varies in different parts : — 
 
 1. Temperature of the Skin. 
 
 Middle of the sole of the foot . . 32.26 C. 
 
 Near tendo-Achillis 33^5 
 
 Anterior surface of leg 33'°5 
 
 Middle of calf 33.85 
 
 Bend of knee 35'CO 
 
 Middle of upper arm 35-4° 
 
 Inguinal fold .......... 35.80 
 
 Near cardiac impulse . . . . 34.40 
 
 J. Davy made these observations directly after 
 standing, while naked, with the tempera- 
 ture of the room at 21° C. Only the under 
 surface of the thermometer touched the 
 skin. 
 
 In the closed axilla, 36.49 (mean of 505 individuals) ; — 36.5 to 37.25 ( Wunderlich) ; — 36.89 C. 
 
 (Liebermeister). 
 
 The temperature of the skin of the head is higher in the forehead and parietal region than in the 
 occipital region; the left side is warmer than the right {Maragliano). Dyspnoea increases the 
 temperature of the skin (Heidenhain, Frankel). 
 
 Method. — Liebermeister determines the temperature of free cutaneous surfaces thus : The 
 bulb of the thermometer is heated slightly above the temperature expected ; after the mercury begins 
 to fall, the bulb is placed on the skin, and if the bulb has the same temperature as the skin, the 
 mercury remains stationary. This experiment must be repeated several times. 
 
 2. Temperature of the Cavities. 
 
 Mouth under the tongue 37.19 C, 
 
 Rectum 38.01 
 
 Vagina 38.30 
 
 (Uterine cavity somewhat warmer; cervical canal somewhat cooler.) 
 Urine 37.03 
 
 2 3 
 
354 
 
 CONDITIONS AFFECTING THE TEMPERATURE OF ORGANS. 
 
 The temperature falls in the stomach during digestion (§ 166, i). Cold in- 
 jections (n° C.) into the rectum rapidly lower the temperature in the stomach i° 
 C. {Winternitz). 
 
 3. The temperature of the Blood is, as a mean, 39° C. The venous blood 
 in internal viscera is warmer than the arterial, but it is cooler in peripheral 
 parts : — 
 
 Blood of the right heart . . . . 38.8 
 
 " left heart 38.6 
 
 " aorta 38.7 
 
 " hepatic veins .... 39.7 
 (CI. Bernard). 
 
 Blood of the superior vena cava . . 36 78° 
 " inferior vena cava . . 38.1 1 
 
 " crural vein 37.20 
 
 v. Liebig. 
 
 The lower temperature of the blood in the left heart may be explained by the blood becoming 
 cooled in its pai-sa^e through the lungs during respiration. According to Heidenhain and Korner, 
 the right heart is slightly warmer because it lies in relation with the warm liver, while the left heart 
 is surrounded by the lung which contains air. This observation of Malgaigne (1832), Berger, and 
 G. v. Liebig is disputed by others, who say that the left heart is slightly warmer (Jacobson and 
 Bernhardt) because the combustion processes are more active in arterial blood, and heat is evolved 
 during the formation of oxyhaemoglobin ( Gamgee). The blood in the veins is usually cooler than 
 in the corresponding arteries (Holier), owing to the superficial position of the former, whereby they 
 give off heat during their long course ; thus the blood of the jugular vein is ]/ 2 to 2° C. lower than 
 the blood in the carotid (Colin) ; the crural vein ^ to 1° cooler than in the crural artery (Becque- 
 rel and Brechet). Superficial veins, more especially than those of the skin, give off much heat, 
 and their blood is, therefore, somewhat cooler. The warmest blood is that of the hepatic vein, 
 39. 7 C. (CI. Bernard), partly owing to the great chemical changes which occur within the liver 
 owing to its secretory activity (\ 210, a), and partly to its protected situation. 
 
 (4) Temperature of the Tissues. — The individual tissues are warmer — (1) 
 the greater the transformation of kinetic energy into heat, i. e. , the greater the 
 tissue metabolism ; (2) the more blood they contain ; (3) and the more protected 
 their situation. According to Heidenhain and Korner, the cerebrum is the warm- 
 est organ in the body. 
 
 Berger measured the temperature of the tissues of a sheep, and found — 
 
 Subcutaneous tissue 37-35° C. "J While the temperature was in — 
 
 Brain 40.25 ( Rectum 40.67 C. 
 
 Liver 41 .25 r Right heart 41.60 
 
 Lungs 4I-50 J Left heart 40.90 
 
 Becquerel and Brechet found the temperature of the human subcutaneous tissue to be 2.1° C. 
 lower than that of the neighboring muscles. The horny tissues do not produce heat, and their 
 low temperature is due to the conduction of heat from the parts on which they grow. The tem- 
 perature of the cornea partly depends on that of the iris, and the more contracted the pupil is, it 
 receives more heat from the blood vessels of the iris. 
 
 210. CONDITIONS AFFECTING THE TEMPERATURE OF 
 ORGANS. — The temperature of the individual organs is by no means constant ; 
 it is influenced by many conditions ; among these are the following : — 
 
 (1) The more heat that is produced independently within a part, the higher is its 
 temperature. As the amount of heat produced within a part depends upon its 
 metabolism, therefore, when the metabolism is increased, the amount of heat pro- 
 duced is similarly increased. 
 
 (a) Glands produce more heat during the act of secretion, as is proved by 
 the higher temperature of their secretion, or by the higher temperature of the 
 venous blood flowing out of their veins. 
 
 Ludwig found that when he stimulated the chorda tympani, the saliva of the submaxillary gland 
 was 1.5° C. warmer than the blood in the carotid, which supplied the gland with blood (p. 239). 
 The blood in the renal vein in a kidney which is secreting is warmer than the blood in the renal 
 artery. The secreting liver produces much heat (J 178). CI. Bernard investigated the tempera- 
 ture of the blood of the portal and hepatic veins during hunger, at the beginning of digestion, 
 and when digestion was most active, and he found : — 
 
 Temperature of portal vein 37. 8° C. "I After 4 days / Blood of right heart, 38.8°. 
 
 " hepatic vein . ... 38.4 J starvation. \ (Hunger period.) 
 
CONDITIONS AFFECTING THE TEMPERATURE OF ORGANS. 355 
 
 Temperature of portal vein 39-9° C. 1 Beginning of 
 
 " hepatic vein 39.5 / digestion. 
 
 Temperature of portal vein 39.7 1 Digestion most J Blood of right heart during 
 
 " hepatic vein 41.3 j active. \ digestion, 39. 2°. 
 
 In the dog a moderate diet, chemical or mechanical stimulation of the gastric mucous membrane, 
 or even the sight of food, raises the temperature in the stomach and intestine. 
 
 (b) When the muscles contract they evolve heat (fiunsen, i8oj). Davy 
 found that an active muscle became 0.7° C. warmer; while Becquerel (1835), by 
 means of a thermo-galvanometer, found that human muscles, when kept con- 
 tracted for five minutes, became i° C. warmer (§ 302). 
 
 This is one of the reasons why the temperature may rise above 40 during rapid running A 
 temperature obtained by energetic muscular action usually does not fall to the normal until after 
 resting for I U hours (Billroth). The low temperature of paralyzed limbs depends partly upon the 
 absence of the muscular contractions. 
 
 (V) With regard to the effect of sensory nerves upon the temperatures, some 
 of the chief points to ascertain are whether the circulation is accelerated or re- 
 tarded by their stimulation, or whether the respiration is increased or diminished 
 (§ 214, II, 3), and whether the muscles of the skeleton are relaxed or contracted 
 reflexly (§ 214, I, 3). In the former case the temperature of the interior and 
 rectum is increased ; in the latter, diminished. 
 
 That there are heat-regulating nerve centres has not been definitely proved ; with regard to the 
 influence of vasomotor nerves ($ 371). 
 
 (</) The temperature of the body rises during mental exertion. Davy ob- 
 served an increase of 0.3 C. after vigorous mental exertion. 
 
 Lombard observed that the temperature of the forehead rose 0.5 C. during mental activity and 
 emotional disturbances. The part of the forehead corresponded to the posterior region of both 
 upper frontal convolutions, to the anterior central convolution, and (?) to the anterior part of the 
 posterior central convolution. The temperature was higher on the left side. 
 
 (e) The parenchymatous fluids, serous fluids, and lymph produce little heat, 
 owing to their feeble metabolism, hence they have the same temperature as their 
 surroundings ; the epidermal and horny tissues do not produce heat, they merely 
 conduct it from subjacent structures. 
 
 (2) The temperature depends, to a large extent, upon the amount of blood in an 
 organ, and also upon the rapidity with which blood is rennved by the circulation. 
 This is best observed in the difference of the temperature between a cold, pale, 
 bloodless hand and a warm, red, congested one. 
 
 Becquerel and Brechet found that the temperature of the human biceps fell several tenths of a 
 degree, when the axillary artery was compressed. Ligature of the iliac artery in a dog caused a fall 
 of )4° C within eighteen minutes; while the removal of the ligature caused the temperature to rise 
 rapidly to normal. Ligature of the crural artery and vein in a dog causes a fall of several degrees 
 {Landois). If the extremities be kept suspended in the air, they become bloodless and cold. 
 
 Liebermeister has pointed out a difference with regard to the external and internal parts of the 
 body. The external parts give off more heat than they produce, so that they become cooler the 
 more slowly new blood flows into them, and warmer the greater the rapidity of the blood stream 
 through them. Acceleration of the blood stream, therefore, causes the temperature of peripheral 
 parts to approximate more and more to the temperature of internal organs, while retardation of the 
 blood stream causes them to approach the temperature of the surrounding medium. Exactly the 
 reverse is the case with internal parts, where a large amount of heat is produced, and heat is given 
 up almost alone to the blood which flows through them. Their temperature must fall when the 
 blood stream through them is accelerated, and it is raised when the blood stream is retarded (Hei- 
 denhain). Hence it follows, that the greater the difference of the temperature between peripheral 
 and internal parts, the slower must be the velocity of the circulation. 
 
 (3) If the position of an organ be such, or if other conditions cause it to 
 give off heat by conduction or radiation, then its temperature falls. 
 
 A good example of this is the skin, which varies greatly in temperature according to the tempera- 
 ture of the surrounding medium, whether it is covered or uncovered, whether it is dry or moist with 
 sweat (which abstracts heat when it evaporates). When much cold food or drink is taken the 
 
356 
 
 SPECIFIC HEAT OF THE BODY. 
 
 stomach is cooled, and when ice cold air is breathed the respiratory passages as far as the 
 bronchi are cooled. • 
 
 2ii. ESTIMATION OF HEAT— CALORIMETRY.— Calorimetry 
 
 is the method of determining the amount of heat possessed by any body, or what 
 amount of heat it is capable of producing. The unit of measurement is the 
 "heat unit," i. e., the amount of heat (or potential energy) required to raise 
 the temperature of i gramme of water, i° C. (see Introduction). 
 
 Experiment has shown that equal quantities of different substances require very unequal amounts 
 of heat to raise them to the same temperature, e. g., I kilo, water requires nine times as much heat 
 as I kilo, iron to raise it to the same temperature. In the human body, therefore, which is com- 
 posed of very different substances, unequal amounts of heat will be required to raise them all to the 
 same temperature. The same amount of heat transferred to two different substances will raise them 
 to different temperatures. Hence, bodies of different temperatures may contain equal amounts of 
 heat. The amount of heat required to raise a definite quantity (e. g., I grm.) of a substance to a 
 certain higher degree (e. g., i° C.) is called " specific heat " ( Wilkie, 1780). The specific heat 
 of water (which of all bodies has the highest specific heat) is taken as = 1. By " heat capacity " 
 is meant, that property of bodies in virtue of which they must absorb a given amount of heat in 
 order to have a certain temperature (Crawford). 
 
 Calorimetry is employed : I. To determine the specific heat of the different organs 
 
 Fig. 217. 
 
 Kopp's apparatus for the estimation of specific heat. 
 
 of the body. Only a few observations have been made. The mean specific 
 heat of the following animal parts (water = 1) is~- 
 
 Human blood 
 
 = 
 
 1.02 
 
 ( ? ) 
 
 Compact bone 
 
 = 0.3 
 
 Arterial blood 
 
 = 
 
 1.031 
 
 ( ? ) 
 
 Spongy bone 
 
 = 0.71 
 
 Venous blood 
 
 = 
 
 0.892 
 
 ? ) 
 
 Fat tissue 
 
 = 0.712 
 
 Cow's milk 
 
 = 
 
 0.992 
 
 
 Striped muscle 
 
 = 0.825 
 
 Human muscle 
 
 = 
 
 0.741 
 
 
 Defibrinated blood 
 
 = 0.927 
 
 Ox muscle 
 
 = 
 
 0.787 
 
 
 
 (/. Rosenthal) 
 
 The specific heat of the human body, as a whole, is about that of an equal 
 volume of water. 
 
 Method. — Kopp has estimated the specific heat of solids and fluids thus (Fig. 217) : The solid 
 to be investigated is broken in pieces about the size of a pea, and placed in a test tube, A, with thin 
 walls, which is closed above with a cork, from which a copper wire with a hook on it projects. 
 The test tube contains a certain quantity of fluid which does not dissolve the substance, but which 
 lies between its pieces and covers it. It is weighed three times, to ascertain the weight, (t) of the 
 empty glass, (2) after it is filled with the solid substance, (3) after the fluid is added, so that we 
 obtain the weight of the solid substance, m, and that of the fluid/. The test tube and its contents 
 are placed in a mercury bath, BB, and this again in an oil bath, CC, and the whole is raised to a 
 high temperature. Into BB there is introduced a fine thermometer, T. When the tube, A, has 
 reached the necessary temperature (say 40 ) it is rapidly placed in the water of the accompanying 
 
THERMAL CONDUCTIVITY OF ANIMAL TISSUES. 357 
 
 calorimeter box, DD. The water in this box, which also contains a thermometer, D, is kept in 
 motion until it has completely absorbed all the heat given off by A. Let T represent the tempera- 
 ture to which A and its contents were raised in the mercury bath, and T t the temperature to which 
 it fell in the calorimeter; let s be the specific heat, and m the weight of the solid substance in the 
 test tube, while a and f- represent the specific heat of the weight of the interstitial fluid in the test 
 tube ; and lastly, let iv equal the amount of water in contact with A, which absorbs and gives off 
 heat ; then W represents the amount of heat which the test tube and its contents give off during 
 cooling. 
 
 W = (s. m + w + a. fi) T — T x ). 
 The amount of heat, W lf absorbed by the calorimeter is 
 
 W 1 = M (/,—/), 
 where M represents the amount of water in the calorimeter, and t the original temperature of the 
 water in the calorimeter, and ( 1 the temperature to which it is raised by placing A in it. If W and 
 Wj are equal, then 
 
 the specific heat, s = M (/ x - Q - (, + «r AQ (T - T x ) 
 
 r J m (T — TJ 
 
 If a fluid substance is placed in the test tube, and its weight = m, and its specific heat = s, the 
 formula for the specific heat of the fluid to be investigated is — 
 
 M(V x -<)-»(T-T x ) 
 »»(T-T X ) 
 This is a subject which has been very slightly investigated. J. Rosenthal, in his researches, used 
 an ice calorimeter ($ 206). 
 
 II. Calorimetry is more important for determining the amount of heat produced 
 in a given time by the body as a whole, or by its individual parts. 
 
 Lavoisier and Laplace made the first calorimetic observations on animals in 1783, by means of 
 an ice calorimeter; a guinea pig melted 13 oz. of ice in ten hours. Crawford, and afterward 
 Dulong and Despretz (1824), used Rumford's water calorimeter, which is similar to the one already 
 described, viz., of Favre and Silbermann. Small animals are placed in the inner thin-walled copper 
 chamber (K), which is placed in a water bath surrounded on all sides by some non-conducting 
 material. We require to know the amount of water, and its original temperature. The number 
 of calories is obtained from the increase of the temperature at the end of the experiment, which 
 lasts several hours. The air is supplied to the animal through a special apparatus resembling a 
 gasometer. The amount of C0 2 in the gases evolved is estimated chemically. 
 
 According to Despretz, a bitch forms 14,610 heat units per hour — i. e., 393,000 
 in twenty-four ho.urs. Other things being equal, a man seven times heavier than 
 this would produce in twenty-four hours about 2,750,000 calories. Senator found 
 that a dog weighing 6330 grms. produced 15,370 calories, and excreted at the 
 same time 367 grms. C(3 2 . The first calorimetric experiments on man were made 
 by Scharling (1849). Liebermeister estimated the amount of heat given off by 
 a man placed in a cold bath, which was surrounded with a woolen covering. 
 Leyden placed a lower limb in the calorimeter, whereby 6000 grms. water were 
 raised 1° C. in an hour. If we assume that the total superficial area of the body 
 is fifteen times greater than that of the leg, the human body would produce 
 2,376,000 calories in twenty-four hours. 
 
 212. THERMAL CONDUCTIVITY OF ANIMAL TISSUES.— The thermal con- 
 ductivity of animal tissues is of special interest in connection with the skin and subcutaneous fatty 
 tissue. The fatty layer under the skin, more especially in the whale, walrus, and seal, forms a pro- 
 tective covering, whereby the conduction of heat from interna] organs is rendered almost impossible. 
 Investigations upon this subject, however, are few. Griess (1870) attempted to estimate the thermal 
 conductivity by heating one part of the tissue, and determining when and in what direction pieces 
 of wax placed on the tissue to be investigated began, to melt. He investigated the stomach of the 
 sheep, the bladder, skin, hoof, horn, and bones of an ox, deer's horn, ivory, mother-of-pearl, shell 
 of haliotis. He found that fibrous tissues conducted heat more readily in the direction of their 
 fibres than at right angles to the course of the fibres. Hence, the figures obtained from the melted 
 wax were usually elliptical. Landois has made similar observations, and he finds that tissues con- 
 duct better in the direction of their fibres. After bones, blood clot was the best conductor, then 
 followed spleen, liver, cartilage, tendon, muscle, elastic tissue, nail and hair, bloodless skin, gastric 
 mucous membrane, washed fibrin. It is specially interesting to note how much better skin con- 
 taining Mood in its blood vessels conducts, compared with bloodless skin. Hence little heat is given 
 off from a bloodless skin, while congested skin conducts and gives off much more heat. 
 
358 
 
 VARIATIONS OF THE MEAN TEMPERATURE. 
 
 Like all other substances, the human body is enlarged by heat. A man weighing 60 kilos., and 
 whose temperature is raised from 37° C. to 40 C, is enlarged about 62 cubic centimetres. Con- 
 nective tissue (tendon) is extended by heat, while elastic tissue and the skin, like caoutchouc, are 
 contracted [Lombard and Walton). 
 
 213. VARIATIONS OF THE MEAN TEMPERATURE.— (1) 
 General Climatic and Somatic Influences. — In the tropics the mean tem- 
 perature of the body is about *^° C. higher than in temperate climates, where 
 again it is several tenths of a degree warmer than in cold climates {/. Davy) ; 
 but this has recently been denied by Boileau and Pinkerton. This difference is 
 comparatively trivial, when we remember that a man is subjected to a variation of 
 over 40 C. in passing from the equator to the poles. Observations on more than 
 4000 persons show that when a person goes from a warm to a cold climate his 
 temperature is but slightly diminished, but when he goes from a cold to a warm 
 climate his temperature rises relatively considerably more. In the temperate zone, 
 the temperature of the body during a cold winter is usually o.i° to 0.3 C. lower 
 than it is on a warm summer day. The elevation of a place above sea-level has 
 no obvious effect on the temperature of the body. There seems to be no difference 
 in different races, nor in the sexes, other conditions being the same. Persons 
 of powerful physique and constitution are said to have generally a slightly 
 higher temperature than feeble, weak, anaemic persons. 
 
 (2) Influence of the General Metabolism. — As the formation of heat de- 
 pends upon the transformation of chemical compounds, whose chief final pro- 
 ducts, in addition to H 2 0, are C0 2 and urea, the amount of heat formed must 
 go pari passu with the amount of these excreta. The more rapid metabolism 
 which sets in after a full meal causes a rise of temperature to several tenths of a 
 degree (" Digestion fever"). As the metabolism is much diminished during 
 hunger, this explains why the mean temperature in a fasting man is 36. 6°, while 
 it is 37.17° on ordinary days (Lichtenfels and FrohlicK) (§ 237). 
 
 Jiirgensen also found that the temperature fell on the first day of inanition (although there was a 
 temporary rise on the second day). In experiments made upon starving animals, the temperature at 
 first fell rapidly, then remained constant for a considerable time, while during the last days it fell 
 considerably. Schmidt starved a cat: on the 15th day the temperature was 38°.6; on the 1 6th, 
 38°.3; 17th, 37°.64; 18th, 35°.8 ; 19th (death) = 33°.o. Chossat found that starving mammals 
 and birds had a temperature 16° C. below normal on the day of their death. 
 
 (3) Influence of Age. — Age has a decided effect upon the temperature of the 
 body. The extent of the general metabolism is in part an index of the heat of 
 the body at different ages, but it is possible that other as yet unknown influences 
 are also active. 
 
 Age. 
 
 Mean Temperature at the 
 Ordinary Temperature. 
 
 Normal Limits. 
 
 "Where Measured. 
 
 Newly-born, 
 
 37.45° C. 
 
 37-3S-37-5S° c. 
 
 Rectum. 
 
 5-9 year, 
 
 37-72 
 
 36.87-37-62 
 
 Mouth and Rectum. 
 
 15-20 " 
 
 37-37 
 
 36. 1 2-38. 1 
 
 Axilla. 
 
 21-30 " 
 
 37.22 
 
 . . 
 
 a 
 
 25-30 " 
 
 36.91 
 
 
 tt 
 
 3I-40 " 
 
 37-1 
 
 36.25-37.5 
 
 it 
 
 41-50 " 
 
 36.87 
 
 
 tt 
 
 51-60 " 
 
 36.83 
 
 
 " 
 
 80 " 
 
 3746 
 
 
 Mouth. 
 
 Newly-born Animals exhibit peculiarities owing to the sudden change in 
 their conditions of existence. Immediately after birth, the infant is 0.3 warmer 
 than the vagina of the mother, viz., 37.86°. A short time after birth, the tem- 
 perature falls 0.9°, while twelve to twenty-four hours afterward it has risen to the 
 normal temperature of an infant, which is 37.45°. Several irregular variations 
 
VARIATIONS OF THE MEAN TEMPERATURE. 
 
 359 
 
 occur during the first weeks of life. During sleep, the temperature of an infant 
 falls 0.34 to 0.56 , while continued crying may raise it several tenths of a degree. 
 Old people, on account of their feeble metabolism, produce little heat ; they 
 become cold sooner, and hence ought to wear warm clothing to keep up their 
 temperature. 
 
 Fig. 218. 
 
 Morning. Mid-day. Evening. Night. Morning. 
 
 Variations of the daily temperature in health during twenty-tour hours. L , after Liebermeister ; J after 
 
 Jiirgensen. 
 
 (4) Periodical Daily Variations. — In the course of twenty-four hours there 
 are regular periodic variations in the mean temperature, and these occur at all ages. 
 As a general rule, the temperature continues to rise during the day (maximum at 5 to 
 8 p.m.), while it continues to fall during the night (minimum 2 to 6 a.m.). The mean 
 temperature occurs at the third hour after breakfast {Lichtenfels and Frohlich). 
 
 Time. 
 
 Barensprung. 
 
 J. Davy. 
 
 Hallmann. 
 
 Gierse. 
 
 Jiirgensen. 
 
 Jager. 
 
 Morning . 
 
 ■ 5 
 
 
 
 
 
 367 
 
 366 
 
 36.9 
 
 
 6 
 
 36.68 
 
 
 
 
 36.7 
 
 36-4 
 
 37-' 
 
 
 7 
 
 
 36.94* 
 
 36.63 
 
 36.98 
 
 36.7* 
 
 36-5* 
 
 37-5* 
 
 
 8 
 
 37.16* 
 
 
 36.80* 
 
 37.08* 
 
 36.8 
 
 36-7 
 
 37-4 
 
 
 9 
 
 
 36.89 
 
 
 
 36-9 
 
 36.8 
 
 37-5 
 
 
 10 
 
 37.26 
 
 
 io>£ = 37-36 
 
 37-23 
 
 37-o 
 
 37-o 
 
 37-5 
 
 
 11 
 
 . , 
 
 36.89 
 
 
 
 37-2 
 
 37-2 
 
 37-3 
 
 Mid- day. 
 
 12 
 
 36-87 
 
 
 
 
 37-3* 
 
 37-3* 
 
 37-5* 
 
 
 1 
 
 36.83 
 
 
 37.21 
 
 37-13 
 
 37-3 
 
 37-3 
 
 37-4 
 
 
 2 
 
 . . 
 
 37-05 
 
 
 37-5o* 
 
 37-4 
 
 37-4 
 
 37-5 
 
 
 3 
 
 37-15* 
 
 
 
 37-43 
 
 37-4* 
 
 37-3* 
 
 37-5 
 
 
 4 
 
 
 37-17 
 
 
 
 37-4 
 
 37-3 
 
 37-5* 
 
 
 5 
 
 37-48 
 
 37-°5* 
 
 5^=37.21 
 
 37-43 
 
 37-5 
 
 37-5 
 
 37-5 
 
 
 6 
 
 
 ey 2 = 36.83 
 
 
 37-29 
 
 37-5 
 
 37-6 
 
 37-4 
 
 
 7 
 
 37-43 
 
 7^=36.50* 
 
 37-3'* 
 
 
 37-S* 
 
 37.6* 
 
 37-3 
 
 
 8 
 
 
 
 
 . . 
 
 37-4 
 
 37-7 
 
 37-i* 
 
 
 9 
 
 37.02* 
 
 
 
 
 37-4 
 
 37-5 
 
 3 6 -9 
 
 
 10 
 
 
 
 
 37-29 
 
 37-3 
 
 37-4 
 
 36.8 
 
 
 11 
 
 36.8S 
 
 36.72 
 
 36.70 
 
 36.81 
 
 37-2 
 
 37-i 
 
 36-8 
 
 Night. . 
 
 12 
 
 . . 
 
 
 
 
 37-1 
 
 36.9 
 
 369 
 
 
 1 
 
 36-65 
 
 36-44 
 
 
 
 37-o 
 
 3 6 -9 
 
 36.9 
 
 
 2 
 
 
 
 
 
 36.9 
 
 36-7 
 
 36-8 
 
 
 3 
 
 
 
 . . 
 
 
 36.8 
 
 36-7 
 
 36-7 
 
 
 4 
 
 36-31 
 
 • • 
 
 ' ' 
 
 
 36-7 
 
 36-7 
 
 36.7 
 
 [* Indicates taking of food.] 
 
360 CONDITIONS AFFECTING THE MEAN TEMPERATURE. 
 
 The mean height of all the temperatures taken during a day in a patient is 
 called the "daily mean," and according to Jaeger, it is 37.13° in the rectum 
 in health. A daily mean of more than 37. 8° is a " fever temperature," while a 
 mean under 37. o° C. is regarded as a "collapse temperature." 
 
 According to I.ichtenfels and Frohlich, the morning temperature rises four to six hours after 
 breakfast until its first maximum, then it falls until dinner time ; and it rises again within two hours 
 to a second maximum, falls again toward evening, while supper does not appear to cause any 
 obvious increase. The daily variation of the temperature is given in Fig. 218, according to Lieber- 
 meister and Jiirgensen. According to Bonnal, the minimum occurs between 12 and 3 a.m. (in 
 winter 36.05, in summer 36.45 C), the maximum between 2 and 4 p.m. 
 
 As the variations occur when a person is starved for a day — although those that occur at the 
 periods at which food ought to have been taken are less — it is obvious that the variations are not 
 due entirely to the taking of food. 
 
 The daily variation in the frequency of the pulse often coincides with variation of the tem- 
 perature. Barensprung found that the mid-day temperature maximum slightly preceded the pulse 
 maximum (§ 70, 3, C). 
 
 If we sleep during the day, and do all our daily duties during the night, the 
 above described typical course of the temperature is inverted (Krieger). With 
 regard to the effect of activity or rest, it appears that the activity of the muscles 
 during the day tends to increase the mean temperature slightly, while at night the 
 mean temperature is less than in the case of a person at rest (Liebermeister). 
 
 The peripheral parts of the body exhibit more or less regular variations of their temperature. 
 In the palm of the hand, the progress of events is the following : After a relatively high night 
 temperature there is a rapid fall at 6 A.M., which reaches its minimum at 9 to 10 A.M. This is fol- 
 lowed by a slow rise, which reaches a high maximum after dinner ; it falls between I and 3 P.M., and 
 after two or three hours reaches a minimum. It rises from 6 to 8 P.M., and falls again toward 
 morning. A rapid fall of the temperature in a peripheral part corresponds to a rise of temperature 
 in internal parts (Romer\. 
 
 (5) Many operations upon the body affect the temperature. After hemor- 
 rhage, the temperature falls at first, but it rises again several tenths of a degree, 
 and is usually accompanied by a shiver or slight rigor ; several days thereafter it 
 falls to normal, and may even fall somewhat below it. The sudden loss of a large 
 amount of blood causes a fall of the temperature yi to 2° C. Very long-continued 
 hemorrhage (dog) causes it to fall to 31° or 29° C. (Marshall Hall). 
 
 This is, obviously, due to the diminution of the processes of oxidation in the ansemic body, and 
 to the enfeebled circulation. Similar conditions, causing diminished metabolism, effect the same 
 result. Continued stimulation of the peripheral end of the vagus, so that the heart's action is enor- 
 mously slowed, diminishes the temperature several degrees in rabbits (Landois and Ammon). 
 
 The transfusion of a considerable quantity of blood raises the temperature 
 about half an hour after the operation. This gradually passes into a febrile attack, 
 which disappears within several hours. When blood is transfused from an artery to 
 a vein of the same animal a similar result occurs (Albert and Strieker) (§ 102). 
 
 (6) Many poisons diminish the temperature, e.g., chloroform (Scheinesson), 
 and the anaesthetics, as also alcohol (§ 235), digitalis, quinin, aconitin, muscarin. 
 These appear to act, partly, by rendering the tissues less liable to undergo molecu- 
 lar transformations for the production of heat. In the case of the anaesthetics, 
 this effect, perhaps, occurs, and is due, possibly, to a semi-coagulation of the 
 nervous substance (?). They may also act partly by influencing the giving off 
 of heat (§ 214, II). Other poisons increase the temperature, for opposite reasons. 
 
 The temperature is increased by strychnin, nicotin, picrotoxin, veratrin (Hogyes), laudanin 
 (F. A. Falck). Curara (muscarin — Hogyes), laudanosin (F. A. Falck), cause an uncertain effect. 
 
 (7) Various diseases diminish the temperature, which may be due either to lessened produc- 
 tion of heat (diminution of the metabolism), or to increased expenditure of heat. Loewenhardt 
 found that in paralytics and in insane personSj several weeks before their death, the rectal tempera- 
 ture was 30° to 31° C. ; Bechterew found in dementia paralytica, before death, 27.5 C. (rectum); 
 the lowest temperature observed, and life retained, in a drunken person, was 24 C. (Reinke, 
 Nicolaysen). 
 
REGULATION OF THE TEMPERATURE. 361 
 
 The temperature is increased in fever, and the highest point reached just before death, and re- 
 corded by Wunderlich, was 44.65 C. (compare (j 220). Increase of temperature, constituting fever, 
 is treated of in \ 220. 
 
 214. REGULATION OF THE TEMPERATURE.— As the bodily 
 temperature of man and similar animals is nearly constant — notwithstanding 
 great variations in the temperature of their surroundings — it is clear that some 
 mechanism must exist in the body whereby the heat economy is constantly 
 regulated. This may be brought about in two ways: either by controlling the 
 transformation of potential energy into heat, or by affecting the amount of heat 
 given off according to the amount produced, or to the action of external agencies. 
 
 I. Regulatory Arrangements Governing the Production of Heat. — 
 Lieberrrieister estimated the amount of heat produced by a healthy man at 1.8 
 calories per minute. It is highly probable that, within the body, there exist 
 mechanisms which determine the molecular transformations, upon which the evo- 
 lution of heat depends (Hoppe-Seyler, Liebermeister). This is accomplished, 
 chiefly, in a reflex manner. The peripheral ends of cutaneous nerves (by 
 thermal stimulation), or the nerves of the intestine and the digestive glands (by 
 mechanical or chemical stimulation during digestion or inanition) may be irri- 
 tated, whereby impressions are conveyed to the heat centre, which sends out 
 impulses, through efferent fibres, to the depots of potential energy, either to 
 increase or diminish the extent of the transformations occurring in them. The 
 nerve channels herein concerned are entirely unknown. Many considerations, 
 however, go to support such an hypothesis (§377). 
 
 • Heat Centre. — So far, the investigations as to the existence of such a centre are not quite con- 
 clusive. Tschetschechin and Naunyn, Ott and Wood, assume that there is a cerebral heat centre, 
 which inhibits the combustion processes in the body by means of fibres descending through the 
 pons, medulla oblongata and spinal cord, so that destruction of this centre, or its conducting paths, 
 increases the production of heat. Aronsohn and Sachs observed that puncture of a rabbit's brain, 
 several millimetres to the side of and behind the large fontanelle, was followed by a temporary rise 
 'of the temperature. Richet noted a similar result, but he referred it to increased production of heat ; 
 the animals ate more and lost flesh. Repeated puncture of the brain finally caused emaciation, 
 diminution of temperature (26 C.) and death. 
 
 The following phenomena indicate the existence of mechanisms regulating the 
 production of heat : — 
 
 (1) The temporary application of moderate cold raises the bodily temperature, 
 while heat, similarly applied to the external surface, lowers it (§222 and 224). 
 
 (2) Cooling of the surroundings increases the amount of C0 2 excreted, by 
 increasing the production of heat [Liebermeister, Gildermeister), while the O 
 consumed is also increased simultaneously ; heating the surrounding medium di- 
 minishes the C0 2 (§ 127, 5). 
 
 D. Finkler found, from experiments upon guinea pigs, that the production of heat was more than 
 doubled when the surrounding temperature was diminished 24 C. The metabolism of the guinea 
 pig is increased in winter 23 per cent., as compared with summer ; so that the same relation obtains 
 as in the case of a diminution of the surrounding temperature of short duration. 
 
 C. Ludwig and Sanders- Ezn found that in a rabbit there was a rapid increase in the amount of 
 COj given off, when the surroundings were cooled from 38 to 6° or 7 C. ; while the excretion was 
 diminished when the surrounding temperature was raised from 4°-9° to 35°-37°, so that the thermal 
 stimulation, due to the temperature of the surrounding medium, acted upon the combustion within 
 the body. Pfluger found that a rabbit which was dipped in cold water used more O and excreted 
 more C0 2 . 
 
 If the cooling action was so great as to reduce the bodily temperature to 30°, the exchange of 
 gases diminished, and where the temperature fell to 20°, the exchange of gases was diminished one- 
 half. It is to be remembered, however, that the excretion of C0 2 does not go hand in hand with 
 the formation of C0 2 , so that the increased excretion of C0 2 in a cold bath is, perhaps, due to more 
 complete expiration, and Berthelot has proved that the formation of C0 2 is not a certain test of the 
 amount of heat produced. If mammals be placed in a warm bath, which is 2° to 3° higher than 
 their own temperature, the excretion of C0 2 and the consumption of O are increased, owing to the 
 stimulation of their metabolism (Pfluger), while the excretion of urea is also increased in animals 
 \Naunyri) and in man {Schleich) (§ 133, 5). 
 
362 REGULATION OF THE TEMPERATURE. 
 
 (3) Cold acting upon the skin causes involuntary muscular movements 
 (shivering, rigors), and also voluntary movements, both of which produce heat. 
 
 The cold excites the action of the muscles, which is connected with processes of oxidation 
 (PJluger). After poisoning with curara, which paralyzes voluntary motion, this regulation of the 
 heat falls to a minimum (Rohrig and Zuntz) [while the bodily temperature rises and falls with a 
 rise or fall in the temperature of the surrounding medium]. 
 
 (4) Variations in the temperature of the surroundings affect the appetite 
 for food ; in winter, and in cold regions, the sensation of hunger and the appetite 
 for the fats, or such substances as yield much heat when they are oxidized, are 
 increased ; in summer, and in hot climates, they are diminished. Thus the mean 
 temperature of the surroundings, to a certain extent, determines the amount of 
 the heat-producing substances to be taken in the food. In winter the amount of 
 ozone in the air is greater, and thus the oxidizing power of the inspired air is 
 increased. 
 
 II. Regulatory Mechanisms Governing the Excretion of Heat — 
 The mean amount of heat given off by the human skin in twenty-four hours, by a 
 man weighing 82 kilos., is 2092 to 2592 calories, i. e., 1.36 to 1.60 per minute. 
 
 (1) Increased temperature causes dilatation of the cutaneous vessels ; 
 the skin becomes red, congested, and soft ; it contains more fluids, so that it 
 becomes a better conductor of heat ; the epithelium is moistened, and sweat 
 appears upon the surface. Thus increased excretion of heat is provided for, while 
 the evaporation of the sweat also abstracts heat. 
 
 The amount of heat necessary to convert into vapor I grm. of water at ioo c C, is equal to that 
 required to heat 10 grms. from o° to 53.67 C. The sweat as secreted is at the temperature of the 
 body; if it were completely changed into vapor, it would require the heat necessary to raise it to the 
 boiling point, and also that necessary to convert it into vapor. 
 
 Cold causes contraction of the cutaneous vessels ; the skin becomes 
 pale, less soft, poorer in juices, and collapsed ; the epithelium becomes dry, and 
 does not permit fluids to pass through it to be evaporated, so that the excretion of 
 heat is diminished. The excretion of heat from the periphery, and the transverse 
 thermal conduction through the skin, are diminished by the contraction of the 
 vessels and muscles of the skin, and by the expulsion of the well-conducting blood 
 from the cutaneous and subcutaneous vessels. The cooling of the body is very 
 much affected, owing to the diminution of the cutaneous blood stream, just as 
 occurs when the current through a coil or worm of a distillation apparatus is greatly 
 diminished ( Winternitz). If the blood vessels dilate, the temperature of the surface 
 of the body rises, the difference of temperature between it and the surrounding 
 cooler medium is increased, and thus the excretion of heat is increased. Tomsa 
 has shown that the fibres of the skin are so arranged anatomically, that the tension 
 of the fibres produced by the erector pili muscles causes a diminution in the 
 thickness of the skin, this result being brought about at the expense of the easily 
 expelled blood. 
 
 Landois and Hauschild ligatured the arteries alone, or the arteries and veins (dog), e.g., the 
 axillary artery and vein, the crurals, the carotids and the jugular veins, and found that in a short 
 time the temperature rose several tenths of a degree. 
 
 By the systematic application of stimuli, <?. g., cold baths, and washing with cold water, the 
 muscles of the skin and its blood vessels may be caused to contract, and become so vigorous and 
 excitable that, when cold is suddenly applied to the body, or to a part of it, the excretion of heat is 
 energetically prevented, so that cold baths and washing with cold water are, to a certain extent, 
 " gymnastics of the cutaneous muscles," which, under the above circumstances, protect the body 
 from cold (Rosenthal, du Bois Reymond). 
 
 (2) Increased temperature causes increased heart beats, while 
 diminished temperature diminishes the number of contractions of the 
 heart (§ 58, II, a). The relatively warm blood is pumped by the action of the 
 heart from the internal organs of the body to the surface of the skin, where it 
 readily gives off heat. The more frequently the same volume of blood passes 
 
CLOTHING. 363 
 
 through the skin — twenty-seven heart beats being necessary for the complete 
 circuit of the blood — the greater will be the amount of heat given off and con- 
 versely. Hence, the frequency of the heart beat is in direct relation to the 
 rapidity of cooling {Walther). In very hot air (over 100° C.) the pulse rose to 
 over 160 per minute. The same is true in fever (§ 70, 3, c). Liebermeister gives 
 the following numbers with reference to the temperature in an adult : — 
 
 Pulse beats, per min 78.6 — 91.2 — 99.8 — 108.5 — 110—137.5. 
 
 Temperature in C.° 37°— 38 — 39 — 40 — 41 — 42°." 
 
 (3) Increased Temperature increases the Number of Respirations. 
 
 — Under ordinary circumstances, a much larger volume of air passes through the 
 lungs when it is warmed almost to the temperature of the body. Further, a cer- 
 tain amount of watery vapor is given off with each expiration, which must be 
 evaporated, whereby heat is abstracted. Energetic respiration aids the circula- 
 tion, so that respiration acts indirectly in the same way as (2). According to 
 other observers, the increased consumption of O favors the combustion in the 
 body (§ 127, 8), whereby the increased respiration must act in producing an 
 amount of heat greater than normal. This excess is more than compensated by 
 the cooling factors above mentioned. Forced respiration produces cooling, even 
 when the air breathed is heated to 54 C, and saturated with watery vapor. 
 {Lombard). 
 
 (4) Covering of the Body. — Animals become clothed in winter with a winter 
 fur or covering, while in summer their covering is lighter, so that the excretion of 
 heat in surroundings of different temperatures is thereby rendered more constant. 
 Many animals which live in very cold air or water (whale) are protected from too 
 rapid excretion of heat by a thick layer of fat under the skin. Man provides for 
 a similar result by adopting summer and winter clothing. 
 
 (5) The position of the body is also important ; pulling the parts of the body 
 together, approximation of the head and limbs, keep in the heat ; spreading out 
 the limbs, erection of the hairs, pluming the feathers, allow more heat to be 
 evolved. If a rabbit be kept exposed to the air with its legs extended for three 
 hours, the rectal temperature will fall from 39 C. to 37 C. Man may influence 
 his temperature by remaining in a warm or cold room — by taking hot or cold 
 drinks, hot or cold baths — remaining in air at rest or air in motion, e. g., by using 
 a fan. 
 
 Stimulation of the central end of a sensory nerve (sciatic) increases the surface temperature and 
 diminishes the internal temperature (Ostroumow, Mitropolsky). 
 
 Clothing — Warm Clothing is the Equivalent of Food. — As clothes are intended to keep in 
 heat of the body, and heat is produced by the combustion and oxidation of the food, we may say 
 the body takes in heat directly in the food, while clothing prevents it from giving off too much heat. 
 Summer clothes weigh 3 to 4 kilos,, and winter ones 6 to 7 kilos. 
 
 In connection with clothes, the following considerations are of importance : — 
 
 ( 1 ) Their capacity for conduction. — Those substances which conduct heat badly keep us warmest. 
 Hare skin, down, beaver skin, raw silk, taffeta, sheep's wool, cotton wool, flax, spun silk, are given 
 in order, from the worst to the best conductors. (2) The capacity for radiation. — Coarse materials 
 radiate more heat than smooth, but color has no effect. (3) Relation to the sun's rays.- — Dark 
 materials absorb more heat than light colored ones. (4) Their hygroscopic properties are. important, 
 whether they can absorb much moisture from the skin and gradually give it off by evaporation, or 
 the reverse. The same weight of wool takes up twice as much as linen ; hence, the latter gives it 
 off in evaporation more rapidly. Flannel next the skin is not so easily moistened, nor does it so 
 rapidly become cold by evaporation ; hence it protects against the action of cold. (5) The per- 
 meability for air is of importance, but does not stand in relation with the heat conducting capacity. 
 The following substances are arranged in order from the most to the least permeable — flannel, buck- 
 skin, linen, silk, leather, wax cloth. 
 
 215. INCOME, EXPENDITURE, AND BALANCE OF HEAT. 
 
 — As the temperature of the body is maintained within narrow limits, the amount 
 of heat taken in must balance the heat given off, i. e. , exactly the same amount of 
 potential energy must be transformed in a given time into heat, as heat is given off 
 from the body. 
 
364 INCOME, EXPENDITURE, AND BALANCE OF HEAT. 
 
 An adult produces as much heat in half an hour as will raise the temperature of 
 his body i°C. If no heat was given off, the body would become very hot in a 
 short time ; it would reach the boiling point in thirty-six hours, supposing the 
 production of heat continued uninterruptedly. 
 
 The following are the most important calculations on the subject : — 
 
 (A) According to Helmholtz, who was the first to estimate numerically the amount of heat 
 produced by a man. 
 
 (1) Heat Income. — (a) A healthy adult, weighing 82 kilos., expires in twenty- 
 
 four hours 878.4 grms. C0 2 \Scharling). The combustion of the 
 
 C therein into C0 2 produces 1,730,760 cal. 
 
 (b) But he takes in moreO than reappears in the C0 2 ; the excess is used 
 
 in oxidation processes, e. g., for the formation of H 2 0, by union 
 with H, so that 13,615 grms. H will be oxidized by the excess of 
 
 O, which gives 318,600 cal. 
 
 2,049,360 cal. 
 
 (c) About 25 per cent, of the heat must be referred to sources other than 
 
 combustion {Dulong), so that the total == 2,732,000 cal. 
 
 2,732,000 calories are actually sufficient to raise the temperature of an 
 adult weighing 80 to 90 kilos., from io to 38 or 39 C, i. c, to a 
 normal temperature. 
 
 (2) Heat expenditure. — (a) Heating the food and drink, which have a mean 
 
 temperature of 12 C. 70,157 cal = 2.6 per cent. 
 
 (b) Heating the air respired = 16,400 grms., with an initial temperature of 
 
 20 C. 70,032 cal =2.6 per cent. 
 
 ( When the temperature of the air is o°, 140,064 cal. = 5.2 per cent.) 
 
 !c) Evaporation of 656 grms. water by the lungs, 397,536 cal = 14.7 per cent. 
 d) The remainder given off by radiation and evaporation of water by the 
 
 skin, (77. 5 per cent, to) =80.1 per cent. 
 
 (B) According to Dulong. — (1) Heat income. — Dulong, and after him Boussingault, Liebig, 
 and Dumas, sought to estimate the amount of heat from the C and H contained in the food. As 
 we know that the combustion of 1 grm. C = 8040 heat units, and 1 grm. H = 34,460 heat units, 
 it would be easy to determine the amount of heat were the C simply converted into C0 2 and the 
 H into H 2 0. But Dulong omitted the H in the carbohydrates (<?. g., grape sugar = C e H 12 6 ) as 
 producing heat, because the H is already combined with O, or at least is the proportion in which it 
 exists in water. This assumption is hypothetical, for the atoms of C in a carbohydrate may be so 
 firmly united to the other atoms, that before oxidation can take place their relations must be altered, 
 so that potential energy is used up, i. e., heat must be rendered latent; so that these considerations 
 rendered the following example of Dulong's method given by Vierordt very problematical. 
 
 An adult eats in twenty- four hours, 120 grms. proteids, 90 grms. fat and 340 grms, starch (carbo- 
 hydrates). These contain :— 
 
 Grms. C. H. 
 
 Proteids 120 contain 64.18 and 8.60 
 
 Fat 90 " 70.20 " 10.26 
 
 Starch 330 " 146.82 " . . 
 
 281.20 and 18.86 
 The urine and fseces contain still unconsumed . . . 29 8 " 6.3 
 
 Remainder to be burned 251.4 and 12.56 
 
 As 1 grm. C = 8040 heat units and I grm. H = 34,460 heat units, we have the following calcu- 
 lation : — 
 
 251.4 X 8 >°4° = 2,031,312 (from combustion of C). 
 12.56 X 34.46o = 432.818 ( " " H). 
 
 2,464,130 heat units. 
 (2) Heat expenditure : — Per cent, of 
 
 Heat units. the excreta. 
 
 1. 1900 grms. are excreted daily by the urine and fseces, and 
 
 they are 25 warmer than the food 47,500 1.8 
 
 2. 13,000 grms. air are heated (from 12° to 27 C.) (heat 
 
 capacity of the air = 0.26) 84.500 3.5 
 
 3. 330 grms. water are evaporated by the respiration (i grm. 
 
 = 582 heat units) 192,060 7.2 
 
 4. 660 grms. water are evaporated from the skin 384,1 'o 14.5 
 
 Total 708,180 
 
 Remainder radiated and conducted from the skin 1,791,810 72 
 
 Total amount of heat units given off 2,500,000 100 
 
RELATION OF HEAT PRODUCTION TO WORK. 365 
 
 (C) Heat income. — Frankland burned the food directly in a calorimeter, and found that I grm. 
 of the following substances yielded — 
 
 Albumin 499 8 heat units 
 
 Grape sugar 3277 " 
 
 Ox fat 9069 " 
 
 The albumin, however, is only oxidized to the stage of urea, hence the heat units of urea must be 
 deducted from 4998, which gives 4263 heat units obtainable from I grm. albumin. When we know 
 the number of grammes consumed, a simple multiplication gives the number of heat units. 
 
 The heat units will vary, of course, with the nature of the food. J. Ranke gives the following : — 
 
 With animal diet 2,779,524 heat units. 
 
 " food free from N 2,059,506 " 
 
 " mixed diet 2,200,000 " 
 
 " during hunger 2,012,816 " 
 
 216. VARIATIONS IN HEAT PRODUCTION.— According to Helmholtz, an adult 
 weighing 82 kilos, produces 2,732,000 calories in twenty-four hours. 
 
 (1) Influence of the Body Weight. — Accepting the above number, Immermann has given the 
 following formula for the heat production in living tissues : — 
 
 w : W = y/J*\ j/P 2 
 
 3 
 
 (where W = 2,732,000; P = 82 kilos. [W: j// 2 = 144,75] > P = D0( fy weight of the person 
 to be investigated, and w represents the heat production which is required). 
 
 8 
 
 It is highly desirable that W : y'/ 2 (= m) was ascertained as a mean from a large number of 
 observations, that the heat production for any body weight p would be 
 
 3 — 
 w = m t/P 2 . 
 
 (2) Age and Sex. — The heat production is less in infancy and in old age, and it is less in pro- 
 portion in the female than in the male. 
 
 (3) Daily Variation. — The heat production shows variations in twenty-four hours correspond- 
 ing with the temperature of the body (\ 213, 4). 
 
 (4) The heat production is greater in the waking condition, during physical and mental exer- 
 tion, and during digestion, than in the opposite conditions. 
 
 217. RELATION OF HEAT PRODUCTION TO WORK.— The 
 
 potential energy supplied to the body may be transformed into heat and kinetic 
 energy (see Introduction). In the passive condition, almost all the potential 
 energy is changed into heat ; the workman, however, transforms potential energy 
 into work — mechanical work — in addition to heat. These two may be com- 
 pared by using an equivalent measurement, thus 1 heat unit (energy required to 
 raise 1 gramme of water i° C.) = 425.5 gramme metres. 
 
 Relation of Heat to Work. — The following example may serve to illustrate the relation between 
 heat production and the production of work : Suppose a small steam engine to be placed within a 
 capacious calorimeter, and a certain quantity of coal to be burned, then as long as the engine does 
 not perform any mechanical work, heat alone is produced by the burning of the coal. Let this 
 amount of heat be estimated, and a second experiment made by burning the same amount of coal, 
 but allow the engine to do a certain amount of work — say, raise a weight — by a suitable arrange- 
 ment. This work must, of course, be accomplished by the potential energy of the heating material. 
 At the end of this experiment, the temperature of the water will be much less than in the first ex- 
 periment, i. e., fewer heat units have been transferred to the calorimeter when the engine was heated 
 than when it did no work. 
 
 Comparative experiments of this nature have shown that in the second experiment the useful 
 work is very nearly proportional to the decrease of the heat {Him). In good steam engines only 
 ■X, and in the very best }4, of the potential energy is changed into mechanical energy, while }$ to 
 % passes into heat. 
 
 Compare this with what happens within the body : A man in a passive con- 
 dition forms from the potential energy of the food between 2^ and 2^ million 
 calories. The work done by a workman is reckoned at 300,000 kilogramme 
 metres (§ 300). 
 
 If the organism were entirely similar to a machine, a smaller amount of heat, 
 corresponding to the work done, would be formed in the body. As a matter of 
 fact, the organism produces less heat from the same amount of potential energy 
 
366 
 
 ACCOMMODATION FOR VARYING TEMPERATURES. 
 
 when mechanical work is done. There is one point of difference between a work- 
 man and a working machine. The workman consumes much more potential 
 energy in the same time than a passive person ; much more transformed in his 
 body, and hence the increased consumption is not only covered, but even over- 
 compensated. Hence, the workman is warmer than the passive person, owing to 
 the increased muscular activity (§ 210, 1, b). Take the following example : Him 
 (1858) remained passive, and absorbed 30 grm. O per hour in a calorimeter, and 
 produced 155 calories. When in the calorimeter he did work equal to 27,450 
 kilogramme metres, which was transferred beyond it; he absorbed 132 grm. O, 
 and produced only 251 calories. 
 
 In estimating the work done, we must include only the heat equivalent of the work transferred 
 beyond the body ; lifting weights, pushing anything, throwing a weight, and lifting the body, are 
 examples. In ordinary walking there is no loss of heat (apart from overcoming the resistance of 
 the air); when descending from a height there may be increased warmth of the body. 
 
 The organism is" superior to a machine in as far as it can, from the same amount 
 of potential energy, produce more work in proportion to heat. While the very 
 best steam engine gives \ of the potential energy in the form of work, and -J as 
 heat, the body produces \ as work and $ as heat. Chemical energy can never do 
 work alone, in a living or dead motor, without heat being formed at the same 
 time. 
 
 218. ACCOMMODATION FOR VARYING TEMPERATURES. 
 
 — All substances which possess high conductivity for heat, when brought into con- 
 tact with the skin, appear to be very much colder or hotter than bad conductors 
 of heat. The reason of this is that these bodies abstract far more heat, or con- 
 duct more heat than other bodies. Thus the water of a cool bath, being a better 
 conductor of heat, is always thought to be colder than air at the same tempera- 
 ture. In our climate it appears to us that — 
 
 Air, at 18 C. is moderately warm; 
 " at 25°-28° C, hot; 
 " above 28 , very hot. 
 
 Water, at 18° C. is cold; 
 " from l8°-29° C, cool; 
 " » 29°-3S° C, warm ; 
 
 " " 37-5° an d above, hot. 
 
 Warm Media. — As long as the temperature of the body is higher than that 
 of the surrounding medium, heat is given off, and that the more rapidly the 
 better the conducting power of the surrounding medium. As soon as the tem- 
 perature of the surrounding medium rises higher than the temperature of the 
 body, the latter absorbs heat, and it does so the more rapidly the better the con- 
 ducting power of the medium. Hence, hot water appears to be warmer than air 
 at the same temperature. A person may remain eight minutes in a bath at 45.5° 
 C. (dangerous to life !) ; the hands may be plunged into water at 50.5° C, but 
 not at 51.65° C, while at 6o° violent pain is produced. 
 
 A person may remain for eight minutes in hot air at 127 C, and a tempera- 
 ture of 132° C. has been borne for ten minutes (Tillett, 1763). The body tem- 
 perature rises only to 38. 6° or 38. 9 (Fordyce, Blagden, 1774 s ). This depends 
 upon the air being a bad conductor, and thus it gives less heat to the body than 
 water would do. Further, and what is more important, the skin becomes covered 
 with sweat, which evaporates and abstracts heat, while the lungs also give off more 
 watery vapor. The enormously increased heart beats — over 160 — and the dilated 
 blood vessels, enable the skin to obtain an ample supply of blood for the formation 
 and evaporation of sweat. In proportion as the secretion of sweat diminishes, 
 the body becomes unable to endure a hot atmosphere ; hence it is that in air con- 
 taining much watery vapor a person cannot endure nearly so high a temperature as 
 in dry air, so that heat must accumulate in the body. In a Turkish vapor bath 
 of 53 to 6o° C, the rectal temperature rises to 40. 7 or 41. 6° C. (Barthels, 
 Jiirgensen Krishaber). A person may work continuously in air at 31° C. which 
 is almost saturated with moisture (Stapff). 
 
FEVER AND ITS PHENOMENA. 367 
 
 If a person be placed in water at the temperature of the body, the normal 
 temperature rises i° C. in one hour, and in i^ hours about 2° C. (Liebermeister). 
 A gradual increase of the temperature from 38. 6° to 40.2° C. causes the axillary 
 temperature to rise to 39. o° within fifteen minutes. 
 
 Rabbits placed in a warm box at 36 C. acquire a constant temperature of 42° C, and lose 
 weight; but if the temperature of the box be raised to 40 , death occurs, the body temperature 
 rising to 45° C. (_/. Rosenthal). 
 
 219. STORAGE OF HEAT IN THE BODY.— As the uniform tem- 
 perature of the body, under normal circumstances, is due to the reciprocal rela- 
 tion between the amount of heat produced and the amount given off, it is clear 
 that heat must be stored up in the body when the evolution of heat is diminished. 
 The skin is the chief organ regulating the evolution of heat ; when it and its 
 blood vessels contract the heat evolved is diminished, when they dilate it is in- 
 creased. Heat may be stored up when — 
 
 (a) The skin is extensively stimulated, whereby the cutaneous vessels are temporarily contracted 
 (Rohrig). (b) Any other circumstances preventing heat from being given off by the skin [Win- 
 ternitz). (c) When the vasomotor centre is excited, causing all the blood vessels of the body — 
 those of the skin included — to contract. This seems to be the cause of the rise of temperature 
 after the transfusion of blood (Landois), and the rise of temperature after the sudden removal of 
 water from the body seems to admit of a similar explanation ; as the inspissated blood occupies less 
 space, and the contracted vessels of the skin admit less blood, (d ) When the circulation in the 
 cutaneous vessels of a large area is mechanically slowed, or when the smaller vessels are plugged 
 by the injection of some sticky substance, or by the transfusion of foreign blood, the temperature 
 rises [\ 102). Landois found that ligature of both carotids, and the axillary and crural arteries, 
 caused a rise of i° C. within two hours. 
 
 It is also obvious than when a normal amount of heat is given off, an increased 
 production of heat must raise the temperature. The rise of the temperature after 
 muscular or mental exertion, and during digestion, seems to be caused in this 
 way. The rise which occurs several hours after a cold bath is probably due to the 
 reflex excitement of the skin causing an increased production \jurgenseri). 
 
 When the temperature of the body, as a whole, is raised 6° C., death takes 
 place, as in sunstroke. It seems as if there was a molecular decomposition of the 
 tissues at this temperature ; while, if a slightly lower temperature be kept up con- 
 tinuously, fatty degeneration of many tissues occurs (Litteri). If animals which 
 have been exposed artificially to a temperature of over 42 to 44 C. be transferred 
 to a cooler atmosphere, their temperature becomes subnormal (36° C.) and may 
 remain so for several days. 
 
 220. FEVER. — Cause. — Fever consists in a greatly increased tissue metabolism (especially in 
 the muscles — Finkler, Zunts), with simultaneous increase of the temperature. Of course, the 
 mechanism regulating the balance of formation and expenditure of heat is disturbed. During fever 
 the body is greatly incapacitated for performing mechanical work. It is evident, therefore, that the 
 large amount of potential energy transformed is almost all converted into heat, so that the non- 
 transformation of the energy into mechanical work is another important factor. 
 
 We may take intermittent fever or ague as a type of fever, in which violent attacks of fever of 
 several hours' duration alternate with periods free from fever. This enables us to analyze the 
 symptoms. The symptoms of fever are : — 
 
 (1) The increased temperature of the body (38 to 39 C, slight; from 39 to 41 C. and 
 upward, severe). The high temperature occurs not only in cases where the skin is red, and has a 
 hot, burning feeling (calor mordax), but even during the rigor or the shivering stage, the tempera- 
 ture is raised [Ant. de Haen, 1760). The congested, red skin is a good conductor of heat, while 
 the pale, bloodless skin conducts badly; hence, the former feels hot to the touch (v. Barensprung 
 — compare \ 212). 
 
 The following table in °C and °F indicates generally the degree of fever : — 
 
 35 C. = 95 F Collapse. 
 
 36 
 
 = 
 
 96.8 
 
 3°. s 
 
 = 
 
 97-7 
 
 37 
 
 = 
 
 98.6 
 
 37-5 
 
 = 
 
 99-5 
 
 38 
 
 = 
 
 100.4 
 
 38.S 
 
 = 
 
 101.3 
 
 39 C. = 102.2° F. 
 
 Low. 
 
 39-5 
 
 = 103.1 
 
 Subnormal. 
 
 40 
 
 = 104 
 
 Normal. 
 
 40.5 
 
 = 104.9 
 
 
 41 
 
 = 105.8 
 
 Sub-febrile. 
 
 
 
 Moderate fever. 
 
 High fever. 
 
 Hyperpyretic. 
 
 Mnlayson.~\ 
 
368 FEVER AND ITS PHENOMENA. 
 
 (2) The increased production of heat (assumed by Lavoisier and Crawford) is proved by 
 calorimetric observations. This is, in small part, due to the increased activity of the circulation 
 being changed into heat (<j 206, 2, a), but for the most part it is due to increased combustion within 
 the body. 
 
 (3) The increased metabolism gives rise to the " consuming " or " wasting " character of fever, 
 which was known to Hippocrates and Galen, and, in 1852, v. Barensprung asserted that "all the 
 so-called febrile symptoms show that the metabolism is increased." The increase of the metabolism 
 is shown in the increased excretion of C0 2 = 70 to 80 per cent. (Leyden and Frankel), while 
 more O is consumed, although the respiratory quotient remains the same (Zuntz and Lilienfeld). 
 According to Dr. Finkler, the CO a excreted shows greater variations than the O consumed. The 
 excretion of urea is increased \ to \ . In dogs suffering from septic fever, Naunyn observed that 
 the urea began to increase before the temperature rose, "pre-febrile rise." Part of the urea, 
 however, is sometimes retained during the fever, and appears after the fever is over, " epi-critical 
 excretion of urea" {Naunyn). The uric acid is also increased; the urine pigment (g 19), 
 derived from the haemoglobin, may be increased twenty times, while the excretion of potash 
 may be sevenfold. 
 
 It is important to observe that the oxidation or combustion processes within the body of the fever 
 patient are greatly increased when he is placed in a warmer atmosphere. The oxidation processes 
 in fever, however, are also increased under the influence of cooler surroundings (| 214, I, 2), but 
 the increase of the oxidation in a warm medium is very much greater than in the cold (£>. Finkler). 
 The amount of C0 2 in the blood is diminished, but not at once after the onset even of a very severe 
 fever [Geppert). 
 
 (4) The diminished excretion of heat varies in different stages of a fever. We distinguish 
 several stages in a fever — (a) The cold stage, when the loss of heat is greatly diminished, owing 
 to the pale, bloodless skin, but at the same time the heat production is increased i l / 2 to 2 l / z times. 
 The sudden and considerable rise of the temperature during this stage shows that the diminished 
 excretion of heat is not the only cause of the rise of the temperature, (b) During the hot stage 
 the heat given off from the congested, red skin is greatly increased, but at the same time more heat 
 is produced. Liebermeister assumes that a rise of I, 2, 3, 4 C. corresponds to an increased pro- 
 duction of heat of 6, 12, 18, 24 per cent, (c) In the sweating stage the excretion of heat through 
 the red, moist skin and evaporation are greatest, more than two to three times the normal (Leyden). 
 The heat production is either increased, normal, or subnormal, so that under these conditions the 
 temperature may also be subnormal (36 C). 
 
 (5) The heat-regulating mechanism is injured. A warm temperature of the surroundings 
 raises the temperature of the fever patient more than it does that of a non-febrile person. The 
 depression of the heat production, which enables normal animals to maintain their normal tempera- 
 ture in a warm medium (g 214), is much less in fever (£>. Finkler). 
 
 The accessory phenomena of fever are very important : Increase in the intensity and number 
 of the heart beats ((j 214, II, 2) and respirations (in adults 40, and children 60 per min.),both being 
 compensatory phenomena of the increased temperature; further, diminished digestive activity (J 186, 
 D) and intestinal movements ; disturbances of the cerebral activities ; of secretion ; of muscular 
 activity; slower excretion, e.g., of potassium iodide through the urine (Bachrach, Scholze). In 
 severe fever, molecular degenerations of the tissues are very common. 
 
 For the condition of the blood corpuscles in fever, see J 10; the vascular tension, \ 69; the 
 saliva, \ 146. 
 
 Quinine, the most important febrifuge, causes a decrease of the temperature by limiting the 
 production of heat (Lewizky, Binz, Naunyn, Quincke, Amlz) (\ 213, 6). Toxic doses of the 
 metallic salts act in the same way, while there is at the same time diminished formation of C0 2 
 (Luchsinger). 
 
 [Antipyretics or Febrifuges. — All methods which diminish abnormal temperature belong to 
 this group. As the constant temperature of the body depends on (1 ) the amount of heat production, 
 and (2) the loss of heat, we may lower the temperature either in the one way or the other. When 
 cold water is applied to the body, it abstracts heat, i. e„ it affects the results of fever, so that Lieber- 
 meister calls such methods antithermic. But those remedies which diminish the actual heat 
 production are true antipyretic. In practice, however, both methods are usually employed, and 
 spoken of collectively as antipyretics.] 
 
 [Among the methods which are used to abstract heat from the body are the application of colder 
 fluids, such as the cold bath, affusion, douche, spray, ice, or cold mixtures, etc. A person suffering 
 from high fever requires to be repeatedly placed in a cold bath, to produce any permanent reduc- 
 tion of the temperature. Some remedies act by favoring the radiation of heat, by dilating the 
 cutaneous vessels (alcohol), while others excite the sweat glands — i. e., are sudorifics — so that the 
 water, by its evaporation, removes some heat. Among the drugs which influence tissue changes 
 and oxidation — and thereby lessen heat production — are quinine, salicylic acid, some of the salicy- 
 lates, digitalis and veratrin. Blood letting was formerly used to diminish abnormal temperature. 
 Among the newer antipyretic remedies are hydrochlorate of kairin and antipyrin, both of which 
 belong to the aromatic group (derivatives of benzol), which includes, also, many of our best 
 antiseptics.] 
 
INCREASE OF TEMPERATURE POST-MORTEM. 369 
 
 221. ARTIFICIAL INCREASE OF THE BODILY TEMPERA- 
 TURE. — If mammals are kept constantly in air at 40° C, the excretion of heat 
 from the body ceases, so that the heat produced is stored up. At first, the tem- 
 perature falls somewhat for a very short time (Obernier), but soon a decided 
 increase occurs. The respirations and pulse are increased, while the latter becomes 
 irregular and weaker. The O absorbed and C0 2 given off are diminished after 
 six to eight hours (Zitten), and death occurs after great fatigue, feebleness, spasms, 
 secretion of saliva and loss of consciousness, when the bodily temperature has 
 been increased 4 , or, at most, 6° C. Death does not take place, owing to rigidity 
 of the muscles ; for the coagulation of the myosin of mammals' muscles occurs at 
 49 to 50 C. ; in birds, at 53 C, and in frogs, at 40 C. If mammals are 
 suddenly placed in air at ioo° C, death occurs (in 15 to 20 min.) very rapidly, 
 and with the same phenomena, while the bodily temperature rises 4° to 5° C. In 
 rabbits, the body weight diminishes 1 grm. per min. Birds bear a high tempera- 
 ture somewhat longer ; they die when their blood reaches 48° to 50° C. 
 
 Even man may remain for some time in air at ioo-no-132 C., but in ten to 
 fifteen minutes there is danger to life. The skin is burning to the touch, and red; 
 a copious secretion Qf sweat bursts forth, and the cutaneous veins are fuller and 
 redder {Crawford). The pulse and respirations are greatly accelerated. Violent 
 headache, vertigo, feebleness, stupefaction, indicate great danger to life. The 
 rectal temperature is only i° to 2° C. higher. The high temperature of fever may 
 even be dangerous to human life. If the temperature remains for any length of 
 time at 42. 5 C, death is almost certain to occur. Coagulation of the blood in the 
 arteries is said to occur at 42.6° C. ( Weikarl). If the artificial heating does not 
 produce death, fatty infiltration and degeneration of the liver, heart, kidneys and 
 muscles begin, after thirty-six to forty-eight hours (Littcn). 
 
 Cold-blooded Animals, if placed in hot air or warm water, soon have their temperature raised 
 6° to lo° C. The highest temperature compatible with life in a frog must be below 40 C, as the 
 frog's heart and muscles begin to coagulate at this temperature. Death is preceded by a stage 
 resembling death, during which life may be saved. 
 
 Most of the juicy plants die in half an hour in air at 52 C, or in water at 46 C. [Sachs). 
 Dried seeds of corn may still germinate after long . exposure to air at 120 C. Lowly-organized 
 plants, such as algae, may live in water at 6o° C. [Uoppe-Seyler). Several bacteria withstand a 
 boiling temperature ( Tyndall, Chamber land). 
 
 222. EMPLOYMENT OF HEAT.— Action of Heat.— The short, but not intense, action 
 Qf heat on the surface causes, in the first place, a transient slight decrease of the bodily temperature, 
 partly because it retards reflexly the production of heat {Kernig), and partly because, owing to the 
 dilatation of the cutaneous vessels and the stretching of the skin, more heat is given off (Senator). 
 A warm bath above the temperature of the blood at once increases the bodily temperature. 
 
 Therapeutic Uses. — The application of heat to the entire body is used where the bodily tem- 
 perature has fallen— or is likely to fall — very low, as in the algid stage of cholera, and in infants 
 born prematurely. The general application of heat is obtained by the use of warm baths, packing, 
 vapor baths, and the copious use of hot drinks. The local application of heat is obtained by the use 
 of warm wrappings, partial baths, plunging the parts in warm earth or sand, or placing wounded 
 parts in chambers filled with heated air. After removal of the heating agent, care must be taken to 
 prevent the great escape of heat due to the dilatation of the blood vessels. 
 
 223. INCREASE OF TEMPERATURE POST-MORTEM.— Phenomena.— Heiden- 
 
 hain found that in a dead dog, before the body cooled, there was a constant temporary rise of the 
 temperature, which slightly exceeded the normal. The same observation had been occasionally 
 made on human bodies immediately after their death, especially when death was preceded by mus- 
 cular spasms [also in yellow fever.] Thus, Wunderlich measured the temperature fifty-seven min- 
 utes after death in a case of tetanus, and found it to be 45.375° C. 
 
 Causes. — (1) A temporary increased production of heat after death, due, chiefly, to the change 
 of the semi-solid myosin of the muscles into a solid form (rigor mortis). As the muscle coagulates, 
 heat is produced {y. Wather, Fick). All conditions which cause rapid and intense coagulation of 
 the muscles — e.g., spasms — favor a post-mortem rise of temperature (see \ 295) ; a rapid coagulation 
 of the blood has a similar result (§28, 5). 
 
 (2) Immediately after death, a series of chemical processes occur within the body, whereby heat 
 is produced. Valentin placed dead rabbits in a chamber, so that no heat could be given off from 
 the body, and he found that the internal temperature of the animal's body was increased. The 
 24 
 
370 ARTIFICIAL LOWERING OF THE TEMPERATURE. 
 
 processes which cause a rise of temperature post-mortem are more active during the first than the 
 second hour ; and the higher the temperature at the moment of death, the greater is the amount of 
 heat evolved after death (Quincke and Brieger). 
 
 (3) Another cause is the diminished excretion of heat post-mortem. After the circulation is 
 abolished, within a few minutes little heat is given off from the surface of the body, as rapid excre- 
 tion implies that the cutaneous vessels must be continually filled with warm blood. 
 
 224. ACTION OF COLD ON THE BODY.— Phenomena.— A short, 
 temporary, slight cooling of the skin (removing one's clothes in a cool room, a 
 cool bath for a short time, or a cool douche) causes either no change or a slight 
 rise in the bodily temperature (Liebermeister). The slight rise, when it occurs, is 
 due to the stimulation of the skin causing reflexly a more rapid molecular trans- 
 formation, and therefore a greater production of heat (Liebermeister), while the 
 amount of heat given off is diminished, owing to contraction of the small cuta- 
 neous vessels and the skin itself {Jurgensen, Senator). The continuous and 
 intense application of cold causes a decrease of the temperature (Currie), chiefly 
 by conduction, notwithstanding that at the same time there is a greater produc- 
 tion of heat. After a cold bath the temperature may be 34°, 32 , and even 30 C. 
 
 As an after-effect of the great abstraction of heat, the # temperature of the 
 body after a time_ remains lower than it was before {"primary after-effect" — 
 Liebermeister) ; thus after an hour it was — 0.22 C. in the rectum. There is a 
 "secondary after-effect" which occurs after the first after-effect is over, when the 
 temperature rises (Jiirgenseri). This effect begins five to eight hours after a cold 
 bath, and is equal to -j- 0.2 C. in the rectum. Hoppe-Seyler found that some 
 time after the application of heat there was a corresponding lowering of the tem- 
 perature. 
 
 Taking Cold. — If a rabbit be taken from a surrounding temperature of 35 C, and suddenly 
 cooled, it shivers, and there may be temporary diarrhoea. After two clays the temperature rises 1.5 
 C, and albuminuria occurs. There are microscopic traces of interstitial inflammation in the kidneys, 
 liver, lungs, heart and nerve sheaths, the dilated arteries of the liver and lung contain thrombi, and 
 in the neighborhood of the veins are accumulations of leucocytes. In pregnant animals the foetus 
 shows the same conditions (Lassar). Perhaps the greatly cooled blood acts as an irritant, causing 
 inflammation (Rosenthal). 
 
 Action of Frost. — The continued application of a high degree of cold causes at first contrac- 
 tion of the blood vessels of the skin and its muscles, so that it becomes pale. If continued paraly- 
 sis of the cutaneous vessels occurs, the skin becomes red, owing to congestion of its vessels. As the 
 passage of fluids through the capillaries is rendered more difficult by the cold, the blood stagnates, 
 and the skin assumes a livid appearance, as the O is almost completely used up. Thus the peri- 
 pheral circulation is slowed. If the action of the cold be still more intense, the peripheral circula- 
 tion stops completely, especially in the thinnest and most exposed organs — ears, nose, toes and 
 fingers. The sensory nerves are paralyzed, so that there is numbness and loss of sensibility, and 
 the parts may even be frozen through and through. As the slowing of the circulation in the 
 superficial vessels gradually affects other areas of the circulation, the pulmonary circulation is 
 enfeebled, and diminished oxidation of the blood occurs, notwithstanding the greater amount of O 
 in the cold air, so that the nerve centres are affected. Hence arise great dislike to making move- 
 ments or any muscular effort, a painful sensation of fatigue, a peculiar and almost irresistible desire 
 to sleep, cerebral inactivity, blunting of the sense organs, and lastly, coma. The blood freezes at 
 — 3.9° C, while the juices of the superficial parts freeze sooner. Too rapid movements of the 
 frost-bitten parts ought to be avoided. Rubbing with snow, and the very gradual application of 
 heat, produce the best results. Partial death of a part is not unfrequently produced by the pro- 
 longed action of cold. 
 
 225. ARTIFICIAL LOWERING OF THE TEMPERATURE. 
 — Phenomena. — The artificial cooling of warm-blooded animals, by placing 
 them in cold air or in a freezing mixture, gives rise to a series of characteristic 
 phenomena (A. Walther). If the animals (rabbits) are cooled so that the tem- 
 perature (rectum) falls to 18 , they suffer great depression, without, however, the 
 voluntary or reflex movements being abolished. The pulse falls from 100 or 150 
 to 20 beats per minute, and the blood pressure falls to several millimetres of Hg. 
 The respirations are few and shallow. Suffocation does not cause spasms (Hor- 
 vath), the secretion of urine stops, and the liver is congested. The animal may 
 
HYBERNATION AND USE OF COLD. 371 
 
 remain for twelve hours in this condition, and when the muscles and nerves show 
 signs of paralysis, coagulation of the blood occurs after numerous blood cor- 
 puscles have been destroyed. The retina becomes pale, and death occurs with 
 spasms and the signs of asphyxia. If the bodily temperature be reduced to 1 7 
 and under, the voluntary movements cease before the reflex acts (Richet and Ron- 
 deau). An animal cooled to 18 C, and left to itself, at the same temperature of 
 the surroundings, does not recover of itself, but if artificial respiration be 
 employed, the temperature rises io° C. If this be combined with the application 
 of external warmth, the animals may recover completely, even when they have 
 been apparently dead for forty minutes. Walther cooled adult animals to 9 C, 
 and recovered them by artificial respiration and external warmth ; while Horvath 
 cooled young animals to 5 C. Mammals which are born blind, and birds which 
 come out of the egg devoid of feathers, cool more rapidly than others. Mor- 
 phia, and more so, alcohol, accelerate the cooling of mammals, at the same 
 time the exchange of gases falls considerably {Rumpf) ; hence, drunken men are 
 more liable to die when exposed to cold. 
 
 Artificial Cold-blooded Condition. — CL, Bernard made the important 
 observation, that the muscles of animals that had been cooled remained irritable 
 for a long time, both to direct stimuli and to stimuli applied to their nerves ; 
 and the same is the case when the animals are asphyxiated for want of O. An 
 "artificial cold-blooded condition," i. e., a condition in which warm-blooded 
 animals have a lower temperature, and retain muscular and nervous excitability 
 (67. Bernard), may also be caused in warm-blooded animals, by dividing the cer- 
 vical spinal cord and keeping up artificial respiration ; further, by moistening the 
 peritoneum with a cool solution of common salt ( Wegner). 
 
 Hybernation presents a series of similar phenomena. Valentin found that hybernating animals 
 become half awake when their bodily temperature is 28° C. ; at 18° C. they are in a somnolent 
 condition, at 6° they are in a gentle sleep, and at 1.6° C. in a deep sleep. The heart beats and the 
 blood pressure fall, the former to 8 to 10 per minute. The respiratory, urinary and intestinal move- 
 ments cease completely, and the cardio-pneumatic movement alone sustains the slight exchange of 
 gases in the lungs (§ 59). They cannot endure cooling to o° C, and awake before the tempera- 
 ture falls so low. Hybernating animals may be cooled to a greater degree than other mammals ; 
 they give off heat rapidly, and they become warm again rapidly, and even spontaneously. New- 
 born mammals resemble hybernating animals more closely in this respect than do adults. 
 
 Cold-blooded Animals may be cooled to 0°. Even when the blood has been frozen and ice 
 formed in the lymph of the peritoneal cavity, frogs may recover. In this condition they appear to 
 be dead, but when placed in a warm medium they soon recover. A frog's muscle so cooled will 
 contract again (Kukne). The germs and ova of lower animals, tr. g., insects' eggs, survive con- 
 tinued frost; and if the cold be moderate, it merely retards development. Bacteria, e.g., Bacillus 
 anthracis, survive a temperature of — 130° C. (Pictet and Young); yeast, even — ioo° C. (Frisch). 
 
 Varnishing the Skin causes a series of similar phenomena. The varnished skin gives off a 
 large amount of heat by radiation [Krieger), and sometimes the cutaneous vessels are greatly dilated 
 (Laschkewitsch). Hence the animals cool rapidly and die, although the consumption of O is not 
 diminished. If cooling be prevented ( Valentin, Schiff, Brunton) by warming them and keeping 
 them in warm wool, the animals live for a longer time. The blood post-mortem does not contain 
 any poisonous substances, nor even are any materials retained in the blood which can cause death, 
 for if the blood be injected into other animals, these remain healthy. Varnishing the human skin 
 does not seem to be dangerous (Senator). 
 
 226. EMPLOYMENT OF COLD.— Cold may be applied to the whole or part of the sur- 
 face of the body in the following conditions : — 
 
 (a) By placing the body for a time in. a cold bath, to abstract as much heat as possible, when the 
 bodily temperature in fever rises so high as to be dangerous to life. This result is best accomplished 
 and lasts longest when the bath is gradually cooled from a moderate temperature. If the body be 
 placed at once in cold water, the cutaneous vessels contract, the skin becomes bloodless, and thus 
 obstacles are placed in the way of the excretion of heat. A bath gradually cooled in this way is 
 borne longer (v. Ziemssen). The addition of stimulating substances, e. g., salts, which cause dila- 
 tation of the cutaneous vessels, facilitates the secretion of heat ; even salt water conducts heat better. 
 If alcohol be given internally at the same time, it lowers the temperature. 
 
 (6) Cold may be applied locally by means of ice in a bag, which causes contraction of the 
 cutaneous vessels and contraction of the tissues (as in inflammation), while at the same time heat 
 is abstracted locally. 
 
372 HISTORICAL AND COMPARATIVE. 
 
 (r) Heat may be abstracted locally by the rapid evaporation of volatile substances (ether, car- 
 bon disulphide), which causes numbness of the sensory nerves. The introduction of media of low 
 temperature into the body, respiring cool air, taking cold drinks, and the injection of cold fluids 
 into the intestine act locally, and also produce a more general action. In applying cold it is im- 
 portant to notice that the initial contraction of the vessels and the contraction of the tissues are 
 followed by a greater dilatation and turgescence, i. e., by a healthy reaction. 
 
 227. HEAT OF INFLAMED PARTS. — "Calor," or heat, is reckoned one of the funda- 
 mental phenomena of inflammation, in addition to rubor (redness), tumor (swelling), and dolor 
 (pain). But the apparent increase in the heat of the inflamed parts is not above the temperature of 
 the blood. Simon, in i860, asserted that the arterial blood flowing to an inflamed part was cooler 
 than the part itself; but v. Barensprung denies this, as J. Hunter did, and so does Jacobson, Bern- 
 hardt, and Laudien. The outer parts of the skin in an inflamed part are warmer than usual, owing 
 to the dilatation of the vessels (rubor) and the consequent acceleration of the blood stream in the 
 inflamed part, and owing to the Swelling (tumor) from the presence of good heat-conducting fluids ; 
 but the heat is not greater than the heat of the blood. It is not proved that an increased amount 
 of heat is produced owing to increased molecular decompositions within an inflamed part. 
 
 228. HISTORICAL AND COMPARATIVE. — According to Aristotle, the heart prepares 
 the heat within itself, and sends it along with the blood to all parts of the body. This doctrine 
 prevailed in the time of Hippocrates and Galen, and occurs even in Cartesius and Bartholinus 
 (1667, "flammula cordis"). The iatro "mechanical school [Boerhaave, van Swieteri) ascribed the 
 heat to the friction of the blood on the walls of the vessels. The iatro-chemical school, on the 
 other hand, sought the source of heat in the fermentations that arose from the passage of the ab- 
 sorbed substances into the blood {van Helmont, Sylvius, Ettmiiller). Lavoisier (1777) was the 
 first to ascribe the heat to the combustion of carbon in the lungs. 
 
 After the construclion of the thermometer by Galileo, Sanctorius (1626) made the first fher- 
 mometric observations on sick persons, while the first calorimetric observations were made by 
 Lavoisier and Laplace. 
 
 Comparative observations are given at \ 207, and also under Hybernation (§ 225). 
 
PHYSIOLOGY- METABOLIC PHENOMENA 
 
 By the term metabolism are meant all those phenomena, whereby all — even 
 the most lowly — living organisms are capable of incorporating the substances 
 obtained from their food into their tissues, and making them an integral part of 
 their own bodies. This part of the process is known as assimilation. Further, 
 the organism in virtue of its metabolism forms a store of potential energy, which 
 it can transform into kinetic energy, and which, in the higher animals at least, 
 appears most obvious in the form of muscular work and heat. The changes of 
 the constituents of the tissues, by which these transformations of the poten- 
 tial energy are accompanied, result in the formation of excretory products, 
 which is another part of the process of metabolism. The normal metabolism 
 requires the supply of food quantitatively and qualitatively of the proper kind, 
 the laying up of this food within the body, a regular chemical transformation of 
 the tissues, and the preparation of the effete products which have to be given out 
 through the excretory organs. [Synthetic or constructive metabolism is spoken of as 
 Anabolic, and destructive or analytical metabolism as Katabolic metabolism.] 
 
 229. THE MOST IMPORTANT SUBSTANCES USED AS 
 FOOD. — Water. — When we remember that 58.5 per cent, of the body con-j 
 sists of water, that water is being continually given off by the urine and faeces, as well 
 as through the skin and lungs, that the processes of digestion and absorption 
 require water for the solution of most of the substances used as food, and that 
 numerous substances excreted from the body require water for their solution, e.g., 
 in the urine, the great importance of water and its continual renewal within the 
 organism are at once apparent. As put by Hoppe-Seyler, all organisms live in f 
 water, and even in running water, a saying which ranks with the old saying — j 
 " Corpora non agunt nisi fluida." 
 
 Water — as far as it is not a constituent of all fluid foods — occurs in different forms as drink : (1) 
 Rain water, which most closely resembles distilled or chemically pure water, always contains 
 minute quantities of C0 2 , NH 3 , nitrous and nitric acids. (2) Spring water usually contains! 
 much mineral substance. It is formed from the deposition of watery vapor or rain from the air,' 
 which permeates the soil, containing much C0 2 ; the C0 2 is dissolved by the water, and aids in 
 dissolving the alkalies, alkaline earths and metals which appear in solution as bicarbonates, e.g., of 
 lime or iron oxide. The water is removed from the spring by proper mechanical appliances, or it 
 bubbles up on the surface in the form of a "spring." (3) The running water of rivers usually 
 contains much less mineral matter than spring water. Spring water floating on the surface rapidly 
 gives off its C0 2 , whereby many substances — e.g., lime — are thrown out of solution and deposited 
 as insoluble precipitates. 
 
 Gases. — Spring water contains little O, but much C0 2 , the latter giving to it its fresh taste. 
 Hence, vegetable organisms flourish in spring water, while animals requiring, as they do, much O, 
 are but poorly represented in such water. Water flowing freely gives up C0 2 , and absorbs O from 
 the air, and thus affords the necessary conditions for the existence of fishes and other marine ani- 
 mals. River water contains fa to -fa of its volume of absorbed gases, which may be expelled by 
 boiling or freezing. 
 
 Drinking water is chiefly obtained from springs. River water, if used for this purpose, must be 
 filtered, to get rid of mechanically suspended impurities. For household purposes a charcoal filter 
 may be used, as the charcoal acts as a disinfectant. Alum has a remarkable action; if 0.0001 per 
 cent, be added, it makes turbid water clear. 
 
 Investigation of Drinking Water. — Drinking water, even in a thick layer, 
 ought to be completely colorless, not turbid, and without odor. Any odor is best 
 
 373 
 
374 SALTS AND OTHER SUBSTANCES IN WATER. 
 
 recognized by heating it to 50° C, and adding a little caustic soda. It ought not 
 to be too hard, i.e., it ought not to contain too much lime (and magnesia) salts. 
 
 By the term " degree of hardness " of a water is meant the unit amount of lime (and magne- 
 sia) in 100,000 parts of water; a water of 20 degrees of hardness contains 20 parts of lime (cal- 
 cium oxide) combined with G0 2 , sulphuric or hydrochloric acids (the small amount of magnesia 
 may be neglected). A good drinking water ought not to exceed 20 degrees of hardness. The 
 hardness is determined by titrating the water with a standard soap solution, the result being the for- 
 mation of a scum of lime soap on the surface. The hardness of unboiled water is called its total 
 hardness, while that of toiled water is called permanent hardness. Boiling drives off the C0 2 , 
 and precipitates the calcium carbonate, so that the water at the same time becomes softer. 
 
 The presence of sulphuric acid, or sulphates, is determined by the water becoming turbid on 
 adding a solution of barium chloride and hydrochloric acid. 
 
 Chlorine occurs in small amount in pure spring water, but when it occurs there in large amount 
 — apart from its being derived from saline springs, near the sea or manufactories — we may conclude 
 that the' water is oontaminated from water closets or dunghills, so that the estimation of chlorine 
 is of importance. For this purpose use a solution (A) of 17 grms. of crystallized silver nitrate in 1 
 litre of distilled water; 1 cubic centimetre of this solution precipitates 3.55 milligrammes of chlor- 
 ine as silver chloride. Use also (B) a cold saturated solution of neutral potassium chromate. Take 
 50 cubic centimetres of the water to be investigated, and place it in a beaker, add to it 2 to 3 drops 
 of B, and allow the fluid A to run into it from a burette until the white precipitate first formed 
 remains red, even after the fluid has been stirred. Multiply the number of cubic centimetres of A 
 used by 7.1, arid this will give the amount of chlorine in 100,000 parts of the water. Example — 
 50 c.cmtr. requires 2.9 c.cmtr. of the silver solution, so that 100,000 parts of the water contain 2.9 
 X 7.1 = 20.59 parts chlorine (JCubel, Tiemann). Good water ought not to contain more than 15 
 milligrammes of chlorine per litre. 
 
 The presence of lime may be ascertained by acidulating 50 cubic centimetres of the water with 
 HC1 and adding ammonia in excess, and afterward adding ammonia oxalate ; the white precipitate 
 is lime oxalate. According to the degree of turbidity we judge whether the water is " soft " (poor 
 in lime), or "hard " (rich in lime). 
 
 Magnesia is determined by taking the clear fluid of the above operation, after removing the 
 precipitate of lime, and adding to it a solution of sodium phosphate and some ammonia ; the crys- 
 talline precipitate which occurs is magnesia. 
 
 The more feeble all these reactions are which indicate the presence of sulphuric acid, chlorine, 
 lime and magnesia, the better is the water. In addition, good water ought not to contain more than 
 traces of nitrates, nitrites, or compounds of ammonia, as their presence indicates the decomposition 
 of nitrogenous organic substances. 
 
 For nitric acid, take 100 cubic centimetres of water acidulated with two to three drops of concen- 
 trated sulphuric acid, add several pieces of zinc,together with a solution of potassium iodide, and starch 
 solution; a blue color indicates nitric acid. The following test is very delicate : Add to half a drop of 
 water, in a capsule, two drops of a watery solution of Brucinum sulphuricum, and afterward several 
 drops of concentrated sulphuric acid; a rose-red coloration indicates the presence of nitric acid. 
 
 The presence of nitrous acid is ascertained by the blue coloration which results from the addi- 
 tion of a solution of potassium iodide, and solution of starch, after the water has been acidulated 
 with sulphuric acid. 
 
 Compounds of ammonia are detected by Nessler's reagent, which gives a yellow or reddish 
 coloration when a trace of ammonia is present in water ; while a large amount of these compounds 
 gives a brown precipitate of the iodide of mercury and ammonia. 
 
 The contamination of water by decomposing animal substance is determined by the amount of 
 N it contains. In most cases it is sufficient to determine the amount of nitric acid present. For 
 this purpose we require (A) a solution of 1. 871 grms. potassium nitrate in I litre distilled water; 1 
 cubic centimetre contains I milligramme nitric acid ; (B) a dilute solution of indigo, which is pre- 
 pared by rubbing together one part of pulverized indigotin with six parts H 2 S0 4 , and allowing the 
 deposit to subside, when the blue fluid is poured into forty times its volume of distilled water, and 
 filtered. This fluid is diluted with distilled water until a layer, 12 to 15 mm. in thickness, begins to 
 be transparent. 
 
 To test the activity of B, place I cubic centimetre of A in 24 cubic centimetres water ; add some 
 common salt and 50 cubic centimetres concentrated sulphuric acid, and allow B to flow from a 
 burette into this mixture until a faint green mixture is obtained. The number of cubic Centimetres 
 of B used correspond to 1 milligramme of nitric acid. 
 
 25 cubic centimetres of the water to be investigated are mixed with 50 cubic centimetres of con- 
 centrated H 2 S0 4 , and titrated with B until a green color is obtained. This process must be repeated, 
 and on the second occasion the solution B must be allowed to flow in at once, when, usually, some- 
 what more indigo solution is required to obtain the green solution. The number of cubic centi 7 
 metres of B (corresponding to the strength of B, as determined above) indicates the amount of 
 nitric acid present in 25 c. cmtr. of the water investigated. As much as io milligrammes nitric acid 
 have been found in spring water [Marx, Trommsdorff). 
 
MAMMARY GLANDS. 375 
 
 Sulphuretted Hydrogen is recognized by its odor, also by a piece of blotting paper moistened 
 with alkaline solution of lead becoming brown when it is held over the boiling water. If it occurs 
 as a compound in the water, sodium nitro-prusside gives a reddish-violet color 
 
 It is of the greatest importance that drinking water should be free from the presence of organic 
 matter in a state of decomposition. Organic matter in a state of decomposition, and the organisms 
 therewith associated, when introduced into the body, may give rise to fatal maladies, e. g., cholera 
 and typhoid fever. This is the case when the water supply has been contaminated from water 
 which has percolated from water closets, privies and dung pits.- The presence of organic matter may 
 be detected thus : ( I ) A considerable amount of the water is evaporated to dryness in a porcelain 
 vessel; if the residue be heated again, a brown or black color indicates the presence of a consider- 
 able amount of organic matter; and if it contain N, there is an odor of ammonia. Good water 
 treated in this way gives only a light-brown stain. The presence of micro-organisms may be 
 determined microscopically after evaporating a small quantity of water on a glass slide. (2) The 
 addition of potassio-gold chloride added to the water gives a black frothy precipitate after long stand- 
 ing- (3) A solution of potassium permanganate, added to the water in a covered jar, gradually 
 becomes decolorized, and a brownish precipitate is formed. 
 
 Water containing much organic matter should never be used as drinking water, and this is espe- 
 cially the case when there is an epidemic of typhoid fever, cholera or diarrhoea. In all such cir- 
 cumstances the water ought to be boiled for a long time, whereby the organic germs are killed. 
 The insipid taste of the water after boiling may be corrected by adding a little sugar or lime juice. 
 
 230. THE MAMMARY GLANDS AND MILK.— Milk Duct.— About 20 galactophorous 
 ducts open singly upon the surface of the nipple. Each of these, just before it opens on the surface, 
 is provided with an oval dilatation — the sinus lacteus. When traced into the gland, the galacto- 
 phorous ducts divide like the branches of a tree, and a large branch of the duct passes to each lobe 
 of the gland — all the lobes being held together by loose connective tissue. Only during lactation 
 do all the fine terminations of the ducts communicate with the globular glandular acini. Every 
 gland acinus consists of a membrana propria, surrounded externally with a network of branched 
 connective-tissue corpuscles, and lined internally with a somewhat flattened, polyhedral layer of 
 nucleated secretory cells (Fig. 219). The size of the lumen of 
 
 the acini depends upon the secretory activity of the glands; when YlG. 2IQ. 
 
 it is large, it is filled with milk containing numerous refractive fatty 
 granules. The milk ducts consist of fibrillar connective tissue. 
 Some fibres are arranged longitudinally, but the chief mass are 
 disposed circularly, and are permeated externally with elastic fibres, 
 while in the finer ducts there is a membrana propria continuous 
 with that of the gland acini. The ducts are lined by cylindrical 
 epithelium. 
 
 Curing the first few days after delivery, the breasts secrete a 
 small amount of milk of greater consistence and of a yellow color 
 — the colostrum — in which large cells, filled with fatty granules, 
 occur — the colostrum corpuscles (Fig. 221). Sometimes a nucleus 
 is observable within them, and rarely they exhibit amseboid move- 
 ments (Fig. 220, c, d, e). The regular secretion of milk begins Acin i° f '!jf, n"™"""? gland of a 
 r , * *> ? ' ' ' ' T , r ° . , . ... b „ sheep during lactation, a, mem- 
 
 after three to four days. It was formerly supposed that the cells brana propria ; 6, secretory epi- 
 
 of the acini underwent a fatty degeneration, and thus produced the thelium. 
 
 fatty granules of the milk. It is more probable, from the observa- 
 tions of Strieker, Schwarz, Partsch and Heidenhain, that the cells of the acini manufacture the 
 fatty granules, and their protaplasm eliminates them, at the same time forming the clear fluid part 
 of the milk. , 
 
 Changes during Secretion. — Partsch and Heidenhain found that the secretory- 
 cells in the passive non-secreting gland (Fig. 220, 1) were flat, polyhedral and 
 uni- nucleated, while the secreting cells (Fig. 220, II) often contained several nuclei, 
 were more albuminous, higher, and cylindrical in form. The edge of the cell 
 directed toward the lumen of the acinus undergoes changes during secretion. 
 Fatty granules are formed in this part of the cell, and are afterward extruded. 
 The decomposed portion of the cell is dissolved in the milk, and the fatty gran- 
 ules become free as milk globules (Fig. 220, II, a). If nuclei are present in that % 
 part of the cell which are broken up, they also pass into the milk, and give rise ) 
 to the presence of nuclein in the secretion. 
 
 Besides the milk globules and colostrum corpuscles, Rauber has found leucocytes undergoing 
 fatty degeneration and single pale cells (/). Occasionally milk globules are found with traces of 
 the cell substance adhering to their surface (b). 
 
 Formation of Milk. — Concerning the formation of the individual constituents of milk, H. 
 Thierfelder, who digested fresh mammary glands directly after death, found that during the diges- 
 
376 
 
 STRUCTURE OF THE MAMMA. 
 
 tion of the glands, at the temperature of the body, a reducing substance, probably lactose, was 
 formed by a process of fermentation. The mother substance (saccharogen) is soluble in water, but 
 not in alcohol or ether, is not destroyed by boiling, and is not identical with glycogen. The ferment 
 which forms the lactose is connected with the gland cells ; it does not pass into the milk, nor into a 
 watery extract of the gland. During the digestion of the mammary glands at the temperature of 
 the body, casein is formed, probably from serum albumin, by a process of fermentation. This 
 ferment occurs in the milk. 
 
 The nipple and its areola are characterized by the presence of pigment — more abundant during 
 pregnancy — in the rete Malpighii of the skin, and by large papilUe in the cutis vera. Some of the 
 papillse contain touch corpuscles. Numerous non-striped muscular fibres surround the milk ducts 
 in the deep layers of the skin and in the subcutaneous tissue, which contains no fat. These muscular 
 fibres can be traced following a longitudinal course to the termination of the ducts on the surface. 
 The small glands of Montgomery, which occur on the areola during lactation, are just small milk 
 glands, each with a special duct opening on the surface of the elevation. 
 
 Arteries proceed from several sources to supply the mamma, but their branches do not accom- 
 pany the milk ducts ; each gland acinus is surrounded by a network of capillaries, which commu- 
 nicate with those of adjoining acini by small arteries and veins. The veins of the areola are 
 arranged in a circle (drculus Halleri). The nerves are derived from the supraclavicular, and the 
 II-IV-VI intercostals ; they proceed to the skin over the gland, to the very sensitive nipple, to the 
 blood vessels and non-striped muscle of the nipple, and to the gland acini, where the mode of ter- 
 mination is still unknown. Lymphatics surround the alveoli, and they are often full. The milk 
 appears to be prepared from the lymph contained in the lymphatics surrounding the acini. 
 
 The comparative anatomy of the mamma. The rodents, insectivora, and carnivora have 10 
 to 12 teats, while some of them have only 4. The pachydermata and ruminantia have 2 to 4 
 abdominal teats ; the whale has 2 near the vulva. The apes, bats, vegetable-feeding whales, ele- 
 
 Fig. 220 
 
 n 
 
 mi ca ° 
 
 I. Inactive acinus of the mamma. 
 
 II. During the secretion of milk. — a, b, milk globules ; c, d, e, colostrum corpus- 
 cles ; /, pale cells (bitch). 
 
 phants, and sloths have 2, like man. In the marsupials the tubes are arranged in groups, which 
 open on a patch of skin devoid of hair, without any nipple. The young animals remain within the 
 mother's pouch, and the milk is expelled into their mouths by the action of a muscle — the compressor 
 mammae. 
 
 The development of the human mamma begins in both sexes during the third month ; at the 
 fourth and fifth months a few simple tubular gland ducts are arranged radially around the position 
 of the future nipple, which is devoid of hair. In the new-born child the ducts are branched twice 
 or thrice, and are provided with dilated extremities, the future acini. Up to the twelfth year, in 
 both sexes, the ducts continue to divide dendritically, but without any proper acini being formed. 
 
 In the girl at puberty the ducts branch rapidly ; but the acini are formed only at the periphery of 
 the gland, while during pregnancy acini are also formed in the centre of the gland, while the con- 
 nective tissue at the same time becomes somewhat more opened out. At the climacteric period, 
 or menopause, all the acini and numerous fine milk ducts degenerate. In the adult male the gland 
 remains in the non-developed infantile condition. Accessory or supernumerary glands upon the 
 breast and abdomen are not uncommon ; sometimes the mamma occurs in the axilla, on the back, 
 over the acromion process, or on the leg. A slight secretion of milk in a newly-born infant is 
 normal. 
 
 During the evacuation of the milk (500-1500 cubic centimetres daily), there is not only the 
 mechanical action of sucking, but also the activity of the gland itself ((j 152). This consists in the 
 erection of the nipple, whereby its non-striped muscular fibres compress the sinuses on the milk 
 ducts, and empty them, so that the milk may flow out in streams. The gland acini are also excited 
 to secretion reflexly by the stimulation of the sensory nerves of the -nipple. The vessels of the 
 gland are dilated, and there is a copious transudation into the gland, the transuded fluid being 
 manufactured into milk under the influence of the secretory protoplasm. The amount of secretion 
 
MILK AND ITS PREPARATIONS. 377 
 
 depends upon the blood pressure {Rdhrig). During sucking, not only is the milk in the gland 
 extracted, but new milk is formed, owing to the accelerated secretion. Emotional disturbances — 
 anger, fear, etc. — arrest the secretion. Laffont found that stimulation of the mammary nerve (bitch) 
 caused erection of the teat, dilatation of the vessels, and secretion of milk. After section of the 
 cerebro-spinal nerves going to the mamma, Eckhard observed that erection of the teat ceased, 
 although the secretion of milk in a goat was not interrupted. The rarely observed galactorrhea 
 is perhaps to be regarded as a paralytic secretion analogous to the paralytic secretion of saliva. 
 Heidenhain and Partsch found that the secretion (bitch) was increased by injecting strychnine or 
 curara after section of the nerves of the gland. The " milk fever," which accompanies the first 
 secretion of milk, probably depends on stimulation of the vasomotor nerves, but this condition must 
 be studied in relation with the other changes which occur within the pelvic cavity after birth. 
 [Some substances, such as atropin, arrest the secretion of milk.] 
 
 231. MILK AND ITS PREPARATIONS.— Milk represents a com- 
 plete or typical food in which are present all the constituents necessary for 
 maintaining the life and growth of the body [of an infant (§ 236). If an adult 
 were to live on milk alone, to get the 23 oz. of dry solids necessary, he would 
 have to take 9 pints of milk daily, which would give far too much water, fat, and 
 proteids.] To every 10 parts of proteids there are 10 parts fat and 20 parts sugar. 
 Relatively more fat than albumin is absorbed from the milk (Hubner) ; while a 
 part of both is excreted in the faeces. 
 
 Fig. 221. 
 
 Microscopic appearance of milk (M) upper half of the figure, and colostrum (C) lower half. 
 
 Characters. — Milk is an opaque, bluish-white fluid with a sweetish taste and a 
 characteristic odor, probably due to the peculiar volatile substances derived from 
 the cutaneous secretions of the glands, and it has a specific gravity of 1026 to 
 1035 {Radenhausen). When it stands for a time, numerous milk globules, butter 
 globules, or cream, collect on its surface, under which there is a bluish watery 
 fluid. Human milk is always alkaline ; cow's milk may be alkaline, acid, or 
 amphoteric ; while the milk of carnivora is always acid. 
 
 Milk Globules. — When milk is examined microscopically, it is seen to contain 
 numerous small, highly refractive oil globules, floating in a clear fluid — the milk 
 plasma (Figs. 220, a, b, 221); while colostrum corpuscles and epithelium from 
 the milk ducts are not so numerous. The white color and opacity of the milk are 
 due to the presence of the milk globules which reflect the light ; the globules con- 
 sist of a fat, or butter, and are apparently surrounded with a very thin envelope of 
 casein or haptogen membrane. [This, however, is denied ; it is more probable 
 that the casein exists in a swollen-up condition rather than in a state of true solu- 
 tion.] 
 
 If acetic acid be added to a microscopic preparation of milk, this caseous envelope is dissolved, 
 the fatty granules are liberated, and they run together to form irregular masses. If cow's milk be 
 
378 FATS AND PLASMA OF MILK. 
 
 shaken with caustic potash, the casein envelopes are dissolved, and if ether be added the milk be- 
 comes clear and transparent, as the ether dissolves out all the fatty particles in the solution. Ether 
 cannot extract the fat from cow's milk until acetic acid or caustic potash is added to liberate the 
 fats from their envelopes ; but shaking with ether is sufficient to extract the fats from human milk 
 (Radenhausen). Some observers deny that an envelope of casein exists, and according to them 
 milk is a simple emulsion, kept emulsionized owing to the colloid, swollen-up casein in the milk 
 plasma (Kehrer). The treatment of milk with potash and ether makes the casein unable any 
 longer to preserve the emulsion (Soxhlet). 
 
 The fats of the milk globules are the triglycerides of stearic, palmitic, oleic 
 (very little), myristic, arachinic (butinic), capric, caprylic, caproic, and butyric 
 acids, with traces of acetic and formic acids (Heintz), and cholesterin. 
 
 Butter. — When milk is beaten or stirred for a long time (i. e., churned), the fat of the milk 
 globules is ultimately obtained in the form of butter, owing to the rupture of the envelopes of casein. 
 Butter is soluble in alcohol and ether, and it is clarified by heat (90 C), or by washing in water at 
 40 C. When allowed to stand exposed to the air it first becomes sour, owing to the formation of 
 lactic acid, and afterward becomes rancid, owing to the glycerine of the neutral fats being decom- 
 posed by fungi into acrolein and formic acid, while the volatile fatty acids give it its rancid odor. 
 
 The milk plasma, obtained by filtration through clay filters or membranes, is 
 a clear, slightly opalescent fluid, and contains casein (§ 249, III, 3), some serum 
 albumin (§ 32), peptone (0.13 per cent.), nuclein, and a trace of diastatic 
 ferment (in human milk — Bkchamp}. 
 
 Whether other peculiar chemical bodies, such as proteids are present in milk, e.g., lactoprotein 
 {Milton and Comaitte, Liebermann), globulin, albumose, galactin, etc., is disputed by some chem- 
 ists (Hoppe-Seyler). 
 
 When milk is boiled the albumin coagulates, while the surface also becomes 
 covered with a thin scum or layer of casein, which has become insoluble [the rest 
 of the milk remaining fluid]. 
 
 Casein. — When milk is filtered through fresh animal membranes [Hoppe-Seyler), or through a 
 clay filter, the casein does not pass through (Helmholtz, Zahn, Kehrer). 
 
 Precipitation. — It is precipitated by adding crystals of MgS0 4 to saturation. [If to milk twice 
 its volume of a saturated solution of NaCl and crystals of NaCl be added, and the whole shaken 
 thoroughly, casein is precipitated, and carries down with it fat, so that the clear filtrate contains the 
 lactose and coagulable proteids.] 
 
 The plasma contains milk sugar (§252); a carbohydrate resembling dextrin 
 {Ritthausen), (? lactic acid), lecithin, urea, extractives, kreatin, sarkin, (potassic 
 sulphocyanide in cow's milk), sodic and potassic chlorides, alkaline phosphates, 
 calcium and magnesium sulphates, alkaline carbonates, traces of iron, fluorine, and 
 silica (C0 2 , N, O). 
 
 The coagulation of milk depends upon the coagulation of its casein. In milk, casein is com- 
 bined with calcium phosphate, which keeps it in solution ; acids which act on the calcium phosphate 
 cause coagulation ot the casein (acetic and tartaric acids in excess redissolve it). All acids do not 
 coagulate human milk (Simon and Lehmann). It is coagulated with two or more drops of hydro- 
 chloric acid (0.1 percent.) or acetic acid (0.2 percent.). The spontaneous coagulation of milk after 
 it has stood for a time, especially in a warm place,' is due to the formation of lactic acid, which is 
 formed from the milk su^ar in the milk by the action of bacterium lacticum [which is introduced 
 from without (Pasteur, Cohn, Lister)} (§ 184, I). It changes the neutral alkaline phosphate in 
 the acid phosphate, takes the casein from the calcium phosphate, and precipitates the casein. The 
 sugar is decomposed into lactic acid and C0 2 . 
 
 Rennet (g 250, 9, d, <S 166, II) coagulates milk with an alkaline reaction (sweet, whey). This 
 ferment decomposes the casein into the precipitated cheese, and also into the slightly soluble whey 
 albumin (Hammersten, Korster), so that the coagulation by rennet is a process quite distinct from 
 the coagulation of milk by the gastric and pancreatic juices [and also from the precipitation pro- 
 duced by acids. The presence of calcium phosphate seems to be necessary for the complete action 
 of the rennet (ffammersten).~\ 
 
 [Experiments. — Warm a little milk to 40° C, and add a few drops of commercial rennet, set- 
 ting aside the mixture in a warm place ; a solid coagulum is soon formed, and by and by the whey 
 separates from it If the milk be previously diluted with water, no coagulum is formed ; and if the 
 rennet be boiled before, it, like other ferments, is destroyed. A solution of rennet may be prepared 
 by extracting the fourth stomach of the calf with glycerine.] 
 
COMPOSITION OF MILK. 379 
 
 [A milk-coagulating ferment is found in certain plants (artichokes, figs, Carica papays), and 
 causes milk to coagulate in neutral or alkaline solution (Bagins&y). It is also found in the small < 
 intestine of the calf, while a 5 per cent. NaCl solution of the seeds of Withania coagulans coagu- 
 lates milk in an alkaline medium (Aitchison and Lea). ~\ 
 
 [When the milk is coagulated we obtain the curd, consisting of casein with some milk globules 
 entangled in it ; the whey contains some soluble albumin and fat, and the great proportion of the 
 salts and milk sugar, together with lactic acid.] 
 
 Boiling (by killing all the lower organisms), sodium bicarbonate (y^inj), ammonia, salicylic acid 
 (yaVtr)' glycerine, and ethereal oil of mustard prevent the spontaneous coagulation. Fresh milk 
 makes tincture of guaiacum blue, but boiled milk does not do so (ScAacht, C. Arnold). When 
 milk is exposed to the air for a long time, it gives off C0 2 and absorbs O ; the fats are increased 
 (? owing to the development of fungi in the milk), and so are the alcoholic and ethereal extracts, 
 from the decomposition of the casein (Hoppe-Seyler, Kemmerich). According to Schmidt-Mul- 
 heim, some of the casein becomes converted into peptone, but this occurs only in unboiled milk. 
 
 Composition. — 100 parts of milk contain — 
 
 Human. Cow. Goat. Ass. 
 
 Water 87.24 to 90.58 86.23 86 - 8 5 8 9-°' 
 
 Solids 9.42 " 12.39 '3-77 '3S 2 IO -99 
 
 Atbtin :::: t: »?y *>**»{ ill 2 ,ll] *■« 
 
 Butter 2.67 " 4.30 4-5° 4-34 185 
 
 Milk sugar . . . 3.15" 609 4.93 3.78 1 
 
 Salts 0.14" 0.28 0.6 0.65/ iui 
 
 Human milk contains less albumin, which is more soluble than the albumin in the milk of 
 animals. 
 
 Colostrum contains much serum albumin, and very little casein, while all the other substances, 
 and especially the fats, are more abundant. , 
 
 Gases. — Pfliiger and Setschenow found in 100 vols, of milk 5.01 to 7.60 C0 2 ; 0.09 to 0.32 O ; 
 0.70 to 1.41 N, according to volume. Only part of the C0 2 is expelled by phosphoric acid. 
 
 Salts. — The potash, salts (as in blood and muscle) are more abundant than the soda compounds, 
 while there is a considerable amount of calcium phosphate, which is necessary for forming the 
 bones of the infant. Wildenstein found in 100 parts of the ash of human milk — sodium chloride, 
 IO -73! potassium chloride, 26.33 ; potash, 21.44; lime, 18.78; magnesia, 0.87 ; phosphoric acid, 
 19; ferric phosphate, 0.21 ; sulphuric acid, 2.64; silica, traces. The amount oi salts present is 
 affected by the salts of the food. 
 
 Conditions Influencing the Composition. — The more frequently the breasts are emptied, the 
 richer the milk becomes in casein. The last milk obtained at any time is always richer in butter, 
 as it comes from the most distant part of the gland — viz., the acini (Reiset, Heynsius, For.ster, ae 
 Leon) . Some substances are diminished and others increased in amount, according to the time 
 after delivery. The following are increased : Until the 2d month after delivery, casein and fat ; until 
 the 5th month, the salts (which diminish progressively from this time onward) ; from 8-loth 
 month, the sugar. The following are diminished: From io-24th month, casein; from 5-6th 
 and 10-lith months, fat; during 1st month, the sugar; from the 5th month, the salts. 
 
 [Influence of Drugs. — That cow's milk is influenced by the pasture and food is well known. 
 Turnip as food gives a peculiar odor, taste and flavor to milk, and so do the fragrant grasses. The 
 mental state of the nurse influences the quantity and quality of milk, while many substances given 
 as medicines reappear in the milk, such as dill, copaiba, conium, aniseed, garlic ; especially those 
 containing aromatic volatile oils, as the umbelliferae and cruciferae ; also some of the following 
 drugs : potassium iodide, arsenic, mercury, opium, rhubarb, or its active principle, the purgative 
 principle of castor oil, and the cathartic principle of senna. Jaborandi is the nearest approach to a 
 galactagogue, but its action is temporary. Atropin is a true anti-galactagogue. The composition 
 of the milk may be affected by using fatty food, by the use of salts, and above all, by the diet 
 ( Bolan).] 
 
 [Milk may be a vehicle for communicating disease — by direct contamination from the water 
 used for adulterating it or cleansing the vessels in which it is kept; by the milk absorbing delete- 
 rious gases ; by the secretion being altered in diseased animals.] 
 
 The greater the amount of milk that is secreted (woman), the more casein and sugar, and the less 
 butter it contains. The milk of a primipara is less watery. Rich feeding, especially proteids 
 (small amount of vegetable food), increase the amount of milk and the casein, sugar, and fat in it ; 
 a large amount of carbohydrates (not fats) increases the amount of sugar. 
 
 Substitutes. — If other than human milk has to be used, ass's milk most closely resembles human 
 milk. Cow's milk is best when it contains plenty of fatty matters — it must be diluted with its own 
 volume of water at first, and a little milk sugar added. The casein of cow's milk differs qualita- 
 tively from that of human milk (Biedert) ; its coagulated floccuH or curd are much coarser than 
 the fine curd of human milk, and they are only % dissolved by the digestive juices, while human 
 milk is completely dissolved. Cow's milk when boiled is less digestible than unboiled (£. Jessen). 
 
 Milk ought not to be kept in zinc vessels, owing to the formation of zinc lactate. 
 
380 TESTS FOR MILK. 
 
 [Milk exposed to light becomes sour more rapidly, and the cream separates quicker; after a 
 time there is a very acid reaction, an evolution of gases, and few bacteria are present, while in 
 milk kept in the dark the former processes go on more slowly, while there is a putrid fermentation 
 without the evolution of gas, but with many bacteria and a feeble acid reaction (Albini and 
 Malberla).] 
 
 Tests for Milk. — The amount of cream is estimated by placing the milk for twenty- four hours 
 in a tall cylindrical glass graduated into a hundred parts, or creamometer ; the cream collects on 
 the surface, and ought to form from 10 to 24 vols, per cent. [The cream is generally about T jf r ] 
 The specific gravity (fresh cow's milk, 1029 to 1034; when creamed, 1032 to 1040) is estimated 
 with an aerometer or lactometer at 15 C. The sugar is estimated by titration with Fehling's 
 solution (\ 150, II), but in this case 1 cubic centimetre of this solution corresponds to 0.0067 6™- 
 of milk sugar; or its amount may be estimated with the polariscopic apparatus (g 150). The pro- 
 teids are precipitated and the fats extracted with ether. The fats in Iresh milk form about 3 per 
 cent., and in skimmed milk iyi per cent. The amount of water in relation to the milk globules 
 is estimated by the lactoscope or the diaphanometer of Donne (modified by Vogel and Hoppe- 
 Seyler), which consists of a glass vessel with plane parallel sides placed I centimetre apart. A 
 measured quantity of milk is taken, and water is added to it from a burette until the outline of a 
 candle flame placed at a distance of 1 metre can be distinctly seen through the diluted milk. This 
 is done in a dark room. For 1 cubic centimetre of good cow's milk, 70 to 85 centimetres water 
 are required. [Other forms of lactoscope are used, all depending on the same principle of an 
 optical test, viz., that the opacity of milk varies with and is proportional to the amount of butter fats 
 present, i. e., the oil globules. Bond uses a shallow cylindrical vessel with the bottom covered by 
 black lines on a white surface. A measured quantity of water is placed in this vessel, and milk 
 is added, drop by drop, until the parallel lines on the pattern at the bottom of the dish cease 
 to be visible. On counting the number of drops, a table accompanying the appliance gives 
 the percentage of fats. This method gives approximate results. In all cases it is well to use 
 fresh milk.] 
 
 Various substances pass into the milk when they are administered to the mother — many 
 odoriferous vegetable bodies, e.g., anise, vermuth, garlic, etc. ; opium, indigo, salicylic acid, iodine, 
 iron, zinc, mercury, lead, bismuth, antimony. In osteomalacia the amount of lime in the milk is 
 increased ( Gusserow). Potassium iodide diminishes the secretion of milk by affecting the secretory 
 function (Stump/). Among abnormal constituents are — haemoglobin, bile pigments, mucin, blood 
 .corpuscles, pus, fibrin. Numerous fungi and other low organisms develop in evacuated milk, and 
 the rare blue milk is due to the development of Bacterium cyanogeneum (Fuchs, Neeken). The 
 milk serum is blue, not the fungus. Blue milk is unhealthy, and causes diarrhoea (Mosler). There 
 are fungi which make milk bluish-black ox green. Red and yellow milk are produced by a similar 
 action of chromogenic fungi (J 184). The former is produced by Micrococcus prodigiosus, which 
 is colorless. The color seems to be due to fuchsin. The yellow color is produced by Bacterium 
 synxanthum (Ehi-enberg). Some of the pigments seem to be related to the aniline, and others to 
 the phenol coloring matters (Huppe). 
 
 The rennet- like action of bacteria is a widely diffused property of these organisms ; they 
 coagulate and peptonize casein and may ultimately produce further decompositions. The butyric 
 acid bacillus (g 184) first coagulates casein, then peptonizes it, and finally splits it up, with the evo- 
 lution of ammonia (Huppe). 
 
 Milk becomes stringy, owing to the action of cocci (Schmidt, Miilkeim), which form a stringy 
 substance [ = dextran, C 12 H 10 O 10 (Scheibler)"], just as beer or wine undergoes a similar or ropy 
 change. [The milk of diseased animals may contain or transmit directly infectious matter.] 
 
 Preparations of Milk — (1) Condensed milk — 80 grms. cane sugar are added to I litre of 
 milk; the whole is evaporated to ^ ; and while hot sealed up in tin cans (Lignac). For children 
 one teaspoonful is dissolved in a pint of cold water, and then boiled. 
 
 (2) Koumiss is prepared by the Tartars from mare's milk. Koumiss and sour milk are added 
 to milk, the whole is violently stirred, and it undergoes the alcoholic fermentation, whereby the 
 milk sugar is first changed into galactose, and then into alcohol ; so that koumiss contains 2 to 3 per 
 cent, of alcohol ; while the casein is at first precipitated, but is afterward partly redissolved and 
 changed into acid albumin and peptone (Dochmann). Tartar koumiss seems to be produced by 
 the action of a special bacterium (Diaspora Caucasia, Kern). 
 
 (3) Cheese is prepared by coagulating milk with rennet, allowing the whey to separate, and 
 adding salt to the curd. When kept for a long time, cheese "ripens," the casein again becomes 
 soluble in water, probably from the formation of soda albuminate ; in many cases it becomes semi- 
 fluid when it takes the characters of peptones. When further decomposition occurs, leucin and 
 tyrosin are formed. The fats increase at the expense of the casein, and they again undergo further 
 change, the volatile fatty acids giving the characteristic odor. . The formation of peptone, leucin, 
 tyrosin and the decomposition of fat recalls the digestive processes. 
 
 [Cheese is coagulated casein entangling more or less fat, so that the richness of the cheese will 
 depend upon the kind of milk from which it is made. There are, in this sense, three kinds of 
 cheese, whole milk, skim milk, and cream cheese, the last being represented by Stilton, Roquefort, 
 Cheshire, etc. 
 
FLESH AND ITS PREPARATIONS. 
 The composition is shown in the following table, after Bauer : — 
 
 381 
 
 
 Water. 
 
 Nitrogeneous 
 Matter. 
 
 Fat. 
 
 Extractives. 
 
 Ash. 
 
 
 35-75 
 46.82 
 48.02 
 
 7.16 
 27.62 
 32.6S 
 
 30.43 
 
 20.54 
 
 8.41 
 
 2-53 
 2.97 
 6.80 
 
 4-13 
 3°5 
 4.12 
 
 Skim milk 
 
 Cream cheese, especially if it be made from goat milk, acquires a very high odor and strong 
 flavor when it is kept and " ripens ;" the casein is partly decomposed to yield ammonia and ammo- 
 nium sulphide, while the fats yield butyric, caproic and other acids.] 
 
 232. EGGS. — Eggs must be regarded as a complete food, as the organism of \ 
 the young chick is developed from them. The yelk contains a characteristic 
 proteid body — vitellin (§ 249), and an albuminate in the envelopes of the yellow 
 yelk spheres — nuclein, from the white yelk ; fats in the yellow yelk (palmitin, 
 olein), cholesterin, much lecithin; and as its decomposition product, glycerin- 
 phosphoric acid — grape sugar, pigments (lutein), and a body containing iron and 
 related to haemoglobin ; lastly, salts qualitatively the same as in blood — quantita- 
 tively as in the blood corpuscles — and gases. The chief constituent of the ■white 
 of egg is egg albumin (§ 249), together with a small amount of palmitin and 
 olein partly saponified with soda ; grape sugar, extractives ; lastly, salts, qualita- 
 tively resembling those of blood, but quantitatively like those of serum and a trace 
 of fluorine. 
 
 [The shell is composed chiefly of mineral matter (91 per cent, of calcic carbonate, 6 per cent, of 
 calcic phosphate, and 3 per cent, of organic matter). A hen's egg weighs about l}( oz., of which 
 the shell forms about T 'j. 
 
 Composition : — 
 
 White of Egg. Yelk. 
 
 Water 84.8 51.5 
 
 Proteids 12.0 15.0 
 
 Fats, etc 2.0 30.0 
 
 Mineral matter 1.2 1.4 
 
 Pigment extractives 2.1 
 
 This shows the large amount of fatly matter in the yelk.] 
 
 Relatively more of the nitrogenous constituents than the fatty constituents of 
 eggs are absorbed {Rubner). 
 
 233. FLESH AND ITS PREPARATIONS.— Flesh, in the form in 
 which it is eaten, contains, in addition to the muscle substance proper, more or 
 less of the elements of fat, connective and elastic tissue mixed with it (§ 293). 
 The following results refer to flesh freed as much as possible from the constituents. 
 The chief proteid constituent of the contractile muscular substance is myosin 1 
 (Kiihne~) ; serum albumin occurs in the fluid of the fibres, in the lymph and blood 
 of muscle. The fats are for the most part derived from the interfibrillar fat cells, \ 
 while lecithin and cholesterin come from the nerves of the muscles ; the gelatin is 
 derived from the connective tissue of the perimysium, perineurium, and the walls 
 of blood vessels and tendons. The red color of the flesh is due to the haemo- 
 globin present in the sarcous substance {Kiihne, Gscheidleri), but in some muscles, 
 e.g., the heart, there is a special pigment, myo-hsematin {MacMunn). Elastin 
 occurs in the sarcolemma, neurilemma, and in the elastic fibres of the perimysium 
 and walls of the vessels ; the small amount of keratin is derived from the endo- 
 thelium of the vessels. The chief muscular substance, the result of the retrogres- 
 sive metabolism of the sarcous substance, is kreatin ( — 0.25 per cent., Chevreul, 
 Perls); kreatinin, the inconstant inosinic acid, then lactic, or rather sarcolactic . 
 acid (§ 293). Further, taurin, sarkin, xanthin, uric acid, carnin, inosit (most| 
 abundant in the muscles of drunkards), urea (.01 per cent.), dextrin (in horse and 
 
382 
 
 FLESH AND ITS PREPARATIONS. 
 
 rabbit, not constant — Sanson, Limprichf) ; grape sugar (Meissner), but it is very 
 probably derived post-mortem from glycogen (0.43 per cent.), which occurs in 
 considerable amount in foetal muscles ( O. Nasse) ; lastly, volatile fatty acids. 
 Among the salts, potash and phosphoric acid compounds (Braconnot) are most 
 abundant ; magnesium phosphate exceeds calcium phosphate in amount. [The 
 composition varies somewhat even in different muscles of the same animal.] 
 
 In 100 parts Flesh there is, according to Schlossberger and. v. Bibra — 
 
 
 Ox. 
 
 Calf. 
 
 Deer. 
 
 Pig- 
 
 Man. 
 
 Fowl. 
 
 Carp. 
 
 Frog. 
 
 Water 
 
 Solids 
 
 Glutin 
 
 Fats 
 
 775° 
 22.50 
 
 \ 2.20 
 
 1-3° 
 1.50 
 
 78.20 
 2I.8o 
 
 2.60 
 
 I.60 
 I.40 
 
 74-63 
 
 25-37 
 
 I.94 
 
 O.50 
 
 4-75 
 
 78.30 
 21.70 
 
 2.40 
 
 0.80 
 1.70 
 
 74-45 
 2 S-55 
 
 '•93 
 
 2.07 
 
 3-7' 
 2.30 
 
 15-54 
 
 77-3° 
 22.7 
 
 3° { 
 
 1.2 
 
 1.4 
 
 16.5 
 
 79.78 
 20.22 
 
 2-35 
 
 80.43 
 '9-57 
 
 1.86 
 
 1.98 
 
 3-47 
 1. 11 
 
 11.31 
 
 2.48 
 3-4° 
 
 O.IO 
 
 11.67 
 
 Insoluble albumin, Blood vessels, 
 
 17.50 
 
 16 2 
 
 16.81 
 
 16.81 
 
 
 In 100 parts Ash there is — 
 
 
 Horse. 
 
 Ox. 
 
 Calf. 
 
 Pig- 
 
 Potash 
 
 39.40 
 
 4.86 
 
 3-88 
 1.80 
 
 35-94 
 
 3-31 
 '•73 
 5-36 
 
 4.86 
 
 0.98 
 
 34-36 
 
 3-37 
 2.07 
 8.02 
 0.15 
 
 34-40 
 
 2-35 
 1:45 
 1.99 
 
 37-79 
 4.02 
 4.81 
 7-54 
 
 
 Chalk 
 
 
 } '•«{ 
 
 I.IO 
 
 46.74 
 0.30 
 
 } io-59 { 
 0.27 
 48,13 
 
 0.40 
 
 0.62 
 
 o-35 
 
 44-47 
 
 
 0.81 
 
 
 
 
 
 
 
 
 
 
 
 
 The amount of fat in flesh varies very much, according to the condition of the animal. After 
 removal of the visible fat, human flesh contains 7.15; ox, 11.12; calf, 10.4; sheep, 3.9; wild goose, 
 8.8 ; fowl, 2.5 per cent. 
 
 The amount of extractives is most abundant in those animals which exhibit energetic muscular 
 action ; hence it is largest in wild animals. The extract is increased after vigorous muscular action, 
 when sarcolactic acid is developed, and the flesh becomes more tender and is more palatable. Some 
 of the extractives excite the nervous system, e. g., kreatin and kreatinin ; and others give to flesh its 
 characteristic agreeable flavor [" osmasome,"] but this is also partly due to the different fats of the 
 flesh, and is best developed when the flesh is cooked. The extractives in 100 parts of flesh are in 
 man and pigeon, 3 ; deer and duck, 4 ; swallow, 7 per cent. 
 
 Preparation, or Cooking of Flesh. — As a general rule, the flesh of young animals, owing to 
 the sarcolemma, connective tissue, and elastic constituents being less tough, is more tender and more 
 easily digested than the flesh of old animals ; after flesh has been kept for a time it is more friable 
 and tender, as the inosit becomes changed into sarcolactic acid and the glycogen into sugar, and this 
 again into lactic acid, whereby the elements of the flesh undergo a kind of maceration. Finely 
 divided flesh is more digestible than when it is eaten in large pieces. In cooking meat, the heat 
 ought not to be too intense, and ought not to be continued too long, as the muscular fibres thereby 
 become hard and shrink very much. Those parts are most digestible which are obtained from the 
 centre of a roast where they have been heated to 6o° to 70 C, as this temperature is sufficient, 
 with the aid of the acids of the flesh, to change the connective tissue into gelatin, whereby the fibres 
 are loosened, so that the gastric juice readily attacks them. In roasting beef, apply heat suddenly 
 at first, to coagulate a layer on the surface, which prevents the exit of the juice. 
 
VEGETABLE FOODS. 
 
 383 
 
 Meat Soup is best prepared by cutting the flesh into pieces and placing them for several hours 
 in cold water, and afterward boiling. Liebig found that 6 parts per ioo of ox flesh were dissolved 
 by cold water. When this cold extract was boiled, 2.95 parts were precipitated as coagulated 
 albumin, which is chiefly removed by "skimming," so that only 3.05 parts remain in solution. From 
 100 parts of flesh of fowl, 8 parts were extracted, and of these 4.7 coagulated and 3.3 remained 
 dissolved in the soup. By boiling for a very long time, part of the albumin may be redissolved (Mulder). 
 The dissolved substances are : ( 1) Inorganic salts of the meat, of which 82.27 P er cer * 1 - P ass mto tne 
 soup ; the earthy phosphates chiefly remain in the cooked meat. (2) Kreatin, kreatinin, the inosin- 
 ates and lactates which give to broth or beef tea their stimulating qualities, and a small amount of 
 aromatic extractives. (3) Gelatin, more abundantly extracted from the flesh of young animal-!. 
 According to these facts, therefore, flesh, broth or beef-tea is a powerful stimulant, supplying muscle 
 with restoratives, but is not a food in the ordinary sense of the term, as kreatin (v. Voil) in general 
 leaves the body unchanged. The flesh, especially if it be cooked in a large mass, after the extrac- 
 tion of the broth is still available as a food. 
 
 Liebig's Extract of Meat is an extract of flesh evaporated to a thick syrupy consistence. It 
 contains no fat or gelatin, and is chiefly a solution of the extractives and salts of flesh. 
 
 [Extract of Fish. — A similar extract is now prepared from fish, and such extract has no fishy 
 flavor, but presents much the same appearance, odor, and properties as extract of flesh.] 
 
 234, VEGETABLE FOODS.— The nitrogenous constituents of plants 
 are not so easily absorbed as animal food (Subtler). Carbohydrates, starch, and 
 sugar are very completely absorbed, and even a not inconsiderable proportion of 
 cellulose may be digested ( Weiske, Konig). The more fats that are contained in 
 the vegetable food, the less are the carbohydrates digested and absorbed. 
 
 1. The cereals are most important vegetable foods; they contain proteids, 
 starch, salts, and water to 14 per cent. The nitrogenous glutin is most abundant 
 under the husk (Fig. 222, c). The use of whole meal containing the outer layers 
 of the grain is highly nutritive, but bread containing much bran is somewhat in- 
 digestible (Subtler). Their composition is the following : — 
 
 100 Parts of the Dry Meal contain 
 
 100 Parts of Ash contain 
 
 Of 
 
 Albumin. 
 
 Starch. 
 
 Red 
 
 Wheat. 
 
 
 White 
 Wheat. 
 
 Wheat .... 
 
 Rye 
 
 Barley .... 
 
 Maize 
 
 Rice 
 
 Buckwheat . . 
 
 16.52 <f„ 
 
 II.92 
 
 17.70 
 
 I3-65 
 7.40 
 6.8-IO.5 
 
 56.25 fo 
 60.91 
 
 38-3I 
 77-74 
 86.21 
 65.05 
 
 27.87 
 15-75 
 
 '■93 
 9.60 
 1.36 
 49-36 
 0.15 
 
 Potash 
 
 Soda 
 
 Lime 
 
 Magnesia .... 
 Iron oxide .... 
 Phosphoric Acid . 
 Silica 
 
 33.84 
 
 3-09 
 13-54 
 
 0.31 
 59-21 
 
 It is curious to observe that soda is absent from white wheat, its place being taken by other 
 alkalies. Rye contains more cellulose and dextrin than wheat, but less sugar; rye bread is usually 
 less porous. 
 
 In the preparation of bread the meal is kneaded with water until dough is formed, and to it 
 is added salt and yeast (Saccharomycetes cerevisiae). When placed in a warm oven, the proteids 
 of the meal begin to decompose and act as a ferment npon the swollen-up starch, which becomes in 
 part changed into sugar. The sugar is further decomposed into C0 2 and alcohol, the C0 2 forms 
 bubbles, which make the bread to "rise" and thus become spongy and porous. The alcohol is 
 driven off by the baking (200°), while much soluble dextrin is formed in the crust of the bread. 
 [But CO 2 may be set free within the dough by chemical means without yeast or leaven, thus forming 
 unfermented bread. This is done by mixing with the dough an alkaline carbonate and then 
 adding an acid. Baking powders consist of carbonate of soda and tartaric acid. In Dauglish's 
 process for aerated bread, the C0 2 is forced into water, and a dough is made with this water under 
 pressure, and when the dough is heated, the G0 2 expands and forms the spongy bread. Bread as 
 an article of food is deficient in N, while it is poor in fats and some salts. Hence the necessity for 
 using some form of fat with it (butter or bacon).] 
 
 [Oatmeal contains more nitrogenous substances (gliadin and glutin-casein) than wheaten flour, 
 but owing to the want of adhesive properties it cannot be made into bread. The amount of fat and 
 salts is large.] 
 
 2. The Pulses contain much albumin, especially vegetable casein or legumin : 
 together with starch, lecithin, cholesterin, and 9 to 19 per cent, water. Peas 
 
384 
 
 PULSES, POTATOES, FRUITS. 
 
 contain 18.02 proteids, and 38.81 starch; beans, 28.54, and 37.50; lentils, 29.31, 
 and 40, and more cellulose. Owing to the absence of glutin they do not form 
 dough, and bread cannot be prepared from them. On account of the large 
 amount of proteids which they contain, they are admirably adapted as food for 
 the poorer classes. 
 
 [3. The whole group of farinaceous substances used as "pudding stuffs," such as corn flour, 
 arrowroot, rice, hominy, are really very largely composed of starchy substance.] 
 
 4. Potatoes contain 70 to 81 per cent, water. In the fresh, juicy cellular 
 tissue, which has an acid reaction, from the presence of phosphoric, malic, and 
 hydrochloric acids, there is 16 to 23 per cent, of starch, 2.5 soluble albumin, 
 globulin (Zdller), and a trace of asparagin. The envelopes of the cells swell up 
 by boiling, and are changed into sugar and gums by dilute acids. The poisonous 
 solanin occurs in the sprouts. In 100 parts of potato ash, May found 46.96 potash, 
 2.41 sodium chloride, 8. n potassium chloride, 6.50 sulphuric acid derived from 
 burned proteids, 7.17 silica. 
 
 5. In Fruits the chief nutrient ingredients are sugar and salts; the organic 
 acids give them their characteristic taste ; the gelatinizing substance is the soluble 
 
 Fig. 222. 
 
 Microscopic characters of wheat (X 200). a, cells of the bran ; b, cells of thin cuticle ; c, glutin cells ; d, starch 
 
 cells ; B, wheat starch (X 350). 
 
 so-called pectin (C^H^Osj), which can be prepared artificially by boiling the 
 very insoluble pectose of unripe fruits and mulberries. 
 
 6. Green Vegetables are especially rich in ■ salts which resemble the 
 salts of the blood ; thus, dry salad contains 23 per cent, of salts which 
 closely resemble the salts of the blood. Of much less importance are the 
 starch, cell substance, dextrin, sugar, and the small amount of albumin which 
 they contain. 
 
 [Vegetables are chiefly useful for the salts they contain, while many of them are antiscorbutic. 
 Their value is attested by the serious defects of nutrition, such as scurvy, which result when they 
 are not supplied in the food. In Arctic expeditions and in the navy, lime juice is served out as an 
 antiscorbutic] 
 
 [Preserved Vegetables. — The dried and compressed vegetables of Messrs. Chollet & Company 
 are an excellent substitute for fresh vegetables, and are used largely in naval and military expe- 
 ditions.] 
 
 Utilization of Food. — As regards what percentage of the food swallowed is 
 actually absorbed, we know that, stated broadly, vegetable food is assimilated to 
 a much less extent than animal food in man. Fr. Hofmann gives the following 
 table as showing this : — 
 
CONDIMENTS, COFFEE, TEA, ALCOHOL. 
 
 385 
 
 Weight of Food. 
 
 Vegetable. 
 
 Animal. 
 
 Digested. 
 
 Undigested; 
 
 Digested. 
 
 Undigested. 
 
 Of ioo parts of solids 
 
 " ioo " albumin " 
 
 " ioo " fats or carbohyd . . 
 
 75-5 
 46.6 
 
 9°-3 
 
 24.5 
 
 53-4 
 
 9-7 
 
 89.9 
 81.2 
 96.9 
 
 II. I 
 
 18.8 
 
 3-'] 
 
 [The following table, abridged from Parkes, shows the composition of the chief articles of diet, and 
 is also used for calculating diet tables : — 
 
 Articles. 
 
 Water. 
 
 Proteids. 
 
 Fats. 
 
 Carbohydrates. 
 
 Salts. 
 
 Beefsteak 
 
 Smoked ham .... 
 
 White fish 
 
 Poultry 
 
 White wheaten bread 
 Wheat flour .... 
 
 Biscuit 
 
 Rice 
 
 Oatmeal 
 
 Maize 
 
 Macaroni 
 
 Arrow root .... 
 Peas (dry) 
 
 Carrots 
 
 Cabbage 
 
 Butter 
 
 Egg (tV for shell) . 
 
 Cheese 
 
 Milk (sp. gr. 1032) . 
 
 Cream 
 
 Skimmed milk . . . 
 Sugar 
 
 74-4 
 39-0 
 27.8 
 78.0 
 74.0 
 40.0 
 15.0 
 8.0 
 
 IOO 
 
 iS-o 
 13-5 
 131 
 '5-4 
 15.0 
 74.0 
 85.0 
 91.0 
 6.0 
 
 73-S 
 36.8 
 86.8 
 66.0 
 88.0 
 3-o 
 
 20.5 
 
 9.8 
 24.8 
 18.1 
 21.0 
 
 8.0 
 
 II.O 
 
 15.6 
 5.0 
 
 12.6 
 
 1 0.0 
 
 9.0 
 0.8 
 
 22.0 
 2.0 
 1.6 
 1.8 
 o-3 
 '3-5 
 33-5 
 4.0 
 2.7 
 4.0 
 
 3-5 
 48.9 
 
 36.5 
 2.9 
 
 3-8 
 
 «S 
 2.0 
 
 1-3 
 0.8 
 
 5-6 
 6.7 
 
 °-3 
 
 2.0 
 
 0.16 
 
 0.25 
 
 S-o 
 91.0 
 1 1.6 
 24-3 
 
 3-7 
 26 7 
 
 1.8 
 
 49.2 
 
 7°-3 
 73-4 
 83.2 
 63.0 
 
 64-5 
 76.8 
 
 83-3 
 53° 
 21.0 
 
 8.4 
 5-8 
 
 4.2 
 
 2.8 
 
 5-4 
 
 96.5 
 
 1.6 
 
 2-3 
 IO.I 
 
 1.0 
 
 1.2 
 
 i-3 
 
 '•7 
 
 i-7 
 
 °-5 
 
 3-° 
 
 1.4 
 
 0.8 
 
 0.27 
 
 2.4 
 
 1.0 
 
 1.0 
 
 0.7 
 2.7 
 
 1.0 
 
 5-4 
 0.7 
 1.8 
 0.8 
 o.S] 
 
 235. CONDIMENTS, COFFEE, TEA, ALCOHOL.— Some substances are used along 
 with food, not so much on account of their nutritive properties as on account of their stimulating! 
 effects and agreeable qualities, which are exerted partly upon the organ of taste and partly upon] 
 the nervous system. These are called condiments. 
 
 Coffee, Tea, and Chocolate are prepared as infusions of certain vegetables [the first of the 
 roasted berry, the second of the leaves, and the third of the seeds]. The chief active ingredients 
 are respectively caffein, thein (C g H 10 N 4 O 2 + H 2 0,) and theobromin (C 7 H 8 N 4 2 ), which are 
 regarded as alkaloids of the vegetable bases, and which have recently been prepared artificially 
 from xanthin (£. Fischer). [Guarana, or Brazilian cocoa, is made of the seeds ground into a 
 paste in the form of a sausage. Mate or Paraguay tea, the leaves of a species of holly, are used in 
 South America, and so also is the coca of the Andes (Erythroxylon Coca).] 
 
 These "alkaloids " occur as such in the plants containing them ; they behave like ammonia; 
 they have an alkaline reaction, and form crystalline salts with acids. All these vegetable bases act/ 1- 
 upon the nervous system; some more feebly (as the above), others more powerfully (quinine) ; some) 
 stimulate powerfully, or completely paralyze (morphia, atropin, strychnin, curarin, nicotin, mus- 
 carin). 
 
 Effects. — All these substances act on the nervous system; they quicken thought,) 
 accelerate movement, and stir one to greater activity. In these respects they re- 
 semble the stimulating extractives — kreatin and kreatinin — of beef tea. Coffee 
 contains about }i per cent, of caffein, part of which is only liberated by the act 
 of roasting. Tea has 6 per cent, of thein ; while green tea contains 1 per cent. V 
 
 ethereal oil, and black tea 
 •25 
 
 y 2 per cent. ; in green tea there is 18 per cent., in 
 
386 PREPARATION OF ALCOHOLIC DRINKS. 
 
 black, 15 per cent, tannin ; green tea yields about 46 per cent., and the black 
 scarcely 30 per cent, of extract. The inorganic salts present are also of im- 
 portance ; tea contains 3.03 per cent, of salts, and among these are soluble com- 
 pounds of iron, manganese, and soda salts. In coffee, which yields 3.41 per cent, 
 of ash, potash salts are most abundant ; in all three substances the other salts which 
 occur in the blood are also present. 
 
 Alcoholic Drinks owe their action chiefly to the alcohol which they contain. 
 The alcohol, when taken into the body, undergoes certain changes and produces 
 certain effects: (1) About 95 per cent, of it is oxidized chiefly into C0 2 and 
 H 2 0, so that it is so far a source of heat. As it undergoes this change very read- 
 ily, when taken to a certain extent, it may act as a substitute for the consumption 
 of the tissues of the body, especially when the amount of food is insufficient. 
 [Hammond found that when he lived on an insufficient amount of food, alcohol, 
 if given in a certain quantity, supplied the place of the deficiency of food, and he 
 even gained in weight. If, however, sufficient food was taken, alcohol was unnec- 
 essary. As it interferes with oxidation, and where there is a sufficient amount of 
 other food, in health, it is unnecessary, for dietetic reasons.] Small doses dimin- 
 ish the decomposition of the proteids to the extent of 6 to 7 per cent. Only a 
 very small part of the alcohol is excreted in the urine ; the odor of the breath is 
 not due to alcohol, but to other volatile substances mixed with it, e. g., fusel oil, 
 etc. (2) In small doses it excites, while in large doses it paralyzes the ner- 
 vous system. By its stimulating qualities it excites to greater action, which, 
 however, is followed by depression. (3) It diminishes the sensation of hunger. 
 (4) It excites the vascular system, accelerates the circulation, so that the muscles 
 and nerves are more active, owing to the greater supply of blood. It also gives rise 
 to a subjective feeling of warmth. In large doses, however, it paralyzes the ves- 
 sels, so that they dilate, and thus much heat is given off (§ 213, 7, § 227). The 
 action of the heart also becomes affected, the pulse becomes smaller, feebler, and 
 more rapid. In high altitudes the action of alcohol is greatly diminished, owing 
 to the diminished atmospheric pressure whereby it is rapidly given off from the 
 blood. 
 
 Alcohol in small doses is of great use in conditions of temporary want, and 
 where the food taken is insufficient in quantity. When alcohol is taken regularly, 
 more especially in large doses, it affects the nervous system, and undermines the 
 psychical and corporeal faculties, partly from the action of the impurities which it 
 may contain, such as fusel oil, which has a poisonous effect upon the nervous sys- 
 tem, partly by the direct effects, such as catarrh and inflammation of the digestive 
 organs, which it produces, and lastly, by its effect upon the normal metabolism. 
 
 [The action of alcohol in lowering the temperature, even in moderate doses, is most important. 
 By dilating the cutaneous vessels, it thus permits of the radiating of much heat from the blood. 
 When the action of alcohol is pushed too far — and especially when this is combined with the action 
 of great cold — its use is to be condemned.] 
 
 [Brunton has pointed out that, as regards its action on the nervous system, it seems to induce 
 progressive paralysis, affecting the nervous tissues " in the inverse order of their development, the 
 highest centres being affected first and the lowest last." The judgment is affected first, although 
 the imagination and " emotions maybe more than usually active." The motor centres and speech 
 are affected, then the cerebellum is influenced, and afterward the cord, while, by and by, the centres 
 essential to life are paralyzed, provided the dose be sufficiently large.] 
 
 Preparation.— Alcoholic drinks are prepared by the fermentation of various carbohydrates, 
 such as sugar derived from starch. The alcoholic fermentation, such as occurs in the manufacture 
 of beer, is caused by the development of the yeast plant, Saccharomycetes cerevisise ; while in 
 the fermentation of the grape (wine), S. ellipsoideus is the species present (Fig. 223). The yeast 
 takes the substances necessary for the maintenance of its organic processes directly from the mixture 
 of the sugar, viz., carbohydrates, proteids and salts, especially calcium and potassium phosphates 
 and magnesium sulphate. These substances undergo decomposition within the cells of the yeast 
 plant, which multiply during the process, and there are produced alcohol and C0 2 {\ 150), together 
 with glycerine (3.2 to 3.6 per cent.) and succinic acid (0.6 to 0.7 per cent.). Yeast is either added 
 intentionally or it reaches the mixture from the air, which always contains its spores. When yeast 
 is completely excluded, or if it be killed by boiling [or if its action be prevented by the presence of 
 
CONDIMENTS. 387 
 
 some germicide], the fermentation does not occur. The alcoholic fermentation is due to the vital 
 activity of a low organism (Schwann, Mitscherlich, Pasteur). 
 
 In the preparation of brandy, the starch of the grain or potatoes is first changed into sugar by 
 the action of diastase or maltin. Yeast is added, and fermentation thereby produced ; the mixture 
 is distilled at 78. 3 C. The fusel oil is prevented from mixing with the alcohol by passing the vapor 
 through heated charcoal. The distillate contains 50 to 55 per cent, of alcohol. 
 
 In the preparation of wine, the saccharine juice of the grape — the must — after being expressed 
 from the grapes, is exposed to the air at lo° to 15 C, and the yeast cells, which are floating about, 
 drop into it and excite fermentation, which lasts ten to fourteen days, when the yeast sinks to the 
 bottom. The clear wine is drawn off into casks, where it becomes turbid by undergoing an after- 
 fermentation, until the sugar is converted into alcohol and C0 2 , which is accompanied by the deposi- 
 tion of some yeast and tartar. If all the sugar is not decomposed — which occurs when there is not 
 sufficient nitrogenous matter present to nourish the yeast — a sweet wine is obtained. Wine contains 
 89 to 90 per cent, water, 7 to 8 per cent, alcohol, together with sethylic, propylic and butylic alcohol. 
 The red color of some wines is due to the coloring matter of the skin of the grapes, but if the skins 
 be removed before fermentation, red grapes yield white wine. When wine is stored, it develops a 
 fine flavor or bouquet. The characteristic vinous odor is due to cenanthic ether. The salts of 
 wine closely resemble the salts of the blood. 
 
 In the preparation of beer the grain is moistened, and allowed to germinate, when the tempera- 
 ture rises, and the starch (68 per cent, in barley) is changed into sugar. Thus, " malt " is formed, 
 
 Fig. 223. . 
 
 1, Isolated yeast "cells; 2, 3, yeast cells budding; 4, 5, so-called endogenous formation of cells; 6, sprouting and 
 
 formation of buds. 
 
 which is dried, and afterward pulverized, and extracted with water at 70 to 75 , the watery extract 
 being the " wort." Hops are added to the wort, and the whole is evaporated, when the proteids are 
 coagulated. Hops give beer its bitter taste, make it keep, while their tannic acid precipitates any 
 starch that may be present, and clarifies the wort. After being boiled, it is cooled rapidly (12 C. ) ; 
 yeast is added, and fermentation goes on rapidly and with considerable effervescence at 10° to 14 . 
 Beer contains 75 to 95 per cent, water; alcohol, 2 to 5 per cent, (porter and ale, to 8 per cent.) ; 
 C0 2 , 0.1 to 0.8 per cent.; sugar, 2 to 8 per cent.; gum, dextrin, 2 to 10 per cent.; the hops yield 
 traces of protein, fat, lactic acid, ammonia compounds, the salts of the grain and of the hops. In 
 the ash there is a great preponderance of phosphoric acid and potash, both of which are of great 
 importance for the formation of blood. In too parts of ash there are 40.8 potash-, 20.0 phosphorus, 
 magnesium phosphate, 20, calcium phosphate, 2.6, silica, 16.6 per cent. The formation of blood, 
 muscle and other tissues from the consumption of beer is due to the phosphoric acid and potash, 
 while if too much be taken, the potash produces fatigue. 
 
 Condiments are taken with food, partly on account of their taste, and partly 
 because they excite secretion. Common salt, in a certain sense, is a condiment. 
 We may also include many substances of unknown constitution which act upon 
 the gustatory organs, e. g. , substances in the crust of bread [dextrin] and in meat 
 which has been roasted. 
 
PHENOMENA AND LAWS OF METABOLISM. 
 
 236. EQUILIBRIUM OF THE METABOLISM.— By this term is 
 meant that, under normal physiological conditions, just as much material is absorbed 
 and assimilated from the food as is removed from the body, by the excretory 
 I organs, in the form of effete or end products, the result of the retrogressive tissue 
 changes. The income must always balance the expenditure ; wherever a tissue is 
 used up, it must be replaced by the formation of new tissue. During the period 
 of growth, the increase of the body corresponds to a certain increase of forma- 
 tion, whereby the metabolism of the growing parts of the body is 2.5 to 6.3 times 
 greater than that of the parts already formed (Crusius). Conversely, during 
 senile decay, there is an excess of expenditure from the body. 
 
 Methods. — The normal equilibrium of the metabolism of the body is investigated — (1) By 
 determining chemically that the sum of all the substances passing into the body is equal to the sum 
 of all the substances given off from it. Thus the C, H, N, O, salts and water of the food, and the 
 O inspired, must be equal to the C, N, H, O, salts and water given off in the excreta (urine, faeces, 
 air expired, water excreted). (2) The physiological equilibrium is determined empirically by 
 observing that the body retains its normal weight with a given diet ; so that, by simply weighing a 
 person, a physician is enabled to determine exactly the state of convalescence of his patient. The 
 tedious process of making an elementary analysis of the metabolic substances was first under- 
 taken in the Munich School by v. Bischoff, v. Voit, v. Pettenkofer, and others. 
 
 Circulation of C. — In the circulation of materials the total amount of C taken 
 in the food, if the metabolism be in a condition of physiological equilibrium, 
 must be equaled by the C in the C0 2 given off by the lungs and skin (90 per 
 cent.), together with the relatively small amount of C in the organic excreta of 
 the urine and faeces (10 per cent.). 
 
 Circulation of N. — Nearly all the N taken in with the food is excreted within 
 twenty-four hours in the form of urea. A very small amount of nitrogenous 
 matter is excreted in the faeces, while the other nitrogenous urinary constituents 
 (uric acid, kreatinin, etc.) represent about 2 per cent, of N. A trace of the N 
 is given off by the breath (§ 124), and a minute proportion in combination, 
 in the epidermal scales (50 milligrammes daily in the hair and nails), and 
 in the sweat. 
 
 Deficit of N — That nearly all the N taken in the food reappears in the urine 
 and faeces, as was stated by v. Voit to be the case in the carnivora, by Henneberg, 
 Stohman, and Grouven in the herbivora, and v. Ranke in man, is contradicted 
 partly by old and partly by new observations, which go to show that the whole of 
 the N cannot be recovered from these excretions, but on the contrary there is a 
 considerable deficit. 
 
 According to Leo, only 0.55 per cent, of the albumin transformed within the body (assuming 15 
 per cent. N. in albumin) gives off its N in the form of gaseous N (according to Seegen and Nowak 
 12 times more). In every exact analysis of the metabolism of N this gaseous excretion of N must 
 be taken into account. 
 
 The Excretion of N after food does not take place regularly from hour to hour, but it increases 
 at once and distinctly, reaches its maximum in five to six hours, and then gradually falls. The same 
 is true of the excretion of S and P ; but in these cases the maximum of excretion is reached at the 
 fourth hour. When fat is added to a diet of flesh, the excretion of N and S is uniformly distributed 
 over the individual hours of the day (v. Voit and Feder). 
 
 The nitrogenous constituents in the body during metabolism become poorer in C, and richer in N 
 and O. Thus in albumin to I atom of N there are 4 atoms C; in gelatin, 3^ C; in glycocoll, 
 2 C; in kreatin, 1% C; in uric acid, \% C; in allantoin, 1 C; in urea, only "| atom of C. 
 
 388 
 
EQUILIBRIUM OF THE METABOLISM. 389 
 
 The H leaves the body chiefly in the form of water — a part, however, is in the 
 combination in other excreta ; the O is chiefly excreted as C0 2 and water ; a little 
 is given off in combination in other excreta ; water is given off by evaporation 
 from the lungs and skin, and also in the urine and feces. As H is oxidized to 
 form H 2 0, more water is excreted than is taken in. With regard to the salts, 
 most of the readily soluble salts are given off by the urine ; the less soluble salts, 
 especially those of potash, and the insoluble salts, in the feces ; while others e. g., 
 common salt, are given off in the sweat. Of the sulphur of albumin, about one- 
 half is excreted in the sulphur compounds in the urine, and the other half in the 
 feces (taurin), and in the epidermal tissues. 
 
 Every organism has a minimum and a maximum limit of metabolism, 
 according to the amount of work done by the body, and its weight. If less food 
 be given than is necessary to maintain the former, the body loses weight ; while, 
 if more be given after the maximum limit is reached, the food so given is not 
 absorbed, but remains as a floating balance, and is given off with the feces. When 
 food is liberally supplied and the weight increases, of course the minimum limit 
 rises; hence, during the process of "feeding" or "fattening," the amount of 
 food necessary is very much greater than in poorly fed animals, for the same 
 increase of the body weight. By continuing the process, a condition is at last 
 reached, in which the digestive organs are just sufficient to maintain the existing 
 condition, but cannot act so as to admit of new additions being made to the body 
 weight {v. Bischoff, v. Voit, v. Pettenkofer). 
 
 By the term " luxus consumption" is meant the direct combustion or oxi- 
 dation of the superfluous food stuffs absorbed into the blood. This, however, does 
 not exist ; on the contrary, the material in the juices is always being used for 
 building up the tissues. The albumin found in the fluids which everywhere per- 
 meate the tissues has been called " circulating albumin," and according to 
 v. Voit it undergoes decomposition sooner than the organized " organic albu- 
 min " which forms an integral part of the tissues. 
 
 [Liebig taught that the nitrogenous metabolism of the body depended on a corresponding decom- 
 position of the proteids of the organs, so that the proteids in the food supplied the place of the 
 proteids of the organs thus used up. He called the proteids " plastic foods " or " tissue for- 
 mers," while he regarded the fats and carbohydrates as respiratory foods," as he supposed that 
 they alone were concerned in the evolution of heat. As a matter of fact, experiment proved that 
 the N metabolism is to a large extent independent of the proteids of the food. The luxus-con- 
 sumption theory was invented to explain this. It simply means, that proteids taken with the food 
 not only replace the amount of proteids which have been decomposed during the activiiy of organs 
 and tissues, but any excess is immediately consumed without being converted into tissue, and thus 
 this surplus amount giving rise to heat, being oxidized, to a certain extent it replaced the fats and 
 carbohydrates. But Voit showed that nitrogenous metabolism is not influenced by the activity of 
 the organism, and he proved that in ordinary conditions only a small amount of the organic jilbumin, 
 i. e., that composing tissues and organs, undergoes decomposition, while, owing to the action of the 
 cellular elements of the tissues, a large amount of the circulating albumin is split up, so that under 
 ordinary conditions the organic albumin is comparatively stable. This he demonstrated from a 
 comparison of the urea excreted, for the urea may be taken as an index of the N metabolism 
 in well-fed, fasting, and starving animals. But in certain pathological conditions the organic 
 albumin may undergo rapid change, having become less stable, as in fevers, and poisoning 
 with phosphorus.] 
 
 According to v. Voit only i per cent, of the organic albumin present in the 
 body, while 70 per cent, of the circulating albumin, is transferred in twenty-four 
 hours. 
 
 Quality and Quantity of the Income in a Healthy Adult. — As far as 
 his organization is concerned, man belongs to the omnivorous animals, /. e., 
 those that can live upon a mixed diet. 
 
 For an adequate diet man requires for his existence and to maintain health a 
 mixture of the following four chief groups of food stuffs, along with the necessary 
 relishes ; none of them must be absent from the food for any length of time. 
 They are : — 
 
390 REQUISITES FOR A PERFECT DIET. 
 
 i. Water — for an adult, in his food and drink, 2700 to 2800 grms. [70 to 90 
 oz.] daily (§ 229 and § 247, 1). 
 
 [Thirst. — The needs of the economy for water are expressed by the sensation of thirst. The 
 sensation of heat and dryness may be confined to the tongue, mouth, and fauces, and, indeed, may 
 be excited by inhaling dry air. This local thirst may be allayed by swallowing water or by eating 
 substances which excite the secretion of saliva. More frequently, however, the sensation is the 
 expression of a general condition indicating the diminution of water in the tissues ; or it may be due 
 to excess of saline matters in the blood. In some diseases this sensation is very intense, e.g., dia- 
 betes, and there seems to be a thirst centre in the brain (Notknagel). If water be injected into the 
 blood vessels, or stomach, both the general and local thirst are abolished, even although no water 
 enters the mouth. In some diseased conditions the sensation of thirst is not perceived, owing to 
 the diminution of the excitability of the perceptive centre, and in some cases excessive thirst is 
 complained of even although the body does not seem to be unduly deficient in fluids.] 
 
 2. Inorganic Substances are the integral part of all tissues, and without 
 them the tissues cannot be formed. They occur in ordinary food. The addition 
 of too much salt increases the consumption of water, and this in turn increases 
 the transformation of N in the body (Weiske). If an animal be deprived of salts, 
 nutrition is interfered with ; food deprived of its lime affects the formation of the 
 bones ; deprival of common salts causes albuminuria (§ 247, A, III). The alkaline 
 salts serve to neutralize the sulphuric acid formed by the oxidation of the sulphur 
 of the proteids (E. Salkowski). Iron, which is so essential for the formation of 
 blood, exists in animals and plants in combination with complex organic bodies 
 {Bunge). 
 
 [The uses of mineral salts are referred to in \ 247, A. Salts form an essential ingredient in 
 soups and broth. Some salts exist in combination with the organized tissues, while others are 
 merely dissolved in the fluids. Forster thinks that it is the latter which are chiefly excreted.] 
 
 Only in times of famine is man driven to eat large quantities of inorganic substances, to extract 
 the organic matter mixed therewith. A. v. Humboldt states, in regard to the inhabitants of the 
 Orinoco, that they eat a kind of earth which contains innumerable infusoria. 
 
 3. At least one animal or vegetable albuminous body or proteid (§§ 248, 250). 
 The proteids are required to replace the used-up nitrogenous tissues, e. g., for 
 muscles. They contain 15.4 to 16.5 per cent. N. 
 
 The proteidsare in blood = 20.56 per cent.; muscles, 19.9 per cent. ; liver, 11.74 per cent. ; 
 brain, 8.63 per cent.; blood plasma, 7.5 per cent.; milk, 3.94 per cent.; lymph, 2.46 per cent. 
 According to Pfliiger and Bohland, a youth of full stature, and 62 kilos. [136 H>s.], decomposes 
 89.9 grms. of albumin daily. 
 
 Asparagin, in combination with gelatin, can replace albumin in the food (Weiske), while aspara- 
 gin alone limits the decomposition of albumin in herbivora but not in carnivora (J. Muni). 
 Ammoniacal salts, glycocoll, sarkosin, and benzamid, increase the amount of albumin in the body. 
 
 4. At least one fat (§ 251), or a digestible carbohydrate (§ 252). These 
 chiefly serve to replace the transformed fats and non-nitrogenous constituents. 
 Owing to the large amount of C which they contain, when they undergo oxida- 
 tion, they form the chief source of the heat of the body (§ 206). Fats and car- 
 bohydrates may replace each other in the food, and in inverse proportion too, 
 corresponding to the amount of C which each contains. As far as the mere evo- 
 lution of heat is concerned, 100 parts of fat = 256 of grape sugar — 234 of cane 
 sugar = 221 of dry starch {Rubner). A man consumes 210 grms. fat daily. 
 (v. Voit and v. Pettenkofer). According to v. Voit, in the economy 175 parts of 
 starch by weight are equal to 1 00 parts of fat: 
 
 [5. Every proper diet ought to have a certain degree of sapidity or flavor. 
 The substances which give this are not useful in the evolution of energy or build- 
 ing, up the tissues, but they stimulate the nervous system and excite secretion. 
 They are called " Genussmittel " (means of enjoying food) by the Germans, but 
 we have no exact equivalent for this word in English, though the articles them- 
 selves are included under our expression "condiments." These substances are 
 the aromatic matter in roast meat (osmasoine), tea, vinegar, salt, mustard, pepper, 
 etc.] 
 
PROPORTION OF FOODS. 
 
 391 
 
 [Condition of Diet for Health. — In an adequate diet, not only (i) should 
 the total quantity be sufficient and not more than sufficient, but (2) the constitu- 
 ents should exist in proper proportions, (3) be digestible, and (4) the whole 
 should be in good condition, wholesome, and not adulterated with any substance 
 prejudicial to health.] 
 
 Fig. 224. 
 explanation of the signs. 
 
 Water. 
 
 Beef. 
 
 Pork. 
 
 Fowl. 
 
 Fish. 
 
 Egg. 
 
 Cow's milk. 
 
 Human milk. 
 
 c 
 
 Water. 
 
 Wheaten bread 
 
 Proteids. 
 
 Albuminoids. N-free org. bodies. 
 
 62 
 
 55 
 
 73 
 
 76 
 
 73,5 
 
 8fi 
 
 89 
 
 Salts. 
 
 <H,3 
 
 n 
 
 ■ < 
 
 Animal Foods. 
 EXPLANATION OF THE SIGNS. 
 
 ^H|||lll'» l liilililliliiilillllllPll^.^'-^gS 
 
 Proteids. Digestible. Non-digestible. Salts. 
 
 N-free organic bodies. 
 
 I 
 
 Rice. 
 
 Potatoes. 
 White turnip. 
 Cauliflower. 
 Beer. 
 
 75 
 
 90,5 
 
 ao 
 
 30 
 
 Ulk -1 
 
 ma- 
 
 Vegetable Foods. 
 
 Relative Proportion. — With regard to the relative proportions of the various 
 kinds of food which ought to be taken, experience has shown that the diet best 
 suited for the body must contain 1 part of nitrogenous foods to j^A or, at most, 4*4 
 of the non-nitrogenous. Looking at ordinary foods from this point of view, we see 
 how far they correspond to this requirement, and how several substances may be 
 combined to produce a satisfactory diet. 
 
392 
 
 DAILY QUANTITY OF FOOD REQUIRED. 
 
 Nit. 
 i. Veal 10 
 
 2. Hare's flesh . . . io 
 
 3. Beef 10 
 
 4. Lentils 10 
 
 5. Beans 10 
 
 6. Peas 10 
 
 Non- 
 Nit. 
 I 
 
 2 
 
 17 
 21 
 22 
 23 
 
 Mutton . . 
 Pork . . . 
 Cow's milk 
 
 Human milk 
 
 Nit. 
 . IO 
 . 10 
 , 10 
 . 10 
 
 9- 
 10. 
 
 11. Whea ten flour . 10 
 
 12. Oatmeal . . . . 10 
 
 Non- 
 Nit. 
 27 
 
 3° 
 30 
 
 37 
 46 
 5o 
 
 13. Rye meal , . 
 
 14. Barley meal . 
 
 15. White potatoes 
 
 16. Blue " 
 
 17. Rice . . . . 
 
 Nit. 
 . IO 
 . IO 
 , 10 
 . 10 
 . 10 
 
 18. Buckwheat meal. 10 
 
 Non- 
 Nit. 
 
 57 
 57 
 86 
 
 "5 
 123 
 130 
 
 An examination of this table shows that, in addition to human milk, wheat flour has the right 
 proportion of nitrogenous to non-nitrogenous substances. A man who tries to nourish himself on 
 beef alone, commits as great a mistake as one who would feed himself with potatoes alone. 
 Experience has taught people that man may live upon milk and eggs, but that in addition to flesh 
 we must eat bread or potatoes, while pulses require fat or bacon. 
 
 Effect of Cold. — The diet varies with the climate and with the season of the year. As the 
 organism must produce more heat in cold latitudes, the inhabitants of northern climates must eat 
 more non-nitrogenous foods, such as fats and sugar or starches, which, on account of the large 
 amount of C they contain, are admirably adapted for producing heat ($ 214, I, 4). 
 
 The graphic representation of the composition of foods (Fig. 224), taken from 
 Fick, shows at once the relative proportions of the most important food stuffs, 
 and how they vary from the standard of 1 nitrogenous to 3^ or 4j^ non-nitro- 
 genous. 
 
 The absolute amount of food stuffs required by an adult in twenty-four hours 
 depends upon a variety of conditions. As the food represents the chemical 
 reservoir of potential energy, from which the kinetic energy (in its various forms) 
 and the heat of the body are obtained, the absolute amount of food must be 
 increased when the body loses more heat, as in winter, and when more muscular 
 activity (work) is accomplished. As a general rule, an adult requires daily 130 
 grammes proteids, 84 grammes fats, 404 grammes carbohydrates. 
 
 The following tables express the mean of numerous single observations : — 
 
 A Healthy Adult Requires in 24 Hours, of Water-free solids — 
 
 Food in Grammes. 
 
 At Rest. 
 {Play/air.) 
 
 Moderate Work. 
 {Malesckott.) 
 
 Laborious Work. 
 
 {Play/air.) 
 
 (v. Pettenkofer 
 andv. Voit.) 
 
 Fats 
 
 70.87 
 
 28.35 
 
 340.20 
 
 14.00 
 
 130 
 84 
 
 404 
 3° 
 
 I55-92 
 70.87 
 
 567-50 
 40.00 
 
 137 
 117 
 
 352 
 40 
 
 Carbohydrates (Sugar, Starch, etc.) . 
 Salts 
 
 [When we record these numbers in ounces we get the following results as 
 water-free solids required by any average man (JParkes) : — 
 
 
 At Rest. 
 
 Ordinary Work. 
 
 Laborious Work. 
 
 Proteids 
 
 Fats . • 
 
 Salts 
 
 2-5 
 I.O 
 
 12.0 
 
 0.5 
 
 4.6 
 
 3-0 
 
 14.4 
 
 1.0 
 
 6 to 7 
 
 3-5*0 4 5 
 16 to 18 
 1.2 to 1.5 
 
 Total water-free food 
 
 16.0 
 
 23.0 
 
 26.7 to 31.0 
 
 During ordinary work the proportion is about : — 
 
 Proteids, 1 : fats, 0.6: carbohydrates, 3.0, 
 i.e., 1 Nitrogenous to 3.6 non-nitrogenous.] 
 
 [In a diet for ordinary work (23 oz. of dry solids) a man takes about -j-J-^ part of 
 his own weight daily; ordinary food, however, as it is consumed, contains between 
 
DAILY QUANTITY OF FOOD REQUIRED. 
 
 393 
 
 50 and 60 per cent, of water ; if we add this proportion of water to the actually 
 dry food we get 48 to 60 oz. of ordinary food (exclusive of liquids). But we 
 consume 50 to 80 oz. of water in some liquid form, making the total amount of 
 water 70 to 90 oz. (Parkes).~\ 
 
 In an analogous example from Vierordt, the elementary substances in the food are given (J 215, 
 B), and compared with the income and expenditure. 
 
 An Adult doing a Moderate Amount of Work takes in : — 
 
 
 C. 
 
 H. 
 
 N. 
 
 0. 
 
 90 " fats, " 
 
 64.18 
 
 70.20 
 
 146.82 
 
 8.60 
 IO.26 
 20.33 
 
 18.88 
 
 :: 
 
 28.34 
 
 9-54 
 162.85 
 
 330 " starch, " 
 
 
 281.20 
 
 39-19 
 
 18.88 
 
 200.73 
 
 Add 744. 1 1 grm. O from the air by respiration. 
 " 2818 " H 2 0. 
 
 " 32 " Inorganic compounds (salts). 
 
 The whole is equal to 3^- kilos [7 R)3.], i. e., about -fa of the body weight ; so 
 that about 6 per cent, of the water, about 6 per cent, of the fat, about 1 per cent, 
 albumin, and about 0.4 per cent, of the salts of the body are daily transformed 
 within the organism. 
 
 An Adult doing Moderate Work gives off, in grammes: — 
 
 By respiration 
 Perspiration . 
 Urine . . . 
 Faeces . . . 
 
 Water. 
 
 c. 
 
 H. 
 
 N. 
 
 0. 
 
 330 
 
 660 
 
 17OO 
 
 128 
 
 248.8 
 
 2.0 
 
 9.8 
 
 20.0 
 
 3-3 
 
 3-o 
 
 15.8 
 
 3-° 
 
 651.15 
 
 7.2 
 
 11. 1 
 
 12.0 
 
 28l8 
 
 201.2 
 
 6.3 
 
 18.8 
 
 681.45 
 
 Add to this (besides 2818 grammes water, as drink) 296 grammes water formed in the body by 
 the oxidation of H. These 296 grammes of water contain 3289 grammes H, and 263.41 grammes 
 O ; 26 grammes of salts are given .dff in the urine, and 6 by the faeces. 
 
 Effect of Age. — The investigations of the Munich School have shown that the 
 following numbers represent the minimum amount of food necessary for dif- 
 ferent ages : — 
 
 Age. 
 
 Child until 1% years . . . , 
 
 " from six to fifteen years 
 
 Man (moderate work) . . . . 
 
 Woman 
 
 Old man 
 
 Old woman , 
 
 Nitrogenous. 
 
 20—36 grms. 
 
 70-80 " 
 
 1 18 " 
 
 92 " 
 
 100 " 
 
 80 " 
 
 Fat. 
 
 30-45 grms. 
 
 37-5° " 
 56 " 
 
 44 " 
 
 68 
 
 50 ' " 
 
 Carbohydrates. 
 
 60-90 grms. 
 250-400 " 
 500 " 
 400 " 
 
 35° " 
 260 " 
 
 [Not only do muscular movements and age influence the amount of food taken, but climate and 
 individual peculiarities, such as size and the activity of certain organs, also affect it.] 
 
 Small animals have a more lively metabolism than large ones (Regnault and Reisef). In small 
 animals the decomposition of albumin per unit weight of body is greater than in large animals 
 [v. Voit). Small animals, as a rule, consume more proteids than larger ones, because they generally 
 have less bodily fat (Subtler). 
 
394 
 
 METABOLISM DURING HUNGER AND STARVATION. 
 
 Relation of N to C. — In most of the ordinary articles of diet, nitrogenous 
 and non-nitrogenous substances are present, but in very varying proportion, in 
 the different foods. Man requires that these shall be in the proportion of i : 3^ 
 to 1 : 4^. 
 
 If food be taken in which this proportion is not observed, in order to obtain 
 the necessary amount of that substance which is contained in too small proportion 
 in his food, he must consume far too much food. Moleschott finds that a person, 
 in order to obtain the 130 grammes of proteids necessary, must use 
 
 Cheese 338 grms. 
 
 Lentils 491 " 
 
 Peas 582 " 
 
 Beef 614 grms. 
 
 Eggs 968 " 
 
 Wheat bread . . 1444 " 
 
 Rice 2562 grms. 
 
 Rye bread . . . 2875 " 
 Potatoes . . . 10,000 " 
 
 provided he were to take only one of these substances as food ; so that it is per- 
 fectly, obvious that, if a workman were to live on potatoes alone, in order to get 
 the necessary amount of N, he would have to consume an altogether preposterous 
 amount of this kind of food. 
 
 To obtain the 448 grammes of carbohydrates, or the equivalent amount of 
 fat necessary to support him, a man must eat 
 
 Peas 819 grms. 
 
 Eggs 902 " 
 
 Rye bread .... 930 " 
 
 Rice 572 grms. 
 
 Wheat bread . . . 626 " 
 Lentils 806 " 
 
 Cheese 201 1 grms. 
 
 Potatoes .... 2039 " 
 Beef 2261 " 
 
 so that if he were to live upon cheese or flesh alone, he would require to eat an 
 enormous amount of these substances. 
 
 In the case of the herbivora, the proportion of nitrogenous to non-nitrogenous food necessary is 
 I of the former to 8 or 9 parts of the latter. 
 
 237. METABOLISM DURING HUNGER AND STARVATION. 
 
 — If a warm-blooded animal be deprived of all food, it must, in order to 
 maintain the temperature of its body and to produce the necessary amount of me- 
 chanical work, transform and utilize the amount of potential energy of the con- 
 stituents of its own body. The result is that its body weight diminishes from 
 day to day, until death occurs from starvation. 
 
 The following table, from Bidder and Schmidt, shows the amounts of the different excreta in the 
 case of a starved cat : — 
 
 Day. 
 
 Body 
 Weight. 
 
 Water 
 taken. 
 
 Urine. 
 
 Urea. 
 
 Inorganic 
 
 Substances 
 in Urine. 
 
 Dry 
 Faeces. 
 
 Expired 
 C. 
 
 Water in 
 
 Urine 
 
 and Faeces. 
 
 I. 
 
 2464 
 
 
 98 
 
 7-9 
 
 i-3 
 
 1.2 
 
 13-9 
 
 91.4 
 
 2. 
 
 2297 
 
 II.5 
 
 54 
 
 5-3 
 
 0.8 
 
 1.2 
 
 . iz-9 
 
 50.5 
 
 3- 
 
 22IO 
 
 
 45 
 
 4.2 
 
 °-7 
 
 I.I 
 
 12 
 
 42.9 
 
 4- 
 
 2172 
 
 68.2 
 
 45 
 
 3-8 
 
 0.7 
 
 I.I 
 
 12.3 
 
 43 
 
 5- 
 
 2129 
 
 
 55 
 
 4-7 
 
 0.7 
 
 1-7 
 
 1 1.9 
 
 54-1 
 
 6. 
 
 2024 
 
 
 44 
 
 4-3 
 
 0.6 
 
 0.6 
 
 11.6 
 
 41. 1 
 
 7- 
 
 1946 
 
 
 40 
 
 3-8 
 
 °-5 
 
 0.7 
 
 11 
 
 37-5 
 
 8. 
 
 1873 
 
 
 42 
 
 3-9 
 
 0.6 
 
 I.I 
 
 10.6 
 
 40 
 
 9- 
 
 1782 
 
 15-2 
 
 42 
 
 4 
 
 0.5 
 
 i-7 
 
 10.6 
 
 41.4 
 
 10. 
 
 1717 
 
 
 35 
 
 3-3 
 
 0.4 
 
 x v3 
 
 10.5 
 
 34 
 
 11. 
 
 l69S 
 
 4 
 
 32 
 
 2.9 
 
 o-5 
 
 1.1 
 
 10.2 
 
 3°-9 
 
 12. 
 
 1634 
 
 22.5 
 
 3° 
 
 2.7 
 
 0.4 
 
 1.1 
 
 10.3 
 
 29.6 
 
 13. 
 
 I570 
 
 7-i 
 
 40 
 
 34 
 
 °-5 
 
 0.4 
 
 IO.I 
 
 36.6 
 
 14. 
 
 1518 
 
 3 
 
 41 
 
 3-4 
 
 o-5 
 
 o-3 
 
 9-7 
 
 38 
 
 IS- 
 
 1434 
 
 
 41 
 
 2.9 
 
 0.4 
 
 o-3 
 
 9-4 
 
 38-4 
 
 16. 
 
 1389 
 
 
 48 
 
 3 
 
 0.4 
 
 0.2 
 
 8.8 
 
 45-5 
 
 17- 
 
 I33S 
 
 
 28 
 
 1.6 
 
 0.2 
 
 o-3 
 
 7-8 
 
 26.6 
 
 i8.f 
 
 1267 
 
 
 «3 
 
 0.7 
 
 O.I 
 
 o-3 
 
 6.1 
 
 12.9 
 
 
 -1 197 
 
 I3I-S 
 
 775 
 
 65-9 
 
 9.8 
 
 15-8 
 
 190.8 
 
 7374 
 
LOSS OF WEIGHT OF ORGANS DURING STARVATION. 395 
 
 The cat lost 1197 grms. in weight before it died, and this amount is apportioned 
 in the following way: 204.43 grms. ( = 17.01 per cent.) loss of albumin; 
 132.75 grms. (=11.05 P er cent.) loss of fat ; 863.82 grms. loss of water ( = 
 71.91 per cent, of the total body weight). 
 
 Methods. — In order to investigate the condition of inanition it is necessary — (1) to weigh the 
 animal daily ; (2) to estimate daily all the C and N given off from the body in the faeces, urine and 
 expired air. The N and C, of course, can only be obtained from the decomposition of tissues con- 
 taining them. . 
 
 Among the general phenomena of inanition, it is found that strong, well-nourished dogs die 
 after 4 weeks, man after 21-24 days {Moleschotl) — (6 melancholies who took water died after 41 \ 
 days) ; small mammals and birds, 9 days, and frogso months. Vigorous adults die when they ) 
 lose -fij of their body weight, but ynung individuals diernuch sooner than adults. The symptoms 
 are obvious : The mouth is dry, the walls of the alimentary canal become thin, and the digestive 
 secretions cease to be formed ; pulse beats and respirations are fewer; urine very acid from the 
 presence of an increased amount of sulphuric and phosphoric acids, while the chlorine compounds 
 rapidly diminish and almost disappear. The blood contains less water and the plasma less albumin, 
 the gall bladder is distended, which indicates a continuous decomposition of blood corpuscles within 
 the liver. The liver is small and very dark-colored, the muscles are very brittle and dry, so that 
 there is great muscular weakness, and death occurs, with the signs of great depression and coma. 
 The relations of the metabolism are given in the foregoing table, the diminution in the excretion of 
 urea is much greater than that of C0 2 , which is due to a larger amount of fats than proteids being 
 decomposed. 
 
 According to the calculation, there is daily a tolerably constant amount of fat 
 used up, while, as the starvation continues, the proteids are decomposed in much 
 smaller amounts from day to day, although the drinking of water accelerates their 
 decomposition. .The excretion of C0 2 , therefore, falls more slowly than the total 
 body weight, so that the unit weight of the living animal from day to day may 
 even show an increased production of C0 2 . The amount of O consumed depends, 
 of course, upon the oxidation of proteids (which require less O), and of fats 
 (which require more O). • 
 
 According to D. Finkler, starving animals consume nearly as much O as well-nourished animals, 
 so that the energy of oxidation is scarcely altered during inanition. Corresponding to this, the tem- 
 perature of a starving animal is the same as normal. The respiratory quotient ($ 124) then falls 
 from 0.9 to 0.7, and the excretion of CO z diminishes more rapidly than the consumption of O. It 
 would be wrong, however, to conclude, from the diminished excretion of C0 2 , that the oxidation 
 also was diminished, as the simultaneous consumption of O is the only guide to the energy of the 
 metabolism. As starving animals use up their own flesh and fat, they form less C0 2 than well- 
 nourished animals, which oxidize carbohydrates chiefly. 
 
 Loss of Weight of Organs. — It is of importance to determine to what extent 
 the individual organs and tissues lose weight ; some undergo simple loss of weight, 
 e.g., the bones, the fat undergoes very considerable and rapid decomposition, 
 while other organs, as the heart, undergo little change, because they seem to be 
 able to nourish themselves from the transformation products of other tissues. 
 
 A starving cat, according to v. Voit, lost — 
 
 Per cent. Per cent, of 
 
 originally the total loss of 
 
 present. body weight. 
 
 1. Fat 97 26.2 
 
 2. Spleen .... 66.7 0.6 
 3- Liver 53.7 4.8 
 
 4. Testicles . . . 40.0 0.1 
 
 5. Muscles .... 30.5 42.2 
 
 6. Blood 27.0 3.7 
 
 7. Kidneys .... 25.9 0.6 
 
 8. Skin 20.6 8.8 
 
 9. Intestine . . . 18.0 2 o 
 
 There is a very important difference according as the animals before inanition 
 have been fed freely on flesh and fat [z. e., if they have a surplus store of food 
 within themselves], or as they have merely had a subsistence diet. Well-fed ani- 
 mals lose weight much more rapidly during the first few days than on the later 
 
 10. 
 II. 
 
 Per cent. 
 
 originally 
 present. 
 Lungs .... 17.7 
 Pancreas . . . 17.0 
 
 Per cent, of 
 
 the total loss of 
 
 body weight. 
 
 °-3 
 0.1 
 
 12. 
 
 Bones .... 13.9 
 Central Nerv- 
 
 5-4 
 
 14. 
 
 ous System . 3.2 
 Heart .... 2.6 
 
 O.I 
 
 0.02 
 
 15- 
 
 Total loss of 
 the rest of 
 
 
 
 the body . . 36.8 
 
 S-o 
 
396 METABOLISM OF PEPTONES. 
 
 days. v. Voit thinks that the albumin derived from the excess of food occurs in 
 a state of loose combination in the body as " circulating " or " storage albumin," 
 so that during hunger it must decompose more readily and to a greater extent than 
 the " organic albumin," which forms an integral part of the tissues (§ 236). 
 Further, in fat individuals, the decomposition of fat is much greater than in 
 slender persons. 
 
 238. METABOLISM ON A PURELY FLESH DIET— ALBU- 
 MIN OR GELATIN, PROTEID METABOLISM.— A man is not able 
 to maintain his metabolism in equilibrium on a purely flesh diet ; if he were com- 
 pelled to live on such a diet, he would succumb. The reason is obvious. In beef, 
 the proportion of nitrogenous to non-nitrogenous elementary constituents of food 
 is 1 : 1. 7 (p. 392). A healthy person excretes 280 grammes [8 to 90Z.] of carbon, 
 in the form of C0 2 , in the expired air, and in the urine and faeces. If a man is 
 to obtain 280 grammes C from a flesh diet, he must consume — digest and assimilate 
 — more than 2 kilos. [4.4 lbs.] of beef in twenty- four hours. But our digestive 
 organs are unequal to this task for any length of time. The person is soon 
 obliged to take less beef, which would necessitate the using of his own tissues, at 
 first the fatty parts and afterward the proteid substances. 
 
 A carnivorous animal (dog), whose digestive apparatus, being specially adapted for the diges- 
 tion of flesh, has a short intestine and powerfully active digestive fluids, can only maintain its meta- 
 bolism in a state of equilibrium when fed on a flesh diet free from fat, provided its body is already 
 well supplied with fat, and is muscular. It consumes ^ to fo part of the weight of its body in 
 flesh, so that the excretion of urea increases enormously. If it eats a larger amount, it may " put 
 on flesh," when, of course, it requires to eat more to maintain itself in this condition, unless the limit 
 of its digestive activity is reached. If a well-nourished dog is fed on less than Jj to ^ of its body 
 weight of flesh, it uses part of its own fat and muscle, gradually diminishes in weight, and ulti- 
 mately succumbs. Poorly-fed non-muscular dogs are unable from the very beginning to maintain 
 their metabolism in equilibrium for airy length of time on a purely flesh diet, as they must eat so 
 large a quantity of flesh that their digestive organs cannot digest it. The herbivora cannot live 
 upon flesh food, as their digestive apparatus is adapted solely for the digestion of vegetable food. 
 
 [The proteid metabolism depends (1) on the amount of proteids ingested, 
 for the great mass of these becomes changed into circulating albumin (v. Voit) ; 
 
 (2) upon the previous condition of nutrition of the organism, for we know that a 
 certain amount of proteid may produce very different results in the same individual 
 when he is in good health, and when he has suffered from some exhausting disease ; 
 
 (3) it is also influenced by the use of other foods, e. g. , fats and carbohydrates. 
 If a certain amount of fat be added to a diet of flesh, much less flesh is required, 
 so that the N metabolism is reduced by fat. This is spoken of as the " albumin- 
 sparing action" of fats.] 
 
 Exactly the same result occurs with other forms of proteids as with flesh. It 
 has been proved that gelatin may, to a certain extent, replace proteids in the 
 food, in the proportion of 2 of gelatin to 1 of albumin. The carnivora, which can 
 maintain their metabolism in equilibrium by eating a large amount of flesh, can 
 do so with less flesh when gelatin is added to their food. A diet of gelatin alone, 
 which produces much urea, is not sufficient for this purpose, and animals soon lose 
 their appetite for this kind of food (v. Bischoff, v. Voit, v. Pettenkqfer, Oeruni). 
 
 [Voit has shown that gelatin readily undergoes metabolism in the body and forms urea, and if a 
 small quantity be taken it is completely and rapidly metabolized. When administered, it acts, just 
 like fats and carbohydrates, as an " albumin -sparing " substance. It seems that gelatin is not avail- 
 able directly for the growth and repair of tissues (Bauer).~\ 
 
 Owing to the great solubility of gelatin, the value of gelatin as a food used to be greatly discussed, 
 and now, again, the addition of gelatin in the form of calf 's-foot jelly is recommended to invalids. 
 [When a large amount of gelatin is given as food, owing to the large and rapid excretion of urea 
 the latter excites diuresis.] When chondrin is given along with flesh for a time, grape sugar is 
 found in the urine (Bodeker). 
 
 [The Metabolism of Peptones. — Most of the proteids absorbed into the 
 blood are previously converted into peptones by the digestive juices. It has been 
 
FLESH AND CARBOHYDRATES. 397 
 
 asserted, more especially by Briicke, that some albumin is absorbed unchanged 
 (§ 192, 4), and that only this is capable of forming organic albumin, while the 
 peptones, after undergoing a reconversion into albumin, undergo decomposition as 
 such. This view is opposed by many observers (Adamkiewicz, Plbsz, Maly), who 
 maintain that peptones perform all the functions of proteids, so that peptones, 
 with the other necessary constituents of an adequate diet, form an adequate diet.] 
 
 239. A DIET OF FAT OR OF CARBOHYDRATES.— If fat alone 
 
 be given as a food, the animal lives but a short time. The animal so fed secretes 
 even less urea than when it is starving ; so that the consumption of fat limits the 
 decomposition of the animal's own proteids. This depends upon the fact that 
 fat, being an easily oxidized body, yields heat chiefly, and becomes sooner oxi- 
 dized than the nitrogenous proteids which are oxidized with more difficulty. If 
 the amount of fat taken be very large, all the C of the fat does not reappear, e.g., 
 in the C0 2 of the expired air ; so that the body must acquire fat, while at the same 
 time it decomposes proteids. The animal thus becomes poorer in proteids and 
 richer' in fats at the same time. 
 
 [The Metabolism of Fats is not dependent on the amount of fats taken with 
 the food. 1. It is largely influenced by work, i. e., by the activity of the tissues, 
 and, in fact, with muscular work C0 2 is excreted in greatly increased amount 
 (§ 127, 6). 2. -By the temperature of the surroundings, as more C0 2 is produced 
 in the cold (§ 214, 2), and far more fatty foods are required in high latitudes.] 
 
 [In their action on the organism, proteids and fats so far oppose each other, as 
 the former increases the waste, and therefore oxidation, while the latter diminish 
 it, probably by affecting the metabolic activity of the cells themselves (Bauer). 
 As a matter of fact, fat animals or persons bear starvation better than spare indi- 
 viduals. In the latter, the small store of fat is soon used up, and then the albumin 
 is rapidly decomposed. For the same reason, corpulent persons are very apt to 
 become still more so, even on a very moderate diet.] 
 
 When carbohydrates alone are given, they must first be converted by the 
 act of digestion into sugar. The result of such feeding coincides pretty nearly 
 with the results of feeding with fat alone. But the sugar is more easily burned or 
 oxidized within the body than the fat, and 1 7 parts of carbohydrate are equal to 
 10 parts of fat. Thus the diet of carbohydrates limits the excretion of urea more 
 readily than a purely fat diet. The animals lose flesh, and appear even to use up 
 part of their own fat. 
 
 [The Metabolism of Carbohydrates. — They also serve to diminish the 
 proteid metabolism, as they are rapidly burned up and thus "spare" the circu- 
 lating albumin. But Pettenkofer and Voit assert that they are rapidly destroyed 
 in the body, even when given in large amount, so that they differ from fats in this 
 respect. They are more easily oxidized' than fats, so that they are always con- 
 sumed first in a diet of carbohydrates and fat. By being consumed, they protect 
 the proteids and fats from consumption.] 
 
 The direct introduction of grape sugar and cane sugar into the blood does not increase the amount 
 of oxygen used, although the amount of C0 2 formed is increased ( Wolfers). 
 
 [The doctrine of Liebig, that the oxygen taken in was a measure of the metabolic processes, is 
 refuted by these and other experiments. It would seem that fat is not directly oxidized by O, but 
 that it is split up into other simpler compounds which are slowly and gradually oxidized ; in fact, 
 fat may lessen the amount of (3 taken in, as it diminishes waste.] 
 
 240. FLESH AND FAT, OR FLESH AND CARBOHYDRATES. 
 
 — Since an amount of flesh equal to -fa to -fo of the weight of the body is required 
 to nourish a dog which is fed on a purely flesh diet, if the necessary amount of 
 fat or carbohydrates be added to the diet, a smaller quantity of flesh is required 
 (». Voit and Gruber). For 100 parts of fat added to the flesh diet, 245 parts of 
 dry flesh or 227 of syntonin can be dispensed with., If instead of fats carbohy- 
 drates are added, then 100 parts of fat = 230-250 of the latter {Rubner). 
 
398 ORIGIN OF FAT IN THE BODY. 
 
 When the amount of flesh is insufficient, the addition of fat or carbohydrates to the 
 food always limits the decomposition of the animal's own substance. Lastly, 
 when too much flesh is given along with these substances, the weight of the body 
 increases more with them than without them. Under these circumstances, the 
 animal's body puts on more fat than flesh. 
 
 The consumption of O in the body is regulated by the mixture of flesh and 
 non-nitrogenous substances, rising and falling with the amount of flesh consumed. 
 It is remarkable that more O is consumed when a given amount of flesh is taken, 
 than when the same amount of flesh is taken with the addition of fat (v. Petten- 
 kqfer and v. Voif). 
 
 It seems that, instead of fat, the corresponding amount of fatty acids has the same effect on the 
 metabolism. [If a dog be fed with fatty acids and a sufficient amount of proteid, no fatty acids are 
 found in the chyle, while fat is formed synthetically, the glycerin for the latter probably being pro- 
 duced in the body.] They are absorbed as an emulsion, just like the fats. When so absorbed, 
 they seem to be reconverted into fats in their passage from the intestine to the thoracic duct, probably 
 by the action of the leucocytes (J. Muni, Will). Glycerin does not diminish the decomposition 
 of albumin within the body (Lewin, Tschirwinsky, J. Munk). According to Lebedeff and v. Voit, 
 it diminishes the decomposition of the fats, and is therefore a food. 
 
 241. ORIGIN OF FAT IN THE BODY.— I. Part of the fat of the 
 
 body is derived directly from the fat of the food, *". e., it is absorbed and depos- 
 ited in the tissues. This is shown by the fact that, with a diet containing a small 
 amount of albumin, the addition of more fat causes the deposition of a larger 
 amount of fat in the body (v. Voil, Hofmann). 
 
 Lebedeff found that dogs, which were starved for a month, so as to get rid of all their own fat, 
 on being fed with linseed oil, or mutton suet and flesh, had these fats restored to their tissues. These 
 fats, therefore, must have been absorbed and deposited. J. Munk found the same on feeding 
 animals with rape-seed oil. Fatty acids may also contribute to the formation of fats, as glycerin 
 when formed in the body must be stored up during metabolism [J. Munk). 
 
 II. A second source of the fats is their formation from albuminous bodies 
 (Liebig and others). In the case of the formation of fat from proteids which 
 may yield 11 per cent, of fat (according to Henneberg 100 parts of dry albumin 
 can form 51.5 parts of fat), these proteids split up into a non-nitrogenous and a 
 nitrogenous atomic compound. The former, during a diet containing much al- 
 bumin, when it is not completely oxidized into C0 2 , and H 2 is the substance 
 from which the fat is formed — the latter leaves the body oxidized chiefly to the 
 stage of urea. 
 
 Examples. — That fats are formed from proteids is shown by the following: 1. A cow which 
 produces I lb. of butter daily does not take nearly this amount of fatty matter in its food, so that 
 the fat would appear to be formed from vegetable proteids. 2. Carnivora giving suck, when fed on 
 plenty of flesh and some fat, yield milk rich in fat. 3. Dogs fed with plenty of flesh and some fat, 
 add more fat to their bodies than the fat contained in the food. 4. Fatty degeneration, e.g., of 
 nerve and muscle, is due to decomposition of proteids. 5. The transformation of entire bodies, e.g., 
 such as have lain for a long time surrounded with water, into a mass consisting almost entirely of 
 palmitic acid or adipocere {Fourcroy), is also a proof of the transformation of part of the proteids 
 into fats. 6. Fungi are also able to form fat from albumin during their growth (v. Naegeli, and 0. 
 Low). 
 
 Fats not merely absorbed. — Experiments which go to show that the fat of animals, during 
 the fattening process, is not absorbed as such from the food : 1 . Fattening occurs with flesh and 
 soaps; it is most improbable that the soaps are re-transformed into neutral fats by taking up glycerin 
 and giving up alkali (Kithne and Radziejewski). 2. If a lean dog be fed with flesh and palmitin- 
 and stearin-soda soap, the fat of its body contains, in addition to palmitin and stearin, olein fat, so 
 that the last must be formed by the organism from the proteids of the flesh. Further, Ssubotin 
 found that when a lean dog was fed on lean meat and spermaceti fat, a very small amount of the 
 latter was found in the fat of the animal. Although these experiments show that the fat of the body 
 must be formed from the decomposition of proteids, they do not prove that all the fat arises in this 
 way, and that none of it is absorbed and redeposited. 
 
 III. According to v. Voit, no fat is formed in the body directly from carbo- 
 hydrates, e.g., by reduction. As fattening occurs on a diet of pure flesh with 
 
CORPULENCE. 399 
 
 the addition of carbohydrates, we must assume that the carbohydrates are con- 
 sumed or oxidized in the body, and that thereby a non-nitrogenous body derived 
 from the proteids is prevented from being burned up, and that it is changed into 
 fat, and stored up as such. No doubt fat is formed indirectly in the blood in this 
 way (§ 240). 
 
 From experiments upon fattening animals, however, Lawes and Gilbert, Leh- 
 mann, Heiden, v. Wolff, think they are entitled to conclude that the carbo- 
 hydrates absorbed are directly concerned in the formation of fats, a view which is 
 supported by Henneberg, B. Schulze, Soxhlet. According to Pasteur, glycerine 
 (the basis of neutral fats) may be formed from carbohydrates. 
 
 Formerly it was believed that bees could prepare wax from honey alone ; this is a mistake — an 
 equivalent of albumin is required in addition — the necessary amount is found in the raw honey 
 itself.- 
 
 242. CORPULENCE. — The addition of too much fat to the body is a pathological phe- 
 nomenon which is attended with disagreeable consequences. With regard to the causes of 
 obesity, without doubt there is an inherited tendency (in 33 to 56 per cent, of the cases — Bou- 
 chard, Chalmers) in many families — and in some breeds of cattle, to lay up fat in the body, while 
 other families may be richly supplied with fat, and yet remain lean. The chief cause, however, is 
 taking too much food, i.e., more than the amount required for the normal metabolism ; corpulent 
 people, in order to maintain their bodies, must eat absolutely and relatively more than persons of 
 spare habit, under analogous conditions of nutrition (fj 236). 
 
 Conditions favoring Corpulence. — The following conditions favor the occurrence of corpu-l 
 lence : (1) A diet richin proteids, with a corresponding addition of fat 'or carbohydrates. As flesh orl 
 muscle is formed from proteids, and part of the fat of the body is also formed from albumin (p. 398), 
 the assumption that fats and carbohydrates fatten, or when taken alone, act as fattening agents, is 
 completely without foundation. No one ever becomes fat without taking plenty of albumin. (2) 
 Diminished disintegration of materials within the body, e.g., (a) diminished muscular activity 
 (much sleep and little exercise) ; (b) abrogation of the sexual functions (as is shown by the rapid \ 
 fattening of castrated animals, as well as by the fact that some women, after cessation of the menses, \ 
 readily become corpulent) ; (c) diminished mental activity (the obesity of dementia), phlegmatic 
 temperament. On the contrary, vigorous mental work, excitable temperament, care and sorrow, 
 counteract the deposit of fat ; (d) diminished extent of the respiratory activity, as occurs whenj 
 there is a great deposition of fat in the abdomen, limiting the action of the diaphragm (breathless- 1 
 ness of corpulent people), whereby the combustion of the fatty matters, which become deposited in I 
 the body is limited ; \e) a corpulent person requires to use relatively less heat-giving substances in 
 his body, partly because he gives off relatively less heat from his compact body, than is done by a 
 slender, long-bodied individual, and partly because the thick layer of fat retards the conduction of 
 heat (§ 214, 4). Thus, corresponding to the relatively diminished production of heat, more fat j, 
 may be stored up; (/) a diminution of the red blood corpuscles, which are the great exciters of^ 
 oxidation in the body, is generally followed by an increase of fat — fat people, as a rule, are fat 
 because they have relatively less blood (§ 41) — women with fewer red blood corpuscles are usually 
 fatter than men; (g) the consumption of alcohol favors the conservation of fat in the body; the f 
 alcohol is easily oxidized, and thus prevents the fat from being burned up (§ 235). J 
 
 Well- nourished individuals are usually at first both muscular and endowed with a fair amount of 
 fatty tissue. When they begin to put on fat, the development of the muscular system lags behind, 
 partly because the increasing corpulence leads to diminished activity of the muscular system, so 
 'that this system is involved secondarily. Some lively corpulent people, nevertheless, retain their 
 muscular energy. When those conditions which favor corpulence are especially active, corpulence 
 may ultimately pass into a condition of great obesity. \ 
 
 Disadvantages. — Besides the inconvenience of the great size and weight of the body, corpu- \ 
 lent people suffer from breathlessness — they are easily fatigued, are liable to intertrigo between the ) 
 folds of the skin, the heart becomes loaded with fat, and they not unfrequently are subject to 
 apoplexy. 
 
 In order to counteract corpulence we ought to— (1) Reduce uniformly all articles of diet. 
 The diet and body ought to be weighed from week to week, and as long as there is no diminution 
 in the body weight, the amount of food ought to be gradually and uniformly reduced (notwithstand- 
 ing the appetite). This must be done very gradually and not suddenly. A moderate reduction of 
 fat and carbohydrates in a normal diet, at the same time leads to a diminution of the fat of the 
 body itself. Let a person who is capable of muscular exertion take 156 grms. proteid, 43 grms. fat, 
 and 1 14 grms. carbohydrates ; but in those where congestions, hydrsemia, breathlessness have taken 
 place, take 170 grms. proteid, 25 grms. fat, and 70 grms. carbohydrates [Oertel). It is not advisable 
 to limit the amount of fat and carbohydrates alone, as is done in the Banting cure or Bantingism. 
 Apart altogether from the fact that fat is formed from proteids, if too little non-nitrogenous food be 
 taken, severe disturbance of the bodily metabolism is apt to occur. (2) It is advisable during the 
 
400 METABOLISM OF THE TISSUES. 
 
 chief meal to limit the consumption of fluids of all sorts (even until three-quarters of an hour there- 
 after), and thus render the absorption and digestive activity of the intestine less active {Oertel). 
 (3) The muscular activity ought to be greatly developed by doing plenty of muscular work, or 
 taking plenty of exercise, both physical and mental. (4) Favor the evolution of heat by taking 
 cold baths of considerable duration, and afterward rubbing the skin strongly so as to cause it to 
 become red ; further, dress lightly, and at night use light bed clothing ; tea and coffee are useful, 
 as they excite the circulation. (5) Use gentle laxatives; acid fruits, cider; alkaline carbonates 
 [Marienbad, Carlsbad, Vichy, Neuenahr, Ems, etc.), act by increasing the intestinal evacuations 
 and diminishing absorption. (6) If from accumulation of fat there is danger of failure of the 
 heart's action, Oertel recommends hill climbing, whereby the cardiac muscle is exercised and 
 strengthened. At the same time the circulation becomes more lively and the metabolism is 
 increased. 
 
 [Oertel's Method goes on the idea of strengthening the cardiac musculature, which is sought 
 to be accomplished by (1) limiting the amount of fluids consumed, and (2) carefully regulated mus- 
 cular exertion. The amount of food is first reduced one -half, and the water to a still lower amount, 
 while the nitrogenous elements in food are increased, the non-nitrogenous are decreased. The per- 
 son is then instructed to take exercise under certain medical precautions, first, on level ground, and 
 then on gradually increasing gradients. Oertel has opened several establishments in Germany 
 (Terrain Curorte) for conducting what he calls his Terrain Cur.] 
 
 Fatty Degeneration. — The process of fattening consists in the deposition of drops of fat within 
 the fat cells of the panniculus and around the viscera, as well as in the marrow of bone (but they 
 are never deposited in the subcutaneous tissue of the eyelids, of the penis, of the red part of the 
 lips, in the ears and nose). This is quite different from the fatty atrophy or fatty degeneration 
 which occurs in the form of fatty globules or granules in albuminous tissues, e.g., in muscular fibres 
 (heart), gland cells (liver, kidney), cartilage cells, lymph and pus corpuscles, as well as in nerve 
 fibres separated from their nerve centres. The fat in these cases is derived from albumin, much in 
 the same way as fat is formed in the gland cells of the mammary and sebaceous glands. Marked 
 fatty degeneration not unfrequently occurs after severe fevers, and after artificial heating of the tis- 
 sues ; when a too small amount of O is supplied to the tissues, as occurs in cases of phosphorus 
 poisoning [Bauer) ; in drunkards; after poisoning with arsenic and other substances; and after 
 some disturbances of the circulation and innervation. Some organs are especially prone to undergo 
 fatty degeneration during the course of certain diseases. . 
 
 243. METABOLISM OF THE TISSUES.— The blood stream is 
 
 the chief medium whereby new material is supplied to the tissues and the effete 
 products removed from them. The lymph which passes through the thin capil- 
 laries comes into actual contact with the tissue elements. Those tissues which 
 are devoid of blood vessels in their own substance, such as the cornea and cartil- 
 age, receive nutrient fluid or lymph from the adjacent capillaries, by means of 
 their cellular elements, which act as juice-conducting media. Hence, when the 
 normal circulation is interfered with, as by atheroma or calcification of the walls 
 of the blood vessels, these tissues are secondarily affected [this, for example, is 
 the case in arcus senilis of the cornea, due to a fatty degeneration of the corneal 
 tissue, owing to some affection of the blood vessels on which the cornea depends 
 for its nutrition]. Total compression or ligature of all the blood vessels results 
 in necrosis of the parts supplied by the ligatured blood vessels. 
 
 Atrophies caused by diminution of the normal supply of blood gradually, in the course of time, 
 become less and less [Samuel). 
 
 Hence, there must be a double current of the tissue juices; the afferent or 
 supply current, which supplies the new material, and the efferent stream, 
 which removes the effete products. The former brings to the tissues the proteids, 
 fats, carbohydrates, and salts from which the tissues are formed. It is evident 
 that any interruption of the arterial supply to the tissues will diminish this supply. 
 
 That such a current exists is proved by injecting an indifferent, easily recognizable substance into 
 the blood, e.g., potassium ferrocyanide, when its presence may be detected in the tissues, to which 
 it has been carried by the outgoing current. 
 
 The efferent stream carries away the decomposition products from the various 
 tissues, more especially urea, C0 2 , H 2 0, and salts, and these are transferred as 
 quickly as possible to the organs through which they are excreted. 
 
 That such a current exists is proved by injecting such a substance as potassium ferrocyanide into 
 the tissues, e.g., subcutaneously, when its presence may be detected in the urine within two to five 
 minutes. 
 
METABOLISM OF THE TISSUES. 401 
 
 If the current from the tissues to the blood is so active that the excretory organs 
 cannot eliminate all the effete products from the blood, then these products are 
 found in the tissues. This occurs when certain poisons are injected subcutaneously, 
 when they pass rapidly into the blood and are carried in great quantity to other 
 tissues, e.g., to the nervous system, on which they act with fatal effect, before 
 they are eliminated to any great extent from the blood by the action of the 
 excretory organs. The effete materials are carried away from the tissues by two 
 channels, viz., by the veins and by the lymphatics, so that if these be inter- 
 fered with, the metabolism of the tissues must also suffer. When a limb is ligatured 
 so as to compress the veins and the lymphatics, the efferent stream stagnates to 
 such an extent that considerable swelling of the tissues or oedema may occur 
 (§ 203). The action of the muscles and fascia? are very important in removing 
 these effete matters (Hasse). 
 
 H. Nasse found that the blood of the jugular vein is 0.225 P er IOO ° specifically heavier than the 
 blood of the carotid, and contains 0.9 parts per 1000 more solids; 1000 cubic centimetres of blood 
 circulating through the head yield about 5 cubic centimetres of transudation into the tissues. 
 
 The extent and intensity of the metabolism of the tissues depend upon 
 a variety of factors. 
 
 1. Upon their activity. The increased activity of an organ is indicated by 
 the increased amount of blood going into it, and by the more active circulation 
 through it (§ 100). When an organ is completely inactive, such as a paralyzed 
 muscle, or the peripheral end of a divided nerve, the amount of blood and the 
 nutritive exchange of fluids diminish within these parts. The parts thus thrown 
 out of activity become pale, relaxed, and ultimately undergo fatty degeneration. 
 The increased metabolism of an organ during its activity has been proved experi- 
 mentally in the case of muscle, and [(§ 263) also in the brain {Speck).'] Langley 
 and Sewell have recently observed directly the metabolic changes within sufficiently 
 thin lobules of glands during life. The cells of serous glands (§ 143), and those 
 of mucus- and pepsin-forming glands (§ 164), during quiescence, become filled 
 with coarse granules, which are dark in transmitted light and white in reflected 
 light, which granules are consumed or disappear during granular activity. During 
 sleep, when most organs are at rest, the metabolism is limited ; darkness also 
 diminishes it, while light excites it, obviously owing to nervous influences. The 
 variations in the total metabolism of the body are reflected in the excretion of 
 C0 2 (§ 127, 9) and urea (§ 257), which may be expressed graphically in the form 
 of a curve corresponding with the activity of the organism ; this curve corresponds 
 very closely with the daily variations in the respirations, pulse, and temperature 
 
 (P- 359)- 
 
 2. The composition or quality of the blood has a marked effect upon the 
 current on which the metabolism of the tissues depends. Very concentrated 
 blood, which contains a small amount of water, as after profuse sweating, severe 
 diarrhoea — e.g., in cholera — makes the tissues dry, while if much water be absorbed 
 into the blood, the tissues become more succulent and even oedema may occur. 
 When much common salt is present in the blood, and when the red blood cor- 
 puscles contain a diminished amount of O, and especially if the latter condition 
 be accompanied by muscular exertion causing dyspnoea, a large amount of albumin 
 is decomposed, and there is a great formation of urea. Hence, exposure to a 
 rarefied atmosphere is accompanied by increased excretion of urea. Certain 
 abnormal conditions of the blood produce remarkable results ; blood charged with 
 carbonic oxide cannot absorb O from the air, and does not remove C0 2 from the 
 tissues (§ 16). The presence of hydrocyanic acid in the blood (§ 16) is said to 
 interrupt at once the chemical oxidation processes in the blood, so that rapid 
 asphyxia, owing to cessation of the internal respiration, occurs. Fermentation is 
 interrupted by the same substance in a similar way. A diminution of the total 
 amount of the blood causes more fluid to pass from the tissues into the blood ; but 
 
 26 
 
402 REGENERATION OF ORGANS AND TISSUES. 
 
 the absorption of substances, such as poisons or pathological effusions, from the 
 tissues or intestines is delayed. If the substances which pass from the tissues into 
 the blood be rapidly eliminated from it, absorption takes place more rapidly. 
 
 3. The blood pressure is of importance, in so far, that when it is greatly in- 
 creased, the tissues contain more fluid, while the blood itself becomes more con- 
 centrated, to the extent of 3 to 5 per 1000 (Nasse). We may convince ourselves 
 that blood plasma easily passes through the capillary wall, by pressing upon the 
 efferent vessel coming from the chorium deprived of its epidermis, e.g., by a burn 
 or a blister, when the surface of the wound becomes rapidly suffused with plasma. 
 Diminution of the blood pressure produces the opposite result. The oxidation 
 processes in the body are diminished after the use of P, Cu, ether, chloroform, 
 chloral (Nencki and Sieber). 
 
 4. Increased temperature of the tissues (several hours daily) does not 
 increase the breaking up of albumin and fats {Koch, Stockvis, Simanowsky , and 
 v. Voit). (See also Artificial Elevation of the Temperature, § 221 ; Fever, § 220 ; 
 and Artificial Cooling, § 225.) 
 
 5. The influence of the nervous system on the metabolism is twofold. On 
 the one hand, it acts indirectly through its effect upon the blood vessels, by caus- 
 ing them to contract or dilate through the agency of vaso-motor nerves, 
 whereby it influences the amount of blood supplied, and also affects the blood 
 pressure. But in addition to this, and quite independently of the blood vessels, 
 it is probable that certain special nerves — the so-called trophic nerves, influence 
 the metabolism or nutrition of the tissues (§ 342, c). That nerves do influence 
 directly the transformation of matter within the tissues is shown by the secretion 
 of saliva resulting from the stimulation of certain nerves, after cessation of the 
 circulation (§ 145), and by the metabolism during the contraction of bloodless 
 muscles. Increased respiration and apnoea are not followed by increased oxida- 
 tion (Pfliiger) (§ 127, 8). 
 
 [Gaskell has raised the question as to the existence of katabolic and anabolic nerves control- 
 ling respectively the analytic and synthetic metabolism of the tissues (p. 373).] 
 
 244. REGENERATION OF ORGANS AND TISSUES.— The extent to which lost 
 parts are replaced varies greatly in different organs. Among the lower animals the parts of organs 
 are replaced to a far greater extent than among warm-blooded animals. When a hydra is divided 
 into two parts, each part forms a new individual — nay, if the body of the animal be divided into 
 
 . several'parts in a particular way, then each part gives rise to a new individual (Spallanzani). The 
 Planarians also show a great capability of reproducing lost parts (Duyis). Spiders and crabs can 
 
 ; reproduce lost feelers, limbs, and claws; snails, part of the head, feelers, and eyes, provided the 
 
 ■ central nervous system is not injured. Many fishes reproduce fins, even the tail fin. Salamanders 
 and lizards can produce an entire tail, including bones, muscles, and even the posterior part of the 
 
 : spinal cord ; while the triton reproduces an amputated limb, the lower jaw and the eye. This re- 
 
 , production necessitates that a small stump be left, while total expiration of the parts prevents repro- 
 
 • duction (Pkilippeaux). 
 
 In amphibians and reptiles the regeneration of organs and tissues, as a whole, takes place after 
 the type of the embryonic development (Fraisse, Gotte), and the same is true as regards the histo- 
 
 . logical processes which occur in the regenerated tail and other parts of the body of the earthworm 
 ( Billow). 
 
 The extent to which regeneration can take place in mammals and in man is very 
 slight, and even in these cases it is chiefly confined to young individuals. A true 
 regeneration occurs in — 
 
 1. The blood (compare § 7 and § 41), including the plasma, the colorless and 
 colored corpuscles. 
 
 2. The epidermal appendages (§ 283) and the epithelium of the mucous 
 membranes are reproduced by a proliferation of the cells of the deeper layers of 
 the epithelium, with simultaneous division of their nuclei. Epithelial cells are 
 reproduced as long as the matrix on which they rest and the lowest layer of cells 
 are intact. When these are destroyed cell-regeneration from below ceases, and 
 the cells at the margins are concerned in filling up the deficiency. Regeneration, 
 
REGENERATION OF TISSUES. 403 
 
 therefore, either takes place from below or from the margins of the wound in the 
 epithelial covering ; leucocytes also wander into the part, while the deepest layer 
 of cells forms large multi-nucleated cells, which reproduce by division polygonal, 
 flat, nucleated cells {Klebs, Heller). [In the process of division of the cells, the 
 nucleus plays an important part, and in so doing it shows the usual karyokinetic 
 figures (§ 431).] The nails grow from the root forward ; those of the ringers in 
 four to five months, and that of the great toe in about twelve months, although 
 growth is slower in the case of fracture of the bones, The matrix is co-extensive 
 with the lunule, and if it be destroyed the nail is not reproduced (§ 284). The 
 eyelashes are changed in 100 to 150 days (Donders), the other hairs of the body 
 somewhat more slowly. If the papilla of the hair follicle be destroyed, the hair 
 is not reproduced. Cutting the hair favors its growth, but hair which has been 
 cut does not grow longer than uncut hair. After hair has grown to a certain length 
 it falls out. The hair never grows at its apex. The epithelial cells of mucous 
 membranes and secretory glands seem to undergo a regular series of changes and 
 renewal. The presence of secretory cells in the milk (§ 231) and in the sebaceous 
 secretion (§ 285) proves this ; the spermatozoa are replaced by the action of sper- 
 matoblasts. In catarrhal conditions of mucous membranes, there is a great 
 increase in the formation and excretion of new epithelium, while many cells are 
 but indifferently formed and constitute mucous corpuscles. The crystalline 
 lens, which is just modified epithelium, is reorganized just like epithelium ; its 
 matrix is the anterior wall of its capsule, with the single layer of cells covering it. 
 If the lens be removed and this layer of cells retained, these cells proliferate and 
 elongate to form lens fibres, so that the whole cavity of the empty lens capsule is 
 refilled. If much water be withdrawn from the body, the lens fibres become 
 turbid (Kunde, Koehnhorri). [A turbid or opaque condition of the lens may occur 
 in diabetes, or after the transfusion of strong common salt or sugar solution into 
 a frog.] 
 
 3. The blood vessels undergo extensive regeneration, and they are regener- 
 ated in the same way as they are formed (§ 7, B). Capillaries are always the first 
 stage, and around them the characteristic coats are added to form an artery or a 
 vein. When an artery is injured and permanently occluded, as a general rule 
 the part of the vessel up to the nearest collateral branch becomes obliterated, 
 whereby the derivatives of the endothelial lining, the connective-tissue corpuscles 
 of the wall, and the leucocytes change into spindle-shaped cells, and form a kind 
 of cicatricial tissue. Blind and solid outshoots are always found on the blood 
 vessels of young and adult animals, and are a sign of the continual degeneration 
 and regeneration of these vessels (Sigm. Mayer). 
 
 Lymphatics behave in the same way as blood vessels ; after removal of a lym- 
 phatic gland, a new one may be formed {Bayer). 
 
 4. The contractile substance of muscle may undergo regeneration after it 
 has become partially degenerated. This takes place after amyloid or wax-like 
 degeneration, such as occurs not unfrequently after typhus and other severe fevers. 
 This is chiefly accomplished by an increase of the muscle corpuscles. After being 
 compressed, the muscular nuclei disappear ; and at the same time the contractile 
 contents degenerate {Heidelberg). After several days, the sarcolemma contains 
 numerous nuclei which reproduce new muscular nuclei and the contractile sub- 
 stance (Kraske, Erbkam). In fibres injured by a subcutaneous wound, Neumann 
 found that, after five to seven days, there was a bud-like elongation of the cut 
 ends of the fibres, at first without transverse striation ultimately. If a large extent 
 of a muscle be removed, it is replaced by cicatricial connective tissue. Non- 
 striped muscular fibres are also reproduced ; the nuclei of the injured fibres divide 
 after becoming enlarged, and exhibit a well-marked intranuclear plexus of fibrils. 
 The nuclei divide into two, and from each of these a new fibre is formed, prob- 
 ably by the differentiation of the perinuclear protoplasm. 
 
404 REGENERATION OF BONE. 
 
 5. After a nerve is divided, the two ends do not join at once so as to permit 
 the function of the nerve to be established. On the contrary, marked changes 
 occur. If a piece be cut out of a nerve trunk, the peripheral end of the divided 
 nerve degenerates, the axial cylinder and the white substance of Schwann disap- 
 pear. The interval is filled up at first with juicy, cellular tissue. The subsequent 
 changes are fully described in § 325, 4. There seems to be in peripheral nerves a 
 continual disappearance of fibres by fatty degeneration, accompanied by a con- 
 secutive formation of new fibres (Sigm. Mayer). The regeneration of peripheral 
 ganglionic cells is unknown, v. Voit, however, observed that a pigeon, part of 
 whose brain was removed, had within five months reproduced a nervous mass 
 within the skull, consisting of medullated nerve fibres and nerve cells. Eichhorst 
 and Naunyn found that in young dogs, whose spinal cord was divided between the 
 dorsal and lumbar regions, there was an anatomical and physiological regeneration, 
 to such an extent that voluntary movements could be executed (§ 338, 3). Vau- 
 lair, in the case of frogs, and Masius in dogs, found that mobility or motion was 
 first restored, and afterward sensibility. Regeneration of the spinal ganglia did 
 not occur. 
 
 6. If a portion of a secretory gland be removed, as a general rule, it is not 
 reproduced. But the bile ducts (§ 173) and the pancreatic duct may be 
 reproduced (§ 171). According to Phihppeaux and Griffini, if part of the 
 spleen be removed it is reproduced (§ 103). Tizzoni and Collucci observed 
 the formation of new liver cells and bile ducts after injury to the liver (§ 173), 
 and Pisenti makes the same statement as regards the kidney. After me- 
 chanical injury to the secretory cells of glands (liver, kidney, salivary, 
 Meibomian) neighboring cells undergo proliferation and aid in the restoration 
 of the cells ( W. Podwisotzky). 
 
 7. Among connective tissues, cartilage, provided its perichondrium be not in- 
 jured, reproduces itself by division of its cartilage cells {Redferti) ; but usually 
 when a part of a cartilage is removed, it is replaced by connective tissue. 
 
 8. When a tendon is divided, proliferation of the tendon cells occurs, and the cut 
 ends are united by connective tissue. 
 
 9. The reproduction of bone takes place to a great extent under certain con- 
 ditions. If the articular end be removed by excision, it may be reproduced, 
 although there is a considerable degree of shortening. Pieces of bone which have 
 been broken off or sawed off heal again, and become united with the original bone 
 (Jakimowitsch) . If a piece of periosteum be transplanted to another region of 
 the body, it eventually gives rise to the formation of new bone in that locality. 
 If part of a bone be removed, provided the periosteum be left, new bone is rapidly 
 reproduced ; hence the surgeon takes great care to preserve the periosteum intact 
 in all operations where he wishes new bone to be reproduced. Even the marrow 
 of bone, when it is transplanted, gives rise to the formation of bone. This is due 
 to the osteoblasts adhering to the osseous tissue (P. Burns, MacEwen). 
 
 In fracture of a long bone the periosteum deposits on the surface of the ends of the broken 
 bones a ring of substance which forms a temporary support, the external callus. At first this 
 callus is jelly-like, soft, and contains many corpuscles, but afterward it becomes more solid and 
 somewhat like cartilage. A similar condition occurs within the bone, where an internal callus is 
 formed. The formation of this temporary callus is due to an inflammatory proliferation of the 
 marrow. According to Rigal and Vignal, the internal callus is always osseous, and is derived from 
 the marrow of the bone. The outer and inner callus become calcified and ultimately ossified, 
 whereby the broken ends are reunited. Toward the fortieth day, a thin layer of bone is formed 
 (intermediary callus ) between the ends of the bone. Where this begins to be definitely ossified, 
 the outer and inner callus begin to be absorbed, and ultimately the intermediary callus has the same 
 structure as the rest of the bone. 
 
 There are many interesting observations connected with the growth and metabolism of bones. 
 1. The addition of a very small amount of phosphorus ( Wagner) or arsenious acid (Maas) to the 
 food causes considerable thickening of the bones. This seems to be due to the non-absorption of 
 those parts of the bones which are usually absorbed, while new growth is continually taking place. 
 
INCREASE IN SIZE AND WEIGHT DURING GROWTH. 405 
 
 2. When food devoid of lime salts is given to an animal, the growth of the bones is not arrested 
 {v. Voii), but the bones become thinner, whereby all parts, even the organic basis of the bone, 
 undergo a uniform diminution (Chossat,A. Milne-Edwards). 3. Feeding with madder makes the 
 bones red, as the coloring matter is deposited with the bone salts in the bone, especially in the grow- 
 ing and last-formed parts. In birds the shell of the egg becomes colored. 4. The continued use of 
 lactic acid dissolves the bones (Siedamgrotzky and Hofmeister). The ash of bone is thereby dimin- 
 ished. If lime salts be withheld at the same time, the effect is greatly increased, so that the bones 
 come to resemble rachitic bones. (Development of Bone, \ 447.) 
 
 When a lost tissue is not replaced by the same kind of tissue, its place is always 
 taken by cicatricial connective tissue. 
 
 When this is the case, the part becomes inflamed and swollen, owing to an exudation of plasma. 
 The blood vessels become dilated and congested, and notwithstanding the slower circulation, the 
 amount of blood is greater. The blood vessels are increased, owing to the formation of new ones. 
 Colorless blood corpuscles pass out of the vessels and reproduce themselves, and many of them 
 undergo fatty degeneration, while others take up nutriment and become converted into large uni- 
 nucleated protoplasma cells, from which giant cells are developed {Ziegler, Cohnheim). The 
 newly-formed blood vessels supply all these elements with blood. 
 
 245. TRANSPLANTATION OF TISSUES.— The nose, ear, and even a finger, after 
 having been severed from the body by a clean cut, have, under certain circumstances, become united 
 to the part from which they were removed. The skin is frequently transplanted by surgeons, as, 
 for example, to form a new nose. The piece of skin is cut from the forehead or arm, to which it 
 is left attached by a bridge of skin. The skin is then stitched to the part which it is desired to 
 cover in, and when it has become attached in its new situation, the bridge of skin is severed. Re- 
 verdin cut a piece of skin into pieces about the size of a pea and fixed them on an ulcerated sur- 
 face, where they, as it were, took root, grew, and sent off from their margins epithelial outgrowths, 
 so that ultimately the whole surface was covered with epithelium. The excised spur of a cock was 
 transplanted and fixed in the comb of the same animal, where it grew {John Hunter). P. Bert cut 
 off the tail and legs of rats and transplanted them under the skin of the back of other rats, where 
 they united with the adjoining parts. Oilier found that, when periosteum was transplanted, it grew 
 and reproduced bone in its new situation. Even blood and Ivmph may be transfused (Transfusion, 
 § 102). [Small portions (1.5 mm.) of epiphyses, costal cartilage, of a rabbit or kitten, when trans- 
 planted quite fresh into the anterior chamber of the eye, testis, submaxillary gland, kidney, and 
 under the skin of a rabbit, attach themselves and grow, and the growth is more rapid the more vas- 
 cular the site on which the tissue is transplanted. The cartilage is not essentially different from 
 hyaline cartilage, but the cells are fewer in the centre, while the matrix tends to become fibrous. 
 Small pieces of epiphyseal cartilage introduced into the jugular vein were found as cartilaginous 
 foci in the lungs (Zahn, Leopold). Tissues transplanted from embryonic structures grow far better 
 than adult tissues {Zahn). 
 
 Many of these results seem only to be possible between individuals of the same species, although 
 Helferich has recently found that a piece of dog's muscle, when substituted for human muscle, 
 united to the adjoining muscle, and became functionally active. [J. R. Wolfe has transplanted the 
 conjunctiva of the rabbit to the human eye.] Most tissues, however, do not admit of transplantation, 
 e.g., glands and the sense organs. They may be removed to other parts of the body, or into the 
 peritoneal cavity, without exciting any inflammatory reaction; they, in fact, behave like inert foreign 
 matter. 
 
 246. INCREASE IN SIZE AND WEIGHT DURING GROWTH.—The length of 
 the body, which at birth is usually -J T of the adult body, undergoes the greatest elongation at an 
 early period : in the first year, 20 ; in the second, 10 ; in the third, about 7 centimetres ; while from 
 five to sixteen years the annual increase is about 5^ centimetres. In the twentieth year the increase 
 is very slight. From fifty onward the size of the body diminishes, owing to the intervertebral 
 disks becoming thinner, and the loss may be 6-7 centimetres about the eightieth year. The weight 
 of the body (Jj of an adult) sinks during the first five to seven days, owing to the evacuation of 
 the meconium and the small amount of food which is taken at first. Only on the tenth day is the 
 weight the same as at birth. 
 
 The increase of weight is greater in the same time than the increase in length. Within the first 
 year a child trebles its weight. The greatest weight is usually reached about forty, while toward 
 sixty a decrease begins, which at eighty may amount even to 6 kilos. The results of measurements, 
 chiefly by Quetelet, are given in the following table : — 
 
406 
 
 INCREASE IN SIZE AND WEIGHT DURING GROWTH. 
 
 
 Length (Cm tr.). 
 
 Weight (Kilo.). 
 
 
 Length (Cmtr.). 
 
 Weight 
 
 (Kilo.). 
 
 Age 
 
 
 
 
 
 Age 
 
 
 
 
 
 
 Man. 
 
 Woman. 
 
 Man. 
 
 Woman. 
 
 
 Man. 
 
 Woman. 
 
 Man. 
 
 Woman. 
 
 O 
 
 49-6 
 
 48.3 
 
 3.20 
 
 2.9I 
 
 15 
 
 155-9 
 
 147-5 
 
 46.41 
 
 4130 
 
 I 
 
 69.6 
 
 69.0 
 
 IO.OO 
 
 9-3° 
 
 16 
 
 161.0 
 
 150.O 
 
 53-39 
 
 44-44 
 
 2 
 
 79.6 
 
 78.0 
 
 12.00 
 
 II.40 
 
 17 
 
 167.0 
 
 154-4 
 
 57-4Q 
 
 49.08 
 
 3 
 
 86.0 
 
 85.0 
 
 13.21 
 
 12.45 
 
 18 
 
 170.0 
 
 156.2 
 
 61.26 
 
 53-io 
 
 4 
 
 93-2 
 
 91.0 
 
 I5-07 
 
 14.18 
 
 19 
 
 170.6 
 
 
 6332 
 
 . . 
 
 5 
 
 99.0 
 
 97.0 
 
 16.70 
 
 1550 
 
 20 
 
 171. 1 
 
 I57.0 
 
 65.00 
 
 54-46. 
 
 6 
 
 104.6 
 
 103.2 
 
 18.04 
 
 16.74 
 
 25 
 
 172.2 
 
 157-7 
 
 68.29 
 
 55.08 
 
 7 
 
 in. 2 
 
 109.6 
 
 20.I6 
 
 18.45 
 
 30 
 
 172.2 
 
 157-9 
 
 68.90 
 
 55-H 
 
 8 
 
 117.0 
 
 "3-9 
 
 22.26 
 
 19.82 
 
 40 
 
 i7i-3 
 
 155-5 
 
 68.81 
 
 56.65 
 
 9 
 
 122.7 
 
 120.0 
 
 24.09 
 
 22.44 
 
 50 
 
 166.4 
 
 153-6 
 
 67-45 
 
 58.45 
 
 IO 
 
 128.2 
 
 124.8 
 
 26.12 
 
 24.24 
 
 60 
 
 163.9 
 
 151.6 
 
 6S-5o 
 
 56.73 
 
 II 
 
 1327 
 
 127-5 
 
 27.85 
 
 26.25 
 
 70 
 
 162.3 
 
 151-4 
 
 6303 
 
 53-72 
 
 12 
 
 135-9 
 
 132.7 
 
 3I.O0 
 
 3°-54 
 
 80 
 
 161.3 
 
 150.6 
 
 61.22 
 
 51.52 
 
 13 
 
 140.3 
 
 138.6 
 
 35-32 
 
 34.65 
 
 90 
 
 . . 
 
 
 57.83 
 
 49-34 
 
 H 
 
 148.7 
 
 144.7' 
 
 40.50 
 
 38.10 
 
 
 (Chiefly from 
 
 Quetelet.) 
 
 
 Between the twelfth and fifteenth years the weight and size of the girl are greater than of the 
 boy. Growth is most active in the last months of foetal life, and afterward from the sixth to ninth 
 year until the thirteenth to sixteenth. The full stature is reached about thirty, but not the greatest 
 weight (TAoma). 
 
CHEMICAL CONSTITUENTS OF THE ORGANISM. 
 
 247. (A) INORGANIC CONSTITUENTS.— I. Water forms 58.5 per cent, of the whole 
 body, but it occurs in different quantity in the different tissues. The kidneys contain the most 
 water, 82.7 per cent. ; bones, 22 per cent. ; teeth, 10 per cent. ; while enamel contains the least, 0.2 
 per cent. 
 
 [ Water is of the utmost importance in the economy, and it is no paradox to say that all organisms 
 live in water, for though the entire animal may not live in water, all its tissues are bathed by watery 
 fluids, and the essential vital processes occur in water ($ 229). A constant stream of water may be 
 said to be passing through organisms; a certain quantity of water is taken in with the food and drink, 
 which ultimately reaches the blood, while from the blood a constant loss is taking place by the urine, 
 the sweat, and breath. The greater quantity of the water in our bodies is derived from without, 
 but it is probable that a small amount is formed within our bodies by the action of free oxygen on 
 certain organic substances. According to some observers, peroxide of hydrogen (H 2 2 ) is also 
 present in the body.] 
 
 II. Gases. — [Oxygen is absorbed from the air, and enters the blood, where it forms a loose 
 chemical compound, with the coloring matter or haemoglobin, while a small amount exists in a free 
 state, or is simply absorbed.] Hydrogen is found in the alimentary canal. Nitrogen, [like 
 oxygen, is absorbed from the atmosphere by the blood, in which it is dissolved, and from which it 
 passes into other fluids of the body. It is probable that a very small quantity is formed within the 
 body.] 
 
 The presence of marsh gas (CH 4 ) (\ 124), ammonia (NH 3 ), C0 2 ($ 38), sulphuretted hydrogen 
 (H 2 S) (§ 184), and ozone (g 37) has been referred to already. 
 
 III. Salts. — Sodium chloride [is one of the most important inorganic substances present in 
 the body. It occurs in all the tissues and fluids of the body, and it plays a most prominent part in 
 connection with the diffusion of fluids through membranes, and its presence is necessary for the 
 solution of the globulins (8 409). In some cases it exists in a state of combination with albuminous 
 bodies, as in the blood plasma. Common salt is absolutely necessary for one's existence ; if it be 
 withdrawn entirely, life soon comes to an end. About 15 grammes are given off in twenty-four 
 hours, the great part being excreted by the urine. Bous*ingault showed that the addition of a certain 
 amount of common salt to the daily food of cattle greatly improved their condition.] 
 
 [Calcium phosphate (Ca 3 P 2 8 ) is the most abundant salt in the body, as it forms more than 
 one-half of our bones, but it also occurs in dentine, enamel, and, to a much less extent, in the other 
 solids and fluids of the body. Among secretions, milk contains relatively the largest amount (2.72 
 per cent.). In milk, it is necessary for forming the calcareous matter of the bones of the infant. 
 It gives bones their hardness, solidity, and rigidity. It is chiefly derived from the food, and, as 
 only a small quantity is given off in the excretions, it seems not to undergo rapid removal from 
 the body. J 
 
 [Sodium phosphate (PNa s O t ), acid sodium phosphate (PNa 2 4 ), acid potassium phosphate 
 (PK 2 H0 4 ). The sodium phosphate and the corresponding potash salt give most of the fluids of 
 the body their alkaline reaction. The alkaline reaction of the blood plasma is partly due to alkaline 
 phosphates, which are chiefly derived from the food. The acid sodium phosphate is the chief cause 
 of the acid reaction of the urine. A small quantity of phosphoric acid is formed in the body owing 
 to the oxidation of "lecithin," which contains phosphorus, and also forms an important constituent 
 of nerve tissue.] 
 
 [Sodium carbonate (Na 2 CO s ) and sodium bicarbonate (NaHCO s ) exist in small quantities 
 in the food, and are chiefly formed in the body from the decomposition of the salts of the vegetable 
 acids. They occur in the blood plasma, where they play an important part in carrying the C0 2 
 from the tissues to the lungs.] 
 
 [Sodium and potassium sulphates (Na 2 S0 4 and K 2 S0 4 ) exist in very small quantity in the 
 body, and are introduced with the food, but part is formed in the body from the oxidation of organic 
 bodies containing sulphur.] 
 
 [Potassium chloride (KC1) is pretty widely distributed, and it occurs specially in muscle, 
 colored blood corpuscles, and milk. Calcium fluoride (CaFl 2 ) occurs in small quantity in bones 
 and teeth. Calcium carbonate (CaCO,) is associated with calcium phosphate in bone, tooth, 
 and in some fluids, but it occurs in relatively much smaller amount. It is kept in solution by alka- 
 line chlorides, or by the presence of free carbonic acid.] 
 
 [Ammonium chloride (NH 4 C1). — Minute traces occur in the gastric juice and the urine.] 
 
 407 
 
408 THE ALBUMINOUS OR PROTEID SUBSTANCES. 
 
 [Magnesium phosphate (Mg 3 P0 4 ) occurs in the tissues and fluids of the body, along with 
 calcium phosphate, but in very much smaller quantity.] 
 
 IV. Free Acids. — Hydrochloric acid (HC1) [occurs free in the gastric juice, but in combination 
 with the alkalies it is widely distributed as chlorides]. Sulphuric acid (H 2 S0 4 ) [is said to occur 
 free in the saliva of certain gasteropods, as Dolium galea. In the body it forms sulphates, being 
 chiefly in combination with soda and potash], 
 
 V. Bases. — Silicon as silicic acid (Si0 2 ) ; manganese, iron, the last forms an integral constituent 
 of the blood pigment; copper (?), ($ 174). 
 
 248. fB) ORGANIC COMPOUNDS.— I. THE ALBUMINOUS OR PROTEID 
 SUBSTANCES.— 1. True Proteids and their Allies.— Proteids or Albumins and their 
 allies are composed of C, H, O, N. and S, and are derived from plants (see Introduction). 
 
 [According to Hoppe-Seyler their general percentage composition is — 
 
 O. H. N. C. S. 
 
 From 20.9 6.9 15.2 51.5 0.3 
 
 To 23.5 to 7.3 to 17.0 to 54.5 to 2.0. ] 
 
 They exist in all animal fluids, and in nearly all the tissues. They occur partly in the fluid 
 form, although Briicke maintains that the molecule of albumin exists in a condition midway 
 between a state of imbibition and a true solution, and partly in a more concentrated condition. 
 Besides forming the chief part of muscle, nerve, and gland, they occur in nearly all the fluids 
 of the body, including the blood, lymph, and serous fluids; but in health mere traces occur in 
 the sweat, while they are absent from the bile and the urine. Unboiled white of egg is the 
 type. In the alimentary canal they are changed into peptones. The chief products derived from 
 their oxidation within the body are C0 2 , H 2 0, and especially urea, which contains nearly all 
 the N of the proteids. 
 
 Constitution. — Their chemical constitution is quite unknown. The N seems to exist in two 
 distinct conditions, partly loosely combined, so as to yield ammonia readily when they are decom- 
 posed, and partly in a more fixed condition. According to Pfliiger, part of the N in living proteid 
 bodies exists in the form of cyanogen. The proteid molecule is very large, and is, very probably, 
 a complex one ; a small part of the molecule is composed of substances from the group of aromatic 
 bodies (which become conspicuous during putrefaction), the larger part of the molecule belongs to 
 the fatty bodies (during the oxidation of albumin, fatty acids especially are developed). Carbo- 
 hydrates may also appear as decomposition products (Krukenberg). For the decompositions during 
 digestion, see \ 170, and during putrefaction, \ 184. The proteids form a large group of closely- 
 related substances, all of which are, perhaps, modifications of the same body. When we remember 
 that the infant manufactures most of the proteids of its ever-growing body from the casein in milk, 
 this last view seems not improbable. 
 
 Characters. — Proteids, the anhydrides of peptones (§ 166), are colloids (fi 191), and, therefore, 
 do not diffuse easily through animal membranes; they are amorphous, and do not crystallize, and, 
 hence, are isolated with difficulty; some are soluble, others are insoluble, in water; are insoluble in 
 alcohol; rotate the ray of polarized light to the left; in a flame, they give the odor of burned horn. 
 Various metallic salts and alcohol precipitate them from their solution ; they are coagulated by 
 heat, mineral acids, and the prolonged action of alcohol. Caustic alkalies dissolve them (yellow), 
 and from this solution they are precipitated by acids. By powerful oxidizing agents they yield 
 carbamic acid, guanidin and volatile fatty acids. 
 
 Decompositions. — When acted upon in a suitable manner by acids and alkalies, they give rise 
 to the decomposition products — leucin (10-18 per cent.), tyrosin (0.25-2 per cent), asparaginic acid, 
 glutamic acid, and also volatile fatty acids, benzoic and hydrocyanic acids, and aldehydes of benzoic 
 and fatty acids; also, indo {Hlasiwetz, Habermann). Similar products are formed during pan- 
 creatic digestion ({! 170), and during putrefaction (§ 184). 
 
 Reactions. — (1) They are coagulated by nitric acid, and when boiled therewith, give & yellow, 
 the xanthoproteic reaction ; the addition of ammonia gives a deep orange color. 
 
 (2) Millon's reagent (nitrate of mercury with nitrous acid) ; when heated with this reagent 
 above 6o° C, they give a red, probably owing to the formation of tyrosin. [If the proteids 
 are present in large amount, a red precipitate occurs ; but if mere traces are present, only the 
 fluid becomes red.] 
 
 (3) The addition of a few drops of solution of cupric sulphate, and the subsequent addition of 
 caustic potash or soda, give a violet color, which deepens on boiling [the same color is obtained by 
 adding a few drops of Fehling's solution (biuret reaction).] 
 
 (4) They are precipitated by acetic acid and potassium ferrocyanide. 
 
 (5) When boiled with concentrated hydrochloric acid, they give a violet-red color. 
 
 (6) Sulphuric acid containing molybdic acid gives a blue color [Frohde). 
 
 (7) Their solution in acetic acid is colored violet with concentrated sulphuric acid, and shows the 
 absorption band of hydrobilirubin (Adamkiewicz). 
 
 (8) Iodine is a good microscopic reagent, which strikes a brownish-yellow, while sulphuric acid 
 and cane sugar give a purplish- violet (E. Schultze). 
 
NATIVE ALBUMINS, GLOBULINS AND ALBUMINATES. 409 
 
 [(9) When boiled with acetic acid and an equal volume of a concentrated solution of sodic sul- 
 phate, they are precipitated. This method is used for removing proteids from other liquids, as it 
 does not interfere with the presence of other substances. Saturation with sodio-magne 5 ic sulphate 
 precipitates the proteids, but not peptones.] 
 
 249. THE ANIMAL PROTEIDS AND THEIR CHARACTERS.— They have been 
 divided into classes : — 
 
 Class I. — Native Albumins. — Native albumins occur in a natural condition in the solids 
 and fluids of the body. They are soluble in water, and are not precipitated by alkaline carbonates, 
 NaCl, or by very dilute acids. Their solutions are coagulated by heat at 65°-73° C. Dried at 40° 
 C, they yield a clear, yellow, amber-colored, friable mass, " soluble albumin," which is soluble in 
 water. 
 
 (1) Serum albumin, whose chemico-physical characters are given in \ 32, and its physiological 
 properties at JS41. Almost all its salts may be removed from it by dialysis, when it is no longer 
 coagulated by heat [Schmidt). It is coagulated by strong alcohol, and is easily dissolved in strong 
 hydrochloric acid. When precipitated, it is readily soluble in strong nitric acid. It is not coagulated 
 when shaken up with ether. The addition of water to the hydrochloric solution precipitates acid 
 albumin. For its presence in urine, § 264. 
 
 (2) Egg albumin. Whi*n injected into the blood vessels or under the skin, or even when 
 introduced in large quantity into the intestine, part of it appears unchanged in the urine (g 192, 4, 
 and \ 264). When shaken with ether, it is precipitated. These two reactions serve to distinguish 
 it from (1). The specific rotation is 37.8 . Amount of S, 1.6 per cent. 
 
 (Metalbumin and Paralbumin have been found by Scherer in ropy solutions in ovarian cysts; 
 they are only partially precipitated by heat. The precipitate thrown down by the action of strong 
 alcohol is soluble in water. They are not precipitated by acetic acid, by acetic acid and potassium 
 ferrocyanide, by mercuric chloride, or by saturation with magnesium sulphate. Concentrated sul- 
 phuric acid and acetic acid give a violet color (Adamkiewicz). According to Hammarsten, met- 
 albumin is a mixture of paralbumin and other proteid substances. On being boiled with dilute sul- 
 phuric acid, they yield a reducing substance (? sugar)). 
 
 Class II. — Globulins. — They are native proteids, which are insoluble in distilled water, but 
 soluble in dilute saline solutions, sodium chloride of I per cent., and in magnesium sulphate. 
 These solutions are coagulated by heat, and are precipitated by the addition of a large quantity of 
 water. Most of them are precipitated from their sodium chloride solution by the addition of crystals 
 of sodium chloride, and also by saturating their neutral solution at 30 with crystals of magnesium 
 sulphate. When acted upon by dilute acids, they yield acid albumin, and by dilute alkalies, alkali 
 albumin. 
 
 (1) Globulin (Crystallin) is obtained by passing a stream of C0 2 through a watery extract of the 
 crystalline lens. 
 
 (2) Vitellin is the chief proteid in the yelk of egg. It is also said to occur in the chyle (?) and 
 in the amniotic fluid ( Weyl). Both the foregoing are not precipitated from their neutral solutions 
 by saturation with sodium chloride. 
 
 (3) Paraglobulin or Serum globulin ($ 29), and in urine, \ 264. 
 \aS Fibrinogen (§29). 
 
 (5) Myosin is the chief proteid in dead muscle. Its coagulation in muscle post-mortem consti- 
 tutes rigor mortis. If muscle be repeatedly washed, and afterward treated with a 10 per cent, 
 solution of sodium chloride, it yields a viscid fluid, which, when dropped into a large quantity of 
 distilled water, gives a white flocculent precipitate of myosin. It is also precipitated from its NaCl 
 solution by crystals of NaCl. For Kiihne's method of preparation, see \ 293. 
 
 (6) Globin [Preyer), the proteid residue of haemoglobin, \ 18. 
 
 Class III. — Derived Albumins (Albuminates). — (1) Acid Albumin or Syntonin. — When 
 proteids are dissolved in the stronger acids, e.g., hydrochloric, they hecome changed into acid 
 albumins. They are precipitated from solution by the addition of many salts (NaCl, Na 2 S0 4 ), or 
 by neutralization with an alkali, e.g., sodic carbonate, but they are not precipitated by heat. The 
 concentrated solution gelatinizes in the cold, and is redissolved by heat. Syntonin, which is 
 obtained by the prolonged action of dilute hydrochloric acid (2 per 1000) upon minced muscle, is 
 also an acid albumin. It is formed also in the stomach during digestion ($ 166, 1). According to 
 Soyka, the alkali- and acid albumins differ from each other only in so far as the proteid in the one 
 case is united with the base (metal) and in the other with the acid. 
 
 (2) Alkali Albumin. — It egg- or serum albumin be acted upon by dilute alkalies, a solution of 
 alkali albumin is obtained. Strong caustic potash acts upon white of egg, and yields a thick jelly 
 (Lieberkuhn). The solution is not precipitated by heat, but it is precipitated by the addition of an 
 acid. 
 
 (3) Casein is the chief proteid in milk (g 231). It is precipitated by acids and by rennet at 40° 
 C. In its characters it is closely related to alkali albuminate, but, according to O. Nasse, it contains 
 more N. It contains a large amount of phosphorus (0.83 per cent.). It may be precipitated from 
 milk by diluting it with several times its volume of water and adding dilute acetic acid, or by adding 
 magnesium sulphate crystals to milk and shaking vigorously. Owing to the large amount of phos- 
 
410 VEGETABLE PROTEID BODIES. 
 
 phorus which it contains, it is sometimes referred to the nucleo-albumins. When it is digested with 
 dilute HC1 (o.l per cent.) and pepsin at the temperature of the body, it gradually yields nuclein. 
 
 Class IV. — Fibrin. — For fibrin, see (S 27, and for the fibrin factors, \ 29. 
 
 Class V. — Peptones. — For peptones and propeptone [hemialbumose], see \ 166, I, and 
 in urine, § 264. 
 
 Class VI. — Lardacein and Other Bodies. — There fall to be mentioned the "yelk plates," 
 which occur in the yelk: Ichthin (cartilaginous fishes, frog); Ichthidin (osseous fishes); 
 Ichthulin (salmon); Emydin (tortoise — Valenciennes and Fremy); also the indigestible amy- 
 loid substance ( Virchow) or lardacein, which occurs chiefly as a pathological infiltration into 
 various organs, as the liver, spleen, kidneys and blood vessels. It gives a blue with iodine and 
 sulphuric acid (like cellulose), and a mahogany brown with iodine. It is difficult to change it into 
 an albuminate by the action of acids and alkalies. 
 
 Class VII. — Coagulated Proteids. — When any native albumins or globules are coagulated, 
 e.g., at 70 C, they yield bodies with altered characters, insoluble in water and saline solutions, but 
 soluble in boiling strong acids and alkalies, when they are apt to split up. They are dissolved 
 during gastric and pancreatic digestion, to produce peptones. 
 
 Appendix: Vegetable Proteid Bodies. — Plants, like animals, contain proteid bodies, 
 although in less amount. They occur either in solution in the juices of living plants or in the 
 solid form. In composition and reaction they resemble animal proteids. 
 
 [The characters of the proteids occurring in plants have not been sufficiently investigated to 
 generalize on the nature of the bodies themselves. As far as our knowledge at present extends, 
 they have a great resemblance to animal proteids. They have frequently been obtained in a 
 crystalline form (Radlkofer), e.g., from the seeds of the gourd (Grubler) and various oleaginous 
 seeds (Ritthausen). They occurin greatest bulk in the seeds of plants, aleurone grains being for 
 the most part composed of them.] 
 
 [As regards the kinds of proteid, the researches of late years (since 1877) nave shown that in 
 seeds, globulins and " vegetable peptone" form the greater proportion of the proteid constituents. 
 The existence of this " peptone," however, is denied ( Vines}, and other bodies similar in some par- 
 ticulars to peptones have been described, viz., albumoses ( Vines, Martin)."] 
 
 [Globulins. — Three varieties have been described as occurring in the seeds of plants: vegetable 
 myosin (Hoppe-Seyler), vitellin ( Weyl), and paraglobulin [Martin). They have practically the 
 same properties as those found in the animal kingdom : vegetable vitellin has. however, not been 
 sufficiently studied. Paraglobulin has been found in papaw juice {Martin). Myosin occurs in the 
 seeds of leguminosae, in flour and in the potato.] 
 
 [Albumin. — The existence of a body corresponding to egg- or serum albumin in the vegetable 
 kingdom is doubtful (Ritthausen). Such a body has been described in papaw juice (Martin)."] 
 
 [Vegetable Peptone : Albumoses. — A true peptone has not yet been recognized in plants : 
 what has been described as such is hemialbumose ( Vines). The existence of albumoses in the 
 vegetable kingdom is' probably widespread ; up to the present date they have been described as 
 occurring in the seeds of leguminosae, in flour, and in papaw juice. In the last, two forms occur, 
 called respectively a- and />-phytalbumose. The former, s-phytalbumose, agrees with the 
 hemialbumose described by Vines, being soluble in cold and boiling water ; giving also a biuret 
 reaction, and a precipitate by saturation with sodium chloride only in an acid solution. The latter, 
 /3-phytalbumose, is soluble in cold, but not in boiling, distilled water; hence it is precipitated by 
 heat. It is also readily thrown down by saturation with sodium chloride, and gives a faint biuret 
 reaction (Martin)."] 
 
 [Vegetable Casein is said to occur in the seeds of leguminosae ; and it is slightly soluble in 
 water, hut readily so in weak alkalies and in solutions of basic calcic phosphate. A solution of 
 this body is precipitated by acids and rennet. Two varieties have been described : (a) legumin, 
 in peas, beans, lentils (1805); acid in reaction, soluble in weak alkalies and very dilute HC1 or 
 acetic acid (Ernlwf, 180J) ; (6) conglutin, a very similar body occurring in hops and almonds 
 (Ritthausen). The existence of vegetable casein is denied ( Weyl, 1877 ; Vines, 1878 to 1880). 
 Vines states that both legumin and conglutin are artificial products, being formed from the globulins 
 present by the dilute alkali used in extraction of the proteids. This is denied by Ritthausen.] 
 
 [Gluten and Glutin. — Gluten is readily prepared from flour by washing and kneading it in a 
 muslin bag under a stream of water. So prepared it is yellowish- brown in color, very sticky, and 
 capable of being drawn out into long shreds. R is insoluble in water, soluble (but not completely) 
 by prolonged action in dilute acids and alkalies (.2 per cent. KHO and HC1). The prolonged 
 action of alcohol (80 to 85 per cent.) dissolves part of the substance of gluten ( Taddei, Liebig), 
 leaving a residue, called by Liebig plant fibrin and by Ritthausen gluten casein. The alcohol con- 
 tains gliadin (glutin), gluten fibrin and mucedin (Ritthausen). Gluten casein is readily soluble 
 in dilute alkalies, almost insoluble in dilute acetic acid, and quite insoluble in cold and boiling 
 water; the products of its decomposition, by heating with H 2 S0 2 , are leucin, tyrosin, glutamic and 
 asparaginic acids. The three bodies dissolved from glutin by alcohol differ chiefly in their solubility 
 in alcohol and water. Gluten fibrin, the least soluble, is coagulated by the action of absolute 
 alcohol ; it is readily soluble in dilute acids and alkalies, being precipitated by neutralization. 
 Gliadin (gluten, plant gelatin) may be prepared by boiling gluten with water : it deposits on cool- 
 
ALBUMINOIDS. 411 
 
 ing the solution. Though soluble in water at ioo° C. at first, it becomes insoluble by the prolonged 
 action of water at that temperature. It is, like gluten fibrin, soluble in dilute acids and alkalies. 
 Mucedin differs from gliadin in being less soluble in strong alcohol; it is considered by Ritthausen 
 as a modification of gluten fibrin. The existence of these several constituents of gluten has not 
 been definitely proved : they were first described by Ritthausen (1872). The formation of gluten 
 has been ascribed by Weyl to a ferment action similar to the formation of blood fibrin ; all attempts, 
 however, to isolate a ferment have proved fruitless. The water used in washing the flour in the 
 preparation of gluten contains hemialbumose ( Vines) and a globulin ( Weyl). Rye flour, as well as 
 wheaten, yields gluten under similar treatment with water.] 
 
 [Nitrogenous Crystalline Principles. — Leucin, tyrosin, asparagin, and glutamic acid, have 
 been found in the seeds of plants.] 
 
 250. (2) THE ALBUMINOIDS. — These substances closely resemble true proteids in their 
 composition and origin, and are amorphous non-crystalline colloids; some of them do not contain 
 S, but the most of them have not been prepared free from ash. Their reactions and decomposition 
 products closely resemble those of the proteids ; some of them produce, in addition to leucin and 
 tyrosin,, glycin and alanin (amido-propionic acid). They occur as organized constituents of the 
 tissues and also in fluid form. It is unknown whether they are formed by oxidation from proteid 
 bodies or by synthesis. 
 
 1. Mucin is the characteristic substance present in mucus. It contains no S. That obtained from 
 the submaxillary gland contains — C 52.31, H 7.22, N II 84, O 28.63. *' dissolves in water, mak- 
 ing it sticky or slimy, and can be filtered. It is precipitated by acetic acid and alcohol ; and the 
 alcohol precipitate is again soluble in water. It is not precipitated by acetic acid and ferrocyanide 
 of potassium, but HNO s and other mineral acids precipitate it (Scherer). It occurs in saliva (\ 146), 
 in bile, in mucous glands, secretions of mucous membranes, in mucous tissue, in synovia, and in 
 tendons (A. Rollett). Pathologically it occurs not unfrequently in cysts; in the animal kingdom, 
 especially in snails and in the skin of holothurians (Eichwald). It yields leucin and 7 per cent, of 
 tyrosin when it is decomposed by prolonged boiling with sulphuric acid. [The precipitate called 
 mucin has not always the same characters, and, in fact, it differs according to the animal from which 
 it is obtained (Landwehr) ] 
 
 2. Nuclein [Miescher, \ 198) — (C 29, H 49, N 9, P 3, O 22) — contains phosphoric acid, and is 
 slightly soluble in water, easily in ammonia, alkaline carbonates, strong HNO s ; it gives the biuret re- 
 action; no reaction with Millon's reagent; when decomposed it yields phosphorus. It occurs in the 
 nuclei of pus and blood corpuscles {\ 22), in spermatozoids, yelk-spheres, liver, brain, and milk, yeast, 
 fungi, and many seeds. It has resemblances to mucin, and is perhaps an intermediate product between 
 albumin and lecithin {Hoppe-Seyler). It is prepared by the artificial digestion of pus when it remains as 
 an indigestible residue ; acids precipitate it from an alkaline solution. It gives a feeble xanthoproteic re- 
 action; after the prolonged action of alkalies and acid, substances similar to albumin and syntonin are 
 formed. Hypoxanthin and guanin have been obtained as decomposition products from it (Kossel). 
 
 3. Keratin occurs in all horny and epidermic tissues (epidermic scales, hairs, nails, feathers) — 
 C So.3-52.5, H 6.4-7, N 15. 2-17, O 20.8-25, S 0.7-5 percent. — is soluble in boiling caustic alka- 
 lies, but swells up in cold concentrated acetic acid. When decomposed by H 2 S0 4 it yields 10 per 
 cent, leucin and 3.6 per cent, tyrosin. Neuro-keratin, \ 321. 
 
 4. Fibroin is soluble in strong alkalies and mineral acids, in ammonia-sulphate of copper ; when 
 boiled with H a S0 4 it yields 5 per cent, tyrosin, leucin, and glycin. It is the chief constituent of 
 the cocoons of insects and threads of spiders. 
 
 5. Spongin, allied to fibroin, occurs in the bath sponge, and yields, as decomposition products, 
 leucin and glycin (S/ade/er). 
 
 6. Elastin, the fundamental substance in elastic tissue, is soluble only when boiled in concen- 
 trated caustic potash — C 55-55.6, H 7.1-7.7, N 16.1-17.7, O 19.2-21.1 per cent. It yields 36-45 
 per cent, of leucin and ^ per cent, of tyrosin. 
 
 7. Gelatin (Glutin), obtained from connective tissues by prolonged boiling with water ; it gela- 
 tinize? in the cold— C 52.2-50.7, H 6.6-7.2, N 17. 9-18.8, S + O 23.5-25, (S 0.7 per cent.). [The 
 ordinary connective tissues are supposed to contain the hypothetical anhydride collagen , while the 
 organic basis of bone is called ossein.] It rotates the ray of polarized light strongly to the left. 
 By prolonged boiling and digestion it is converted into a peptone-like body (gelatin peptone), 
 which does not gelatinize ($ 161, I). [It swells up, but does not dissolve in cold water ; when dis- 
 solved in warm water, and tinged with Berlin blue or carmine, it forms the usual colored mass 
 which is employed by histologists for making fine transparent injections of blood vessels. ] A body 
 resembling gelatin is found in leuksemic blood and in the juice of the spleen (§ 103, 1). When 
 decomposed with sulphuric acid it yields glycin, ammonia, leucin, but no tyrosin. It gives insoluble 
 precipitates with mercuric chloride, and tannin. 
 
 8. Chondrin (Joh. Miiller) occurs in the matrix of hyaline cartilage and between the fibres in 
 fibro-cartilage. It is obtained from hyaline cartilage and the cornea by boiling. It occurs also in 
 the mantle of molluscs — C 49.5-50.9, H 6.6-7.1, N 14.4-14.9, S +0 27.2-29 (S 0.4 per cent.). 
 When boiled with sulphuric acid it yields leucin; with hydrochloric acid, and when digested, 
 chondro-glucose (Mezssner) ; it belongs to the glucosides, which contain N. When acted upon by 
 oxidizing reagents it is converted into gelatin (Brame). The substance which yields chondrin is 
 
412 
 
 ORGANIZED AND UNORGANIZED FERMENTS. 
 
 called chondrogen, which is perhaps an anhydride of chondrin. The following properties of gelatin 
 and chondrin are to be noted : Gelatin is precipitated by tannic acid, mercuric chloride, chlorine 
 water, platinic chloride, and alcohol, but not by acids, alum, or salts of silver, iron, copper, or lead ; 
 its specific rotation is = — 130 . [Compare these precipitants with those of albumin.] Chondrin 
 is precipitated by acetic acid and dilute sulphuric and hydrochloric acids, by alum , and by salts of 
 silver, iron, and lead; its specific rotation = — 213 . 
 
 9. The hydrolytic ferments have recently been called Enzymes by W. Kiihne, in order to 
 distinguish them from organized ferments, such as yeast. The enzymes, hydrolytic or organic fer- 
 ments, act only in the presence of water. They act upon certain bodies, causing them to take up a 
 molecule of water. They all decompose hydric peroxide into water and O. They are most active 
 between 30 and 35° C, and are destroyed by boiling, but when dry they may be subjected to a tem- 
 perature of ioo° without being destroyed. Their solutions, if kept for a long time, gradually lose 
 their properties and undergo more or less decomposition. > 
 
 (a) Sugar forming or diastatic ferment occurs in saliva (§ 148), pancreatic juice (j! 170), 
 intestinal juice (§ 183), bile {\ 180), blood {\ 22), chyle (\ 189), liver (\ 174), in human milk (| 231). 
 Invertin in intestinal juice {\ 183). 
 
 Almost all dead tissues, organic fluids, and even proteids, although only to a slight degree, may 
 act diastatically. Diastatic ferments are very generally distributed in the vegetable kingdom, 
 
 (b) Proteolytic, or Ferments which act upon Proteids. — Pepsin in gastric juice and in muscle 
 ({! 166), in vetches, myxomycetes ( Krukenberg), trypsin in the pancreatic juice (jj 170), a similar 
 ferment in the intestinal juice ($ 183), and urine (§ 264). 
 
 (c) Fat-decomposing in pancreatic juice (§ 170), in the stomach (§ 166). 
 
 (d) Milk-coagulating in the stomach (I 166), pancreatic juice (j! 170), and perhaps also in the 
 intestinal juice (?) — {W. Roberts). 
 
 [The importance of fermentive processes has already been referred to in detail under 
 ''Digestion." Ferments are bodies which excite chemical changes in other matter with which 
 they are brought into contact. They are divided into two classes : — 
 
 (1) Unorganized; soluble or non-living. 
 
 (2) Organized, or living.] 
 
 [Table showing the unorganized ferments present in the body, and their actions. 
 
 Fluid or Tissues, 
 
 Ferment. 
 
 Actions. 
 
 Saliva, 
 
 I. Ptyalin, (j! 148) 
 
 1. Pepsin, \ 
 
 2. Milk curdling 
 
 3. Lactic-acid ferment, . . 
 
 4. Fat splitting, j 
 
 Converts starcn chiefly into maltose. 
 
 Converts proteids into peptones in an 
 acid medium, certain by-products 
 being formed (\ 166I. 
 
 Curdles casein of milk. 
 
 Splits up milk sugar into lactic acid. 
 
 Splits up fats into glycerine and fatty 
 acids. 
 
 Gastric juice - 
 
 Pancreatic juice, . . . - 
 
 1 . Diastatic or amylopsin, . 
 
 2. Trypsin, -J 
 
 4. Fat splitting or steapsin, . 1 
 
 5. Milk curdling 
 
 Converts starch chiefly into maltose. 
 
 Changes proteids into peptones in an 
 alkaline medium, certain by-pro- 
 ducts being formed ($ 170). 
 
 Emulsifies fats. 
 
 Splits fats into glycerine and fatty 
 acids. 
 
 Curdles casein of milk. 
 
 Intestinal juice, ... 
 
 1. Diastatic, -j 
 
 2. Proteolytic 
 
 3. Invertin, 
 
 4. Milk curdling 
 
 Does not form maltose, but maltose is 
 
 changed into glucose ((j 183). 
 Fibrin into peptone (?). 
 Changes cane- into grape sugar. 
 (? in small intestine). 
 
 Blood, 
 
 Chyle 
 
 Liver, (?) 
 
 Milk 
 
 Most tissues, . . . 
 
 - Diastatic ferments. 
 
 
 Muscle, 
 
 > Pepsin and other ferments. 
 
 . . 
 
 Blood, 
 
 Fibrin-forming ferment. 
 
 (Modified from W. Roberts).] 
 
FATS. 413 
 
 [(i) The Unorganized Ferments are those mentioned in the preceding table. They seem to 
 be nitrogenous bodies, although their exact composition is unknown, and it is doubtful if they 
 have ever been obtained perfectly pure. They are produced within the body, in many secretions, 
 by the vital activity of the protoplasm of cells. They are termed soluble because they are 
 soluble in water, glycerine, and some other substances (g 148), while they can be precipitated by 
 alcohol and some other reagents. They do not multiply during their activity, nor is their 
 activity prevented by a certain proportion of salicylic acid. They are not affected by oxygen 
 subjected to the compression of many atmospheres {P. Bert). They are non-living. Their 
 other properties are referred to above.] 
 
 [(2) The Organized or living ferments are represented by yeast (g 235). Other living ferments 
 belonging to the schizomycetes, occurring in the intestinal canal, are referred to in \ 184. Yeast 
 causes fermentation by splitting up sugar into C0 2 and alcohol {\ 156), but this result only occurs 
 so long as the yeast is living. Hence, its activity is coupled with the vitality of the cells of the 
 yeast. If yeast be boiled, or if it be mixed with carbolic or salicylic acid, or chloroform, all of 
 which destroy its activity, it cannot produce the alcoholic fermentation. As yet no one has suc- 
 ceeded in extracting from yeast a substance which will excite the alcoholic fermentation. All the 
 organized ferments grow and multiply during their activity at the expense of the substances in 
 which they occur. Thus the alcoholic fermentation depends upon the " life " of the yeast. They 
 are said to be killed by oxygen subjected to the compression of many atmospheres (P. Bert). But 
 it is important to note that Hoppe-Seyler has extracted from dead yeast (killed by ether) an unor- 
 ganized ferment which can change cane sugar into grape sugar.] 
 
 10. Haemoglobin, the coloring matter of blood, which, in addition to C, H, G, N, and S, con- 
 tains iron, may be taken with the albuminoids (§ ir). 
 
 (3) Glucosides containing Nitrogen. — In addition to chondrin, the following glucosides con- 
 taining nitrogen, when subjected to hydrolytic processes, may combine with water, and form sugar 
 and other substances : — 
 
 Cerebrin (§ 322) = C 5 ,H 110 N 2 O 25 (GeogAegan). 
 
 Protagon — C 66.29, H 10.69, N 2.39, P 1.068 per cent. — occurs in nerves, and contains phos- 
 phorus ($ 322). 
 
 Chitin, 2(C 15 H 26 N 2 O 10 ), is a glucoside, containing nitrogen, and occurs in the cutaneous cov- 
 erings of arthropoda, and also in their intestine and trachea ; it is soluble in concentrated acids, e.g., 
 hydrochloric or nitric acid, but insoluble in other reagents. According to Sandwick, chitin is an 
 amin-derivative of a carbohydrate with the general formula n(Cj 2 H 2 ,,0; ). The hyalin of worms 
 is closely related to chitin. (Solanin, amygdalin (§ 202), and salicin, etc., are glucosides of the 
 vegetable kingdom. ) 
 
 (4) Coloring Matters containing Nitrogen. — Their constitution is unknown, and they occur 
 only in animals. They are in all probability derivatives of haemoglobin. They are — ( I ) haematin 
 (g 18, A), myo-haematin (g 232, \ 292, a), and haematoidin ({> 20). (2) Bile pigments (g 177, 
 3). (3) Urine pigments (except Indican). (4) Melanin — C 44.2, H 3, N 9.9, O 42.6 — or the 
 black pigment, which occurs partly in epithelium (choroid, retina, iris, and in the deep layers 
 of epidermis in colored races) and partly in connective-tissue corpuscles (Lamina fusca of 
 the choroid). 
 
 * II. ORGANIC ACIDS FREE FROM NITROGEN.— (1) The fatty acids, with the for- 
 mula C n H 2n .iO(OH), occur in the body partly free and partly in combination. Free volatile fatty 
 acids occur in decomposing cutaneous secretions (sweat). In combination, acetic acid and caproic 
 acid occur as amido-compounds in glycin ( = arnido-acetic acid), and leucin ( = amido-caproic 
 acid). More especially do they occur united with glycerine to form neutral fats, from which the 
 fatty acid is again set free by pancreatic digestion (§ 170, III). 
 
 (2) The acids of the acrylic acid series, with the formula C n H 2n . 3 0(HO), are represented 
 in the body by one acid, oleic acid, which in combination with glycerine yields the neutral 
 fat olein. 
 
 251. FATS. — (1) Neutral fats occur very abundantly in animals, but they also occur in all 
 plants; in the latter more especially in the seeds (nuts, almonds, cocoanut, poppy), more rarely 
 in the pericarp (olive) or in the root. They are obtained by pressure, melting, or by extracting 
 them with ether or boiling alcohol. They [e.g., tristearin, C 5 ,H ]10 O 6 ] contain much less 
 O than the carbohydrates, such as sugar and starch ; they give a greasy spot on paper, and 
 when shaken with colloid substances, such as albumin, they yield an emulsion. When 
 treated with superheated steam, or with certain ferments (p. 412, c), they take up water 
 and yield glycerine and fatty acids, and if the latter be volatile they have a rancid odor. 
 Treated with caustic alkalies they also take up water, and are decomposed into glycerine and 
 fatty acids ; the fatty acid unites with the alkali and forms a soap, while glycerine is set free. 
 The soap solution dissolves fats. 
 
 Glycerine is a tri-atomic alcohol, C 3 H S (OH) 3 , and unites with (1) the following monobasic 
 fatty acids (those occurring in the body are printed in italics) : — 
 
414 
 
 ACIDS. 
 
 Acids. 
 
 Formic . . 
 Acetic , . 
 Propionic . 
 Butyric . . 
 [Isobutyric 
 Valerianic 
 Caproic . . 
 
 CH 2 2 
 . C 2 H t 2 
 . C 3 H 6 2 
 
 C 4 H 8 2 
 
 ■ C 4 H 8 2 ] 
 
 ■ C 5 H lo02 
 
 , C 6 H 12 2 
 
 Acids. 
 CEnanthylic . 
 Caprylic , . 
 Pelargonic . 
 Capric . . . 
 Laurostearic 
 Myristic , . 
 Palmitic . . 
 
 C 8 H 16°2 
 C 9 H 18°2 
 ^'10"20^'2 
 
 C 12 H 24 2 
 
 C 14 H 28°2 
 ^'16"32^'2 
 
 Acids. 
 
 [Margaric, . . C lv H 84 2 
 is a mixture of 
 13 and 14.] 
 Stearic . . . . C 18 H 36 2 
 Arachinic . . C 20 H 40 O 2 
 Hyanic . . . C 25 H B0 O 2 
 
 Cerotinic 
 
 ^27" 64 2 
 
 The acids form a homologous series with the formula C n H2 n .!0(OH). With every CH 2 added 
 their boiling point rises 19°. Those containing most carbon are solid and non- volatile ; those con- 
 taining less C (up to and including 10) are fluid like oil, have a burning acid taste, and a rancid 
 odor. 
 
 The earlier members of the series may be obtained by oxidation from the latter, by CH 2 being 
 removed, while C0 2 and H 2 are formed; thus, butyric acid is obtained from propionic acid. 
 
 Nos. 13 and 14 are found in human and animal fat, less abundant and more inconstant are 12, 
 ii, 6, 8, 10, 4. Some occur in sweat (§ 287) and in milk (<j 231). Many of them are developed 
 during the decomposition of albumin and gelatin. Most of the above (except 15 to 17) occur in 
 the contents of the large intestine ($ 185). 
 
 (.2) Glycerine also unites with the monobasic oleic acid, which also forms a series, whose gen- 
 eral formula is C„H 2 „. 3 0(OH) ; and they all contain 2H less than the corresponding members of the 
 fatty acid series. The corresponding fatty acids can be obtained from the oleic acid series, and vice 
 versa. Oleic acid (olein-elainic acid), C 18 H 84 2 , is the only one found in the organism; united 
 with glycerine, it forms the fluid fat, olein. The fat of new-born children contains more glycerine 
 of palmitic and stearic acid than that of adults, which contains more glyceride of oleic acid. Oleic 
 acid also occurs united with alkalies (in soaps), and (like some fatty acids) in the lecithins (§ 23). 
 J If lecithin be acted on with barium hydrate, we obtain insoluble stearic, or oleic, or palmitic acids 
 and barium oleate, together with dissolved neurin (§ 322, b) and baric glycerin phosphate. It ap- 
 pears as if there were several lecithins, of which the most abundant are the one with stearic acid 
 and that with palmitin -+- oleic acid radicle {Diakonow). Lecithin occurs in the blood corpuscles 
 (j! 23), semen, nerves, while neurin is constantly present in fungi. 
 
 The neutral fats' [palmitin, stearin (both solid), and olein (fluid)], the glycerides of fatty acids, 
 and of oleic acid, are triple ethers of the tri-atomic alcohol glycerine. 
 
 With the neutral fats may be associated glycerin- phosphoric acid, and acid glycerin ether, 
 formed by the union of glycerine and phosphoric acid, with the giving off of a molecule of water 
 (C 3 H 9 PO e ) ; it is a decomposition product of lecithin (§ 23). 
 
 (3) The glycolic acids (acids of the lactic acid series) have the formula C„H 2n . 2 0(OH) 2 . 
 They are formed by oxidation from the fatty acid series by substituting OH (hydroxyl) for one atom 
 of H of the fatty acids. Conversely, fatty acids may be obtained from the glycolic acids. The fol- 
 lowing acids of this seiies occur in the body : — 
 
 («) Carbonic acid (oxy-formic acid), CO(OH) 2 ; in this form, however, it only makes salts. 
 Free carbonic acid or carbon dioxide is an anhydride of the same = C0 2 . 
 
 (i) Glycolic acid (oxy-acetic acid), C 2 H 2 0(0H) 2 , does not occur free in the body. One of 
 its compounds, glycin (glycocoll, amido-acetic acid, or gelatin sugar) occurs as a conjugate acid, 
 viz., as glycocholic acid in the bile (g 1774 2), and as hippuric acid in the urine (§ 260). Glycin 
 exists in complex combination in gelatin. 
 
 (c) Lactic Acid (oxy-propionic acid), C 3 H 4 0(0H) 2 , occurs in the body in two isomeric forms : ' 
 I. The ethylidene-lactic acid, which occurs in tw<5 modifications — as the right rotary sarcolactic acid 
 (paralactic), a metabolic product of muscle; and as the ordinary optically inactive product of 
 " lactic fermentation," which occurs in gastric juice, in sour milk (sauerkraut, acid cucumber), and 
 can be obtained by fermentation from sugar (g 184). 2. The isomer, ethylene-lactic acid, occurs in 
 the watery extract of muscles (^ 293). 
 
 {d) Leucic Acid (oxy-caproic acid), C 6 H 12 3 , does not occur as such, but only in the form of 
 one of its derivatives, leucin (amido caproic acid), as a product of the metabolism in many tissues, 
 and is formed during pancreatic digestion ({S 170, II). Leucic acid may be prepared from leucin, 
 and glycolic acid from glycin, by the action of nitrous acid. 
 
 (4) Acids of the Oxalic Acid or Succinic Acid Series, having the formula Cj,H 2 „. 4 2 (OH) 2 , 
 are bi-basic acids, which are formed as completely oxidized products by the oxidation of fatty acids 
 and glycolic acid, water being removed ; and it is important to note their origin from substances 
 rich in carbon, e.g., fats, carbohydrates, and proteids. 
 
 (a) Oxalic Acid, C 2 2 (OH) 2 , arises from the oxidation of glycol, glycin, cellulose, sugar, 
 starch, glycerine, and many vegetable acids — it occurs in the urine as calcium oxalate (<j 260). 
 
 (6) Succinic Acid, C 4 H 4 2 (0H) 2 , has been found in small amount in animal solids and 
 fluids ; spleen, liver, thymus, thyroid ; in the fluids of echinococcus, of hydrocephalus, and of hydro- 
 cele, and more abundantly in dog!s urine after fatty and flesh food ; in rabbit's urine after feeding 
 with yellow turnips. It is also formed in small amount during alcoholic fermentation (g 150). 
 
THE CARBOHYDRATES. 415 
 
 (5) Cholalic Acids in the bile ({j 177) and in the intestine (g 182). 
 
 (6) Aromatic Acids contain the radicle of benzol. Benzoic acid (== phenylformic acid) 
 occurs in urine united with glycin, as hippuric acid (J 260). 
 
 III. ALCOHOLS. — Alcohols are those bodies which originate from carbohydrates, in which 
 the radicle hydroxyl (HO) is substituted for one or more atoms of H. They may be regarded as 
 
 water, „ >0, in which the half of the H is replaced by a CH compound. Thus, C 2 H 6 (ethyl- 
 
 hydrogen) passes into ! j, s J-0 (ethy lie alcohol). 
 
 c w ^ 
 (a) Cholesterin, 26 u 43 f O, is a true monatomic alcohol, and occurs in blood, yelk, brain, 
 
 bile ((J 177, 4), and generally in vegetable cells, 
 f OH 
 
 (i) Glycerine, C.H 6 -j OH, is a tri-atomic alcohol. It occurs in neutral fats united with fatty 
 I. OH 
 acids and oleic acid ; it is formed by the splitting up of neutral fats during pancreatic digestion 
 l§ 170, III), and during alcoholic fermentation (§ 150). 
 
 (c) Phenol (= phenylic acid, carbolic acid, oxybenzol) (J 184, III). 
 
 \d) Pyrokatechin (= dioxybenzol) (§ 252). 
 
 («) The Sugars are closely related to the alcohols, and they may be regarded as polyatomic 
 alcohols. Their constitution is unknown. Together with a series of closely-related bodies they 
 form the great group of the carbohydrates, some of which occur in the animal body, while others 
 are widely distributed in the vegetable kingdom. 
 
 252. THE CARBOHYDRATES.— These substances, which occur in plants and animals, 
 have received their name, because in addition to C (at least 6 atoms), they contain H and O, in the 
 proportion in which these occur in water. They are all solids, chemically indifferent, and without 
 odor. They have either a sweet taste (sugars), or can be readily changed into sugars by the action 
 of dilute acids ; they rotate the ray of polarized light either to the right or left ; as far as their con- 
 stitution is concerned, they may be regarded as fatty bodies, as hexatonic alcohols, in which 2II are 
 wanting. 
 
 They are divided into the following group : — 
 
 1. Division. — Glucoses (C 6 H 12 6 )—- (1) Grape sugar (glucose, dextrose, or diabetic sugar) 
 occurs in minute quantities in the blood, chyle, muscle, liver (?), urine, and in large amount in the 
 urine in diabetes mellitus (g 175). It is formed by the action of diastatic ferments upon other 
 carbohydrates, during digestion. In the vegetable kingdom, it is extensively distributed in the 
 sweet juices of many fruits and flowers (and thus it gets into honey). It is formed from cane sugar, 
 maltose, dextrin, glycogen, and starch, by boiling with dilute acids. It crystallizes in warty masses 
 with one molecule of water of crystallization ; unites with bases, salts, acids, and alcohols, but is 
 easily decomposed by bases; it reduces many metallic oxides (§ 149). Fresh solutions have a 
 rotatory power of -)- 106 . By fermentation with yeast it splits up into alcohol and C0 2 (§ 150) ; 
 with decomposing proteids it splits into two molecules of lactic acid (§ 184, I); the lactic acid splits 
 up, under the same conditions in alkaline solutions, into butyric acid, C0 2 and H. For the qualita- 
 tive and quantitative estimation of glucose, see \ 149 and \ 150. In alcoholic solution, it forms 
 very insoluble compounds with chalk, barium, and potassium, and it also forms a crystalline com- 
 pound with common salt (Estimation, \ 150). 
 
 (2) Galactose, obtained by boiling milk sugar (lactose) with dilute mineral acids ; it crystallizes 
 readily, is very fermentable, and gives all the reactions of glucose. When oxidized with nitric acid 
 it becomes transformed into mucic acid. Its specific rotatory power = -|- 88.08°. 
 
 (3) Laevulose (left-fruit-, invert-, or mucin sugar) occurs as a colorless syrup in the acid juices 
 of some fruits and in honey ; is non-crystallizable, and insoluble in alcohol ; specific rotatory power 
 = — 106 . It is formed normally in the intestine (§ 183), and occurs rarely as a pathological pro- 
 duct in urine. 
 
 II. Division contains carbohydrates with the formula C 12 H 22 11; and which may be regarded 
 as anhydrides of the first division — I. Milk sugar or lactose occurs only in milk, crystallizes in 
 cakes (with 1 molecule of water) from the syrupy concentrated whey; it rotates polarized light to 
 the right = + 59.3, and is much less soluble in water and alcohol than grape sugar. When boiled 
 with dilute mineral acids it passes into galactose, and can be directly transformed into lactic acid 
 only by fermentation ; the galactose, however, is capable of undergoing the alcoholic fermentation 
 with yeast (Koumis preparation, \ 232). For its quantitative estimation, see Milk (J 231). Rare 
 in urine (J 267). 
 
 2. Maltose (C^H^On) + H 2 (CC Sullivan) has I molecule of water less than grape sugar 
 (Cj 2 H 24 0! 2 ), is iormed during the action of a diastatic ferment, such as saliva upon starch (g 148) ; 
 is soluble in alcohol, right rotatory power = 150° ; it is crystalline, while its reducing power is only 
 two-thirds that of dextrose. 
 
 (3. Saccharose (cane sugar) occurs in sugar cane and some plants, it does not reduce a solution 
 of copper, is insoluble in alcohol, is right rotatory, and not capable of fermentation. When boiled 
 
416 
 
 THE CARBOHYDRATES. 
 
 with dilute acids, it becomes changed into a mixture of easily fermentable glucose (right rotatory) 
 and laevulose (invert sugar, \ 183, 5, and \ 184, 1, 6), which ferments with difficulty and is left 
 rotatory (\ 183). When oxidized with nitric acid, it passes into glucic acid and oxalic acid.) 
 
 (4. Melitose, from Eucalyptus-manna ; Melezitose, from Larch-manna ; Trehalose (Mycose), 
 from Ergot ; are all right rotatory, and do not reduce alkaline cupric solutions.) 
 
 III. Division contains carbohydrates, with the formula, C 6 Hi O 6 , which may be regarded as 
 anhydrides of the second division. 
 
 1. Glycogen, with a rotatory power of 21 1° (Boim, Hofmann, Kiih\ does not reduce cupric 
 oxide. It occurs in the liver ($ 174), muscles, many embryonic tissues, the embryonic area of the 
 chick (Kith), in normal and pathological epithelium (Schiele); in diabetic persons it is widely dis- 
 tributed ; brain, pancreas, and cartilage ; and in the spleen, pancreas, kidney, ovum, brain, and 
 blood, together with a small amount of glucose {Pavy). It also occurs in the oyster and some of 
 the molluscs (Bizio), and indeed in all tissues and classes of the animal kingdom. 
 
 2. Dextrin was discovered by Limpricht in the. muscles of the horse. It is right rotatory = 4- 
 J38 , soluble in water, and forms a very sticky solution, from which it is precipitated by alcohol or 
 acetic acid ; it is tinged slightly red with iodine. It is formed in roasted starch (hence it occurs in 
 large quantity in the crust of bread — see Bread, \ 234), by dilute acids, and in the body by the 
 action of ferments (g 148). It is formed from cellulose by the action of dilute sulphuric acid. It 
 occurs in beer, and is found in the juices of most plants. 
 
 (3. Amylum or Starch occurs in the " mealy " parts of many plants, is formed within vegetable 
 cells, and consists of concentric layers with an excentric nucleus (Fig. 225). The diameter and 
 characters of starch grains vary greatly with the plant from which they are derived, as indicated in 
 the above illustration. At 72 C. it swells up in water and forms mucilage ; in the cold, iodine 
 colors it blue. Starch grains always contain more or less cellulose and a substance which is colored 
 red with iodine (erythrogranulose) (J 148). It and glycogen are transformed into dextrose by cer- 
 
 Fig. 225. 
 
 «, West Indian arrowroot ; c, Tahiti arrowroot ; d, Potato starch. 
 
 tain digestive ferments in the saliva, pancreatic and intestinal juices, and artificially by boiling with 
 dilute sulphuric acid.) 
 
 (4. Gum, C 10 H 20 O, , occurs in vegetable juices (specially in acacise and mimosas), is partly 
 soluble in water (arabin), partly swells up like mucin (bassorin), also in the salivary glands, mucous 
 tissue, lungs, and urine. Alcohol precipitates it. It is fermentable, and Vhen boiled with dilute 
 acids yields a reducing sugar.) 
 
 (5. Inulin, a crystalline powder occurring in the root of chicory, dandelion, and specially in the 
 bulbs of the dahlia ; it is not colored blue by iodine.) 
 
 (6. Lichenin occurs in the intercellular substance of Iceland moss (Cetraria islandica) and algse; 
 is transformed into glucose by dilute sulphuric acid.) 
 
 (7. Paramylum occurs in the form of granules resembling starch, in the infusoriar., Euglena 
 viridis.) 
 
 (8. Cellulose occurs in the cell walls of all plants (in the exo-skeleton of arthropoda, and the 
 skin of snakes) ; soluble only in ammonio-cupric oxide ; rendered blue by sulphuric acid and iodine. 
 Boiled with dilute sulphuric acid, it yields dextrin and glucose. Concentrated nitric acid mixed 
 with sulphuric acid changes it (cotton) into nitro- cellulose (gun cotton) C 6 H 7 (N0 2 ) 3 5 , which 
 dissolves in a mixture of ether and alcohol and forms collodoin.) 
 
 (9. Tunicin is a substance resembling cellulose, and occurs in the integument of the Tunicata 
 or Ascidians.) 
 
 IV. Division contains the carbohydrates which do not ferment. 
 
 1. Inosit (phaseo-mannit, muscle sugar) occurs in muscle {Scherer), lung, liver, spleen, kidney, 
 brain of ox, human kidney ; pathologically in urine and the fluid of echinococcus. In the vegetable 
 kingdom, in beans (leguminosse), and the juice of the grape. It is an isomer of grape sugar; 
 optically it is inactive, crystallizes in warts with two molecules of water, in long monoclinic crystals ; 
 it has a sweet taste, is insoluble in water, does not give Trommer's reaction, is capable of undergoing 
 
HISTORICAL. 417 
 
 only the sarcolactic acid fermentation. (Nearly allied are Sorbin, from sorbic acid — Scyllit, from 
 the intestines of the hag -fish and skate — and Eukalyn, arising from the fermentation of melitose.) 
 
 IV. DERIVATIVES OF AMMONIA AND THEIR COMPOUNDS.— The am- 
 monia derivatives are obtained from the proteids, and are decomposition products of their meta- 
 bolism. 
 
 (i) Amines, i. e., compound ammonias which can be obtained from ammonia (NH 3 ), or from 
 ammonium hydroxide (NH 4 — OH), by replacing one or all the atoms of H by groups of carbo- 
 hydrates (alcohol radicals). The amine derived from one molecule of ammonia is called monamine. 
 We are only acquainted with — 
 
 HI CH 3 1 
 
 H V N Methylamine and Tri-Methylamine CH 3 V N, 
 ■CH,J CH.-J 
 
 as decomposition products of cholin (neurin) and of kreatin. Neurin occurs in lecithin in a very 
 complex combination (see Lecithin, p. 414, and also \ 23). 
 
 (2) Amides, i. e., derivatives of acids, which have exchanged the hydroxyl (HO) of the acids 
 for NH 2 . Urea, CO(NH 2 ) 2 , the biamid of C0 2 , is the chief end product of the metabolism of 
 the nitrogenous constituents of our bodies (see Urine, \ 256). Carbon dioxide containing water 
 = CO(OH) 2 ; in it both OH are replaced by NH 2 — thus we get CO(NH 2 ) 2 , urea. 
 
 (3) Amido acids, i. e., nitrogenous compounds, which show partly the character of an acid and 
 partly that of a weak base, in which the atoms of H of the acid radicle are replaced by NH 2 , or by 
 the substituted ammonia groups. 
 
 (a) Glycin (or amido-acetic acid, glycocoll, gelatin sugar, \ 177, 2) is formed by boiling gelatin 
 with dilute sulphuric acid. It has a sweet taste (gelatin sugar), behaves as a weak acid, but also 
 unites with acids as an amine base. It occurs as glycin -4- benzoic acid = hippuric acid in urine 
 (\ 260); and also as glycin -f- cholalic acid = glycocholic acid in bile [\ 177). (b) Leucin — 
 (g 170) = amido-caproic acid, (c) Serin — ( = ? amido-lactic acid), obtained from silk gelatin. 
 (d) Asparaginic acid — (amido-succinic acid) ; and (e) Glutaminic acid, obtained by the splitting 
 up of proteids (§ 170). Other amido acids are — {/) Cystin = amido-lactic acid, in which O is 
 replaced by S (\ 268). (g) Taurin— (§ 177), amido-ethyl-sulphuric acid occurs (except in certain 
 glands) chiefly in combination with cholalic acid, as taurocholic acid in bile. Tyrosin (parahydro- 
 oxyphenyl-amido-propionic acid), an amido acid of unknown constitution, occurs along with leucin 
 during pancreatic digestion (g 170), is a decomposition product of proteids, and occurs plentifully 
 in the urine in acute yellow atrophy of the liver ($ 269). 
 
 To the amido acids are related — (a) Kreatin in muscle, brain, blood, urine, regarded as methyl- 
 uramido-acetic acid (C 4 H 9 N s 2 ). It has been prepared artificially. When boiled with baryta 
 water, it takes up H 2 0, and splits into urea— and (b) Sarkosin (C 3 H 7 N0 2 ), methyl-amido-acetic 
 acid. When boiled with water, heated with strong acids, in the presence of putrefying substances, 
 krealin gives off water, and is changed into kreatinin (C 4 H,N 3 0). This strong base can be 
 rechanged by alkalies into kreatin. 
 
 (4) Ammonia Derivatives of Unknown Constitution. — Uric acid (<S 258) ; allantoin 
 (\ 260) is formed by the oxidation of uric acid by means of potassium permanganate ; cyanuric 
 acid in dog's urine; inosinic acid in muscle; guanin in traces in the liver and pancreas, in 
 guano, the excrements of spiders, in the skin of amphibia and reptiles, in the silver sheen of many 
 fishes {A. Ewald and Krukenberg) ; by oxidation it yields urea ; hypoxanthin or sarkin occurs 
 along with xanthin in many organs and in urine. Kossel prepared hypoxanthin from nuclein by 
 prolonged boiling of the latter. It may be obtained from fibrin by putrefaction, by gastric and 
 pancreatic digestion, and by dilute acids {Salomon, H. Krause, Chittenden); xanthin is prepared 
 by oxidation from hypoxanthin. It occurs very rarely in the form of a urinary calculus. Para- 
 xanthin in urine, and a similar body, carnin, in flesh (g 233). 
 
 Aromatic Substances. — I. Monatomic phenols — (a) Phenol (hydroxyl of benzol) in the 
 intestine (§ 184). Phenyl-sulphuric acid in urine [\ 262). (b) Kresol, in the form of orthokresol 
 and parakresol, united with sulphuric acid, occur in urine ($ 262). 2. Diatomic phenols — (a) 
 pyrokatechin united with sulphuric acid in urine (\ 262). 3. Aromatic oxyacids — (a) Hydro- 
 paracumaric acid ; (b) Paraoxyphenylacetic acid in urine (| 562). 4. Indol and skatol in the 
 intestine (f! 184), conjoined with sulphuric acid in urine (§ 262). 
 
 253. HISTORICAL — According to Aristotle, the organism requires food for three purposes — 
 for growth, for the production of heat, and to compensate for the loss of the bodily excreta. The 
 formation of heat takes place in the heart by a process of concoction, the heat so formed being 
 distributed to all parts of the body by means of the blood, while the respiration is regarded 
 as an act whereby the body is cooled. Galen accepted this view in a somewhat modified form ; 
 according to him, the metabolic processes may be compared to the processes going on in a lamp ; 
 the blood represents the oil ; the heart, the wick ; the lungs, the fanning apparatus. According to 
 the view of the iatrochemical school [van Belmont), the metabolic processes of the body are fer- 
 mentations, whereby the food is mixed with the juices of the body. Since the middle of the seven- 
 teenth century [Boyle), the knowledge of the metabolic processes has followed the development of 
 chemistry. A. v. Haller regarded heat as due to chemical processes — the food continually supplying 
 27 
 
418 HISTORICAL. 
 
 the waste which is excreted from the body. After the discovery of oxygen (1774, by Priestley and 
 Scheele), Lavoisier formulated the theory of combustion in the lungs, whereby carbonic acid and 
 water were formed. Mitscherlich compared the decomposition processes in the living body with 
 putrefactive processes. Magendie was the first to emphasize the difference between nitrogenous 
 and non-nitrogenous foods, and he showed that the latter alone were not able to support life. Even 
 gelatin alone is not sufficient for this purpose. The greatest advance in the theory of nutrition was 
 made by J. v. Liebig, who laid the foundation of our present knowledge of this subject. According 
 to Liebig, foods may be divided into two classes, viz., the " plastic," suitable for the construction 
 of the organism, and the " respiratory," for the maintenance of the temperature ; to the former 
 class he referred the albuminates or proteids, to the latter, the non-nitrogenous carbohydrates and 
 fats (p. 389). Among recent observers, the Munich School, as represented by v. Bischoff, v. Petten- 
 kofer, and v. Voit, has done most to give us an exact knowledge of this department of physiology. 
 
the Secretion of Urine. 
 
 254. STRUCTURE OF THE KIDNEY.— [Capsule.— The kidney is 
 
 a compound tubular gland, and is invested by a thin, tough, fibrous capsule, easily 
 Stripped off from the substance of the organ, to which it is attached by fine pro- 
 cesses of connective tissue and blood vessels.] 
 
 [Naked Eye Appearances. — On dividing the kidney longitudinally from the hilum to its outer 
 border, and examining the cut surface with the naked eye, we observe the parenchyma of the 
 
 Fig. 226. 
 
 Boundary layer \ 
 of medulla. j 
 
 Papillary portion 1 
 of medulla. j 
 
 Transverse section') 
 of tubules in >- 3. 
 boundary layer. J 
 
 Fat of renal sinus. 4. 
 
 Transversely "| 
 
 coursing medullary > 
 rays. j 
 
 Artery. 5. 
 
 1" Labyrinth. 
 
 i' Medullary rays. 
 
 MEDULLA. 
 
 CORTEX. 
 
 Renal calyx. 
 
 Ureter. 
 
 (Branch of renal 
 I artery. 
 
 Artery. 
 
 Longitudinal section through the kidney ( Tyson, after Henle). 
 
 kidney, consisting of an outer cortical and an inner medullary, or pyramidal portion, the latter 
 composed of about twelve conical papillae, or Pyramids of Malpighi, with their apices directed 
 toward the pelvis of the organ, and embraced by the calices of the pelvis of the kidney (Fig. 226). 
 The medullary portion is further subdivided into the boundary layer of Ludwig and the papillary 
 portion. According to Klein, the relative proportions of these three parts are — cortex, 3.5 ; 
 boundary layer, 2.5 ; and papillary portion, 4. The cortex has a light-brawn color, and when torn, 
 it presents a slightly granular aspect, with radiating lines or striae running at regular distances. The 
 granules are due to the presence of the Malpighian corpuscles, and the strise to the medullary rays. The 
 
 419 
 
420 
 
 COURSE AND STRUCTURE OF THE TUBULES. 
 
 boundary zone is darker, and often purplish in color. It is striated with clear and red lines alternating 
 with opaque ones, the former being blood vessels and the latter uriniferous tubules. The papillary zone 
 is nearly white arid uniformly striated, the striae converging to the apex of the pyramid. The me- 
 dulla is much denser and less friable than the cortex, owing to the presence of a large amount of 
 connective tissue between the tubules. The bundles of straight tubes of the medulla may be traced 
 at regular intervals, running outward into the cortex, constituting medullary rays, which become 
 smaller as they pass outward in the cortical zone, so that they are conical, and form the pyramids 
 of Ferrein (Fig. 227, PF). The portion of the cortex lying between the medullary rays is known 
 as the labyrinth, from the complicated arrangement of its tubules.] 
 
 [Size, Weight. — The adult kidney is about 11 centimetres (4.4 inches) in length, 5 centimetres 
 (2 inches) wide, and .75 centimetres (.3 inches) in thickness, It weighs, in the male, 113.5 to 
 170 grms. (4 to 6 oz.), in the female, 113. 5 to 156 grms. (4 to $yi oz.). The width of the cortex 
 is usually 5 to 6 millimetres (\ to \ inch — Tyson).'] 
 
 I. The uriniferous tubules all arise within the labyrinth of the cortex by 
 means of a globular enlargement, 200 to 300 fi [y^ to -j^- inch] in diameter, 
 
 Cortex. 
 
 Boundary or 
 marginal zone. 
 
 K} Papillary zone. 
 
 Longitudinal section of a Malpighian pyramid. PF, pyramids of Ferrein ; R A, branch of renal artery ; R V, lumen 
 of a renal vein receiving an interlobular vein ; VR, vasa recta ; PA, apex of a renal papilla ; b f b, embrace the 
 bases of the renal lobules. 
 
 called Bowman's capsule (Figs. 228, 229), and, after pursuing a complicated 
 course, altering their direction, diameter and structure, and being joined by other 
 tubules, they ultimately form large collecting tubes, which terminate by minute 
 apertures — visible with the aid of a hand lens — on the apices of the papillae pro- 
 jecting into the calices of the kidney. Each urinary tubule is composed of a 
 homogeneous membrana propria, lined by epithelial cells, so as to leave a 
 lumen for the passage of the urine from the Malpighian corpuscles to the pelvis 
 of the kidney. The diameter and direction of the tubules vary, and the epithe- 
 lium differs in its characters at different parts of the tube, while the lumen also 
 undergoes alterations in its diameter. 
 
 Course and Structure of the Tubules. — In the labyrinth of the cortex, 
 tubules arise in the spherical enlargement known as Bowman's capsule (Fig. 
 
COURSE OF THE TUBULES. 
 
 421 
 
 228, 1), which invests (in the manner presently to be described) the tuft of capil- 
 lary blood vessels called a glomerulus or Malpighian corpuscle. By means 
 of a short and narrow neck (2) the capsule becomes continuous with a convoluted 
 tubule, x in Fig. 229 {Bowman). This tubule is of considerable length, forming 
 many windings in the cortex (Fig. 228, 3) ; the first part of it is 4.5 fi wide, con- 
 stituting the proximal or first convoluted tubule. It becomes continuous with the 
 spiral tubule of Schachowa (4), which lies in a medullary ray, where it pursues a 
 slightly wavy or spiral course. On the boundary line between the cortical and 
 
 Fig. 228. 
 
 4. Spiral tube. 
 
 13. Straight part of col- 
 lecting tube. 
 
 g. Wavy part of ascend- 
 ing limb of Henle's 
 loop. 
 
 Inner stratum of cortex 
 without Malpighian 
 corpuscles. 
 
 7 and 8. Ascending limb 
 of Henle's loop 
 
 tube. 
 
 Sub-capsular layer with- 
 out Malpighian cor- 
 puscles. 
 
 12. First part of collect- 
 ing tube. 
 
 11. Distal convoluted 
 tubule. 
 
 A)a. cortex. 
 
 10. Irregular tubule. 
 
 3. Proximal convo- 
 luted tubule. 
 
 9. Wavy part of as- 
 cending limb. 
 2. Constriction or neck 
 
 4. Spiral tubule. 
 
 1. Malpighian tuft sur- 
 rounded by Bow- 
 man's capsule. 
 
 8. Spiral part of as- 
 cending limb of 
 Henle's loop. 
 
 B. BOUNDARY 
 ZONE. 
 
 5. Descending limb of 
 Henle's loop tube. 
 
 6. Henle's loop. 
 
 C. PAPILLARY 
 ZONE. 
 
 Diagram of the course of two uriniferous tubules {Klein and Noble-Smitk). 
 
 boundary zone, the spiral tubule suddenly becomes smaller (Isaacs) and passes 
 into the descending portion of Henle's loop (5), which is 14 /* in breadth, and is 
 continued downward through the boundary zone into the medulla, where it forms 
 the narrow loop of Henle (6), which runs backward in the medullary part to the 
 boundary zone. Here it becomes wider (20-26 ft), and as it continues its undu- 
 lating course, it enters a medullary ray, where it constitutes the ascending loop 
 tube (7), which becomes narrower in the cortex. Leaving the medullary ray 
 
422 
 
 COURSE OF THE TUBULES. 
 
 again, it passes into the labyrinth, where it forms a tube with irregular angular 
 outlines — the irregular tubule (10), which is continuous with (Fig. 229, n, n) the 
 second or distal convoluted tubule or intercalated tubule (" Schaltstiick " of Schweig* 
 ger-Seidel) (11), which resembles the proximal tubule of the same name. Its 
 
 Fig. 229. 
 
 1, Blood vessels and uriniferous tubules of the kidney (semi-diagrammatic) ; A, capillaries of the cortex, B, of tha 
 medulla; a, interlobular artery; I, vas afferens; 2, vas efferens; r, ff, vasa recta; c, vena recta; v, v, inter- 
 lobular vein; S, origin of a vena stellata; /, i, Bowman's capsule and glomerulus ; X, X, convoluted tubules; t t t t 
 Henle's loop ; n, n, junctional piece ; o, o, collecting tubes ; O, excretory tube. 
 
 diameter is 40 /i. A short, narrow, wavy junctional or curved collecting tubule 
 (12) connects the latter with one of the straight collecting tubes (13) of a medul- 
 lary ray. As thecollecting tubule proceeds through the boundary zone, it receives 
 numerous junctional tubes, and when it reaches the boundary zone, it forms one 
 
STRUCTURE OF THE TUBULES. 
 
 423 
 
 of the collecting tubes (Fig. 229, O), which unite with one another at acute angles 
 to form the larger straight excretory tubes or ducts of Bellini (15), which open on 
 the summit of the Malpighian pyramids into a calyx of the pelvis of the kidney. 
 In the cortex the collecting tubules are 45 n in diameter, but where they have 
 formed an excretory tube (O), their diameter is 200 to 300 ft; 24 to 80 of these 
 tubes open on the apex of each of the 12 to 15 Malpighian pyramids. In the 
 lowest and broadest part, the membrana propria is strengthened by the presence 
 of a thick supporting framework of connective tissue. 
 
 Structure of the Tubules. — [Below the neck, the tubules are lined every- 
 where by a single layer of nucleated epithelium.] Bowman's capsule, 
 which is about -%hs mcn > n diameter (Fig. 230, II), consists of a homogeneous 
 basement membrane lined internally by a single continuous layer of flattened 
 cells {k). According to Roth, the basement membrane itself is composed of 
 endothelial cells. [In the foetus the lining cells are more polyhedral.] Within 
 the capsule lies the glomerulus or tuft of blood vessels. The cells lining the cap- 
 sule are reflected over and between the lobules of which the glomerulus consists. 
 The glomerulus may not completely fill the capsule, so that, according to the 
 
 Fig. 230. 
 
 II, Bowman's capsule and glomerulus, a, vas afferens ; e t vas efferens ; e, capillary network of the cortex ; k, endo- 
 thelium of the capsule ; h, origin of a convoluted tubule— 1 1 1, " rodded " cells from a convoluted tubule — a, seen 
 from the side, with^-, inner granular zone ; I, from the surface. — IV, cell lining Henle's looped tubule. — V, cells 
 of a collecting tube. — VI, section of an excretory tube. 
 
 activity of the kidney, there may be a larger or smaller space between the 
 glomerulus and the capsule into which the filtered urine passes. The neck is 
 lined by cubical cells. These cells, in some animals, e.g., the rabbit, sheep 
 {Hassat), mouse {Klein), and frog are ciliated. 
 
 The proximal convoluted tubule is lined by characteristic epithelium. The 
 cells, which are short or polyhedral, form a single layer, with a turbid or cloudy 
 protoplasm (Fig. 230, III, 1 and 2), which not unfrequently contains oil globules. 
 The cells consist of two parts ; the inner, containing the spherical nucleus, is 
 next the lumen, and granular (III, 2, g), while the outer part, next the membrana 
 propria, appears fibrillated, or "rodded" {Heidenhain), from the presence of 
 rods (Stabchen) or fibrils placed vertically to the basement membrane (Fig. 
 231). These appear like the hairs of a brush pressed upon a plate of glass 
 (III, 2). The cells are not easily separated from each other, as neighboring 
 cells interlock by means of the branched ridges on their surfaces (III, 1) — {Hei- 
 denhain, Schachowd). The lumen is well defined, but its size seems to depend 
 upon the state of imbibition of the cells bounding it. 
 
424 
 
 BLOOD VESSELS OF THE CORTEX. 
 
 Fig. 231. 
 
 Convoluted tubule (after 
 ammonium chro- 
 mate) showing 
 "rodded" epithe- 
 lium. 
 
 FlG; 232. 
 
 
 The spiral tubule has similar epithelium and a correspond- 
 ing lumen, although the epithelium becomes lower and somewhat 
 altered in its characters at the lower part of the tube. 
 
 The descending limb of Henle's loop, and the loop itself 
 with a relatively wide lumen, are bounded by clear, flattened 
 epithelial cells, with a bulging nucleus (IV, S) ; the cells lying 
 on one side of the tube being so placed that the bulging part of 
 the bodies of the cells is opposite the thin part of the cells on 
 the opposite side of the tube. [These tubes might be mistaken 
 for blood capillaries, but in addition to their squamous lining, 
 they have a basement membrane, which capillaries have not.] 
 In the ascending limb, the lumen is relatively wide, while 
 its epithelium agrees generally with that in the convoluted 
 tubule, excepting that the "rods" are shorter. Sometimes 
 the .cells are arranged in an " imbricate " manner. 
 
 In the irregular tubule, which has a very small lumen, 
 the polyhedral cells lining it contain oval nuclei, and are 
 shorter than those of the convoluted tubules. The cells, 
 again, are very irregular in size, while their "rodded" character 
 is much coarser and more defined (Fig. 232). 
 
 The distal convoluted tubule closely resembles in its 
 
 structure the proximal convoluted tubule, and is lined by similar 
 
 cells. The curved collecting or junctional tubule, although 
 
 narrow, has a relatively wide lumen, as it is lined 
 
 by clear, somewhat flattened cells. 
 
 The collecting tubes have a distinct lumen, 
 and are lined by clear, somewhat irregular, cubi- 
 cal cells (Fig. 230, V), which, in the larger ex- 
 cretory tubes, are distinctly columnar (VI). The 
 basement membrane is said to be absent in the 
 larger tubes. 
 
 [Klein describes a thin, delicate, nucleated centro-tubular 
 membrane lining the surface of the epithelium next the lumen.] 
 
 II. The Blood Vessels. — The renal artery (Fig. 226) divides into four or 
 five branches, which pass into the kidney at the hilum. These branches, sur- 
 rounded by connective tissue continuous with that of the capsule, continue to 
 divide, and pass between the papillae, to reach the bases of the pyramids on the 
 limits between the cortical and boundary zones, where they form incomplete 
 arches. From these horizontal trunks the interlobular arteries (Fig. 229, a) 
 run vertically and singly into the cortex, between each two medullary rays, and 
 in their course they give off on all sides the short, undivided vasa afferentia 
 (1), each of which enters a Malpighian capsule at the opposite pole from which 
 the urinary tubule is given off. Within the capsule, each afferent artery breaks 
 up into capillaries arranged in lobules and supported by connective tissue, the 
 whole forming a tuft of capillary blood vessels, or a glomerulus. Each glom- 
 erulus is covered on its surface, directed toward the wall of the capsule by a layer 
 of fiat, nucleated epithelial cells (Fig. 230, II), which also dip down between the 
 capillaries {Heidenhain, Huneberg). A vein, the vas efferens (2), which is 
 always smaller than the afferent arteriole, proceeds from the centre of the glom- 
 erulus, and leaves the capsule close to the point at which the afferent vessel enters 
 it (Fig. 230, II). In their structure and distribution all the efferent vessels re- 
 semble arteries, as they divide into branches to form a dense, narrow-meshed 
 capillary network (Fig. 229, A, and Fig. 230, II, c), which surrounds and 
 ramifies over the convoluted tubules. The meshes are elongated around the tubules 
 of the medullary rays, and more polygonal around the convoluted tubules (Fig. 
 
 Epithelium of an irregular tubule of the 
 kidney of a dog {Klein). 
 
LYMPHATICS, NERVES, CONNECTIVE TISSUE. 425 
 
 229). Some of the lowest efferent vessels split up into vasa recta, which run 
 toward the medulla. The interlobular arteries become smaller as they pass toward 
 the surface of the kidney, and some of their terminal capillaries communicate 
 with the capillaries of the external capsule itself.] Venous trunks proceed from 
 the capillary network, to terminate in the interlobular veins (V). These veins 
 begin close under the external capsule by venous radicles arranged in a stellate 
 manner (constituting the stellulse Verheynii, or venae stellatse), and accompany 
 the corresponding artery to the limit between the cortex and boundary zone, 
 where they communicate with the large venous trunks in that situation. 
 
 The blood vessels of the medulla arise from the vasa recta (Fig. 229, r). 
 The latter begin on the limit of the cortex and medulla, either as single, direct, 
 muscular branches (r) of the large arterial trunks, or from those efferent vessels 
 (<?) which lie next to the medulla. The latter are said to be devoid of muscle ; 
 while, according to Huschke, a few vasa recta are formed by the union of the 
 capillaries of the medullary rays. All the vasa recta enter the boundary layer, 
 where they split up into a leash or pencil of small arterioles, which pass between 
 the straight tubules toward the pelvis, and form in their course a capillary network 
 with elongated meshes. From these capillaries there arise venous radicles, which, 
 as they proceed toward the limit between the cortex and medulla, form the venae 
 recta (c), and open into the concave side of the venous trunks in this region. 
 At the apex of the papillae, the capillaries of the medulla form connections with 
 the rosette-like capillaries surrounding the excretory ducts (at I). [The circula- 
 tion through the vasa recta is most important. The cortical system of blood 
 vessels communicates with the medullary, but as most of the vasa recta are derived 
 from the same vessel as the interlobular arteries, it is evident that they may form 
 a side stream through which much of the blood may pass without traversing the 
 vessels of the cortex. Very probably the "short cut " is useful in congestions of 
 the kidney. The amount of distention of these vessels, also, will influence the 
 size of the tubules lying between them. There are two other channels by which 
 blood can pass through the renal arteries without traversing the glomeruli — (i) 
 The anastomoses between the terminal twigs of the renal artery and the sub- 
 capsular venous plexus ; (2) small branches given off, either by the interlobular 
 arteries, or by the afferent vessels before entering the glomeruli {Brunton).~\ 
 
 The blood vessels of the external capsule are derived partly from the terminal twigs of the 
 interlobular arteries, partly from branches of the supra-renal, phrenic and lumbar arteries,which. 
 anastomose with each other. The capillary network has simple meshes. The origins of the veins 
 pass partly into the venae stellatse and partly into the veins of the same name as the arteries. The 
 connection of the area of the renal artery with the other arteries of the capsule explains why, after 
 ligature of the renal artery within the kidney, the blood still circulates in the external capsule {C. 
 Ludwig, M. Herrmann) ; in fact, these blood vessels still supply the kidney with a small amount 
 of blood, which may suffice to permit a slight secretion of urine to take place (Litten, Pautynski). 
 
 III. The lymphatics form a wide-meshed plexus in the capsule of the kidney, while under it 
 they form large spaces (Heidenhain). In the parenchyma of the kidney, the lymphatics are said- 
 to be represented by large slits, devoid of a wall, in the tissues, and are more numerous around the 
 convoluted than the straight tubules. The slits pass to the surface of the kidney, and expand under 
 the capsule. When the lymphatics are greatly distended, they tend to compress the uriniferous tubules . 
 and the bloodvessels (C. Ludwig and Zawarykin). According to Ryndowsky, the uriniferous. 
 tubules are surrounded by true lymphatics with an endothelial lining, and they even penetrate into, 
 the capsule of Bowman, along with the vas atferens. [The large blood vessels are also surrounded 
 by lymphatics.] Large lymphatics, provided wiih valves, pass out of the kidney at the hilum, while 
 others emerge through the capsule ; both sets are connected with the lymph spaces of the capsule of 
 the kidney (A. Budge). 
 
 IV. The nerves form small trunks provided with ganglia (Beale), and accompany the blood 
 vessels. [They are derived from the renal plexus and the lesser splanchnic nerve.] They contain- 
 medullated and non-medullated fibres, and the latter have been traced by W. Krause as far as the 
 apices of the papillae. Their mode of termination is unknown. Physiologically, we are certain that 
 they contain both vaso-motor and sensory fibres; perhaps there may be also vaso-dilator and secretory 
 
 bres. 
 
 V. The connective tissue, or interlobular stroma, forms in the papilla;, especially at their 
 pices, fibrous, concentric layers of considerable thickness between the excretory tubules (Fig. 233). 
 
426 
 
 PHYSICAL CHARACTERS OF URINE. 
 
 Further outward, the fibrillar character becomes less distinct, while at the same time branched 
 connective-tissue corpuscles occur in greater numbers (Beer). In the cortex, the interstitial stroma 
 consists almost entirely of branched corpuscles, which anastomose with each other ( Goodsir). [There 
 is also a small quantity of delicate fibrous tissue around Bowman's capsule, and along the course of 
 the arteries. The connective tissue often plays an important r61e in pathological conditions of the 
 kidney, as in interstitial nephritis.] The outer layers of the capsule of the kidney are composed 
 of dense bundles of fibrous tissue, while the deeper layers are more loose, and send processes into 
 the cortical layers. The deeper layers also contain non-striped muscular fibres (Eberth, W. Krause). 
 The capsule is easily stripped off. None of the secretory substance is removed with it. Under the 
 capsule in the human kidney, there is a thin plexus of non-striped muscular fibres. At the hilum 
 it becomes continuous with the outer fibrous coat of the dilated upper end of the ureter. The fat 
 surrounding the kidney is united to the kidney partly by blood vessels and partly by bands of 
 connective tissue. [The sub-capsular layer of the cortex, and a thin layer next the boundary zone 
 (Fig. 228, a, a), are devoid of Malpighian corpuscles.] 
 
 [Development of a Malpighian Capsule. — The upper end of the urinary tubule is dilated 
 and closed, and into it there grows a tuft of blood vessels (a), pushing one layer of the tube before 
 it (b) ; hence the capillaries become invested by it, just as an organ is surrounded by a serous sac, 
 so that one layer — the reflected one (b) — of the tubule is closely applied to the blood vessels, while 
 the other (c) lies loosely over it with a space between the two (Fig. 234).] 
 
 Fig. 234. 
 
 Development of a glomerulus and 
 Malpighian capsule, a, capil- 
 lary; 6, visceral; c, parietal layer 
 of capsule. 
 
 Transverse section of apex of a. Malpighian pyramid, a, large collecting 
 tubes; b, c, d t tubules of Henle; e t f, blood capillaries. 
 
 255. THE URINE.— Physical Characters.— A knowledge of the com- 
 position of this secretion is of the greatest value to the physician and surgeon. 
 
 1. The quantity of urine passed by an adult man in twenty-four hours is 
 between 1000 and 1500 cubic centimetres, or about 50 ozs., and in the female 
 900 to 1200 c.c. The minimum is secreted between 2-4 a.m., and the maximum 
 between 2-4 p.m. {Weigeliri). 
 
 The amount is diminished by profuse sweating, diarrhcea, thirst, non- nitrogenous food, diminu- 
 tion of the general blood pressure, after severe hemorrhage, and in some diseases of the kidneys. 
 The minimum, which may be normal, is 400 to 500 c.c. It is increased by increase of the general 
 blood pressure, or of the pressure within the area of the renal artery, by copious drinking, contrac- 
 tion of the cutaneous vessels through the action of cold, the passage of a large amount of soluble 
 substances (urea, salts, and sugar) into the urine, a large amount of nitrogenous food, as well as by 
 various drugs, such as digitalis, alcohol, squills. After taking fluids charged with CO,, the amount 
 of urine is increased during the following hours (Quincke). 
 
 The secretion is influenced directly by the nervous system, as in the sudden polyuria following 
 nervous excitement, such as hysteria [when the person usually passes a large amount of very pale- 
 colored urine] ; after an epileptic attack, and also after pleasurable excitement (Beneke). Lastly, 
 
ESTIMATION OF SOLIDS. 
 
 427 
 
 we have the polyuria unaccompanied by the presence of sugar in the urine, which follows injury to 
 a certain pari of the floor of the fourth ventricle (CI. Bernard). The urine is measured in tall, 
 graduated, cylindrical vessels (Fig. 235, A). [In estimating the quantity of urine passed, the patient 
 must, of course, be directed always to empty his bladder at a particular hour, and collect the urine 
 passed during the next twenty-four hours.] 
 
 2. The specific gravity varies, as a mean, between 1015 and 1025 ; the 
 minimum, after copious draughts of water, may be 1002 ; while the maximum, 
 after profuse perspiration and great thirst, may be 1040. The mean specific gravity 
 is about 1020. In newly-born children, the specific gravity falls very considerably 
 during the first three days, which is due to the ingestion of a large amount of 
 food (Martin and Huge). [The specific gravity of the urine in infants is about 
 1003 to 1006.] A healthy adult excretes about 50 grms. \_ij4 oz.] daily of solids 
 by the urine, or about 1 grm. of solids per 1 kilo, of body weight. 
 
 The specific gravity is estimated by means of a urinometer (Fig. 235, B), the urine being at 
 the temperature of 1 6° C. [The urinometer, when placed in distilled water, ought to float at the 
 mark o° or zero, which is conventionally spoken of as 1000. The urine itself ought to be tested in an 
 tall cylindrical glass, of such width that the urinometer, when placed in it, may float freely and not 
 touch the sides. Take care that no air bubbles adhere to the instrument. When reading off the 
 mark on the stem, raise the vessel to the eye and bring the eye on a level with the surface of the 
 water, noting the number which corresponds to this. This rule is adopted, because the water rises 
 on the stem in virtue of capillarity. It is essential that a sample of the mixed urine of the twenty- 
 four hours be used for ascertaining the mean specific gravity.] 
 
 Christison's Formula. — To estimate the amount of 
 solids in the urine. This may be done approximately Fig. z 35- 
 
 by means of the formula of Trapp or Haeser, or, as it A B 
 
 is called in this country^ " Christison's formula," viz., 
 " Multiply the two last figures of a specific gravity ex- 
 pressed in four figures by 2.33" (Christison and Haeser), 
 or by 2 (Trapp), or 2.2 (LoebiscA). This gives the 
 amount of solids in every 1000 parts. [Suppose a person 
 passes 1200 c. c. urine in twenty-four hours, and specific 
 gravity is 1022, then 
 
 22 X 2 -33 = SI.26 grms. in 1000 c. c. 
 To ascertain the amount in 1200 c. c. 
 
 1000 : 1200 : : 51.26 : X = ? 1,26 X I2 °° = 6i .51 grms.] 
 1000 
 Direct estimation to determine the exact amount 
 of solids. Place 15 c. c. of urine in a capsule of known 
 weight, and evaporate it over a water bath, afterward 
 completely dry the residue in an air bath at 100 C, 
 and then cool it over concentrated sulphuric acid. 
 During the process, a small amount of urea is decom- 
 posed, so that the value obtained is slightly too small. 
 Of course, the specific gravity varies with the amount of 
 water in the urine. The most concentrated (highest spe- 
 cific gravity) urine is the morning urine (Urina noctis), 
 especially after being retained in the bladder, e.g., in 
 prolonged sleep a certain amount of water is absorbed, so 
 that the urine becomes more concentrated. The most 
 dilute urine is secreted after copious drinking (Urina 
 potus). Under pathological conditions, as in diabetes 
 mellitus (g 175), the urine is, at the same time, very 
 copious (as much as 10,000 c. c), and very concentrated, 
 while the specific gravity varies from 103010 1060. [The 
 high specific gravity in this case is due to the presence of 
 a large amount of grape sugar.] In fever the urine is 
 concentrated, and small in amount. In polyuria, due to 
 certain nervous conditions, the urine is very dilute and 
 copious, while the specific gravity may be as low as 
 I OOI. 
 
 3. The color of the urine depends on the 
 coloring matters present in it, and varies Graduated cylinder and flask 
 greatly, but the differences in color are due STiiEST"'" 8 the amount 
 
 ion* 
 
 _101« 
 
 _I0B» 
 
 _104« 
 
 Urinometer. 
 
428 
 
 AMOUNTS OF URINARY CONSTITUENTS. 
 
 chiefly to the variations in the amount of water. Normally, it has a pale straw 
 color, but if it contains more water than usual it has a very pale tint, and in 
 certain cases (as in the sudden polyuria occurring after an attack of hysteria), it 
 may be as clear as water. Concentrated urine, as after meals, or the first urine 
 passed in the morning, has a darker color ; it is a dark-yellow or brownish-red ; 
 while it is usually dark colored in fever. 
 
 Foetal urine, and also the urine first passed after birth, are as clear and colorless as water. The 
 admixture of various substances with the urine alters its color. When mixed with blood, according 
 to the degree of decomposition of the haemoglobin, the urine is red or dark brownish-red 
 [more frequently it is smoky'] , especially if the blood comes from the kidneys and the urine is 
 acid. When mixed with bile pigments, it is of a deep yellowish-brown, with an intense yellow 
 froth; senna taken internally makes it intensely red, rhubarb brownish-yellow, and carbolic acid 
 black. Urine undergoing the ammoniacal fermentation may. present a dirty, bluish appearance 
 owing to the formation of indigo. The color of urine is estimated by Neubauer and Vogel by 
 means of an empirical " color scale." 
 
 [Amounts of the Several Urinary Constituents (Loebisch). 
 
 Constituents. 
 
 Quantity 
 
 Specific gravity, 
 
 Water 
 
 Solids, 
 
 Urea, 
 
 Uric acid, 
 
 Sodium chloride, 
 
 Phosphoric acid, 
 
 Sulphuric acid, 
 
 Phosphorus, Calcium, .... 
 Magnesium phosphate, . . . 
 Total quantity of earthy phos- 
 phates 
 
 Ammonia 
 
 Free acid, 
 
 Man, 28 years of age, weight 72 kilos., observations 
 over 8 days (Kerner). 
 
 Means of 
 
 analyses in 
 
 different 
 
 In 24 hours. 
 
 individuals. 
 (Vogel.) 
 
 Min. 
 
 Max. 
 
 Mean. 
 
 In 24 hours. 
 
 C. C. 
 
 C. C. 
 
 C C. 
 
 C. C. 
 
 IO99 
 IOI5 
 
 2150 
 I027 
 
 I49I 
 I02I 
 
 1500 
 
 I020 
 
 I440 
 
 60 
 
 32.0O 
 
 O.69 
 
 I5.OO 
 
 43-4 
 1-37 
 19.20 
 
 38-1 
 
 O.94 
 16.8 
 
 35 
 0.75 
 16.5 
 
 3.OO 
 2.26 
 O.25 
 O.67 
 
 4.07 
 2.84 
 0.51 
 1.29 
 
 3-42 
 2.48 
 O.38 
 O.97 
 
 3-5 
 2.0 
 
 O.92 
 O.74 
 1.74 
 
 1.80 
 1. 01 
 2.20 
 
 '•35 
 0.83 
 1.9S 
 
 1.2 
 0.65 
 
 3 ] 
 
 [Amounts of the Several Urinary Constituents Passed in 24 Hours (Parkes). 
 
 Constituents. 
 
 Water 
 
 Total solids, 
 
 Urea 
 
 Uric acid, 
 
 Hippuric acid, 
 
 Kreatinin, 
 
 Pigment and other substances. 
 
 Sulphuric acid 
 
 Phosphoric acid, 
 
 Chlorine 
 
 Ammonia, 
 
 Potassium, 
 
 Sodium, 
 
 Calcium 
 
 Magnesium, 
 
 By an average man of 
 
 Per 1 kilo, of body 
 
 66 kilos. 
 
 weight. 
 
 grms. 
 
 grms. 
 
 1500.000 
 
 23.000 
 
 72.000 
 
 1. 100 
 
 33-i8° 
 
 0.500 
 
 °-555 
 
 0.0084 
 
 0.400 
 
 0.0060 
 
 0.910 
 
 0.0140 
 
 10.300 
 
 0.1510 
 
 2.012 
 
 0.0305 
 
 3.164 
 
 0.0486 
 
 7.000 (8.12) 
 
 0.1260 
 
 0.770 
 
 . . . 
 
 2.500 
 
 
 1 1 .090 
 
 . ■ ■ 
 
 0.260 
 
 
 0.207 
 
 • • • ] 
 
REACTION OF URINE. 
 
 429 
 
 Fig. 236. 
 
 Fluorescence. — Urine, but especially ammoniacal urine, exhibits fluorescence, which disappears on 
 the addition of an acid, and reappears after the addition of an alkali (Schonbein,Schleiss,v. Lowenfeld), 
 
 Mucous Cloud. — Normal urine, after standing for several hours, deposits a fine cloud of vesical 
 mucus [like delicate cotton wool]. The froth of normal urine is white, and disappears pretty rap- 
 idly, while that on an albuminous urine persists much longer. The urine not unfrequently contains 
 some epithelial cells from the bladder and urethra. 
 
 4. Consistence. — Normal urine, like water, is a freely mobile fluid. 
 
 Large quantities of sugar, albumin, or mucus make it less mobile; while the so-called chylous 
 urine of warm climates may be like a white jelly. 
 
 5. The taste is a saline bitter, the odor is characteristic and aromatic. 
 
 Ammoniacal urine has the odor of ammonia. Turpentine taken internally gives rise to the odor 
 of violets, copaiba and cubebs a strongly aromatic, and asparagus an unpleasant odor. Valerian, 
 assafoetida, and castoreum [but not camphor] also produce a characteristic odor. [The odor of 
 diabetic urine is described as " sweet." ] 
 
 6. The reaction of normal urine is acid, owing to the presence of acid salts, 
 chiefly acid sodic phosphate, which seems to be derived from basic sodic phos- 
 phate, owing to the uric acid, hippuric acid, sulphuric acid, and C0 2 taking to 
 themselves part of the soda, so that the phosphoric acid forms an acid salt. 
 After a diet of flesh, acid potassic phosphate is the cause of the acidity. That 
 the urine contains no free acid is proved by the fact that it gives no precipitate 
 with sodic hyposulphite (v. Voit, Huppert}. 
 
 The acid reaction is increased after the use of 
 acids, e.g., hydrochloric and phosphoric, also by 
 ammoniacal salts, which are changed within the 
 body into nitric acid ; lastly, after prolonged mus- 
 cular exertion (Kliipfel, Fustier). The morning 
 urine is strongly acid. 
 
 The urine becomes less acid or alkaline — 
 (1) By the use of caustic alkalies, alkaline car- 
 bonates, or alkaline salts of the vegetable acids, 
 the last being oxidized within the body into car- 
 bonates. (2) By the presence of calcic, or mag- 
 nesic carbonate. (3) By admixture with alkaline 
 blood, or pus. (4) By removing the gastric juice 
 through a gastric fistula (p. 272 — Maly) ; further, 
 from one to three hours after a meal [The reac- 
 tion of urine passed during digestion may be 
 neutral, or even alkaline. This is due either to 
 the formation of acid in the stomach (Bence 
 Jones), or to a fixed alkali derived from the basic 
 alkaline phosphates taken with the food ( W. Rob- 
 erts).] (5) The urine is rarely alkaline in anaemia, 
 owing to a deficiency of phosphoric and sulphuric 
 acids. [(6) The nature of the food — vegetable 
 food makes it alkaline. (7 ) By profuse sweating 
 (Jos. Hofmann). (8) By absorption of alkaline 
 transudations (blood serum), Quincke^ 
 
 Method. — [The reaction of urine is tested by 
 means of litmus paper. Normal urine turns blue 
 litmus paper red, and does not affect red litmus. 
 An alkaline urine makes red litmus paper blue, 
 while a neutral urine docs not alter either blue or 
 red litmus paper.] Sometimes violet litmus paper 
 is used, which becomes red in acid, and blue in 
 alkaline urine. 
 
 Estimation of the Acidity. — This is done by 
 determining the amount of caustic soda necessary 
 to produce a neutral reaction in 100 c.c. of urine. 
 A soda solution containing 0.0031 grm. of soda = — — 
 in each c.c. is used ; I c.c. of this solution exactly — y 
 neutralizes 0.0063 grm. oxalic acid. To the 100 m 
 
 c.c. of urine in a beaker, soda solution is added, Us§| 
 
 drop by drop, from a graduated burette (Fig. 236), ^^^^^= 
 
 until violet litmus paper becomes neither red nor Graduated burette. 
 
430 
 
 QUANTITY OF UREA. 
 
 blue. The number of c.c. of soda solution is now read off on the burette, and as each c.c. corres- 
 ponds to 0.0063 S rm - oxalic acid, we can easily calculate the amount of oxalic acid which is equiv- 
 alent to the degree of acidity in 100 c.c. of urine. So that the degree of acidity of the urine is 
 expressed by the equivalent amount of oxalic acid, which is completely neutralized by the same 
 amount of caustic soda. 
 
 Urine of Mammals. — The urine of carnivora is pale, passing into a golden yellow ; its specific 
 gravity is high, and its reaction strongly acid. The urine of herbivora is alkaline ; it shows a pre. 
 cipitate of earthy carbonates (hence, it effervesces on the addition of an acid), and of basic earthy 
 phosphates. During hunger, the urine presents the character of that of carnivora, as the animal in 
 this case practically lives upon its own flesh and tissues. 
 
 256.— I. THE ORGANIC CONSTITUENTS OF URINE.— Urea 
 
 = CO(NH,),. — Urea, the diamide of C0 2 , or carbamide, is the chief end 
 product of the oxidation of the nitrogenous constituents of the body. Its com- 
 position is comparatively simple : 1 carbonic acid -f- 2 ammonia — 1 water. It, 
 crystallizes in silky, four-sided prisms with oblique ends (rhombic system), with- 
 out water of crystallization (Fig. 237, a), but when it crystallizes rapidly it forms 
 delicate white needles. It has no action on litmus, is odorless, and has a weak, 
 bitter, cooling taste, like saltpetre ; is readily soluble in water and alcohol, but 
 insoluble in ether. It is an isomer of amnionic cyanate, from which it may be 
 
 Fig. 237. 
 
 ... b 
 
 a. Urea ; b, hexagonal plates ; and c, smaller scales, or rhombic plates of urea nitrate. 
 
 prepared by evaporation ( W'ohler, 1828), whereby the atoms rearrange themselves. 
 It can be prepared artificially in many other ways. 
 
 Decomposition. — When heated above 120 , it gives off ammonia vapor, while a glassy mass of 
 biuret and cyanic acid is left. When urine undergoes the alkaline fermentation (g 263), or when 
 urea is treated with strong mineral acids, or boiled with the hydrates of the alkalies, or superheated 
 with water (240 C), it takes up two molecules of water and produces ammonium carbonate, 
 thus — 
 
 CO(NH 2 ) 2 + 2H 2 = CO(NH 4 0) 2 . 
 
 When brought into relation with nitrous acid, it splits up into water, C0 2 , and N. The two last 
 decompositions are made the basis of methods for the quantitative estimation of urea (fj 257). 
 
 Quantity. — In normal urine, urea occurs to the extent of 2.5 to 3.2 per cent. 
 An adult man excretes daily from 30 to 40 grms. [500 grains, or a little over 1 
 oz.] ; women excrete less, while children excrete relatively more ; owing to the 
 relatively greater metabolism in children, the unit weight of body produces more 
 urea than the unit weight of an adult, in the proportion of 1.7 : 1. If the meta- 
 bolism of the body is in a condition of equilibrium (§ 236), the urea excreted con- 
 tains almost as much N as is taken in with the nitrogenous constituents of the food. 
 
QUANTITY OF UREA. 431 
 
 Variations in the Quantity. — The amount of urea increases when the 
 amount of proteids in the food is increased ; and also when there is a more rapid 
 breaking up of the nitrogenous tissues of the body itself. As this breaking up is 
 increased by diminution of O (Frankel, Penzoldt, and Fleischer), and by loss of 
 blood {Bauer) ; so these conditions also increase the urea (§ 41). It is also in- 
 creased by drinking large draughts of water, by various salts, by frequent urina- 
 tion, and by exposure to compressed air. In diabetic persons, who eat very large 
 quantities of food, it may exceed 100 grms. [over 3 oz.] per day ; during hunger 
 it sinks to 6. 1 grms. [90 grains] per day (Seegen). During inanition, the maximum 
 amount is excreted toward mid-day, and the minimum in the morning. The 
 daily amount of urea varies with the quantity of urine ; three to five hours after a 
 meal, the formation of urea is at a maximum, when it sinks and reaches its mini- 
 mum during the night. Muscular exercise, as a rule, does not increase it 
 (v. Voit, Fick, and Wislicenus — § 295), but only when deficiency of O, causing 
 dyspnoea, occurs at the same time (Oppenheim). 
 
 Pathological. — In acute febrile inflammations, and in fevers generally (\ 22, 3), the urea in. 
 creases until the crisis is reached, and afterward it diminishes ( Vogel). After the fever has passed 
 off, the amount excreted is often under the normal. In some cases of high fever, although the 
 amount of urea formed is increased, it may not be excreted ; I here is a retention of the urea, while, 
 later on, this may lead to an increased excretion (Naunyn). In chronic diseases, the amount 
 depends largely upon the state of the nutrition, the metabolism, and also upon the degree of fever 
 present. Degenerative changes in the liver, e. g.,' due to poisoning with phosphorus, may be ac- 
 companied by diminished excretion of urea and increased excretion of ammonia (Stadelmanri) . It 
 is increased in man by morphia, narcotin, marcein, papaverin, codein, thebain (Fubini), arsenic 
 (Gdthgens), compounds of antimony, and small doses of phosphorus (Bauer), which favor the de- 
 composition of proteids. Quinine which "spares" the proteids diminishes it. 
 
 Occurrence.— Urea occurs in the blood (1 : 10,000), lymph, chyle (2 • 1000), liver, lymph 
 glands, spleen, lungs, brain, eye, bile, saliva, amniotic fluid, and pathologically in sweat, e. g., in 
 cholera, in the vomit and sweat of uraemic patients, and in dropsical fluids. 
 
 Formation. — It is certain that it is the chief end product of the metabolism 
 of the proteids. Less oxidized products are uric acid, guanin, xanthin, hypo- 
 xanthin, alloxan, allantoin. Uric acid administered internally appears in the urine 
 as urea ; alloxan and hypoxanthin can be changed directly into urea. The urea 
 excretion is increased by the administration of leucin, glycin, aspartic acid, or 
 ammonia salts. (Schulzen, Nencki.) As yet, it has not been definitely determined 
 where urea is formed, but the liver and, perhaps, the lymph glands are organs 
 where it is produced (§ 178). ' 
 
 In birds, the liver forms uric acid from ammonia. The liver can be readily excluded from the 
 circulation in birds, and Minkowski found that after this operation the uric acid was diminished and 
 the ammoniacal salts increased ($ 178). 
 
 Antecedents. — During digestion, the proteids are converted into leucin, tyrosin, glycin, and as- 
 paraginic acid. If the amido acids, glycin, leucin, or asparaginic acid, or ammoniacal salts, be 
 given to an animal, the amount of urea excreted is increased. As the molecule of the amido acids 
 contains only one atom of N, and the molecule of urea contains two of N, it is probable that urea 
 may be formed synthetically from these acids. It is possible that the amido acids meet with nitro- 
 genous residues in the juices of the body, e.g., carbamic acid 
 
 or cyanic acid. The union of these may produce urea. Fig. 238. 
 
 According to Salkowski, feeding with these substances ~ _ 
 
 causes the breaking up of the proper proteids of the body ^ *— /N 
 
 so as to provide the necessary components. Schmiedeberg [J ^~M ^\ ^"^ 
 
 is of opinion that urea is formed in the body from ammonia x %J <% &J ^^^ 
 
 carbonate by the removal of water ; and v. Schroder found ^^ *"' ^^^ 
 
 that, when he passed blood containing ammonia carbonate t \ ^ Q yV 
 
 through a fresh liver, the urea in the blood was greatly in- C~\ "■ "J I ^ 
 
 creased. Drechsel succeeded in producing urea at ordinary V/^^ [] /\ ^\/ «ol 
 
 temperatures by the rapid alternating oxidation and reduc- ^^ ^^ \ \ O — 
 
 tion of a watery solution of ammonia carbonate. [We ^\r r" \ ) Cj 
 
 know that the greater part of the urea exists in the blood, /^ V^ ^ 
 
 and that the renal epithelium removes it from the blood. - ^,S U w^ 
 
 Although it is surmised that some of the proteid bodies -w 
 
 named above, more especially leucin, and perhaps, also, Perfect crystals of oxalate of urea. 
 
432 QUALITATIVE AND QUANTITATIVE ESTIMATION OF UREA. 
 
 kreatin, are the precursors of urea, yet we cannot say definitely how or where the transformation 
 takes place. Perhaps this is effected in the liver, and, it may be, also in the spleen (§ 103).] 
 
 Preparation. — Urea is readily prepared from dog's urine (especially after a diet of flesh) by 
 evaporating it to a syrupy consistence, extracting it with alcohol, and again evaporating the filtrate 
 to a syrupy consistence. The crystals which separate are washed with water to remove any 
 extractives that may be mixed with them, and dissolved in absolute alcohol It is then filtered and 
 allowed to crystallize slowly. Or, human urine may be evaporated to one-sixth of its volume 
 and cooled to 0°, and excess of strong nitric acid added, which precipitates urea nitrate mixed 
 with coloring matter. This prec pitate is pressed in blotting paper, then dissolved in boiling water 
 containing animal charcoal, and filtered while hot. When it cools, colorless crystals of urea nitrate 
 separate (Fig. 237, c). These crystals are redissolved in warm water, and barium carbonate added 
 until effervescence ceases ; urea and barium carbonate are formed. Evaporate to dryness, extract 
 with absolute alcohol, filter, and allow evaporation to take p'ace, when urea separates. 
 
 Compounds of Urea. — Urea combines with acids, bases and salts. The 
 following are the most important combinations : — 
 
 1. Urea nitrate (CH 4 N 2 0, HN0 3 ) is easily soluble in water, and not so soluble in water con- 
 taining nitric acid. It forms characteristic rhombic crystals (Fig. 237, b and c). Sometimes the 
 formation of these crystals is used to determine microscopically the presence of urea in a fluid. 
 If a fluid is suspected to contain minute traces of urea, it is concentrated and a drop of the fluid 
 is put on a microscopic slide. A thread is placed in the fluid, and the whole is covered with a 
 cover glass. A drop of concentrated nitric acid is allowed to flow under the cover glass, and after 
 a time crystals of urea nitrate adhering to the thread may be detected with the microscope. 
 
 2. Urea oxalate (CH 4 N 2 0) 2> C 2 H 2 4 + H 2 0, is made by mixing a concentrated solution of 
 urea with oxalic acid. The crystals form groups of rhombic tables, often of irregular shape. It is 
 only slightly soluble in cold water, and still less so in alcohol (Fig. 238). 
 
 3. Urea phosphate (CH 4 N 2 0, H 3 P0 4 ) forms large, glancing rhombic crystals, very easily 
 soluble in water. It is obtained by evaporating the urine of pigs fed on dough. 
 
 4. Sodic chloride + urea (CH 4 N 2 0, NaCl -f- H 2 0) forms rhombic, shining prisms, which 
 are sometimes deposited in evaporated human urine. 
 
 5. Urea -|- mercuric nitrate is obtained as a white, cheesy precipitate, when mercuric nitrate 
 is added to a solution of urea. Liebig's titration method for urea depends on this reaction ($ 257, 
 II). 
 
 257. QUALITATIVE AND QUANTITATIVE ESTIMATION OF UREA.— I. 
 
 The Qualitative Estimation of Urea. — (1 ) It may be isolated as such. If albumin be present, 
 add to the fluid three to four times its volume of alcohol, and, after several hours, filter. Evapo- 
 rate the filtrate over a water bath, and dissolve the residue in a few drops of water. 
 
 (2) The crystals of urea nitrate may be detected microscopically (Fig. 237). 
 
 II. Quantitative Estimation. — (1) Sodic hypobromite decomposes urea into C0 2 , H 2 and 
 N. On this reaction depends the Knop-Hufner method of quantitative estimation. The N rises 
 in the form of small. bubbles in the mixed fluid, while the C0 2 is absorbed by the caustic soda. 
 [The reaction is the following : — 
 
 N 2 H 4 CO + 3 NaBrO = 3 NaBr -f C0 2 + 2H 2 + N. 
 The nitrogen is collected and estimated in a graduated tube, and the amount of urea calculated 
 from the volume of nitrogen. The uric acid is also decomposed, but that can be estimated sepa- 
 rately and a correction made. We may use the apparatus of Russell and West, or Dupre, or that 
 of Charteris (Fig. 239).] 
 
 [Ureameter. — Make a solution of hypobromite of soda by mixing 100 grammes NaHO in 250 
 c.c. of water, and adding 25 c.c. of bromine. It is better to be made fresh, as it decomposes by 
 keeping. The graduated tube is placed in a cylindrical vessel, filled with water, and depressed 
 until the zero on the tube coincides with the level of the water. Introduce 15 c.c. of the hypo- 
 bromite solution into the pyramidal-shaped bottle, while into a short test tube are placed 5 c.c. of 
 urine. The test tube with the urine is introduced into the bottle by means of a pair of forceps in 
 such a way that it does not spill. Close the bottle tightly with the caoutchouc stopper, through 
 which passes a glass tube to connect it with the graduated burette. Incline the bottle so as to 
 allow the urine to mix with the hypobromite solution, when the gases are given off, and pass into 
 the collecting tube, which is gradually raised until the surfaces of the liquids outside and in coin- 
 cide. Time should be allowed to permit the whole apparatus to have the same temperature. Read 
 off the amount of gas N evolved, for the C0 2 is absorbed by the caustic soda. The collecting 
 tube is usually graduated beforehand, so that each division of the tube is = o. I per cent, of urea, 
 or 0.44 gr. per fluid oz. Thus, suppose 50 oz. of urine are passed in twenty-four hours, and that 5 
 c.c. of urine evolve 18 measures of N, then 0.44 X 18 X 5° = 39^ grs- of urea. If, however, 
 the tube be graduated into c.c, then 30.3 c.c. of N — 0.1 grm. of urea at the ordinary temperature 
 and pressure.] 
 
 [Squibb's Method is simple and expeditious. Measure off lj£ oz. of liquor sodse chlor. 
 (U. S.), and place it in A (Fig. 240), together with a glass thimble D, containing 4 c.c. of urine. 
 
QUANTITATIVE ESTIMATION OF UREA. 
 
 433 
 
 B is filled with water, connected by an India-rubber tube with A, and so adjusted that when it is 
 in the position shown, no water escapes into C. Filter A, and mix the urine in D with the chlorin- 
 ated solution, when N is given off, displacing water from B into C. All the N escapes in about ten 
 minutes. When the pressure in A and B is restored, the contents of C are measured by a pipette 
 (J), so graduated that each measure is = .0027 grm. urea, from which the calculation is easily 
 made (Martimlale).~\ 
 
 III. Volumetric Method (Lieiig). By means of a graduated pipette (Fig. 241), 40 cubic cen- 
 timetres of the urine are taken up and placed in a beaker. To this is added 20 cubic centimetres 
 of barium mixture to precipitate the sulphuric and phosphoric acids. The barium mixture consists 
 
 Fig. 239. 
 
 Fig. 241. 
 
 Ureameter of Charteris, as made by W. Hume, of 
 Edinburgh. 
 
 Fig. 240. 
 
 Squibb's Method. 
 
 of I vol. of a cold saturated solution of barium nitrate and 2 vols, of a cold saturated solution of 
 barium hydrate. Filter through a dry filter, and take 15 cubic centimetres of the filtrate, which 
 correspond to 10 c.c. of urine, and place in a beaker. Allow a titrated standard solution of 
 mercuric nitrate to drop from a burette into the urine until a precipitate no longer occurs. The 
 mercuric nitrate is made of such a strength that I cubic centimetre of it will combine with 10 
 milligrammes of urea. Test a drop of the mixture from time to time in a watch glass or piece 
 of glass blackened on its under surface, with a solution of sodic carbonate, which is called the 
 indicator. Whenever the slightest excess of mercuric nitrate is added, the mixture strikes & yellow 
 color with the soda. The standard solution must be added drop by drop until this result is 
 28 
 
434 
 
 PROPERTIES OF URIC ACID. 
 
 obtained. Read off the number of cubic centimetres of the standard solution used ; as each centi- 
 metre corresponds to 10 milligrammes of urea, just multiply by ten, and the amount of urea in 10 
 cubic centimetres of urine is obtained. 
 
 This method does not give quite accurate results even in normal urine. To urine containing 
 much phosphates is added an equal volume of the barium mixture. Very acid urines may require 
 several volumes to be added. Urine containing albumin or blood must be boiled, after the addition 
 of a few drops of acetic acid, to remove the albumin. The sodic chloride in the urine also inter- 
 feres with the accuracy of the process, as on adding mercuric nitrate to urine mercuric chloride and 
 sodic nitrate are formed, so that the urea does not combine until the sodic chloride is decomposed. 
 When the urine contains, as is usually the case, 1 to \yi per cent. NaCl, deduct z c.c. from the 
 number of c.c. of the S.S. added to IO c.c. of urine. 
 
 258. URIC ACID = C 5 H 4 N 4 3 .— Quantity. — Uric acid is the nitro- 
 genous substance which, next to urea, carries off most of the N from the body ; 
 in twenty-four hours 0.5 grm. (7 to 10 grains); during hunger, 0.24 grm. (4 
 grains) ; after a strongly animal diet, 2. n grm. (30 to 35 grains) are excreted. 
 The proportion of urea to uric acid is 45 : 1. 
 
 It is the chief nitrogenous product in the urine of birds, reptiles, and insects, while it is absent 
 from herbivorous urine. 
 
 Fig. 242. 
 
 Fig. 243. 
 
 Fig. 242. — Uric acid, a, rhombic tables (whetstone form) ; b, barrel form ; c, sheaves ; d, rosettes of whetstone crys- 
 tals. Fig. 243. — Uric acid. «, rhomboidal, truncated, hexahedral, and laminated crystals ; b, rhombic prism, 
 horizontally truncated angles of the rhombic prism, imperfect rhombic prisms ; c, prism with a hexahedral basic 
 surface, barrel-shaped figure, prism with a hexahedral basal surface ; d, cylindrical figure, stellate and superim- 
 posed groups of crystals. 
 
 If a mammal be fed with uric acid, part of it becomes more highly oxidized 
 into urea, while the oxalic acid in the urine is also increased (§ 260 — Wohler, v. 
 Frerichs) ; in fowls, feeding with leucin, glycin, or asparaginic acid (v. Knieriem), 
 or ammonia carbonate {Schroeder), increases the amount of uric acid. When 
 urea is administered to fowls, it is reduced chiefly to uric acid (JJech, H. Mayer, 
 
 Me). ... 
 
 Properties. — Uric acid is dibasic, colorless, and crystallizes in various forms 
 (Figs. 242 and 243), belonging to the rhombic system. When the angles are 
 rounded, the whetstone form (a) is produced, and if the long surfaces be flattened 
 six-sided tables occur. Not unfrequently diabetic urine deposits spontaneously 
 large, yellow, transparent rosettes (</). If 20 c.c. of HC1, or acetic acid, be 
 added to 1 litre of urine, crystals (£) are deposited, like cayenne pepper, on the 
 surface and sides of the glass, after several hours. [The HC1 decomposes the 
 urates, and liberates the acid, which does not crystallize at once, owing to the 
 presence of the phosphates in the urine (Briicke). Crystals of uric acid are 
 
ESTIMATION OF URIC ACID. 435 
 
 usually yellowish in color from the pigment of the urine, and they are soluble in 
 caustic potash.] 
 
 Solubility. — It is tasteless and odorless ; reddens litmus ; is soluble in 18,000 parts of cold, and 
 in 15,000 of boiling water, and insoluble in alcohol and ether. Horbaczewski prepared it synthetic- 
 ally by melting together glycin, or, as it is also called glycocin, and urea. 
 
 It is freely soluble in alkaline carbonates, borates, phosphates, lactates, and acetates, these salts 
 at the same time removing a part of the base ; thus there are formed acid urates and acid salts from 
 the neutral salts. It is soluble in concentrated sulphuric acid, from which it may be precipitated by 
 the addition of water. During dry distillation it decomposes into urea, cyanuric acid, hydrocyanic 
 acid, and ammonium carbonate. Superoxide of lead converts it into urea, allantoin, oxalic acid, and 
 C0 2 ; while ozone forms the same substances, with the addition of alloxan. When it is reduced 
 by H in statu nascendi, as by sodium amalgam, it forms xanthin and sarkin. It is a less oxidized 
 metabolic product than urea, but it is by no means proved that uric acid is a precursor of urea. 
 
 Occurrence. — Uric acid occurs dissolved in the urine in the form of acid 
 urates of soda and potash. These salts occur also in urinary calculi, gravel, 
 and in gouty deposits. Ammonium urate occurs in very small quantity in a 
 deposit of " urates," but is formed in considerable amount when urine becomes 
 ammoniacal from decomposition (Fig. 250). Free uric acid occurs in normal 
 urine only in the very smallest amount. It is sometimes deposited after a time 
 (Fig. 249). It frequently forms urinary calculi, being sometimes deposited 
 around a speck of albumin as a nucleus (JEbsteiri). [It has also been found in the 
 blood, liver, and spleen. It is remarkable that it has been found in the spleen of 
 herbivora, although, as stated above, it is absent from herbivorous urine. In gout, 
 it accumulates in the blood (Garrod').~\ 
 
 The urine of newly-born children contains much uric acid. Uric acid and its salts are increased 
 after severe muscular exertion, accompanied by perspiration, in catarrhal and rheumatic fevers, and 
 such conditions as are accompanied by disturbance of the respiration ; in leukaemia and tumors of 
 the spleen, cirrhotic liver, and, generally, in cases of catarrh of the stomach and intestinal tract, fol- 
 lowing the excessive use of alcohol, [It is also increased during ague and fevers, and perhaps this 
 has some relation to the congestion of the spleen which accompanies these conditions.] It is 
 diminished after copious draughts of water, after large doses of quinine, caffein, potassic iodide, 
 common salt, sodic and lithic carbonates, sodic sulphate, inhalation of O, slight muscular exertion. 
 In gout, the amount excreted in the urine is small. In chronic tumors of the spleen, anaemia and 
 chlorosis, when the respiration is not at the same time embarrassed, it is also diminished. 
 
 Urates. — Uric acid forms salts — chiefly acid urates — with several bases, which 
 dissolve with difficulty in cold water, but are easily soluble in warm water. Neu- 
 tral urates are changed by C0 2 into acid salts. Hydrochloric and acetic acids 
 break up the compounds, and crystals of uric acid separate. 
 
 (1) Acid sodic urate usually .appears as a brick -red deposit, more rarely gray or white (lateri- 
 tious deposit), tinged with uroerythrin, in urine, in catarrhal conditions of the digestive organs, and 
 in rheumatic and febrile affections. Microscopically, it is completely amorphous, consisting of 
 granules, sometimes disposed in groups ( Fig. 249, i) ; sometimes the granules have spines on them. 
 The corresponding potash salt occurs not unfrequently under the same conditions, and presents the 
 same characters. 
 
 (2) Acid ammonium urate (Fig. 250, a) always occurs as a sediment in ammoniacal urine, either 
 with (1), or mixed with free uric acid, accompanied by triple phosphate. Microscopically, it is the 
 same as (1). (I) and (2) are distinguished by the sediment dissolving when the urine is heated. 
 If a drop of hydrochloric acid be added to a microscopic preparation of the sediment, crystals of 
 uric acid separate. 
 
 (3) Acid calcic urate occurs sometimes in calculi, and is a white, amorphous powder, but slightly 
 soluble in water. When heated on platinum, it leaves an ash of calcium carbonate. Magnesia 
 rarely occurs in urinary calculi. 
 
 259. ESTIMATION OF URIC ACID.— I. Qualitative.— 1. Micro- 
 scopic Characters. — The appearances presented by uric acid and its salts under 
 the microscope. It is deposited from urine after several hours, on adding acetic 
 or hydrochloric acid. 
 
 2. Murexide Test. — Gently heat a urate or uric acid in a porcelain vessel, 
 along with nitric acid. Decomposition takes place, and the color changes to 
 yellow. N and C0 2 are given off; urea and alloxan (C 4 H 2 N 2 4 ) remain. Evapo- 
 
436 KREATININ AND OTHER SUBSTANCES. 
 
 rate slowly, and allow the yellowish-red stain to cool ; on adding a drop of dilute 
 ammonia, a purplish-red color of murexide is obtained ; it becomes blue on the 
 addition of caustic potash. If potash or soda be added, instead of ammonia, a 
 violet color is obtained. 
 
 3. Schiff ' s Test. — If a little uric acid or a urate be dissolved in a solution of an alkaline car- 
 bonate, and this be dropped upon blotting paper saturated with a solution of silver nitrate, reduction 
 of the silver takes place at once, and a black spot is formed (H. Schiff). 
 
 4. On boiling a solution of uric acid or a urate in an alkali, with Fehling's solution (\ 149, 2), 
 at first white urate of the suboxide of copper is deposited, while later, red copper suboxide is 
 formed. 
 
 II. The Quantitative estimation may be made by adding 5 cubic centimetres of concentrated 
 HC1 to 100 c. c. of urine, and allowing it to stand for forty-eight hours in the dark, when the uric 
 acid is precipitated like fine cayenne pepper crystals. Salkowski and Fokker have improved the 
 method. AH the uric acid is not precipitated by the HC1, even after standing for a time. [E. A. 
 Cook uses sulphate of zinc to precipitate the uric acid as urate of zinc. Caustic soda is added to 
 precipitate the phosphates, and then to the clear fluid zinc sulphate solution, which precipitates urate 
 of zinc as a white gelatinous deposit.] 
 
 [Haycraft's method depends on the fact that uric acid forms a compound with silver — urate of 
 silver, which is very insoluble in water. The solutions required are : I. Centinormal amnionic sul- 
 phocyanate, made by dissolving 8 grms. of crystals in I litre of water, and adjust to decinormal silver 
 solution. Dilute with 9 vols, of water, 1 c. c. = 0.00168 uric acid. 2. Saturated solution of iron 
 alum (the indicator). 3. Pure HN0 3 (20 to 30 per cent.). 4. Strong ammonia. Ammoniacal 
 silver solution made by dissolving 5 grms. AgN0 3 in 100 c. c. water, and add NH 4 HO until the 
 solution becomes clear. Process. — Place 25 c. c. of urine in a beaker, and add 1 grm. sxlic bicar- 
 bonate; then add 2 to 3 c. c. of ammonia to precipitate ammonio-magnesic phosphate. Add I to 
 2 c. c. of ammoniacal silver solution, which precipitates silver urate in a white gelatinous form. 
 The precipitate is then thoroughly washed on an asbestos filter, and then dissolved from this by nitric 
 acid, after which the silver is estimated (Volhard's method). In doing so, add a few drops of the 
 indicator, and drop in the centinormal solution of amnionic sulphocyanate. A white precipitate, 
 with a transient reddish coloration, will be formed ; as soon as the red color is permanent, the 
 process is at an end. The uric acid present is ascertained by multiplying the number of cubic centi- 
 metres of the sulphocyanate used by 0.00168.] 
 
 260. KREATININ AND OTHER SUBSTANCES.— Quantity.— 
 
 Kreatinin, C 4 H 9 N 3 2 (Liebig), is derived from the kreatin of muscle, from which 
 it can be obtained by heating in a watery solution, a molecule of water being given 
 off; and, conversely, kreatinin may take up water and form kreatin. The amount 
 excreted daily is 0.6 to 1.3 grammes (8 to 18 grains). 
 
 It is diminished in progressive muscular atrophy, tetanus, anaemia, marasmus, chlorosis, con- 
 sumption, paralysis; and is increased in typhus, inflammation of the lung ; it is absent from the 
 urine of sucklings. 
 
 Properties. — Kreatinin is alkaline in reaction, easily soluble in water and hot alcohol. It occurs 
 in the form of colorless, oblique, rhombic columns. It forms compounds with acids and salts, with 
 silver nitrate, mercuric chloride, and especially with zinc chloride. Kreatinin-zinc chloride ( Fig. 
 244) is used to detect its presence. Test. — Add to urine a few drops of a slightly-brownish solu- 
 tion of nitro-prusside of soda, and then weak caustic soda solution, which cause a Burgundy red 
 color, which soon disappears ( Th. Weyl). When heated with acetic acid, the color changes to 
 green or blue (Salkowski). Kreatinin has been prepared artificially. When boiled with baryta 
 water, it decomposes into urea and sarkosin. When administered by the mouth, or when injected 
 into the blood, the greater part of it reappears unchanged in the urine. 
 
 Xanthin (=C 5 H 4 N 4 2 ) (Marcei) occurs only to the amountof 1 gramme in 300 kilos, of urine. 
 It is a substance intermediate between sarkin and uric acid. Guanin and hypoxanthin may be 
 changed into xanthin ; in contact with water and ferments it passes into uric acid. When evapo- 
 rated with nitric acid, it gives a yellow stain, which becomes yellowish-red on adding potash, and 
 violet-red on applying more heat. It is an amorphous, yellowish-white powder, fairly soluble in 
 boiling water. It has also been found in traces in muscles, brain, liver, spleen, pancreas, and 
 thymus. The crystalline body paraxanthin, and the amorphous heteroxanthin, occur in traces 
 in the urine (Salomon). 
 
 Sarkin (= Hypoxanthin), C 5 H 4 N 4 0. — As yet this substance has been found only in the urine 
 of leuksemic patients (Jakubasch), and it has been prepared in the form of needles or flattened 
 scales (Scherer) from muscle, spleen, thymus, brain, bone, liver, and kidney. In normal urine a 
 body nearly related to, and possibly identical with, hypoxanthin occurs (E. Salkowski). Hypo- 
 xanthin closely resembles xanthin, and can be changed into it by oxidation. Nascent hydrogen, on 
 the other hand, reduces uric acid to xanthin and hypoxanthin. When evaporated with nitric acid 
 
OXALIC ACID AND OXALURIA. 
 
 437 
 
 it gives a light yellow stain, which becomes deeper, but not reddish yellow, on adding caustic soda. 
 It is more easily soluble in water than xanthin, and by this means the two substances can be sepa- 
 rated from each other. Guanin is insoluble in water. 
 
 Oxaluric acid (C 3 H 4 N 2 4 ) occurs in very small quantity combined with ammonia in urine. 
 Physiologically, it is interesting on account of its relation to uric acid. It is a white powder, slightly 
 soluble in water. Ammonia oxalurate can be prepared from uric acid. 
 
 Oxalic Acid (C 2 H 2 Q,). — The series of chemical decompositions of oxaluric 
 acid leads to oxalic acid. It occurs, but not constantly, to the amount of 20 
 
 Fig. 244. 
 
 — i * 
 
 Kreatinin-zinc chloride, u, balls with radiating marks ; b, crystallized from water ; e, rarer forms from an 
 
 alcoholic extract. 
 
 milligrammes daily as oxalate of lime, which is known by the "envelope" 
 shape of the crystals (Figs. 245 and 246) ; insoluble in acetic acid, and forming 
 transparent octahedra. More rarely it assumes a biscut or sand-glass form (Fig. 
 259, c). According to Neubauer, soluble oxalate of lime occurs in urine, being 
 kept in solution by acid sodic phosphate. This substance is excreted in a crys-' 
 talline form, the more the reaction of the urine becomes neutral. 
 
 The genetic relation of oxalic acid to uric acid is shown by the fact, that dogs 
 
 Fig. 246. 
 
 Oxalate of lime, a, octahedra ; b, basal plane of an octahedron forming 
 a rectangle ; c, compound forms ; d, dumb bells. 
 
 Perfect dumb-bell crystals 
 of oxalate of lime. 
 
 fed with uric acid excrete much oxalate of lime (v. Frerichs, Wohler). Oxalic 
 acid may also be produced by the oxidation of products derived from the fatty 
 acid series (p. 414). 
 
 Oxaluria. — The eating of substances containing oxalate of lime (rhubarb) increases the excretion. 
 Increased excretion is called oxaluria ; it is regarded as a sign of retarded metabolism (Benete), 
 and it may give rise to the formation of a calculus. In oxaluria the uric acid is also often increased 
 in amount. Perhaps, in the first instance, there is an increased formation of uric acid, from which 
 oxalic acid, urea, and C0 2 may be formed. The amount of oxalic acid is increased after the use 
 of wine and sodic bicarbonate. 
 
438 
 
 HIPPURIC ACID. 
 
 Hippuric Acid = C 9 H 9 N0 3 (Benzoylamidoacetic acid) occurs in large amount 
 in the urine of herbivora {Liebig), and in them it replaces uric acid, and is one of 
 the chief end products of the metabolism of nitrogenous substances ; in human 
 urine the daily amount is small, 0.3 to 3.8 grms. (5 to 50 grains). It is an odor- 
 less monobasic acid with a bitter taste, and crystallizes in colorless, four-sided 
 prisms (Fig. 247). It is readily soluble in alcohol, and only soluble in 600 parts 
 of water. 
 
 It is a conjugated acid, and is formed in the body from benzoic acid, or some 
 nearly related chemical body, such as the cuticular substance of plants, or from 
 oil of bitter almonds, cinnamic or chinic acid, which easily pass by reduction 
 (chinic acid) or by oxidation (cinnamic acid) into benzoic acid ; glycin uniting 
 with it, and water being given off — 
 
 C 7 H 6 2 + C 2 H 5 N0 2 = C 9 H 9 N0 3 + H 2 
 
 Benzoic acid + Glycin = Hippuric acid + Water. 
 
 [Formation. — When benzoic acid is introduced into the alimentary canal of 
 an animal (rabbit or dog), it appears in the urine as hippuric acid ; while nitro- 
 
 Fig. 247. 
 
 Hippuric acid. 
 
 benzoic acid appears as nitro-hippuric acid. As the benzoic acid passes through 
 the body it becomes conjugated with glycin or glycocin, chiefly in the kidneys. 
 The hippuric acid in the urine of herbivora is chiefly derived from some substance 
 with a benzoic acid residue present in the cuticular coverings of the food. That 
 hippuric acid, in part at least, is formed in the kidneys is shown by the follow- 
 ing considerations : If arterialized blood, containing benzoic acid and glycin, or 
 even benzoic acid alone, be passed through the blood vessels of a fresh living 
 excised kidney, hippuric acid is found in the blood after it is perfused. Even 
 after forty-eight hours, if the kidney be kept cool, the synthesis takes place. If 
 the kidney be kept too long, the conjugation does not take place. If the fresh 
 kidney be chopped up, and kept at the temperature of the body with benzoic acid 
 and glycin, hippuric acid is formed. Oxygen seems to be necessary for the pro- 
 cess, for, if blood or serum containing carbonic oxide be used, there is no forma- 
 tion of hippuric acid.] 
 
 According to this view, it is derived chiefly from the food of herbivorous animals, and hence it is 
 absent from the urine of sucking calves. But it is also formed in the body from the proteids. In 
 the dog, the formation of hippuric acid occurs in the kidney (Schmiedeberg and Bunge), and in the 
 
COLORING MATTERS OF URINE. 439 
 
 frog also outside the kidney. Kiihne and Hallwachs thought it was formed in the liver, and Jaars- 
 veld and Stockvis in the kidney, liver, and intestine. The observation of Salomon that, after excision 
 of the kidneys in rabbits, and injection of benzoic acid into the blood, hippuric acid was found in 
 the muscles, blood, and liver, goes to show that it must be formed in other organs beside the 
 kidneys. The power of changing benzoic acid introduced into the human body into hippuric acid, 
 may even be abolished in disease of the kidney [Jaarsveld and Stockvis, Fr. Kronecker). Under 
 certain circumstances it seems that hippuric acid, already formed, may be again decomposed in the 
 tissues. 
 
 It is greatly increased after eating pears, plums, and cranberries; and it is also increased in 
 icterus, some liver affections, and in diabetes. When boiled with strong acid or alkalies, or with 
 putrid substances, it takes up H 2 and splits into benzoic acid and glycin. 
 
 [Crystals of hippuric acid when heated in a test tube are decomposed, and a sublimate of benzoic 
 acid and ammonic benzoate condenses on the upper cool part of the tube, while there is an odor of 
 new hay, and oily drops remain in the tube.] It is freely soluble in water, with difficulty in alcohol, 
 and insoluble in ether. 
 
 Preparation. — Add milk of lime to the fresh urine of horses or cows to form calcic hippurate. 
 Filter, evaporate the nitrate to a small bulk, and precipitate the hippuric acid with excess of hydro- 
 chloric acid. To purify the hippuric acid, crystallize it several times from a hot watery solution. 
 
 Cynuric Acid. — C 20 H 14 N 2 6 -f- H 2 occurs in the urine of dogs [J. v. Liebig). 
 
 Allantoin, C 4 H 6 N 4 3 , which occurs in the amniotic fluid of the cow, is found 
 in minute traces in normal urine after flesh food, and is more abundant during the 
 first weeks of life, and during pregnancy. 
 
 After large doses of tannic acid, the amount is increased [ScKottiri), while in dogs feeding with 
 uric acid also increases it (Salkowski). 
 
 Properties. — It forms shining, prismatic crystals; from the urine of sucking calves it crystallizes 
 in transparent prisms. It is decomposed by ferments into urea, ammonium oxalate, and carbonate, 
 and another as yet unknown body. • 
 
 Preparation. — (a) The urine is precipitated with basic lead acetate, the lead in the nitrate is re- 
 moved by sulphuretted hydrogen, and the filtrate itself is then evaporated to a syrup, from which 
 the crystals separate, after standing for several days. They are then washed with water, and re- 
 crystallized from that water [Salkowski). 
 
 261. COLORING MATTERS OF THE URINE.— 1. Urobilin 
 
 {Jaffe) is most abundant in the highly colored urine of fevers, but it also occurs 
 in normal urine. It is a derivative of haematin, or of the bile pigments (§ 177) de- 
 rived from the latter. It is identical with the hydrobilirubin of Maly (§117, 3, g). 
 It gives a red, or reddish yellow color to urine, which becomes yellow on the addi- 
 tion of ammonia. 
 
 Preparation. — Prepare a chloroform extract of urine containing urobilin —add iodine to the 
 extract, and remove the iodine by shaking the mixture with dilute caustic potash, which forms 
 potassic iodide. This potash solution becomes yellow or brownish yellow, and exhibits beautifu 
 green fluorescence [Gerhardt). 
 
 Urobilin may be extracted from many urines by ether [Salkowski). When subjected to the 
 action of reducing agents, e.g., sodium amalgam, a colorless product is obtained, which on exposure 
 to the air absorbs O, and becomes retransformed into urobilin. This colorless body is identical with 
 the chromogen which Jaffe found in urine. 
 
 If urine is treated with soda or potash, the characteristic absorption band lying between b and F, 
 passes nearer to b, becomes darker and more sharply defined. According to Hoppe-Seyler, urobilin 
 is formed in urine after it is voided, from another urobilin-forming body (Jaffe's chromogen) absorb- 
 ing oxygen. If urine containing urobilin be made alkaline with ammonia, and zinc chloride be 
 added, it exhibits marked fluorescence ; it has a green shimmer by reflected light. When urobilin 
 is isolated, it fluoresces without the addition of zinc chloride. In cases of jaundice ($ 180), where 
 Gmelin's test sometimes fails to reveal the presence of bile pigments, urobilin occurs. This " uro- 
 bilin icterus " (Gerhardt) occurs chiefly after the absorption of large extravasations of blood. Ac- 
 cording to Cazeneuve, the urobilin is increased in all diseases where there is increased disintegration 
 of colored blood corpuscles. 
 
 2. Urochrome ( Thudichum) is regarded as the chief coloring matter of urine. It may be iso- 
 lated in the form of yellow scales, soluble in water, and in dilute acids and alkalies. The watery 
 solution oxidizes, and when exposed to air becomes red owing to the formation of uroerythrin 
 ( Thudichum) When acted on by acids, new decomposition products are formed, e. g., urome- 
 lanin. Uroerythrin gives the red color to deposits of urates (\ 258). 
 
 3. A brown pigment containing iron is carried down with uric acid, which is precipitated on the 
 addition of hydrochloric acid (\ 258). By repeatedly adding sodic urate to the urine, and precipi- 
 tating the uric acid by hydrochloric acid, a considerable amount may be obtained (JCunkel). 
 
440 INDICAN, PHENOL AND PARAKRESOL. 
 
 In cases of melanotic tumors, there has been occasionally observed urine, which becomes dark, 
 owing to melanin ($ 250, 4), or to a coloring matter containing iron (Kunkel). 
 
 262. INDIGO— PHENOL— KRESOL— PYROKATECHIN— AND 
 SKATOL-FORMING SUBSTANCES.— 1. Indican [C 8 H,NSOJ or 
 indigo-forming substance (Schunck), is derived from indol, C 8 H,N (Jaffe), the 
 basis of indigo {Bayer), and is formed in the intestine by the pancreatic diges- 
 tion of proteids (§ 170, II), but it also arises as a putrefactive product (§ 184, 6). 
 Indol, when united with the radical of sulphuric acid, HS0 3 , and combined with 
 .potassium, forms the so-called indigogen or indican of urine (Brieger, Baumann). 
 This substance (C 8 H 6 NS0 4 K = indoxyl-sulphate of potash) forms white glancing 
 tablets and plates ; readily soluble in water and less so in alcohol. By oxidation 
 it forms indigo-blue — 2 indican -f- 2 = Ci 6 H 10 N 2 O 2 (indigo-blue) -J- 2HKSO4 
 (acid potassic sulphate). It is more abundant in the urine in the tropics, and it 
 is absent from the urine of the newly-born (Senator). 
 
 Tests.— (1) Add to 40 drops of urine, 3 to 4 c.c. of strong fuming hydrochloric acid, and 2 to 3 
 drops of nitric acid. Boil, a violet-red color with the deposition of true crystalline indigo-blue 
 (rhombic) and indigo-red attest its presence. Putrefaction causes a similar decomposition in 
 indican ; hence, we not unfrequently observe a bluish- red pellicle of microscopic crystals of indigo- 
 blue, or even a precipitate of the same {Hill Hassal, 1853). (2) Mix in a beaker equal quantities 
 of urine and hydrochlorous acid, and add two drops of a solution of chloride of lime ; the mixture 
 at first becomes clear, then blue (Jaffe). Add chloroform, and shake the°mixture vigorously for 
 some time ; the chloroform dissolves the blue coloring matter, which is obtained as a deposit, when 
 the chloroform evaporates (Senator, Salkowski). (3) Heat to 70 one part of urine with two parts 
 of nitric acid, and shake up with chloroform ; the chloroform dissolves the indigo which is formed, 
 assumes a violet color and gives an absorption band between C and D, slightly nearer D (Hoppe- 
 Seyler). Jaffe found in 1500 c.c. of normal human urine, 4.5 to 19.5 milligrammes of indigo; 
 horse's urine contains 23 times as much. The subcutaneous injection of indol increases the indican 
 in the urine (Jaffi). E. Ludwig obtained indican by heating hsematin or urobilin with a caustic 
 alkali and zinc dust. It has also been found in the sweat (Bizio). 
 
 Pathological — The indican in the urine is increased when much indol is formed in the intes- 
 tine ($ 172, II), e.g., in typhus, lead colic, trichinosis, catarrah and hemorrhage of the stomach, 
 cholera, carcinoma of the liver and stomach ; obstruction of the bowel or ileus, peritonitis and 
 diseases of the small intestine — in cachexias, long-standing suppuration, paraplegia — after taking 
 creosote, oil of bitter almonds, turpentine or nux vomica. 
 
 2. Phenol, C 6 H e O, carbolic acid, monohydroxylbenzol, § 252), was discovered 
 by Stadeler in human urine (more abundant in horse's urine). It does not occur 
 as carbolic acid, but in combination with a substance from which it is separated 
 by distillation with dilute mineral acids. The " phenol-forming substance " is, 
 according to Baumann, " phenolsulphuric acid" (QH 5 0, SO s H), which in 
 urine is united with potash. 
 
 Phenol is derived from the decomposition of proteids by pancreatic digestion ($ 172, II), and 
 also from putrefaction (§ 184, 6), the mother substance being tyrosin. Hence, the formation of 
 phenolsulphuric acid is analogous to the formation of indican. 
 
 If in the' employment of carbolic acid it be absorbed, the phenolsulphuric acid becomes greatly 
 increased in amount (Almen, Salkowski), so that sulphuric acid must be united with it ; hence, 
 alkaline sulphates are decomposed in the body, so that the latter may be absent from the urine 
 (Baumann). Living muscle or liver, when digested in a stream of air for several hours with 
 blood to which phenol and sodic sulphate are added, yields phenolsulphuric acid ; while, under 
 the same circumstances, pyrokatechin forms ethersulphuric acid. 
 
 Carbolic Urine. — When carbolic acid is used externally or internally, and it is absorbed, it 
 causes a deep, dark-colored urine, due to the oxidation of phenol into hydrochinon (orthobioxy- 
 benzol = C 6 H 6 2 ), which, for the most part, appears in the urine as ethersulphuric acid (Bau- 
 mann and others). 
 
 3. Parakresol, (hydroxy ltoluol, C,H 8 0) with its isomers ortho- and meta- 
 kresol (the latter in traces), is more abundant in urine (Baumann, Preusse). It 
 also occurs in combination with sulphuric acid. 
 
 Test for phenol (and also kresol) : Distil 150 c.c. urine with dilute sulphuric acid. The distillate 
 gives a brown crystalline deposit of tribromophenol with bromine water, as well as a red color with 
 Millon's reagent. 
 
 Hydroxylbenzol (pyrokatechin, hydrochinon) is obtained from urine, when it is heated for a 
 long time with hydrochloric acid. 
 
INORGANIC CONSTITUENTS OF THE URINE. 441 
 
 Resorcin which is an isomer of hydrochinon, when administered internally, also appears in the 
 urine as ethersulphuric acid. Toluol and naphthalin behave similarly. 
 
 4. Pyrokatechin = C 6 H 6 2 (metadihydroxylbenzol) is formed along with 
 hydrochinon from phenol, and is an isomer of the former. It behaves like indol 
 and phenol, for when united with sulphuric acid, it forms the pyrokatechin-form- 
 ing substance {Baumann, Herter). Small quantities sometimes occur in human 
 urine ; it is more abundant in the urine of children {Ebstein and Miiller) ; it 
 becomes darker when the urine putrefies. 
 
 Perhaps pyrokatechin is formed in the body from decomposed carbohydrates, from which Hoppe- 
 Seyler obtained it by heating them with water under a high pressure, as well as by acting on them 
 with alkalies. 
 
 5. Skatol (§ 252), which is crystalline, and is formed during putrefaction in 
 the intestine, also appears in the urine as a compound of sulphuric acid. On 
 feeding a dog with skatol, Brieger found much potassic skatol-oxysulphate. 
 
 Test. — Skatol compounds are recognized by adding dilute nitric acid, which causes a violet 
 color, or of fuming nitric acid, which precipitates red flakes (Nencki). Its quantity is regulated 
 by the same conditions as indican. 
 
 The aromatic oxyacids, hydroparacumaric acid and paraoxyphenylacetic acid (the former a 
 putrefactive product of flesh, the latter obtained by E and H — Salkowski, from putrid albumin), 
 occur in the urine {Baumann, \ 252). Shake tbe urine treated with a mineral acid with ether, 
 evaporate the latter, and dissolve the residue in water. If aromatic oxyacids are present, they give 
 a red color with Millon's reagent. 
 
 Baumann gives the following series of bodies, which are formed from tyrosin by decomposition 
 and oxidation ; most of the substances are formed both during the decomposition of albumin, and 
 also in the intestine, whence they pass into the urine : Tyrosin, CgHnNOj -+- H 2 = C 9 H 10 O 3 
 (hydroparacumaric acid) + NH,. C 9 H ]0 O 3 = C g H 10 O (paraethylphenol, not yet proved) + 
 C0 2 . C 8 H 10 O + 3 = C 8 H 8 O s (paraoxyphenylacetic acid) + H 2 0. C 8 H 8 3 = C,H 8 
 (parakresol) -+- C0 2 . C,H g O + Os = C,H 6 O s (paroxybenzoic acid, not yet proved) -f- H 2 0. 
 C 7 H 8 = C 6 H 6 (phenol) + CO ? . 
 
 Potassium sulphocyanide, derived from the saliva, also occurs in urine. After acidulation 
 with hydrochloric acid, its presence may be detected by the ferric chloride test (§ 146 — Gscheidlen 
 and J. Munk). One litre of human urine contains 0.02 to 0.08 gramme combined with an alkali. 
 
 Succinic acid, C 4 H 6 4 [Meissner and Shepard), occurs chiefly after a diet of flesh and fat, and 
 almost disappears after a vegetable diet. It is a decomposition product of asparagin, and therefore 
 occurs in considerable amount in the urine after eating asparagus. It is also a product of the alco- 
 holic fermentation (J 150), and as it passes out of the body unchanged, it occurs in the urine of 
 those who imbibe spirituous liquors. It passes unchanged into the urine (Neu/iauer). 
 
 Lactic acid (C 3 H 6 3 ) is a constant constituent of urine (Lehmann, Briicke). Other observers 
 have found fermentative lactic acid in diabetic urine ; sarcolactic acid after poisoning with phos- 
 phorus and in trichinosis. Occasionally traces of volatile fatty acids are present. Some animal 
 gum occurs in urine (p. 416), and Bechamp's " Nephrozymose " consists for the most part of 
 gum (Landwefir). This substance is precipitated from urine by adding to it three times its volume 
 of 90 per cent, alcohol. It is not a simple body, but at 6o° to 70 C. it transforms starch into sugar 
 (v. Vintschgau). 
 
 Ferments. — Traces of diastatic, peptic, tryptic, and rennet ferment have been found, especially 
 in urine of high specific gravity. 
 
 Traces of sugar {Briicke, Bence Jones) to the amount of 0.05 to 0.01 per cent., and less, occur 
 in normal urine. After the ingestion of milk-, cane-, or grape sugar (50 grms.) these varieties of 
 sugar appear in small quantity in the urine ( Worm Miillei — f 267, 7). 
 
 Krytophanic acid (C 3 H 9 N0 5 ), according to Thudichum, occurs as a free acid in urine, but 
 Landwehr regards it as an animal gum. 
 
 Aceton (C 3 H 6 0) is formed when normal urine is oxidized with potassic bichromate and sul- 
 phuric acid, and it is formed from a reducing substance present in normal urine (apparently derived 
 from the grape sugar of the blood). Aceton occurs in traces as a normal urinary constituent, 
 which is increased during increased decomposition of the tissues, e.g., carcinoma, inanition. It 
 has also been found in the blood in fever (v. Jacksch). Test. — Acidulate half a litre of urine 
 with AC1 and distil ; when treated with tincture of iodine and ammonia there is a turbidity due to 
 iodoform. 
 
 II. THE INORGANIC CONSTITUENTS OF THE URINE.— 
 
 The inorganic constituents are either taken into the body as such with the food 
 and pass off unchanged in the urine, or they are formed in the body owing to the 
 sulphur and phosphorus of the food being oxidized and the products uniting with 
 
442 
 
 PHOSPHORIC ACID AND EARTHY PHOSPHATES. 
 
 bases to form salt. The quantity of salts excreted daily in the urine is 9 to 25 
 grammes [^ to J^ oz.]. 
 
 1. Sodic chloride— to the amount of 12 (10 to 13) grammes [180 grains]— 
 is excreted daily. It is increased, after a meal, by muscular exercise, drinking 
 of water, and generally, when the quantity of urine is increased, by the free use 
 of large quantities of common salt, but by potash salts also ; while it is dimin- 
 ished under the opposite conditions. 
 
 Tn disease it is greatly diminished ; in pneumonia and other inflammations accompanied by 
 effusions, in continued diarrhoea and profuse sweating, constantly in albuminuria and in dropsies. 
 [In cases of pneumonia, sodic chloride may, at a certain stage, almost disappear from the urine, and 
 it is a good sign when the chlorides begin to reappear.] In other chronic diseases, the amount of 
 NaCl excreted runs nearly parallel with the amount of urine passed. In conditions of excitement 
 the amount of sodic chloride is diminished, and potassic chloride increased; in conditions of de- 
 pression the reverse is the case (Zeulzer). 
 
 Test.— Add to the urine nitric acid and then nitrate of silver solution, which gives a white, curdy 
 precipitate of chloride of silver. In albuminous urine the albumin must first be removed. Micro- 
 scopically look for the step like forms of the common salt, and also for the crystals of sodic chloride 
 urea (\ 256, 4). 
 
 2. Phosphoric acid occurs in urine as acid sodic phosphate and acid 
 
 Fig. 248. 
 
 a, Spermatozoa ; c, amorphous calcic carbonate ; b, crystalline magnesic phosphate. 
 
 calcic and magnesic phosphates (Fig. 248, ¥), to the amount of about 2 
 grammes daily [30 grains], but it is more abundant after a flesh than after a vege- 
 table diet. The amount increases after a mid-day meal until evening, and falls 
 during night until next day at noon. It is partly derived from the alkaline and 
 earthy phosphates of the food, and it is partly a decomposition product of lecithin 
 and nuclein. As phosphorus is an important constituent of the nervous system, 
 the relative increase of phosphoric acid is due to ipcreased metabolism of the 
 nervous substance. 
 
 Pathological. — In fevers, the increased excretion of potassic phosphate is due to a consumption of 
 blood and muscle (g 220, 3). It is also increased in inflammation of the brain, softening of the 
 bones, diabetes, and oxaluria ; and after the administration of lactic acid, morphia, chloral, or chloro- 
 form. It is diminished during pregnancy, owing to the formation of the fcetal bones ; also after 
 the use of ether and alcohol, and in inflammation of the kidney. 
 
 Test. — Earthy phosphates are precipitated by heat. This precipitate is 
 distinguished from albumin, which is also precipitated by heat, by being soluble 
 in nitric acid, which precipitated albumin is not. [The earthy phosphates are 
 not precipitated until near the boiling point.] 
 
SULPHURIC ACID AND OTHER BASES. 443 
 
 Quantitative. — The amount of phosphoric acid is estimated by tritation with a standard solution 
 of uranium acetate ; ferrocyanide of potassium being the indicator. The indicator gives a brown- 
 ish-red color when there is an excess of free uranium acetate. 
 
 In addition to phosphoric acid, phosphorus occurs in an incompletely oxidized form in the urine, 
 e. g., glycerinphosphoric acid (§ 251, 2) (Sotnitzschewsky), which occurs to the amount of 15 milli- 
 grammes in a litre of urine, is increased in nervous diseases (Lepine), and after chloroform narcosis 
 [Ziilzer). 
 
 3. Sulphuric acid occurs in the urine, the greater part in combination with 
 the alkalies, and the remainder united with indol, skatol, and pyrokatechin, in the 
 form of aromatic ethersulphuric compounds (Baumann), the ratio being 1 : o 1045. 
 All conditions which favor the formation of indol, skatol, or pyrokatechin, in- 
 crease the amount of combined sulphuric acid. The total daily amount of sul- 
 phuric acid is 2.5 to 3.5 grammes [37 to 52 grains]. It is increased by the 
 administration of sulphur (Krause). The sulphuric acid is chiefly derived from 
 the decomposition of proteids, and hence its amount runs parallel with the amount 
 of urea excreted. The amount of alkaline sulphates in the food is, as a rule, very 
 small. 
 
 An increased excretion of sulphuric acid in fevers indicates an increased metabolism of the 
 tissues of the body. In renal inflammation it has been observed to be diminished, and in eczema 
 it is greatly increased. Feeding with taurin (which contains sulphur), in the case of rabbits (but 
 not in carnivora nor man), increases the sulphuric acid in the urine (Salio7i/ski). According to 
 Ziilzer, a copious secretion of bile lessens the relative amount of sulphuric acid in the urine. 
 
 Test. — Barium chloride gives a copious, white, heavy precipitate of barium sulphate, insoluble in 
 nitric acid. 
 
 In addition to sulphuric acid, sulphur (J) occurs in an incompletely oxidized form in the urine 
 (potassium sulphocyanide, sulphurous acid, cystin, and sulphur-bearing compounds derived from the 
 bile — Kunkel,v. Voit — § 177,6). Hyposulphurous acid, as an alkaline salt, is an abnormal con- 
 stituent in typhus ; and so is sulphuretted hydrogen, which is recognized by the blackening of a 
 piece of paper moistened with lead acetate and ammonia held over the urine. 
 
 4. Excessively minute traces of silicic acid and nitric acid derived from drinking water have 
 been found in urine. Organic acids, e. g., citric and tartaric, when taken internally, increase the 
 amount of carbonates in the urine. The urine may effervesce on the addition of an acid. 
 
 The sodium in the urine is chiefly combined with chlorine, but a small part of 
 it is united with phosphoric and uric acids ; potassium (which is about yi of the 
 sodium) is chiefly combined with chlorine. In fevers more potash is excreted than 
 soda, and during convalescence, the reverse is the case ; calcium and magne- 
 sium exist in normal acid urine as chlorides or acid phosphates. If the urine is 
 neutral, neutral calcium phosphate and magnesium phosphate are precipitated. 
 Ebstein found the latter in alkaline urine as large, clear, four-sided prisms in diseases 
 of the stomach. If the urine is alkaline, calcium carbonate (Fig. 248, c) or 
 tribasic calcic phosphate are deposited as such, while the magnesium is precipitated 
 in the form of ammonio-magnesium phosphate, or triple phosphate. The calcium 
 is derived from the food, and depends upon the amount of lime salts absorbed 
 from the intestine. Free ammonia is said to occur (0.72 gramme, or 7 grains 
 daily) in perfectly fresh urine {Neubauer and Briicke), and the amount is greater 
 with an animal than with a vegetable diet (Coranda). The amount of fixed am- 
 monia is increased by the administration of mineral acids ( Walter, Schmiedeberg, 
 Galligens). Iron (1 to 11 milligrammes per litre) is never absent. There is a 
 trace of hydric-peroxide' {Schonbeiri), which is detected by its decolorizing 
 indigo solution on the addition of iron sulphate. 
 
 Gases. — 24.4 c.c. of gas was obtained from one litre of urine — 100 volumes of the gases pumped 
 out consisted of 65.40 vol. C0 2 , 2.74 O, 13.86 N. After severe muscular action, the amount of 
 CO 2 may be doubled; digestion also increases it. 
 
 263. SPONTANEOUS CHANGES IN URINE— FERMENTA- 
 TIONS. — Acid Fermentation. — When perfectly fresh urine is set aside in a 
 cool place, it gradually, becomes more acid from day to day. This is called the 
 " acid fermentation." It seems to be due to the development of special fungi 
 (Fig. 249, a), and the process is accompanied by the deposition of uric acid (c), 
 
444 
 
 ACID FERMENTATION OF URINE. 
 
 acid sodium urate, in amorphous grains (S), and calcium oxalate (d). According 
 to Scherer, the fungus and the mucus from the bladder decompose part of the 
 urinary pigment into lactic and acetic acids. The latter sets free uric acid from 
 neutral sodium urate, so that free uric acid and sodium urate must be formed. 
 Butyric and formic acids have been found as abnormal decomposition products of 
 other urinary constituents. When the acid fermentation begins, the urine absorbs 
 
 Fig. 249. 
 
 Fig. 250. 
 
 
 !^4>f 
 
 8 «. 
 
 ft #*.*■* 't 4 ** #■ A M 
 
 ■te. 
 
 
 ■5. a*" 1 .■:<>" CD.../*\ 
 
 S? 
 
 
 
 Deposit in " acid fermentation " of urine, a, fungus ; 
 b, amorphous sodium urate ; c, uric acid ; rf, cal- 
 cium oxalate. 
 
 Deposit in ammoniacal urine (alkaline fermentation). 
 a, acid ammonium urate ; o, ammonio-magnesium 
 phosphate ; c, bacterium urese. 
 
 Fig. 251. 
 
 c\\) 
 
 ;>\'X' 
 
 K 
 
 ^ 
 
 ifli 
 
 ■(..j 
 
 y~ 
 
 '.VVV-i 
 
 Fig. 252. 
 
 
 
 
 
 Deposit from a case of catarrh of the urinary hladder (ammoniacal The more usual forms of triple phosphate 
 fermentation), a, detached epithelium ; />, pus corpuscles ; c, X 300. 
 
 triple phosphate ; d, micro-organisms. 
 
 oxygen (Pasteur). According to Briicke, it is the lactic acid formed from the 
 minute traces of sugar present in urine, which causes the acidity. According to 
 Rohmann, who recognizes the acid fermentation as an exceptional phenomenon, 
 the acids are formed from the decomposition of sugar, and from alcohol which 
 may be present accidentally. While the urine is still acid, it becomes turbid and 
 contains nitrous acid, whose source is entirely unknown. According to v. Voit 
 
ALBUMIN IN URINE. 445 
 
 and Hofmann, phosphoric acid and a basic salt are formed from acid sodium 
 phosphate, whereby part of the uric acid is displaced from sodium urate, thus 
 causing the formation of an acid urate. 
 
 Alkaline Fermentation. — When urine is exposed for a still longer time, 
 more especially in a warm place, it becomes neutral and ultimately ammoniacal, 
 i. e., it undergoes the alkaline fermentation (Fig. 250). 
 
 This condition is accompanied by the formation of the micrococcus ureae 
 {Pasteur, Co/in) and Bacterium ureae (Fig. 251), which cause the urea to take up 
 water, and decompose into C0 2 and ammonia. 
 
 Urea [CO(HN,),]2(H,0) = ammonium carbonate [(NH 4 ) 2 C0 3 ]. 
 
 The property of decomposing urea belongs to many different kinds of bacteria, including even the 
 sarcina of the lungs — whose germs seem to be universally diffused in the air. These organisms pro- 
 duce a soluble ferment (Musculus), which, however, only passes from the body of the cells into 
 the fluid after the cell or organism has been killed by alcohol [Sheridan Lea). 
 
 The presence of ammonia causes the urine to become turbid, and those sub- 
 stances which are insoluble in an alkaline urine are precipitated — earthy phos- 
 phates, consisting of the amorphous calcic phosphate, acid ammonium 
 urate (Fig. 250, a) in the form of small, dark granules covered with spines ; and, 
 lastly, the large, clear, knife-rest or "coffin-lid" form of ammonio-magnesic 
 phosphate, or triple phosphate (Fig. 252). [The last substance does not 
 exist as such in normal urine, but it is formed when ammonia is set free by the 
 decomposition of urea, the ammonia uniting with the magnesium phosphate. Its 
 presence, therefore, always indicates ammoniacal fermentation of the urine.] In 
 cases of catarrh or inflammation of the bladder, this decomposition may 
 take place within the bladder, when the urine always contains pus cells (Fig. 251, 
 b~) and detached epithelium (a). When much pus is present, the urine contains 
 albumin. Ammoniacal urine forms white fumes of ammonium chloride, when a 
 glass rod dipped in hydrochloric acid is brought near it. 
 
 [Significance of Triple Phosphate. — If urine be alkaline when it is passed, and the alkalinity 
 be due to a volatile alkali, i.e., to NH 3 , then decomposition of the urine has taken place, and this 
 kind of urine is a sure sign that there is disease of the genito-urinary mucous membrane.] 
 
 [When ammonia is added to normal urine, triple phosphate is precipitated in a 
 feathery form.] 
 
 264. ALBUMIN IN URINE (ALBUMINURIA).— Serum albumin 
 
 is the most important abnormal constituent in urine which engages the attention 
 of the physician. It is the albumin which occurs in blood (§ 32), and whose 
 characters are described in § 249. 
 
 Causes of Albuminuria. — l. Serum albumin may appear in urine without any apparent ana- 
 tomical or structural change of the renal tissues. This condition has been called by v. Bamberger 
 "Hematogenous albuminuria." It occurs but rarely, however, and sometimes in healthy individu- 
 als when there is an excess of albumin in the blood plasma [e.g., after suppression of the secre- 
 tion of milk), and after too free use of albuminous food. 2. As a result of increased blood pressure 
 in the renal vessels, e.g., after copious drinking. It may be temporary, or it may be persistent, as in 
 cases of congestion following heart disease, emphysema, chronic pleural effusions, infiltrations of the 
 lungs, and after compression of the chest, causing congestion in the pulmonary circuit, which extends 
 even into the renal veins (Schreiier), etc. 3. After section or paralysis of the vasomotor nerves of 
 the kidneys, which causes great congestion of these organs. The albuminuria, which accompanies 
 intense and long-continued abdominal pain, is brought about owing to a reflex paralysis of the renal 
 vessels (Fischel). 4. After violent muscular exercise. [Senator found that forced marches in young 
 recruits were very frequently followed by the appearance of albumin in the urine, which persisted 
 for several days.] Convulsive disorders, e.g., epilepsy, the spasms of dyspnoea after strychnin poi- 
 soning (Huppert); in shock of the brain, apoplexy, spinal paralysis, and violent emotions; the 
 excessive use of morphia, which, perhaps, acts on the vasomotor centres. 5. It may accompany 
 many acute febrile diseases, e.g., the exanthemata (scarlet fever), typhus, pneumonia and pyemia. 
 In these cases it may be due to the increase of temperature paralyzing the vessels, but more prob- 
 ably the secretory apparatus of the kidney is so changed (e.g., cloudy swelling of the renal epithe- 
 lium) that the albumin can pass through the renal membranes. 6. Certain degenerations and 
 inflammations of the kidneys at several of their stages. 7. Inflammation or suppuration in the ureter 
 
446 TESTS FOR ALBUMIN IN URINE. 
 
 or urinary passages. 8. Certain chemical substances which irritate the renal parenchyma, e.g., 
 cantharides, carbolic acid. 9. The complete withdrawal of common salt from the food. The albu- 
 min disappears when the common salt is given again (Wundl, E. Rosenthal). 10. The epithelium 
 may be in such a condition that it cannot retain the albumin within the vessels, due to imperfect 
 nourishment and functional weakness of the secretory elements. This includes the albuminuria of 
 ischaemia, and that after hemorrhage (Quincke), in anaemia, scorbutus, icterus, diabetes. 
 
 [Besides being derived from the secreting parenchyma of the kidney, albumin may be derived 
 by admixture with the secretions from any part of the urinary tract, including the vagina and 
 uterus in the female. In some cases the transudation of albumin is favored by changes in the 
 capillary walls, the albumin being forced through by the intravascular pressure. Sometimes albu- 
 minuria occurs during the course of severe typhoid fever, and in acute fevers generally where the 
 temperature is persistently above 40 C. (104° F.). The high temperature alters the filtering mem- 
 brane and permits the filtration of albumin.] 
 
 [Physiological Albuminuria. — This term has been applied to that condition of the urine where 
 traces of albumin are found in individuals apparently in perfect health. Johnson and Pavy cite 
 such cases, while Posner asserts that all urine — even healthy urine — contains traces of proteids, 
 whose presence is ascertained after concentrating the urine. It is safe to assume that normal urine 
 should give no reaction for albumin.] 
 
 The tests for albumin in urine depend upon the fact that it is precipitated 
 by various reagents. 
 
 [(d) Heller's Test. — Place 10 c.c. of the urine in a test glass, and pour in pure colorless HN0 3 
 so as to run down the side of the glass, forming a layer beneath the urine. A white zone 01 
 coagulated albumin indicates the presence of albumin. In this test it is important to wait a certain 
 time for the development of the reaction. In urines of high specific gravity, a haziness due to acid 
 urates may be formed above, where the two fluids meet, but its upper edge is not circumscribed. 
 The acid decomposes the neutral urates and forms a more insoluble acid salt. This cloud of acid 
 urates is readily dissolved by heat, while the albumin is not ; the latter is always a sharply-defined 
 zone between the two fluids. In very concentrated urine (rare), nitric acid may gradually precipitate 
 crystalline urea nitrate. In patients taking copaiba, nitric acid, by acting on the resin, causes a 
 slight milkiness.] 
 
 [(b) Boiling and Nitric Acid. — Place 10 c.c. of urine in a test tube and boil. If albumin be 
 present in small quantity, a faint haziness, which may be detected in a proper light, will be 
 produced. Add 10 or 12 drops of HNO s . If the turbidity disappears it is due to phosphates, 
 while if any remains it is due to albumin. If albumin be present in large quantity, a copious 
 whitish coagulum is obtained.] 
 
 [Precautions. — (a) In all cases, if the urine be turbid, filter it before applying any test. (b) 
 How to Boil. — Boil the upper strata of the liquid, and take care, if any coagulum be formed, that 
 it does not adhere to the side of the tube, else the tube is liable to break, (c) In performing this 
 test with a neutral solution, note when the precipitate falls, for albumin is precipitated about 70 
 C, phosphates not till about the boiling point, (d) Amount of Acid. — If too little (2 or 3 drops) 
 HNO s be added, or too much (30 or 40 drops), we may fail to detect albumin, although present.] 
 
 (c) Ferrocyanide Test. — By the addition of acetic acid and potassium ferrocyanide. [If albu- 
 min be present, a white flocculent precipitate separates in the cold. Dr. Pavy has introduced pel- 
 lets, consisting of a mixture of citric acid and sodic ferrocyanide. All that is required is to add 
 a pellet to the suspected urine. Oliver's papers. — Dr. Oliver uses papers, one saturated with 
 citric acid and another with ferrocyanide of potassium. The two papers are added to the clear 
 filtered urine. Other precipitants of albumin, such as small pieces of paper impregnated with 
 potassio-mercuric iodide, are used by Oliver.] 
 
 (d) By boiling Acid Urine. — If the urine be alkaline, although albumin may be present, it 
 is not precipitated by heat alone. We require to add acetic acid until a slightly acid reaction is 
 obtained. 
 
 Boiling may give a precipitate of earthy phosphates in an alkaline urine, owing to the C0 2 
 being driven off. This precipitate might be mistaken for albumin, but on adding acetic or nitric 
 acid, the earthy precipitate is dissolved, while the precipitate of albumin is not dissolved. In test- 
 ing for albumin, always use clear urine. If it is turbid, filter it. 
 
 1(e) Metaphosphoric acid is dissolved in water just before it is to be used and added to clear 
 urine (Hindenlang). Graham pointed out that metaphosphoric acid precipitated albumin. A 20 
 per cent, solution of the ordinary glacial phosphoric acid is a good test for albumin, but it also pre- 
 cipitates peptones. It, however, changes into ordinary phosphoric acid by keeping, and then it no 
 longer precipitates albumin.] 
 
 [(/) Acidulate 10 c.c. of urine with acetic acid, and add ]/(, of its volume of a concentrated 
 solution of sulphate of soda or magnesia. On heating, if albumin be present, a distinct cloudiness 
 is obtained.] 
 
 [(g) In picric acid, according to Dr. Johnson, we have a more delicate test for minute traces 
 of albumin than either heat or nitric acid, or than both these tests combined. It is used either in 
 the form of crystals or powder, or as a saturated aqueous solution. Take a four -inch column of 
 
HEMATURIA AND HEMOGLOBINURIA. 447 
 
 urine in a test tube, hold the tube in a slanting direction, and pour an inch of the picric acid solu- 
 tion on the surface of the urine, where, in consequence of its low specific gravity (1005), it mixes 
 only with the upper layer of the urine. It coagulates any albumin present. The precipitate occurs 
 at once, and is increased by heat, while the urate of soda, which is sometimes precipitated, is 
 soluble on heating.] 
 
 [Dr. Roberts regards any test for albumin which requires strong acidulation with an organic acid, 
 citric, acetic or lactic, as unsatisfactory, since it precipitates mucin. For this reason he rejects the 
 tungstate, mercuric iodide, and potassic ferrocyanide tests. Dr. Roberts regards the heat test, with 
 the addition of a small definite quantity of acetic acid, as the best test for the detection of small 
 quantities of albumin.] 
 
 1. Quantitative Estimation of albumin. — 100 c.c. of urine are boiled in a capsule, some 
 acetic acid being ultimately added, whereby the albumin is precipitated in flakes. The precipitate 
 is collected on a weighed, dried (no ), and ash free filter, and repeatedly washed with hot water, 
 then with alcohol, and completely dried in an air bath at 1 io°. Lastly, the dried filter with the 
 albumin is burned in a weighed platinum capsule, and the weight of the ash also deducted from it. 
 [This method is not available for the busy practitioner on account of the time it takes. Practically, 
 it is sufficient to compare from day to day the proportion that the precipitated albumin bears to the 
 bulk of the urine tested. A graduated tube may be used, so that after the precipitate has subsided 
 the physician may see whether it occupies one-fourth or one-tenth of the fluid, as the case may be.] 
 
 2. Globulin occurs only in albuminous urine (Senator, Edtefseti), and is frequently present. Its 
 presence is ascertained by adding powdered magnesium sulphate in excess to the urine ; when it 
 is present it is precipitated (§ 32). The more globulin there is in the presence of albumin, the 
 more difficult it is to precipitate it. [Sometimes, when an albuminous urine is dropped into a large 
 cylinder of water, each drop as it sinks is followed by a milky train, and when a sufficient number 
 of drops has been added, the water becomes opalescent, the opalescence disappearing on adding an 
 acid. The globulin is kept in solution by common salt and other neutral salts, but when these are 
 largely diluted, the globulin is precipitated (Hobertsy"] 
 
 3. Peptone (v. Frerichs, 18J1) occurs in some specimens of albuminous urine, but also in non- 
 albuminous urine (Gerhardt). Maixner found it constantly in the urine in all cases where suppu- 
 ration is present, e.g., in exudations, abscesses, resolution of pneumonia, and in articular rheumatism, 
 when the attack is passing off (v. Jaksch). Peptone occurs in pus, and the peptonuria in these 
 cases is a sign of the breaking up of the pus cells (Hofmeister). Also when many leucocytes are 
 broken up in the blood, or when large quantities of peptone are absorbed from the intestinal canal. 
 It is frequently found after childbirth. 
 
 Test. — Separate the albumin by boiling and the addition of acetic acid. Treat the filtrate with 
 three volumes of alcohol; this precipitates the peptone, which, when dissolved in water, gives the 
 characteristic reactions for peptone (j 166, I). 
 
 4. Propeptone occurs very rarely in osteomalacia and intestinal tuberculosis (Macynter and Bence 
 Jones). The urine is treated to saturation with NaCl and a large quantity of acetic acid added, and 
 filtered while hot, to separate the albumin and globulin. In the cold filtrate propeptone forms a 
 turbidity, which is redissolved by heat. The precipitate thrown down by HC1 and HNO s is soluble 
 by heat (JCuhne). The precipitate is isolated by filtration, and dissolved in a little warm water, 
 when it gives with HN0 3 a yellow reaction ; like peptone, the solution gives the biuret reaction. 
 
 5. Egg albumin appears in the urine when much egg albumin is taken in the food, and also 
 when it is injected into the blood vessels (J 192, 4). According to Semmola, the albumin present 
 in the urine in Bright's disease has undergone a molecular change (similar to egg albumin), and 
 hence it is excreted. 
 
 6. Mucus is present in large amount, especially in catarrh of the bladder. It contains numerous 
 mucus corpuscles, which are scarcely distinguishable from pus corpuscles. They contain albumin, 
 so that urine containing much mucus is albuminous ; mucin is not precipitated by heat, but acetic 
 acid gives a flocculent precipitate in clear urine. [Minute traces of mucin occur normally in urine. 
 If clear, normal urine be set aside for a short time, a flocculent haziness, like a cloud of cotton wool, 
 is seen floating in the urine. This is mucus entangling a few epithelial cells from the genitourinary 
 tract. Mucin Reaction. — According to W. Roberts, the addition of a concentrated solution of 
 citric acid to urine, as in Heller's test (\ 264, a), where the two fluids meet, causes an opalescent 
 zone gradually to be formed above the layer of acid.] 
 
 265. BLOOD IN URINE (HEMATURIA)— HEMOGLOBINURIA.— I. Source 
 of the Blood. — (1) In haematuria, the blood may come from any part of the urinary apparatus. 
 I. In hemorrhage from the kidney, the amount of blood is usually small and well mixed with the 
 urine. The presence of " blood cylinders," long, microscopic blood coagula, casts of the uriniferous 
 tubules, washed out of them by the urine, are characteristic when they are found in the urine (Fig. 
 263). The urine usually has a smoky appearance. [The urine slowly dissolves out the coloring 
 matter, the stroma of the corpuscles after a time being deposited as a brownish sediment. The 
 smoky hue occurs only in acid urine ; if the urine becomes alkaline, the hue becomes brighter red.] 
 The blood corpuscles show peculiar changes of form [they become crenated - ] (Fig. 253), and exhibit 
 evidence of division, due to the action of urea on them ($ 5). Large coagula are never found in 
 
448 
 
 HEMATURIA AND HEMOGLOBINURIA. 
 
 urine mixed with blood derived from the kidney. 2. In hemorrhage from the ureter, we occa- 
 sionally find worm-like masses of clotted blood, casts of the canal of the ureter. 3. The relatively 
 largest coagula occur in hemorrhage from the bladder. In all cases where blood is present, we 
 must examine microscopically for the blood corpuscles, and it may be for coagula of fibrin In acid 
 urine, blood corpuscles, but never in rouleaux, may be found after two to three days in urine. The 
 
 Fig 
 
 Crenated red blood corpuscles in urine X 350. 
 
 Fig. 254. 
 
 Peculiar changes of the red blood corpuscles in renal hematuria {Friedreich}. 
 
 blood corpuscles settle as a red sediment at the bottom. If the hemorrhage is copious, many retain 
 their original shape; but if the urine is very concentrated, they may become crenated. 
 
 When there is a small and slow hemorrhage from ruptured, small capillaries, the red blood cor- 
 puscles are of unequal Size, many ^ to ^ the size of normal, while the pigment has become brownish 
 yellow (Fig. 255). 
 
BLOOD IN URINE. 
 
 449 
 
 If a hemorrhage of this kind is accompanied by catarrhal inflammation of the bladder, there 
 is found between the red, numerous shriveled leucocytes (Fig. 255), which in freshly-passed urine 
 often exhibit lively amoeboid movements. If the urine be alkaline, as it usually is, crystals of triple 
 phosphate also occur. 
 
 If the remains of the red blood corpuscles become very pale, their presence may be frequently 
 ascertained by adding iodine in a solution of KI (Fig. 254). Blood is constantly present in the 
 urine during menstruation. 
 
 Fig. 255. 
 
 Colored and (a) colorless blood corpuscles of various forms. 
 
 Fig. 256. 
 
 Shriveled blood corpuscles in urine (catarrh of the bladder), with numerous lymph corpuscles, 
 and crystals of triple phosphate, X 350. 
 
 II. Hemoglobinuria is quite distinct from hematuria. It depends upon the excretion of 
 hsemoglobin as such through the kidneys, and it is produced when haemoglobin occurs free 
 within the blood vessels, as in cases where the colored blood corpuscles have been dissolved inside 
 the blood vessels (haemocytolysis). It occurs when foreign blood is transfused, e.g., when lamb's 
 blood is transfused into man. The foreign blood corpuscles are dissolved in the blood of the 
 recipient, and the haemoglobin appears in the urine (j| 102). In addition, microscopic "cylinders," 
 29 
 
450 
 
 / 
 
 BILE IN URINE. 
 
 consisting of a globulin-like body tinged yellow with haemoglobin, may likewise be found in the 
 urine. It also occurs in cases of severe burns (g 10, 3) ; after decomposition of the blood in pyaemia, 
 scorbutus, purpura, severe typhus, after respiring arseniuretted hydrogen, and after the passage of 
 azobenzol (Baumann and Herter), of naphtol (Kaposi), pyrogallic acid, potassic chlorate, chloral, 
 phosphorus, or carbolic acid into the circulation. [The injection of laky blood, water, ether, 
 glycerine (Adams), or toluylendiamin (Afanassiew), also causes it, and in such cases Afanassiew 
 asserts that the Hb passes out through the glomeruli, while brown degeneration products of the red 
 blood corpuscles, which are dissolved by these agents, were found in the convoluted tubules.] 
 These substances dissolve the red blood corpuscles. Sometimes it occurs periodically from causes 
 and conditions, as yet but little understood, e. g., the application of cold to the skin. 
 
 Tests for Blood in Urine. — 1. The color of bloody urine shows every tint, from a faint red to 
 a dark, blackish brown, according to the amount of blood present. The urine is often turbid. 
 
 2. Urine containing blood or blood pigment contains albumin. 
 
 3. Heller's Blood-test. — Add to urine half its volume of solution of caustic potash, and heat 
 gently. The earthy phosphates are precipitated, and they carry the hsematin with them, falling as 
 garnet-red flocculi. [This is not a reliable test.] 
 
 4. Haemin Test. — The colored earthy phosphates may be collected on a filter, and from them 
 hsemin may be prepared as directed in \ 19. 
 
 Fig. 257. 
 
 P # 
 
 Spectroscope for investing the presence of haemoglobin in urine. 
 
 5. Almen's Test. — Add to urine, freshly-prepared tincture of guaiacum and ozonized ether ; a 
 blue color indicates the presence of blood (\ 37). 
 
 6. Spectroscope (see \ 14). Fig. 257 shows the arrangement of the apparatus. The urine is 
 placed in a glass vessel, D, with parallel sides, 1 centimetre apart (hsematinometer). Light 
 from a lamp, E, passes through the fluid. The lamp, F, illuminates the scale, which is seen by the 
 observer through the telescope, A. (a) Fresh urine containing blood gives the spectrum of 
 oxyhsemoglobin (Fig. 14). (b) When bloody urine is exposed for some time, especially in a warm 
 place, it becomes more acid, and assumes a dark, brownish.black color. The haemoglobin becomes 
 changed into methaemoglobin (§ 15). It is precipitated by lead acetate, which does not precipi- 
 tate oxyhsemoglobin; the spectrum of methaamoglobin resembles that of hsematin in an acid solu- 
 tion (§ 15, Fig. 14). The two spectra may be combined, (c) The microscopic investigation 
 must never be omitted. The shape of the corpuscles may vary considerably, as is shown in Figs. 
 253 to 255. 
 
 266. BILE IN URINE (CHOLURIA).— The physiological conditions which cause the 
 bile constituents to appear in the urine are mentioned in part at \ 180. ' 
 
 Haematogenic, or Anhepatogenic Icterus (Quincke), occurs when bilirubin (<j 20) is formed 
 from extravasated blood by the action of the connective-tissue corpuscles, so that bile pigments, in 
 addition to coloring the tissues, pass into the urine. 
 
SUGAR IN URINE. 451 
 
 I. Bile Pigments. — Their presence is ascertained by Gmelin-Heintz's test. Green (Bili- 
 verdin) is the characteristic hue in the play of colors obtained with this test, which is fully described 
 in I 177. 
 
 Modifications of the Test. — 1 . If icteric urine be filtered through filtering or blotting paper, 
 a drop of nitric acid containing nitrous acid, when applied to the inner surface of the spread-out 
 filter, gives a yellowish colored ring (Rosenbach). 2. In order that the reaction may not take place 
 too rapidly, add a concentrated solution of sodic nitrate, and then slowly pour in sulphuric acid 
 (Fleisckl). 3. On shaking 50 c.c. of icteric urine with 10 c.c. of chloroform, the bilirubin is dis- 
 solved by the latter. On adding bromide water, a beautiful ring of colors is obtained (Maly). If 
 the chloroform extract be treated with ozonized turpentine and dilute caustic potash, a green color, 
 due to biliverdin, occurs in the watery fluid (Gerhardt). 
 
 In slight degrees of jaundice, urobilin alone may be found (J 261, 1) [Quincke). 
 
 In persistent high fever, the urine contains especially biliprasin (Huppert). If it contains 
 choletelin alone, add to the urine some hydrochloric acid, and examine it with the spectroscope, 
 which gives a pale absorption band between b and F ({! 177, 3,/). 
 
 Haematoidin. — Sometimes crystals of hcematoidin (jj 20, Fig. 14) appear in the urine, especially 
 when blood corpuscles are dissolved within the blood stream ; occasionally in scarlet fever and 
 typhus, and sometimes in cases of periodic hsemoglobinuria. The breaking up of old blood clots 
 in the urinary passages, as in pyonephrosis (TZbstein), or during the dissolution of necrotic areas 
 (Hofmann and Ultzmann) produces them, and similar crystals occur in analogous cases in the 
 sputum (I 138). In jaundice due to congestion ($ 180), the identical crystalline substance, bilirubin, 
 is found. 
 
 II. Bile acids occur in largest amount in absorption jaundice, but they are never present to any 
 extent. 
 
 The test is described at \ 177, 2, the cane-sugar solution consisting of 0.5 grm. to 1 litre of 
 water. If the urine be dilute, it is advisable to concentrate it on a water bath. v. Pettenkofer's 
 test may be used with the alcoholic extract of the nearly dry residue, but no albumin must be present. 
 Dragendorff found 0.8 grm. in 100 litres of normal urine. 
 
 Strassburg's Modification. — Dip filter paper into the urine, to which a little cane sugar has 
 been added ; dry the paper, and apply to it a drop of sulphuric acid. A violet-red color is obtained 
 after a short time. 
 
 [Hay's Reaction. — The effect of bile salts in lessening the surface tension of a liquid, and thus 
 rapidly causing the precipitation of a dry powder like sulphur, when placed in the liquid, is the 
 basis of this test (§ 177).] 
 
 267. SUGAR IN URINE (GLYCOSURIA). — Diabetes Mellitus.— The excessively 
 minute trace, of grape sugar, or dextrose, which is constantly present in normal urine, sometimes 
 becomes greatly increased, and constitutes the conditions of diabetes mellitus and glycosuria. 
 The physiological conditions which determine this result are given at \ 175. In this condition, the 
 quantity of urine is greatly increased; it may reach 10 or more litres. Many pints may be passed 
 daily. [The usual abnormal amount of sugar is from 1 to 8 per cent., although 15 per cent, has 
 been found, i. e., found from 5 to 50 grs. per fluid oz., or 300 to 4000 grs. in twenty-four hours 
 (Tyson).} The specific gravity is also increased (1030 to 1040). [In a case where a large 
 amount of urine is passed of a pale color and a specific gravity above 1030, always suspect sugar.] 
 A diabetic person gives off relatively more water by the kidneys and less by the skin (and lungs ?) 
 than a healthy person. The color is very pale yellow, although the amount of pigment is, by no 
 means, diminished; it is only diluted [the depth of the color being inversely as the quantity passed]. 
 The amount of the nitrogenous urinary excreta is increased. The sugar is increased by a diet of 
 carbohydrates and diminished by an albuminous diet. The uric acid and oxalate of lime are often 
 increased at the commencement of the disease, while yeast cells are constantly present after the 
 urine has been exposed to the air for some time. 
 
 Sugar has been found occasionally after poisoning with, or after the use of, morphia, CO, chloral, 
 chloroform, curara; after the injection of ether and amyl-nitrite into the blood ; and in gout, inter- 
 mittent fever, cholera, cerebro-spinal meningitis, hepatic cirrhosis, and cardiac and pulmonary 
 affections. 
 
 Tests. — Any of the tests described at § 149 may be used, but the urine must be free from ajbumin. 
 The quantitative estimation by fermentation and the titration methods are described in \ 149. [The 
 tests for grape sugar described in \ 149 are (1) Trommer's; (2) Fehling's; (3) Moore & Heller's; 
 (4) Bottger's; (5) Mulder and Neubauer's ; (6) Fermentation test.] 
 
 7. Worm Miiller recommends the following modification of Fehling's test: Use a 2.5 per cent, 
 solution of cupric sulphate solution, and another of 10 parts of sodio-potassic tartarate in 100 parts 
 of a 4 per cent, solution of soda. Boil 5 c. cm. of urine in a test tube, while in a second test tube 
 is boiled I to 3 c. cm. of the copper solution and 2.5 c. cm. of the potassio-tartrate solution. The 
 boiling of both fluids is stopped simultaneously, and after 20 to 25 seconds, the contents of one test 
 tube are added to those of the other, but without shaking the mixture, the reduction taking place 
 spontaneously. 
 
 8. Nylander's modification of Bottger's test is also good (§ 149). 
 
452 TESTS FOR SUGAR IN URINE. 
 
 [9. Picric Acid and Potash Test. — Braun showed that grape sugar, when boiled with picric 
 acid and potash, reduces the yellow picric acid to the deep-red picramic acid, the depth of the color 
 depending on the amount of sugar present. Dr. Johnson uses this test for detecting the presence of 
 sugar in urine, and also for estimating the amount of sugar present, the depth of the red color 
 obtained in boiling being compared with a standard dilution of ferric acetate. In doing the test, 
 use I drachm of urine, % a drachm of liquor potassse, and 10 minims of picric acid solution ; make 
 up to 2 drachms with distilled water, and boil the mixture for one minute. This test indicates the 
 presence of 0.6 grain of sugar per fluidounce of normal urine. Dr. Johnson claims for this lest 
 that it possesses all the advantages of the other tests, while it is not affected by uric acid or any 
 other normal ingredient of urine ; neither does the presence of albumin interfere with the action of 
 the test as it does with all the forms of copper testing.] 
 
 [10. Indigo-carmine Test. — A blue solution of this substance, when boiled with diabetic urine 
 containing sodic carbonate, changes from a blue to a violet, purple-red, yellow, and, finally, straw- 
 yellow color. After cooling and exposure to the air, the various colors are obtained in the reverse 
 order until the mixture becomes blue again. Dr. Oliver uses this test in the form of test papers. 
 One bibulous paper is impregnated with the indigo carmine and the other with sodic carbonate. 
 Drop one of the test papers and a sodic carbonate paper into a test tube containing lj£ inches of 
 water; heat gently, when a blue solution is obtained. Add the urine slowly, one drop at a time, 
 and boil the mixture, observing any change of color by holding the tube against a white surface 
 below the level of the eye. Uric acid and urates, which reduce Fehling's solution, do net affect 
 the carmine test, nor does kreatinin, although it reacts with the picric acid test.] 
 
 [Quantitative Estimation — (a) Fermentation Test (§ 150). Take 4 oz. (120 c. c.) of the 
 urine ; add a lump of German yeast about the size of a walnut, lightly cork the bottle, and place it 
 aside for twenty-four hours in a moderately warm place, e.g., on the mantelpiece. Take the spe- 
 cific gravity before and after the fermentation. Thus, if the specific gravity be 1038 before and 
 1013 afterward, the difference, or "density lost," is 25, which gives 25 grs. of sugar per fluid oz. 
 (Roberts). If it be desired to get the percentage, multiply the density lost by 0.23 ; thus, 25 X °- 2 3 
 = 5.69 in 100 parts.] 
 
 \{b) Volumetric Analysis. — 10 c. c. of Fehling's solution = .05 gramme of sugar. 
 
 I. Ascertain the quantity of urine passed in twenty-four hours. 2. Filter the urine, and remove 
 any albumin present by boiling and filtration. 3. Dilute 10 c. c. of Fehling's solution with about 
 twenty times its volume of distilled water, and place it in a white porcelain capsule on a wire gauze 
 support, under a burette. (It is diluted because any change of color is more easily observed.) 4. 
 Take 5 c. c. of the urine and 95 c. c. of distilled water, and place the diluted urine in a burette. 
 5. Gradually boil the diluted Fehling's solution, and while it is boiling, gradually add the diluted 
 urine from the burette, until all the cuprous oxide is precipitated as a reddish powder, and the super- 
 natent fluid has a straw-yellow color, not a trace of blue remaining. Read off the number of c. c. 
 of dilute urine employed. Say 36 c. u. were used — that, of course, represents 1 .8 c. c. of the 
 original urine. Suppose the patient passes 1550 c.c, and as 1.8 c. c. of urine reduced all the cupric 
 oxide in the 10 c. c. of Fehling's solution, it must contain .05 gramme sugar; hence, 
 
 1.8 : 1550 : : .05 : ^2 — -*■ ' -* = 237.5 grammes of sugar passed in 24 hours.] 
 1.8 
 
 (c) According to Worm Muller, the polarization method is almost valueless for diabetic urine. 
 
 If large quantities of dextrose are taken in the food, a part of it (and more in diabetic persons) 
 appears in the urine. Laevulose, when taken internally, does not increase the amount of sugar in 
 diabetes. The free use of starch does not cause glycosuria in health, but in diabetes it increases 
 the amount of sugar. A large consumption of cane- or milk sugar causes the passage of small 
 quantities of both of these sugars into the urine in health, while in diabetes the amount of dextrose 
 is increased ( Worm Mutter). According to Kiilz, in diabetic persons cane sugar is split up into 
 grape-fruit sugar, the latter being used up in the body, the former partly excreted ; and the same is 
 the case with milk sugar. 
 
 In severe cases of diabetes mellitus, Kiilz found the left rotatory ^-oxybutyric acid (the next highest 
 analogue of lactic acid) in the urine, from which acetic acid is formed by oxidation (\ 175) which 
 in its turn readily yields C0 2 and aceton. a-crotonic acid is formed in urine by the removal of 
 water from oxybutjric acid in the urine in diabetes (Stadelmann). The administration of aceton 
 causes albuminuria, and this may in part explain in some cases the complication of albuminuria in 
 diabetes (Albertoni and Pisenti). 
 
 [Preparation of Fehling's Solution.— 34.64 grammes of pure crystalline cupric sulphate are 
 powdered and dissolved in 200 c.c. of distilled water; in another vessel dissolve 173 grammes of 
 Rochelle salts in 480 c.c. of pure caustic soda, specific gravity 1.14. Mix the two solutions, and 
 dilute the deep colored fluid which results to 1 litre. N. B. — Fehling's solution ought not to be 
 kept too long ; it is apt to decompose, and should therefore be preserved from the light, or protected 
 with opaque paper pasted on the bottle. Some other substances in urine, e.g., urates and uric acid, 
 reduce cupric oxide.] 
 
 Aceton, or Aceton-yielding substance, probably aceto-acetic acid, is sometimes found in diabetic 
 urine. It has a peculiar venous odor, and it has been detected in the urine during fever. Gerhardt 
 described a peculiar substance in diabetic urine, which gave a deep red color with perchloride of 
 
MILK, SUGAR AND OTHER SUBSTANCES IN URINE. 
 
 453 
 
 iron. This substance is probably diacetic ether, and he considered it to be the source of aceton ; 
 but it is more probably derived from aceto-acetic acid. Tests for Aceton. — (i) Perchloride of 
 iron = Burgundy-red color ; but this is not reliable. (2) Lieben suggested an iodoform test. Dis- 
 solve 20 grains of KI in fluidrachm of Hq. potassse, and boil the fluid. Pour the suspected urine 
 on the surface, when a ring of phosphates is deposited from the urine by the hot alkaline solution. 
 If aceton be present, after a time the deposit becomes yellow, and yellow granules of iodoform 
 appear and sink to the bottom of the test tube [Halfe). The only other substance which may be 
 met with in the urine giving this reaction is lactic acid.] 
 
 [Picro-Saccharimeter. — G. Johnson uses a stoppered bottle 12 inches long and ^ inch wide, 
 graduated in Jj and T ^ (Fig. 257, a). To it is fixed a shorter bottle containing the standard 
 iron solution Tor comparison, a standard solution, composed of liquor ferri perchloride 5 j, Hq. 
 amnion, acetatis giv, glacial acetic acid giv, liq. ammonite iji, and water to make up ^iv. All 
 B. P. preparations give a color identical with a solution containing 1 gr. of grape sugar per oz., 
 reduced by picric acid and afterward diluted four times, so that this tint = *£ gr. of sugar per oz. 
 
 Fig. 257 a. 
 
 Fig. 258. 
 
 Inosit crystallized partly from alcohol and partly 
 from water (after Funke). 
 
 Picro-saccharimeter of 
 G. Johnson. 
 
 After reducing the sugar with the picric acid, pour into the tall tube the dark, saccharine liquid pro- 
 duced by boiling to occupy ten divisions of the tube, and add distilled water cautiously until the color 
 approaches that of the standard ; read off the level of the fluid. The amount of sugar present is 
 determined from the amount of water added. In making the test, the picric acid must be added in 
 proportion to the amount of sugar added.] 
 
 Milk sugar is sometimes found in the urine of women who are nursing ; when the secretion of 
 milk is arrested, absorption taking place from the breasts (Kirsten, Spiegelberg). Laevulose is 
 sometimes found in diabetic urine {\ 252). 
 
 Dextrin has also been found in diabetic urine. Inosit, or muscle sugar (j! 252), is sometimes 
 found in diabetes, in polyuria (Mosler), and albuminuria. It is found in traces, even in normal 
 urine. Occasionally, after thepiqure in animals ($ 175), inosit, instead of grape sugar, appears in 
 the urine (Fig. 258). In testing for inosit, remove the grape sugar by fermentation, and the albumin 
 by heat, after the addition of a few drops of acetic acid and sodic sulphate. Some of the filtrate 
 is evaporated nearly to dryness on a capsule. To the residue add two drops of mercuric nitrate 
 
454 
 
 CYSTIN, LEUCIN AND TYROSIN. 
 
 (Liebig's titration fluid for urea), which gives a yellow precipitate. When this colored residue is 
 spread out and carefully heated, a dark-red color, which disappears on cooling, is obtained ( Gallois, 
 Kulz). [Inosit gives a green when boiled with Fehling's solution.] 
 
 268. CYSTIN. — This left rotatory body, CjHj 2 N 2 S 2 4 (Kulz, Baumann), occurs very seldom 
 in large amount in urine, although it seems to be a constituent of normal urine. It may be in solu- 
 tion or in the form of hexagonal crystals (Fig. 259, A). It is insoluble in water, alcohol, and ether, 
 but easily soluble in ammonia, from which solution it may be crystallized. According to Baumann 
 
 Fig. 259. 
 
 A, Crystals of cystin; B, oxalate of lime; c, hourglass forms of B, 
 
 Fig. 260. 
 
 a a, Leucin balls ; b b, tyrosin sheaves ; c, double balls of ammonium urate. 
 
 and Preusse, there are intermediate products of the metabolism, from which are furnished the 
 materials necessary for the formation of Cystin. During normal metabolism these materials undergo 
 further changes, and the sulphur appears oxidized in the urine as sulphuric acid. In rare cases 
 these oxidations do not take place, and then the sulphur appears in the cystin of the urine 
 (Stadthagen). 
 
 26g. LEUCIN=C 6 H 13 N0 2 . TYROSIN=C 9 H I1 N0 3 .— Both bodies occur in the urine 
 in acute yellow atrophy of the liver, and in poisoning by phosphorus. (Their formation during 
 
DEPOSITS IN URINE, 
 
 455 
 
 pancreatic digestion has been referred to in \ 17b, II.) As the urea excreted is usually diminished 
 at the same time, it is assumed that, in these diseases, the further oxidation of the derivatives of the 
 proteids is interfered with. Leucin, which is either precipitated spontaneously or obtained after 
 evaporating an alcoholic extract of the concentrated urine, occurs in the form of yellowish, brown 
 balls (Fig. 260, a a), often with concentric markings, or with fine spines on their surface. When 
 heated, it sublimes without fusing. 
 
 Tyrosin forms silky, colorless sheaves of needles (Fig. 260, b b). When boiled with mer- 
 curic nitrate and nitric acid it gives a red color, and afterward a brownish-red precipitate. When 
 slightly heated with a few drops of concentrated sulphuric acid, it dissolves with a temporary deep 
 red color. On diluting with water, adding barium carbonate until it is neutralized, boiling, filter- 
 ing, and adding dilute ferric chloride, a violet color is obtained (Piria, Stadeler). 
 
 270. DEPOSITS IN URINE. — Deposits may occur in normal as well as 
 in pathological urine, and they are either "organized" or "unorganized." 
 
 I. ORGANIZED DEPOSITS.— A. Blood: red and white blood corpuscles and sometimes 
 fibrin (Figs. 253-255). 
 
 B. Pus, in greater or less amount, in catarrh or inflammation of the urinary passages. Pus cells 
 exactly resemble colorless blood corpuscles (Figs. 7, 256). Donne's Test. — Pour off the super- 
 
 d 
 
 «, epithelium from the human urethra ; 6, vagina ; c, prostate ; d, Cowper's glands ; e , Littre's 
 glands ; f, female urethra ; g, bladder. 
 
 natent fluid and add a piece of caustic potash to the deposit ; if it be pus it becomes gelatinous, 
 ropy, and more viscid (alkali-albuminate). Mucus, when so acted on, becomes more fluid and 
 mixed with flocculi. 
 
 C. Epithelium of various forms occurs, but it is not always possible to say whence it is derived 
 (Fig. 261). 
 
 D. Spermatozoa may be present (Fig. 248, a). 
 
 E. Lower organisms occur in the urinary passages very seldom, but they may be present, e.g., 
 in the bladder, when germs are introduced from without by means of a" dirty catheter. [Before 
 introducing a catheter into the bladder one ought always to make sure that the instrument is perfectly 
 aseptic] Micrococci are found in the urine in certain diseases, e.g., diphtheria. The following 
 forms are distinguished : — 
 
 1. Schizomycetes {i 184). Normal human urine contains neither schizomycetes nor their 
 spores. In pathological conditions, however, fungi may pass from the blood into the urinary tubules 
 and thus reach the urine (Leube). During the alkaline fermentation of urine, micrococci, rod- 
 shaped bacteria or bacilli (Figs. 250, 251, may occur). Sarcinas belong to the above group 
 (2 J 86). 
 
 2. Saccharomycetes (fermentation fungi) : (a) The fungus of the acid urine fermentation (S. 
 urinae) consists of small, bladder-like cells arranged either in chains or in groups (Figs. 251, d; 
 
456 
 
 TUBE CASTS IN URINE. 
 
 262, c). {b) Yeast (S. fermentum) occurs in diabetic urine, as oval cells with a dotted, eccentrically 
 placed nucleus (Fig. 262, d). 
 
 3. Phytomycetes (moulds) occur in putrid urine (Fig. 262, e). They are without clinical sig- 
 nificance. 
 
 F. Tube Casts. — The occurrence of tube casts, i.e., casts of the uriniferous tubules \Henle, 
 1837) is of great importance in connection with the diagnosis of renal diseases. If these structures 
 
 Fig. 262. 
 
 , micrococci in short chains and groups ; b, sarcinas ; c. fungi from acid fermentation ; d, yeast 
 cells from diabetic urine ; e, mycelium of a fungus. 
 
 Fig. 263. 
 
 a, blood casts ; b, granular cast ; c, amyloid or waxy cast. 
 
 are relatively thick and straight, they probably come from the collecting tubules, but if they are 
 smaller and twisted, they probably come from the convoluted tubules. There are various forms of 
 tube casts : 1. Epithelial casts, consisting of the actual cells of the uriniferous tubules. They 
 indicate that there is no very great change going on, but only that, as in catarrhal inflammation of 
 any mucous membrane, the epithelium is in process of desquamation. 2. Hyaline casts (Fig. 264) 
 
DETECTION OF URINARY DEPOSITS. 
 
 457 
 
 are quite clear and homogeneous, usually long and small; sometimes they are " finely granular," 
 from the presence of fat or other particles. They are best seen after the addition of a solution of 
 iodine. They are probably formed from albumin, which passes into the uriniferous tubules. They 
 are dissolved in alkaline urine, while acid urine favors their formation. They usually occur in the 
 late stages of renal disease, after the tubular epithelium has been shed. 3. Coarsely granular 
 casts (Fig. 263, />), brownish-yellow 6paque, and granular, usually broader than 2. There are vari- 
 ous forms. Not unfrequently there are fatty granules, and, it may be, epithelial cells in them. 4. 
 Amyloid casts occur in amyloid degeneration of the kidneys (Fig. 263, c). They are refractive 
 and completely homogeneous, and give a blue color ^myloid reaction) with sulphuric acid and 
 iodine. 5. Blood casts occur in capillary hemorrhage of the kidney, and consist of coagulated 
 blood entangling blood corpuscles (Fig. 263, a). When tube casts are present, the urine is always 
 albuminous. 
 
 II. Unorganized Deposits. — Some of these are crystalline and others are amorphous, and 
 they have been referred to in treating of the urinary constituents. 
 
 271. SCHEME FOR DETECTING URINARY DEPOSITS.— I. In acid urine there 
 may occur : — 
 
 1. An amorphous granular deposit : 
 
 (a) Which is dissolved by heat and reappears in the cold ; the deposit is often reddish in color 
 
 = urates (Fig. 249). 
 (i) Which is not dissolved by heat, but is dissolved by acetic acid, but without effervescence 
 = probably tribasic calcic phosphate. 
 
 Fig. 264. 
 
 Hyaline casts. 
 
 (c) Small, bright, refractive granules, soluble in ether = fat or oil granules (§ 41) (Lipsemia). 
 
 Fat occurs in the urine, especially when the round worm, Filaria sanguinis hominis, is 
 present in the blood ; sometimes, along with sugar, in phthisis, poisoning with phos- 
 phorus, yellow fever, pyaemia, after long-continued suppuration, and lastly, after the 
 injection of fat or milk into the blood (§ 102). It occurs also in fatty degeneration of 
 the urinary apparatus, admixture with pus from old abscesses, and after severe injuries to 
 bones. In these cases attention ought to be directed to the presence of cholesterin and 
 lecithin. Very rarely is the fat present in such amount in the urine as to form a cream 
 on the surface (chyluria). 
 2. A crystalline deposit may be — 
 
 (a) Uric acid (Figs. 242, 243, 249). 
 
 (6) Calcium oxalate (Figs. 249, 259) — octahedra insoluble in acetic acid. 
 
 \c) Cystin (Fig. 259). 
 
 (d) Leucin and tyrosin — very rare (Fig. 260). 
 II. In alkaline urine there may occur — 
 
 1 . A completely amorphous granular deposit, soluble in acids without effervescence = tri- 
 
 basic calcic phosphate. 
 
 2. Sediment crystalline, or with a characteristic form. 
 
 (a) Triple phosphate (Figs. 250, 251, 252, and 256), soluble at once in acids. 
 
458 URINARY CALCULI. 
 
 (i) Acid ammonium urate — dark -yellowish, small balls often beset with spines, also amor- 
 phous (Figs. 250 and 260). 
 
 (c) Calcium carbonate — small whitish balls or biscuit-shaped bodies. Acids dissolve them 
 
 with effervescence (Fig. 248). 
 
 (d) Leucin and tyrosin (Fig. 260) — very rare. 
 
 '(<?) Neutral calcic phosphate and long plates of tribasic magnesic phosphate (Fig. 248). 
 Organized deposits may occur both in alkaline and in acid urine; pus cells are more abundant 
 in alkaline urine, and so are the lower vegetable organisms. 
 
 272. URINARY CALCULI. — Urinary concretions may occur in granules the size of sand, or 
 in masses as large as the fist. According to their size they are spoken of as sand, gravel, stone or 
 calculi. They occur in the pelvis of the kidney, ureters, bladder and sinus prostaticus. 
 
 We may classify them as follows ( Ultzmann) : — 
 
 1 . Calculi, whose nucleus consists of the sedimentary forms that occur in acid urine (primary 
 formation of calculi). They are all formed in the kidney, and pass into the bladder, where they 
 enlarge according to the growth of the crystals in the urine. . 
 
 2. Calculi, which are either sedimentary forms from alkaline urine, or whose nucleus consists 
 of a foreign body (secondary formation of calculi). They are formed in the bladder. 
 
 The primary formation of calculi begins with free uric acid in the form of sheaves (Fig. 242, c) 
 which form a nucleus, with concentric layers of oxalate of lime. The secondary formation occurs 
 in neutral urine by the deposition of calcic carbonate and crystalline calcic phosphate ; in alkaline 
 urine, by the deposition of acid ammonium urate, triple phosphate and amorphous calcic phosphate. 
 
 Chemical Investigation. — Scrape the calculus, burn the scrapings on platinum foil to ascertain 
 if they are burned or not. 
 
 I. Combustible concretions can consist only of organic substances. 
 
 (a) Apply the 1 murexide test (g 259, 2), and if it succeeds uric acid is present. Uric acid cal- 
 culi are very common, often of considerable size, smooth, fairly hard, and yellow to reddish-brown 
 in color. 
 
 (b) If another portion, on being boiled with caustic potash, gives the odor of ammonia (or when 
 the vapor makes damp turmeric paper brown, or if a glass rod dipped in HC1 and held over it gives 
 white fumes of ammonium chloride), the concretion contains ammonium urate. If b gives no 
 result, pure uric acid is present Calculi of ammonium urate are rare, usually small, of an earthy 
 consistence, i.e., soft and pale yellow or whitish in color. 
 
 (c) If the xanthin reaction succeeds (£ 260), this substance is present (rare). Indigo has been 
 found on one occasion in a calculus (Ord). 
 
 (d) If, after solution in ammonia, hexagonal plates (Fig. 259, A) are found, cystin is present. 
 (<?) Concretions of coagulated blood or fibrin, without any crystals, are rare. When burned 
 
 they give the odor of singed hair. They are insoluble in water, alcohol and ether; but are soluble 
 in caustic potash, and are precipitated therefrom by acids. 
 
 (f) Urostealith is applied to a caoutchouc like, soft elastic substance, and is" very rare. When 
 dry it is brittle and hard, brown or black. When warm it softens, and if more heat be applied 
 it melts. It is soluble in ether, and the residue after evaporation becomes violet on being heated. 
 It is soluble in warm caustic potash, with the formation of a soap. 
 
 II. If the concretions are only partly combustible, thus leaving a residue, they contain organic 
 and inorganic constituents. 
 
 (a) Pulverize a part of the stone, boil it in water, and filter while hot. The urates are dissolved. 
 To test if the uric acid is united with soda, potash, lime or magnesia, the filtrate is evaporated and 
 burned. The ash is investigated with the spectroscope (§ 14), when the characteristic bands of 
 sodium or potash are observed. Magnesic urate and calcic urate are changed into carbonate by 
 burning. To separate them dissolve the ash in dilute hydrochloric acid and filter. The filtrate is 
 neutralized with ammonia, and again redissolved by a few drops of acetic acid. The addition of 
 ammonium oxalate precipitates calcic oxalate. Filter and add to the filtrate sodic phosphate and 
 ammonia, when the magnesia is precipitated as ammonio-magnesic phosphate. 
 
 (b) Calcic oxalate (especially in children, either as small, smooth pale stones, or in "dark, warty, 
 hard " mulberry calculi ") is not affected by acetic acid, is dissolved by mineral acids without effer- 
 vescence, and again precipitated by ammonia. Heated on platinum foil it chars and blackens, then 
 it becomes white, owing to the formation of calcic carbonate, which effervesces on the addition of an 
 acid. 
 
 (c) Calcic carbonate (chiefly in whitish-gray, earthy, chalk-like calculi, somewhat rare) dis- 
 solves with effervescence in hydrochloric acid. When burned it first becomes black, owing to 
 admixture with mucus, and then white. 
 
 (d) Ammonio-magnesic phosphate and basic calcic phosphate usually occur together in 
 soft, white, earthy stones, which occasionally are very large. These stones show that the urine has 
 been ammoniacal for a very long time. The first substance when heated gives the odor of ammo- 
 nia, which is more distinct when heated with caustic potash ; is soluble in acetic acid without effer- 
 vescence, and is again precipitated in a crystalline form from this solution on the addition of am- 
 monia. When heated it fuses into a white, enamel-like mass [hence, it is called " fusible calculus "] . 
 
GLOMERULAR EPITHELIUM. 459 
 
 Basic calcic phosphate does not effervesce with acids. The solution in hydrochloric acid is pre- 
 cipitated by ammonia. When ammonium oxalate is added to the acetic acid solution, it yields 
 calcic oxalate. 
 
 (e) Neutral calcic phosphate is rare in calculi, while it is frequent in the form of gravel. 
 Physically and chemically, these concretions resemble the earthy phosphates, only they do not con- 
 tain magnesia. 
 
 273. THE SECRETION OF URINE.— [The functions of the kidney 
 are — 
 
 1. To excrete waste products, chiefly nitrogenous bodies and salts; 
 
 2. To excrete water ; 
 
 3. And perhaps also to reabsorb water from the uriniferous tubules, after it 
 
 has washed out the waste products from the renal epithelium. 
 
 The chief parts of the organs concerned in 1, are the epithelial cells of the 
 convoluted tubules ; the glomeruli permit water and some solids to pass through 
 them, while the constrictions of the tubules may prevent the too rapid outflow of 
 water, and thus enable part of it to be reabsorbed (Brunton)i\ 
 
 Theories. — The two chief older theories regarding the secretion of urine are 
 the following : 1. According to Bowman's view (1842), through the glomeruli 
 are filtered only the water and some of the highly diffusible and soluble salts 
 present in the blood, while the specific urinary constituents are secreted by the 
 activity of the epithelium of the urinary tubules, and are extracted or removed 
 from the epithelium by the water flowing along the tubules. This has been called 
 the "vital" theory. 2. C. Ludwig (1844) assumes that very dilute urine is 
 secreted or filtered through the glomerulus. As it passes along the urinary 
 tubules it becomes more concentrated, owing to endosmosis. It gives back some 
 of its water to the blood and lymph of the kidney, thus becoming more concen- 
 trated, and assuming its normal character. [This is commonly known as the 
 " mechanical" theory.] 
 
 The secretion of urine in the kidneys does not depend upon definite physical forces 
 only. A great number of facts force us to conclude that the vital activity of certain 
 secretory cells plays a foremost part in the process of secretion (J?. Heidenhain). 
 
 The secretion of urine embraces — (1) The water, and (2) the urinary con- 
 stituents therein dissolved; both together form the urinary secretion. The 
 amount of urine depends chiefly upon the amount of water which is filtered 
 through or secreted by the glomeruli ; the amount of solids dissolved in the 
 urine determines its concentration. 
 
 (A) The amount of urine, which is secreted chiefly within the Malpighian 
 capsules, depends primarily upon the blood pressure in the area of the renal artery, 
 and follows, therefore, the laws of filtration [§ 191, II] {Ludwig and Goll). 
 [In this respect the secretion of urine differs markedly from that of saliva, gastric 
 juice, or bile. We may state it more accurately thus, that the amount of urine 
 depends very closely upon the difference of pressure between the blood in the 
 glomeruli and the pressure within the renal tubules. If the ureter be ligatured, 
 the secretion of urine is ultimately arrested, even although the blood pressure be 
 high. The secretion may also be arrested by ligature of the renal vein ; and in 
 some cases of cardiac or pulmonary disease the venous congestion thereby pro- 
 duced may bring about the same result.] 
 
 Glomerular Epithelium. — The amount of urine secreted does not depend 
 upon the hydrostatic pressure alone, but it seems that the epithelial cells covering 
 the glomerulus also participate actively in the process of secretion. Besides the 
 water, a certain amount of the salts present in the urine is excreted through the 
 glomeruli. The serum albumin of the blood, however, is prevented from passing 
 through. With regard to the secretory activity of these cells, the quantity of 
 water must also depend upon the amount and rate at which the material to be 
 secreted is carried to the glomeruli by the blood stream, and also upon the amount 
 of the urinary constituents and water present in the blood (R. Heidenhain). 
 
460 RELATION TO THE BLOOD PRESSURE. 
 
 Only when the vitality of the secretory cells is intact is there independent activity of these 
 secretory cells {Heidenhdin). When the renal artery is closed temporarily, their activity is para- 
 lyzed, so that the kidneys cease to secrete, and even after the compression is removed and the circu- 
 lation re-established, secretion does not take place for some time (Overbed). 
 
 That the secretion depends in part upon the blood pressure is proved by 
 the following considerations : — 
 
 i . Increase of the total contents of the vascular system, so as to increase the blood 
 pressure, increases the amount of water which filters through the glomeruli. The 
 injection of water into the blood vessels, or drinking copious draughts of water, 
 acts partly in this way. If the blood pressure rises above a certain height, albu- 
 min may pass into the urine. The active participation of the cells of the glom- 
 eruli is rendered probable by the fact that, after very copious drinking, the blood 
 pressure is not always raised (Pawlow) ; further, after profuse transfusion, the 
 quantity of urine is not increased. Conversely, the excretion of water, owing to 
 profuse sweating or diarrhoea, copious hemorrhage, or prolonged thirst, dimin- 
 ishes the secretion of urine. 
 
 2. Diminution of the capacity of the vascular system, provided the pressure within 
 the renal area be thereby increased, acts in a similar manner. This may be pro- 
 duced by contraction of the cutaneous vessels, owing to the action of cold, stim- 
 ulation of the vasomotor centre, or large vasomotor nerves, ligature, or com- 
 pression of large arteries (§ 85, e), or enveloping the extremities in tight bandages. 
 All these conditions cause an increase in the amount of urine, and, of course, the 
 opposite conditions bring about a diminution of urine, e. g. , the action of heat 
 on the skin causing redness and dilatation of the cutaneous vessels, weakening of 
 the vasomotor centre, or paralysis of a large number of vasomotor nerves. 
 
 3. Increased action of the heart, whereby the tension and rapidity of the blood 
 in the arteries are increased (§ 85, c), augments the amount of urine; conversely, 
 feeble action of the heart (paralysis of motor cardiac nerves, disease of the cardiac 
 musculature, certain valvular lesions), diminishes the amount. Artificial stimula- 
 tion of the vagi in animals, so as to slow the action of the heart, and thus dimin- 
 ish the mean blood pressure from 130 to 100 mm. Hg, causes a diminution in the 
 amount of urine to the extent of one-fifth (Goll, CI. Bernard) ; when the pres- 
 sure in the aorta falls to 40 mm. the secretion of urine ceases. [If the medulla 
 oblongata be divided (dog) there is an immediate fall of the general blood 
 pressure, and although, as a general rule, the secretion of urine is arrested when 
 the pressure falls to 40 to 50 mm. Hg, yet secretion has been observed to take 
 place with a lower pressure than this.] 
 
 4. The amount of urine secreted rises or falls according to the degree of fulness 
 of the renal artery (Ludwig, Max Herrmann) ; even when this artery is moderately 
 constricted in animals, there is a decided diminution in the amount of urine. 
 
 Pathological. — In fever the renal vessels are less full, and there is consecutive diminution of 
 mine [Mendelsohn), It is most important, in connection with certain renal diseases, to note that 
 ligature of the renal artery, even when it is obliterated for only two hours, causes necrosis of the 
 epithelium of the uriniferous tubules. When the arterial anaemia is kept up for a long time, the 
 whole renal tissue dies (Litten). After long-continued ligation of the renal artery, the epithelium 
 of the glomeruli becomes greatly changed (Ribbert). 
 
 5. Most diuretics act in one or other of the above-mentioned ways. 
 
 [Some diuretics act by increasing the general blood pressure (digitalis and the action of cold on 
 the skin), others may increase the blood pressure locally within the kidney, and this they may do 
 in several ways. The nitrites are said to paralyze the muscular fibres in the vasa afferentia, and 
 thus raise the blood pressure within the glomeruli. But some also act on the secretory epithelium, 
 such as urea and cafiein. Brunton recommends the combination of diuretics in appropriate cases, 
 and the diuretics must be chosen according to the end in view — as we wish to remove excess of 
 fluids from the tissues and serous cavities, or as we wish to remove injurious waste products, or 
 merely to dilute the urine.] 
 
 [6. The amount of urine also depends upon the composition of the blood. Drink- 
 
SECRETORY ACTIVITY OF THE RENAL EPITHELIUM. 461 
 
 ing a large quantity of water — whereby the blood becomes more watery — increases 
 the amount of urine, but this is true only within certain limits. It is not merely 
 the increase of volume of the blood acting mechanically which causes this increase, 
 as we know that large quantities of blood may be transfused without the general 
 blood pressure being materially raised thereby.] 
 
 [Heidenhain argues that it is not so much the pressure of the blood in the 
 glomeruli as its velocity, which determines the process of the secretion of water 
 in the kidney. He contends that, while increase of the pressure in the renal 
 artery causes an increased flow of urine, ligature of the renal vein, whereby the 
 pressure in the glomeruli is also increased, arrests the secretion altogether. In 
 both cases the pressure is increased within the glomeruli, and the two cases differ 
 essentially in the velocity of the blood current through the glomeruli.] 
 
 Pressure in the Vas Afferens. — The pressure in each vas afferens must be 
 relatively great, because (i) the double set of capillaries in the kidney offers con- 
 siderable resistance, and because (2) the lumen of the vas efferens is narrower than 
 that of the vas afferens. Hence, owing to the high blood pressure in the capilla- 
 ries of the renal glomeruli, filtration must take place from the blood into the 
 Malpighian capsules. When the vasa afferentia are dilated, e. g., through the 
 action of the nervous system on their smooth muscular fibres, the filtration pressure 
 is increased, while, when they are contracted, the secretion is lessened. When 
 the pressure becomes so diminished as to retard greatly the blood stream in the 
 renal vein, the secretion of urine begins to be arrested. Occlusion of the renal 
 vein completely suppresses the secretion (H. Meyer, v. Frerichs~). Ludwig con- 
 cluded, from this observation, that the filtration or excretion of fluid could not 
 take place through the renal capillaries proper, as, owing to occlusion of the renal 
 vein, the blood pressure in these capillaries must rise, which ought to lead to 
 increased filtration. Such an experiment points to the conclusion that the filtra- 
 tion must take place through the capillaries of the glomeruli. The venous stasis dis- 
 tends the vas efferens, which springs from the centre of the glomerulus, and 
 compresses the capillary loops against the wall of the Malpighian capsule, so that 
 filtration cannot take place through them. It is not decided whether any fluid 
 is given off through the convoluted urinary tubules. 
 
 Pressure in Ureter. — As the blood pressure in the renal artery is about 120 to 140 mm. Hg, 
 and the urine in the ureter is moved along by a very slight propelling force, so that a counter-pressure 
 of from 10 (Loiell) to 40 mm. of Hg is sufficient to arrest its flow, it is clear that the blood pressure 
 can also act as a vis a tergo to propel the urine stream through the ureter. The pressure in the 
 ureter is measured by dividing the ureter transversely and placing a manometer in it. 
 
 (B) Secretory Activity of the Renal Epithelium. — The degree of 
 concentration of the urine depends upon the quantity of the dissolved constit- 
 uents which has passed from the blood into the water of the urine. The secretory 
 cells of the convoluted tubules, by their own proper vital activity, seem to be 
 able to take up, or secrete, some, at least, of these substances from the blood 
 {Bowman, Heidenhain). The watery part of the urine, containing only easily 
 diffusible salts, as it flows along the tubules from the glomeruli, extracts or washes 
 out these substances from the secretory epithelium of the convoluted tubules. 
 
 Experiments. — 1. Sulphindigotate of soda and sodium urate, when injected 
 into the blood, pass into the urine, and are found within the protoplasm of the 
 cells of the convoluted tubules [only in those parts lined by " rodded ' ' epithelium], 
 but not in the Malpighian capsules {Heidenhain). A little later, these substances 
 are found in the lumen of the urinary tubules, from which they are washed out by 
 the watery part of the urine coming from the glomeruli. If, however, two days 
 before the injection of these substances into the blood, the cortical part of the 
 kidney containing the Malpighian capsules be cauterized [e. g., by nitrate of silver] 
 (Heidenhain), or simply be removed with a knife (Hoegyes), the blue pigment 
 remains within the convoluted tubules. It cannot be carried onward, as the water 
 
462 nussbaum's experiments. 
 
 which should carry it along has ceased to be secreted, owing to the destruction of 
 the glomeruli. This experiment also goes to show that, through the glomeruli the 
 watery part of the urine is chiefly excreted, while through the convoluted tubules the 
 specific urinary constituents are excreted. Uric acid salts, injected into the blood, 
 were observed by Heidenhain to be excreted by the convoluted tubules. Von 
 Wittich had previously observed that in birds, crystals of uric acid were excreted 
 by the epithelium of the convoluted tubules. [The presence of crystals of uric 
 acid in the renal epithelium was observed by Bowman, and used as an argument 
 to support his theory.] Nussbaum, in 1878, stated that urea is secreted by the 
 urinary tubules, and not by the glomeruli. 
 
 The same is true for the bile pigments (Mobius, 1877), for the iron salts of the vegetable acids 
 when injected subcutaneously (Glaevecke), and for haemoglobin (Landois). After the injection of 
 milk into the blood vessels, numerous fatty granules occur within the epithelium of the urinary 
 tubules (| 102). 
 
 [Nussbaum's Experiments. — In the frog and newt, the kidney is supplied 
 with blood in a different manner from that obtaining in mammals. The glomeruli 
 are supplied by branches of the renal artery. The tubules are supplied by the 
 renal-portal vein. The vein coming from the posterior extremities divides at the 
 upper end of the thigh into two branches, one of which enters the kidney, and 
 breaks up to form a capillary plexus which surrounds the uriniferous tubules, but 
 this plexus is also joined by the efferent vessels of the glomeruli. These two systems 
 are partly independent of each other. By ligaturing the renal artery, Nussbaum 
 asserted that the circulation in the glomeruli was cut off, while ligature of the 
 renal-portal vein excluded the functional activity of the tubules. By injecting a 
 substance into the blood after ligaturing either the artery or renal-portal vein, and 
 observing whether it occurs in the urine, he infers that it is given off either by the 
 glomeruli or the tubules. Sugar, peptones, and egg albumin rapidly pass through 
 an intact kidney, but if the renal artery be tied they are not excreted. Urea when 
 injected into the circulation is excreted after the artery is tied, so that it is excreted 
 through the tubules, but at the same time it takes with it a considerable quantity 
 of water. Thus water is excreted in two ways from the kidney, by the glomeruli 
 and also from the venous plexus around the tubules along with the urea. Indigo 
 carmine merely passes into the tubular epithelium of the convoluted tubules, but 
 it does not cause a secretion of urine. Albumin passes through the glomeruli, but 
 only after their membranes have been altered in some way, as by clamping the 
 renal artery for a time.] 
 
 [Adami's Experiments on the kidney of the frog clearly show that Nuss- 
 baum's conclusions are not justified, for Adami found that if the renal arteries in 
 the frog be ligatured, within a few hours a collateral circulation is established, and 
 a certain amount of blood flows through the kidney. He proved this by injecting 
 into the blood carmine or painter's vermilion, in a state of fine suspension, and 
 after ligature of the renal arteries he found it in many of the glomeruli, while laky 
 blood similarly injected revealed its presence as menisci of Hb in the Malpighian 
 capsules. Even secretion of some urine may go on after ligature of the renal 
 arteries. It is evident, then, that Nussbaum's method is not a reliable one for 
 locating the parts of the kidney through which certain substances are excreted.] 
 
 [Adami's experiments also give some support to Heidenhain's view that ttie 
 glomerular epithelium "possesses powers of a selective secretory nature;" for he 
 finds that in frogs, after ligature of the renal arteries, where, of course, the pres- 
 sure in the glomeruli is just nearly that in the veins, and in the dog after section 
 of the spinal cord, so that the blood pressure has fallen below 40 mm. Hg, whereby 
 the secretion of urine is arrested ; the injection of laky blood causes Hb to appear 
 in the capsules, although there is no simultaneous excretion of water.] 
 
 Excretion of Pigments. — Only during very copious excretion does the capsule participate. 
 After the introduction of a large amount of sodic sulphinuigotate, and when the experiment has 
 
FORMATION OF THE URINARY CONSTITUENTS. 463 
 
 lasted for a long time, the epithelium of the capsule becomes blue (Arnold and Pautynski). In 
 albuminuria the abnormal excretion of urine takes place first in the urinary tubules, and after- 
 ward in the capsules (Senator); Hb is partly found in the capsules (Grictzner, Bridges Adams). 
 According to Nussbaum, egg albumin passes out through the capsule. 
 
 2. Even when the secretion of the watery part of the urine is completely 
 arrested, either by ligature of the ureter, or after a very great fall of the blood 
 pressure in the renal artery [as after section of the cervical spinal cord], the before- 
 mentioned substances, when injected into the blood, are found in the cells of the 
 convoluted tubules. The injection of urea under these circumstances causes re- 
 newed secretion. These facts show that, independently of the filtration pressure, 
 the secretory activity of these cells is still maintained (Heidenhain, Neisser, Ustimo- 
 witsch, Grictzner). 
 
 The independent vital activity of the secretory cells of the urinary tubules, which as yet we 
 are unable to explain on purely physical grounds, renders it probable that the tubules are not to be 
 compared to an apparatus provided with physical membranes. This is proved by the following ex- 
 periment : Abeles caused arterial blood to circulate through freshly excised living kidneys. A pale, 
 urine-like fluid dropped from the ureter. On adding some urea or sugar to the blood, the secretion 
 became more concentrated. Thus the excised living kidney also excretes substances in a more con- 
 centrated form than when supplied to it in the diluted blood streaming through it. 
 
 Salts and Gases. — The vital activity explains why the serum albumin of the blood does not 
 pass into the urine, while egg albumin and dissolved haemoglobin readily do so. Among the salts 
 which occur in the blood and blood corpuscles, of course only those in solution can pass into the 
 urine. Those which are united with proteid bodies, or are fixed in the cellular elements, cannot 
 pass out, or al least only after they have been split up. Thus we may explain the difference between 
 the salts of the urine and those of the blood. Similarly, the urine can only contain the absorbed 
 and not the chemically united gases. 
 
 Ligature of the Ureter. — If the secretion be arrested, by compression or by ligature of the 
 ureter, the lymph spaces of the kidney become filled with fluid, which may pass into the blood, so 
 that the organ becomes oedematous, owing to the passage of fluid into its lymph spaces. The secre~- 
 tion undergoes a change ; as first water passes back into the blood, then the sodic chloride, sulphuric, 
 and phosphoric acids diminish, and lastly the urea (C. Ludwig, Max Herrmann). Kreatinin is 
 still present in considerable amount. There is no longer secretion of proper urine (LSbelt). 
 
 Non-Symmetrical Renal Activity. — It is remarkable that both kidneys do not secrete sym- 
 metrically — there is an alternate condition of hyperemia and secretory activity on opposite sides 
 (# ioo). One kidney secretes a more watery urine, which at the same time contains more NaCl 
 and urea (Ludwig, M. Herrmann). Von Wittich observed that the excretion of uric acid was not 
 uniform in all the urinary tubules of the same bird. Extirpation of one kidney, or disease of one 
 kidney in man, does not seem to diminish the secretion (Rosenstein). The remaining kidney 
 becomes more active and larger. 
 
 Reabsorption in the Kidney. — In discussing the secretion of the kidney, we must attach con- 
 siderable importance to the variations in the calibre of the renal tubules in their course. Perhaps 
 in the narrowing of the descending part of the looped tubule of Henle there may be either a reab- 
 sorption of water, so that the urine becomes more concentrated, or there may be absorption even of 
 albumin, which may, perphaps, pass through the glomeruli in small amount. [That reabsorption 
 of fluid takes place within the kidney was part of Ludwig's theory, which is practically a process of 
 filtration and reabsorption. Hufner pointed out that the structure of the kidneys of various classes 
 of vertebrates corresponded closely with the requirements for reabsorption of water. The experi- 
 ments of Ribbert show that the urine actually secreted in the cortex of the kidney is more watery 
 than that secreted normally by the entire organ. He extirpated the medullary portion in rabbits, 
 leaving the cortical part intact, and in this way collected the dilute urine from the Malpighian cor- 
 puscles before it passed through Henle's loops.] 
 
 274. FORMATION OF THE URINARY CONSTITUENTS.— 
 
 The question has often been discussed, whether all the urinary constituents are 
 merely excreted through the kidneys, i, e., that they exist pre-formed in the 
 blood ; or whether some of them do not exist pre-formed in the blood, but are 
 formed within the kidneys, as a result of the activity of the renal epithelium. 
 
 Seat of Urea Formation. Urea formed outside the Kidney. — In 
 considering the formation of urea, we have to ascertain if it is formed within the 
 kidney or outside of it. Urea exists pre-formed in the blood, from which it is 
 separated by the activity of the kidney. This is proved by the following con- 
 siderations : — 
 
464 FORMATION OF URIC ACID. 
 
 1. The blood contains one part of urea in 3000 to 5000 parts {Fr. Simon, 1S41), but the renal 
 vein contains less urea than the blood of the corresponding artery {Picara, 1836; Grihant). 
 This fact is in favor of the excretion of urea from the blood. 
 
 2. After extirpation of the kidneys, or nephrotomy {Privost and Dumas), or after ligature of 
 the renal vessels, the amount of urea accumulates in the blood {Meissner, v. Voit), and increases 
 with the duration of the experiment to -A-Q to ^y {Grihant). At the same time there is vomiting 
 and diarrhcea, and the fluids so voided contain urea {CI. Bernard, Bareswill). Animals die in 
 from one to three days after the operation. 
 
 3. After ligature of the ureters, the secretion of urine is soon arrested. Urea accumulates in the 
 blood, but not to a greater extent than after nephrotomy. It is possible, however, that the kidneys, 
 like other organs, may form a small amount of urea, due to the metabolism of their own tissues. 
 
 [Urea exists in the blood ; whence does the blood derive it ? It can only obtain it from one 
 or more of several organs — (1) muscle; (2) nervous system; and (3) glands, of which the liver is 
 the most prominent. This is best stated by the method of exclusion.] 
 
 [1. That urea is not formed in muscle is shown, among other considerations, by the fact that only 
 a trace of urea occurs in muscle (J 293), and that amount is not increased by exercise. Blood 
 which has been transfused through a muscle, or the blood after circulating in a muscle during violent 
 exercise, does not contain an increase of urea, nor does the addition of ammonia carbonate to blood 
 circulating through muscle show any increase of urea {Grihant, Quinquand, Salomon). Again, 
 muscular exertion does not (as a rule) increase the amount of urea in the urine, as shown by the 
 experiments of Fick and Wislicenus {\ 294), Parkes, and others. The excretion chiefly increased 
 by muscular exertion is pulmonary C0 2 (| 127).] 
 
 [2. From what we know of the nervous system, it is not formed there. We are therefore forced 
 to consider the evidence as to the liver as the organ, or, at least, the chief organ in which it is 
 formed. This evidence is in some respects contradictory, but it is partly experimental and partly 
 clinical. Although Hoppe-Seyler denies the existence of urea in the liver, its existence there is 
 proved by Gscheidlen; and Cyon, on passing blood through an excised liver by the "perfusion" 
 or '* Durchstromung " method of Ludwig, found that blood, after being passed several times through 
 the organ, contained an increased amount of urea. The objection to these experiments is, that 
 Cyon's method of estimating the urea was unreliable. But von Schrceder, using a similar method, 
 finds that if blood be perfused though the liver of a dog in full digestion, there is a great increase in 
 the amount of urea, while there is none in the liver of a fasting dog. If ammonia carbonate be 
 added to the blood, there is a very much greater amount of urea in the blood of the hepatic vein. 
 This last fact is confirmed by Salomon. The experiments of Minkowski on the liver of the goose 
 (fj 386) show that when the liver is excluded from the circulation, lactic acid takes the place of uric 
 acid in this bird. Brouardel further states, that if the region of the liver be so beaten as to cause 
 congestion of that organ, there is an increase of the urea in the urine.] 
 
 [The clinical evidence points strongly to the formation of urea in the liver. Parkes pointed out 
 that in hepatic abscess, during the early congestive stage, the urea in the urine is increased, while it 
 is diminished in the suppurative stage, when the hepatic parenchyma is destroyed. The urea is also 
 diminished in cancer of the liver, phthisis, and some forms of hepatic cirrhosis, while it is increased 
 during hepatic congestion, and specially so in some cases of diabetes mellitus. The most striking 
 fact of all is that, in acute yellow atrophy of the liver, the urea is enormously diminished in the 
 urine, and may even disappear from it, while its place is taken by the intermediate products, leucin 
 and tyrosin {v. Frerichs). In poisoning by phosphorus, coincident with the atrophy of the liver, 
 there is a fall in the urea excretion. Noel-Paton finds that some drugs which increase the quantity 
 of bile in dogs in a state of N equilibrium (\ 178), sodic salicylate and benzoate, colchicum, mercuric 
 chloride and euonymin also increase the urea in the urine ; he therefore concludes " that the forma- 
 tion of urea in the liver bears a very direct relationship to the secretion of bile by that organ."] 
 
 As to the antecedents of urea there is the greatest doubt (§ 256). 
 
 Seat of Uric Acid Formation. Uric acid formed outside the kidneys. 
 
 I. Birds' blood normally contains uric acid {Meissner). . Ligature of their ureters or blood vessels 
 {Paivlinoff), or the gradual destruction of their secretory parenchyma by the subcutaneous injection 
 of neutral potassium chromate {Ebstein), is followed by the deposition of uric acid in the joints and 
 tissues, and it may even form a white incrustation on the serous membranes. The brain remains free 
 {Galvani, 1767; Zalesky, Oppler). Acid urates of ammonia, soda, and magnesia are also similarly 
 deposited ( Colasanti). Extirpation of a snake's kidneys gives the same result, but to a less degree. 
 
 [2. Minkowski found that, after excluding the liver from the circulation, lactic acid took the place 
 of uric acid in the urine (p. 298).] * 
 
 [The latter experiments point to the formation of uric acid in the liver in birds, 
 and this is supposed to be strengthened by the appearance of the deposition of 
 urates in the urine in certain disorders of digestion.] Von Schrceder and Cola- 
 santi, however, as the result of their experiments upon snakes, come to the con- 
 clusion that there is no special organ concerned in the formation of uric acid. 
 
PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE. 
 
 Hippuric acid is partly formed in the kidney, for the blood of herbivora does not contain a 
 trace of it (Meissner and Shepard). In rabbits, perhaps it is formed synthetically, in other tissues 
 as well as in the kidney. If blood containing sodic benzoate and glycin be passed through the 
 blood vessels of a fresh kidney, hippuric acid is formed (§ 260) (Bunge, Schmiedeberg, Kochs). 
 [The other evidence is given in \ 260.] Kreatinin has intimate relations to kreatin of muscle, but 
 where it is formed is not known. If phenol and pyrokatechin are digested along with fresh renal 
 substance, a compound of sulphuric acid similar to that occurring in urine ({} 262) is formed. The 
 latter substance, however, is also formed by similarly digesting liver, pancreas, and muscle. It is 
 concluded from these experiments that these substances are formed in the body within the kidneys, 
 and the other organs mentioned (Kochs). 
 
 Chemistry of the Kidney. — The kidneys contain a very large amount of water. Besides serum 
 albumin, globulin, albumin soluble in sodium carbonate (Gottwalt), gelatin-yielding substances, fat 
 in the epithelium, elastic substance derived from the membrana propria of the tubules, the kidneys 
 contain leucin, xanthin, hypoxanthin, kreatin, taurin, inosit, cystin (the last in no other tissue), but 
 only in very small amount. The occurrence of these substances points to a lively metabolism in 
 the kidneys, which is also proved by the liberal supply of blood they receive. 
 
 Blood Vessels. — The kidneys receive a very large supply of blood, and dur- 
 ing secretion of the blood of the renal vein is bright red (C/. Bernard '). [In 
 the dog the diameter of the renal artery may be diminished to .5 mm. without the 
 amount of blood flowing through the kidney being thereby greatly interfered with. 
 Hence, within wide limits, the amount of blood is independent of the size of the 
 arterial lumen, and is, therefore, dependent on the blood pressure in the aorta, 
 and the resistance to the blood current within and beyond the kidney (Jffeiden- 
 hairi).~\ 
 
 The reaction of the kidney is acid, even in those animals whose urine is alkaline. Perhaps this 
 fact is connected with the retention of the albumin in the vessels (Heynsius). 
 
 275. PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE.— 1. The fol- 
 lowing substances pass unchanged into the urine : Sulphate, borate, silicate, nitrate, and carbon- 
 ate of the alkalies ; alkaline chlorides, bromides, iodides ; potassium sulphocyanide and ferrocyanide ; 
 bile salts, urea, kreatinin ; cumaric, oxalic, camphoric, pyrogallic, and carbolic acids. Many alka- 
 loids, e.g., morphia, strychnia, curara, quinine, caffein; pigments, sulphindigotate of soda, carmine, 
 madder, logwood, coloring matter of cranberries, cherries, rhubarb ; santonin ; lastly, salts of gold, 
 silver, mercury, antimony, arsenic, bismuth, iron (but not lead), although the greatest part of these 
 is excreted by the bile and the feces. 
 
 2. Inorganic acids reappear in man and carnivora as neutral salts of ammonia (Sckmeideberg and j 
 Walter, Uallervorden) ; in herbivora, as neutral salts of the alkalies (E. Salkowski). 
 
 3. Certain substances which, when injected in small amount, seem to be decomposed in the 
 blood, pass in part into the urine, when they occur in such large amount fn the blood that they can- 
 not be completely decomposed — sugar, haemoglobin, egg albumin, alkaline salts of the vegetable 
 acids, alcohol, chloroform. 
 
 4. Many substances appear in an oxidized form in the urine — moderate quantities of vegetable 
 alkaline salts as alkaline carbonates ( Wohler), uric acid in part as allantoin (Salkowski), sulphides 
 and sulphites of soda, in part as sodium sulphate, potassium sulphide as potassium sulphate, some 
 oxydulsas oxides, benzol as phenol (Naumyn and Sckulzen). 
 
 5. Those bodies which are completely decomposed, as glycerin, resins, give rise to no special 
 derivatives in the urine. 
 
 6. Many substances combine and appear as conjugated compounds in the urine, e.g., the origin 
 of hippuric acid by conjugation (§ 260), the conjugation of sulphuric acid (§ 262), and the forma- 
 tion of urea by synthesis from carbamic acid and ammonia (Drecksel) (g 256). After the use of 
 camphor, chloral, or butylchloral, a conjugated compound with glycuronic acid (an acid nearly 
 related to sugar) appears in the urine. Taurin and sarcosin unite with sulphaminic acid. When 
 bromphenol is given, it unites with mercapturic acid, a body nearly related to cystin ((! 268). 
 
 7. Tannic acid, C I4 Hi O 9 , takes up H 2 0, and is decomposed into two molecules of gallic acid 
 = 2(C r H 6 5 ). 
 
 8. The iodates of potash and soda are reduced to iodides ; malic acid (C 4 H 6 6 ) partly to suc- 
 cinic acid (C 4 H 6 4 ) ; indigo blue (C 16 H 10 N 2 O 2 ) takes up hydrogen and becomes indigo white 
 (C 18 H 12 N 2 2 ). 
 
 9. Some substances do not pass into the urine at all, e. g., oils, insoluble metallic salts and 
 metals. 
 
 276. INFLUENCE OF NERVES ON THE RENAL SECRE- 
 TION. — At the present time we are acquainted merely with the influence of the 
 vasomotor nerves on the filtration of the urine through the renal vessels. Each 
 
 3° 
 
466 INFLUENCE OF NERVES ON THE RENAL SECTION. 
 
 kidney seems to be supplied with vasomotor nerves, which spring from both halves 
 of the spinal cord (Nicolaides). As a general rule, dilatation of the branches of 
 the renal artery, chiefly the vasa afferentia, must raise the pressure within the glom- 
 eruli, and thus increase the amount of water filtered through them. The more the 
 dilatation is confined to the area of the renal artery alone, the greater is the 
 amount of the urine. [As yet we only know that the nervous system influences 
 the secretion of urine only in so far as it modifies the pressure and velocity of the 
 blood current in the kidney. We have no satisfactory evidence of the existence 
 of direct secretory nerves in the kidney.] 
 
 i. Renal Plexus and its Centre. — Section of the nerves of the renal plexus 
 — the nerves around the renal artery — generally causes an increase in the secretion 
 of urine [hydruria or polyuria] ; sometimes, on account of the great rise of the 
 pressure within the glomeruli, albumin passes into the urine (and there may be 
 rupture of the vessels of the glomeruli), leading to the passage of blood into the 
 urine. The nerve centre for these renal nerves lies in the floor of the fourth 
 ventricle, in front of the origin of the vagus. Injury to this part of the floor of 
 the fourth ventricle, e. g., by puncture (piqure), may increase the amoimt of 
 urine (diabetes insipidus), which is sometimes accompanied by the simulta- 
 neous appearance of albumin and blood in the urine {CI. Bernard). Section of 
 the parts which lie directly in the course of these fibres, as they pass from the 
 centre in the medulla to the kidney, produces the same effects. Close to this 
 centre in the medulla, there lies the centre for the vasomotor nerves of the liver, 
 whose injury causes diabetes mellitus (§ 175): Eckhard found that stimulation 
 of the vermiform process of the cerebellum produced hydruria. In man, stimula- 
 tion of these parts by tumors or inflammation, etc., produces similar results. 
 
 2. Paralysis of Limited Vascular Areas. — If, simultaneously with the 
 paralysis of the nerves of the renal artery, the nerves of a neighboring large vas- 
 cular area be paralyzed, necessarily the blood pressure in the renal artery area 
 will not be so high, as more blood flows into the other paralyzed province. 
 Under these circumstances, there may be only a temporary, or, indeed, no increase 
 of urine, provided the paralyzed area be sufficiently large. There is a moderate 
 increase of urine for several hours after section of the splanchnic nerve. This 
 nerve contains the renal vasomotor nerves (which, in part, at least, leave the spinal 
 cord at the first dorsal nerve and pass into the sympathetic nerve), but it also con- 
 tains the vasomotor nerves for the large area of the intestinal and abdominal 
 viscera. Stimulation of this nerve has the opposite effect ( CI. Bernard, Eckhard'). 
 [The polyuria thus produced is not so great as after section of the renal nerves, 
 because the splanchnic supplies such a large vascular area, that much blood accu- 
 mulates in that area, and also because all the renal nerves do not run in the 
 splanchnics.] 
 
 3. Paralysis of Large Areas. — If, simultaneously with paralysis of the 
 renal nerves, the great majority of the vasomotor nerves of the body be paralyzed 
 [as by section of the medulla oblongata], then, owing to the great dilatation of 
 all these vessels, the blood pressure falls at once throughout the entire arterial 
 system. The result of this may be, provided the pressure is sufficiently low, that 
 there is a great decrease, or, it may be, entire cessation of the secretion of urine. 
 The secretion is arrested when the cervical cord is completely divided, down even 
 as far as the seventh cervical vertebra {Eckhard). The polyuria caused by injury 
 to the floor of the fourth ventricle at once disappears when the spinal cord (even 
 down to the twelfth dorsal nerve) is divided. 
 
 [As already stated, section of the renal nerves is followed by polyuria, owing to the 
 increased pressure in the glomeruli, but this polyuria may be increased by stimu- 
 lating the spinal cord below the medulla oblongata, because the contraction of the 
 blood vessels throughout the body still further raises the blood pressure within the 
 glomeruli. If, however, the spinal cord be divided below the medulla oblongata 
 — the renal nerve being also divided — the polyuria ceases, because of the fall of 
 
RENAL ONCOGRAPH AND ONCOMETER. 
 
 467 
 
 the general blood pressure thereby produced. Merely dividing the spinal cord in 
 the dorsal region also diminishes or arrests the secretion of urine, owing to the 
 fall of the blood pressure, but animals recover from this operation, the general 
 blood pressure rises, and with it the secretion of urine. Stimulation of the cord 
 below the medulla arrests the secretion, as it causes contraction of the renal 
 arteries along with the other arteries of the body.] 
 
 [Volume of the Kidney — Oncometer.— By means of the plethysmograph 
 (§ 101) we can measure the variations in the size of a limb, while by the oncograph 
 (dj-zu?, volume) similar variations in the volume of the spleen are measured (§ 103). 
 Roy and Cohnheim have measured the variations in the volume of the kidney by 
 means of an instrument which consists of two parts, one termed the oncometer 
 or renal plethysmometer, in which the organ is enclosed, while the other part is 
 the registering portion or oncograph. The kidney is enclosed in a metallic 
 capsule shaped like the kidney (Fig. 265), and it is composed of two halves which 
 move on a hinge, h, to introduce the organ. The renal vessels pass out at a, v. 
 The kidney is surrounded with a thin membrane, and between this membrane and 
 the inner surface of the capsule is a space filled with warm oil through the tube, 
 I, which is closed by means of a stopcock after the space is filled with oil. The 
 tube, T, can be made to communicate with another tube, T„ leading into a 
 
 Fig. 266. 
 
 Oncometer. K, kidney ; the thick line is the metal- Oncograph. C, chamber filled with oil, communicating by Tj 
 lie capsule ; h, hinge ; I, tube for filling appa- with T ; p, piston ; /, writing lever {Stirling, after Roy). 
 
 ratus ; T, tube to connect with Tj ; a, v, », 
 artery, vein, ureter (Stirling; after Roy). 
 
 metallic chamber, C 1 , of the oncograph (Tig- 266), which is provided with a 
 movable piston, /, attached by a thread to the writing lever, /. Any increase in 
 the size of the organ expels oil from the chamber, O, into C 1 , and thus the piston 
 is raised, while a diminution in the size of the kidney diminishes the fluid in C 1 
 and the lever falls. The actual volume of the living kidney depends upon the 
 state of distention of its structural elements, upon the amount of lymph in its lymph 
 spaces, but chiefly upon the amount of blood in its blood vessels, and this again 
 must depend upon the condition of the non-striped muscles in the renal arteries. 
 When the vessels dilate, the kidney will increase in size, and when they contract 
 it contracts, so that we can register on the same revolving cylinder the variations 
 of the volume at the same time that we record the general arterial blood pressure.] 
 [In the normal circulation through the kidney, the kidney curve, i. e., the 
 curve of the volume of the kidney, runs quite parallel with the blood-pressure 
 curve, and shows exactly the large respiratory undulations, as well as the smaller 
 elevations due to the systole of the heart (Fig. 267). Usually, when the blood 
 pressure falls, the kidney curve sinks, and when the blood pressure rises, the volume 
 of the kidney increases. When the blood-pressure curve is complicated by Traube- 
 Hering waves (§ 85), the opposite effect is produced on the kidney curve ; the 
 
468 CONDITIONS AFFECTING THE VOLUME OF THE KIDNEY. 
 
 highest blood pressure corresponds to the smallest size of the kidney, and con- 
 versely. This is due to the fact that, when these curves occur, all the small arte- 
 rioles — including those in the kidney — are contracted. A kidney placed in an 
 oncometer secretes urine like a kidney under natural conditions.] 
 
 [Arrest of the respiration in a curarized animal produces a rapid and great 
 diminution of the volume of the kidney, caused by the venous blood stimulating 
 the vasomotor centres, and thus contracting the small arterioles, including those 
 of the kidney. This result occurs whether one or both splanchnics are divided, 
 proving that all the vasomotor nerves of the kidney do not reach it through the 
 splanchnics. When all the renal nerves at the hilum are divided, arrest of the 
 respiration causes dilatation of the organ, which condition runs parallel with the 
 rise of the blood pressure. Stimulation of a sensory nerve, e. g., the central end 
 of the sciatic nerve, while causing an increase of the blood pressure, makes the 
 kidney shrink.] 
 
 [In poisoning with strychnin, the kidney shrinks while the blood pressure 
 rises. Stimulation of the central or peripheral end of the splanchnics, divided 
 at the diaphragm, causes contraction of the renal vessels of both sides ; the former 
 is a reflex, the latter a direct effect. Stimulation of the peripheral end of one 
 splanchnic sometimes affects both kidneys. Stimulation of the peripheral end of 
 the renal nerves always causes a diminution in the volume of the kidney, so that 
 
 Fig. 267. 
 
 B P, blood-pressure curve ; K, curve of the volume of the kidney ; T, time curve, intervals indicate a quarter of a 
 minute; A, abscissa {Stirling, after Roy). 
 
 Cohnheim and Roy were forced to conclude that, although there was evidence ot 
 the existence of vasomotor and sensory nerves to the kidney, they found 
 none of the vaso-dilator nerves. By the same method, Cohnheim and Roy con- 
 firmed absolutely the independent action of the two kidneys. The sudden com- 
 pression of one renal artery had not the slightest effect upon the blood current 
 of the other kidney. If a kidney be exposed in an animal, by making an incision 
 in the lumbar region, on stimulating the medulla oblongata directly with elec- 
 tricity, we may observe the kidney itself becoming paler, the pallor appearing in 
 a great many small spots on the surface of the organ, corresponding to the distri- 
 bution of the interlobular arteries ] 
 
 [The researches of Cohnheim have shown that the composition of the blood 
 has a remarkable effect on the renal circulation. Some substances (water and 
 urea), when injected into the blood, cause the kidney first to shrink and then to 
 expand, while sodic acetate dilates the kidney, even after all the renal nerves are 
 divided — an operation which is very difficult indeed. Provided all the renal 
 nerves be divided, these effects would indicate the existence of some local intra- 
 renal vasomotor mechanism governing the renal blood vessels. The general 
 blood pressure is not thereby modified j nor need we wonder at this, as ligature 
 of one renal artery does not increase the pressure in the aorta.] 
 
 [Mosso also showed that the blood stream through an excised organ was mate- 
 
UREMIA AND AMMONLEMIA. 469 
 
 rially influenced by the substances mixed with the blood perfused. This effect 
 may, in part, be due to the action of these chemical ingredients upon the nuclei 
 of the endothelial lining of the blood vessels, especially the capillaries.] 
 
 [The reciprocal relation between the skin and the kidneys is known to 
 every one. On a cold day, when the skin is pallid, owing to contraction of the 
 cutaneous vessels, the amount of urine secreted is great, and, conversely, in 
 summer less urine is passed than in winter. Washing the skin of a dog for two 
 minutes with ice-cold water causes a great contraction of the kidney.] 
 
 [Strychnin seems to be able to cause contraction of the renal vessels, independently of its action 
 on the general vasomotor centre. Brunton and Power found that digitalis caused an increase of the 
 blood pressure (dog), but the secretion of urine was either at the same time diminished, or it ceased 
 altogether. The latter result was due to contraction of the renal blood vessels ; but when the aortic 
 blood pressure began to fall, the amount of urine secreted rose much above normal, i. e., when the 
 arteries had begun to relax.] 
 
 During fever the renal vessels are probably contracted in consequence of the stimulation of the 
 renal centre by the abnormally warm blood (Mendelsohn). 
 
 The repeated respiration of CO is said to produce polyuria, perhaps in consequence of paralysis 
 of the renal vasomotor centre. 
 
 Action of the Vagus. — According to CI. Bernard, stimulation of the vagus at the cardia in- 
 creases the urinary secretion, while at the same time the blood of the renal vein becomes red. It 
 is possible that this nerve may contain vaso-dilator nerve fibres corresponding to the fibres in the 
 facial nerve for the salivary glands ($ 145). 
 
 277. UREMIA — AMMONI^EMIA. — Symptoms of Uraemia. — After excision of the kid- 
 neys (nephrotomy), or ligature of the ureter, whereby the secretion of urine is arrested; in man, 
 also, as a result of certain diseased conditions of the kidney, leading to the suppression of the 
 secretion of urine, there is developed a series of characteristic symptoms which are followed by 
 death. The condition is called ursemic intoxication or urcemia. Besides marked brain phenomena, 
 drowsiness, and even deep coma, there are occasional local or more general spasms. Sometimes 
 there is delirium; Cheyne-Stokes phenomenon is often observed (\ in, II), and there may be 
 vomiting and diarrhoea, while in the fluids voided, as well as in the expired air, ammonia may some- 
 times be detected. 
 
 The cause of these phenomena has been ascribed to the retention in the blood of those sub- 
 stances which normally are excreted by the urine, but as yet it has not been definitely ascertained 
 which of these substances causes the phenomena : — 
 
 1. The first thought is to ascribe them to the retention of the urea. v. Voit found that dogs ex- 
 hibited ursemic symptoms if they were fed for a long time on food containing urea and little water. 
 Meissner found that in nephrotomized animals, the urcemic symptoms were hastened by the injection 
 of urea into the blood. The injection of a moderate amount of urea in perfectly sound animals is 
 not followed by ursemic symptoms, probably because the urea is rapidly excreted by the kidneys ; 
 I to 2 grms. [15 to 30 grains] so injected produce comatose symptoms in rabbits. 
 
 2. The injection of ammonium carbonate produces symptoms resembling those of uraemia, so 
 that v. Frerichs and Stannius thought that the urea was decomposed in the blood, yielding ammo- 
 nium carbonate — ammoniaemia. Demjankow observed uremic phenomena after nephrotomy, 
 when at the same time he injected the urea ferment into the blood ($ 263). Feltz and Ritter ob- 
 tained uraemic symptoms in dogs by injecting salts of ammonia. 
 
 3. As ligature of the ureters produces a comatose condition in those animals which excrete chiefly 
 uric acid in the urine — e. g , birds and snakes I Zalesky) — it is possible that other substances may 
 produce the poisonous symptoms. The injection of kreatin causes feebleness and contraction of the 
 muscles in dogs (Meissner). . Bernard, Traube, and more recently Feltz and Ritter, ascribe the 
 symptoms to an accumulation of the neutral potassium salts in the blood ({! 54). The injection of 
 kreatin, succinic acid (Meissner), uric acid, and sodic urate (Ranke) is without effect. Schottin 
 and Oppler ascribe the results to an accumulation of normal or abnormal extractives. It is pos- 
 sible that several substances and their decomposition products (v. Voit ', Perls) contribute to produce 
 the result, so that there is a combined action of several factors, but perhaps the retention of the 
 potash salts plays the most important part. 
 
 [Alkaloids in Urine (Pouchet,i88o). — Human urine, and especially febrile urine, when injected 
 under the skin of frogs or rabbits, acts as a poison, and even causes death, by the arrest of the res- 
 piration (CI. Bernard, Bocci, Bouchard). The alkaloids seem to be formed by the action of vege- 
 table organisms in the intestine, whence they are absorbed into the blood and pass into the urine 
 (\ 116). Urine rendered colorless by charcoal loses half its toxic power, and the poisonous sub- 
 stance is not volatile, and even resists boiling. These alkaloids are increased in the urine in 
 typhoid fever, pneumonia, but not in diabetes (Lipine and Guerin).'] 
 
 Ammoniaemia. — When urine undergoes the alkaline fermentation within the bladder, and am- 
 monium carbonate is formed, the ammonia may be absorbed and produce this condition. The 
 
470 STRUCTURE AND FUNCTIONS OF THE URETER. 
 
 breath and excretions smell strongly of ammonia ; the mouth, pharynx, and skin are very dry ; 
 there is vomiting, with diarrhoea or constipation, while ulcers may form in the intestine (Treitz). 
 The patient rapidly loses flesh, and death occurs without any disturbance of the mental faculties. 
 
 Uric Acid Diathesis. — When too much nitrogenous food, too much alcoholic fluids are persist- 
 ently used, and little muscular exercise taken, especially if the respiratory organs are interfered 
 with, uric acid may not unfrequently accumulate in the blood ( Garrod). It may be deposited in 
 the joints and their ligaments, especia'ly in the foot and hand, giving rise to painful inflammation, 
 and forming gout stones or chalk stones. The heart, liver, and kidneys are rarely affected. The 
 tissues near these deposits undergo necrosis. 
 
 278. STRUCTURE AND FUNCTIONS OF THE URETER.— Mucous Membrane. 
 — The pelvis of the kidney and the ureter are lined by a mucous membrane, consisting of connect- 
 ive tissue, and covered with several layers of stratified "transitional" epithelium (Fig. 268). 
 The cells are of various shapes, those of the lowest layer being usually more or less spherical and 
 small, while many of the cells in the upper layers are irregular in shape, often with long processes 
 passing into the deeper layers. 
 
 Submucosa. — Under the epithelium there is a layer of adenoid tissue {Hamburger, Chiari), 
 which may contain small lymph follicles [embedded in loose connective tissue]. There are a few 
 small mucous glands in the pelvis of the kidney, and also in the ureter {Unruh, Egli). [They are 
 lined by a single layer of columnar epithelium.] 
 
 The muscular coat consists of an inner somewhat stronger layer of longitudinal, non-striped 
 fibres, and an outer circular layer. In the lowest third of the ureter there are in addition a num- 
 ber of scattered muscular fibres. All these layers are surrounded and supported by connective 
 tissue. The outer layers of the connective tissue form an outer coat or adventitia, which contains 
 the large vessels and nerves [with small ganglia]. The various coats of the ureter can be followed 
 up to the pelvis of the kidney, and to its calices. The papillae are covered only by the mucous 
 membrane, while the muscular layer ceases at the apex of the pyramids, where they are disposed 
 circularly to form a kind of sphincter muscle for each papilla {Henle). 
 
 The blood vessels supply the various coats, and form a capillary plexus under the epithelium. 
 
 The nerves are not very numerous, but they contain medullated (few) and non-medullated fibres, 
 with numerous ganglia scattered in their course. They are partly motor and supply the muscular 
 layers, and some pass toward the epithelium, and are sensory and excito-reflex in function. It is 
 these nerves which are excited when a calculus, passing along the ureter, gives rise to severe pain. 
 The ureter perforates the wall of the bladder obliquely. The inner opening is a narrow slit in the 
 mucous membrane, directed downward and inward, and provided with a pointed, valve- like pro- 
 cess (Fig. 269). 
 
 Movement of the Urine. — The urine is propelled along the ureter thus : 
 (1) The secretion, which is continually being formed under a high pressure in the 
 kidney, propels onward the urine in front of it, as the urine is under a low pressure 
 in the ureter. (2) Gravity aids the passage of the urine when the person is in 
 the erect posture. (3) The muscles of the ureter contract rhythmically and peri- 
 staltically, and so propel it toward the bladder. This movement is reflex, and 
 is due to the presence of the urine in the ureter. Every three-quarters of a min- 
 ute several drops of urine pass into the bladder {Mulder). But the fibres may also 
 be excited directly. The contraction passes along the tube at the rate of 20 to 30 
 mm. per second, always from above downward. The greater the tension of the 
 ureter due to the urine, the more rapid is the peristaltic movement {Sokoleff and 
 Luchsinger). 
 
 Local Stimulation. — On applying a stimulus to the ureter directly, the contraction passes both 
 upward and downward. Engelmann observed 1 that these movements occur in parts of the ureter 
 where neither nerves nor ganglia were to be found, and he concluded that the movement was 
 propagated by " muscular conduction." If this be so, then an impulse may be propagated from 
 one non-striped muscular cell to another without the intervention of nerves (compare the same 
 result in the heart, § 58, I, 3). * 
 
 Prevention of Reflux. — The urine is prevented from exerting a backward 
 pressure toward the kidneys, thus: 1. The urine which collects in the pelvis of 
 the kidney is under a high pressure, and thus tends uniformly to compress the 
 pyramids, so that the urine cannot pass into the minute orifices of the urinary 
 tubules (E. H. Weber). 2. When there is a considerable accumulation of urine 
 in a ureter, e. g. , from the presence of an impacted calculus or other cause, 
 there is also more energetic peristalsis, and, at the same time, the circular mus- 
 cular fibres round the apices of the pyramids compress the pyramids and prevent 
 
URINARY BLADDER AND URETHRA. 
 
 471 
 
 the reflux of urine through the collecting tubules. The urine is prevented from 
 passing back from the bladder into the ureter, by the fact that, when the bladder 
 is greatly distended with urine, the wall of the bladder itself, and the part of the 
 ureter which passes through it, are compressed, so that the edges of the slit-like 
 opening of the ureter are rendered more tense, and are thus approximated toward 
 each other (Fig. 269). 
 
 279. URINARY BLADDER AND URETHRA.— Structure.— The mucous mem- 
 brane of the bladder resembles that of the ureter ; the upper layers of the stratified transitional 
 epithelium are flattened. It is obvious that the form of the cells must vary with the state of dis- 
 tention or contraction of the bladder. [The mucous membrane and muscular coats are thicker 
 than in the ureter. There are mucous glands in the mucous membrane, especially near the neck 
 of the bladder.] 
 
 Submucous Coat. — There is a layer of delicate fibrillar connective tissue mixed with elastic 
 fibres between the mucous and muscular layers. 
 
 [The Serous Coat is continuous with, and has the same structure as, the peritoneum, and it 
 covers only the posterior and upper half of the organ.] 
 
 Musculature. — The non-striped muscular fibres are arrange J in bundles in several layers, an 
 
 Fig. 269. 
 
 Transitional epithelium from the bladder. Many 
 of the large cells lie upon the summit of the 
 columnar and caudate cells, and depressions 
 are seen on their under surface. 
 
 Lower part of the human bladder laid open, with the lower ends of the 
 ureters. Note the clear part, the trigone, the slit-like openings of the 
 ureters, the divided ureters, and vesiculae seminales; the sinus prostati- 
 cus, and on each side of it the round openings of the ejaculatory ducts, 
 and b low both the numerous small apertures of the ducts of the pros- 
 tate gland. 
 
 external longitudinal layer, best developed on the anterior and posterior surfaces, and an inner 
 circular layer. [Between these two is an oblique layer.] There are other bundles of muscular 
 fibres arranged in different directions. Physiologically, the musculature of the bladder represents 
 a single or common hollow muscle, whose function when it contracts is to diminish uniformly the 
 size of the bladder, and thus to expel it« contents (jg 306). 
 
 The blood vessels resemble those of the ureter. The nerves form a plexus, and are placed 
 partly in the mucous membrane and partly in the muscular coat, and, like all the extra renal parts 
 of the urinary apparatus, are provided with ganglia, some of these lying in the mucosa, others in 
 the submucosa, and connected to each other by fibres (Maier). Ganglia occur in the course of 
 the motor nerve fibres in the bladder ( W. Wolff). Their functions are motor, sensory, excitomotor 
 and vasomotor. [Sympathetic nerve ganglia also exist underneath the serous coat (F. Darwin)."] 
 
 A too minute dissection of the several layers and bundles of the musculature of the bladder has 
 given rise to erroneous inferences. Thus, we speak of a special detrusor urinse, which, how- 
 ever, consists chiefly of fibres running on the anterior and posterior surfaces, from the vertex to the 
 fundus. There does not seem to be a special sphincter vesicae internus ; it is merely a thicker 
 circular (6 to 12 mm.) layer of non-striped muscle which surrounds the beginning of the urethra, 
 and which, from its shape, helps to form the funnel-like exit of the bladder. Numerous muscular 
 bundles, connected partly with the longitudinal and partly with the circular fibres of the bladder 
 exist, especially in the trigone, between the orifices of the ureters. 
 
472 ACCUMULATION OF URINE — MICTURITION. 
 
 Sphincter Urethra. — The proper sphincter urethrse is a transversely striped 
 muscle subject to the will, and consists of completely circular fibres which extend 
 downward as far as the middle of the urethra, and partly of longitudinal fibres, 
 which extend only on the posterior surface toward the base of the bladder, where 
 they become lost between the fibres of the circular layer (Ifenle). 
 
 In the male urethra, the epithelium of the prostatic part is the same as that in the bladder ; in 
 the membranous portion it is stratified, and in the cavernous part the simple cylindrical form. The 
 mucous membrane, under the epithelium itself, is beset with papilla, chiefly in the posterior part of 
 the urethra, and contains the mucous glands of Littre. 
 
 Non-striped muscle occurs in the prostatic part arranged longitudinally, chiefly at the colliculus 
 seminalis; in the membranous portion the direction of the fibres is chiefly circular, with a few lon- 
 gitudinal fibres intercalated ; the cavernous part has a few circular fibres posteriorly, but anteriorly 
 the muscular fibres are single and placed obliquely and longitudinally. 
 
 Closure of the Bladder. — As to the means by which the male urethra is kept 
 closed, it must be remembered that the so-called internal vesical sphincter of the 
 anatomists, which consists of non-striped muscle, is in reality an integral part of 
 the muscular coat of the bladder, and surrounds the orifice of the urethra as far 
 down as the prostatic portion, just above the colliculus seminalis. It is, however, 
 not the sphincter muscle. The proper sphincter urethrae (sph. vesicae externus) 
 lies below the latter. It is a completely circular muscle disposed around the 
 urethra, close above the entrance of the urethra into the septum urogenitale at the 
 apex of the prostate, where it exchanges fibres with the deep transverse muscle of 
 the perinasum which lies under it. 
 
 Some longitudinal fibres, which run along the upper margin of the prostate from the bladder, 
 belong to this sphincter muscle. Single transverse bundles passing forward from the surface of the 
 neck of the bladder, the transverse bands which lie within the prostate opposite the apex of the 
 colliculus seminalis, and a strong transverse bundle passing in front of the origin of the urethra, 
 into the substance of the prostate — all belong to the sphincter muscle {Henle). In the male urethra, 
 the blood vessels form a rich capillary plexus under the epithelium, below which is a wide-meshed 
 lymphatic plexus. 
 
 [Tonus of Sphincter Urethrse. — Open the abdomen of a rabbit, ligature one ureter, tie a 
 cannula in the other, and pour water into the bladder until it runs out through the urethra, which is 
 usually under a pressure of 1 6 to 20 inches. If the spinal cord be divided between the fifth and 
 seventh lumbar vertebrae, a column of six inches is sufficient to overcome the resistance of the 
 sphincter, while section at the fourth lumbar vertebra has no effect on the height of the pressure. 
 In such an animal the bladder becomes distended, but in one with its cord divided between the fifth 
 and seventh lumbar vertebrae, there is incontinence of urine (Fig. 270). In the former case because 
 the excito-motor impulses are cut off from the centre (5 to 7 vert.), and in the latter because the 
 tonus of the sphincter is destroyed [JCupressow). This tonus is denied by Landois and others.] 
 
 280. ACCUMULATION OF URINE— MICTURITION.— After 
 
 emptying the bladder, the urine slowly collects again, the bladder being thereby 
 gradually distended. [A healthy bladder may be said to be full when it contains 
 20 oz. {James).~\ As long as there is a moderate amount of urine in the bladder, 
 the elasticity of the elastic fibres surrounding the urethra, and that of the sphincter 
 of the urethra (and in the male of the prostate) suffice to retain the urine in the 
 bladder. This is shown by the fact that the urine does not escape from the bladder 
 after death. If the bladder be greatly distended (1.5 to 1.8 litre), so that its apex 
 projects above the pubes, the sensory nerves in its walls are stimulated and cause a 
 feeling of a full bladder, while at the same time the urethral opening is dilated, so 
 that a few drops of urine pass into the beginning of the urethra. Besides the sub- 
 jective feeling of a full bladder, this tension of the walls of the bladder causes a 
 reflex effect, so that the urinary bladder contracts periodically upon its fluid con- 
 tents, and so do the sphincter of the urethra and the muscular fibres of the urethra, 
 and thus the urethra is closed against the passage of these drops of urine. As 
 long as the pressure within the bladder is not very high, the reflex activity of the 
 transversely striped sphincter overcomes the other (as during sleep) ; but, as the 
 pressure rises and the distention increases, the contraction of the walls of the 
 
EFFECT OF NERVES ON MICTURITION. 473 
 
 bladder overcomes the closure produced by the sphincter, and the bladder is 
 emptied, as occurs normally in young children. 
 
 As age advances, the sphincter urethrae comes under the control of the will, so 
 that it can be contracted voluntarily, as occurs in man when he forcibly contracts 
 the bulbo cavernosus muscle to retain urine in the bladder. The sphincter ani 
 usually contracts at the same time. The reflex activity of the sphincter may also 
 be inhibited voluntarily, so that it may be completely relaxed. This is the condi- 
 tion when the bladder is emptied voluntarily. 
 
 Slight movements, confined to the bladder, occur during psychical or emotional disturbances 
 (e. g., anger, fear), [the bladder may be emptied involuntarily during a fright], after stimulation of 
 sensory nerves (P. Bert, v. Basch, Meyer), auditory impressions, restraining the respiration, and by 
 arrest of the heart's action. There are slight periodic variations coincident with variations in the 
 blood pressure. The contractions of the bladder cease after deep inspiration, and also during apncea 
 (Mosso and Pettacani). The excised bladder of the frog, and even portions free from ganglia, 
 exhibit rhythmical contractions, which are increased by heat (Pfalz). 
 
 Nerves. — The nerves concerned in the retention and evacuation of the urine 
 are : i. The motor nerves of the sphincter urethra?, which lie in the pudendal 
 nerve (anterior roots of the third and fourth sacral nerves). When these nerves 
 are divided, as soon as the bladder becomes so distended as to dilate the urethral 
 opening, the urine begins to trickle away (incontinence of urine). 2. The sen- 
 sory nerves of the urethra, which excite these reflexes, leave the spinal cord by 
 the posterior roots of the third, fourth, and fifth sacral nerves. Section of these 
 nerves also causes incontinence of urine. The centre in dogs lies opposite the 
 fifth, and in rabbits, opposite the seventh, lumbar vertebra (Budge). 3. Fibres- 
 pass from the cerebrum — those that convey voluntary impulses through the 
 peduncles, and the anterior columns of the spinal cord (according to Mosso and 
 Pellacani, through the posterior columns and the posterior part of the lateral col- 
 umns), to the motor fibres of the sphincter urethra?. 4. The inhibitory fibres 
 concerned in the reflex inhibition of the sphincter urethrae, take the same course 
 (perhaps from the optic thalamus?) downward through the cord to where the third, 
 fourth, and fifth sacral nerves leave it. 5. Sensory nerves proceed from the 
 urethra and bladder to the brain, but their course is not known. Some of the 
 motor and sensory fibres lie for a part of their course in the sympathetic. 
 
 Transverse section of the spinal cord above where the nerves leave it, is 
 always followed in the first instance by retention of urine, so that the bladder 
 becomes distended. This occurs because — (1) the section of the spinal cord 
 increases the reflex activity of the urethral sphincter ; and (2) because the inhi- 
 bition of this reflex can no longer take place. As soon, however, as the bladder 
 becomes so distended as in a purely mechanical manner to cause dilatation of 
 the urethral orifice, then the urine trickles away, but the amount of urine which 
 trickles out in drops is small. Thus the bladder becomes more and more dis- 
 tended, as the continuously distended walls of the organ yield to the increased 
 tension, so that the bladder may become distended to an enormous extent. The 
 urine very frequently becomes ammoniacal, and there results catarrh and inflam- 
 mation of the bladder (§ 263). 
 
 Voluntary Micturition. — Observers are not agreed as to the mechanism 
 concerned in emptying the bladder when it is only partially full. It is stated by 
 some that a voluntary impulse passes from the brain along a cerebral peduncle, 
 the anterior columns of the cord and the anterior roots of the third and fourth 
 sacral nerves, and partly through motor fibres from the second to the fifth lumbar 
 nerves (specially the third), to act directly upon the smooth muscular fibres of the 
 bladder. This is assumed, because electrical stimulation of any part of this nervous 
 channel causes contraction of the bladder. This view, however, does not seem to 
 be the true one. It is to be remembered that Budge showed that the sensor-y 
 nerves of the wall of the bladder are contained in the first, second, third, and 
 
474 
 
 VOLUNTARY MICTURITION. 
 
 fourth sacral nerves, and also in part in the course of the hypogastric plexus, 
 whence they ultimately pass by the rami communicantes into the spinal cord. 
 
 According to Landois, the smooth musculature of the bladder cannot be excited 
 directly by a voluntary impulse, but is always caused to contract reflexly. If we 
 wish to micturate when the urinary bladder contains a small quantity of urine, we 
 first excite the sensory nerves of the opening of the urethra, either by causing slight 
 contractions of the sphincter urethra?, or by means of slight abdominal pressure, 
 and thus force a little urine into the urethral orifice. This sensory stimulation 
 causes a reflex contraction of the walls of the urinary bladder. At the same time, 
 this condition is maintained voluntarily, by the action of the intracranial reflex 
 inhibitory centre of the sphincter urethrse. The centre for the reflex stimulation 
 of the movements of the walls of the urinary bladder is placed somewhat higher in 
 the spinal cord than that for the sphincter urethra?. In dogs, it is opposite the 
 fourth lumbar. vertebra (Gianuzzi, Budge). 
 
 Power gives the following account of the probable mechanism involved : — 
 
 " In the first place, looking at the ordinary sensations that are experienced as the bladder fills, we 
 
 Fig. 270. 
 
 Nervous mechanism of the bladder (Power), a, afferent nerve ot the sphincters ; S and M, sensory and motor 
 centres ; X, sensory fibres to brain ; Z, motor fibres from brain ; Y, inhibitory fibres. 
 
 may conclude that sensory impressions, rising gradually in intensity, are conveyed (through P) to 
 the sensory ganglia (S), from whence they are reflected (through i) to the motor centre (M), and 
 from thence to the sphincter, causing this to contract more firmly (Fig. 270). 
 
 " If the bladder becomes greatly distended, the impression is no longer wholly reflected, but 
 passes onward and upward to the brain (through S and along X), and excites conscious uneasiness 
 or pain. If it be desired to retain the water, an impulse is transmitted by motor fibres (through Z) 
 to the motor ganglion, M, and the excito-motor influence (of S) on the sphincter is intensified by 
 the will. 
 
 " But suppose that, instead of holding the water, it be desired to discharge it ; what happens ? 
 The phenomena that are then presented seem to necessitate the admission of an inhibitory, restraining, 
 or regulating centre, which must be in close proximity with the excito-motor centre, and, therefore, 
 at the lower part of the spinal cord, for the action of the will in this matter is not, like its own 
 voluntary muscles, rapid and instantaneous, but is exerted only after the lapse of a distinct interval, 
 and the result is a relaxation of the sphincter. 
 
 " We may conceive this impulse to pass down special fibres, Y, to an inhibitory centre, I, which 
 may either act directly (through L) on the motor centre, M, or possibly may send branches directly 
 to the sphincter muscles." 
 
 Painful stimulation of sensory nerves causes reflex contraction of the bladder and evacuation of 
 
RETENTION AND INCONTINENCE OF URINE. 475 
 
 the urine (in children during teething). Reflex contraction of the bladder can be brought about in 
 cats by stimulation of the inferior mesenteric ganglion. After section of all the nerves going to 
 the bladder, hemorrhage and asphyxia cause contraction by a direct effect upon the structures in the 
 wall of the bladder. As yet no one has succeeded in exciting artificially the inhibitory centre in 
 the brain for the sphincter muscle (Sokirwin and Kowalesky). 
 
 It seems probable that, as in the case of the anal sphincter (g 160), there is not a continuous tonic 
 reflex stimulation of the sphincter urethrse ; the reflex is excited each time by the contents. The 
 sphincter vesicae of the anatomists, which consists of smooth muscular tissue, does not seem to take 
 part in closing the bladder. Budge and Landois found that, after removal of the transversely-striped 
 sphincter urethras, stimulation of the smooth sphincter did not cause occlusion of the bladder, nor 
 could L. Rosenthal or v. Wittich convince themselves of the presence of tonus in this muscle. 
 Indeed, its very existence is questioned by Henle. 
 
 Changes of the Urine in the Bladder. — When the urine is retained in the bladder for a con- 
 siderable time, according to Kaupp, there is an increase in the sodium chloride and a decrease in 
 the urea and water. Urine which remains for a long time in the bladder is prone to undergo 
 ammoniacal decomposition. 
 
 Absorption. — The mucous membrane of the bladder is capable of absorbing substances — potas- 
 sium iodide and other soluble salts — very slowly. 
 
 As the ureters enter near the base of the bladder, the last secreted urine is always lowest. If a 
 person remain perfectly quiet, strata of urine are thus formed, and the urine may be voided so as to 
 ' prove this {Edlefien). 
 
 The pressure within the bladder, when in the supine position = 13 to 15 centimetres of water. 
 Increase of the intra-abdominal pressure (by inspiration, forced expiration, coughing, bearing down) 
 increases the pressure within the bladder. The erect posture also increases it, owing to the pressure 
 of the viscera from above [Schatz, Dubois). [James obtained 4 to 4.5 inch Hg as the highest 
 expulsive power of the bladder, including the abdominal pressure, voluntary and involuntary. In 
 paraplegia, where there is merely the expulsive power of the bladder, he found 20 to 30 inches of 
 water.] 
 
 [Hydronephrosis occurs when the ureters and pelvis of the kidney become dilated, owing to 
 partial and gradual obstruction of the outflow of urine from the ureters; if the obstruction become 
 complete, there is cessation of the urinary secretion. James has shown that the bladder remains 
 contracted for several seconds after it is emptied, and this is specially the case in irritable bladder ; 
 so that this condition may also give rise to hydronephrosis, by damming up the urine in the ureters.] 
 
 During micturition, the amount of urine voided at first is small, but it increases with the time, 
 and toward the end of the act it again diminishes. In men, the last drops of urine are ejected 
 from the urethra by voluntary contractions of the bulbo-cavernosus muscle. Adult dogs increase 
 the stream rhythmically by the action of this muscle. 
 
 281. RETENTION AND INCONTINENCE OF URINE.— Retention of urine, or 
 ischuria, occurs: 1. When there is obstruction of the urethra, from foreign bodies, concretions, 
 stricture, swelling of the prostate. 2. Paralysis or exhaustion of the musculature of the bladder; 
 the latter sometimes occurs after delivery, in consequence of the pressure of the child against the 
 bladder. 3. After section of the spinal cord (p. 473). 4. Where the voluntary impulses are unable 
 to act upon the inhibitory apparatus of the sphincter urethrse reflex, as well as when the sphincter 
 urethrse reflex is increased. 
 
 Incontinence of urine (stillicidium urinae) occurs in consequence of — 1. Paralysis of the 
 sphincter urethrse. 2. Loss of sensibility of the urethra, which, of course, abolishes the reflex of 
 the sphincter. 3. Trickling of the urine is a secondary consequence of section of the spinal cord, 
 or of its degeneration. 
 
 Strangury is an excessive reflex contraction of the walls of the bladder and sphincter, due to 
 stimulation of the bladder and urethra; it is observed in inflammation, neuralgia [and after the use 
 of some poisons, e.g., cantharides]. 
 
 Enuresis nocturna, or involuntary emptying of the bladder at night, may be due to an increased 
 reflex excitability of the wall of the bladder, or weakness of the sphincter. 
 
 282. COMPARATIVE AND HISTORICAL.— Among vertebrates, the urinary and 
 genital organs are frequently combined, except in the osseous fishes. The Wolffian bodies, which 
 act as organs of excretion during the embryonic period, remain throughout life in fishes and amphi- 
 bians, and continue to act as such (Gegenbaur). Fishes. — The myxinoids (cyclostomata) have 
 the simplest kidneys; on each side is a long ureter, with a series of short-stalked glomeruli, with 
 capsules arranged along it. Both ureters open at the genital pore. In the other fishes, the kidneys 
 lie often as elongated, compact masses along both sides of the vertebral column. The two ureters 
 unite to form a urethra, which always opens behind the anus, either united with the opening of the 
 genital organs or behind this. In the sturgeon and hag fish, the anus and orifice of the urethra 
 together form a cloaca. Bladder-like formations, which, however, are morphologically homologous 
 with the urinary bladder of mammals, occur in fishes, either on each ureter (ray, hag fish), or where 
 both join. In amphibians, the vasa efferentia of the testicles are united with the urinary tubules ; 
 
476 COMPARATIVE AND HISTORICAL. 
 
 the duct in the frog unites with the one on the other side, and both conjoined open into the cloaca, 
 while the capacious urinary bladder opens through the anterior wall of the cloaca. From reptiles 
 upward, the kidney is no longer a persistent Wolffian body, but a new organ. In reptiles, it is 
 usually flattened and elongated ; the ureters open singly into the cloaca, saurians and tortoises 
 have a urinary bladder. In birds, the isolated ureters open into the urogenital sinus, which opens 
 into the cloaca, internal to the excretory ducts of the genital apparatus. The urinary bladder is 
 always absent. In mammals, the kidneys often consist of many lobules, e. g., dolphin, ox. 
 
 Among invertebrates, the mollusca have excretory organs in the form of canals, which are 
 provided with an outer and an inner opening. In the mussel, this canal is provided with a spongy, 
 like organ, often with a central cavity, and consisting of ciliated secretory cells, placed at the base of 
 the gills (organ of Bojanus). In gasteropods, with analogous organs, uric acid has been found. 
 Insects, spiders and centipedes have the so-called Malpighian vessels, which are partly excretory 
 organs for uric acid and partly for bile. These vessels are long tubes, which open into the first part 
 of the large intestine. In crabs, blind tubes, connected with the intestinal tube, perhaps have the 
 same functions. The vermes also have renal organs. 
 
 Historical.— Aristotle directed attention to the relatively large size of the human bladder; he 
 named the ureters. Massa (1552) found lymphatics in the kidney. Eustachius (f 1580) ligatured 
 the ureters, and found the bladder empty. Cusanus (1565) investigated the color and weight of the 
 urine. Rousset (1581) described the muscular nature of the walls of the bladder. Vesling de- 
 scribed the trigone (1753). The first important chemical investigations on the urine date from the 
 time of van Helmont (1644). He isolated the solids of the urine, and found among them common 
 salt ; he ascertained the higher specific gravity of fever urine, and ascribed the origin of urinary 
 calculi to the solids of the urine. Scheele (1766) discovered uric acid and calcium phosphate. 
 Arand and K unckel, phosphorus ; Rouelle (1773), urea; and it got its name from Fourcroy and 
 Vauquelin (1799). Berzelius found lactic acid; Seguin, albumin in pathological urine; Liebig, 
 hippuric acid; Heintz and v. Pettenkofer, kreatin and kreatinin ; Wollaston (1810), cystin. Marcet 
 found xanthin ; and Lindbergson, magnesia carbonate. 
 
Functions of the Skin. 
 
 Fig. 271. 
 
 283. STRUCTURE OF THE SKIN.— The skin (3.3 to 2.7 mm. thick; 
 specific gravity, 1057) consists of — 
 [1. The epidermis ; 
 2. The chorium, or cutis vera, with the papillae (Fig. 272).] 
 
 The epidermis (0.08 to 0.12 mm. thick) consists of many layers ofstratified epithelial cells 
 united to each other by cement substance. The superficial layers — stratum corneum (Figs. 272, b, 
 and 271, c) — consist of several layers of dry, horny, non-nucle- 
 ated squames, which swell up in solution of caustic soda 
 (Fig. 272, E). [It is always thickest where intermittent 
 pressure is applied, as on the sole of the foot and palm of the 
 hand.] The next layer is the stratum lucidum (Oehl) — 
 it is clear and transparent in a section of skin, hence the 
 name. It consists of compact layers of clear cells with ves- 
 tiges of nuclei (Fig. 271, /). Under this is the rete muco- 
 sum or rete Malpighii (Fig. 272, d), consisting of many 
 layers of nucleated protoplasmic epithelial cells. These cells 
 contain pigment in the dark races, and in the skin of the 
 scrotum, and around the anus. [The superficial cells are 
 more fusiform and contain granules which stain deeply with 
 carmine. They constitute, 3, the stratum granulosum 
 (Fig. vji,g). In these cells the formation of keratin is 
 about to begin, and the granules have been called eleidin 
 granules by Ranvier. They are chemically on the way to be 
 transformed into keratin (Fig. 271). All corneous structures 
 contain similar granules in the area where the cells are be- 
 coming corneous. Then follow several layers of more or 
 less polyhedral cells, softer and more plastic in their nature, 
 and exhibiting the characters of so-called " prickle cells " 
 (Figs. 271, m, and 272, Rj. The deepest layers of cells are 
 more or less columnar and the cells are placed vertically 
 upon the papilla: (Fig. 273, g). Granular leucocytes or 
 wandering cells are sometimes found between these cells 
 (Biesiadecki). This layer, 4, has been called the stratum 
 Malpighii (Fig. 271, m). The rete Malpighii dips down 
 between adjacent papillae and forms interpapillary processes. 
 According to Klein, a delicate basement membrane sepa- 
 rates the epidermis from the true skin.] The superficial 
 layers of the epidermis are continually being thrown off, 
 while new cells are continually being formed in the deeper 
 layers of the skin by proliferation of the cells of the rete 
 Malpighii. There is a gradual change in the microscopic 
 and chemical characters of the cells as we pass from the 
 deepest to the most superficial layer of the epidermis. 
 
 f ( I ) Stratum corneum, 
 (2) Stratum lucidum, 
 
 , Stratum corneum 
 granulosum ; m, 
 nerve fibrils. 
 
 [Epidermis (Fig. 271),- 
 
 (3) Stratum granulosum, 1 „ . ,. , 
 
 (4) Stratum Malpighii, ' } Rete Mucosum.] 
 
 [In a vertical section of the skin stained with picrocarmine, the S. granulosum is deeply stained 
 red, and is thus readily distinguished among the other layers of the epidermis.] 
 
 No pigment is formed within the epidermis itself; when it is present, it is carried by leucocytes 
 from the subcutaneous tissue (Kiehl, Ehrmann, Aeby). 
 
 The chorium (Fig. 272, I, C) is beset throughout its entire surface by numerous (0.5 to 0.1 mm. 
 high) papilla? (Fig. 273, b), the largest being upon the volar surface of the hand and foot, on the 
 
 477 
 
478 
 
 STRUCTURE OF THE SKIN. 
 
 nipple and glans penis. Most of the papilloe contain a looped capillary (g), while in limited area 
 some of them contain a touch corpuscle (Fig. 273, e). The papillae are disposed in groups, 
 whose arrangement varies in different parts of the body. In the palm of the hand and sole of the 
 foot they occur in rows, which are marked out by the existence of delicate furrows on the surface 
 visible to the naked eye, The chorium consists of a dense network of bundles of white fibrous 
 tissue mixed with a network of elastic fibres, which are more delicate in the papillae. The con- 
 nective tissue contains many connective tissue corpuscles and numerous leucocytes. The deeper 
 
 Fig. 272. 
 
 Vertical section of the skin, with a hair and sebaceous gland, T. Epidermis and chorium shortened — 1, outer; 2, 
 inner fibrous layer of the hair follicle ; 3, hyaline layer of the hair follicle ; 4, outer root sheath ; 5, Huxley's 
 layer of the inner root sheath ; 6, Henle's layer of the same ; p, root of the hair, with its papilla ; A, arrector 
 pili muscle ; C, chorium ; a, subcutaneous fatty tissue ; b, epidermis (horny layer) ; d, rete Malpighii ; g, blood 
 vessels of papillae ; y, lymphatics of the same ; k. horny or corneous substance ; i, medulla or pith ; k t epider- 
 mis or cuticle of hair ; K, coil of sweat gland; E, epidermal scales (seen from above and en face) from the 
 stratum corneum ; R, prickle cells from the rete Malpighii; 91, superficial, and m, deep cells from the nail: 
 H, hair magnified ; e, cuticle ; c, medulla, with cells ; f,f, fusiform fibrous cells of the substance of the hair ; 
 x, cells of Huxley's layer; I, those of Henle's layer ; S, transverse section of a sweat gland from the axilla ; 
 a, smooth muscular fibres surrounding it; t, cells from a sebaceous gland, some of them containing granules 
 of oil. 
 
 connective-tissue layers of the chorium gradually pass into the subcutaneous tissue, where they 
 form a trabecular arrangement of bundles, leaving between them elongated rhomboidal spaces filled 
 for the most part with groups of fat cells (Fig. 272, u, a). [In microscopic sections, after the 
 action of alcohol, the fat cells not unfrequently contain crystals of margarin (Fig. 275).] The 
 long axis of the rhomb corresponds to the greater tension of the skin at that part (C. Longer). In 
 some situations the subcutaneous tissue is devoid of fat [penis, eyelids]. In many situations, the 
 
NAILS AND HAIR. 
 
 479 
 
 skin is fixed by solid fibrous bands to subjacent structures, as fasciae, ligaments or bones (tenacula 
 cutis), in other parts, as over bony prominences, bursse, filled with synovial fluid, occur. 
 
 Smooth muscular fibres occur in the chorium in certain situations on extensor surfaces {Neu- 
 mann) ; nipple, areola mammae, prepuce, perinseum, and in special abundance in the tunica dartos 
 of the scrotum. 
 
 Fig. 273. 
 
 Vertical section of the cutis vera and part of the epidermis, g, cells of the rete Malpighii ; a, capillary ; 6, papilla ; 
 e, blood vessels ; d, nerve fibre entering a Wagner's touch corpuscle, e ; f t section of a nerve fibre. 
 
 Fig. 275. 
 
 Fig. 274. 
 
 Papilla? of the skin, epidermis removed, blood vessels in- 
 jected ; some contain a Wagner's touch corpuscle, a, the 
 others a capillary loop. 
 
 Fat cells containing crystals of margarin. 
 
 284. NAILS AND HAIR.— The nails (specific gravity 1.19) consist of numerous layers of 
 solid, horny, homogeneous, epidermal or nail cells, which may be isolated with a solution of caustic 
 alkalies, when they swell up and exhibit the remains of an elongated nucleus (Fig. 272, «, m). 
 The whole under surface of the nail rests upon the nail bed ; the lateral and posterior edges lie in 
 a deep groove, the nail groove (Fig. 276, e). The chorium under the nail is covered throughout 
 its entire extent by longitudinal rows of papillae (Fig. 276, d). Above this there lies, as in the 
 
480 
 
 DEVELOPMENT OF THE NAILS AND HAIR. 
 
 skin, many layers of prickle cells like those in the rete Malpighii (Fig. 272, c), and above this again 
 is the substance of the nail (Fig. 276, a). [The stratum granulosum is rudimentary in the nail bed. 
 The substance of the nail represents the stratum lucidum, there being no stratum corneum (A7«'»).] 
 The posterior part of the nail groove and the half moon, brighter part or lunule, form the root of 
 the nail. They are, at the same time, the matrix, from which growth of the nail takes place. The 
 lunule is present in an isolated nail, and is due to diminished transparency of the posterior part of 
 the nail, owing to the special thickness and uniform distribution of the cells of the rete Malpighii 
 (Toldt). 
 
 Growth of the Nail. — According to Unna, the matrix extends to the front part of the lunule. 
 The nail grows continually from behind forward, and is formed by layers secreted or formed by the 
 matrix. These layers run parallel to the surface of the matrix. They run obliquely from above 
 and behind, downward and forward, through the thickness of the substance of the nail. The nail 
 is of the same thickness from the anterior margin of the lunule forward to its free margin. Thus 
 the nail does not grow in thickness in this region. In the course of a year the fingers produce about 
 2 grms. of nail substance, and relatively more in summer than in winter [Moleschott, Benecke). 
 
 Development. — Unna makes the following statements regarding the development of the nails : 
 1. From the second to the eighth month of foetal life the position of the nail is indicated by a 
 partial but marked horny condition of the epidermis on the back of the first phalanx, the " epony- 
 chium." The remainder of this substance is represented during life by the normally-formed epidermal 
 layer, which separates the future nail from the surface of the furrow. 2. The future nail is formed 
 under the eponychium, with its first nail cells still in front of the nail groove ; then the nail grows 
 and pushes forward toward the groove. At the seventh month, the nail (itself covered by the 
 
 Fig. 276. 
 
 Transverse section of one-half of a nail, a, nail substance ; b, more open layer of cells of the nail bed ; c, stratum 
 Malpighii ot the nail bed ; d^ transversely divided papillae ; e, nail groove : f t horny layer of e projecting over 
 the nail ; g, papillae of the skin on the back of the finger. 
 
 eponychium) covers the whole extent of the nail bed. 3. When, at a later period, the eponychium 
 splits off, the nail is uncovered. After birth the papillae are formed on the bed of the nail, while 
 simultaneously the matrix passes backward to the most posterior part of the groove. 
 
 Absence of Hairs. — The whole of the skin, with the exception of the palmar surface of the 
 hand, sole of the foot, dorsal surface of the third phalanx of the fingers and toes, outer surface of 
 the eyelids, glans penis, inner surface of the prepuce, and part of the labia, is covered with hairs, 
 which may be strong or fine (lanugo). 
 
 A Hair (specific gravity 1 .26) is fixed by its lower extremity (root) in a depression of the skin 
 or a hair follicle (Fig. 272, l,p) which passes obliquely through the thickness of the skin, some- 
 times as far as the subcutaneous tissue. The structure of a hair follicle is the following : I . The 
 outer fibrous layer (Figs. 272, 1, 278), composed of interwoven bundles of connective tissue, 
 arranged for the most part longitudinally, and provided with numerous blood vessels and nerves. 
 [It is just the connective tissue of the surrounding chorium.] 2. The inner fibrous layer (Figs. 
 272, 2, 277) consists of a layer of fusiform cells (? smooth muscular fibres) arranged circularly. 
 [It does not extend throughout the whole length of the follicle.] 3. Inside this layer is a trans- 
 parent, hyaline, glass-like basement membrane (Figs. 272, 3, 277), which ends at the neck of 
 the hair follicle ; while above it is continued as the basement membrane which exists between the 
 epidermis and chorium. In addition to these coverings, a hair follicle has epithelial coverings 
 which must be regarded in relation to the layers of the epidermis. Immediately within the glass- 
 like membrane is the outer root sheath (Figs. 272, 4, 277, 278), which consists of so many layers 
 of epithelial cells that it forms a conspicuous covering. It is, in fact, a direct continuation of the 
 
DEVELOPMENT OF THE NAILS AND HAIR. 
 
 481 
 
 Stratum Malpighii, and consists of many layers of soft cells, the cells of the outer layer being cylin- 
 drical. Toward the base of the hair follicle it becomes narrower, and is united to, and continuous 
 with, the cells of the root of the hair itself, at least in fully-developed hairs. The horny layer of 
 the epidermis continues to retain its properties as far down as the orifice of the sebaceous follicle, 
 below this point, however, it is continued as the inner root sheath. This consists of ( I ) a single 
 layer of elongated, flat, homogeneous, non-nucleated cells (Figs. 272, 6, 277 ', f—Henle 's layer) 
 placed next and within the outer root sheath. Within this lies (2) Huxley's layer (Figs. 272, 5, 
 277, g), consisting of nucleated, elongated, polygonal cells (Fig. 272, x, and 3), while the cuticle of 
 the hair follicle is composed of cells analogous to those of the surface of the hair itself. Toward 
 the bulb of the hair these three layers become fused together. 
 
 Fig. 278. 
 
 Fig. 277. 
 
 Transverse section of a hair below the neck of a hair 
 follicle, a, outer fibrous coat with 6, blood vessels ; 
 c, inner circularly disposed layer ; d, glass-like layer ; 
 e, outer, /, g, inner root sheath ;/, outer layer of the 
 same (Henle's sheath) ; g, inner layer of the same 
 (Huxley's sheath) ; A, cuticle ; /, hair. 
 
 Section of a hair follicle while a hair is being shed, a, outer 
 and middle sheaths of hair follicle ; b, hyaline membrane ; 
 c, papilla, with a capillary ; d, outer, e , inner root sheath; ' 
 f t cuticle of the latter ; g, cuticle of the hair ; h, young 
 non-medullated hair; i, tip of new hair ; /, hair knob of 
 the shed hair, with k, the remainder of the cast-off outer 
 root sheath. 
 
 [Coverings of a hair follicle arranged from without inward: — 
 _., . I (a) Longitudinally arranged fibrous tissue 
 
 'I W Circularly arranged spindle cells. 
 
 2. Glass-like (hyaline) membrane. 
 ' (a) Outer root sheath. 
 
 3. Epithelial layers, 
 
 4. The hair itself. 
 3 1 
 
 1(0 
 
 Inner root sheath. ( Henle's layer. 
 Cuticle of the hair. I Huxley s layer. 
 
482 THE GLANDS OF THE SKIN. 
 
 The arrector pili muscle (Fig. 272, A) is a fanlike arrangement of a layer of smooth muscular 
 fibres, which is attached below to the side of a hair follicle and extends toward the surface of the 
 chorium ; as it stretches obliquely upward, it subtends the obtuse angle formed by the hair follicle 
 and the surface of the skin, [or, in other words, it forms an acute angle with the hair follicle, and 
 between it and the follicle lies the sebaceous gland]. When these muscles contract, they raise 
 and erect the hair follicles, producing the condition of cutis anserina or goose skin. As the 
 sebaceous gland lies in the angle between fhe muscle and the hair follicle, contraction of the muscle 
 compresses the gland and favors evacuation of the sebaceous secretion. It also compresses the 
 blood vessels of the papilla [Unna). 
 
 The hair with its enlarged bulbous extremity — hair bulb — sits upon, or rather it embraces, the 
 papilla. It consists of — (1) the marrow or medulla (Fig. 272, i) which is absent in woolly hair 
 and in the hairs formed during the first years of life. It consists of two or three rows of cubical 
 cells (H, c). (2) Outside this lies the thicker cortex (h), which consists of elongated, rigid, horny, 
 fibrous cells (H, _/",/), while in and between these cells lie the pigment granules of the hair. (3) 
 The surface of the hair is covered with a cuticle {&), consisting of imbricated layers of non- 
 nucleated squames. 
 
 Gray Hair. — When the hair becomes gray, as in old age, this is due to a defective formation of 
 pigment in the cortical part. The silvery appearance of white hair is increased when small air 
 cavities are developed, especially in the medulla and to a less extent in the cortex, where they re- 
 flect the light. Landois records a case of the hair becoming suddenly gray in a man whose hair 
 became gray during a single night, in the course of an attack of delirium tremens. Numerous air 
 spaces were found throughout the entire marrow of the (blond) hairs, while the hair pigment still 
 remained. 
 
 Development of Hair. — According to Kolliker, from the 12th to 13th week of intra-uterine 
 life, solid finger-like processes of the epidermis are pushed down into the chorium. The process 
 becomes flasked shaped, while the central cells of the cylinder become elongated and form a conical 
 body, arising as it were from the depth of the recess. It soon differentiates into an inner darker 
 part, which becomes the hair, and a thinner, clearer, layer covering the former, the inner root 
 sheath. The outer cells, i. c , those lying next the wall of the sac, form the outer root sheath. 
 Outside this, again, the fibrous tissue of the chorium forms a rudimentary hair follicle, while one of 
 the papillae grows up against it, indents it, and becomes embraced by the bulb of the hair. This is 
 the hair papilla, which contains a loop of blood vessels. The cells of the bulb of the hair prolif- 
 erate rapidly, and thus the hair grows in length. The point of the hair is thereby gradually pushed 
 upward, pierces the inner root sheath, and passes obliquely through the epidermis. The hairs ap- 
 pear upon the forehead at the 19th week ; at the 23d to 25th week the lanugo hairs appear free, 
 and they have a characteristic arrangement on different parts of the body. 
 
 Physical Properties. — Hair has very considerable elasticity (stretching to 0.33 of its length), 
 considerable cohesion (carrying 3 to 5 lbs.), resists putrefaction for a longtime, and is highly hygro- 
 scopic. The last property is also possessed by epidermal scales, as is proved by the pains that occur 
 in old wounds and scars during damp weather. 
 
 Growth of a hair occurs by proliferation of the cells on the surface of the hair papilla, these cells 
 representing the matrix of the hair. Layer after layer is formed, and gradually the hair is raised 
 higher within its follicle. 
 
 Change of the Hair. — The results are by no means uniform. According to one view, when 
 the hair has reached its full length, the process of formation on the surface of the hair papilla is in- 
 terrupted ; the root of the hair is raised from the papilla, becomes horny, remains almost devoid of 
 pigment, and is gradually more and more lifted upward from the surface of the papilla, while its 
 lower bulbous end becomes split up like a brush. The lower empty part of the hair follicle becomes 
 smaller, while on the old papilla a new formation of a hair begins, the old hair at the same time 
 falling out [Kolliker, C. /.anger). According to Stieda, the old papilla disappears, while a new one 
 is formed in the hair follicle, and from it the new hair is developed. 
 
 According to Gotte, in addition to the hair which grows on the papilla, other hairs developed from 
 the outer root sheath are formed in the same hair follicle. Unna aga-n describes the growth and 
 change of the hair differently. He believes that each hair grows for a time from the surface of the 
 papilla. It then frees itself, and with its brush-like lower end or bulb is transplanted anew on the 
 outer root sheath, about the middle of the hair follicle. The free papilla can thus produce a new 
 hair, which may even grow alongside the former, until the former falls out. New recesses with new 
 papillae are formed latterly in the hair follicle, and from them new hairs arise. 
 
 285. THE GLANDS OF THE SKIN.— The sebaceous glands (Fig. 272, I, T) are 
 simple acinous glands, which open by a duct into the hair follicles of large hairs near their upper 
 part; in the case of small hairs, they may project from the duct of the gland (Fig. 279). In some 
 situations, the ducts. of the glands open free upon the surface, e. g., the glands of labia minora, 
 glans, prepuce (Tyson's glands), and the red margins of the lips. The largest glands occur in the 
 nose and in the labia ; they are absent only from the vola manus and planta pedis. The oblong 
 alveoli of the gland consist of a basement membrane lined with small polyhedral nucleated granular 
 secretory cells (Fig. 272, /). Within this are other polyhedral cells, whose substance contains numer- 
 
SKIN AS A PROTECTIVE COVERING. 
 
 483 
 
 ous oil globules ; the cells become more fatty as we pro- Fig. 279. 
 
 ceed toward the centre of the alveolus. The cells lining 
 the duct are continuous with those of the outer root sheath. 
 The detritus formed by the fatty metamorphosis of the cells 
 constitutes the sebum or sebaceous secretion. 
 
 The sweat glands (Fig. 272, I, k), sometimes called 
 sudoriparous glands, consist of a long blind tube, whose 
 lower end is arranged in the form of a coil placed in the 
 areolar tissue under the skin, while the somewhat smaller 
 upper end or excretory portion winds in a vertical, slightly 
 wave-like manner, through the chorium, and in a cork- 
 screw or spiral manner through the epidermis, where it 
 opens with a free, somewhat trumpet shaped mouth. The 
 glands are both very numerous and large in the palm of 
 the hand, sole of the foot, axilla, forehead, and around the 
 nipple ; few on the back of the trunk, and are absent on 
 the glans, prepuce, and margin of the lips. The circum- 
 anal glands and the ceruminous glands of the external 
 auditory meatus, and Moll's glands, which open into the 
 hair follicles of the eyelashes, are modifications of the 
 sweat glands. 
 
 Each gland tube consists of a basement membrane lined 
 by cells; the excretory part or sweat canal of the tube 
 is lined by several layers of cubical cells, whose surface is 
 covered by a delicate cuticular layer, a small central lumen 
 being left. Within the coil the structure is different. The 
 first part of the coil resembles the above, but as the coil is 
 the true secretory part of the gland, its structure differs 
 from the sweat canal. This, the so-called distal portion of 
 the tube, is lined by a single layer of moderately tall, clear 
 nucleated cylindrical epithelium (Fig. 272, S), often con- 
 taining oil globules (Ranvier). Smooth muscular fibres 
 (Kolliker) are arranged longitudinally along the tube in Sebaceous gland, with a lanugo hair, a, granu- 
 the large glands (Fig. 272, S, a). There is a distinct lar epithelium ;* rete Malpighii continu- 
 
 1 » • \\. t u a . »t„ j » ,v t. ous with a ; c, fatty cells and free fat ; 
 
 lumen present in the tube. As the duct passes through rf _ acini . ,; ^ h folliclc> with a smal i 
 
 the epidermis, it winds its way between the epidermal cells hair,/". 
 
 without any independent membrane lining it (Heynold). 
 
 A network of capillaries surrounds the coil. Before the arteries split up into capillaries, they 
 
 form a true rete mirabile around the coil (Briicke). This is comparable to the glomerulus of the 
 
 kidney, which may also be regarded as a rete mirabile. Numerous nerves pass to form a plexus, 
 
 and terminate in the glands (Tomsa). 
 
 The total number of sweat glands is estimated by Krause at ly^ millions, which gives a secretory 
 surface of nearly 1080 square metres. These glands secrete sweat. Nevertheless, an oily or fatty 
 substance is often mixed with the sweat. In some animals (glands in the sole of the foot of the 
 dog, and in birds) this oily secretion is very marked. 
 
 Lymphatics. — Numerous lymphatics occur in the cutis ; some arise by a blind end, and others 
 from loops within the papilla, on a plane lower than the vascular capillary. [These open into more 
 or less horizontal networks of tubular lymphatics in the cutis, and these again into the wide lym- 
 phatics of the subcutaneous tissue, which are well provided with valves.] Special lymphatic spaces 
 are disposed in relation with the hair follicles and their glands (Neumann), [and also with the fat 
 (Klein). The lymphatics of the skin are readily injected with Berlin blue by the puncture method.] 
 
 The blood vessels of the skin are arranged in several systems. There is a superficial system, 
 from which proceed the capillaries for the papillae. There is a deeper system of vessels which 
 supplies special blood vessels to (a) the fatty tissue; (b) the hair follicles, each of which has a 
 special vascular arrangement of its own, and in connection with this each sebaceous gland receives 
 a special artery ; (c) an artery goes also to each coil of a sweat gland, where it forms a dense plexus 
 of capillaries (Tomsa). 
 
 286. THE SKIN AS A PROTECTIVE COVERING.— The sub- 
 cutaneous fatty tissue fills up the depression between adjoining parts of the 
 body and covers projecting parts, so that a more rounded appearance of the body 
 is thereby obtained. It also acts as a soft, elastic pad and protects delicate parts 
 from external pressure (sole of the foot, palm of the hand), and it often surrounds 
 and protects blood vessels, nerves, etc. It is a bad conductor of heat, and thus 
 acts as one of the factors regulating the radiation of heat (§ 214, II, 4), and, there- 
 fore, the temperature of the body. The epidermis and cutis vera also act in the 
 
484 CUTANEOUS respiration: SEBUM — SWEAT. 
 
 same manner (§ 212). Klug found that the heat conduction is less through the 
 skin and subcutaneous fatty tissue than through the skin alone ; the epidermis 
 conducts heat less easily than the fat and the chorium. 
 
 The solid, elastic, easily movable cutis affords a good protection against external, 
 mechanical injuries; while the dry, impermeable, horny epidermis, devoid of 
 nerves and blood vessels, affords a further protection against the absorption of 
 poisons, and at the same time it is capable of resisting, to a certain degree, thermal 
 and even chemical actions. A thin layer of fatty matter protects the free surface 
 of the epidermis from the macerating action of fluids, and from the disintegrating 
 action of the air. The epidermis is important in connection with the fluids of the 
 body. It exerts a certain pressure upon the cutaneous capillaries, and, to a limited 
 extent, prevents too great diffusion of fluid from, the cutaneous vessels. Parts of 
 the skin robbed of their epidermis are red and are always moist. When dry, the 
 epidermis and the epidermal appendages are bad conductors of electricity (§ 326). 
 Lastly, we may say that the existence of uninjured epidermis prevents adjoining 
 parts from growing together. 
 
 As the epidermis is but slightly extensile, it is stretched over the folds and papillae of the cutis 
 vera, which becomes level when the skin is stretched, and the papillae may even disappear with 
 strong tension [Lewinski), 
 
 287. CUTANEOUS RESPIRATION: SEBUM— SWEAT.— The 
 
 skin, with a surface of more than 1 J^ square metres, has the following secretory 
 functions : — 
 
 1. The respiratory excretion ; 
 
 2. The secretion of sebaceous matter ; and 
 
 3. The secretion of sweat. 
 
 [Besides this the skin is protective, contains sense organs, is largely con- 
 cerned in regulating the temperature, and may be concerned in absorption.] 
 
 1. Respiration by the skin has been referred to already (J 131). The organs therein con- 
 cerned are the tubes of the sweat glands, moistened as they are with fluids, and surrounded by a 
 rich network of capillaries. It is uncertain whether or not the skin gives off a small amount of N 
 or ammonia. Rohrig made experiments upon an arm placed in an air-tight metal box. According 
 to him, the amount of C0 2 and H 2 excreted is subject to certain daily variations; it is increased 
 by digestion, increased temperature of the surroundings, the application of cutaneous stimuli, and 
 by impeding the pulmonary respiration. The exchange of gases also depends upon the vascularity 
 of certain parts of the skin, while the cutaneous absorption of O also depends upon the number of 
 colored corpuscles in the blood. 
 
 In frogs and other amphibians, with a thin, always moist epidermis, the cutaneous respiration is 
 more considerable than in warm-blooded animals In winter frogs, the skin alone yields ^ of the 
 total amount of C0 2 excreted; in summer frogs, % of the same {Bidder) ; thus, in these animals it 
 is a more important respiratory organ than the lungs themselves. 
 
 Suppression of the cutaneous activity, e.g., by varnishing or dipping the skin in oil, causes 
 death by asphyxia sooner than ligature of the lungs. Varnishing the Skin. — When the skin of 
 a warm-blooded animal is covered with an impermeable varnish [such as gelatin] (Fourcault, 
 Becquerel, Brechet), death occurs after a time, probably owing to the loss of too much heat. The 
 formation of crystalline ammonio-magnesic phosphate in the cutaneous tissues of such animals 
 [Edenhuizen), is not sufficient to account for death, nor are congestion of internal organs and serous 
 effusions satisfactory explanations. The retention of the volatile substances (acids) present in the 
 sweat is not sufficient. Strong animals live longer than feeble ones; horses die after several days 
 ( Gerlach) ; they shiver and lose flesh. The larger the cutaneous surface left unvarnished, the later 
 does death take place. Rabbits die when y% of their surface is varnished. When the entire surface 
 of the animal is varnished, the temperature rapidly falls (to 19 ) ; the pulse and respirations vary; 
 usually they fall when the varnishing process is limited ; increased frequency of respiration has been 
 observed (f 225). Pigs, dogs, horses, when one-half of the body is varnished, exhibit only a tem- 
 porary fall of the temperature, and show signs of weakness, but do not die (Ellenberger and Hof- 
 meister). [In extensive burns of the skin, not only is there disintegration of the colored blood 
 corpuscles (v. Lesser), but in some cases ulcers occur in the duodenum. The cause of the ulcera- 
 tion, however, has not been ascertained satisfactorily (Curling).~\ 
 
 2. Sebaceous Secretion. — The fatty matter as it is excreted from the acini 
 of the sebaceous glands is fluid, but even within the excretory duct of the gland 
 
CHEMICAL COMPOSITION. 485 
 
 it stagnates and forms a white, fat-like mass, which may sometimes be expressed 
 (at the side of the nose) as a worm-like, white body, the so-called comedo. The 
 sebaceous matter keeps the skin supple, and prevents the hair from becoming too 
 dry. Microscopically, the secretion is seen to contain innumerable fatty 
 granules, a few gland cells filled with fat, visible after the addition of caustic 
 soda, crystals of cholesterin, and in some men a microscopic, mite-like animal 
 (Demodex folliculorum). 
 
 Chemical Composition. — The constituents are, for the most part, fatty ; chiefly olein (fluid) and 
 palmitin (solid) fat, soaps and some cholesterin ; a small amount of albumin and unknown ex- 
 tractives. Among the inorganic constituents, the insoluble earthy phosphates are most abundant ; 
 while the alkaline chlorides and phosphates are less abundant. 
 
 The vernix caseosa, which covers the skin of a new-born child, is a greasy mixture of sebaceous 
 matter and macerated epidermal cells (containing 47.5 per cent. fat). A similar product is the 
 smegma praeputialus (52.8 per cent, fat), in which an ammonia soap is present. 
 
 The cerumen, or ear wax, is a mixture of the secretions of the ceruminous glands of the ear 
 (similar in structure to the sweat glands) and the sebaceous glands of the auditory canal. Besides 
 the constituents of sebum, it contains yellow or brownish particles, a bitter yellow extractive sub- 
 stance derived from the ceruminous glands, potash soaps and a special fat [Berzilius). The secre- 
 tion of the Meibomian glands is sebum. 
 
 [Lanoline. — Liebreich finds in feathers, hairs, wool, and keratin tissues generally, *. cholesterin 
 fat, which, however, is not a true fat, although it saponifies, but an ethereal compound of certain 
 fatty acids with cholesterin. In commerce it is obtained from wool, and is known by the above 
 name; it forms an admirable basis for ointments, and it is very readily absorbed by the skin.] Thus, 
 the fat-like substance for protecting the epidermis is partly formed along with keratin in the epi- 
 dermis itself. 
 
 3. The Sweat. — The sweat is secreted in the coil of the sweat glands. As 
 long as the secretion is small in amount, the water secreted is evaporated at once 
 from the skin, along with the volatile constituents of the sweat ; as soon, how- 
 ever, as the secretion is increased, or evaporation is prevented, drops of sweat 
 appear on the surface of the skin. The former is called insensible perspira- 
 tion, and the latter sensible perspiration. [Broadly, the quantity is about 2 
 ft>s. in twenty-four hours.] 
 
 The sensible perspiration varies greatly ; as a rule, the right side of the body perspires more 
 freely than the left. The palms of the hands secrete most, then follow the soles of the feet, cheek, 
 breast, upper arm and forearm (Peiper). It falls from morning to mid-day, and rises again toward 
 evening (Tanssen). 
 
 Method. — Sweat is obtained from a man by placing him in a metallic vessel in a warm bath ; 
 the sweat is rapidly secreted and collected in the vessel. In this way Favre collected 2560 grammes 
 of sweat in 1)4 hours. An arm may be inclosed in a cylindrical vessel, which is fixed air tight 
 round the arm with an elastic bandage (Schotiin). 
 
 Among animals, the horse sweats, so does the ox, but to a less extent ; the vola and planta of 
 apes, cats and the hedgehog secrete sweat; the snout of the pig sweats (?), while the goat, rabbit, 
 rat, mouse and dog are said not to sweat [Luchsinger). [The skin over the body and the pad on 
 the dog's foot contain numerous sweat glands, which open free on the surface of the pad and into 
 the hair follicles on the general surface of the skin ( W. Stirling).'] 
 
 Microscopically. — The sweat contains only a few epidermal scales accidentally mixed with it, 
 and fine fatty granules from the sebaceous glands. 
 
 Chemical Composition. — Its reaction is alkaline, although it frequently is 
 acid, owing to the admixture of fatty acids from decomposed sebum. During 
 profuse secretion it becomes neutral, and, lastly, alkaline again (Triimpy and 
 Luchsinger). The sweat is colorless, slightly turbid, of a saltish taste, and has a 
 characteristic odor, varying in different parts of the body ; the odor is due to the 
 presence of volatile fatty acids. The constituents are — water, which is increased 
 by copious draughts of that fluid. The solids amount to 1.180 per cent. (0.70 
 to 2.66 per cent. — Funke), and of these 0.96 per cent, is organic and 0.33 inor- 
 ganic. Among the organic constituents are neutral fats (palmitin, stearin), also 
 present in the sweat of the palm of the hand, which contains no sebaceous glands 
 (Krause~), cholesterin, volatile fatty acids (chiefly formic, acetic, butyric, propionic, 
 caproic, capric acids), varying qualitatively and quantitatively in different parts 
 
486 INFLUENCE OF NERVES ON THE SECRETION OF SWEAT. 
 
 of the body. These acids are most abundant in the sweat first (acid) secreted. 
 There are also traces of albumin (similar to casein), and urea, about o. i per cent. 
 (Funke, Ficard). In ursemic conditions (anuria in cholera), urea has been found 
 crystallized on the skin (Schottin, Drasche). When the secretion of sweat is 
 greatly increased, the amount of urea in the urine is diminished both in health 
 and in uraemia {Leube). The nature of the reddish-yellow pigment, which is 
 extracted from the residue of sweat by alcohol, and colored green by oxalic acid, 
 is unknown. Among inorganic constituents, those that are easily soluble are more 
 abundant than .those that are soluble with difficulty, in the proportion of 17 
 to 1 (Schoitiri); sodium chloride, 0.2; potassium chloride, 0.2; sulphates, 0.01 
 per 1000, together with traces of earthy phosphates and sodium phosphate. Sweat 
 contains C0 2 in a state of absorption and some N. When decomposed with free 
 access of air, it yields ammonia salts (Gorup-Besanez). 
 
 Excretion of Substances. — Some substances when introduced into the body reappear in the 
 sweat ; benzoic, cinnamic, tartaric and succinic acids are readily excreted ; quinine and potassium 
 iodide with more difficulty. Mercuric chloride, arsenious and arsenic acids, sodium and potassium 
 arseniate have also been found. After taking arseniate of iron, arsenious acid has been found in 
 the sweat, and iron in the urine. Mercury iodide reappears as a chloride in the sweat, while the 
 iodine occurs in the saliva. 
 
 Formation of Pigment. — The leucocytes furnish the material, and the pig- 
 ment is deposited in granules in the deeper layers, and, to a less extent, in the 
 upper layers of the rete Malpighii. This occurs in the folds around the anus, 
 scrotum, nipple [especially during pregnancy], and everywhere in the colored 
 races. There is a diffuse, whitish-yellow pigment in the stratum corneum, which 
 becomes darker in old age. The pigmentation depends on chemical processes, 
 reduction taking place, and these processes are aided by light. Granular pig- 
 ment lies also in the layers of prickle cells. The dark coloration of the skin may 
 be arrested by free O [hydric peroxide], while the corneous change is prevented 
 at the same time (Unnd). 
 
 Pathological. — To this belongs the formation of liver spots or chloasma, freckles, and the 
 pigmentation of Addison's disease [pigmentation round old ulcers, etc., ] (\ 103, IV). [The 
 curious cases of pigmentation, especially in neurotic women, e.g., in the eyelids, deserve further 
 study in relation to the part played by the nervous system in this process.] 
 
 288. INFLUENCE OF NERVES ON THE SECRETION OF 
 SWEAT. — The secretion of the skin, which averages about -fa of the body 
 weight, i.e., about double the amount of water excreted by the lungs, maybe 
 increased or diminished. The liability to perspire varies much in different indi- 
 viduals. The following conditions influence the secretion : 1. Increased tem- 
 perature of the surroundings causes the skin to become red, while there is a pro- 
 fuse secretion of sweat (§ 214, II, 1). Cold, as well as a temperature of the skin 
 about 50 C, arrest the secretion. 2. A very watery condition of the blood, 
 e.g., after copious draughts of warm water, increases the secretion. 3. Increased 
 cardiac and vascular activity, whereby the blood pressure within the cuta- 
 neous capillaries is increased, has a similar effect ; increased sweating follows 
 increased muscular activity. 4. Certain drugs favor sweating, e.g., pilo- 
 carpi, Calabar bean, strychnin, picrotoxin, muscarin, nicotin, camphor, ammonia 
 compounds, while others,_ as atropin and morphia, in large doses, diminish or 
 paralyze the secretion. [Drugs which excite copious perspiration, so that it stands 
 as beads of sweat on the skin, are called sudorifics, while those that excite the 
 secretion gently are diaphoretics, the difference being one of degree. Those 
 drugs which lessen the secretion are called antihydrotics.] 5. It is important 
 to notice the antagonism which exists, probably upon mechanical grounds, between 
 the secretion of sweat, the urinary secretion, and the evacuation of the intestine. 
 Thus, copious secretion of urine (e.g. , in diabetes) and watery stools coincide 
 with dryness of the skin. If the secretion of sweat be increased, the percentage 
 
INFLUENCE OF NERVES ON THE SECRETION OF SWEAT. 487 
 
 of salts, urea {Funke), and albumin is also increased {Leube), while the other 
 organic substances are diminished. The more saturated the air is with watery 
 vapor, the sooner does the secretion appear in drops upon the skin, while in dry 
 air or air in motion, owing to the rapid evaporation, the formation of drops of 
 sweat is prevented, or at least retarded. [The complementary relation between 
 the skin and kidneys is known to every one. In summer, when the skin is 
 active, the kidneys separate less water ; in winter, when the skin is less active, it 
 is cold and comparatively bloodless, while the kidneys excrete more water, so that 
 the action of these two organs is in inverse ratio.] 
 
 The influence of nerves upon the secretion of sweat is very marked. 
 
 I. Just as in the secretion of saliva (§ 145), vasomotor nerves are usually in 
 action at the same time as the proper secretory nerves ; the vaso-dilator 
 nerves (sweating with a red congested skin) are most frequently involved. The 
 fact that secretion of sweat does occasionally take place when the skin is pale 
 (fear, death agony) shows that, when the vasomotor nerves are excited, so as to 
 constrict the cutaneous blood vessels, the sweat-secretory nerve fibres may also be 
 active. 
 
 Under certain circumstances the amount of blood in the skin seems to determine the occurrence 
 of sweating ; thus Dupuy found that section of the cervical sympathetic caused secretion on that 
 side of the neck of a horse ; while Nitzelnadel found that percutaneous electrical stimulation of 
 the cervical sympathetic in man limited the sweating.? 
 
 [We may draw a parallel between the secretion of saliva and that of sweat. Both are formed 
 in glands derived from the outer layer of the embryo. Both are formed from lymph supplied by 
 the blood stream, and if the lymph be in sufficient quantity, secretion may take place when there is 
 no circulation, although in both cases secretion is most lively when the circulation is most active 
 and the secretory nerves of both are excited simultaneously ; both have secretory nerves distinct 
 from the nerves of the blood vessels ; both may be paralyzed by the action of the nervous system, 
 or in disease (fever), or conversely, both are paralyzed by atropine and excited by other drugs, e.g., 
 pilocarpin. In the gland cells of both histological, changes accompany the secretory act, and no 
 doubt similar electro-motor phenomena occur in both glands.] 
 
 II. Secretory nerves, altogether independent of the circulation, control the 
 secretion of sweat. Stimulation of these nerves, even in a limb which has been 
 amputated in a kitten, causes a temporary secretion of sweat, i.e., after complete 
 arrest of the circulation (Goltz, Kendall and Luchsinger, Ostroumow). In the 
 intact condition of the body, however, profuse perspiration, at all events, is 
 always associated with simultaneous dilatation of the blood vessels (just as, in 
 stimulation of the facial nerve, an increased secretion of saliva is associated with 
 an increased blood stream — § 145, A, I). The secretory nerves and those for 
 the blood vessels seem to lie in the same nerve trunks. 
 
 The secretory nerves for the hind limbs (cat) lie in the sciatic nerve. Luch- 
 singer found that stimulation of the peripheral end of this nerve caused renewed 
 secretion of sweat for a period of half an hour, provided the foot was always wiped to 
 remove the sweat already formed. If a kitten, whose sciatic nerve is divided on 
 one side, be placed in a chamber filled with heated air, all the three intact limbs 
 soon begin to sweat, but the limb whose nerve is divided does not, nor does it do 
 so when the veins of the limb are ligatured so as to produce congestion of its 
 blood vessels. [The cat sweats only on the hairless soles of the feet.] As to the 
 course of the secretory fibres to the sciatic nerve, some pass directly from the 
 spinal cord ( Vulpian), some pass into the abdominal sympathetic {Luchsinger, 
 Nawrocki, Ostroumow), through the rami communicantes and the anterior spinal 
 roots from the upper lumbar and lower dorsal spinal cord (9th to 13th dorsal ver- 
 tebrae — cat) where the sweat centre for the lower limbs is situated. 
 
 The sweat centre may be excited directly: (1) By a strongly venous con- 
 dition of the blood, as during dyspnoea, e.g., in the secretion of sweat that some- 
 times precedes death; (2) by overheated blood (45 ° C.) streaming through the 
 centre; (3) by certain poisons (see p. 486). The centre may be also excited 
 reflexly, although the results are variable, e.g., stimulation of the crural and 
 
488 PATHOLOGICAL VARIATIONS OF SWEATING. 
 
 peroneal nerves, as well as the central end of the opposite sciatic nerve excites it 
 (Luchsinger). [The pungency of mustard in the mouth may excite free perspira- 
 tion on the face.] 
 
 Anterior Extremity. — The secretory fibres lie in the ulnar and median nerves, 
 for the fore limbs of the cat; most of them, or indeed all of them (Nawrocki) 
 pass into the thoracic sympathetic (Ggl. stellatum), and part (?) runs in the nerve 
 roots direct from the spinal cord {Luchsinger, Vulpian, Otf). A similar sweat 
 centre for the upper limbs lies in the lower part of the cervical spinal cord. Stim- 
 ulation of the central ends of the brachial plexus causes a reflex secretion of sweat 
 upon the foot of the other side (Adamkiewicz). At the same time the hind feet 
 also perspire. 
 
 Pathological. — Degeneration of the motor ganglia of the anterior horns of the spinal cord causes 
 loss of the secretion of sweat, in addition to paralysis of the voluntary muscles of the trunk. The 
 perspiration is increased in paralyzed as well as in cedamatous limbs. In nephritis, there are great 
 variations in the amount of water given off by the skin. 
 
 Head. — The secretory fibres for this part (horse, man, snout of pig) lie in the 
 thoracic sympathetic, pass into the ganglion stellatum, and ascend in the cervical 
 sympathetic. Percutaneous electrical stimulation of the cervical sympathetic in 
 man, causes sweating of that side of the face and of the arm (M. Meyer). In the 
 cephalic portion of the sympathetic, some of the fibres pass into, or become 
 applied to, the branches of the trigeminus, which explains why stimulation of 
 the infraorbital nerve causes secretion of sweat. Some fibres, however, arise 
 directly from the roots of the trigeminus (Luchsinger), and the facial (Vulpian, 
 Adamkiewicz). Undoubtedly the cerebrum has a direct effect either upon the 
 vasomotor nerves (p. 487, I) or upon the sweat-secretory fibres (II), as in the 
 sweating produced by psychical excitement (pain, fear, etc.). 
 
 Adamkiewicz and Senator found that, in a man suffering from abscess of the motor region of the 
 cortex cerebri for the arm, there were spasms and perspiration in the arm. 
 
 Sweat Centre. — According to Adamkiewicz, the medulla oblongata contains 
 the dominating sweat centre (§ 373 — Marme, Nawrocki). When this centre 
 is stimulated in a cat, all the four feet sweat, even three-quarters of an hour after 
 death (Adamkiewicz). 
 
 III. The nerve fibres which terminate in the smooth muscular fibres of the sweat 
 glands act upon the excretion of the secretion. 
 
 [Changes in the Cells during Secretion. — In the resting glands of the 
 horse, the cylindrical cells are clear with the nucleus near their attached ends, but 
 after free perspiration they become granular, and their nucleus is more central 
 (Renaut ).] 
 
 If the sweat nerves be divided (cat), injection of pilocarpin causes a secretion of sweat, even at 
 the end of three days. After a longer period than six days there may be no secretion at all. This 
 observation coincides with the phenomenon of dryness of the skin in paralyzed limbs. Dieffenbach 
 found that transplanted portions of skin first began to sweat when their sensibility was restored. If 
 a motor nerve (tibial, median, facial) of a man be stimulated, sweat appears on the skin over the 
 muscular area supplied by the nerve, and also upon the corresponding area of the opposite non- 
 stimulated side of the body. This result occurs when the circulation is arrested as well as when it 
 is active. Sensory and thermal stimulation of the skin always cause a bilateral reflex secretion inde- 
 pendently of the circulation. The area of sweating is independent of the part of the skin stimu- 
 lated {Adamkiewicz). 
 
 289. PATHOLOGICAL VARIATIONS. — I. Anidrosis or diminution of the secretion of 
 sweat occurs in diabetes and the cancerous cachexia, and along with other disturbances of nutrition 
 of the skin in some nervous diseases, e.g., in dementia paralytica ; in some limited regions of the skin 
 it has occurred in certain tropho-neuroses , e.g., in unilateral atrophy of the face and in paralyzed 
 parts. In many of these cases it depends upon paralysis of the corresponding nerves (Eulenburg) or 
 their spinal sweat centres. 
 
 2. Hyperidrosis, or increase of the secretion of sweat, occurs in easily excitable persons, in 
 consequence of the irritation of the nerves concerned ({! 288), e.g., the sweating which occurs in 
 debilitated conditions and in the hysterical (sometimes on the head and hands), and the so called 
 
CUTANEOUS ABSORPTION. 489 
 
 epileptoid sweats (Eulenburg). Sometimes the increase is confined to one side of the head (H. uni- 
 lateralis). This condition is often accompanied with other nervous phenomena, partly with the 
 symptoms of paralysis of the cervical sympathetic (redness of the face, narrow pupil), partly with 
 symptoms of stimulation of the sympathetic (dilated pupil, exophthalmos). It may occur without 
 these phenomena, and is due, perhaps, to stimulation of the proper secretory fibres alone. [Increased 
 sweating is very marked in certain fevers, both during their course and at the crisis in some ; while 
 the sweat is not only copious, but acid in acute rheumatism. The " night sweats " of phthisis are 
 very marked and disagreeable.] 
 
 3. Paridrosis or qualitative changes in the secretion of sweat, e. g., the rare case of " sweat- 
 ing of blood" (Hsematohidrosis), is sometimes unilateral. According to Hebra, in some cases 
 this condition represents a vicarious form of menstruation. It is, however, usually one of many phe- 
 nomena of nervous affections. Bloody sweat sometimes occurs in yellow fever. Bile pigments 
 have been found in the sweat in jaundice; blue sweat from indigo (Bizio), from pyocyanin (the 
 rare blue coloring matter of pus), or from phosphate of the oxide of iron (Osc. Kollmann) is ex.- 
 tremely rare. Such colored sweats are called chromidrosis. Bacteria are frequently found, both 
 in normal and in abnormal sweat, in yellow, blue, and red sweat. Grape sugar occurs in the sweat 
 in diabetes mellitus ; uric acid and cystin very rarely ; and in the sweat of stinking feet, leucin, 
 tyrosin, valerianic acid and ammonia. Stinking sweat (Bromidrosis) is due to the decomposition 
 of the sweat, from the presence of a special micro-organism (Bacterium fcetidum — Thin). In the 
 sweating stage of ague butyrale of lime has been found, while in the sticky sweat of acute articular 
 rheumatism there is more albumin (Anselmino), and the same is the case in artificial sweating 
 (Leube) ; lactic acid is present in the sweat in puerperal fever. 
 
 The sebaceous secretion is sometimes increased, constituting Seborrhcea, which may be local or 
 general. It may be diminished (Asteatosis cutis). The sebaceous glands degenerate in old 
 people, and hence the glancing of the skin (Rimy). If the ducts of the glands are occluded the 
 sebum accumulates. Sometimes the duct is occluded by black particles or ultramarine (Uhna) from 
 the blue used in coloring the linen. When pressed out, the fatty, worm-shaped secretion is called 
 " comedo." 
 
 290. CUTANEOUS ABSORPTION— GALVANIC CONDUCTION.— After long im- 
 mersion in water the superficial layers of the epidermis become moist and swell up. The skin is 
 unable to absorb any substances, either salts or vegetable poisons, from watery solutions of these. 
 This is due to the fat normally present on the epidermis and in the pores of the skin. If the fat be 
 removed from the skin by alcohol, ether, or chloroform, absorption may occur in a few minutes 
 (Parisot). According to Rohrig, all volatile substances, e. g., carbolic acid and others, which act 
 upon and corrode the epidermis, are capable of absorption. While according to Juhl, such watery 
 solutions as impinge on the skin, in a finely divided spray, are also capable of absorption, which very 
 probably takes place through the interstices of the epidermis. 
 
 [Inunction. — When ointments are rubbed into the skin so as to press the substance into the 
 pores, absorption occurs, e. g., potassium iodide in an ointment so rubbed in is absorbed, so is mer- 
 curial ointment, v. Voit found globules of mercury between the layers of the epidermis, and even 
 in the chorium of a person who was executed, into whose skin mercurial ointment had been previ- 
 ously rubbed. The mercury globules, in cases of mercurial inunction, pass into the hair follicles 
 and ducts of the glands, where they are affected by the secretion of the glands and transformed into 
 a compound capable of absorption. An abraded or inflamed surface (e.g., after a blister), where 
 the epidermis is removed, absorbs very rapidly, just like the surface of a wound (Endermic 
 method).] 
 
 [Drugs may be applied locally where the epidermis is intact — Epidermic method — as when 
 drugs which affect the sensory nerves of a part are painted over a painful area to diminish the pain. 
 Another method, the hypodermic, now largely used, is that of injecting, by means of a hypodermic 
 syringe, a non-corrosive, non-irritant drug, in solution, into the subcutaneous tissue, where it prac- 
 tically passes into the lymph spaces and comes into direct relation with the lymph and blood stream, 
 absorption takes place with great rapidity, even more so than from the stomach.] 
 
 Gases. — Under normal conditions, minute traces of O are absorbed from the air ; hydrocyanic 
 acid, sulphuretted hydrogen — CO, C0 2 , the vapor of chloroform and ether may be absorbed (Chaus- 
 sier, Gerlach, Rohrig). In a bath containing sulphuretted hydrogen, this gas is absorbed, while C0 2 
 is given off into the water (Rohrig). 
 
 Absorption of watery solutions takes place rapidly through the skin of the frog ( Guttmann, 
 W. Stirling, v. Wittich). Even after the circulation is excluded and the central nervous system 
 destroyed, much water is absorbed through the skin of the frog, but not to such an extent as when 
 the circulation is intact (Spina). .. 
 
 Galvanic Conduction through the Skin. — If the two electrodes of a constant current be 
 impregnated with a watery solution of certain substances and applied to the skin, and if the direc- 
 tion of the current be changed from time to time, strychnin may be caused to pass through the skin 
 of a rabbit in a few minutes, and that in sufficient amount to kill the animal (H. Muni). In man, 
 quinine and potassium iodide have been introduced into the body in this way, and their presence 
 detected in the urine. This process is called the cataphoric action of the constant current (J 328). 
 
490 COMPARATIVE — HISTORICAL. 
 
 291. COMPARATIVE— HISTORICAL. — In all vertebrates, the skin consists of chorium 
 and epidermis. In some reptiles, the epidermis becomes horny, and forms large plates or scales. 
 Similar structures occur in the edentata among mammals. The epidermal appendages assume 
 various forms -sucli as hair, nail, spines, bristles, feathers, claws, hoof, horns, spurs, etc. The 
 scales of some fishes are partly osseous structures. Many glands occur in the skin ; in some am- 
 phibia they secrete mucus, in others the secretion is poisonous. Snakes and tortoises are devoid of 
 cutaneous glands ; in lizards the " leg glands " extend from the anus to the bend of the knee. In 
 the crocodile, the glands open under the margins of the cutaneo-osseous scales. In birds, the 
 cutaneous glands are absent ; the " coccygeal glands" form an oily secretion for lubricating the 
 feathers. [This is denied by O. Liebreich, as he finds no cholesterin fats in their secretion.] The 
 civet glands, at the anus of the civet cat, the preputial glands of the musk deer, the glands of the 
 hare, and the pedal glands of ruminants, are really greatly developed sebaceous glands. In some 
 invertebrata, the skin, consisting of epidermis and chorium, is intimately united with the subjacent 
 muscles, forming a musculo-cutaneous tube for the body of the animal. The cephalopoda have 
 chromatophores in their skin, i. e., round or irregular spaces filled with colored granules. Mus- 
 cular fibres are arranged radially around these spaces, so that when these muscles contract the 
 colored surface is increased. The change of color in these animals is due to the play or contraction 
 of these muscles. (Briicke.) Special glands are concerned in the production of the shells of the 
 snail. The annulosa are covered with a chitinous investment, which is continued for a certain 
 distance along the digestive tract and the trachea. It is thrown off when the animal sheds its cover- 
 ing. It not only protects the animal, but it forms a structure for the attachment of muscles. In 
 echinodermata, the cutaneous covering contains calcareous masses ; in the holothurians, the calca- 
 reous structures assume the form of calcareous spicules. 
 
 Historical. — Hippocrates (born 460 B. c.) and Theophrastus (born 371 B.C.) distinguished the 
 perspiration from the sweat; and, according to the latter, the secretion of sweat stands in a certain 
 antagonistic relation to the urinary secretion and to the water in the faeces. According to Cassins 
 Felix (97 A. D.), a person placed in a bath absorbs water through the skin; Sanctorius (1614) 
 measured the amount of sweat given off; Alberti (1581) was acquainted with the hair bulb ; Donatus 
 (1588) described hair becoming gray suddenly; Riolan (1626) showed that the color of the skin 
 of the negro was due to the epidermis. 
 
Physiology s motor apparatus. 
 
 292. CILIARY MOTION — PIGMENT CELLS.— {a) Muscular 
 Movement. — By far the greatest number of the movements occuring in our 
 bodies is accomplished through the agency of muscular fibre, which, when it 
 is excited by a stimulus, contracts — i. e., it forcibly shortens — and thus brings its 
 two ends nearer together, while it bulges to a corresponding extent laterally. In 
 muscle, the contraction takes place in a definite direction. 
 
 (p) Amoeboid Movement. — Motion is also exhibited by colorless blood 
 corpuscles, lymph corpuscles, leucocytes, and some other corpuscles. In these 
 structures we have examples of amceboid movement (§ 9), which is movement in 
 an indefinite direction. 
 
 [(c) Ciliary Movement. — There is also a peculiar form of movement, known 
 as ciliary movement. There is a gradual transition between these different forms of 
 movement. The cilia, which are attached to the ciliated epithelium, are the 
 motor agents (Fig. 280).] 
 
 [Ciliated epithelium, and where found. — In the nasal mucous membrane, except the olfactory 
 region; the cavities accessory to the nose; the upper half of the pharynx, Eustachian tube, larynx, 
 trachea and bronchi ; in the menu, except the lower half of the cervix ; Fallopian tubes ; vasa 
 
 Fig. 280. 
 
 Ciliated epithelium "fc . -JgrniffgifljiBp!!^ Clear disk. 
 
 Intermediate forms. 
 
 Inner layer. 
 Debove's membrane. 
 
 Ciliated epithelium. 
 
 efferentia to the lower end of epididymis ; ventricles of brain (child) ; and the central canal of the 
 spinal cord.] 
 
 [The cilia are flattened, blade-like or hair-like appendages attached to the free end of the cells. 
 They are about ^Vo' inch in length, and are, apparently, homogeneous and structureless. They 
 are planted upon a clear, non- contractile disk on the free end of the cell, and some observers state 
 that they pass through this disk to become continuous with the protoplasm of the cell, or with the 
 plexus of fibrils which pervades the protoplasm ; so that by some observers {Klein) they are regarded 
 as prolongations of the intraepithelial plexus of fibrils. They are specially modified parts of an 
 epithelial cell, and are contractile and elastic. They are colorless, tolerably strong, not colored by 
 staining reagents, and are possessed of considerable rigidity and flexibility. They are always con- 
 nected with the protoplasm of cells, and are never outgrowths of the solid cell membranes. There 
 may be 10 to 20 cilia distributed uniformly on the free surface of a cell (Fig. 280).] 
 
 [In the large ciliated cells in the intestine of some molluscs (mussel) the cilia perforate the clear 
 refractile disk, which appears to consist of small globules — basal pieces — united by their edge, so 
 that a cilium seems to spring from each of these, while continued downward into the protoplasm 
 of the cell, but not attached to the nucleus, there is a single varicose fibril — rootlet, and the leash 
 of these fibrils passes through the substance of the cell, and may unite toward its lower-tailed 
 extremity (Engelmann).~\ 
 
 [Ciliary motion may be studied in the gill of a mussel, a small part of the gill being teased in 
 
 491 
 
492 FUNCTIONS OF CILIA. 
 
 sea water ; or the hard palate of a frog, newly killed, may be scraped, and the scraping examined 
 in i£ p. c. salt solution. On analyzing the movement, all the cilia will be observed to execute a 
 regular, periodic, to-and-fro rhythmical movement in a plane usually vertical to the surface of the 
 cells, the direction of the movement being parallel to the long axis of the organ. The appearance 
 presented by the movements of the cilia is sometimes described as a lashing movement, or like a 
 field of corn moved by the wind. Each vibration of a cilium consists of a rapid forward move- 
 ment or flexion, the tip moving more than the base, and a slower backward movement, the cilium 
 again straightening itself. The forward movement is about twice as rapid as the backward move- 
 ment. The amplitude of the movement varies according to the kind of cell and other conditions, 
 being less when the cells are about to die ; but it is the same for all the cilia attached to one cell, 
 and is seldom more than 20 to 50°. There is a certain periodicity in their movement ; in the 
 frog they contract about 12 times per second (Engelmann). The result of the rapid forward 
 movement is that the surrounding fluid, and any particles it may contain, are moved in the direction 
 in which the cilia bend. All the cilia of adjoining cells do not move at once, but in regular suc- 
 cession, the movement traveling from one cell to the other; but how this coordination is brought 
 about we do not know. At least, it is quite independent of the nervous system, as ciliary move- 
 ment goes on in isolated cells, and in man it has been observed in the trachea two days after death. 
 Conditions for Movement. — In order that the ciliary movement may go on, it is essential that 
 — (1) the cilia be connected with part of a cell ; (2) moisture ; (3) oxygen be present ; and (4) the 
 temperature is within certain limits.] 
 
 [A ciliated epithelial cell is a good example of the physiological division of labor. It is 
 derived from a cell which originally held motor, automatic and nutritive functions all combined in 
 one mass of protoplasm ; but in the fully-developed cell the nutritive and regulative functions are 
 confined to the protoplasm, while the cilia alone are contractile. If the cilia be separated from the 
 cell, they no longer move. If, however, a cell be divided so that part of it remains attached to the 
 cilia, the latter still move. The nucleus is not essential for this act. It would seem, therefore, 
 that though the cilia are contractile, the motor impulse probably proceeds from the cell. Each 
 cell can regulate its own nutrition, for during life they resist the entrance of certain colored 
 fluids.] 
 
 [Effect of Reagents. — Gentle heat accelerates the number and intensity of the movements, 
 cold retards them. A temperature of 45 C. causes coagulation of their proteids, makes them 
 permanently rigid, and kills them, just in the same way as it acts on muscle, causing heat stiffening 
 (P- 5°5)- Weak alkalies may cause them to contract after their movement is arrested or nearly so 
 ( Virchow), and any current of fluid, in fact, may do so. Lister showed that the vapor of ether 
 and chloroform arrests the movements as long as the narcosis lasts, but if the vapor be not applied 
 for too long a time, the cilia may begin to move again. The prolonged action of the vapor kills 
 them. As yet, we do not know any specific poison for cilia, atropin, veratrin and curara acting 
 like other substances with the same endosmotic equivalent [Engelmann).'] 
 
 [Functions of Cilia. — The moving cilia propel fluids or particles along the 
 passages which they line. By carrying secretions along the tubes which they line 
 toward where these tubes open on the surface, they aid in excretion. In the 
 respiratory passages, they carry outward along the bronchi and trachea the mucus 
 formed by the mucous glands in these regions. When the mucus reaches the 
 larynx it. is either swallowed or coughed up. That the cilia carry particles upward 
 in a spiral direction in the trachea has been proved by actual laryngoscopic inves- 
 tigation, and also by excising a trachea and sprinkling a colored powder on its 
 mucous membrane, when the colored particles (Berlin blue or charcoal) are slowly 
 carried toward the upper end of the trachea. In bronchitis, the ciliated epi- 
 thelium is shed, and hence the mucus tends to accumulate in the bronchi. They 
 remove mucus from cavities accessory to the nose, and from the tympanum, while 
 the ova are carried, partly by their agency, from the ovary along the Fallopian 
 tube to the uterus. In some of the lower animals they act as organs of locomo- 
 tion, and in others as adjuvants to respiration, by creating currents of water in 
 the region of the organs of respiration.] 
 
 [The Force of Ciliary Movement. — Wyman and Bowditch found that the amount of work 
 that can be done by cilia is very considerable. The work was estimated by the weighty which a 
 measured surface of the mucous membrane of the frog's hard palate was able to carry up an 
 inclined plane of a definite slope in a given time.] 
 
 [Pigment cells belong to the group of contractile tissues, and are well developed in the frog, 
 and many other animals where their characters have been carefully studied. They are generally 
 regarded as comparable to branched connective^tissue corpuscles, loaded with pigmented 
 granules of melanin. The pigment granules may be diffused in the cell, or aggregated around 
 
STRUCTURE AND ARRANGEMENT OF THE MUSCLES. 493 
 
 the nucleus; in the former case, the skin of the frog appears dark in color, in the latter, it 
 is but slightly pigmented. The question has been raised whether they are actual cells or merely 
 spaces, branched, and containing a fluid with granules in suspension. In any case, they undergo 
 marked changes of shape under various influences. If the motor nerve to one leg of a frog be 
 divided, the skin of the leg on that side becomes gradually darker in color than the intact leg. A 
 similar result is seen in the curara experiment, when all parts are ligatured except the nerve. 
 Local applications affect the state of diffusion of the pigment, as v. Wittich found that turpentine 
 or electricity caused the cells of the tree-frog to contract, and the same effect is produced by light. 
 In Rana temporaria local irritation has little effect, but light, on the contrary, has, although the 
 effect of light seems to be brought about through the eye (Lister), probably by a reflex mechanism. 
 A pale colored frog, put in a dark place, assumes, after a time, a different color, as the pigment is 
 diffused in the dark ; but if it be exposed to a bright light it soon becomes pale again. The same 
 phenomenon may be seen on studying the web of a frog's leg under the microscope. The marked 
 variations of color — within a certain range — in the chameleon is due to the condition of the pig- 
 ment cells in its skin, covered as they are by epidermis, containing a thin stratum of air (Brucke). 
 When it is poisoned with strychnin, its whole body turns pale ; if it be ill, its body becomes spotted 
 in a dendritic fashion, and if its cutaneous nerves be divided, the area supplied by the nerve changes 
 to black. The condition of its skin, therefore, is readily affected by the condition of its nervous 
 system, for psychical excitement also alters its color. If the sympathetic nerve in the neck of a 
 turbot be divided, the skin on the dorsal part of the head becomes black. It is notorious that the 
 color of fishes is adapted to the color of their environment. If the nerve proceeding from the stellate 
 ganglion in the mantle of a cuttle fish be divided, the skin on one-half of the body becomes pale.] 
 
 292 a. STRUCTURE AND ARRANGEMENT OF THE MUS- 
 CLES. — Muscular Tissue is endowed with contractility, so that when it is 
 acted upon by certain forms of energy or stimuli, it contracts. There are two 
 varieties of this tissue — 
 
 (1) Striped, striated or (voluntary) ; 
 
 (2) Non-striped, smooth, organic, or (involuntary). 
 
 Some muscles are completely under the control of the will, and are hence called 
 " voluntary," and others are not directly subject to the control of the will, and 
 are hence called "involuntary;" the former are for the most part striped, and the 
 latter non-striped ; but the heart muscle, although striped, is an involuntary muscle. 
 
 I. Striped Muscles. — The surface of a muscle is covered with a connective-tissue envelope or 
 perimysium externum, from which septa, carrying blood vessels and nerves, the perimysium 
 internum, pass into the substance of the muscle, so as to divide it into bundles of fibres or fasci- 
 culi, which are fine in the eye muscles and coarse in the glutei. In each such compartment or 
 mesh there lie a number of muscular fibres arranged more or less parallel to each other. [The 
 fibres are held together by delicate connective tissue or endomesium, which surrounds groups of 
 the fibres ; each fibre being, as it were, separated from its neighbor by excessively delicate fibrillar 
 connective tissue.] Each muscular fibre is surrounded with a rich plexus of capillaries [which 
 form an elongated meshwork, lying between adjacent fibres, but never penetrating the fibres, which, 
 however, they cross (Fig. 284). In a contracted muscle the capillaries may be slightly sinuous in 
 their course, but when a muscle is on the stretch these curves disappear. The capillaries lie in the 
 endomysium, and near them are lymphatics.] Each muscular fibre receives a nerve fibre. [Where 
 found.— Striped muscular fibres occur in the skeletal muscles, heart, diaphragm, pharynx, upper 
 part of oesophagus, muscles of the middle ear and pinna, the true sphincter of the urethra, and 
 external anal sphincter.] 
 
 A muscular fibre (Fig. 281, 1) is a more or less cylindrical or polygonal 
 fibre, 11 to 67 [x [j-J-jt to ^-J^ in.] in diameter, and never longer than 3 to 4 centi- 
 metres [1 to i}i in. J. Within short muscles, e.g., stapedius, tensor tympani, 
 or the short muscles of a frog, the fibres are as long as the muscle itself ; within 
 longer muscles, however, the individual fibres are pointed, and are united obliquely 
 by cement substance with a similar beveled or pointed end of another fibre lying 
 in the same direction. Muscular fibres may be isolated by maceration in nitric 
 acid with excess of potassic chlorate (Budge), or by a 35 per cent, solution of 
 caustic potash (Moleschott). 
 
 [Each muscular fibre consists of the following parts : — 
 
 1. Sarcolemma, an elastic sheath, with transverse partitions, stretching 
 across the fibre at regular intervals — the membranes of Krause ; 
 
 2. The included sarcous substance; 
 
 3. The nuclei or muscle corpuscles.] 
 
494 
 
 STRUCTURE OF STRIPED MUSCLES. 
 
 Sarcolemma. — Each muscular fibre is completely enclosed by a colorless, structureless, trans- 
 parent elastic sheath (Fig. 281, 1, S), which, chemically, is midway between connective and elastic 
 tissue, and within it is the contractile substance of the muscle. [It has much more cohesion than 
 the sarcous substance which it encloses, so that sometimes, when teasing fresh muscular tissue under 
 the microscope, one may observe the sarcous substance torn across, with the unruptured sarcolemma 
 stretching between the ends of the ruptured sarcous substance. If muscular fibres be teased in 
 distilled water, sometimes fine, clear blebs are' seen along the course of the fibre, due to the sarco- 
 lemma being raised by the fluid diffusing under it. The sarcous substance, but not the sarcolemma, 
 may be torn across by plunging a muscle in water at 55 C, and keeping it there for some time 
 {Ranvier).~\ 
 
 Fig. 281. 
 
 Histology of muscular tissue. 1, Diagram of part of a striped muscular fibre ; S, sarcolemma ; Q, transverse stripes ; 
 F, nbrillae ; K, the muscle nuclei; N, a nerve fibre entering it with a, its axis cylinder and Kuhne's motorial end 
 plate, e, seen in profile; 2, transverse section of part of a muscular fibre, showing Cohnheim's areas, c; 3, isolated 
 muscular fibrillar ; 4, part of an insect's muscle greatly magnified : a, Krause-Amici's line limiting the muscular 
 cases ; b, the doubly-refractive substance ; c t Hensen's disk ; d, the singly-refractive substance ; 5, fibre cleaving 
 transversely into disks ; 6, muscular fibre from the heart of a frog ; 7, development of a striped muscle from a 
 human foetus at the third month ; 8, g, muscular fibres of the heart ; c, capillaries ; b, connective-tissue cor- 
 puscles ; io, smooth muscular fibres > 11, transverse section of smooth muscular fibres. 
 
 Stripes. — The sarcous substance is marked transversely by alternate light 
 and dim layers, bands, stripes or disks (Fig. 281, 1, Q), so that each fibre 
 is said to be "transversely striped." [The stripes do not occur in the 
 sarcolemma, but are confined to the sarcous substance, and they involve its 
 whole thickness.] 
 
 [The animals most suited for studying the structure of the sarcous substance are some of the 
 insects. The muscles of the water beetle, Dytiscus marginalis, and the Hydrophilus piceus are well 
 suited for this purpose. So is the crab's muscle. In examining a living muscle microscopically, 
 no fluid except the muscle juice should be added to the preparation, and very high powers of the 
 microscope are required to make out the finer details.] 
 
STRUCTURE OF A MUSCULAR FIBRILLA. 
 
 495 
 
 Fig. 282. 
 
 Portion of a human muscular fibre, 
 X3°°- 
 
 Bowman's Disks. — If a muscular fibre be subjected to the action of hydro- 
 chloric acid (1 per 1000), or if it be digested by 
 gastric juice, or if it be frozen, it tends to cleave 
 transversely into disks {Bowman), which are arti- 
 ficial products, and resemble a pile of coins which 
 has been knocked over (Fig. 281, 5). 
 
 Fibrillar. — Under certain circumstances, a fibre 
 may exhibit longitudinal striation. This is due to 
 the fact that it may be split up longitudinally into 
 an immense number of (1 to 1.7 y. in diameter) 
 fine, contractile, threads, the' primitive fibrillae 
 (Fig. 281, 1, F), placed side by side, each of which 
 is also transversely striped, and they are so united 
 to each other by semi-fluid cement substance, that 
 the transverse- markings of all the fibrillae lie at the 
 same level. These fibrillae, owing to mutual pres- 
 sure, are prismatic in form, so that when a trans- 
 verse section of a perfectly fresh muscular fibre is 
 observed after it is frozen, the end of each fibre is 
 mapped out into a number of small polygonal areas 
 called Cohnheim's areas (Fig. 281, 2). 
 
 Fibrillar are easily obtained from insects' mus- 
 cles, while those from a mammal's muscle are readily 
 isolated by the action of dilute alcohol, Miiller's 
 fluid [or, best of all, \ per cent, solution of chro- 
 mic acid] (Fig. 281, 3). 
 
 [When a living, unaltered muscular fibre is examined microscopically, in its 
 own juice, we observe the alternate dim and light transverse disks. A high power 
 reveals the presence of a line running across the light disk, and dividing it into 
 two (Fig. 282). It has been called Dobie's line {Rutherford), and by others it is 
 regarded as due to the existence of a membrane, called Krause's membrane, 
 which runs transversely across the fibre, being attached all round to the sarco- 
 lemma, thus dividing each fibre into a series of compartments placed end to end. 
 
 These muscular compartments contain the sarcous substance, and in each 
 compartment we find (1) a broad, dim disk, which is the contractile part of the 
 sarcous substance. It is doubly refractive (anisotropous), and is composed of 
 Bowman's sarcous elements. (2) On each end of this disk, and between it and 
 Krause's membranes, is a narrower, clear, homogeneous, and but singly refractile 
 (isotropous), soft or fluid substance, which forms the lateral disk of Engel- 
 mann. In some insects it contains a row of refractive granules, constituting the 
 granular layer of Flogel. If a muscular fibre be stretched and stained with 
 logwood, the central part of the dim disk appears lighter in color than the two 
 ends of the same disk. This has been described as a separate disk, and is called 
 the median disk of Hensen (Fig. 281, 4, c).~\ 
 
 [In an unaltered fibre, the dim, broad stripe appears homogeneous, but after a 
 time it cleaves throughout its entire extent in the long axis of the fibre into a 
 number of prismatic elements or fibrils, the sarcous elements of Bowman 
 (Fig. 281). These at first are prismatic, but as they solidify they shrink and 
 seem to squeeze out of them a fluid, becoming at the same time more constricted in 
 the centre. This separation into fibrils with an interstitial matter gives rise to the 
 appearance seen on transverse section of a frozen muscle, and known as Cohn- 
 heim's areas (Fig. 281, 2, c). In all probability the cleavage also extends through 
 the lateral disks, and thus fibrils are formed by longitudinal cleavage of the fibre.] 
 
 [According to Haycraft, a muscular fibre is moniliform, being narrowest at the part opposite 
 Krause's membrane, and thicker in the interval, so that Haycraft attributes the transverse striation 
 to these differences, the surface being undulating.] 
 
496 
 
 MUSCLE RODS. 
 
 [Muscle Rods. — Sch&fer describes the appearance differently: " Double rows of granules are 
 seen lying in or at the boundaries of the light streaks (disks), and very fine, longitudinal lines may 
 be detected running through the dark streak (dim disk) and uniting the minute granules. These 
 fine lines, with their enlarged extremities, are muscle rods." They are most conspicuous in in- 
 sects. During the contraction of a living muscular fibre, Schafer describes the " reversal of the 
 stripes" (§ 297) as follows: "When the fibres contract the light stripes are seen, as the fibre 
 shortens and thickens, to become dark, an apparent reversal being thereby produced in the striae. 
 This reversal is due to the enlargement of the rows of dark dots and the formation by their juxta- 
 position and blending of dark disks, while the muscular substance between these disks has by con- 
 trast a bright appearance."] 
 
 [With polarized light in a living muscular fibre, all the sarcous substance, except the muscle 
 rod, is doubly refractive or anisotropous, so that it appears bright on a dark field when the Nicol's 
 prisms are crossed, while under the same conditions contracted muscle and dead muscle show 
 alternate dark and light bands (Scia/er).] 
 
 The nuclei or muscle corpuscles are found immediately under the sarcolemma in all mammals, 
 and their long axis lies in the long axis of the fibre (8 to 13 V- long, 3 to 4 A* broad). [In the mus- 
 cles of the frog and some other animals, e.g., the red muscles of the rabbit and hare, they lie in the 
 
 Relation of a tendon, S, to its 
 muscular fibre. 
 
 Injected blood vessels of a human muscle, a, small artery ; /', 
 vein ; c, capillaries. X 250 (Kolliker). 
 
 substance of the fibre surrounded by a small amount of protoplasm.] When they occur immediately 
 under the sarcolemma they are more or less flattened, and lie embedded in a small amount of pro- 
 toplasm (Fig. 281, I and 2, K). They contain one or two nucleoli, and it is said that the proto- 
 plasm sends out fine processes which unite with similar processes from adjoining corpuscles, so that, 
 according to this view, a branched protoplasmic network exists under the sarcolemma. [Each 
 nucleus has a reticulated appearance due to the presence of a plexus of fibrils. The nuclei are not 
 seen in a perfectly fresh muscle, because, until they have undergone some change, their refractive 
 index is the same as that of the sarcous substance.] They become specially evident after the addi- 
 tion of acetic acid. Histogenetically, they are the remainder of the cells from which the muscular 
 fibres were developed (Fig. 281, 7). According to M. Schultze, the sarcous substance is an inter- 
 cellular substance differentiated and formed by their activity. Perhaps they are the centres of nutri- 
 tion for the muscular fibres. In amphibians, birds, fishes, and reptiles, they lie in the axis of the 
 fibres between the fibrils. 
 
 It is said that the protoplasm of the muscle corpuscles forms a fine network throughout the whole 
 muscular fibre, the transverse branches taking the course of the lines of Krause or Dobie, and the 
 longitudinal branches running in the interstices between Cohnheim's areas (Jtetzius, Bremer). 
 
NERVES OF A MUSCLE. 497 
 
 Relation to Tendons. — According to Toldt, the delicate connective-tissue elements, which 
 cover the several muscular fibres, pass from the ends of the latter directly into the connective -tissue 
 elements of the tendon. The end of the muscular fibre is perhaps united to the smooth surface or 
 hollow end of the tendon by means of a special cement ( Weismann — Fig. 283, S). In arthropoda, 
 the sarcolemma passes directly into and becomes continuous with the tendon (Leydig, Reichert). 
 The tendon itself consists of longitudinally arranged bundles of white fibrous tissue with cells — 
 tendon cells — embracing them. There is a loose capsule or sheath of connective tissue — the peri- 
 tendineum of Kollman — surrounding the whole and carrying the blood vessels, lymphatics, and 
 nerves. The tendons move in the tendon sheaths, which are moistened by a mucous fluid. In 
 most situations, muscular fibres are attached by means of tendons to some fixed point, but in other 
 situations (face) the ends terminate between the connective-tissue elements of the skin. 
 
 [Blood Vessels. — Muscles, being very active organs, are richly supplied with blood. The 
 blood supply of a muscle differs from some organs in not constituting an actual vascular unit, sup- 
 plied only by one artery and one vein, thus being unlike the kidney, spleen, etc. Each muscle 
 usually receives several branches from different arteries, and branches enter it at certain distances 
 along its whole length. The artery and vein usually lie together in the connective tissue of the 
 perimysium, while the capillaries lie in the endomysium. The capillaries lie between the muscular 
 fibres, but outside the sarcolemma, where they form an elongated, rich plexus with numerous 
 transverse branches (Fig. 284). The lymph to nourish the sarcous substance must traverse the 
 sarcolemma to reach the former. In the red muscles of the rabbit (e.g., semitendinosus), the 
 capillaries are more wavy, while on the transverse branches of some of the capillaries, and on the 
 veins (Ranvier), there are small, oval, saccular dilatations, which act as reservoirs for blood.] 
 
 [Lymphatics. — We know very little of the lymphatics of muscle, although the lymphatics of 
 
 Fig. 285. 
 
 mm- 
 
 End plate. 
 
 I 
 
 Muscle nucleus. 
 
 Muscular fibres with motorial end plates. 
 
 tendon and fascia have been carefully studied by Ludwig and Schweigger-Seidel. There are lym- 
 phatics in the endomysium of the heart, which are continuous with those under the pericardium. 
 This subject still requires further investigation. Compare the lymphatics of the fascia lata of the 
 dog (Fig. 212, (I 201).] 
 
 Entrance of the Nerve. — The trunk of the motor nerve, as a rule, enters the muscle at its 
 geometrical centre (Schwalbe) ; hence the point of entrance in muscles with lonjr, parallel, or spindle- 
 shaped fibres lies near its middle. If the muscle with parallel fibres is more than 2 to 3 centimetres 
 [1 inch] in length, several branches enter its middle. In triangular muscles, the point of entrance of 
 the nerve is displaced more toward the strong tendinous point of convergence of the muscular 
 fibres. A nerve fibre usually enters a muscle at the point where there is the least displacement of 
 the muscular substance during contraction. 
 
 Motor Nerve. — Every muscular fibre receives a motor nerve fibre (Fig. 281, 
 1, N). Each nerve does not contain originally as many motor nerve fibres as there 
 are muscular fibres in the muscle it enters ; in the human eye muscles, there are 
 only 3 nerve fibres to 7 muscular fibres ; in other muscles (dog), 1 nerve fibre to 
 40 or 80 ( Tergast ). Hence, when a nerve enters a muscle it must divide, which 
 occurs dichotomously [at Ranvier's nodes], the structure undergoing no change 
 until there are exactly as many nerve fibres as muscular fibres. In warm-blooded 
 animals each muscular fibre has only one, while cold-blooded animals have seve- 
 ral points of insertion of the nerve fibre (Sandmanri). A nerve fibre enters each 
 3 2 
 
498 
 
 RED AND PALE MUSCLES. 
 
 muscular fibre, and where it enters it forms an eminence {Doyere, 2840), the 
 " motorial end plate " (Fig. 281, 1, e). The neurilemma unites directly with 
 the sarcolemma, the white substance of Schwann ceases, while the axis cylinder 
 passes in and divides within the sarcolemma. There is an elevation of a proto- 
 plasmic nature containing nuclei immediately under the sarcolemma at the entrance 
 of the nerve (Kiihne's end plate, Fig. 285). The branches of the axis cylinder 
 traverse this mass, where they subdivide into fine fibrils recognizable only after 
 the action of gold chloride (Fig. 286). These fibrils penetrate between the fibril- 
 lse along the whole extent of the fibre, and, perhaps, they terminate in the aniso- 
 tropous substance (Gerlacfi). 
 
 Sensory fibres also occur in muscles, and they are the channels for muscular 
 sensibility. They seem to be distributed on the outer surface of the sarcolemma, 
 where they form a branched plexus and wind round the muscular fibres (Arndt, 
 Sachs) ; but, according to Tschirjew, the sensory nerves traverse the substance of 
 the muscle, and after dividing dichotomously, end only in the aponeurosis, either 
 suddenly or by means of a small swelling — a view confirmed by Rauber. The 
 existence of sensory nerves in muscles is also proved by the fact that, stimulation 
 of the central end of a motor nerve, e. g., the phrenic, causes increase of the 
 blood pressure and dilatation of the pupil {Asp, Kowalewsky, Nawrocki'), as well 
 as by the fact that when they are inflamed they are painful. They, of course, do 
 not degenerate after section of the anterior root of the spinal nerves. 
 
 Red and Pale Muscles. — In many fishes (skate, plaice, herring, mackerel) ( IV. Stirling), birds, 
 
 Fig. 286. 
 
 Intra-fibrillar terminations of a motor nerve in striped muscle stained with gold chloride 
 
 and mammals (rabbits), there are two kinds of striped muscle (R~rause,), differing in color, histo- 
 logical structure [Ranvier) and physiological properties [Kronecker and Stirling). Some are 
 " red," e.g., the soleus and semitendinosus of the rabbit, and others "pale," e.g., the adductor 
 magnus. In the pale muscles the transverse striation is less regular, and their nuclei fewer than in 
 . the red muscles [Ranvier) ; they contain less glycogen and myosin. [W. Stirling finds that the red 
 muscles in many fishes, e. g., the mackerel, contain granules of oil, and present all the appearances of 
 muscle in a state of fatty degeneration, while the pale muscles, lying side by side, contain no fatty 
 granules.] 
 
 [Spectrum. — The red color of the ordinary skeletal muscle is due to haemoglobin in the sarcous 
 substance [Kiihne). This is proved by the fact that the color is retained when all the blood is 
 washed out of the vessels, when a thin muscle still shows the absorption bands of haemoglobin when 
 examined with the spectroscope.] 
 
 [Myo-haematin. — MacMunn points out that, although most voluntary muscles owe their color to 
 haemoglobin, it is accompanied by myo-hcematin in most cases, and sometimes entirely replaced by 
 it. Myo-haematin is found in the heart of vertebrates, and in some muscles of vertebrates and inver- 
 tebrates.] 
 
 Muscular Fibres of the Heart. — The mammalian cardiac muscle has certain peculiarities 
 already mentioned [\ 43) : (1) It is striped, but it is involuntary; (2) it has no sarcolemma; (3) its 
 fibres branch and anastomose ; (4) the transverse striation is not so distinct, and it is sometimes 
 striated longitudinally; (5) the nucleus is placed in the centre of each cell (see \ 43). [The cardiac 
 muscle, viewed from a physiological point of view, stands midway between striped and unstriped 
 muscle. Its contraction occurs slowly and lasts for a long time (p. 104), while, although it is trans- 
 versely striped, it is involuntary.] 
 
 [Purkinje's Fibres. — These fibres, which form a plexus of grayish fibres under the endocardium 
 of the heart of ruminants, have been described already (Fig. 28); the cells have, as it were, advanced 
 only to a certain stage of development ({I 46).] 
 
NON-STRIPED MUSCLE. 
 
 499 
 
 Development. — Each muscular fibre is developed from a uninucleated cell of the mesoblast, 
 which elongates into the form of a spindle. As the cell elongates, the nuclei multiply. The super- 
 ficial or parietal part of the cell substance shows transverse markings (Fig. 281, 7), while the nuclei 
 with a small amount of protoplasm are continuous along the axis of the fibre, where they remain in 
 some animals. Young muscles have fewer fibres than those of adults, and the former are also 
 smaller (Budge). 
 
 In developing muscles, the number of fibres is increased by the proliferation of the muscle 
 corpuscles, which form new fibres. Striped muscle, besides occurring in the corresponding organs 
 of vertebrata, occurs in the iris and choroid of birds. The arthropoda have only striped muscle, 
 the molluscs, worms, and echinoderms chiefly smooth muscles; in the latter, there are muscles with 
 double oblique striation (Schwalbe). 
 
 a. Non-Striped Muscle. — [Distribution. — It occurs very widely distributed in the body, in 
 the muscular coat of the lower half of the human oesophagus, stomach, small and large intestine, 
 muscularis mucosae of the intestinal tract, in the arteries, veins and lymphatics, posterior part of 
 the trachea, bronchi, infundibula of the lung, muscular coat of the ureter, bladder, urethra, vas 
 deferens, ves'culse seminalis, and prostate ; corpora cavernosa and spongiosa penis, ovary, Fallopian 
 tube, uterus, skin, ciliary muscle, iris, upper eyelid, spleen and capsule of lymphatic glands, tunica 
 dartos of the scrotum, gall bladder, in ducts of glands, and in some other situations.] 
 
 Structure Smooth muscular fibres consist of fusiform or spindle shaped elongated cells, with 
 
 their ends either tapering to fine points or divided (Fig. 281, 10). These contractile fibre cells may 
 
 Fig. 287. 
 
 Fig. 288. 
 
 Smooth muscular fibre from the mesen- 
 tery of a newt (ammonium chro- 
 mate). N, nucleus; F, fibrils; S, 
 markings in the sheath. 
 
 Termination of nerve in non-striped 
 muscle. 
 
 be isolated by steeping a piece of the tissue in a 30 per cent, solution of caustic potash, or a strong 
 solution of nitric acid. They are 45 to 230 [i [^-g to T ^ T in.] in length, and 4 to 10 /J- [^^^ to 
 ista m m breadth. Each cell contains a solid, oval, elongated nucleus, which may contain one 
 or more nucleoli. It is brought into view by the action of dilute acetic acid, or by staining reagents. 
 The mass of the cell appears more or less homogeneous [and is surrounded by a thin elastic envel- 
 ope]. In some places it shows longitudinal fibrillation. [Method. — This fibrillation is revealed 
 more distinctly thus : Place the mesentery of a newt (Klein) or the bladder of the salamandra 
 musculata (Hemming) in a 5 per cent, solution of ammonium chromate, and afterward stain it with 
 picrocarmine. Each cell consists of a thin elastic sheath (sarcolemma of Krause) enclosing a 
 bundle of fibrils (F), which run in a longitudinal direction within the fibre (Fig. 287). They are 
 continuous at the poles of the nucleus with the plexus of fibrils which lies within the nucleus, and, 
 according to Klein, they are the contractile part, and when they contract, the sheath becomes 
 shriveled transversely and exhibits what looks like thickenings (S). These fibrils have been observed 
 by Flemming in the cells while living. Sometimes the cells are branched, while in the frog's bladder 
 they are triradiate.] 
 
 [Arrangement. — Sometimes the fibres occur singly, but usually they are arranged in groups, 
 forming lamella', sheets, or bundles, or in a plexiform manner, the bundles being surrounded by 
 connective tissue.] A very delicate elastic cement substance unites the individual cells to each 
 other. [This cement may be demonstrated by the action of nitrate of silver. In transverse section 
 
500 PHYSICAL AND CHEMICAL PROPERTIES OF MUSCLE. 
 
 (Fig. 281, 11) they appear oval or polygonal, with the delicate homogeneous cement between them; 
 but, as the fibres are cut at various levels, the areas are unequal in size, and all of them, of course, 
 are not divided at the position of the nucleus.] 
 
 They vary in length from yj^ to jj,; of an inch; those in the blood vessels are short, while they 
 are long in the intestinal tract, and especially in the pregnant uterus. According to Engelmann; 
 the separation of the smooth muscular substance into its individual spindle-like elements is a post- 
 mortem change of the tissue. Sometimes transverse thickenings are seen, which are not due to 
 transverse striation {Krause), but to a partial contraction (Meissner). 
 
 Blood Vessels. — Occasionally they have a tendinous insertion. Non-striped muscle is richly 
 supplied with blood vessels, and the capillaries form elongated meshes between the fibres [although 
 it is not so vascular as striped muscles]. Lymphatics also occur between the fibres. 
 
 Motor Nerves. — According to J. Arnold, they consist of medullated and non-medullated fibres 
 [derived from the sympathetic system] which form a plexus — ground plexus — partly provided 
 with ganglionic cells, and lying in the connective tissue of the perimysium. [The fibres are sur- 
 rounded with an endothelial sheath.] Small branches [composed of bundles of fibrils] are given 
 off from this plexus, forming the intermediary plexus with angular nuclei at the nodal points. It 
 lies either immediately upon the musculature or in the connective tissue between the individual 
 bundles. From the intermediary plexus, the finest fibrillar (0.3 to 0.5 fi) pass oft" either singly or in 
 groups, and reunite to form the intermuscular plexus (Fig. 288, d), which lies in the cement 
 substance between the muscle cells, to end, according to Frankenhauser, in the nucleoli of the 
 nucleus, or in the neighborhood of the nucleus [Lustig). According to J. Arnold, the fibrils traverse 
 the fibre and the nucleus, so that the fibres appear to be strung upon a fibril passing through their 
 nuclei. According to Lowit, the fibrils reach only the interstitial substance, while Gscheidlen also 
 observed that the finest terminal fibrils, one of which goes to each muscular fibre, ran along the 
 margins of the latter (Fig. 288). The course of these fibrils can only be traced after the action of 
 gold chloride. [Ranvier has traced their terminations in the stomach of the leech.] 
 
 Nerves of Tendon. — Within the tendons of the frog there is a plexus of medullated nerve 
 fibres, from which brush-like divided fibres proceed, which ultimately end with a point in nucleated 
 plates, the nerve flakes of Rollett. According to Sachs, bodies like end bulbs occur in tendons, 
 while Rauber found Vater's corpuscles in their sheaths; Golgi found, in addition, spindle-shaped 
 terminal corpuscles, which he regards as a specific apparatus for estimating tension. 
 
 293. PHYSICAL AND CHEMICAL PROPERTIES OF MUS- 
 CLE. — 1. The consistence of the sarcous substance is the same as that of living 
 protoplasm, e. g., of lymph cells; it is semi-solid, i. e., it is not fluid to such a 
 degree as to flow like a fluid, nor is it so solid that, when its parts are separated, 
 these parts are unable to come together to form a continuous whole. The consis- 
 tence may be compared to a jelly at the moment when it is dissolved (e. g., by 
 heat). The power of imbibition is increased in a contracted muscle (Jianke). 
 
 Proofs. — The following facts corroborate the view expressed above : (a) The analogy between 
 the function of the sarcous substance and the contractile protoplasm of cells ((! 9). (/>) The so- 
 called Porret's phenomenon ( IV. Kiihne) which consists in this, that when a galvanic current is 
 conducted through the living, fresh, sarcous substance, the contents of the muscular fibre exhibit a 
 streaming movement from the positive to the negative pole (as in all other fluids), so that the fibre 
 swells at the negative pole. (<r) By the fact that wave movements have been observed to pass along the 
 muscular fibre, (d) Direct observation has shown that a small parasitic round worm (Myoryctes 
 Weismanni) moved freely in the sarcous substance within the sarcolemma, while the semi-solid mass 
 closed up in the track behind it ( W. Kiihne, Eberth). 
 
 z. Polarized Light. — The contractile substance doubly refracts light, and is said to be aniso- 
 tropous, while the ground substance causes single refraction, and is isotropous. According to 
 Briicke, muscle behaves like a doubly-refractive, positively uniaxial body, whose optical axis lies in 
 the long axis of the fibre. When a muscular fibre is examined under the polarization microscope, 
 the doubly-refractive substance is recognized by its appearing bright in the dark field of the micro- 
 scope when the Nicols are crossed (g 297). During contraction of the muscular fibre, the contrac- 
 tile part of the fibre becomes narrower, and at the same time broader, whilst the optical constants 
 do not thereby undergo any change. Hence, Briicke concludes that the contractile disks are not 
 simple bodies like crystals, but must consist of a whole series of small, doubly-refractive elements 
 arranged in groups, which change their position during contraction and relaxation. These small 
 elements Briicke called disdiaclasts. According to Schipiloff, Danielewsky, and O. Nasse, the 
 contractile anisotropous substance consists of myosin, which occurs in a crystalline condition, and 
 represents the disdiaclasts. According to Engelmann, however, all contractile elements are doubly 
 refractive, and the direction of contraction always coincides with the optical axis. 
 
 The investigations of v. Ebner have shown that during the process of growth of the tissue, ten- 
 sion is produced — the tension of bodies subjected to imbibition — which results in double refraction, 
 and so gives rise to the condition called anisoiropous. 
 
CHEMICAL COMPOSITION OF MUSCLE SERUM. 501 
 
 The chemical composition of muscle undergoes a great change after death, 
 owing to the spontaneous coagulation of a proteid within the muscular fibres. As 
 frog's muscles may be frozen and thawed, and still remain contractile, they cannot, 
 therefore, be greatly changed by the process of freezing. W. Kiihne bled frogs, 
 cooled their muscles to io° or 7 C, pounded them in an iced mortar, and ex- 
 pressed their juice through linen. The juice so expressed, when filtered in the 
 cold, forms a neutral, or alkaline, slightly yellowish, opalescent fluid, the so-called 
 "muscle plasma." Like blood plasma, it coagulates spontaneously; at first 
 it is like a uniform soft jelly, but soon becomes opaque ; doubly-refractive fibres 
 and specks, similar to the fibrin of blood, appear in the jelly, and as these begin 
 to contract, they squeeze out of the jelly an acid "muscle serum." Cold 
 prevents or delays the coagulation of the muscle plasma ; above 0°, coagulation 
 occurs very slowly, and the rapidity of coagulation increases rapidly as the tem- 
 perature rises, while coagulation takes place very rapidly at 40 C. in cold-blooded 
 animals, or at 48 to 50° C. in warm-blooded muscles. The addition of distilled 
 water or an acid to muscle plasma causes coagulation at once. The coagulated 
 proteid, most abundant in muscle, and which arises from the doubly-refractive 
 substance, is called "myosin " (W. Kiihne). 
 
 Myosin. — It is a globulin (§ 245), and is soluble in strong f 10 per cent.) solutions of common 
 salt, and is again precipitated from such a solution by dilution with water, or by the addition of very 
 small quantities of acids (0.1 to 0.2 percent, lactic or hydrochloric acid). It is soluble in dilute 
 alkalies or slightly stronger acids (0.5 percent, lactic or hydrochloric acid), and also in 13 per cent, 
 ammonium chloride solution. Like fibrin, myosin rapidly decomposes hydric peroxide. When 
 treated with dilute hydrochloric acid and heat, it is changed into syntonin ($ 245). Myosin may 
 be extracted from muscle by a 10 to 15 per cent, solution of NH 4 C1, and if it be heated to 65 it is 
 precipitated again (DanielewsAy). Danielewsky succeeded in partly changing syntonin into myosin 
 by the action of milk of lime and ammonium chloride. Myosin occurs in other animal structures 
 (cornea), nay, even in some vegetables [O. JVasse). 
 
 Muscle serum still contains three proteids (2.3 to 3 per cent.), viz.: 1. 
 Alkali albuminate, which is precipitated on adding an acid, even at 20 to 24 
 C. 2. Ordinary serum albumin, 1.4 to 1.7 per cent. (§ 32, a), which coagu- 
 lates at 73° C. 3. An albuminate which coagulates at 47° C. 
 
 The other chemical constituents of muscle have been referred to in treating of 
 flesh (§ 233 j. 1. Briicke found traces of pepsin and peptone in muscle juice; 
 Piotrowsky, a trace of a diastatic ferment. 2. In addition to volatile fatty acids 
 (formic, acetic, butyric), there are two isomeric forms of lactic acid (C 3 H 6 3 ) pre- 
 sent in muscle with an acid reaction : (a) Ethylidene-lactic acid, in the modifica- 
 tion known as right rotatory sarcolactic or paralactic acid, which occurs only in 
 muscles, and some other animal structures. (6) Ethylene-lactic acid in small 
 amount (§ 251, 3 c). It was formerly assumed that lactic acid is formed by fer- 
 mentation from the carbohydrates of the muscle (glycogen, dextrin, sugar), and 
 Maly has observed that paralactic acid is occasionally formed when these bodies 
 undergo fermentation. According to Bohm, however, the glycogen of muscle 
 does not pass into lactic acid, as during rigor mortis, if putrefaction be prevented, 
 the amount of glycogen does not diminish. If muscle be suddenly boiled or 
 treated with strong alcohol, the ferment is destroyed, and hence the acidification 
 of the muscular tissue is prevented (Du Bois-Reymond). Acid potassium phosphate 
 also contributes to the acid reaction. 3. Carnin (C,H 8 N 4 3 ), which is changed by 
 bromine or nitric acid into sarkin, occurs to the extent of 1 per cent, in Liebig's 
 extract of meat {Weidel). 4. Only 0.01 per cent, of urea (Haycraft). 5. Gly- 
 cogen occurs to the amount of over 1 per cent, after copious flesh feeding, and to 
 0.5 per cent, during fasting. It is stored up in the muscles, as well as in the liver, 
 during digestion, but it disappears during hunger. It is perhaps formed in the 
 muscles from proteids (§ 174, 2). 6. Lecithin, derived in part from the motor 
 nerve endings (§ 23 and § 251). 7. The gases are C0 2 (15 to 18 vol. per cent.), 
 partly absorbed, partly chemically united ; some absorbed N, but no O, although 
 
502 METABOLISM IN MUSCLE. 
 
 muscle continually absorbs O from the blood passing through it (Z. Hermann). 
 The muscles contain a substance whose decomposition yields C0 2 . When muscles 
 are exercised, this substance is used up, so that severely fatigued muscles yield less 
 C0 2 {Stinzing). [It is to be remembered that all muscles have not the same 
 chemical composition.] 
 
 294. METABOLISM IN MUSCLE. — I. A passive muscle continu- 
 ally absorbs a certain amount of O from the blood flowing through its capillaries, 
 and returns a certain amount of C0 2 to the blood stream. The amount of C0 2 
 given off is less than corresponds to the amount of O absorbed. Excised muscles 
 freed from blood exhibit an analogous but diminished gaseous exchange (Du 
 Bois-Reymond, G. Liebig). As an excised muscle remains longer excitable in O 
 or in air than in an atmosphere free from O, or in indifferent gases {Al. v. Hum- 
 boldt), we must conclude that the above-named gaseous exchange is connected 
 with the normal metabolism, and is a condition on which the life and activity of 
 the muscle depends. 
 
 If a living muscle be excised, and if blood be perfused through its blood vessels, the amount of 
 O used up is, within pretty wide limit's, almost independent of temperature ; if the variations of 
 temperature be great, it rises and falls with the temperature. The C0 2 given off by muscular tissue 
 falls when the muscle is cooled (less than the O used up), but it is not increased when the muscle 
 is subsequently warmed (Rubner). 
 
 This exchange of gases must be distinguished from the putrefactive phenomena due to the devel- 
 opment of living organisms in the muscle. These putrefactive phenomena are also connected with 
 the consumption of O and the excretion of C0 2 , and occurs soon after death (Z. Hermann). 
 
 II. In an active muscle the blood vessels are always dilated {Ludwig 
 and Sczelkow, Gaskell) — a condition pointing to a more lively material exchange 
 in the organ. Hence, the active muscle is distinguished from the passive one by 
 a series of chemical transformations. 
 
 1. Reaction. — The neutral or feebly alkaline reaction of a passive muscle 
 (also of the non-striped variety) passes into an acid reaction during the activity 
 of the muscle, owing to the formation of paralactic acid {Du Bois-Reymond, 
 z8jp) ; the degree of acidity increases up to a certain extent, according to the 
 amount of work performed by the muscle {R. Heidenhain). The acidification is 
 due, according to Weyl and Zeitler, to the phosphoric acid produced by the 
 decomposition of lecithin and (Pnuclein). 
 
 It is doubtful if the acidity is due to lactic acid, as Warren and Astaschewsky find that there is 
 less lactic acid in the active than in the passive muscle. 
 
 2. Production of CO z . — An active muscle excretes considerably more C0 2 
 than a passive one : (a) active muscular exertion on the part of a man or of ani- 
 mals increases the amount of C0 2 given off by the lungs (§127); {b) venous 
 blood flowing from a tetanized muscle of a limb contains more C0 2 , more C0 2 
 being formed than corresponds to the O, which has simultaneously been absorbed 
 {Ludwig and Sczelkow). The same result is obtained when blood is passed through 
 an excised muscle artificially ; (c) an excised muscle caused to contract excretes 
 more C0 2 {Matteucci, Valentin). 
 
 3. Consumption of Oxygen. — An active muscle uses up more O — (a) when 
 we do muscular work, the body absorbs much more O (p. 366) — even 4 to 5 times as 
 much {Regnault and Reiset ) ; (b) venous blood flowing from an active muscle of 
 a limb contains less O {Ludwig, Sczelkow and Al. Schmidt). Nevertheless, the 
 increase of O used up by the active muscle is not so great as the amount of C0 2 
 given off (v. Pettenkofer and v. Voif). The increase of O used up may be ascer- 
 tained even during the period of rest directly following the period of activity, 
 and the same is the case with the C0 2 excreted (v. Frey). 
 
 As yet, it is not possible to prove, by gasometric methods, that O is used 
 up in an excised muscle free from blood. Indeed, the presence of O does not 
 
METABOLISM IN MUSCLE. 
 
 503 
 
 seem to be absolutely necessary for the activity of muscle during short periods, as 
 an excised muscle may continue to contract in a vacuum, or in a mixture of gases 
 free from O, and no O can be obtained from muscular tissue (L. Hermann). A 
 frog's muscles rob easily reducible substances of their O ; they discharge the color 
 of a solution of indigo ; muscles which have rested for a time, acting less ener- 
 getically than those which have been kept in a state of continued activity (Griilz- 
 ner, Gscheidleri). 
 
 4. Glycogen. — The amount of glycogen (o. 43 per cent, in the muscles of a 
 frog or rabbit) and grape sugar is diminished in an active muscle ( O. Nasse, Weiss), 
 but muscles devoid of glycogen do not lose their excitability and contractility. 
 Hence, glycogen is certainly not the direct source of the energy in an active 
 muscle. Perhaps it is to be sought for in an as yet unknown decomposition 
 product of glycogen {Luchsinger). [There is more glycogen in the red than in 
 the pale muscles of a rabbit.] 
 
 5. Extractives. — An active muscle contains less extractive substances soluble 
 in water, but more extractives soluble in alcohol (v. Helmholtz, 18-45) > it also 
 contains less of the substances which form C0 2 {Ranke) ; less fatty acids (Sczelkow) ; 
 less kreatin and kreatinin [v. Voit). 
 
 6. During contraction, the amount of water in the muscular tissue increases, 
 while that of the blood is correspondingly diminished {J. Ranke). The solid 
 substances of the blood are increased, while they (albumin) are diminished in 
 the lymph {Fano). 
 
 7. Urea. — The amount of urea excreted from the body is not materially 
 increased during muscular exertion {v. Voit, Pick and Wislicenus'). According to 
 Parkes, however, although the excretion of urea is not increased immediately, yet 
 after 1 to i]4 days there is a slight increase. The amount of work done cannot 
 be determined from the amount of albumin which is changed into urea. 
 
 [Relation of Muscular Work to Urea — Ed. Smith, Parkes and others have made numerous 
 Investigations on this subject. Fick and Wislicenus (1866) ascended the Faulhorn, and for seven- 
 teen hours before the ascent and for six hours after the ascent no proteid food was taken — the diet, 
 consisting of cakes made of fat, sugar and starch. The urine was collected in three periods, as 
 follows : — 
 
 
 Fick. 
 
 Wislicenus. 
 
 1. Urea of 11 hours before the ascent . . 
 
 2. " 8 " during " . . 
 
 3. " 6 " after " . . 
 
 238.55 g". 
 
 221.05 g rs - 
 
 A hearty meal was taken after this period, and the urine of the next eleven hours after the period 
 of rest contained 159.15 grains of urea (Fick), and 176 71 ( Wislicenus). All the experiments go 
 to show that the amount of urea excreted in the urine is far more dependent upon the nitrogen 
 ingested, i.e., the nature of the food, than upon the decomposition of the muscular substance. A 
 vegetable diet diminishes, while an animal diet greatly increases, the amount of urea in the urine. 
 North's researches confirm thoss of Parkes, but he finds that the disturbance produced by severe 
 muscular labor is considerable. The elimination of phosphates is not affected, while the sulphates 
 in the urine are increased.] 
 
 During the activity of a muscle, all the groups of the chemical substances 
 present in muscle undergo more rapid transformations (_/. Ranke). It is still a 
 matter of doubt, therefore, whether we may assume that the kinetic energy of a 
 muscle is chiefly due to the transformation of the chemical energy of the carbo- 
 hydrates which are decomposed or used up in the process of contraction. As yet 
 we do not know whether the glycogen is supplied by the blood stream to the 
 muscles, perhaps from the liver, or whether it is formed within the muscles them- 
 selves from some unknown derivative of the proteids. The normal circulation is 
 certainly one of the conditions for the formation of glycogen in muscle, as gly- 
 cogen diminishes after ligature of the blood vessels {Chandelon). A muscle in 
 
504 STAGES OF CADAVERIC RIGIDITY. 
 
 which the blood circulates freely is capable of doing more work than one devoid 
 of blood (Ranke), and even in the intact body more blood is always supplied to 
 the contracted muscles. 
 
 295. RIGOR MORTIS. — Cause. — Excised striped, or smooth muscles, and 
 also the muscles of an intact body, at a certain time after death, pass into a con- 
 dition of rigidity — cadaveric rigidity or rigor mortis. When all the muscles 
 of a corpse are thus affected, the whole cadaver becomes completely stiff or rigid. 
 The cause of this phenomenon depends upon the spontaneous coagulation of a 
 proteid, viz., the myosin of the muscular fibre (Kuhne), in consequence of the 
 formation of a small amount of an acid. Under certain circumstances, the 
 coagulation of the other proteids of the muscle may increase the rigidity. 
 During the process of coagulation, heat is set free (v. Walther, Fick — § 223), 
 owing to the passage of the fluid myosin into the solid condition, and also to the 
 simultaneous and subsequently increased density of the tissue. 
 
 Properties of a Muscle in Rigor Mortis. — It is shorter, thicker and some- 
 what denser (Schmulewilsch, Walter) ; stiff, compact and solid ; turbid and 
 opaque (owing to the coagulation of the myosin) ; incompletely elastic, less 
 extensible, and more easily torn or ruptured ; it is completely inexcitable to 
 stimuli ; the muscular electrical current is abolished (or there is a slight current in 
 the opposite direction) ; its reaction is acid, owing to the formation of both forms 
 of lactic acid (§ 293) glycero-phosphoric acid (Diakanow) ; while it also develops 
 free C0 2 . When an incision is made into a rigid muscle, fluid (muscle serum, 
 p. 501) appears spontaneously in the wound. 
 
 The first formed lactic acid converts the salts of the muscle into acid salts ; thus potassium lactate 
 and acid potassium phosphate are formed from potassium phosphate. The lactic acid, which is 
 formed thereafter, remains free and ununited in the muscle. 
 
 Amount of Glycogen. — The newest observations of Bohm are against the view that, during 
 rigor mortis, a partial or complete transformation of the glycogen into sugar and then into lactic 
 acid takes place. During digestion, a temporary storage of glycogen occurs in the muscles as well 
 as in the liver, so that about as much is found in the muscles as in the liver. There is no diminu- 
 tion of the glycogen when rigidity takes place, provided putrefaction be prevented ; so that the 
 lactic acid of rigid muscles cannot be formed from glycogen, but more probably it is formed from the 
 decomposition of the albuminates [Demant, Bohm): 
 
 The amount of acid does not vary, whether the rigidity occurs rapidly or slowly (J. Ranke] ; 
 when acidification begins, the rigidity becomes more marked, owing to the coagulation of the alkali 
 albuminate of the muscle. Less C0 2 is formed from a rigid muscle, the more C0 2 it has given off 
 previously, during muscular exertion. A rigid muscle gives off N and absorbs O. In a cadaveric 
 rigid muscle, fibrin ferment is present (Al. Schmidt and others). It seems to be a product of pro- 
 toplasm, and is never absent where this occurs (Rauschenbach). 
 
 [Rigor Mortis and Coagulation of Blood. — Thus there is a marked 
 analogy between the coagulation of the blood and that of muscle. In both cases, 
 a fluid body yields a solid body, fibrin from blood, and myosin from muscle, and 
 there are many other points of analogy (p. 506).] 
 
 Stages of Rigidity. — Two stages are recognizable in cadaveric muscles : In 
 the first stage, the muscle is rigid, but still excitable; in this stage the myosin 
 seems to be in a jelly-like condition. Restitution is still possible during this 
 stage. In the second stage, the rigidity is well pronounced, with all the phe- 
 nomena above mentioned. 
 
 The onset of the rigidity varies in man from ten minutes to seven hours [and it 
 is complete, as a rule, within four to six hours after death. The muscles of the 
 jaws are first affected, then those of the neck and trunk, afterward (as a rule) the 
 lower limbs, and finally the upper limbs]. Its duration is equally variable — one 
 to six days. After the cadaveric rigidity has disappeared, the muscles, owing to 
 further decompositions and an alkaline reaction, become soft and the rigidity dis- 
 appears (Nysten, Sommer). The onset of the rigidity is always preceded by a loss 
 of nervous activity. Hence, the muscles of the head and neck are first affected, 
 and the other muscles in a descending series (§ 325). Disappearance of the rigid- 
 
EFFECTS OF HEAT AND WATER ON MUSCLE. 505 
 
 ity occurs first in the muscles first affected (Nysteri). Great muscular activity be- 
 fore death {e.g., spasms of tetanus, cholera, strychnin, or opium poisoning) causes 
 rapid and intense rigidity ; hence the heart becomes rigid relatively rapidly 
 and strongly. Hunted animals may become affected within a few minutes 
 after death. [This is often seen in the fox.] Usually the rigidity lasts longer the 
 later it occurs. Rigidity does not occur in a fetus before the seventh month. A 
 frog's muscle cooled to o° C. does not begin to exhibit cadaveric rigidity for four 
 to seven days. 
 
 Stenson's Experiment. — The amount of blood in a muscle has a marked 
 effect upon the onset of the rigidity. Ligature of the muscular arteries causes at 
 first in all mammals an increase of the muscular excitability and then a rapid fall of 
 the excitability (Schmulewitsch) ; thereafter stiffness occurs, the one stage following 
 closely upon the other (Swammerdam, Nic. Stenson, i66f). [If the ligature be 
 removed in the first stage, the muscle recovers, but in the later stages the rigidity 
 is permanent.] If the artery going to a muscle be ligatured, Stannius observed 
 that the excitability of the motor nerves disappeared after an hour, that of the mus- 
 cular substance after four to five hours, and then cadaveric rigidity set in. 
 
 Pathological. — When the blood vessels of a muscle are occluded, by coagulation taking place 
 within them (Landois), rigidity of the muscles is produced ($ 102). True cadaveric rigidity may 
 be produced by too tight bandaging ; the muscles are paralyzed, rigid, and break up into flakes, 
 while the contents of the fibre are afterward absorbed {R. Volkmanti). Occlusion of the blood 
 vessels of muscles by infarcts, especially in persons with atheromatous arteries, may even cause 
 necrosis of the muscles implicated [Finch, Girandeau). 
 
 If the circulation be reestablished during the first stage of the rigidity, the 
 muscle soon recovers its excitability {Stannius). When the second stage has set 
 in, restitution is impossible (Kilhne). In cold-blooded animals, cadaveric rigidity 
 does not occur for several days after ligaturing the blood vessels. Brown-Sequard, 
 by injecting fresh oxygenated blood into the blood vessels, succeeded in restoring 
 the excitability of the muscles of a human cadaver four hours after death, i. <?., 
 during the first stage of cadaveric rigidity. Ludwig and Al. Schmidt found that 
 the onset of cadaveric rigidity was greatly retarded in excised muscles, when arte- 
 rial blood was passed through their blood vessels. Blood deprived of its O did 
 not produce this effect. Cadaveric rigidity occurs relatively early after severe 
 hemorrhage. If a weak alkaline fluid be conducted through the dead muscles of 
 a frog, cadaveric rigidity is prevented (Schipiloff). 
 
 Section of Nerves. — Preliminary section of the motor nerves causes a 
 later onset of the rigidity in the corresponding muscles {Brown-Sequard, Heineke). 
 Perhaps this is caused by the greater accumulation of blood in the paralyzed parts 
 (due to section of the vasomotor nerves). In fishes, whose medulla oblongata is 
 suddenly destroyed, cadaveric rigidity occurs much more slowly than in those ani- 
 mals that die slowly (Blane). 
 
 Rigidity may be produced artificially by various reagents : — 
 
 1. Heat [" Heat stiffening " (Pickford)~] causes the myosin to coagulate at 
 40 C. in cold-blooded animals, in birds about 53° C., and in mammals at 48 to 
 50° C. The protoplasm of plants and animals, e.g., of the amoeba, is coagulated 
 by heat, giving rise to heat rigor. 
 
 Schmulewitsch found that the longer a muscle had been excised from the body, the greater was 
 the heat required to produce stiffening. Heat stiffening differs from cadaveric rigidity thus: a 13 
 per cent, solution of ammonium chloride dissolves out the myosin from a cadaveric rigid muscle, but 
 not from one rendered rigid by heat (Schipiloff). If the rigid cadaveric muscles of a frog be heated, 
 another proteid coagulates at 45°, and lastly at 75 the serum albumin itself. Hence, both processes 
 together make the muscle more rigid ({! 295). 
 
 2. When a muscle is saturated with distilled water, it produces " water 
 stiffening ' ' —an acid reaction being developed at the same time. 
 
 Muscles rendered stiff by water still exhibit electro-motive phenomena, while muscles rendered 
 rigid by other means do not (Bicdermann). If the upper limb of a frog be ligatured, deprived of 
 
506 MUSCULAR EXCITABILITY. 
 
 its skin, and dipped in warm water, it becomes rigid. If the ligature be removed and the circulation 
 reestablished, the rigidity may be partially set aside. If there be well-marked rigidity, it can only 
 be set aside by placing the limb in a 10 per cent, solution of common salt, which dissolves the coag- 
 ulum of myosin (Preyer). 
 
 3. Acids, even C0 2 , rapidly produce "acid stiffening," which is probably- 
 different from ordinary stiffening, as such muscles do not evolve any free C0 2 (Z. 
 Hermann). The injection of 0.1 to 0.2 per cent, solutions of lactic or hydro- 
 chloric acid into the muscles of a frog produces stiffening at once, which may be 
 set aside by injecting 0.5 per cent, solution of an acid, or by a solution of soda, or 
 by 15 per cent, solution of ammonium chloride. The] acids form a compound 
 with the myosin (Schipilojp). 
 
 4. Freezing and thawing a part alternately, rapidly produces stiffening ; and 
 it is aided by mechanical injuries. 
 
 Poisons. — Rigor mortis is favored by quinine, caffein, digitalin, [a concentrated solution of 
 caffein or digitalin, applied to the muscle of a frog, produces rigor mortis,] veratrin, hydrocyanic 
 acid, ether, chloroform, the oils of mustard, fennel, and aniseed; direct contact of muscular tissue 
 with potassium sulphocyanide {Bernard, Setschenow), ammonia, alcohol, and metallic salts. 
 
 Position of the Body. — The attitude of the body during cadaveric rigidity is generally that 
 occupied at death ; the position of the limbs is the result of the varying tensions of the different 
 muscles. During the occurrence of rigor mortis, a limb, or more frequently the arm and fingers, 
 may move (Sommer). Thus, if stiffening occurs rapidly and firmly in certain groups of muscles, 
 this may produce movements, as is sometimes seen in cholera. If cadaveric rigidity occurs very 
 rapidly, the body may occupy the same position which it did at the moment of death, as sometimes 
 happens on the battle-field. In these cases it does not seem that a contracted condition of the muscle 
 passes at once into rigor mortis ; but between these two conditions, according to Briicke, there is 
 always a very short relaxation. 
 
 Muscles which have been plunged into boiling water do not undergo rigor mortis,' neither do 
 they become acid (Du Bois Raymond), nor evolve free C0 2 (L. Hermann). 
 
 Analogy between Contraction and Rigidity. — L. Hermann has drawn attention to the 
 analogy which exists between a muscle in a state of contraction and one in a state of cadaveric 
 rigidity — both evolve C0 2 and the other acids from the same source. The form of the contracted 
 and the stiffened muscle is shorter and thicker ; both are denser, less elastic, and evolve heat ; in 
 both cases, the muscular contents behave negatively as regards their electro-motive force, in refer- 
 ence to the unaltered, living, resting substance. Hence he is inclined to regard a muscular contrac- 
 tion as a temporary, physiological, rapidly disappearing rigor, whilst other observers regard stiffen. 
 ing as in a certain sense the last flickering act of a living muscle. 
 
 Work done during Rigidity. — A muscle in the act of becoming stiff will lift a weight, but the 
 height to which it is lifted is greater with small weights, but less with heavier weights, than when a 
 living muscle is stimulated with a maximal stimulus. 
 
 Disappearance of Rigidity. — When rigor mortis passes off, there is a con- 
 siderable amount of acid formed in the muscle, which dissolves the coagulated 
 myosin. After a time putrefaction sets in, accompanied by the presence of 
 micro-organisms and the evolution of ammonia and putrefactive gases (H 2 S, N, 
 C0 2 -§ 184). 
 
 According to Onimus, the loss of excitability which precedes the onset of rigor mortis occurs 
 in the following order in man : Left ventricle, stomach, intestine (55 minutes) ; urinary bladder, 
 right ventricle (60 minutes) ; iris (105 minutes) ; muscles of face and tongue (180 minutes) ; the 
 extensors of the extremities (about one hour before the flexors) ; the muscles of the trunk (five to 
 six hours). The oesophagus remains excitable for a long time (§ 325). 
 
 296. MUSCULAR EXCITABILITY.— By the term excitability or 
 irritability of a muscle, is meant that property in virtue of which a muscle 
 shortens when it is stimulated. The condition of excitement is the active condi- 
 tion of a muscle produced by the application of stimuli, and is usually indicated 
 by the act of contraction. Stimuli are simply various forms of energy, and they 
 throw the muscle into a state of excitement, while at the moment of activity the 
 chemical energy of the muscle is transformed into work and heat, so that stimuli 
 act as liberating or " discharging forces." The normal temperature of the 
 body is most favorable for maintaining the normal muscular excitability; the ex- 
 citability varies as the temperature rises or falls. 
 
ACTION OF CURARA. 507 
 
 As long as the blood stream within a muscle is uninterrupted, the first effect 
 of stimulation of a muscle is to increase its energizing power, partly because the 
 circulation is more lively and the blood vessels are dilated, but after a time the 
 energizing power is diminished. Even in excised muscles,- especially when the 
 large nerve trunks have already lost their excitability, the excitability is increased 
 after a stimulus, so that the application of a series of stimuli of the same strength 
 causes a series of contractions which are greater than at first ( Wundf). Hence, 
 we account for the fact that, although the first feeble stimulus may be unable to 
 discharge a contraction, the second may, because the first one has increased the 
 muscular excitability (Fick). 
 
 Effect of Cold. — If the muscles of a frog or tortoise be kept in a. cool place, they may remain 
 excitable for ten days, while the muscles of warm-blooded animals cease to be excitable after one 
 and a half to two and a half hours. (For the heart, see g 55.) A muscle, when stimulated directly, 
 always remains excitable for a longer time when its motor nerve is already dead. 
 
 [Independent Muscular Excitability.— Since the time of Albrecht v. Haller and R. Whytt, 
 physiologists have ascribed to muscle a condition of excitability which is entirely independent of 
 the existence of motor nerves, and which depends on certain constituents of the sarcous substance. 
 Excitability, or the property of responding to a stimulus, is » widely distributed function of proto- 
 plasm or its modifications. A colorless blood corpuscle or an amceba is excitable, and so are secre- 
 tory and nerve cells. In the first cases, the application of a stimulus results in motion in an indefi- 
 nite direction, in the second in a formation of the secretion, and in the third in the discharge of 
 nerve energy. In the case of muscle, a stimulus causes movement in a definite direction, called a 
 contraction, and depending on the contractility of the sarcous substance. There are many considera- 
 tions which show that excitability is independent of the nervous system, although in the higher 
 animals nerves are the usual medium through which the excitability is brought into action. Thus 
 plants are excitable, and they contain no nerves.] 
 
 Numerous experiments attest the " independent excitability " of muscle : 
 1. There are chemical stimuli, which do not cause movement when applied to 
 motor nerves, but do so when they are applied directly to muscle ; ammonia, lime 
 water, carbolic acid. 2. The ends of the sartorius of the frog, in which no nerve 
 terminations are observable by means of the microscope, contract when they are 
 stimulated directly (Kuhne). 3. Curara paralyzes the extremities of the motor 
 nerves, while the muscles themselves remain excitable (C7. Bernard, Kolliker). 
 The action of cold, or arrest of the blood supply in an animal, abolishes the excita- 
 bility of the nerves, but not of the muscles at the same time. 4. After section of 
 its nerve, a muscle still remains excitable, even after the nerves have undergone 
 fatty degeneration (Brown- Sequard, Bidder). 5. Sometimes electrical stimuli act 
 only upon the nerves and not upon the muscle itself (Brucke). [6. The foetal 
 heart contracts rhythmically before any nervous structures are discoverable in it.] 
 
 [The Action of Curara. — Curara, woorali, urari, or Indian arrow poison of South America, is 
 the inspissated juice of the Strychnos crevauxi. A watery extract of the drug, when injected under 
 the skin or into the blood of an animal, acts chiefly upon the motor nerve endings, and does not 
 affect the muscular contractility. An active substance, curarin, has been isolated from it (p. 510). 
 Poison a frog by injecting a few milligrammes into the dorsal lymph sac. In a few minutes after 
 the poison is absorbed, the animal ceases to support itself on its fore limbs; it lies flat on the table, 
 its limbs are paralyzed, and so are the respiratory movements in the throat. When completely under 
 the action of the poison, th° frog lies in any position, limp and motionless, neither exhibiting vol- 
 untary nor reflex movements. If the brain be destroyed and the skin removed, on faradizing the 
 sciatic nerve no contraction of the muscles of the hind limb occurs; but if the electrical stimulus 
 be applied directly to the muscles, they contract, thus proving that curara poisons the motor 
 connections and not the muscles. If the dose be not too large, the heart still continues to beat, 
 and the vasomotor nerves remain active.] 
 
 [Methods. — (1) This may be shown also by applying the drug locally. 
 Bernard took two nerve-muscle preparations, put some solution of curara into 
 two watch glasses, and dipped the nerve into one glass and the muscle into the 
 other. The curara penetrated into both preparations, and he found, on stimu- 
 lating the nerve which had been steeped in curara, that its muscle still contracted, 
 so that the curara had not acted on the motor fibres ; while stimulation of the 
 
508 
 
 ACTION OF CURARA. 
 
 Frog with sciatic artery liga- 
 tured. S P, spinal cord ; 
 P, poisoned, N P, non- 
 poisoned leg; M, gastroc- 
 nemius muscles, afferent, 
 efferent, nerve (after 
 j\utherford and Brun- 
 ion). 
 
 nerve of the other preparation produced no contraction, 
 although the corresponding muscle contracted. In this 
 case, the curara had penetrated into the muscle and 
 affected the intra-muscular nerve endings.] 
 
 [(2) But it is the terminal or intra-muscular portions 
 of the nerves, not the nerve trunk, which are paralyzed. 
 Ligature the sciatic artery, or, better still, tie all the parts 
 of the hind limb of a frog at the upper part of a thigh, 
 except the sciatic nerve (Fig. 289). Inject curara into the 
 dorsal lymph sac. The poisoned blood will, of course, cir- 
 culate in every part of the body except the ligatured limb. 
 [The shaded parts are traversed by the poison.] The animal 
 can still, at a certain stage of the poisoning, pull up the 
 non-poisoned limb, while it cannot move the poisoned one. 
 At this time, although poisoned blood has circulated in the 
 sacral and intra-abdominal parts of the nerves, yet they are 
 not paralyzed, so that the poison does not act on this part 
 of the trunk of the nerve. But we can show that it does 
 not act on any part of the extra-muscular trunk of the 
 nerve. This is done by ligaturing the arteries going to 
 the gastrocnemius muscle, and then poisoning the animal. 
 On stimulating the nerve on the ligatured side, the gas- 
 trocnemius of that side contracts, although the whole 
 length of the nerve trunk has been supplied by poisoned 
 blood. Therefore, it is the intra-muscular terminations of 
 the nerves which are acted on.] 
 [By means of the following arrangement, we may prove that the actual termina- 
 tions or end plates are paralyzed. Ligature the sciatic artery of one leg of a frog, 
 and then inject curara into a lymph sac. After the animal is fully poisoned, dissect 
 out the whole length of the sciatic nerve in both legs, leaving all the muscles below 
 the knee joint, then clean and divide the femur at its middle. Pin a straw flag to 
 each limb, and fix both femora in a clamp, or muscle forceps, with the gastroc- 
 nemii uppermost, as in Fig. 290. Place the two nerves, N, on Du Bois-Reymond's 
 electrodes (Fig. 291), attached to two wires coming from a commutator, C (Fig. 
 290). From two other binding screws of the commutator, two wires pass and are 
 made to pierce the gastrocnemii. The other two binding screws of the commu- 
 tator are connected with the secondary coil of a Du Bois-Reymond's induction 
 machine (§ 330). The bridge of the commutator can be turned so as to pass the 
 current either through both muscles or both nerves — the latter is the case in the 
 diagram (H). When both nerves are stimulated, only the non-poisoned leg (N P) 
 contracts. Reverse the commutator, and pass the current through both muscles, 
 when both contract .] 
 
 [Rosenthal's Modification. — Pull the secondary coil far away from the primary, and pass the 
 current through both muscles. Gradually approximate the secondary to the primary coil, and in 
 doing so it will be found that the non-poisoned leg contracts first, and on continuing to push up the 
 secondary coil both limbs contract. Thus the poisoned limb does not respond to so feeble a faradic 
 stimulus as the non poisoned one, a. result which is not due to the action of the curara on the 
 excitability of the muscle. The non-^poisoned limb responds to a feebler stimulus because its motor 
 nerve terminations are not paralyzed, while the poisoned leg does not do so, because the motor ter- 
 minations are paralyzed. A feebler induced shock suffices to cause a muscle to contract when it is 
 applied to the nerve than when it is applied to the muscle itself directly. In large doses, curara 
 also affects the spinal cord.] 
 
 The whole question of " specific muscular excitability " has entered upon a new phase, 
 owing to the researches of Gerlach on the terminations of motor nerves in muscle. Since it has 
 been shown that a nerve fibre, after penetrating the sarcolemma, breaks up into inter- fibrillar 
 threads, which come into direct relation with the sarcous substance, we can scarcely speak of an 
 isolated stimulation of a muscle, for all stimuli which are applied to a muscle must at the same time 
 act on the nerve, for the muscle is the proper end organ of a motor nerve. 
 
MUSCULAR AND CHEMICAL STIMULI OF MUSCLE. 
 
 509 
 
 N euro- Muscular Cells. — Even in the lower animals, e.g., Hydra {Kleinenberg\ and Medusa 
 (Eimer) there are uni-cellular structures called " neuromuscular cells" in which the nervous and 
 muscular substances are represented in the same cell. [The outer part of these cells is adapted for 
 the action of stimuli, and corresponds to the nervous receptive organ, while the inner deeper part is 
 contractile, and is the representative of the muscular part.] 
 
 Muscular Stimuli. — Various stimuli cause a muscle to contract, either by act- 
 ing upon its motor nerve (indirect), or upon the muscular substance itself 
 (direct) (§ 324). 
 
 1. Under ordinary circumstances, the normal stimulus causing a muscle to 
 contract is the nerve impulse which passes along a curve, but its exact nature is 
 unknown, e.g., in voluntary movements, automatic motor movements, and reflex 
 acts. 
 
 2. Chemical Stimuli. — All chemical substances, which alter the chemical 
 composition of a muscle with sufficient rapidity, act as muscular stimuli. Accord- 
 ing to Kiihne, mineral acids (HC1 0.1) per cent., acetic and oxalic acids, the 
 
 Scheme of the curara experiment. B, battery ; 
 I, primary; II, secondary spiral; N. 
 nerves; F, clamp; N P, non-poisoned 
 leg; P, poisoned leg; C, commutator; K, 
 key (after Rutherford'). 
 
 Du Bois-Reymond's platinum electrodes. The nerve is placed 
 over the two pieces of platinum, P, which rest on vulcanite ; 
 B, universal joint ; V, support. 
 
 salts of iron, zinc, copper, silver and lead, bile {Budge), all act in weak solutions 
 as muscular stimuli ; while they act upon the motor nerve only when they are more 
 concentrated. Lactic acid and glycerin, when concentrated, excite only (?) the 
 nerve ; when dilute, only the muscle. Neutral alkaline salts act equally upon 
 nerve and muscle ; alcohol and ether act on both very feebly. When water is 
 injected into the blood vessels, it causes fibrillar muscular contractions {v. WitticK), 
 while a 0.6 per cent, solution of NaCl may be passed through a muscle for days 
 without causing contraction {Kolliker, O. Nasse). Acids, alkalies and extract of 
 flesh diminish the muscular excitability, while the muscular stimuli, in small doses, 
 increase it {Ranke). Gases and vapors stimulate muscle ; they cause either a 
 simple contraction {e.g., HC1), or at once permanent contraction or con- 
 tracture {e.g., CI). Long exposure to the gas causes rigidity. The vapor of 
 bisulphide of carbon stimulates only the nerves, while most vapors {e.g., HC1) 
 kill without exciting them {Kuhne andjani~). 
 
510 THERMAL, MECHANICAL AND ELECTRICAL STIMULI OF MUSCLE. 
 
 Method. — In making experiments upon the chemical stimulation of muscle, it is inadvisable to 
 dip the transverse section of the muscle into the solution of the chemical reagent [Bering). The 
 chemical stimulus ought to be applied in solution to a limited portion of the uninjured surface of 
 the muscle ; after a few seconds, we obtain a contraction or fibrillar twitchings of the superficial 
 muscular layers [Bering). 
 
 [Rhythmical Contraction. — While rhythmical contractions are very marked in smooth muscle 
 (especially if it is stretched or subjected to considerable internal pressure, as in the hollow viscera), 
 e.g., the intestine, uterus, ureter, blood vessels, and also in the striped but involuntary cardiac mus- 
 culature [I 58), they are not, as a rule, very common in striped voluntary muscle. Chemical 
 stimuli are particularly effective in producing them.] If the sartorius of a curarized frog be dipped 
 into a solution composed of 5 grms. NaCl, 2 grms. alkaline sodium phosphate, and 0.5 grm. sodium 
 carbonate in 1 litre of water, at lo° C, the muscle contracts rhythmically, and may do so for 
 several days [especially with a low temperature] [Biedermann). This recalls the rhythmical con- 
 traction of the heart. [Kuhne found a similar result. The rhythm is arrested by lactic acid and 
 restored by an alkaline solution of NaCl.] Rhythmical movements may also be induced in the 
 sartorius (frog), by the combined action of a dilute solution of sodic carbonate and an ascending 
 constant electrical current. Compare also the action of a constant current on the heart (f! 58). 
 
 3. Thermal Stimuli. — If an excised frog's muscle be rapidly heated toward 
 28 J C, a gradually increasing contraction occurs, which, at 30 C, is more pro- 
 nounced, reaching its maximum at 45 C. [Eckhard, SchumlewitscK). If the 
 temperature be raised, "heat stiffening" rapidly ensues. The smooth muscles 
 of warm-blooded animals also contract when they are warmed, but those of cold- 
 blooded animals are elongated by heat [Grunhagen, Samkowy). If a frog's 
 muscle be cooled to o°, it is very excitable to mechanical stimuli (Griinhagen) ; 
 it is even excited by a temperature under o° {Eckhard}. 
 
 CI. Bernard observed that the muscles of animals, artificially cooled ({! 225), remained excitable 
 many hours after death. Heat causes the excitability to disappear rapidly, but increases it tempo- 
 rarily. 
 
 4. Mechanical Stimuli. — Every kind of sudden mechanical stimulus, pro- 
 vided it be applied with sufficient rapidity to a muscle (and also to a nerve), 
 causes a contraction. If stimuli of sufficient intensity be repeated with sufficient 
 rapidity, tetanus is produced. Strong local stimulation causes a weal-like, long- 
 continued contraction at the part stimulated (§ 297, 3, a). Moderate tension of 
 a muscle increases its excitability. 
 
 5. Electrical Stimuli will be referred to when treating of the stimulation of 
 nerve (§ 324). 
 
 Other Actions of Curara. — When injected into the blood or subcutaneously, it causes at first 
 paralysis of the intra-muscular ends of the motor nerves (p. 507), while the muscles themselves re- 
 main excitable ; the sensory nerves, the central nervous system, viscera, heart, intestine, and the 
 blood vessels are not affected at first [CI. Bernard, Kolliker). [If the skin be stimulated, the frog 
 will still pull up the ligatured leg reflexly, although the other leg will remain quiescent ; this shows 
 that the sensory nerve and nerve centres are still intact ; but when the action of the drug is fully 
 developed, no amount of stimulation of the skin or the posterior roots of the nerves will give rise 
 to a reflex act, although the motor nerve of the ligatured limb is known to be excitable, hence it is 
 probable that the nerve centres in the cord themselves are ultimately affected. If the dose be very 
 large, the heart and blood vessels may be affected.] In warm-blooded animals, death takes 
 place by asphyxia, owing to paralysis of the diaphragm, but of course there are no spasms. In 
 frogs, where the skin is the most important respiratory organ, if a suitable dose be injected under 
 the skin, the animal may remain motionless for days and yet recover, the poison being eliminated by 
 the urine [Kuhne, Bidder). If the dose be larger, the inhibitory fibres of the vagus may be para- 
 lyzed. In electrical fishes, the sensory nerves concerned with the electrical discharge are paralyzed 
 [Marey). In frogs, the lymph hearts are paralyzed. A dose sufficient to kill a frog, when injected 
 under its skin, will do so if administered by the mouth, because the poison seems to be eliminated as 
 rapidly by the kidneys as it is absorbed from the gastric mucous membrane. For the same reason 
 the flesh of an animal killed by curara is not poisonous when eaten. If, however, the ureters 
 be tied, the poison collects in the blood, and poisoning takes place ( L. Hermann). [In this case 
 the mammal may exhibit convulsions. Why ? The action of curara is to paralyze, and it para- 
 lyzes the respiratory nerves, so that asphyxia is produced from the venosity of the blood. It affects 
 the respiratory nerve endings before those in the muscles generally, so that when the venous blood 
 stimulates the nerve centres the partially affected muscles respond by convulsions. In this way, 
 other narcotics may excite convulsions indirectly by inducing a venous condition of the blood, while 
 the motor centres, nerves, and muscles are still unaffected.] Large doses, however, poison unin- 
 
TOTAL AND PARTIAL MUSCULAR CONTRACTION. 511 
 
 jured animals even when given by the mouth. The nerves (Funke) and muscles ( Valentin) of 
 I oisoned animals exhibit considerable electro-motive force. [For the effect of curara on lymph 
 formation ((I igg, 6).] 
 
 Atropin appears to be a specific poison for smooth muscular tissue, but different muscles are 
 differently affected (Szpilmann, Luchsinger). [This is doubtful. A small quantity of atropin 
 seems to affect the motor nerves of smooth muscle in the same way that curara does those of striped 
 muscle ; we must remember, however, that there are no end plates proper in the former, so that the 
 link between the nerve fibrils and the contractile substance is probably different in the two cases. It 
 is well known that the amount of striped and smooth muscle varies in the cesophagus in different 
 animals. Szpilmann and Luchsinger find that after the action of atropin, stimulation of the periph- 
 eral end of the vagus will still cause contraction of the striped muscular fibres in the cesuphagus, 
 but not of the smooth fibres, although both forms of muscular tissue respond to direct stimulation.] 
 
 Excitability after Section of the Motor Nerves. — After section of the motor nerve of a 
 muscle, the excitability undergoes remarkable changes ; after three to four days the excitability of 
 the paralyzed muscle is diminished, both for direct and indirect (»". e., through the nerve) stimuli ; 
 this condition is followed by a stage, during which a constant current is more active than normal, 
 while induction currents are scarcely or not at all effective (§ 339, 1). The excitability for mechan- 
 ical stimuli is also increased. The increased excitability occurs until about the seventh week ; it 
 gradually diminishes until it is abolished toward the sixth to the seventh month. Fatty degenera- 
 tion begins in the second week after section of the motor nerve, and goes on until there is complete 
 muscular atrophy. Immediately after section of the sciatic nerve, Schmulewitsch found that the 
 excitability of the muscles supplied by it was increased. 
 
 297. CHANGES IN A MUSCLE DURING CONTRACTION.— 
 I. Macroscopic Phenomena. — 1. When a muscle contracts, it becomes 
 ' shorter and at the same time thicker. 
 
 The degree of contraction, which in very excitable frogs may be 65 to 85 per cent. (72 per 
 cent, mean) of the total length of the muscle, depends upon various conditions: (a) Up to a cer- 
 tain point, increasing the strength of the stimulus causes a greater degree of contraction ; (b) 
 as the muscular fatigue increases, i. <?., after continued vigorous exertion, the stimulus remaining 
 the same, the extent of contraction is diminished ; (c) the temperature of the surroundings has a 
 certain effect. The extent of the contraction is increased in a lrog's muscle — the strength of stim- 
 ulus and degree of fatigue remaining the same— when it is heated to 33° C. If the temperature be 
 increased above this point, the degree of contraction is diminished (Schmulewitsch). 
 
 2. The volume of a contracted muscle is slightly diminished {Swammerdam, 
 f 1680). Hence, the specific gravity of a contracted muscle is slightly in- 
 creased, the ratio to the non-contracted muscle being 1062 : 1061 (Valentin); 
 the diminution in volume is, however, only T ^Vtr- 
 
 Methods. — (a) Erman placed portions of the body of a live eel in a glass vessel filled with an 
 indifferent fluid. A narrow tube communicated with the glass vessel, and the fluid rose in the tube 
 to a certain level. As soon as the muscles of the eel were caused to contract, the fluid in the index 
 tube sank, (b) Landois demonstrates the decrease in volume by means of a manometric flame. 
 The cylindrical vessel containing the muscle is provided with two electrodes fixed into it in an air-_ 
 tight manner. The interior of the vessel communicates with the gas supply, while there is a small 
 narrow exit tube for the gas, which is lighted. Every time the muscle contracts the flame dimin- 
 ishes. The same experiment may be performed with a contracting heart. 
 
 3. Total and Partial Contraction. — Normally, all stimuli applied to a muscle' 
 or its motor nerve cause contraction in all its muscular fibres. Thus, the muscle 
 conducts the state of excitement to all its parts. Under certain circumstances, 
 however, this is not the case, viz.: (0) when the muscle is greatly fatigued, or 
 when it is about to die, a violent mechanical stimulus, as a vigorous tap with the 
 finger or a percussion hammer (and also chemical or electrical stimuli), cause a 
 localized contraction of the muscular fibres. This is Schiff's " idio-muscular 
 contraction." The same phenomenon is exhibited by the muscles of a healthy 
 man, when .the blunt edge of an instrument is drawn transversely over the direc- 
 tion of thef muscular fibres {Miihlhauser, AuerbacK). (6) Under certain as yet but 
 imperfectly, unknown conditions, a muscle exhibits so-called fibrillar contrac- 
 tions, i. e., short contractions occur alternately in different bundles of muscular 
 fibres. This ; is the case in the muscles of the tongue, after section of the hypo- 
 glossal nerve (Schiff) ; and in the muscles of the face, after section of the facial 
 nerve. 
 
MICROSCOPIC PHENOMENA OF MUSCULAR CONTRACTION. 
 
 [In some phthisical patients there is marked muscular excitabilty, so that if the pectoral muscle 
 be percussed, a local contraction — idio-muscular — occurs, either confined to the spot, or two waves 
 may proceed outward and return to the spot struck.] 
 
 Cause of Fibrillar Contraction. — According to Bleuler and Lehmann, section of the hypo- 
 glossal nerve in rabbits is followed by fibrillar contractions after sixty to eighty hours ; these con- 
 tractions may continue for six months, even when the divided nerve has healed and is stimulated above 
 the cicatrix so as to produce movements in the corresponding half of the tongue. Stimulation of 
 the lingual nerve increases the fibrillar contractions or arrests them. This nerve contains vaso- 
 dilator , fibres derived from the chorda tympani. Schiff is of opinion that the increased blood 
 stream through the organ is the cause of the contractions. Sig. Mayer found that, by compressing 
 the carotids and subclavian, and again removing the pressure, so as to permit free circulation, the 
 muscles of the face contracted. Section of the motor nerves of the face did not abolish the phe- 
 nomenon, but compression of the arteries did. The cause of the phenomenon, therefore, seems to 
 lie within the muscles themselves. This phenomenon may be compared to the paralytic secretion 
 of saliva, and pancreatic juice which follows section of the nerves going to these glands (pp. 239, 
 284). Similar fibrillar contractions occur in man under pathological conditions, but they may also 
 occar without any signs of pathological disturbance. [Fibrillar contractions, due to a central cause, 
 occur in monkeys after excision of the thyroid gland (V.Horsley, \ 103, III).] [Some. drugs 
 cause fibrillar muscular contractions, e.g., aconitin, guanidin, nicotin, pilocarpin, but physostigmin 
 produces them in warm-blooded animals (not in frogs). According to Brunton, these drugs prob- 
 ably act by irritating the motor nerve endings, as the contractions are gradually abolished by 
 curara.] 
 
 Fig. 292. 
 
 ii 
 
 
 d 
 
 a 
 c 
 b 
 
 e 
 
 UHili 
 
 mam 
 
 ABMHb 
 
 
 sBHBffil 
 
 The microscopic appearances during a muscular contraction in the individual elements of the fibrillse. 
 
 Engelmann) ; 4, 5 (after Merkel). 
 
 1, 2, 3 (after 
 
 II. Microscopic Phenomena. — i. Single muscular fibrilla exhibit the same 
 phenomena as an entire muscle, in that they contract and become thicker. 2. 
 There is great difficulty in observing the changes that occur in the individual 
 parts of a muscular fibre during the act of contraction. This much is certain, 
 that the muscular elements become shorter and broader during contraction. Thus, 
 it is evident that the transverse striae must appear to approach nearer to each other 
 {Bowman, 1846). 3. There is great difference of opinion as to the behavior of 
 the doubly-refractive (anisotropous) and the singly-refractive media. 
 
 Fig. 292, 1, on the left, represents, according to Engelmann, a passive muscular element — from 
 c to d is the doubly-refractive contractile substance, with the median disk, a, 6, in it ; h and g are 
 the lateral disks. Besides these, in each of the singly-refractive disks there is a clear disk — " sec- 
 ondary disk "—/ and e, which is only slightly doubly refractive. This occurs only in the muscles 
 of insects. Fig. 1, on the right, shows the same element in polarized light, whereby the middle 
 area of the element, as far as the contractile substance proper extends, is, owing to its double refrac 
 tion, bright; while the other part of the muscular element, owing to its being singly refractive, is 
 black. Fig. 292, 2, is the transition stage, and 3 the proper stage of contraction of the muscular 
 element. In both cases the figures on the left are viewed in ordinary light, and on the right, in 
 polarized light. 
 
 Engelmann's View. — According to Engelmann, during contraction (Fig. 292, 3), the singly- 
 refractive disk becomes, as a whole, more refractive, the doubly refractive less so. Consequently, 
 
MUSCULAR CONTRACTION. 
 
 513 
 
 a fibre at a certain degree of contraction (2), when viewed in ordinary light, may appear homoge- 
 neous and but slightly striped transversely = the homogeneous and transition stage. During a greater 
 degree of contraction (3), very dark transverse stripes reappear, corresponding to the singly-refrac- 
 tive disks. At every stage of the contraction, as well as in the transition stage, the singly- and 
 doubly-refractive disks are sharplydefined, and are recognized by the polariscope as regular alter- 
 nating layers (in 1, 2 and 3 on the right). These do not change places during the contraction. The 
 height of both disks is diminished during contraction, but the singly-refractive do so more rapidly than 
 the doubly-refractive disks. The total volume of each element does not undergo any appreciable 
 alteration in volume during the contraction. Hence, the doubly-refractive disks increase in volume 
 at the expense of the singly refractive. From this it is concluded that, during the contraction, fluid 
 passes from the singly-refractive into the doubly-refractive disks; the former shrink, the latter swell. 
 
 Merkel's view is partially different. In Fig. 292, 4, are two muscular elements at rest; in (5), 
 two in a state of contraction, after Merkel. The gray punctuated areas are the doubly-refractive 
 substance, c, the median disk. According to Merkel, during contraction the dark substance lying 
 in the middle of the element changes its position — either in part or as a whole ; it leaves the middle 
 of the element (the two surfaces of Hensen's median disks, 4, c), and places itself at the lateral 
 disks, 5, at e and d, while the clear substance leaves the lateral disks,, 4, e and d, and applies itself 
 to both surfaces of the median disk, 5, c. The clear substance of the isotropous disks is fluid, and 
 plays a more passive role ; during contraction, it is in part absorbed by the dark substance which 
 thus swells up. This mutual exchange of place of the substances is accompanied by an interme- 
 diate " stage of dissolution" in which the whole contents of the element appear equally homoge- 
 neous {Montgomery) ; in which, therefore, the fluid, singly-refractive substance has uniformly pene- 
 trated the doubly-refractive substance. At this moment only the lateral disks are still visible. 
 
 [If a living portion of an insect's muscle be examined in its own juice, contraction waves may be 
 seen to pass over the fibres. When a contraction wave passes over part of the fibres, the disks 
 become shorter and hroader ; at the same time, in the fully-contracted part, the dim disk appears 
 lighter than the centre of the light disk. There is said to be a " reversal of the stripes " from 
 what obtains in a passive muscle. Before this stage is reached there is an intermediate stage, where 
 the two bands are almost uniform in appearance.] 
 
 Methods. — These phenomena are best observed by " fixing" the different stages of rest or con- 
 traction, by suddenly plunging the muscular fibrilke of insect's muscles into alcohol or osmic acid, 
 which coagulates the muscle substance. The actual contraction may be observed under the micro- 
 scope in the transparent parts of the larvae of insects. 
 
 Spectrum. — A thin muscle, e.g., the sartorius of the frog, when placed directly behind a narrow 
 slit running at right angles to the course of the fibres, yields a diffraction spectrum. When the 
 muscle contracts, as by mechanical stimulation, the spectrum broadens — a proof that the interspaces 
 of the transverse stripes become narrower (Jianvier). 
 
 298. MUSCULAR CONTRACTION.— Myography— Simple Con- 
 traction — Tetanus. — Methods. — In order to determine the duration of each 
 phase of a muscular contraction, myo- 
 graphs of various forms are used. 
 
 V. Helmholtz's Myograph. — Helmholtz 
 constructed a myograph of the form shown in 
 Fig. 293. A muscle, M — say the gastroc- 
 nemius of a frog attached to the femur — is 
 fixed by the femur in a clamp, K, the lower 
 free end of the muscle being attached to a 
 movable lever carrying a scale pan and 
 weight, W, the weight being varied at 
 pleasure. When the muscle contracts, neces- 
 sarily it must raise the lever. To the free 
 end of the lever is attached a movable style, 
 F, capable of adjustment, and which, when 
 properly adjusted, inscribes its movements 
 on a revolving cylinder caused to rotate at 
 a uniform rate by means of clockwork (Fig. 
 98). The cylinder is covered with enameled 
 paper smoked in the flame of » turpentine 
 lamp. When the muscle contracts, it inscribes 
 a curve — the " muscle curve," or "myo- 
 gram." The abscissa indicates the dura- 
 tion of the contraction, but of course the rate at 
 which the cylinder is moving must be known. Scheme of v. Helmholtz's myograph. M, muscle fixed in a 
 The ordinates represent the height of con- S lam P' ?■'• F, writing style : P, weight or counterpoise 
 K , . , ., B for 'he lever; W scale pan for weights ; S, S, supports 
 
 traction at any particular part of the curve. for the lever. «>>■-«■«■ 
 
 33 
 
514 
 
 PENDULUM MYOGRAPH. 
 
 The muscle curve may be inscribed upon a smoked glass plate attached to one limb of a vibrating 
 tuning fork (Fig. 91). Such a curve registers the time units in all its parts. Suppose each 
 vibration of the tuning fork = 0.01613 second, then the duration of any part of such a curve is 
 obtained by counting the number of vibrations and multiplying by 0.01613 second. 
 
 [Pendulum Myograph. — A. Kick invented this instrument. In its improved form by v. Helm- 
 holtz (Fig. 294), it is shown both from the front and the side. A board fixed to the wall carries a 
 heavy iron pendulum, P, whose axis, A, A, moves on friction rollers. At the lower swinging end 
 are two glass plates, G and G', fixed to a bearer, T. The plates can be adjusted by means of the 
 screw, s, so that several curves can be written one above the other. The plate G', on the posterior 
 
 Fig. 294. 
 
 Fick's pendulum myograph, as improved by v. Helmholtz (^ natural size), side and front view. 
 
 surface, is merely a compensator, so that when G is elevated G' is lowered, and thus the duration 
 of the oscillation is not altered. The spring catches, H, H, which can be turned inward or out- 
 ward, are used to fix the pendulum by the teeth, a, a, when it is drawn to one side. The pendu- 
 lum is drawn to one side and fixed, a, in H, so that when H is pulled down, it is liberated and 
 swings to the other side, where it is caught by H at the opposite side. In the improved form, the 
 catches, H, are made to slide along a rod like the arc of a circle, so that the length of the swing can 
 be varied. As the pendulum swings from the one side to the other, the projecting points, a, a, knock 
 over the contact key, b, and the current is opened and a shock transmitted to the muscle. The 
 writing lever to which the muscle is attached is usually a heavy one, and a style writes upon the 
 
CONTRACTION CURVE OF HUMAN MUSCLE. 
 
 515 
 
 smoked surface of the glass. Of course, when the pendulum swings, it moves with unequal velo- 
 cities at different parts of its course.] 
 
 [When using the pendulum myograph to study a muscular contraction, arrange it as in Fig. 295. 
 The frog's muscle is attached to a writing lever, which is very like the lever in Fig. 293, while the 
 style inscribes its movements on the blackened plate.] 
 
 [The pendulum is fixed in the catch, C, as shown in the figure ; the key, K', is closed and placed 
 in the primary circuit, while two wires from the secondary coil of an induction machine are attached 
 to the muscle. When the pendulum swings, the projecting tooth, S, knocks over the contact at K7, 
 and breaks the primary circuit, when a shock is instantly transmitted through the muscle. Before 
 stimulating, allow the pendulum to swing to obtain an abscissa. The time is recorded by a vibrating 
 tuning fork, of known rate of vibration, connected with a Depre's electric chronograph. Depre's 
 chronograph is merely a small electro-magnet with a fine writing style attached to the magnet, which 
 vibrates when it is introduced in an electrical circuit, in which is placed a vibrating tuning fork. 
 The signal vibrates just as often as the tuning fork.] _._' ^ 
 
 [Spring Myograph. — This is used by Du Bois-Reymond chiefly for demonstrations (Fig. 296). 
 It consists of a glass plate fixed in a frame, and 
 
 moving on two polished steel wires, stretched Fig. 295. 
 
 between the supports A and B. At b is a spring, 
 which, when it is compressed between the upright, 
 B, and the knot, b, drives the glass plate from B 
 to A. As the plate moves from one side to the 
 other, a small tooth, d, on its under surface, 
 opens the key, A, and thus a shock is transmitted 
 to the muscle. The arrangement otherwise is 
 the same as for the pendulum myograph. The 
 smoked glass plate is liberated by the projecting 
 finger plate attached to the upright, A.] 
 
 [Simple Myograph of Marey. — The gas- 
 trocnemius is attached to a horizontal lever, 
 which inscribes its movements on a revolving 
 cylinder. This form of myograph, when pro- 
 vided with two levers, is very useful for compar- 
 ing the action of a poison on one limb, the other 
 being unpoisoned.] 
 
 [Pfluger's stationary form, which is simply 
 a Helmholtz's myograph (Fig. 293) arranged to 
 record its movements on a stationary glass plate, 
 so that the muscle merely makes a vertical line 
 or ordinate instead of a curve ; it thus merely 
 indicates the height or extent of the contraction, 
 not its duration.] 
 
 A rapidly rotating disk was used by Valentin 
 and Rosenthal for registering the muscle curve, 
 while Harless used a plate which was allowed to 
 fall rapidly, the so-called " Fall myograph." 
 In all these experiments it is necessary to indicate at the same time the moment of stimulation. 
 
 Contraction Curve of Human Muscle. — In man, another principle is 
 adopted, viz., to measure the increase in thickness during the contraction, either 
 by means of a lever or a compressible tambour {Marey), such as is used in Brond- 
 geest's pansphygmograph (Fig. 72). [The thickening of the adductor muscles of 
 the thumb may be registered by means of Marey' s pince myographique.] 
 
 I. Simple Contraction. — If a single shock or stimulus of momentary duration 
 be applied to a muscle, a " simple muscular contraction " [or shortly, a con- 
 traction, a twitch (Burdon Sandersorij\\s the result, i.e., the muscle rapidly 
 shortens and quickly returns again to its original relaxed condition. 
 
 Myogram or Muscle Curve. — Suppose a single stimulus be applied to a 
 muscle attached to a light writing lever, which is not " overweighted " with any 
 weight attached to it, then, when the muscle contracts, the following events take 
 place : — 
 
 [(1) A period or stage of latent stimulation (Fig. 298). 
 
 (2) A period of increasing energy or contraction. 
 
 (3) A period of decreasing energy or more rapid relaxation. 
 
 (4) A period of slow relaxation, or the elastic after-vibration. ] 
 
 Scheme of the arrangement of the pendulum myograph. 
 B, battery; I, primary, II, secondary spiral of the 
 induction machine ; S, tooth ; K', key ; C, C, 
 catches ; K' in the corner, scheme of K' K, key in 
 primary circuit. 
 
516 
 
 LATENT PERIOD OF A MUSCLE CURVE. 
 
 The muscle curve proper is composed of 2, 3, and 4, and its characters are 
 shown in Figs. 297, 298. 
 
 1. The latent period (Fig. 297, a, S) consists in this, that the muscle does 
 not begin to contract precisely at the moment the stimulus is applied to it, but the 
 contraction occurs somewhat later, i. e., a short but measurable interval elapses 
 between the application of a momentary stimulus and the contraction (v. Helm- 
 holtz). If the entire muscle be stimulated by a momentary stimulus, e.g., a single 
 
 Fig. 296. 
 
 1 
 
 opening induction shock, the duration of the latent period is about 0.01 second. 
 In smooth muscle, the latent period may last for several seconds. 
 
 [Although no change be visible in a muscle during the latent period, neverthe- 
 less we have proof that some change does take place within the muscle substance, 
 for we know that the electrical current of the muscle is diminished during this 
 
 Fig. 297. 
 
 Muscle curve produced by the application of a single induction shock to a muscle.' a~f, abscissa ; a-c, ordinate ; 
 a b, period of latent stimulation; b d, 'period of increasing energy; d e , period of decreasing energy ; e /, 
 elastic after-vibrations. 
 
 period, or we have what is known as the negative variation of the muscle cur- 
 rent {Bernstein — § 333).] 
 
 In man the latent period varies between 0.004 and 0.01 second. If the experiment be so arranged 
 that the muscle can contract as soon as the stimulus is applied to it, i. e., before time is lost in mak- 
 ing the muscle tense; or, to put it otherwise, if the muscle has not "to take in slack," as it were, 
 the latent period may fall to 0.004 second [Gad). If the muscle be still attached to the body, pro- 
 tected as much as possible from external influences and properly supplied with blood, the latent 
 period may be reduced to 0.003. 
 
PENDULUM MYOGRAPH CURVE. 
 
 517 
 
 Modifying Influence. — The latent period is shortened by an increased strength of the stimulus 
 and by heat ; while fatigue, cooling and increasing weight lengthen it (Lauterbach, Mendelsohn, 
 Yeo, Cash). The latent period of an opening contraction may be even as much as 0.04 second 
 longer than that of a closing contraction. The red muscles have a longer latent period than the 
 white (p. 523). Before the muscle contracts as a whole, the individual fibres within it must have 
 contracted. We must, therefore, conclude that the latency of the individual muscular elements 
 is shorter than that of the entire muscle [Gad, Tigerstedi). 
 
 2. The Contraction or Stage of Increasing Energy, i.e., from the 
 moment the muscle begins to shorten until it reaches its greatest degree of con- 
 traction {b d). At first the muscle contracts slowly, then more rapidly, and 
 again more slowly,, so that the ascending limb of the curve has somewhat the 
 form of an/. This stage lasts 0.03 to 0.4 second. It is shorter when the con- 
 traction is shorter (weak stimulus) and the less the weight the muscle has to lift, 
 It also varies with the excitability of the muscle, being shorter in a fresh, non- 
 fatigued muscle. 
 
 3. Elongation or Stage of Decreasing Energy, — After the muscle has 
 contracted up to its maximum for any particular stimulus, it begins to relax — at 
 first slowly, then rapidly — and lastly more slowly, so that an inverse of an/ is 
 obtained (d e). This stage is usually of shorter duration than 2. The duration 
 varies with the strength of the stimulus, being shorter than 2 with a weak stimulus, 
 and longer with a strong stimulus. It also depends upon the extent to which the 
 muscle is loaded during contraction. 
 
 4. The fourth stage has received various names — stage of elastic after- 
 
 Fig. 298. 
 
 Muscle curve of af rag's gastrocnemius attached to a heavy lever tracing on a pendulum myograph. Time tracing 
 of chronograph 120 double vibrations per sec. Stimulus applied at a ; a b (z) latent period, b c (2) shortening, 
 erf (3) elongation, (c) height of contraction : e (4) slow relaxation (after Rutherford'). 
 
 vibration [residual contraction or contraction remainder {Hermann). 
 The after-vibrations (ef), which disappear gradually, depend upon the elasticity 
 of the muscle. The duration of this stage is longest with a powerful contraction, 
 and when the weight attached to the muscle is small.] 
 
 [In studying a Muscle Curve, the more or less vertical character of the 
 ascent will indicate the rapidity of the contraction, the height above the base 
 line, the extent and power of contraction, the length of the curve the duration, 
 and the line of descent the rate of its extensibility.] 
 
 If the stimulus be applied to the motor nerve instead of to the muscle itself, 
 the contraction is greater {Pfiuger), and lasts longer (Wundf) the nearer to the 
 spinal cord the stimulus is applied to the nerve. 
 
 [Pendulum Myograph Curve. — The form of the muscle curve will vary 
 with the kind of myograph used ; if it be stationary, then the muscle will merely 
 record a vertical line ; if the recording surface move quickly, the two parts of 
 the curve will form an acute angle ; and if it move with great rapidity, they will 
 have the form of Fig. 298, which is that obtained with a pendulum myograph. A 
 vibrating tuning fork records time directly under the tracing, whereby the dura- 
 tion of each part of the curve is readily determined. The parts marked 1, 2, 3 
 and 4 correspond to those so numbered on p. 515.] 
 
 [In measuring the myogram, all that is required is to know the moment at which the stimulus 
 was applied, and to note when the curve begins to leave the base line or abscissa. Raise a vertical 
 
518 
 
 OVERWEIGHTED MUSCLES. 
 
 Fig. 299. 
 
 Arrangement for estimating the time relations 
 during contraction of a muscle produced 
 by a faradic shock. B, battery ; K, key 
 in primary circuit ; I, primary, II, second- 
 ary spiral ; /, muscle lever ; e, electro- 
 magnet in primary circuit; t, electric sig- 
 nal ; St, support ; R C, revolving cylinder 
 (after Rutherford}. 
 
 line from each of these points, and the interval between these lines, as measured by the chronograph, 
 indicates the time (Fig. 298).] 
 
 [Method — Faradic Shocks. — The time relations of a muscular contrac- 
 tion may be studied by means of the following arrangement : Attach a frog's 
 
 gastrocnemius to a lever, as in Fig. 299, and 
 through the frog's muscle place two wires from 
 the secondary coil of an induction machine. 
 A scale pan, into which weights may be placed, 
 may be attached to the lever, especially if it is 
 one of the light levers used by Marey. On the 
 same support adjust an electro-magnet with a 
 writing style in the primary circuit, and in this 
 circuit also place a key (K) to make and break 
 the current. Fix also a Depre's chronograph 
 to the same support, and make it vibrate by 
 connecting it in circuit with a tuning fork of 
 known rate of vibration, and driven by a gal- 
 vanic battery. See that the points of all three, 
 levers write exactly over each other on the 
 revolving cylinder. The upper lever registers 
 the contraction, the electro-magnet the moment 
 the stimulus is applied to the muscle, and the 
 electrical chronograph the time.] 
 
 Overweighted Muscles. — The foregoing remarks 
 apply to curves obtained by a light lever connected with 
 the muscle. If the muscle lever be " overweighted" or 
 overloaded, i.e., if the lever be loaded, so that when the 
 muscle contracts it has to lift these weights, the course of the curve is varied according to the 
 weight to be lifted. It is necessary, however, to support the lever in the intervals when .the muscle 
 is at rest. As the weights are increased, the occurrence of the contraction is delayed. This is due 
 to the fact that the muscle, at the moment of stimulation, must accumulate as much energy as is 
 necessary to lift the weight. The greater the weight the longer is the time before it is raised. 
 Lastly, the muscle may be so "loaded," or "overloaded," that it cannot contract at all : this is the 
 limit of the muscular or mechanical energy of the muscle (v. Helmholtz). 
 
 Fatigue. — If a muscle be caused to contract so frequently that it becomes 
 "fatigued," the latent period is longer, the curve is not so high, because the mus- 
 cular contraction is less, and the abscissa is longer, i. e., the contraction is slower 
 and lasts longer (Figs. 300, I, 312). Cooling a muscle has the same effect {v. 
 Helmholtz and others). Soltmann finds that the fresh muscles of new-born animals 
 behave in a similar manner. The myogram has a flat apex and considerable elon- 
 gation in the descending limb of the curve. 
 
 Constant Current. — If the motor nerve of a muscle be stimulated by a closing 
 or opening shock of a constant current, the resulting muscular contraction cor- 
 responds exactly to that already described. If, however, the current be closed or 
 opened, with the muscle itself directly in the circuit, during the closing shock, 
 there is a certain degree of contraction which lasts for a time, so that the curve 
 assumes the form of Fig. 301, where S represents the moment of closing or 
 making the current, and O the moment of opening or breaking it ( Wundt — com- 
 pare §336, D). 
 
 The investigations of Cash and Kronecker show that individual muscles have a special form of 
 muscle curve ; the omohyoid of the tortoise contracts more rapidly than the pectoralis. Similar 
 differences occur in the muscles of frogs and mammals. The flexors of the frog contract more 
 rapidly than the extensors (Griitzner). Sometimes within one and the same muscle there are "red" 
 (rich in glycogen) and " pale " fibres ($ 292). The red fibres contract more slowly, are less excitable 
 and less easily fatigued [Griitzner). The muscles of flying insects contract very rapidly, even more 
 han 100 times per second. 
 
J OTHER POISONS ON MUSCLE. 
 
 519 
 
 [uinine (Schtsehepotiew) increase the height of the 
 yc nerve), while larger doses diminish it, and finally 
 action in large doses, but the maximum of contrac- 
 /eratrin also increase the contractions, but the stage 
 nd Clostermeyer). Veratrin, antiarin and digitalin, 
 n such a way that the contractions become very pro- 
 anus (Harless, 1862). The latent period of muscles 
 :d at first, and afterward lengthened. The gastroc- 
 soda contracts more rapidly (Griitzner). Kunkel is 
 ing the imbibition of water by the sarcous substance. 
 . (| 297, II), the form of the contraction of the poi- 
 dition of imbibition produced by the drug. 
 
 G. 300. 
 
 traction on a vibrating plate attached to a tuning fork. Each 
 c, stage of increasing energy ; erf, of decreasing energy. II, 
 i inscribed on a vibrating plate. Ill, The most rapid trem- 
 ed on the same plate. 
 
 , £-,-_.«...»*■. — x, uTiog-uc porauiictx w-im vtrratrin, and then be made to spring, it does so rapidly, 
 
 but when it alights again the hind legs are extended, and they are only drawn up after a time. 
 Thus, rapid and powerful contraction, with slow and prolonged relaxation, are the character of the 
 movements. In a muscle poisoned with veratrin the ascent is quick enough, but it remains con- 
 tracted for a long time, so that this condition has been called " contracture." A single stimulation 
 may cause a contraction lasting five to fifteen seconds, according to circumstances. Brunton and 
 Cash find that cold has a marked effect on the action of veratrin ; in fact, its effect may be perma- 
 nently destroyed by exposure to extremes of heat or cold. The muscle curve of a brainless frog 
 
 Fig. 301. 
 
 Effect on a muscle of closing and opening a constant current. S, closing; O, opening shock (Wundt). 
 
 cooled artificially, and then poisoned by veratrin, occasionally gives no indications of the action 01 
 the poison until its temperature is raised, and this is not due to non-absorption of the poison. Cold, 
 therefore, abolishes or lessens the contracture peculiar to the veratrin curve. Similar results are 
 obtained with salts of barium, and to a less degree by those of strontium and calcium (Brunton 
 and Cash). ] 
 
 Smooth Muscles. — The muscle curve of smooth or non-striped muscles is 
 similar to that of the striped muscles, but the duration of the contraction is visibly- 
 much longer, and there are other points of difference. Some muscles stand mid- 
 way between these two — at least, so far as the duration of their contractions are 
 concerned. 
 
520 ACTION OF TWO SUCCESSIVE STIMULI. 
 
 The " red " muscles of rabbits, the muscles of the tortoise, the adductors of the common mussel, 
 and the heart, all react in a similar manner. The muscles of flying insects contract extremely 
 rapidly, more than ioo times per second (H. Landois). 
 
 Contraction Remainder. — A contracted muscle assumes its original length 
 only when it is extended by sufficient traction, e. g., by means of a weight (Kiihne). 
 Otherwise, the muscle may remain partially shortened for a long time (v. Helm- 
 hollz, Schiff). This condition has been called "contracture" (Tiegel), or, 
 better, contraction remainder {Hermann). This condition is most marked in 
 muscles that have been previously subjected to strong, direct stimulation, and are 
 greatly fatigued {Tiegel), which are distinctly acid, and ready to pass into rigor 
 mortis, or in muscles excised from animals poisoned with veratrin (v. Bezold). 
 
 Rapidity of Muscular Contraction. — In man, single muscular movements 
 can be executed with great rapidity. The time relations of such movements are 
 most readily ascertained by inscribing the movements upon a smoked glass plate 
 attached to a tuning fork. Fig. 300, II, represents the most rapid voluntary 
 movements that Landois could execute, as, e.g., in writing letters, n, n, and every 
 contraction is equal to about' 3.5 vibrations (1 vibration = 0.01613 second) = 
 0.0564 second. In III, the right arm was tetanized, in which case 2 to 2.5 vibra- 
 tions occur = 0.0323 to 0.0403 second. 
 
 Pathological. — In secondary degeneration of the spinal cord after apoplexy, atrophic muscular 
 anchylosis of the limbs (Edinger), muscular atrophy, progressive ataxia, and paralysis agitans of long 
 standing, the latent period is lengthened ; while it is shortened in the contracture of senile chorea 
 and spastic tabes (Mendelsohn). The whole curve is lengthened in jaundice and diabetes (Edin- 
 ger). In cerebal hemiplegia, during the stage of contracture, the muscle curve resembles the curve 
 of a muscle poisoned with veratrin, and the same is the case in spastic spinal paralysis and amyo- 
 trophic lateral sclerosis ; in pseudo-hypertrophy of the muscles the ascent is short and the descent 
 very elongated. In muscular atrophy, after cerebral hemiplegia, and in tabes, the latent period in- 
 creases, while the height of the curve diminishes. In chorea the curve is short. (For the Reac- 
 tion of Degeneration, see § 339.) In'rare cases-in man it has been observed that the execution of 
 spontaneous movements results in a very prolonged contraction (Thomson's disease). In such 
 cases the muscular fibres are very broad, and the nuclei increased (Erb). 
 
 II. Action of Two Successive Stimuli. — Let two momentary stimuli be 
 applied successively to a muscle : (A) If each stimulus or shock be of itself suffi- 
 cient to cause a maximal contraction, i. e, the greatest possible contraction 
 which the muscle can accomplish, then the effect will vary according to the time 
 which elapses between the application of the two stimuli, (a) If the second stim- 
 ulus is applied to the muscle after the relaxation of the muscle following upon the 
 first stimulus, we obtain merely two maximal contractions. (J>) If, however, the 
 second stimulus be applied to the muscle during the time that the effect of the first 
 is present, i. e. , while the muscle is in the phase of contraction or of relaxation ; 
 in this case the second stimulus causes a new maximal contraction, according to 
 the time of the particular phase of the contraction, (c) When, lastly, the second 
 stimulus follows the first so rapidly that both occur during the latent period, we 
 obtain only one maximal contraction (v. Helmholtz). It is to be specially noted 
 that a single maximal stimulus never excites the same degree of shortening as 
 tetanic stimulation (III), but only about yi of the height of the contraction in 
 tetanus. 
 
 (B) If the stimuli be not maximal, but only such as cause a medium or sub- 
 maximal contraction, the effects of both stimuli are superposed, or there is a 
 summation of the contractions (Fig. 302). It is of no consequence at what 
 particular phase of the primary contraction the second shock is applied. In all 
 cases, the second stimulus causes a contraction, just as if the phase of contraction 
 caused by the first shock was the natural passive form of the muscle, i. e., the new 
 contraction {b, c) starts from that point as from an abscissa (Fig. 302, I, b). Thus, 
 under favorable conditions the contraction may be twice as great as that caused by 
 the first stimulus. The most favorable time for the application of the second 
 stimulus is ^ second after the application of the first (Sewall). The effects of 
 
TETANUS OF MUSCLE. 
 
 521 
 
 both stimuli are obtained even when- the second stimulus is applied during the 
 latent period (v. Helmholtz). 
 
 III. Tetanus — Summation of Stimuli. — If stimuli, each capable of causing 
 a contraction following each other with medium rapidity, be applied to a muscle, the 
 muscle has not sufficient time to elongate or relax in the intervals of stimulation. 
 Therefore, according to the rapidity of the successive stimuli, it remains in a con- 
 dition of continued vibratory contraction, or in a state of tetanus. Tetanus is, 
 however, not a continuous uniform condition of contraction, but it is a discontinu- 
 ous condition or form of the muscle, depending upon the summation or accu- 
 mulation of contractions. If the stimuli are applied with moderate rapidity, the 
 individual contractions appear in the curve (Fig. 302, II); if they occur rapidly, 
 and thus become superposed and fused, the curve appears continuous and unbroken 
 by elevations and depressions (Fig. 302, III). As a fatigued muscle contracts 
 slowly, it is evident that such a muscle will become tetanic by a smaller number of 
 stimuli per second than will suffice for a fresh muscle (Mqrey, Fick, Minot.) All 
 muscular movements of long duration occurring in our bodies are probably tetanic 
 in their nature {Ed. Weler). 
 
 [Summation of Stimuli. — If a stimulus, insufficient in itself to cause con- 
 traction of a muscle, be repeatedly applied to a muscle in proper tempo and of 
 
 Fig. 302. 
 
 . two successive sub-maximal contractions ; IT, successive contractions produced by stimulating a muscle with 12 
 induction shocks per second ; III, curve produced with very rapid induction shocks (complete tetanus). 
 
 sufficient strength, at first a slight and then a stronger or maximal contraction may 
 be produced. This process of summation occurs also in nervous tissue (§ 360).] 
 
 A continued voluntary contraction in man consists of a series of single con- 
 tractions rapidly following each other. Every such movement, on being carefully 
 analyzed, consists of intermittent vibrations, which reach their maximum when a 
 person shivers {Ed. Weber). [Baxt found that the simplest possible voluntary 
 contraction, e. g., striking with the index finger, occupies on an average nearly 
 twice as long time as a similar movement discharged by a single induction shock.] 
 
 The requisite degree of shortening is obtained by the summation of single stimuli applied to the 
 slowly contracting muscle until the desired degree of shortening is obtained. In estimating exactly 
 the amount of movement we generally oppose some resistance by contracting antagonistic muscles, 
 as is shown by observations on spare individuals (Briicke). 
 
 The tetanic contractions, which occur normally in an intact body, are proved to consist of a 
 series of successive contractions, because they can give rise to secondary tetanus (f! 332), which may 
 also be caused by muscles thrown into tetanus by strychnin poisoning {Loven). The muscle sound 
 cannot be regarded as a certain proof of the oscillatory movement in tetanus [as Helmholtz has 
 shown that this sound coincides with the resonance sound of the ear {Hering and FriedricK). 
 
 If a muscle be connected with a telephone, whose wires are brought into connection with two 
 needles, one placed in the tendon, and the other in the substance of the muscle, we hear a sound 
 when the muscle is thrown into tetanus, which proves that periodic vibratory processes, i. e., succes- 
 sive contractions, occur in the muscle (Bernstein and Schonlein). The sound is most distinct when 
 
522 TETANUS OF MUSCLE. 
 
 the tetanizing NeePs hammer of an induction machine vibrates about 50 times per sound ( Wedenski 
 and Kronecker). 
 
 The number of stimuli requisite to produce tetanus varies in different animals, and in different 
 muscles of the same animal. About 15 stimuli per second are required to produce tetanus in the 
 
 Fig. 303. 
 
 Curves obtained from red (upper) and pale (lower) muscles of a rabbit, by stimulating the sciatic nerve with a single 
 induction shock. The lowest line, T, indicates time, and is divided into r$ n second. 
 
 Fig. 304. 
 
 Opening and closing induction shocks of 300 units, applied at intervals of v> second to the pale (lower) and red 
 (upper) muscles of a rabbit. The lowest line, T, marks 5^ second {Kronecker and Stirling). 
 
 Fig. 305. 
 
 Tone inductorium of Kronecker and Stirling, d, iron rod, clamped at a ; j 7 , primary, s", secondary spiral, with a 
 key, k ; leather rollers,y and g, driven by wheels, h. 
 
 muscles of (he frog (hyoglossus only 10, gastrocnemius 27) ; very feeble stimuli (more than 20 per 
 second) cause tetanus (Kronecker) ; the muscles of the tortoise become tetanic with two to three 
 shocks per second ; the red muscles of the rabbit by 10, the pale by over 20 (Kronecker and Stir- 
 ling); muscles of birds not even with 70 (Marey); muscles of insects 330 to 340 per second 
 
RAPIDITY OF TRANSMISSION OF A CONTRACTION. 523 
 
 (Marey, Landois). Tetanic stimulation of the muscles of the crayfish (Astacus) and also in hydroph- 
 ilus, may cause rhythmical contractions {Richei), or rhythmically interrupted tetanus (Schonlein). 
 
 [The red and pale muscles of a rabbit, as already shown, differ structurally, and also in re- 
 gard to their blood supply (p. 496). They also differ physiologically. When both muscles are 
 caused to contract, by stimulating the sciatic nerve with a single induction shock, the curves obtained 
 are shown in Fig. 303 ; the lower one from the pale, and the upper from the red muscle. The 
 latent period is longer, while the duration of a simple contraction of a red muscle is three times 
 longer than that of a pale muscle. Four stimuli per second cause an incomplete tetanus, and 10 
 per second a nearly complete tetanus in the red muscles of a rabbit, while the pale muscles require 
 20 to 30 stimuli per second to be completely tetanized. Fig. 304 shows the results produced by in- 
 duction shocks applied to both muscles at intervals of % second.] 
 
 The extent of shortening in a tetanically contracted muscle, within certain limits, is dependent 
 upon the strength of the individual stimuli — but not upon their frequency. The contraction re- 
 mainder after tetanus is greater the stronger the stimuli, the longer they are applied, and the feebler 
 the muscle used {Bohr). Sometimes a stimulus applied to a muscle immediately after tetanus pro- 
 duces a greater effect than it did before the tetanus {Rossbach, Bohr). 
 
 Duration of Tetanus. — A tetanized muscle cannot remain contracted to the same extent for an 
 indefinite period, even if the stimuli are kept constant. It gradually begins to elongate, at first some- 
 what rapidly, and then more slowly, owing to the occurrence of fatigue. If the tetanic stimulation 
 is arrested, the muscle does not regain its original position and shape at once, but a contraction re- 
 mainder exists for a certain time, this being more evident after stimulation with induction shocks. 
 
 0. Saltmann found that the pale muscles of new-born rabbits were rendered tetanic with 16 
 stimuli per second, so that tetanus was produced in them with the same number of shocks as in 
 fatigued adult muscles. This may serve partly to explain the facility with which spasms occur in 
 new-born animals. 
 
 Curarized muscles sometimes pass into tetanus on the application of a momentary stimulus 
 {JCilhne, Hering). 
 
 IV. If very rapid (224 to 360 per second) induction shocks be applied to a 
 muscle, the tetanus, after a so-called " initial contraction " {Bernstein), may 
 cease {Harless, Heidenhairi). This occurs most readily when the nerves- are cooled 
 ( v. Juries). Kronecker and Stirling, however, found that stimuli following 
 each other at greater rapidity than 24,000 per second produced tetanus. 
 
 [Tone inductoriurn of Kronecker and Sterling. — This apparatus (Fig. 305), consists of a rod 
 of iron, d, fixed in an iron upright at a. The primary, s', and secondary spiral, s", rest on wooden 
 supports, which can be pushed over both ends of the rod. One end of the rod lies between leather 
 rollers,/ and^-, which can be made to rub on the rod by moving the toothed wheels, h. In this 
 way a tone is produced by the longitudinal vibrations of the rod, the number of vibrations being 
 proportional to the length of the rod, so that by means of this instrument we can produce from 
 1000 to 24,000 alternating induction shocks per second.] 
 
 299. RAPIDITY OF TRANSMISSION OF A CONTRACTION. 
 
 — 1. If a long muscle be stimulated at one end, a contraction occurs at that 
 point, and is rapidly propagated in a wave-like manner through the whole length 
 of the muscle, until it reaches the other end. The condition of excitement or 
 molecular disturbance is communicated to each successive part of the muscle, in 
 virtue of a special conductive capacity of the muscle. The mean velocity of 
 the contraction wave is 3 to 4 metres per second in the frog {Bernstein, 3.869 
 metres) ; rabbit, 4 to 5 metres {Bernstein and Steiner) ; lobster, 1 metre {Fre- 
 dericq and van de Velde) ; in smooth muscle and in the heart, only 10 to 15 
 millimetres per second {Engelmann, Marchland — pages 97, 98). These results 
 have reference only to excised muscles, the velocity of transmission being much 
 greater in the voluntary muscles of a living man, viz., 10 to 13 metres {Her- 
 mann, § 334, II). 
 
 Methods. — Aeby placed writing levers upon both ends of a muscle, the levers resting trans- 
 versely to the direction of the muscular fibres. The muscle was stimulated, and both levers regis- 
 tered their movements, the one directly over the other, on a revolving cylinder. On stimulating one 
 end of the muscle, the lever nearest to this point is raised by the contraction wave, and a little 
 later the other lever. When we know the rate at which the cylinder is moving, and the distance 
 between the two elevations, it is easy to calculate the rapidity of transmission of the contraction wave. 
 
 Duration and Wave Length. — The time, corresponding to the length of 
 the abscissa of the muscle curve inscribed by each writing lever, is equal to the 
 
524 MUSCULAR WORK. 
 
 duration of the contraction of this part of the muscle (according to Bernstein, 
 0.053 t0 0-098 second). If this value be multiplied by the rapidity of transmis- 
 sion of the muscular contraction wave, we obtain the wave length of the contraction 
 wave (= 206 to 380 millimetres). 
 
 Modifying Influences. — Cold (Fig. 306), fatigue, approaching death, and 
 many poisons [Veratrin, KCy] diminishes the velocity and the height of the con- 
 traction wave, while the strength of the stimulus and the extent to which the 
 muscle is loaded are without any effect upon the velocity of the wave (Aeby). 
 In excised muscles, the size of the wave diminishes as it passes along the muscle 
 {Bernsteiri), but this is not the case in the muscles of living men and animals. 
 The contraction wave never passes from one muscular fibre to a neighboring fibre. 
 
 [Fig. 306 shows the effect of cold on the muscles of a rabbit, in delaying the contraction wave. 
 There is a longer distance between 1 and 2 in the lower than in the upper curves.] 
 
 2. If a long muscle be stimulated locally near its middle, a contraction wave 
 is propagated toward both ends of the muscle. If several points be stimulated 
 simultaneously, a wave movement sets out from each, the waves passing over each 
 other in their course (Schif). 
 
 3. If a stimulus be applied to the motor nerve of a muscle, an impulse is 
 communicated to every muscular fibre ; a contraction wave begins at the end organ 
 
 Fig. 306. 
 
 Upper two curves, 2 and I, obtained from a rabbit's muscle by the above arrangement ; the lower two curves 
 from the same muscle, when it was cooled by ice. 
 
 [motorial end plate], and must be propagated in both directions along the mus- 
 cular fibres, whose length is only 3 to 4 centimetres. As the length of the motor 
 fibres from the nerve trunk to where they terminate in the motorial end plates is 
 unequal, contraction of all the muscular fibres cannot take place absolutely at the 
 same moment, as the nerve impulse takes a certain time to travel along a nerve. 
 Nevertheless, the difference is so small that, when a muscle is caused to contract 
 by stimulation of its motor nerve, practically the whole muscle appears to contract 
 simultaneously and at once. 
 
 4. A complete, uniform, momentary contraction of all the fibres of a muscle can 
 only take place when all the fibres are excited at thersame moment. This occurs 
 when the electrodes are placed at both ends of the muscle, and an electrical 
 stimulus of momentary duration passes through the whole length of the muscle. 
 
 300. MUSCULAR WORK. — Muscles are most perfect machines, not only 
 because they make the most thorough use of the substances on which their activity 
 depends (§ 217), but they are distinguished from all machines of human manu- 
 facture by the fact that by frequent exercise they become stronger, and are thereby 
 capable of accomplishing more work (J?u Bois-Reymond*). 
 
 The amount of work (W) which a muscle can perform (see introduction) is 
 equal to the product of the weight lifted (/) and the height to which it is lifted 
 
LAWS OF MUSCULAR WORK. 
 
 525 
 
 (h), i.e., W =ph. Hence, it follows that when a muscle is not loaded (where 
 p = o), then w must be = o, i.e., no work is performed. If, again, it be 
 overloaded with too great a load, so that it is unable to contract (h = o), here 
 also the work is nil. Between these two extremes an active muscle is capable of 
 doing a certain amount of " work." 
 
 I. Work with Maximal Stimulation. — When the strongest possible, or 
 maximal stimulus is applied, i.e., when the strength of the stimulus is such as 
 to cause a muscle to contract to the greatest possible extent of which it is capable, 
 the amount of work done increases more and more as the weight is increased, 
 but only up to a certain maximum. If the weight be gradually increased, so that 
 it is lifted to a less height, the amount of work diminishes more and more, and 
 gradually falls to be = o, when the weight is not lifted at all. 
 
 Example of the work done by a frog's muscle (Ed. Weber) : — 
 
 Weight Lifted in Grammes. 
 
 Height in Millimetres. 
 
 Work done in Gramme-Millimetres. 
 
 5 
 '5 
 
 25 
 
 3° 
 
 27.6 
 25.I 
 1 1. 45 
 
 7-3 
 
 138 
 376 
 286 
 220 
 
 200 
 
 I 
 
 350 
 grammes. 
 Height to which each ot the weights is 
 
 [Suppose a muscle be loaded with a certain number of grammes, and then caused to contract, 
 we get a certain height of contraction. Fig. 307 shows the result of an experiment of this kind. 
 The vertical lines represent the height to which the weights (in grammes) noted under them were 
 raised, so that, as a rule, as the weight increases the height to which it is raised decreases.] 
 
 Laws of Muscular Work. — i. A muscle can 
 lift a greater load, the larger its transverse section, FlG - 3°7- 
 
 i.e., the more fibres" it contains arranged parallel to 
 each other (Jiduard Weber, 1846). 
 
 2. The longer the muscle, the higher it can lift 
 a weight. 
 
 3. When a muscle begins to contract, it can lift 
 the largest load ; as the contraction proceeds it can 
 only lift less and less loads, and when it is at its 
 maximum of shortening only relatively very light 
 loads (Th. Schwann, 1837). 
 
 4. By the term " absolute muscular force," 
 is meant, according to Ed. Weber, just the weight - raised 
 which a muscle undergoing maximal stimulation 
 is no longer able to lift (the muscle being in its normal resting phase), and 
 without the muscle at the moment of stimulation being elongated by the weight. 
 
 Comparative. — Comparing the absolute muscular force of different muscles, even in different 
 animals, it is usual to calculate it with reference to that of a square centimetre. The mean 
 transverse section of a muscle is obtained by dividing its volume by its length. The volume is 
 equal to the absolute weight of the muscles divided by its specific gravity = 1058. The absolute 
 muscular force for I □ centimetre of a frog's muscle — 2 % 8 to 3 kilos. [6.6 lbs.] (J. Rosenthal) ; 
 for I □ centimetre of human muscle 7 to 8 (Henke and Knorz), or even 9 to 10 kilos. [20 to 23 
 lbs.] (Korster, Haughton). Insects can perform an extraordinary amount of work — an insect can 
 drag along sixty-seven times its body weight ; a horse scarcely three times its own weight. 
 
 5. During tetanus, when a weight is kept suspended, no work is done as long 
 as the weight is suspended, but of course work is done in the act of lifting the 
 load. To produce tetanus, successive stimuli are required, the muscular meta- 
 bolism is increased, and fatigue rapidly occurs. The potential energy in this case 
 is converted into heat (§ 302). When a muscle is stimulated with a maximal 
 stimulus, it cannot lift so great a weight with one contraction as when it is stimu- 
 lated tetanically {Hermann). The energy evolved, even during tetanus, is 
 
526 THE ELASTICITY OF MUSCLE. 
 
 greater the more frequent the stimulation, at least up to ioo stimuli per second 
 (Bernstein). 
 
 II. Medium Stimuli. — If a muscle be caused to contract by stimuli of 
 moderate strength, i.e., such as do not cause a maximal contraction, there are two 
 possibilities : Either the feeble stimulus is kept constant while the load is varied, 
 in which case the amount of work done follows the same law as obtains for maxi- 
 mal stimulation ; or, the load may be kept the same, while the strength of the 
 stimulus is varied. In the latter case, Fick observed that the height to which the 
 load was lifted increased in a direct ratio with the strength of the stimulus. 
 
 The stimulus which causes a muscle to contract must reach a certain strength or intensity before 
 it becomes effective, i. e., the " liminal intensity " of the stimulus, but this is independent of the 
 weight applied to the muscle. With minimal stimuli a small weight is raised higher than a large 
 one, but as the stimulus is increased, the contractions also increase in a larger ratio with an increased 
 load [v. Kries). 
 
 The blood stream within the muscles of an intact body is increased during 
 muscular activity. The blood vessels of the muscle dilate, so that the amount of 
 blood flowing through them is increased (Zudwig and Sczelkow). At the time that 
 the motor fibres are excited, so also are the vaso-dilator fibres, which lie in the 
 same nervous channels (§ 294, II). [Gaskell found that faradization of the nerve 
 of the mylo-hyoid muscle of the frog not only caused tetanus of the muscle, but 
 also dilatation of its blood vessel.] 
 
 Testing Individual Muscles. — In estimating the absolute force of the individual muscles or 
 groups of muscles in man, we must always pay particular attention to the physical relations, i. e., to 
 
 the arrangement of the levers, direction of the 
 Fig. 308. traction, degree of shortening, etc. (§ 306). Dy- 
 
 namometer. — The absolute force of certain groups 
 of muscles is very conveniently and practically 
 ascertained by means of a dynamometer (Fig. 308). 
 This instrument is very useful for testing the differ- 
 ence between the power of the. two arms in cases 
 of paralysis. The patient grasps the instrument in 
 his hand and an index registers the force exerted. 
 Quetelet has estimated the force of certain muscles 
 — the pressure of both hands of a man to be = 70 
 kilos.; while by pulling he can move double this 
 Dynamometer of Mathieu. weight. The force of the female hand is one- 
 
 third less. A man can carry more than double 
 his own weight; a woman about the half. Boys can carry about one- third more than girls. [Very 
 convenient dynamometers are made by Salter, of Birmingham, both for testing the strength of pull 
 and squeeze ; in testing the former, the instrument is held as an archer holds his bow when in the 
 act of drawing it, and the strength of pull is given by an index ; in the latter, another form of the 
 instrument is used. Large numbers of observations were made by means of these instruments by 
 Francis Galton, at the Health Exhibition, 1885.] 
 
 Amount of Work Daily. — In estimating the work done by a man, we have to consider, not 
 only the amount of work done at any one moment, but how often, time after time, he can succeed 
 in doing work. The mean value of the daily work of a man working eight hours a day is 10 
 (10.5 to 11 at most) kilogramme metres per second, i.e., a daily amount of work = 288,000 
 (300,000) kilogramme metres. 
 
 Modifying Conditions. — Many substances after being introduced into the body diminish, and 
 ultimately paralyze the production of work — -mercury, digital in, helleborin, potash salts, etc. Others 
 increase the muscular activity — veratrin (Rossbach), glycogen [caffein, and allied alkaloids], mus- 
 carin (Klug and Fr. H'dgyes"), kreatin and hypoxanthin; extract of meat rapidly restores the muscles 
 after fatigue (JToierl). [Those drugs which excite muscular tissue restore it after fatigue. Now 
 kreatin is a waste product of muscle, and beef tea and Liebig's extract of meat, perhaps, owe their 
 restorative qualities partly to these extractives.] 
 
 301. THE ELASTICITY OF MUSCLE.— Physical.— Every elastic body has its "natural 
 shape," i. e., its shape when no external force (tension or pressure) acts upon it so as to distort it. 
 Thus, the passive muscle has a " natural form." If, however, a muscle be extended in the course 
 of its fibres, the parts of the muscle are evidently pulled asunder. If the stretching be carried only 
 to a certain degree, the muscle, in virtue of its elasticity, will regain its natural form. Such a body 
 is said to possess " complete elasticity," i. e., after being stretched it regains exactly its original 
 
ELASTIC AFTER-EFFECT. 
 
 52? 
 
 shape. By the term " amount of elasticity " {modulus) is meant the weight (expressed in kilo- 
 grammes ) necessary to extend an elastic body I □ millimetre in diameter, its own length, without 
 the body breaking. Of course, many bodies are ruptured before this occurs. For a passive muscle 
 it is = 0.2734 ( Wundt) [that of bone = 2264 ( Wertheim), tendon = 1.6693, nerve = 1.0905, 
 the arterial walls = 0.0726 ( Wundt)~\. Thus the amount of elasticity of a passive muscle is small, 
 as it requires only a slight stretching force to extend it to its own length. It has, therefore, no great 
 amount of elasticity. The term " coefficient of elasticity " is applied to the fraction of the length 
 of an elastic body, to which it is elongated by the unit of weight applied to stretch it. It is large 
 in a passive muscle. If the tension be sufficiently great, the elastic body ruptures at last. The 
 •'carrying capacity" of muscular tissue, until it ruptures, is in the following ratios for youth, middle, 
 and old age, nearly 7:3:2. [Instead of the word "elasticity," Brunton suggests the use of 
 extensibility and retractibility, terms suggested by Marey, the one referable to the elongation on 
 the application of a weight, and the other to the shortening after its removal.] 
 
 Curve of Elasticity. — In inorganic elastic bodies, the line of elongation, or 
 the extension, is directly proportional to the extending weight ; in organic bodies, 
 and therefore in muscle, this is not the case, as the weight is continually increased 
 by equal increments — the muscle is less extended than at the beginning, so that 
 the extension is not proportional to the weight. If equal weights be added to a 
 scale pan attached to a piece of India-rubber, with a writing lever connected with 
 it, and writing its movements on a plate of glass that can be moved with the hand, 
 we get such a curve as in Fig. 309, while, if the same be done with the sartorius 
 of a frog, we get a result similar to Fig. 310. A straight line joins the apices 
 
 Fig. 309. 
 
 Fig. 310. 
 
 Fig. 311. 
 
 Fig. 309. — Curve of elasticity irom an inorganic body (India-rubber). Fig. 310. — Curve of elasticity from the sartorius 
 of a frog, obtained by adding equal increments of weight at A, B, C, etc. Fig. 311. — Curve of elasticity produced 
 by continuous extension and recoil of a frog's muscle ; o jr, abscissa before, x' ', after extension. 
 
 of the former, while the curve of elasticity is a hyperbola, or something near it, 
 in the latter case. 
 
 Elastic After-effect. — At the same time, after the first elongation, corres- 
 ponding to the extending weight, is reached, the muscle may remain for days, and 
 even weeks, somewhat elongated. This is called the "elastic after-effect" (§ 65). 
 [Marey attached a lever to a frog's muscle, and allowed to latter to record its 
 movements on a slowly revolving cylinder. To the lever was fixed a vessel into 
 which mercury slowly flowed. This extended the muscle, and when it had ceased 
 to elongate, the mercury was allowed slowly to run out again. The curve ob- 
 tained is shown in Fig. 311. The abscissse, o x and xf, indicate the position of 
 the writing style before and after the experiment, and we observe that x' is lower 
 than o x, so that the recoil is imperfect. There has been an actual elongation of 
 the muscle, so that the limit of its elasticity is exceeded. Although a frog's gas- 
 trocnemius may be loaded with 1500 grammes without rupturing it, 100 grammes 
 will prevent it regaining its original length.] 
 
 Method. — In order to test the elasticity of a muscle, fix it to a support provided with a gradu- 
 ated scale, and to the lower end of the muscle attach a scale pan, into which are placed various 
 weights, measuring on each occasion the corresponding elongation of the muscle thereby obtained 
 (Ed. Weber). In order to obtain the curve of elongation or extensibility, take as abscissse the 
 successive units of weight added and the elongation corresponding to each weight as ordinates. 
 Example from the hyoglossus of the frog : — 
 
528 
 
 ELASTICITY OF ACTIVE AND INTACT MUSCLES. 
 
 Weight in Grammes. 
 
 Length of the Muscle in 
 Millimetres. 
 
 Extension. 
 
 In Millimetres. 
 
 Percentage. 
 
 o-3 
 '•3 
 2 -3 
 3-3 
 4-3 
 5-3 
 
 24.9 
 30.0 
 323 
 
 33-4 
 34-2 
 34-6 
 
 5- 1 
 
 2-3 
 
 1.1 
 
 0.8 
 04 
 
 20 
 
 7 
 3 
 2 
 1 
 
 The elasticity of passive muscle is small, but very complete, and is com- 
 parable to that of a caoutchouc fibre. Small weights greatly elongate the muscle. 
 If the weights be uniformly increased there is not a uniform elongation; with 
 equal increments of weight, the greater the load, the increase in elongation always 
 becomes less ; or, to express it in another way, the amount of elasticity of the 
 passive muscle increases with its increased extension {Ed. Weber). 
 
 In inorganic bodies the curve of extension is a straight line, but in 
 organic bodies it more closely resembles a hyperbola ( Wertheim). The elas- 
 ticity of a passive, fatigued muscle does not differ essentially from that of a non- 
 fatigued muscle. 
 
 Muscles in the living body, and still in connection with their nerves and blood vessels, are more 
 extensible than excised ones. Muscles, when quite fresh, are elongated (within certain small limits 
 as regards the weight) at first with a uniformly increasing weight, to an extent proportional to the 
 latter, just as with an inorganic body. When heavy weights are used, we must be careful to take 
 into consideration the "elastic after-effect" (g 65). 
 
 The volume of a stretched muscle is slightly less than an unstretched one, similar to the con- 
 tracted (I 297, 2) and stiffened muscle (§ 295). 
 
 Dead muscles and muscles in rigor mortis have greater elasticity, i. e., they require a heavier 
 weight to stretch them than fresh muscles ; but, on the other hand,' the elasticity of dead muscles 
 is less complete, i. e., after they are stretched they only recover their original form within certain 
 limits. 
 
 Elasticity of Intact Muscles. — Normally, within the body, the muscles are 
 stretched to a very slight extent, as can be shown by the slight degree of retrac- 
 tion which occurs when the insertion of a muscle is divided. This slight degree 
 of extension, or stretching, is important. If this were not so, when a muscle is 
 about to contract, and before it could act upon a bone as a lever, it would have 
 to take in so much slack. The elasticity of muscles is manifested during the con 
 traction of antagonistic muscles. The position of a passive limb depends upon 
 the resultant of the elastic tension of the different muscle groups. 
 
 The elasticity of an active muscle is less than that of a passive muscle, 
 i. e., it is elongated by the same weight to a greater extent than a passive muscle. 
 For this reason, the active muscle, as can be shown in an excised contracted mus- 
 cle, is softer; the apparently great hardness manifested by stretched, contracted 
 muscles depends upon their tension. When the active muscle becomes fatigued 
 its elasticity is diminished (§, 304). 
 
 Method. — Ed. Weber took the hyoglossus muscle of a frog and suspended it vertically, noticing 
 its length when it was passive. It was then tetanized with induction shocks and its height again 
 noted. One after the other heavier weights were attached to it, and the length of the passive and 
 tetanized muscle observed for each weight. The extent to which the active loaded muscle shortened 
 from the position of the passive loaded muscle he called the " height of the lift " (or " Hubhdhe "). 
 The latter becomes less as the weight increases, and lastly, the tetanized muscle may be so loaded that 
 it cannot contract, i. e., the height of the lift is = O. 
 
 Weber's Paradox. — The case may occur where, when a muscle is so loaded that it cannot con- 
 tract when it is stimulated, it may even elongate. According to Wundt, even in this condition the 
 elasticity is not changed. [The usual explanation given is that, as the elasticity of a muscle is dimin- 
 ished during contraction, it is more extended with the same weight in the contracted as compared 
 
FORMATION OF HEAT IN AN ACTIVE MUSCLE. 529 
 
 with the passive or uncontracted state, so that a heavily-weighted muscle, when stimulated, may 
 elongate instead of shorten.] According to Wundt, however, there is no change in the elasticity 
 of the muscle. In these experiments, the length of the active loaded muscle is equal to the length 
 of the passive muscle when similarly loaded, minus the " height of the lift." 
 
 Poisons. — Potash causes shortening of a muscle with simultaneous increase of its elasticity. 
 Digitalin produces other changes with increased elasticity. Physostigmin increases it, while vera- 
 trin diminishes it, and interferes with its completeness (Rossbach and v. Anrep), and tannin makes 
 a muscle less extensible, but more elastic (Lewin). Ligature of the blood vessels produces at first 
 a decrease, and then an increase, of the elasticity ; section of the motor nerve diminishes the elas- 
 ticity (v. Anrep) ; heat increases it. 
 
 Eduard Weber concluded from his experiments that a muscle assumes two forms, the active and the 
 passive form. Each of these corresponds to a special natural form. The passive muscle is longer 
 and thinner — the active is shorter and thicker in form. The passive as well as the active muscle 
 strives to retain its form. If the passive muscle be set into activity, the passive rapidly changes into 
 the active form, in virtue of its elastic force. The latter is the energy which causes muscular work. 
 Schwann compared the force of an active muscle to a long, elastic, tense, spiral spring. Both can 
 lift the greatest w_eight only from that form in which they are most stretched. The more they 
 shorten, the less the weight which they can lift. 
 
 [Tonicity of Muscle (§ 362) — Sensibility of Muscle. — That muscles contain sensory fibres 
 is certain (jj 430). Section of inflamed muscles is painful, and during muscular cramp intense pain 
 is felt. Sachs discharged a reflex action by stimulating the central end of an intra-muscular nerve 
 filament in a frog, while stimulation of the central end of the phrenic nerve raises the blood 
 pressure (Muscular Sense, \ 430).] 
 
 [Uses of Elasticity. — As already pointed out, all muscles are slightly on the 
 stretch, so that no time is lost nor energy wasted in " taking in slack," as it were ; 
 but the elasticity also lessens the shock of the contraction, so that it is developed 
 gradually, and muscles are not liable to be torn from their attachments. The 
 muscular energy is transmitted to the mass to be moved through an elastic and 
 easily extensible body (muscle), whereby the shock due to the contraction is 
 lessened, but, as Marey has shown, the amount of work is thereby considerably 
 increased.] 
 
 302. FORMATION OF HEAT IN AN ACTIVE MUSCLE.— 
 
 After Bunzen, in 1805 (§ 209, 1, b), showed that during muscular activity heat is 
 evolved, v. Helmholtz proved that an excised frog's muscle, when tetanized for 
 two to three minutes, exhibited an increase of its temperature of 0.14 to 
 0.18 C. R. Heidenhain succeeded in showing an increase of o.ooi to 0.005° 
 C. for each single contraction. The heart is warmer during every systole (Marey). 
 
 [Method. — The rise in temperature of a frog's muscle may be estimated by placing the two 
 gastrocnemii of a frog's muscle on the two junctions of a thermo-electric pile, connected with a heat 
 galvanometer. Of course, when the two muscles are at the same temperature, the needle of the 
 galvanometer is stationary ; but, if one muscle be made to contract, or is tetanized, then an elec- 
 trical current is set up which deflects the needle (§ 208, B).] 
 
 The following facts have been ascertained with regard to the development of 
 heat : — 
 
 1. Relation to Work. — It bears a relation to the amount of work, (a) If 
 a muscle during contraction carries a weight which extends it again during rest, 
 no work is transferred beyond the muscle (§ 300). In this case all the chemi- 
 cal potential energy during this movement is converted into heat. Under 
 these circumstances the amount of heat evolved runs parallel with the amount of 
 work done, i.e., it increases as the load and the height increase up to a maximum 
 point, and afterward diminishes as the load is increased. The heat maximum is 
 reached with a less load sooner than the work maximum {Heidenhain). 
 
 (b) If, when the muscle is at the height of its contraction, the load be removed, 
 then the muscle has produced work referable to something outside itself; in this 
 case the amount of heat produced is less (A. Fick). The amount of work pro- 
 duced, and the diminished amount of heat formed, when taken together, repre- 
 sent the same amount of energy, corresponding to the law of the conservation of 
 energy. 
 34 
 
530 THE MUSCLE SOUND. 
 
 (c) If the same amount of work is performed in one case by many but small 
 contractions, and in another by fewer but larger contractions, then in the latter 
 case the amount of heat is greater {Heidenhain and Nawalichin). This shows 
 that larger contractions are accompanied by a relatively greater metabolism of the 
 muscular substance than small contractions, which is in harmony with practical 
 experience ; thus the ascent of a tower with steep high steps causes fatigue more 
 rapidly (metabolism greater) than the ascent of a more gentle slope with lower 
 steps. 
 
 (d) If the weighted muscle executes a series of contractions one after the other, 
 and at the same time does work, then the amount of heat it produces is greater 
 than when it is tetanic, and keeps a weight suspended. Thus the transition of 
 the muscle into a shortened form causes a greater production of heat than the 
 maintenance of this form. 
 
 2. Relation to Tension. — The amount of heat evolved depends upon the 
 tension of the muscle; it also increases as the muscular tension increases {Heide?i- 
 hairi). If the ends of a muscle be so fixed that it cannot contract, the maximum 
 of heat is obtained {Biclard). Such a condition occurs during tetanus, in which 
 condition the violently contracted muscles oppose each other, and very high tem- 
 peratures have been registered by Wunderlich (§ 213, 7), while the same is true 
 of animals that are tetanized {Leyden). Dogs kept in a state of tetanus by elec- 
 trical stimulation die, because their temperature rises so high (44 to 45° C), 
 that life no longer can be maintained {Richet). In addition to the formation of 
 heat, there is a considerable amount of acid and of alcoholic extractives produced 
 in the muscular tissue. 
 
 3. Relation to Stretching. — Heat is also evolved during the elongation or 
 relaxation of a contracted muscle, e.g., by causing a muscle to contract without 
 the addition of any weight, and loading it when it begins to relax, whereby heat 
 is produced {Steiner, Schmulewilsch and Westermari). 
 
 4. The formation of heat diminishes as the muscular fatigue increases. 
 
 5. In a muscle duly supplied with blood, the production of heat (as well as the 
 mechanical work) is far more active than in a muscle whose blood vessels are 
 ligatured or its blood stream cut off. Recovery takes place more rapidly and 
 completely after fatigue, while at the same time there is a new increase in the 
 production of heat {Meade Smith). { 
 
 The amount of work and heat in a muscle must always correspond to the transformation of an 
 equivalent amount of ch-mical energy. A greater part of this energy is manifested as work, the 
 greater the resistance that is offered to the muscular contraction. When the resistance is great, \ of 
 the chemical energy may be manifested as work, but when it is small, only a small part of it is so 
 converted. 
 
 It was stated that a nerve in action is ^5° C. warmer ( Valentin), but this is denied by v. Helm- 
 holtz and Heidenhain. 
 
 In man, if the muscles be stimulated with electricity or contracted voluntarily, the production of 
 heat may be detected through the skin (v. Ziemssen). The venous blood flowing from an actively- 
 contracting muscle is o.6° C. warmer than the arterial blood [Meade Smith). 
 
 303. THE MUSCLE SOUND.— Muscle Sound.— When a muscle con- 
 tracts, and is at the same time kept in a state of tension by the application of 
 sufficient resistance, it emits a distinct sound or tone, depending upon the inter- 
 mittent variations of tension occurring within it ( Wollaston). 
 
 Methods. — The muscle sound may be heard by placing the ear over the tetanically contracted 
 and tense biceps of another person; or we may insert the tips of our index fingers into our ears, 
 and forcibly contract the muscles of our arm ; or the sound of the muscles that close the jaw may 
 be heard by forcibly contracting them, especially at night when all is still, and when the outer ears 
 are closed. V. Helmholtz found that this tone coincides with the resonance tone of the ear, and he 
 thought that the vibrations of the muscles caused this resonance tone. The sound of an isolated 
 frog's muscle may be heard by placing one end of a rod in the ear, the other ear being closed. To 
 the other end of the rod is attached a loaded frog's muscle kept in a tetanic condition. The pitch 
 of the note, i. e., the number of vibrations, may be estimated by comparing the muscle sound with 
 that produced by elastic springs vibrating at a known rate. 
 
FATIGUE AND RECOVERY OF MUSCLE. 531 
 
 When a muscle contracts voluntarily, i. e., through the will, it makes 19.5 
 vibrations per second. We do not hear this very low tone, owing to the number 
 of vibrations per second being too few ; but what we actually hear is the first 
 overtone, with double the number of vibrations. The muscle sound has 19.5 
 vibrations, when the muscles of an animal are caused to contract, by stimulating 
 its spinal cord (v. Helmholtz), and also when the motor nerve trunk is excited by 
 chemical means {Bernstein). If, however, tetanizing induction shocks be applied 
 to a muscle, then the number of vibrations of the muscle sound corresponds exactly 
 with the number of vibrations of the vibrating spring or hammer of the induction 
 apparatus. Thus the tone may be raised or lowered by altering the tension of the 
 spring. 
 
 Loven found that the muscle sound was loudest when the weakest currents capable of producing 
 tetanus were employed. The sound corresponded to the number of vibrations of the octave just 
 below it in the scale. With stronger currents the muscle sound disappears, but it reappears with the 
 same number of vibrations as that of the interrupter of the induction apparatus, if s ill stronger 
 currents are used. 
 
 If the induction shocks be applied to the nerve, the sound is not so loud, but 
 it has the same number of vibrations as the interrupter. With rapid induction 
 shocks, tones caused by 704 {Loven) and 1000 vibrations per second have been 
 produced {Bernstein), 
 t The first heart sound is partly muscular (§ 53). 
 
 (^ The muscle sound is regarded as a sign that tetanus is due to a series of single variations of the 
 density of the muscle (j! 298, III). 
 
 304. FATIGUE AND RECOVERY OF MUSCLE.— Fatigue.— By 
 
 the term fatigue is meant that condition of diminished capacity for work which is 
 produced in a muscle by prolonged activity. This condition is accompanied in 
 the living person with a peculiar feeling of lassitude, which is referred to the 
 muscles. A fatigued muscle rapidly recovers in a living animal, but an excised 
 muscle recovers only to a slight extent {Ed. Weber, Valentin). 
 
 [Waller recognizes a certain resemblance between experimental fatigue and the natural decline 
 of excitability at death, in disease, and in poisoning.] 
 
 The cause of fatigue is, probably, partly due to the accumulation of decomposi- 
 tion products — "fatigue stuffs" — in the muscular tissue, these products being 
 formed within the muscle itself during its activity. They are phosphoric acid, 
 either free or in the form of acid phosphates, acid potassium phosphate (§ 294), 
 glycerin-phosphoric acid (?), and C0 2 . If these substances be removed from a 
 muscle, by passing through its blood vessels an indifferent solution of common 
 salt (0.6 per cent.), or a weak solution of sodium carbonate [or a dilute solution 
 of permanganate of potash {Kroneckerj\, the muscle again becomes capable of 
 energizing {J. Ranke, 1863). The using up of O by an active muscle favors 
 fatigue {v. Pettenkofer and v. Voit). The transfusion of arterial blood (not of 
 venous — Bichat) removes the fatigue {Ranke, Kronecker), probably by replacing 
 the substances that have been used up in the muscle. Conversely, an actively- 
 energizing muscle may be rapidly fatigued by injecting into its blood vessels a 
 dilute solution of phosphoric acid, of acid potassium phosphate, or dissolved 
 extract of meat {Kemmerich). A muscle fatigued in this way absorbs less O, and 
 when so fatigued it evolves only a small amount of acids and C0 2 . The condi- 
 tions which lead up to fatigue are connected with considerable metabolism in the 
 muscular tissue. 
 
 [Zabludowski found that if a frog's muscles be systematically stimulated by maximum induction 
 shocks until they cease to contract, massage, or kneading them rapidly, restored their excitability, 
 while simple rest had little effect. Massage acts on the nerves, but chiefly by favoring the blood 
 and lymph streams which wash out the waste products from the muscle. A similar result obtains 
 in man, so that the ancient Roman practice of " rubbing" after a bath and after exercise was one 
 conducive to restoratijn of the power of the muscles.] 
 
532 MODIFYING CONDITIONS. 
 
 Modifying Conditions. — In order to obtain the same amount of work from 
 a fatigued muscle, a much more powerful stimulus must be applied to it than to a 
 fresh one. A fatigued muscle is incapable of lifting a considerable load, so that 
 its absolute muscular force is diminished. If, during the course of an experiment, 
 an excised muscle be loaded with the same weight, and if the muscle be stimulated 
 at regular intervals with maximal stimuli (strong induction shocks), contraction 
 after contraction, gradually and regularly diminishes in height, the decrease being 
 a constant fraction of the total shortening. Thus the fatigue curve is represented 
 by a straight line [i. e., a straight line will touch the apices of all the contractions]. 
 The more rapidly the contractions succeed each other, the greater is the fall in the 
 height of the contraction [i. <?., if the interval between the contractions be short, 
 the fatigue curve falls rapidly toward the abscissa], and conversely. After a cer- 
 tain number of contractions, an excised muscle becomes exhausted. 
 
 This result occurs whether the stimuli are applied at short or long intervals 
 {Kronecker), and a similar result is obtained with submaximal stimuli ( Tiegel). 
 A fatigued muscle contracts more slowly than a fresh one, while the latent period 
 is also longer during fatigue (p. 518). The fatigued muscle is said to be more 
 extensible {Donders and van Mansvelt). If a muscle be so loaded that when it 
 contracts it cannot lift the load, fatigue occurs even to a greater extent than when 
 the load is such that the muscle can lift it {Leber). The metabolism and the forma- 
 tion of acid are greater in a contracted muscle kept on the stretch, than in a contracted 
 muscle allowed to shorten {Heidenhain): If a muscle contract, but is not required 
 to lift any load, it becomes fatigued only very gradually. If a muscle be loaded 
 only during contraction, and not during relaxation, it is fatigued more slowly than 
 when it is loaded during both phases ; and the same is true when a muscle has to 
 lift its load only during the course of its contraction, instead of at the beginning 
 of the contraction. Loads may be suspended to perfectly passive muscles without 
 fatiguing them {Earless, Leber). 
 
 [Signs of Fatigue. — In the record of the series of contractions (1) the con- 
 tractions become more prolonged, (2) they decrease in extent, (3) but Waller 
 finds that a skeletal muscle exhibits after a period of rest a " staircase " character 
 of its contractions just like the heart (§ 57).] 
 
 [While an excised frog's muscle is fairly rapidly exhausted by single opening induction shocks 
 at intervals of one second, human muscle in its normal relations may be almost indefinitely so 
 treated, and there is no change in the record or any sensation of fatigue, and Waller regards this as 
 favoring the view that the " fatigue consequent upon prolonged muscular exertion is normally cen- 
 tral rather than peripheral." Such results, however, do not harmonize with those of Zabludowski 
 on the kneading of muscles or massage. Probably there are two factors, one central the other periph- 
 eral.] 
 
 Blood Supply. — If the arteries of a mammal be ligatured, stimulation of the motor nerves pro- 
 duces complete fatigue after 120 to 240 contractions (in two to four minutes), but direct muscular 
 stimulation still causes the muscles to contract. In both cases the fatigue curve is in the form of 
 a straight line. If the blood supply to a mammalian muscle be normal, on stimulating the motor 
 nerve the muscular contractions at first increase in height and then fall, their apices forming a straight 
 line {Rossbach and Harteneck). In persons who have used their muscles until fatigue sets in, it is 
 found that at the beginning the nerves and muscles react better to galvanic and faradic stimulation, 
 but afterward always to a less degree (Orschanski). According to v. Kries, a muscle tetanized and 
 fatigued with maximal stimuli behaves like a fresh muscle tetanized with submaximal stimuli ; both 
 show an incomplete transition from the passive to the active condition. 
 
 [Relation of End Plates. — Muscle is fatigued far more rapidly than nerve, and the fatigue begins 
 in the muscle and not in the nerve, and it seems to be the weakest link in the chain between nerve 
 and muscle which is affected during excessive action, viz., the motor end plate ( Waller). In a 
 nerve its conductivity is sooner affected by fatigue than its direct excitability. Waller finds that 
 afler death " the excitability of a nerve persists when its action upon muscle has ceased, such muscle 
 being still excitable by direct stimulation." Some link in the chain is obviously affected, and it is 
 perhaps the end plates.] 
 
 [Action of Drugs on Fatigue. — Waller finds, in a frog poisoned with veratrin, that if the mus- 
 cles be stimulated electrically the characteristic elongation of the descent ({! 298) gradually disap- 
 pears, but reappears after a period of rest. In this respect strychnin in its action on the spinal cord 
 behaves precisely the same as veratrin on muscle, viz., its effect is dissipated by action and- 
 
MECHANISM OF THE BONES AND JOINTS. 
 
 533 
 
 restored by rest.] Curara and the ptomaines cause an irregular course of the fatigue curve ( Guareschi 
 arid Mosso). 
 
 [If strychnin be injected into a frog, and the sciatic nerve on one side divided after the strychnin 
 tetanus has lasted for a time, the leg muscles of the side with the nerve undivided exhibit signs of 
 fatigue, as shown by direct stimulation of the muscles of both legs when a curve similar to Fig. 312 
 is obtained. The higher one is the non-fatigued, the lower that of the side with the nerve undi- 
 vided {Waller).} 
 
 Recovery from the condition of fatigue is promoted by passing a constant elec- 
 trical current through the entire length of the muscle (Heidenhairi), also by inject- 
 ing fresh arterial blood into its blood vessels, or by very small doses of veratrin 
 [or permanganate of potash] and by rest. 
 
 If the muscle of an intact animal be stimulated continuously (fourteen days or thereby), until 
 complete fatigue occurs, the muscular fibres become granular and exhibit a wax-like degeneration. 
 The transverse striation is still visible as long as the sarcous substance is in large masses, but as soon 
 as it breaks up into small pieces the transverse striation disappears completely ( O. Roth). 
 
 305. MECHANISM OF THE BONES AND JOINTS.— Bones 
 
 exhibit in the inner architecture of their spongiosa an arrangement of their 
 lamellae and spicules which represents the static result of those forces— pressure 
 and traction — which act on the developing bone. They are so arranged that, 
 
 Fig. 312. 
 
 Curves obtained by direct stimulation of the gastrocnemius ot a frog poisoned with strychnin ( JValler), the 
 sciatic nerve divided on one side (upper curve) and not on the other (lower or fatigue curve). 
 
 with the minimum of material, they afford the greatest resistance as a supporting 
 structure or framework {H. v. Meyer, Culmann, Jul. Wolff). 
 
 I. The joints permit the freest movements of one bone upon another [such as exist between the 
 extremities of the bones of the limbs. In other cases, sutures are formed, which, while permitting 
 no movement, allow the contents of the cavity which they surround to enlarge, as in the case of the 
 cranium.] The articular end of a fresh bone is covered with a thin layer or plate of hyaline car- 
 tilage, which in virtue of its elasticity moderates any shocks or impulses communicated to the bones. 
 The surface of the'articular cartilage is perfectly smooth, and facilitates an easy gliding movement 
 of the one surface upon the other. At the outer boundary line of the cartilage, there is fixed the cap- 
 sule of the joint, which encloses the articular ends of the bones like a sac. The inner surface of 
 the capsule is lined by a synovial membrane, which secretes the sticky, semi-fluid, synovia, moisten- 
 ing the joint. The outer surface of the capsule is provided at various parts with bands of fibrous 
 tissue, some of which strengthen it, while others restrain or limit the movements of the joint. Some 
 osseous processes limit the movements of particular joints, e. g., the coronoid process of the ulna, 
 which permits the forearm to be flexed on the upper arm only to a certain extent ; the olecranon, 
 which prevents over-extension at the elbow joint. The joint surfaces are kept in apposition— ( 1 ) 
 by the adhesion of the synovia-covered smooth articular surfaces; (2) by the capsule and its fibrous 
 bands ; and (3) by the elastic tension and contraction of the muscles. 
 
 [Structure of Articular Cartilage.— The thin layer of hyaline encrusting cartilage is fixed by 
 an irregular surface upon the corresponding surface of the head of the bone. In a vertical section 
 through the articular cartilage of a bone, which has been softened in chromic or other suitable acid, 
 we observe that the cartilage cells are flattened near the free surface of the cartilage, and their long 
 axes are parallel to the surface of the joint ; lower down, the cells are arranged in irregular groups, 
 
534 HINGE AND SCREW-HINGE JOINTS. 
 
 and further down still, nearer the bone, in columns or rows, whose long axis is in the long axis of 
 the bone. These rows are produced by transverse cleavage of pre existing cells. In the upper 
 two-thirds or thereby the matrix of the cartilage is hyaline, but in the lower third, near the bone, 
 the matrix is granular and sometimes fibrillated. This is the calcified zone, which is impregnated 
 with lime salts, and sharply defined by a nearly straight line from the hyaline zone above it, and by 
 a bold wavy line from the osseous head of the bone.] 
 
 Synovial Membrane. — Synovial membrane consists of bundles of delicate connective tissue ' 
 mixed with elastic tissue, while on its inner surface it is provided with folds, some cf which contain 
 fat, and others blood vessels (synovial villi). The inner surface is lined with endoth. lium. The 
 intra-capsular ligaments and cartilages are not covered by the synovial membrane, nor are they 
 covered by endothelium. The synovia is a colorless, stringy, alkaline fluid, with a chemical com- 
 position closely allied to that of transudations, with this difference, that it contains much mucin, 
 together with albumin and traces of fat. Excessive movement diminishes its amount, makes it more 
 inspissated, and increases the mucin, but diminishes the salts. 
 
 Joints may be divided into several classes, according to the kind of movement 
 which they permit : — 
 
 i. Joints with movement around one axis . (a) The Ginglymus, or Hinge Joint. — The pne 
 articular surface represents a portion of a cylinder or sphere, to which the other surface is adapted 
 by a corresponding depression, so that, when flexion or extension of the joint takes place, it moves 
 only on one axis of the cylinder or sphere. The joints of the fingers and toes are hinge joints of 
 this description. Lateral ligaments, which prevent a lateral displacement of the articular surfaces, 
 are always present. 
 
 The Screw-hinge Joint is a modification of the simple hinge form (Langer, Henke), c. g., the 
 humcro-uinar articulation. Strictly speaking, simple flexion and extension do not take place at the 
 elbow joint, but the ulna moves on the capitellum of the humerus like a nut on a bolt ; in the 
 right humerus the screw is a right spiral, in the left, a left spiral. The ankle joint is another ex- 
 ample ; the nut or female screw is the tibial surface, the right joint is like a left-handed screw, the 
 left the reverse. (b) The pivot joint (rotatoria), with a cylindrical surface, e.g., the joint between 
 the atlas and the axis, the axis of rotation being around the odontoid process of the axis. In the 
 acts of pronation and supination of the forearm at the elbow joint, the axis of rotation is from 
 the middle of the cotyloid cavity of the head of the radius to the styloid process of the ulna. The 
 other joints which assist in these movements are above the joint between the circumferential part of 
 the head of the radius and the sigmoid cavity of the ulna, and below the joint between the sigmoid 
 cavity of the radius which moves over the rounded lower end of the ulna. 
 
 2. Joints with movements around two axes. — (a) Such joints have two unequally curved surfaces 
 which intersect each other, but which lie in the same direction, e. g., the atlanto occipital joint, or 
 the wrist joint, at which lateral movements, as well as flexion and extension, take place, {b) Joints 
 with curved surfaces, which intersect each other, but which do not lie in the same direction. To 
 this group belong the saddle-shaped articulations, whose surface is concave in one direction, but 
 convex in the other, e. g.. the joint between the metacarpal bone of the thumb and the trapezium. 
 The chief movements are — (i) flexion and extension, (2) abduction and adduction. Further, to a 
 limited degree, movement is possible in all other directions ; and, lastly, a pyramidal movement can 
 be described by the thumb. 
 
 3. Joints with movement on a spiral articular surface {spiral joints') , e. g., the knee joint (Good- 
 sir). The condyl of the femur, curved from before backward, in the antero-posterior section of its 
 articular surface, represents a spiral (Ed. Weber), whose centre lies nearer the posterior part of the 
 condyle, and whose radius vector increases from behind, downward and forward. Flexion and 
 extension are the chief movements. The strong lateral ligaments arise from the condyles of the 
 femur corresponding to the centre of the spiral, and are inserted into the head of the fibula and in- 
 ternal condyle of the tibia. When the knee joint is strongly flexed, the lateral ligaments are relaxed 
 — they become tense as the extension increases ; and when the knee joint is fully extended, they act 
 quite like tense bands which secure the lateral fixation of the joint. Corresponding to the spiral 
 form of the articular surface, flexion and extension do not take place around one axis, but the axis 
 moves continually with the point of contact; the axis moves also in a spiral direction. The greatest 
 flexion and extension covers an angle of about 145 . The anterior crucial ligament is more tense 
 during extension, and acts as a check ligament for too great extension, while the posterior is more 
 tense during flexion and is a check ligament for too great flexion. The movements of extension 
 and flexion at the knee are further complicated by the fact that the joint has a screw-like move- 
 ment, in that during the greater extension the leg moves outward. Hence, the thigh, when the leg 
 is fixed, must be rotated outward during flexion. Pronation and supination take place during the 
 greatest flexion to the extent of 41 ° (Albert) at the knee joint, while with the greatest extension it 
 is nil. It occurs because the external condyle of the tibia rotates on the internal. In all positions 
 during flexion the crucial ligaments are fairly and uniformly tense, whereby the articular surfaces are 
 pressed against each other. Owing to their arrangement, during increasing tension of the anterior 
 ligament (extension), the condyles of the femur must roll more on to the anterior part of the articular 
 
ARRANGEMENT AND USES OF THE MUSCLES. 535 
 
 surface of the tibia, while by increasing tension of the posterior ligament (flexion) they must pass 
 more backward. 
 
 4. Joints with the axis of rotation round one fixed point. — These are the freely movable 
 arthrodial joints. The movements can take place around innumerable axes, which all intersect 
 each other in the centre of rotation. One articular surface is nearly spherical, the other is cup- 
 shaped. The shoulder and hip joints are typical "ball and socket joints." We may represent 
 the movements as taking place around three axes, intersecting each other at right angles. The 
 movements which can be performed at these joints may be grouped as : (1) pendulum-like move- 
 ments in any plane; (2) rotation round the long axis of the limb; and (3) circumscribing movements 
 [circumduction], such as are made round the circumference of a sphere; the centre is in the point 
 of rotation of the joint, while the circumference is described by the limb itself. 
 
 Limited arthrodial joints are ball joints with limited movements, and where rotation on the 
 long axis is wanting, e.g., the metacarpophalangeal joints. 
 
 5. Rigid joints or amphiarthroses are characterized by the fact that movement may occur in 
 all directions, but only to a very limited extent, in consequence of the very tough and unyielding 
 external ligaments. Both articular surfaces are usually about the same size, and are nearly plane 
 surfaces, e.g., the articulations of the carpal and the tarsal bones. 
 
 II. Symphyses, synchondroses, and syndesmoses unite bones without the formation of a 
 proper articular cavity, are movable in all directions, but only to the very slightest extent. Physio- 
 logically, they are closely related to amphiarthrodial joints. 
 
 III. Sutures unite bones without permitting any movement. The physiological importance of 
 the suture is that the bones can still grow at their edges, which thus renders possible the distention 
 of the cavity enclosed by the bones {Herm. v. Meyer). 
 
 306. ARRANGEMENT AND USES OF THE MUSCLES.— The 
 
 muscles form 45 per cent, of the total mass of the body, those of the right side 
 being heavier than those on the \zit{Ed. Weber). Muscles may be arranged in 
 the following groups, as far as their mechanical actions are concerned : — 
 
 A. Muscles without a definite origin and insertion : — 
 
 1. The hollow muscles surrounding globular, oval, or irregular cavities, such 
 as the urinary bladder, gall bladder, uterus, and heart ; or the walls of more or 
 less cylindrical canals (intestinal tract, muscular gland ducts, ureters, Fallopian 
 tubes, vasa deferentia, blood vessels, and lymphatics). In all these cases the 
 muscular fibres are arranged in several layers, e. g. , in a longitudinal and a circular 
 layer, and sometimes also in an oblique layer. All these layers act together, and 
 thus diminish the cavity. It is inadmissible to ascribe different mechanical effects 
 to the different layers, e. g., that the circular fibres of the intestine narrow it, while 
 the longitudinal dilate it. Both sets of fibres rather seem to act simultaneously, 
 and diminish the cavity by making it narrower and shorter at the same time. 
 The only case where muscular fibres may act in partially dilating the cavity is / 
 when, owing to pressure from without or from partial contraction of some fibres,' 
 a fold, projecting into the lumen, has been formed. When the fibres, necessarily 
 stretching across the depression thereby produced, contract, they must tend to \ 
 undo it, i. e., enlarge the cavity. The various layers are all innervated from the ] 
 same motor source, which supports the view of their conjoint action. ' 
 
 2. The sphincters surround an opening or a short canal, and by their action j 
 they either constrict or close it, e.g., sphincter papillae, palpebrarum, oris, pylori, 
 ani, cunni, urethrse. 
 
 B. Muscles with a definite origin and insertion :— 
 
 1. The origin is completely fixed when the muscle is in action. The I 
 course of the muscular fibres, as they pass to where they are inserted, permits of I 
 the insertion being approximated in a straight line toward their origin during 
 contraction, e.g., the attolens, attrahens, and retrahentes of the outer ear, and 
 the rhomboidei. Some of these muscles are inserted into soft parts which neces- 
 sarily must follow the line of traction, e.g., the azygos uvulae, levator palati mollis; ( 
 and most of the muscles which arise from bone and are inserted into the skin, such [ 
 as the muscles of the face, styloglossus, stylopharyngeus, etc. 
 
 2. Both Origin and Insertion Movable. — In this case the movements of | 
 both points are inversely as the resistance to be overcome. The resistance is often I 
 voluntary, which may be increased either at the origin or insertion of the muscle. 
 
536 VARIOUS KINDS OF LEVERS ACTED ON BY MUSCLES. 
 
 Thus, the sternocleidomastoid may act either as a depressor of the head or as an 
 elevator of the chest ; the pectoralis minor may act as an adductor and depressor 
 of the shoulder, or as an elevator of the 3d to 5 th ribs (when the shoulder girdle 
 is fixed). 
 
 3. Angular Course. — Many muscles having a fixed origin are diverted from 
 their straight course ; either their fibres or their tendons may be bent out of the 
 straight course. Sometimes the curving is slight, as in the occipito-frontalis and 
 levator palpebrae superioris, or the tendon may form an angle round some bony 
 process, whereby the muscular traction acts in quite a different direction, i. e., as 
 if the muscle acted directly from this process upon its point of insertion, e.g., the 
 obliquus oculi superior, tensor tympani, tensor veli palatini, obturator internus. 
 
 4. Many of the muscles of the extremities act upon the. long bones as upon 
 levers : (a) Some act upon a lever with one arm, in which case the insertion 
 of the muscle (power) and the weight lie upon one side of the fulcrum or point of 
 support, e.g., biceps, deltoid. The insertion of (or power) often lies very close 
 to the fulcrum. In such a case, the rapidity of the movement at the end of the 
 lever is greatly increased, but force is lost [i. e., what is gained in rapidity is lost 
 in power]. This arrangement has this advantage, that, owing to the slight con- 
 traction of the muscle, little energy is evolved, which would be the case had the 
 muscular contraction been more considerable (§ 300, I, 3). (6) The muscles act 
 upon the bones as upon a lever with two arms, in which case the power (insertion 
 of the muscle) lies on the other side of the fulcrum opposite to the weight, e.g., 
 the triceps and muscles of the calf. In both cases, the muscular force necessary 
 to overcome the resistance is estimated by the principles of the lever : equilibrium 
 is established when the static moments (= product of the power in its vertical 
 distance from the fulcrum) are equal ; or when the power and weight are inversely 
 proportional, as their vertical distance from the fulcrum. 
 
 [The Bony Levers. — All the three orders of levers are met with in the body. Indeed, in the 
 elbow joint all the three orders are represented. The annexed scheme shows the relative positions 
 
 of P, W and F (Fig. 313). The 1st order is represented by such 
 Fig. 313. a movement as nodding the head, the 2d by raising the body on 
 
 the tiptoes by the muscles of the calf, and the 3d by the action 
 of the biceps in raising the forearm. At the elbow joint the first 
 
 (1) order is illustrated by extending the flexed forearm on the upper 
 arm, as in striking a blow on the table, where the triceps attached 
 to the olecranon is the power, the trochlea the fulcrum, and the 
 hand the weight. If the hand rest on the table and the body be 
 
 (2) rised on it, then the hand is the fulcrum, while the triceps is the 
 power raising the humerus and the parts resting on it (W). The 
 third order has already been referred to in flexing the forearm.] 
 
 ,.. . Direction of Action. — It is most important to observe the 
 
 W^^^^™""T> A "' direction in which the muscular force and weight act upon the 
 
 lever arm. Thus, the direction may be vertical to the lever in one 
 
 The three orders of levers. position, while after flexion it may act obliquely upon the lever. 
 
 The static moment of a power acting obliquely on the lever arm is 
 
 obtained by multiplying the power with the power acting in a direction vertical to the point of 
 
 rotation. , 
 
 Examples. — In Fig. 314, I,|B x presents the humerus, and x Z the radius ; Ay, the direction 
 of the traction of the biceps. If the biceps acts at a right angle only, as by lifting horizontally a 
 weight (P) lying on the forearm or in the hand, then the power of the biceps (= A) is obtained 
 from the formula, Ay x = P x Z, i.e., A = (P x Z) : y x. It is evident that, when the radius is 
 depressed to the position x C, the result is different ; then the force of the biceps = Aj = (P! v x) ; 
 x. In Fig. 314, II, TF is the tibia, F, the ankle joint, MC, the foot in a- horizontal position. 
 The power of the muscles of the calf (= a) necessary to Equalize a force,/, directed from below 
 against the anterior part of the foot, would be a = (p M F) : F C. If the foot be altered to the 
 position, R S, the force of the muscles of the calf would thefi be a 1 = (p 1 MF) : F C. 
 
 In muscles also, which, like the coraco-brachialis, are stretched over the angle 
 of a hinge, the same result obtains. 
 
 In Fig. 314, III, H E is the humerus, E, the elbow joint, E R, the radius, B R, the coraco- 
 
 • 
 
 F 
 
 
 % 
 
 w 
 
 A 
 
 
 p 
 
 F 
 
 • 
 
 
 t 
 
 A 
 
 w 
 
 
 p 
 
 • 
 
 
 k 
 
 F 
 
VARIOUS KINDS OF LEVER ACTION OF MUSCLES. 
 
 537 
 
 brachialis. Its moment in this position is = A, b E. When the radius is raised to E Rj, then it is 
 = A,jE, We must notice, however, that BR,<BR. Hence, the absolute muscular force 
 must be less in the flexed position, because every muscle, as it becomes shorter, lifts less weight. 
 What is lost in power is gained by the elongation of the lever arm. 
 
 5. Many muscles have a double action ; when contracted in the ordinary 
 way they execute a combined movement, e.g., the biceps is a flexor and supinator 
 of the forearm. If one of these movements be prevented by the action of other 
 muscles, the muscle takes no part in the execution of the other movement. 
 
 If the forearm be strongly pronated and flexed in this position, the biceps takes no part therein ; 
 or, when the elbow joint is rigidly supinated, only the supinator brevis acts, not the biceps. The 
 muscles of mastication are another example. The masseter elevates the lower jaw, and at the 
 same time pulls it forward. If the depressed jaw, however, be strongly pulled backward when the 
 jaw is raised, the masseter is not concerned. The temporal muscle raises the jaw, and at the same 
 time pulls it backward. If the depressed jaw be raised after being pushed forward, then the tem- 
 poral is not concerned in its elevation. 
 
 6. Muscles acting on two or more joints are those which in their course 
 from their origin to their insertion pass over two or more joints. Either the 
 
 Scheme of the action of muscles on bones. 
 
 tendons may deviate from a straight course, e.g. , the extensors and flexors of the 
 fingers and toes, as when the latter are flexed ; or the direction is always straight, 
 e.g., the gastrocnemius. The muscles of this group present the following points 
 of interest : (a) The phenomenon of so-called " active insufficiency " {Hueter, 
 Jlenke). If the position of the joints over which those muscles pass be so altered 
 that their origin and insertion come too near each other, the muscle may require 
 to contract so much before it can act on the bones attached to it, that it cannot 
 contract actively any further than to the extent of the shortening from which it 
 begins to be active, e.g. , when the knee joint is bent the gastrocnemius can no 
 longer produce plantar flexion of the foot, but the traction on the tendo Achilles 
 is produced by the soleus. (3) " Passive insufficiency" is shown by many- 
 jointed muscles under the following circumstances : In certain positions of the 
 joint, a muscle may be so stretched that it may act like a rigid strap, and thus 
 limit or prevent the action of other muscles, e.g., the gastrocnemius is too short 
 to permit complete dorsal flexion of the foot when the knee is extended. The 
 long flexors of the leg, arising from the tuber ischii, are too short to permit com- 
 plete extension of the knee joint when the hip joint is flexed at an acute angle. 
 
538 GYMNASTICS, MASSAGE AND CHANGES IN MUSCLE. 
 
 The extensor tendons of the fingers are too short to permit of complete flexion 
 of the joints of the fingers when the hand is completely flexed. 
 
 7. Synergetic muscles are those which together subserve a certain kind of 
 movement, e.g., the flexors of the leg, the muscles of the calf, and others. The 
 abdominal muscles act along with the diaphragm in diminishing the abdomen 
 during straining, while the muscles of inspiration or expiration, even the different 
 origins of one muscle, or the two bellies of a biventral muscle, may be regarded 
 from the same point of view. 
 
 Antagonistic muscles {Galen) are those which, during their action, have ex- 
 actly the opposite effect of other muscles, e.g., flexors and extensors — pronators 
 and supinators — adductors and abductors — elevators and depressors — sphincters 
 and dilators — inspiratory and expiratory. 
 
 When it is necessary to bring the full power of our muscles into action, we 
 quite involuntarily bring them beforehand into a condition of the greatest tension, 
 as a muscle in this condition is in the most favorable position for doing work 
 (§300, I, 3 — Schwann). Conversely, when we execute delicate movements requir- 
 ing little energy, we select a position in which the corresponding muscle is already 
 shortened. 
 
 All the fasciae of the body are connected with muscles, which, when they contract, alter the ten- 
 sion of the former, so that they are, in a certain sense, aponeuroses or tendons of the latter (JC. 
 Bardeleben). [For the importance of muscular movements and those of the fascia; in connection 
 with the movements of the lymph, see \ 201.] 
 
 307. GYMNASTICS; MOTOR PATHOLOGICAL VARIATIONS.— Gymnastic 
 exercise is most important for the proper development of the muscles and motor power, and it 
 ought to be commenced in both sexes at an early age. Systematic muscular activity increases the 
 volume of the muscles, and enables them to do more work. The amount of blood is increased 
 with increase in the muscular development, while at the same time the bones and ligaments become 
 more resistant. As the circulation is more lively in an active muscle, gymnastics favor the circula- 
 tion, and ought to be practice!, especially by persons of sedentary habits, who are apt to suffer 
 from congestion of the blood in the abdominal organs {e.g., haemorrhoids), as it favors the move- 
 ment of the tissue juices \\ 201]. An active muscle also uses more O and produces more C0 2 , so 
 that respiration is also excited. The total increase of the metabolism gives rise to the feeling of 
 well-being and vigor, diminishes abnormal irritability, and dispels the tendency to fatigue. The 
 whole body becomes firmer and specifically heavier {Jager). 
 
 By Ling's, or the Swedish system, a systematic attempt is made to strengthen certain weak 
 muscles, or groups of muscles, whose weakness might lead to the production of deformities These 
 muscles are exercised systematically by opposing to them resistances, which must either be over- 
 Gome, or against which the patient must strive by muscular action. 
 
 Massage, which consists in kneading, pressing, or rubbing the muscles, favors the blood stream ; 
 hence, this system may be advantageously used for such muscles as are so weakened by disease that an 
 independent treatment by means of gymnastics cannot be adopted. [The importance of massage 
 as a restorative practice in getting rid of the waste products of muscular activity has been already 
 referred to (§ 304). It is much practiced on the Continent.] 
 
 Disturbances of the normal movements may partly affect the passive motor organs {e.g., the 
 bones, joints, ligaments, and aponeuroses), or the active organs (muscles with their tendons, and 
 motor nerves). 
 
 Passive Organs — Fractures, caries and necrosis, and inflammation of the bones, which make 
 movements painful, influence or even make movement impossible. Similarly, dislocations, relaxa- 
 tion of the ligaments, arthritis, or anchylosis interfere with movement. Also curvature of bones, 
 hyperostosis or exostosis; lateral curvature of the vertebral column (Scoliosis), backward angular 
 curvature (Kyphosis), or forward curvature (Lordosis). The latter interfere with respiration. 
 In the lower extremities, which have to carry the weighl of the body, genu valgum may occur in 
 flabby, tall, rapidly-growing individuals, especially in some trades, e.g., bakers. The opposite 
 form, genu varum, is generally a result of rickets. Flat foot depends upon a depression of the 
 arch of the foot, which then no long«r rests upon its three points of support. Its causes seem to be 
 similar to those of genu valgum. The ligaments of the small tarsal joints are stretched, and the long 
 axis of the foot is usually directed outward ; the inner margin of the foot is more turned to the ground, 
 while pain in the foot and malleoli make walking and standing impossible. Club foot (Talipes 
 varus) in which the inner margin of the foot is raised, and the point of the toes is directed inward 
 and downward, depends upon imperfect development during foetal life. All children are born 
 with a certain very slight degree of bending of the foot in this direction. Talipes equinus, in 
 which the toes, and T. calcaneus, in which the heel touches the ground, usually depend upon 
 
STANDING. 539 
 
 contracture of the muscles causing these positions of the foot, or upon paralysis of the antago- 
 nistic muscles. 
 
 Rickets and Osteomalacia. — If the earthy salts be withheld from the food, the bones gradually 
 undergo a change ; they become thin, translucent, and may even bend under pressure. In certain 
 persistent defects of nutrition, the lime salts of the food are not absorbed, giving rise to rachitis, 
 or rickets, in children. If fully-formed bones lose their lime salts to the extent of yi to "^ (halis- 
 terisis), they become brittle and soft (osteomalacia). This occurs to a limited extent in old age. 
 
 Muscles. —The normal nutrition of muscle is intimately dependent on a proper supply of sodium 
 chloride and potash salts in the food, as these form integral parts of the muscular tissue (JfCemmerich, 
 Forster). Besides the atrophic changes which occur in the muscles when these substances are 
 withheld, there are disturbances of the central nervous system and digestive apparatus, and the 
 animals ultimately die. The condition of the muscles during inanition is given in $ 237. If mus- 
 cles and bones be kept inactive they tend to atrophy (j! 244). In atrophic muscles, and in cases of 
 anchylosis, there is an enormous increase, or " atrophic proliferation," of the muscle corpuscles, 
 which takes place at the expense of the contractile contents (Cohn/ieim). A certain degree of mus- 
 cular atrophy takes place in old age. The uterus, after delivery, undergoes a great decrease in 
 size and weight — from 1000 to 350 grammes — due chiefly to the diminished blood supply to the 
 organ. In chronic lead poisoning, the extensors and interossei chiefly undergo atrophy. Atrophy 
 and degeneration of the muscles are followed by shortening and thinning of the bones to which the 
 muscles are attached. 
 
 Section and paralysis of the motor nerves cause palsy of the muscle, thus rendering them 
 inactive, and they ultimately degenerate. Atrophy also occurs after inflammation or softening of 
 the multipolar nerve cells in the anterior horn of the gray matter of the spinal cord, or the motor 
 nuclei (facial, spinal accessory, and hypoglossal of Stilling in the medulla oblongata), in the muscles 
 connected with these parts. Rapid atrophy takes place in certain forms of spinal paralysis and in 
 acute bulbar paralysis (paralysis of the medulla oblongata), and in a chronic form in progressive 
 muscular atrophy and progressive bulbar paralysis. The muscles and their nerves become small 
 and soft. The muscles show many nuclei, the sarcous substance becomes fatty and ultimately dis- 
 appears. According to Charcot, these areas are at the same time the trophic centres for the nerves 
 proceeding from them as well as for the muscles belonging to them. According to Friedreich, the 
 primary lesion in progressive muscular atrophy is in the muscles, and is due to a primary interstitial 
 inflammation of the muscle, resulting in atrophy and degenerative changes, while the nerve centres 
 are affected secondarily, just as after amputation of a limb the corresponding part of the spinal cord 
 degenerates. 
 
 In pseudo-hypertrophic muscular atrophy the muscular fibres atrophy completely, with 
 copious development of fat and connective tissue between the fibres, without the nerves or spinal 
 cord undergoing degeneration. The muscular substance may also undergo amyloid or wax like 
 degeneration, whereby the amyloid substance infiltrates the tissue ({! 249, VI). Sometimes atrophic 
 muscles have a deep-brown color, due to a change of the haemoglobin of the muscle. When muscles 
 are much used, they hypertrophy, as the heart in certain cases of valvular lesion or obstruction 
 (J 49), the bladder and intestine. [In true hypertrophy there is an increased number or increase 
 in the size of its tissue elements, throughout the entire tissue or organ, without any deposit of a 
 foreign body. Perhaps, in hypertrophy of the bladder, the thickened muscular coat not only serves 
 to overcome resistance, but it offers greater resistance to bursting under the increased intra-vesical 
 pressure. Mere enlargement is not hypertrophy, for this may be brought about by foreign ele- 
 ments. In atrophy there is a diminution in size or bulk, even when the blood stream is kept up, 
 the decrease being due to pressure. An atrophied organ may be even enlarged, as seen in pseudo- 
 hypertrophic paralysis, where the muscles are larger, owing to the interstitial growth of fatty and 
 connective tissue, while the true muscular tissue is diminished and truly atrophied.] 
 
 308. STANDING.— The act of standing is accomplished by muscular action, 
 and is the vertical position of equilibrium of the body, in which a line drawn from 
 the centre of gravity of the body falls within the area of both feet placed upon v 
 the ground. In the military attitude the muscles act in two directions — (1) to 
 fix the jointed body, as it were, into one unbending column ; and (2) in case of 
 a variation of the equilibrium, to compensate, by muscular action, for the dis- 
 turbance of the equilibrium. 
 
 The following individual motor acts occur in standing : — 
 
 I. The fixation of the head upon the vertebral column. The occiput may be moved in various 
 directions upon the atlas, as in the acts of nodding. As the long arm of the lever lies in front of 
 the atlas, necessarily when the muscles of the back of the neck relax, as in sleep or death, the chin 
 falls upon the breast. The strong neck muscles, which pull from the vertebral column upon the 
 occiput, fix the head in a firm position on the vertebral column. The chief rotatory movement of 
 the head on a vertical axis occurs round the odontoid process of the axis. The articular surfaces on 
 the pedicles, aud part of the bodies of the 1st and 2d vertebrae, are convex toward each other in the 
 
540 SITTING. 
 
 middle, becoming somewhat lower in front and behind, so that the head is highest in the erect 
 posture. Hence, when the head is greatly rotated, compression of the medulla oblongata is pre- 
 vented (Henke). In standing, these muscles do not require to be fixed by muscular action, as no 
 rotation can take place when the neck muscles are at rest. 
 
 2. Fix Vertebral Column The vertebral column itself must be fixed, especially where it is 
 
 most mobile, i, c, in the cervical and lumbar regions. This is brought about by the strong muscles 
 situate in these regions, e. g., the cervical spinal muscles, Extensor dorsi communis and Quadralus 
 lumborum. 
 
 I Mobility of the Vertebrae. — The least movable vertebrae are the 3d to the 6th dorsal; the 
 I sacrum is quite immovable. For a certain length of the column, the mobility depends on (a) the 
 'number and height of the interarticular fibro-cartilages. They are most numerous in the neck, 
 thickest in the lumbar region, and relatively also in the lower cervical region. They permit move- 
 ment to take place in every direction. Collectively, the interarticular disks form one-fourth of the 
 height of the whole vertebral column. They are compressed somewhat by the pressure of the body ; 
 hence the body is longest in the morning and after lying in the horizontal position. The smaller 
 periphery of the bodies of the cervical vertebrae favors the mobility of these vertebrae compared with 
 the larger lower ones, (b) The position of the processes also influences greatly the mobility. The 
 strongly-depressed spines of the dorsal region hinder hyperextension. The articular processes on 
 the cervical vertebrae are so placed that their surfaces look obliquely from before and upward, back- 
 ward and downward ; this permits relatively free movement, rotation, lateral and nodding move- 
 ments. In the dorsal region the articular surfaces are directed vertically and directly to the front, 
 the lower directly backward ; in the lumbar region the position of the articular processes is almost 
 completely vertical and antero-posterior. In bending backward as far as possible, the most mobile 
 parts of the column are the lower cervical vertebrae, the I llh dorsal to the 2d lumbar and the lower 
 two lumbar vertebrae (£. H. Weber). 
 
 3. The centre of gravity of the head, trunk and arms, when fixed as above, lies in front of the 
 10th dorsal vertebra. It lies further forward, in a horizontal plane, passing through the xiphoid 
 process ( Weber}, the greater the distention of the abdomen by food, fat or pregnancy. A line 
 drawn vertically downward from the centre of gravity passes behind the line uniting both hip joints. 
 Hence, the trunk would fall backward on the hip joint, were it not prevented partly by ligaments 
 and partly by muscles. The former are represented by the ileo-femoral band and the anterior tense 
 layer of the fascia lata. As ligaments alone, however, never resist permanent traction, they are 
 aided, especially by the ileo-psoas muscle inserted into trie small trochanter, and in part, also, by the 
 rectus femoris. Lateral movement at the hip joint, whereby the one limb must be abducted and the 
 other adducted, is prevented especially by the large mass of the glutei. When the leg is extended, 
 the ileo-femoral ligament, aided by the fascia lata, prevents adduction. 
 
 4. The rigid part of the body, head and trunk, with the arms and the legs, whose centre of 
 gravity lies lower and only a little in front, so that the vertical line drawn downward intersects a 
 line connecting the posterior surfaces of the knee joints, must now be fixed at the knee joint. Falling 
 backward is prevented by a slight action of the quadriceps femoris, aided by the tension of the fascia 
 lata. Indirectly it is aided also by the ileo-femoral ligament. Lateral moven/ent of the knee is 
 prevented by the disposition of the strong lateral ligaments. Rotation cannot take place at the knee 
 joint in the extended position (g 305, I, 3). 
 
 5. A line drawn downward from the centre of gravity of the whole body, which lies in the pro- 
 monotory, falls slightly in front of a line between the two ankle joints. Hence, the body would 
 fo\\ forward on the latter joint. This is prevented especially by the muscles of the calf, aided by 
 the muscles of the deep layer of the leg (tibialis posticus, flexors of the toes, peroneus longus et 
 brevis). 
 
 Other Factors. — (a) As the long axis of the foot forms with the leg an angle of 50°, falling 
 forward can only occur after the feet are in a position more nearly parallel with their long axis, [b) 
 The form of the articular surfaces helps, as the anterior broad part of (he astragalus must be pressed 
 between the two malleoli. The latter mechanism cannot be of much importance. 
 
 6. The metatarsus and phalanges are united by tense ligaments to form the arch of the foot, 
 which touches the ground at three points— tuber calcanei (heel), the head of the first metatarsal 
 bone (ball of the great toe), and of the fifth toe. Between the latter two points the heads of the 
 metatarsal bones also form points of supports. The weight of the body is transmitted to the highest 
 part of the arch of the foot, the caput tali. The arching of the foot is fixed only by ligaments. The 
 toes play no part in standing, although, when moved by their muscles, they greatly aid the balancing 
 of the body. The maintenance of the erect attitude fatigues one more rapidly than walking. 
 
 309. SITTING. — Sitting is that position of equilibrium whereby the body is supported on the 
 tubera ischii, on which a too-and-fro movement may take place {H. v. Meyer). The head and 
 trunk together are made rigid to form an immovable column, as in standing. We may distinguish 
 — (1) the forward posture, in which the line of gravity passes in front of the tubera ischii; the 
 body being supported either against a fixed object, e. g., by means of the arm on a table, or against 
 the upper surface of the thigh. (2) The backward posture, in which the line of gravity falls 
 behind the tubera. A person is prevented from falling backward either by leaning on a support, or 
 
WALKING, RUNNING AND SPRINGING. 
 
 541 
 
 by the counter weight of the legs kept extended by muscular action, whereby the sacrum forms an 
 additional point of support, while the trunk is fixed on the thigh by the ileopsoas and rectus femoris, 
 the leg being kept extended by the extensor quadriceps. Usually the centre of gravity is so placed 
 that the heel also acts as a point of support. The latter sitting posture is, of course, not suited for 
 resting the muscles of the lower limbs. (3) When " sitting erect " the line of gravity falls 
 between the tubera themselves. The muscles of the legs are relaxed, the rigid trunk only requires 
 to be balanced by slight muscular action. Usually the balancing of the head is sufficient to main- 
 tain the equilibrium. 
 
 310. WALKING, RUNNING, AND SPRINGING.— By the term 
 walking is understood progression in a forward horizontal direction with the 
 least possible muscular exertion, due to the alternate activity of the two legs. 
 
 Methods. — The Brothers Weber were the first to analyze the various positions of the body in 
 walking, running, and springing, and they represented them in a continuous series, which represents 
 the successive phases of locomotion. These phases may be examined with the zoetrope (§ 398, 3). 
 Marey estimated the time relations of the individual acts, by transferring the movements by means 
 of his air tambours to a recording surface. Recently, by means of a revolving camera, he has suc- 
 ceeded in photographing, in instantaneous pictures (y^j second), the whole series of acts. Of 
 course this series, when placed in the zoetrope, represents the natural movements. Figs. 316, 317, 
 318 represent these acts. 
 
 In walking, the legs are active alternately; while one — the "supporting" or 
 "active" leg — carries the trunk, the other is "inactive" or "passive." Each 
 
 Phases of walking. The thick lines represent the active, the thin the passive leg ; h t the hip joint ; k, a, knee ; f,b, 
 ankle; c, d, heel; m, c, ball ol the tarso-metatarsal joints ; z,g; point of great toe. 
 
 leg is alternately in an active and a passive phase. Walking may be divided into 
 the following movements : — s - 
 
 I. Act (Fig. 315, 2). — The active leg is vertical, slightly flexed at the knee, and it alone supports' 
 the centre of gravity of the body. The passive leg is completely extended, and touches the ground 
 only with the tip of the great toe (z). This position of the leg corresponds to a right-angled tri- 
 angle, in which the active leg and the ground form two sides, while the passive leg is the hypo- 
 tenuse. 
 
 II. Act. — For the forward movement of the trunk, the active leg is inclined slightly from its 
 vertical position (cathetus) to an oblique and more forward (hypotenuse) position (3). In order 
 that the trunk may remain at the same height, it is necessary that the active leg be lengthened. This 
 is accomplished by completely extending the knee (3, 4, 5), as well as by lifting the heel from the 
 ground (4, 5), so that thefoot rests on the balls or the heads of the metatarsal bones, and lastly, by 
 elevating it on the point of the great toe (2, thin line). During the extension and forward move- 
 ment of the active leg, the tips of the toes of the passive leg have left the ground (3). It is slightly 
 flexed at the knee joint (owing to the shortening), it performs a " pendulum-like movement " (4,5), 
 whereby its foot is moved as far in front of the active leg as it was formerly behind it. The foot is 
 then placed flat upon the ground (1,2, thick lines) ; the centre of gravity is now transferred to this 
 active leg, which, at the same lime, is slightly flexed at the knee, and placed vertically. The first 
 act is then repeated. 
 
 Simultaneous Movements of the Trunk. — During walking the trunk performs certain char- 
 acteristic movements. ( 1 ) It leans every time toward the active leg, owing to the traction of the 
 
542 WALKING, RUNNING AND SPRINGING. 
 
 glutei and the tensor fasciae latse, so that the centre of gravity is moved, which, in short, heavy per- 
 sons with a broad pelvis, leads to their " waddling" gait. (2) The trunk, especially during rapid 
 walking, is inclined slightly forward to overcome the resistance of the air. (3) During the " pen- 
 dulum-like action," the trunk rotates slightly on the head of the active femor. This rotation is 
 compensated, especially in rapid walking, by the arm of the same side as the oscillating leg swinging 
 in the opposite direction, while that on the other side at the same time swings in the same direction 
 as the oscillating limb. 
 
 Modifying Conditions : 1. The Duration of the Step. — As the rapidity of the vibration of a 
 pendulum (leg) depends upon its length, it is evident that each individual, according to the length 
 of his legs, must have a certain natural rate of walking. The " duration of a step " depends also 
 upon the time during which both feet touch the ground simultaneously, which, of course, can be 
 altered voluntarily. When " walking rapidly " the time = O, i.e., at the same moment in which 
 the active leg reaches the ground, the passive leg is raised. 2. The Length of the Step. — Usually 
 about 6 to 7 decimetres [23 to 27 inches] ( Vierordt) must be greater, the more the length of the 
 hypotenuse of the passive leg exceeds the catherus of the active one. Hence, during a long step, 
 the active leg is greatly shortened (by flexion of the knee), so that the trunk is pulled downward. 
 Similarly, long legs can make longer steps. 
 
 According to Marey and others, the pendulum movement of the passive leg is not a true pen- 
 dulum movement, because its movement, owing to muscular action, is of more uniform rapidity. 
 During the pendulum movement of the whole limb, the leg vibrates by itself at the knee joint 
 [Lucie, H. Vierordt). 
 
 Fixation of the Femur. — According to Ed. and W. Weber, the head of the femur of the 
 
 Fig. 316. 
 
 4 5 6 12 J ' 
 I II III IV V VI 
 
 | m- m ■% m « 3 
 
 
 5 <=a -s SJ 
 
 ~9 "a •■a 
 
 4 5. 6 1 2. 3 
 
 i n in iv v vi 
 
 -^ *S a gs ea as ts* 
 
 ■ r ■< v - 
 
 
 pf 
 
 
 pi 
 
 
 I I I II 
 
 0.F.0 
 
 i 
 
 1.50 
 
 2 
 
 2.S0 3 MV*«. _J 
 
 Phases ot slow walking. Instantaneous photograph (Marey), only the side directed to the observer is shown. From 
 
 v?S"u-, ? os "^°T n S f the " gl ! t • ac .". vc leg: (''• a " the P hases of this le S are represented in six pictures (I to 
 VI) while after VI the vertical position is regained. The Arabic numerals indicate the simultaneous position 
 of the corresponding left leg ; thus i = I, == II, etc., so that during the position IV of the right leg, at the 
 same time the left leg has the position as i. ■ 
 
 passive leg is fixed in its socket chiefly by the atmospheric pressure, so that no muscular action is 
 _ necessary for carrying the whole limb. If all the muscles and the capsule be divided, the head of 
 the femur still remains in the cotyloid cavity. Rose refers this condition not to the action of the 
 atmospheric pressure, but to two adhesion surfaces united by means of synovia. The experiments of 
 Aeby show that not only the weight of the limb is supported by the atmospheric pressure, but 
 that the latter can support several times its weight. When traction is exerted on the limb, the 
 margins of the cotyloid ligament of the cotyloid cavity are applied like a valve tightly to the 
 margin of the cartilage of the head of the femur. According to the Brothers Weber, the leg falls 
 from its socket as soon as air is admitted by making a perforation into the articular cavity. 
 
 Work done during Walking.— Marey and:Demery estimate the amount done by a man 
 weighing 64 kilos. [10 stones], when walking slowly, as = 6 kilogrammetre s per second; rapid 
 running — 56 kilogrammetres. The work done is due to the raising of the entire body and 
 extremities, to the velocity communicated to the body, as well as to the maintenance of the centre 
 of gravity. 
 
 In springing or leaping the body is rapidly projected upward by the greatest possible and most 
 rapid contraction of the leg muscles, while at the same lime the centre of gravity is maintained by 
 other muscular acts (Fig. 318). 
 
 The pressure upon the sole of the foot in walking is distributed in the following manner : The 
 supporting leg always presses more strongly on the ground than the other ; the longer the step the 
 greater the pressure. The heel receives the maximum amount of pressure sooner than the point 
 of the foot \Carlet). 
 
WALKING, RUNNING AND SPRINGING. 
 
 543 
 
 Running is distinguished from rapid walking by the fact that, at a particular 
 moment, both legs do not touch the ground, so that the body is raised in the air. 
 The active leg, as it is forcibly extended from a flexed position, gives the body 
 the necessary impetus (Tig. 317). 
 
 Fig. 317. 
 
 eter. 
 
 Instantaneous photograph of a runner (Marey). Ten pictures per second. The abscissa indicates the length of the 
 
 step in metres. 
 
 Pathological. — Variations of the walking movements depend primarily upon diseases of bones, 
 ligaments, muscles, and tendons, and also upon affections of the motor nerves. The effect of sen- 
 sory nerves and the reflex mechanism of the spinal cord, and also of the" muscular sense on walk 
 ing, are stated in }g 355, 360, 430. 
 
 311. COMPARATIVE.— The absolute muscular force in animals is not, as a rule, much 
 
 Fig. 318. 
 
 High leap. Instantaneous photograph (Marey). The pictures partly overlap each other, as soon as the velocity of 
 the forward movement on the descent diminishes after springing. In the left-hand corner is the dial plnte, the 
 radius of which moved one division in fa second. The abscissa indicates the distance in metres. 
 
 different from man. The great motor power exerted by animals results from the thickness and 
 number of the muscles, as well as from the different arrangement of the levers and the action of 
 muscles on them. Insects particularly exert a large amount of force ; some insects can drag a body 
 sixty-seven times their own weight ; a horse scarcely its own weight. A man pressing upon a 
 dynamometer with one hand exerts pressure = 0.70 times his own weight, while a dog in lifting 
 
544 ACT OF SWIMMING. 
 
 its lower jaw exerts 8.3 times. A crab by closing its pincers 28.5 times. A mussel on closing its 
 shell 382 times its body weight (Plateau). 
 
 In mammals standing is much more easy, as they have four supporting surfaces. The spring- 
 ing animals have a sitting attitude, while the tail is often used as a support (kangaroo, squirrel). 
 In birds there is a mechanical arrangement by which, while perching, the tendons are flexed ; 
 hence, a bird while sleeping can still retain its hold (Cuvier). In the stork and crane, which stand 
 for a long time on one leg, this act is unaccompanied by muscular action, as the tibia is fixed by 
 means of a process which fits into a depression of the articular surface of the femur. 
 
 In walking we distinguish in mammals the step (le pas) — the four feet are generally moved in 
 four tempo, and usually diagonally, e.g., in the horse right fore, left hind; left fore, right hind. 
 [The camel is an exception — it moves the fore and hind limbs simultaneously on each side.] In 
 trotting this movement is accelerated ; the two limbs in a diagonal direction lift together, so that 
 only two hoof sounds are heard, while, at the same time, the body is raised more in the air. Dur- 
 ing the interval between two hoof beats the body is free in the air, all the limbs having left the 
 ground. Strictly speaking, the fore limb leaves the ground slightly sooner than the hind one. The 
 gallop. — When a (right) galloping horse moves in the air, the upper part of its body is fairly hori- 
 zontal ; when it touches the ground, the left hind foot is the first to touch the ground. Shortly 
 thereafter, the left fore leg and right hind foot touch the ground, while the right fore leg has not yet 
 reached the ground and is directed forward. The upper part of the body still retains its horizontal 
 direction. When, however, a few moments thereafter, the left hind leg again leaves the ground, it 
 is higher than the fore leg — simultaneously the right fore leg is thrown forward and lower, while the 
 right hind and left fore leg are stretched to the extreme. Immediately thereafter, these limbs leave 
 the ground, while the hind limb so far overtakes the fore limb that it comes to lie higher than the 
 latter. The body, therefore, is projected forward and downward umil the right fore limb, which 
 alone touches the ground, actively contracts and again raises the body from the ground. When 
 this happens, the horse again floats in the air, its body being directed horizontally. The long axis 
 of the horse's body in galloping is placed obliquely to the direction of the movement, and forming 
 a right angle. In forced galloping (la carriere), which is really a springing movement, the right 
 hind leg and left fore leg do not touch the ground at the same time, but the former does so sooner. 
 The amble is a modification of the step, which consists in this, that both feet on the same side 
 move at the same time or shortly after each other (camel, giraffe, elephant). Marey attached com- 
 pressible ampullae under the hoof of a horse, connecting them with registering apparatus, and thus 
 accurately registered the time relations of each act. Muybridge photographed the actions of a 
 horse and the different phases of the movement. 
 
 In snakes the rudder-like elevation and depression of the ribs causes the progression of the 
 body. 
 
 Swimming is an acquired art in man. The specific gravity of the body is slightly greater than 
 that of ordinary water, but slightly lighter than that of sea water. When lying quietly on the 
 back, so that only the mouth and nose are at last above the water, very slight movements of the 
 hands are necessary to keep a person from sinking. In this position, progression can be accom- 
 plished by extending and adducting the legs, while the movement is accelerated by rudder-like 
 movements of the arms. Swimming belly downward is more difficult, because the head, being 
 held above the water, makes the body specifically heavier. The forward movement and the act of 
 supporting the body in the water consist of three acts : First, horizontal, rudder-like movements of 
 the extended arms from before backward, until they reach the horizontal position (forward move- 
 ment) ; second, pressure of the arms downward, and subsequent adduction of the elbow joint to 
 the body (elevation of the body), together with retraction of the extended legs ; third, projection of 
 the arms, now brought together, and at the same time extension and adduction of the legs obliquely 
 backward and downward, thus causing elevation of the body as well as a forward movement. Too 
 rapid movements cause fatigue, while the respirations must be carefully regulated. Many land 
 mammals, whose body is specifically lighter than water, can swim, especially with the aid of their 
 hind limbs, while at the same time all the legs being directed downward, and being specifically the 
 heaviest part of the body, keep the trunk in the normal position. Fishes chiefly use their tail fin 
 as a motor organ, which is moved by powerful lateral muscles. When the tail is suddenly extended, 
 it presses upon the water and displaces it. Some fish, as the salmon, can lift their body out of the 
 water by a blow of their tail fin. The dorsal and anal fins enable the animal to preserve the erect 
 position. The pectoral and abdominal fins corresponding to the extremities execute slight move- 
 ments, especially upward and downward, which are greater during sleep. The swimming 
 bladder is the homologue of the lung, and is used for hydrostatic purposes in some fishes, and as 
 an auxiliary respiratory organ in others, e.g., the dipnoi ({! 140). It is absent or rudimentary in the 
 cyclostomata. In swimming birds, the body is specifically very much lighter than the water, 
 while their feathers are lubricated by the oily secretion of the coccygeal glands (g 291). Their 
 feet are usually webbed. 
 
 Flight. — Bats and their allies are the only flying mammals. The bones of the Upper limb and 
 phalanges are greatly elongated, and between these and the elongated hind limb (except the foot) 
 there is stretched a thin membrane. The membrane is moved by the powerful pectoral muscles. 
 The flying squirrel has only a duplicature of the skin stretched between the large bones of the ex- 
 
ARRANGEMENT OF THE LARYNX. 545 
 
 tremities, which serves as a parachute when the animals spring. In birds the body is specifically 
 very light ; numerous air sacs in the chest and belly communicate with the lungs, and with the 
 cavities of most of the bones (f! 140). The modified upper extremities are supported by the cora- 
 coid bone and the united clavicles or furculum, and are moved by the powerful pectoral muscles 
 attached to the keeled sternum. Marey, by means of his revolving photographic camera, has 
 analyzed all the phases of flight in a bird. 
 
 [Warner has studied the movements of the fingers, and correlated these movements with 
 changes in the nerve centres in certain diseased conditions, e.g., chorea. An India-rubber tube is 
 attached to each finger, and this " motor " part of the apparatus is connected with a Marey's tam- 
 bour. The several finger tubes are fixed to an arrangement not unlike a cricketer's glove, so that 
 voluntary or involuntary movements of the fingers can be registered and studied.] 
 
 312. VOICE AND SPEECH, PHYSICAL CONSIDERATIONS. 
 
 — The blast of expired air — and under certain circumstances the inspiratory 
 blast also — is employed to throw the tense vocal cords into a state of regular 
 vibration, whereby a sound is produced. The sound so produced is the human 
 voice. 
 
 The true vocal cords are really elastic membranous reeds. If a blast of air be forcibly driven 
 upward through the partially closed glottis, the vocal cords are pushed asunder, as the elastic tension 
 of the air overcomes the resistance of the cords. After the escape of air from below, the cords rapidly 
 return to their former position, and are again pushed asunder, and caused to vibrate. 
 
 1. Thus, when a membrane vibrates, the air must be alternately condensed and rarefied. The 
 condensation and rarefaction are the chief cause of the tone or note (as in the siren), not so much 
 the membranes themselves (». Helmholtz). 
 
 2. The "air tube" or porte vente, conducting the air to the membranes in man, is the lower 
 portion of the larynx, the trachea, and the whole bronchial system ; the bellows is represented by 
 the chest and lungs, which are forcibly diminished in size by the expiratory muscles. 
 
 3. The cavities which lie above the membranes constitute " resonators," and consist of the upper 
 part of the larynx, pharynx, and also of the cavities of the nose and mouth, arranged, as it were, in 
 two stories, the one over the other, which can be closed alternately. 
 
 The pitch of the tone produced by a membranous apparatus depends upon the following 
 factors : — 
 
 (a) On the length of the elastic membranes or plates. The pitch is inversely proportional to the 
 length of the elastic membrane, i. e., the shorter the membrane the higher the pitch, or the greater the 
 number of vibrations per second. Hence, the pitch of a child's vocal cords (shorter) is higher than 
 that of an adult. 
 
 (i) The pitch of the tone is directly proportional to the square root of the amount of the elas- 
 ticity of the elastic membrane. In membranous reeds, and also with silk, it is directly proportional 
 to the square root of the extending weight, which in the case of the larynx is the force of the mus- 
 cles rendering the cords tense. 
 
 (c) The tone of membranous reeds is not only strengthened by a more powerful blast, as the 
 amplitude of the vibrations is increased, but the pitch of the tone may also be raised at the same 
 time, because, owing to the great amplitude of the vibration, the mean tension of the elastic mem- 
 brane is increased. 
 
 (d) The supra-laryngeal cavities, which act as resonators, are inflated when the larynx is in 
 action, so that the tone produced by these cavities is added to and blended with the sound of the 
 elastic membranes, whereby certain partial tones of the latter are strengthened (j! 415). The char- 
 acteristic timbre of the voice largely depends upon the form of the resonators. 
 
 (e) When vocalizing, the strongest resonance takes place in the air tubes, as they contain com- 
 pressed air. It causes the vocal fremitus which is audible on placing the ear over the chest (§ 117, 
 6). 
 
 (/) Narrowing or dilating the glottis has no effect on the pitch of the tone, only with a wide 
 glottis much more air must be driven through it, which, of course, greatly increases the work of the 
 thorax. 
 
 313. ARRANGEMENT OF THE LARYNX.— I. The Cartilages 
 and Ligaments of the Larynx. — The fundamental part of the larynx consists 
 of the cricoid cartilage, whose small, narrow portion is directed forward and the 
 broad plate backward. The thyroid cartilage articulates by its inferior cornu 
 with the posterior lateral portion of the cricoid. This permits of the thyroid car- 
 tilage rotating upon a horizontal axis directed through both of the articular sur- 
 faces, so that the upper margin of the thyroid passes forward and downward, while 
 the joint is so constructed as to permit also of a slight upward, downward, for- 
 ward, and backward movement of the thyroid upon the cricoid cartilage. The 
 
 35 
 
546 
 
 STRUCTURE OF THE LARYNX AND VOCAL CORDS. 
 
 triangular arytenoid cartilages articulate at some distance from the middle line, 
 with oval, saddle-like, articular surfaces placed upon the upper margin of the plate 
 of the cricoid cartilage. The articular surfaces permit two kinds of movements on 
 the part of the arytenoid cartilages ; first, rotation on their base around their ver- 
 tical long axis, whereby either the anterior angle or processus vocalis, which is 
 directed forward, is rotated outward ; while the processus muscularis, which is 
 directed outward and projects over the margin of the cricoid cartilage, is rotated 
 backward and inward, or conversely. Further, the arytenoids may be slightly dis- 
 placed upon their bases either outward or inward. 
 
 The true vocal cords, or thyro-arytenoid ligaments, are in man about 15 
 millimetres, and in women 11 millimetres in length, and consist of numerous 
 
 Fig. 319. 
 
 Fig. 320. 
 
 Fig. 319. — Larynx from the front, with the ligaments and the insertions of the muscles. O. h., oshyoideum; C. tk. t 
 Cart, thyreoidea; Corp. trit., Corpus triticeum ; C c, Cart cricoidea ; C. r>., Cart, tracheales ; Ltg.thyr.- 
 hyoid. med., Ligamentum thyreo-hyoideum medium; Lig. tk.-h. lat., Ligam. thyreo-hyoideum laterale ; Lig. 
 eric. thyr. med. t Ligam. crico-thyreoideum medium; Lig. cric.-track., Ligam. crico-tracheale ; M. St.-k., 
 Muse, stemo-hyoideus ; M. th.-hyoid., Muse, thyreo-hyoideus ; M. si. -th., Muse, sterno-thyrebideus ; M. cr.- 
 ik., Muse, crico-thyreoideus. Fig. 320. — Larynx from behind after removal of the muscles. E., Epiglottis 
 cushion (W.) ; L. ar.-ep., Lig. ary-epiglotticum ; M. in , Membrana mucosa; C.W., Cart. Wrisbergii ; C. S., 
 Cart. Santorini ; C.aryt., Cart, arytsenoidea ; C. c. Cart, cricoidea; P. m., Processus muscularis of Cart, 
 arytaen. ; L. cr.~ar. t Ligam crico-arytsean. ; C. s., Comu superius; C.i. Cornu inferius Cart, thyreoidea; L. 
 ce.-cr. p. i. t Lig. kerato-cricoideum. post. inf. ; C. tr., Cart, tracheales; P. m. tr., Pars membranacea 
 tracheae. 
 
 elastic fibres. They arise close to each other from near the middle of the inner 
 angle of the thyroid cartilage, and are inserted each into the anterior angle or 
 processus vocalis of the arytenoid cartilages. The ventricles of Morgagni 
 permit free vibration of the true vocal cords, and separate them from the upper or 
 false cords, which consist of folds of mucous membrane. The false vocal cords 
 are not concerned in phon-ation, but the secretion of their numerous mucous glands 
 moistens the true vocal cords. 
 
 The obliquely directed under surface of the vocal cords causes the cords to come together very 
 easily when the glottis is narrow during respiration (e.g., in sobbing), while the closure may be 
 made more secure by respiration. The opposite is the condition of the false vocal cords, which, 
 
ACTION OF THE LARYNGEAL MUSCLES. 
 
 547 
 
 when they touch, are easily separated during inspiration ; while during expiration, owing to the 
 dilatation of the ventricles of Morgagni, they easily come together and close ( Wyllie, L. Brunton, 
 and Cash). 
 
 II. Action of the Laryngeal Muscles. — These muscles have a double 
 function : i. One connected with respiration, in as far as the glottis is widened 
 and narrowed alternately during respiration ; further, when the glottis is firmly- 
 closed by these muscles, the entrance of foreign substances into the larynx is 
 prevented. The glottis is closed immediately before the act of coughing (§ 120). 
 2. The laryngeal muscles give the vocal cords the proper tension and other 
 conditions for phonation. 
 
 1. The glottis is dilated by the action of the posterior crico-arytenoid 
 
 Fig. 321. 
 
 Fig. 322. 
 
 Cornu 
 
 Fig. 321. — Larynx from behind with its muscles. E. t Epiglottis, with the cushion (W.) ; C. W., Cart. Wrisbergii ; C. 
 S., Cart. Santorini ; C. c, Cart, cricoidea. Curnusup. — Cornu inf. Cart, thyreoideae ; M. ar. tr., Muse, arytae- 
 noideus transversus ; Mm. ar. obi., Musculi ary tsenoidei obliqui ; M. er.-aryt.post., Musculus crico-arytaenoi- 
 deus posticus ; Pars cart., Pars cartilaginea; Pars memb.. Pars membranacea tracheae. Fig. 322. — Nerves of 
 the larynx. O. k., Oshyoideum ; C. th., Cart, thyreoidea : C. c. Cart, cricoidea; Tr., Trachea ; M. th.-ar., 
 M. thyreo-arytaenoideus ; M. cr.-ar. J.,M. crico-arytaenoideus posticus ; M. cr.~ar. /., M. crico-arytaen. later, 
 alis; M.cr.-th., M. crico-thyreoideus ; N.lar.sup.v.,T$. laryngeus sup.; R. I., Ramus intemus ; R. E. , 
 Ramus ext. ; N. lar, rec. v., N. laryngeus recurrens ; R. I. N. L. R. t Ramus int. ; R. E. iV. L. R., Ramus 
 ext. nervi laryngei recurrentis vagi. 
 
 muscles. When they contract, they pull both processus musculares of the aryte- 
 noid cartilages backward, downward, and toward the middle line (Fig. 323), so 
 that the processus vocales (I, I) must go apart and upward (II, II). Thus, between 
 the vocal cords (glottis vocalis), as well as between the inner margins of the 
 arytenoid cartilages, a large triangular space is formed (glottis respiratoria), 
 and these spaces are so arranged that their bases come together, so that the aperture 
 between the cords and the arytenoid cartilages has a rhomboidal form. Fig. 323 
 shows the action of the muscles. The vocal cords, represented by lines converging 
 in front, arise from the anterior angle of the arytenoid cartilages (I, I). When 
 
548 
 
 ACTION OF THE LARYNGEAL MUSCLES. 
 
 these cartilages are rotated into the position (II, II), the cords take the position 
 indicated by the dotted lines. The widening of the respiratory portion of the 
 glottis between the arytenoid cartilages is also indicated in the diagram. 
 
 Pathological. — When these muscles are paralyzed, the widening of the glottis does not take 
 place, and there may be severe dyspnoea during inspiration, although the voice is unaffected (Riegel, 
 L. Weber). 
 
 2. The entrance to the glottis is constricted by the arytenoid muscle 
 
 (transverse), which extends transversely between both outer surfaces of the aryte- 
 noids along their whole length (Fig. 324). On the posterior surface of this muscle 
 is placed the cross bundles (Fig. 321) of the thyro-aryepiglotticus (or arytaenoidei 
 obliqui) ; they act like the foregoing. The action of these muscles is indicated 
 in Fig. 324; the arrows point to the line of traction. 
 
 Pathological. — Paralysis of this muscle enfeebles the voice and makes it hoarse, as much air 
 escapes between the arytenoid cartilages during phonation. 
 
 3. In order that the vocal cords be approximated to each other, which 
 
 Fig. 323. 
 
 Fig. 324. 
 
 Fig. 323. — Schematic horizontal section of the larynx. I, Position of the horizontally divided arytenoid cartilages 
 during respiration ; from their anterior processes run the converging vocal cords. The arrows show the line of 
 traction of the po sterior crico-arytenoid muscles ; II, II, the position of the arytenoid muscles as a result of this 
 action. Fig. 324. — Schematic horizontal section of the larynx, to illustrate the action of the arytenoid muscle. 
 I, I, position of the arytenoid cartilages during quiet respiration. The arrows indicate the direction of the con- 
 traction of the muscle ; II, II, the position of the arytenoid cartilages after the arytenoideus contracts. 
 
 occurs during phonation, the processus vocales of the arytenoid cartilages must 
 be closely apposed, whereby they must be rotated inward and downward. This 
 result is brought about by the processus musculares being moved in a forward and 
 upward direction by the thyro-arytenoid muscles. These muscles are applied 
 to, and, in fact, are imbedded in, the substance of the elastic vocal cords, and 
 their fibres reach to the external surface of the arytenoid cartilages. When 
 they contract, they rotate these cartilages, so that the processus vocales must 
 rotate inward. The glottis vocalis is thereby narrowed to a mere slit (Fig. 
 326), whilst the glottis respiratoria remains as a broad triangular opening. The 
 action of these muscles is indicated in Fig. 325. 
 
 The lateral crico-arytenoid muscle is inserted into the anterior margin of 
 the articular surface of the arytenoid cartilage; hence, it can only pull the car- 
 tilage forward ; but some have supposed it can also rotate the arytenoid cartilage 
 in a manner similar to the thyro-arytenoid (?), with this difference, that the pro- 
 cessus vocales do not come so close to each other. 
 
POSITION DURING PHONATION. 
 
 549 
 
 Scheme of the closure of the glottis by the ihyro-arytenoid 
 muscles. II, II, position of the arytenoid cartilages during 
 quiet respiration. The arrows indicate the direction of the 
 muscular traction. — I, I, position of the arytenoid carti- 
 lages after the muscles contract. 
 
 Pathological — Paralysis of both thyro- Fig. 325. 
 
 arytenoid muscles causes loss of voice. 
 
 4. The vocal cords are ren- 
 dered tense by their points of 
 attachment being removed from 
 each other by the action of muscles. 
 The chief agents in this action are 
 the crico-thyroid muscles, which 
 pull the thyroid cartilage forward 
 and downward. At the same time, 
 however, the posterior crico-aryte- 
 noids must pull the arytenoid carti- 
 lages slightly backward, and at the 
 same time keep them fixed. 
 
 The genio-hyoid and thyro-hyoid, when 
 they contract, pull the thyro : d upward and 
 forward toward the chin, and also tend to 
 increase the tension of the vocal cords (C 
 Mayer, Griitzner). 
 
 Pathological. — Paralysis of the crico- 
 thyroid causes the voice to become harsh 
 and deep, owing to the vocal cords not being sufficiently tense. 
 
 Position during Phonation. — The tension of the vocal cords brought about 
 in this way is not of itself sufficient for phonation. The triangular aperture of 
 the glottis respiratoria between the arytenoid cartilages, produced by the unaided 
 action of the internal thyro-arytenoid muscles (see 3) must be closed by the action 
 of the transverse and oblique arytenoid muscles. The vocal cords themselves 
 must have a concave margin, which is obtained through the action of the crico- 
 thyroids and posterior crico-arytenoids, so that the glottis vocalis presents the 
 appearance of a myrtle leaf (Henle), while the rima glottidis has the form of a 
 linear slit (Fig. 329). The contraction of the internal thyro-arytenoid converts 
 the concave margin of the vocal cords into a straight margin. This muscle adjusts 
 the delicate variations of tension of the vocal cords themselves, causing, more 
 especially, such variations as are necessary for the production of tones of slightly 
 different pitch. As these muscles come close to the margin of the cords, and are 
 securely woven, as it were, among the elastic fibres of which the cords consist, 
 they are specially adapted for the above-mentioned purpose. When the muscles 
 contract, they give the necessary resistance to the cords, thus favoring their vibra- 
 tion. As some of the muscular fibres end in the elastic fibres of the cords, these 
 fibres, when they contract, can render certain parts of the cords more tense than 
 others, and thus favor the modifications in the formation of the tones. The 
 coarser variations in the tension of the vocal cords are produced by the separa- 
 tion of the thyroid from the arytenoid cartilages, while the finer variations of 
 tension are produced by the thyro-arytenoid muscles. The value of the elastic 
 tissue of the cords does not depend so much upon its extensibility as upon its 
 property of shortening without forming -folds and creases. 
 
 Pathological. — In paralysis of these muscles, the voice can only be produced by forcible expira- 
 tion, as much air escapes through the glottis ; the tones are at the same time deep and impure. 
 Paralysis of the muscle of one side causes flapping of the vocal cord on that side (Gerhardt). 
 
 5. The relaxation of the vocal cords occurs spontaneously when the 
 stretching forces cease to act ; the elasticity of the displaced thyroid and arytenoid 
 cartilages comes into play, and restores them to their original position. The 
 vocal cords are also relaxed by the action of the thyro-arytenoid and lateral crico- 
 arytenoid muscles. 
 
 It is evident from the above statements that tension of the vocal cords and 
 
550 
 
 RELAXATION OF THE VOCAL CORDS. 
 
 narrowing of the glottis are necessary for phonation. The tension is pro- 
 duced by the crico-thyroids. and posterior crico-arytenoidsj the narrowing of the 
 glottis respiratoria by the arytenoids, transverse and oblique, the glottis vocalis 
 being narrowed by the thyro-arytenoids and (? lateral crico-arytenoids), the former 
 muscles causing the cords themselves to become tense. 
 
 Nerves (§ 352, 5). — The crico-thyroid is supplied by the superior laryngeal 
 branch of the vagus, which at the same time is the sensory nerve of the mucous 
 membrane of the larynx. All the other intrinsic muscles of the larynx are sup- 
 plied by the inferior laryngeal. 
 
 Fig. 326. 
 
 A vertical section through the head and neck, to the first dorsal vertebra, a, the position of the laryngoscope on 
 observing the posterior part of the glottis, arytenoid cartilages, the upper surface of the posterior wall of the 
 larynx: 6, its position on observing the anterior angle of the glottis. Large, a, and £, small laryngoscopic 
 mirrors. 
 
 The mucous membrane of the larynx is richly supplied with elastic fibres, and so is the sub- 
 mucosa. The sub-mucosa is more lax near the entrance to the glottis and in the ventricles of Mor- 
 gagni, which explains the enormous swelling that sometimes occurs in these parts in oedema 
 glottidis. A thin, clear limiting membrane lies under the epithelium. The epithelium is stratified, 
 cylindrical, and ciliated with intervening goblet cells. On the true vocal cords and the anterior 
 surface of the epiglottis, however, this is replaced by stratified squamous epithelium, which covers 
 the small papillae of the mucous membrane. Numerous branched mucous glands occur over the 
 cartilages of Wrisberg, the cushion of the epiglottis, and in the ventricles of Morgagni ; in other 
 situations, as on the posterior surface of the larynx, the glands are more scattered. The blood 
 vessels form a dense capillary plexus under the membrana propria of the mucous membrane ; 
 
THE LARYNGOSCOPE. 
 
 551 
 
 under this, however, there are other two strata of blood vessels. The lymphatics form a superficial 
 narrow mesh-work under the blood capillaries, with a deeper, coarser plexus. The medullated 
 nerves have ganglia in their branches, but their mode of termination is unknown. [W. Stirling 
 has described a rich sub-epithelial plexus of medullated nerve fibres on the anterior surface of the 
 epiglottis, while he finds that there are ganglionic cells in the course of the superior laryngeal 
 nerve.] 
 
 Cartilages. — The thyroid, cricoid, and nearly the whole of the arytenoid cartilages consist of 
 hyaline cartilage. The two former are prone to ossify. The apex and processus vocalis of the 
 arytenoid cartilages consist of yellow fibro cartilage, and so do all the other cartilages of the 
 larynx. 
 
 The larynx grows until about the sixth year, when it rests for a time, but it becomes again much 
 larger at puberty (<} 434). 
 
 314. LARYNGOSCOPY. — Historical.— After Bozzini (1807) gave the first impulse toward 
 the investigation of the internal cavities of the body, by illuminating them with the aid of mirrors, 
 Babington (1829) actually observed the glottis in this way. The famous singer Manuel Garcia 
 (1854) made investigations both on himself and other singers, regarding the movements of the vocal 
 cords, during respiration and phonation. The examination of the larynx by means of the laryngo- 
 scope was rendered practicable chiefly by Tiirck (1857) and Czermak, the latter observer being the 
 first to use the light of a lamp for the illumination of the larynx. Rhinoscopy was actually first 
 practised by Baumes (1838), but Czermak was the first person who investigated this subject system- 
 atically. 
 
 Fig 
 
 Method of examining the larynx. 
 
 The Laryngoscope consists of a small mirror fixed to a long handle, at an angle of 125 to 
 130 (Fig. 326, a, b). When the mouth is opened, and the tongue drawn forward, the mirror is in- 
 troduced, as is shown in Fig. 327. The position of the mirror must be varied, according to the 
 portion of the larynx we wish to examine ; in some cases, the soft palate has to be raised by the 
 back of the mirror, as in the position b. A picture of the part of the larynx examined is formed 
 in the small mirror, the rays of light passing in the direction indicated by the dotted lines from the 
 mirror ; they are reflected at the same angle through the mouth into the eye of the observer, who 
 must place himself in the direction of the reflected rays. 
 
 The illumination of the larynx is accomplished either by means of direct sunlight or by light 
 from an artificial source, e. g., an ordinary lamp, an oxyhydrogen lime light or the electric light. 
 The beam of light impinges upon a concave mirror of 15 to 20 centimetres focus, and 10 centi- 
 metres in width, and from its surface the concentrated beam of light is reflected through the mouth 
 of the patient, and directed upon the small mirror held in the back part of the throat. The beam 
 of light is reflected at the same angle toward the larynx by the small throat mirror, so that the 
 larynx is brightly illuminated. The observer has now to direct his eye in the same direction as the 
 illuminating rays, which can be accomplished by having a hole in the centre of the concave mirror 
 through which the observer looks. Practically, however, this is unnecessary ; all that is necessary 
 is to fix the concave mirror to the forehead by means of a broad elastic band, so that the observer, 
 by looking just under the margin of the concave mirror, can see the picture of the larynx in the 
 small throat mirror (Fig. 327). 
 
552 RHINOSCOPY. 
 
 In order to examine the larynx, place the patient immediately in front of you, and cause him to 
 open his mouth and protrude his tongue. A lamp is placed at the side of the head of the patient, 
 and light from this source is reflected from the concave mirror on the observer's forehead, and con- 
 centrated upon the laryngoscopic mirror introduced into the back part of the throat of the patient 
 (Fig. 327). 
 
 Oertel was able by means of a rapid intermittent illumination of the larynx through a stroboscopic 
 disk to study the movements of the vocal cords directly with the eye. Ssimanowsky put a pho- 
 tographic camera in the position of the eye, and photographed the movements of the vocal cords of 
 an artificial larynx.. [Brown and Behnke have photographed the human vocal cords.] 
 
 Laryngeal Electrodes. — V. Ziemssen showed that long, narrow electrodes can be introduced 
 into the larynx, so that the muscles can be stimulated and their actions studied ; while Rossbach 
 finds that the muscles and nerves of the interior of the larynx may be stimulated by stimulating 
 the skin, i.e., percutaneously. These methods are used both for physiological and therapeutical 
 purposes. 
 
 The Picture of the Larynx. — Fig. 328 shows the following structures: L., 
 the root of the tongue, with the ligamentum glosso-epiglotticum continued, from 
 its middle; on each side of the latter are V.V., the so-called vallecullm. The 
 epiglottis (£.) appears like an arched upper lip ; under it, during normal respira- 
 tion, the lancet-shaped glottis (i?.), and on each sideof it the true vocalcords (L. v.). 
 The length of the vocal cord in a child is 6 to 8 mm., in the female 10 to 15 mm. 
 
 when they are relaxed, and 15 to 20 mm. 
 when tense. In man, the length under the 
 same conditions is 15 to 20 mm. and 20 to 
 25 mm. The breadth varies from 2 to 5 mm. 
 On the external side of each vocal cord is 
 the entrance to the sinus of Morgagni {S.M.), 
 represented as a dark line. Further upward 
 and more external are (L.v.s.) the upper or 
 false vocal cords. [The upper or false vocal 
 tords are red, the lower or true, white.] On 
 each side of P. are (S.S.), the apices of the 
 cartilages of Santorini, placed upon the apices 
 of the arytenoid cartilages, while immediately 
 behind is the wall of the pharynx, P. In the 
 aryteno-epiglottidean fold are {W.W.) the 
 T V^e ! ^.^piJittis^K^afSu:' r.', cartilages of Wrisberg, while outside these are 
 glottis ; l.v. true vocal cords ,- s.m 'sinus the depressions (S.p.) constituting the Sinus 
 
 Morgagni; L.v.s., false vocal cords; P., • ■/■ 
 position of pharynx ; S., cartilage of San- pirijormes. 
 
 forces. w " ° f Wrisberg; s *- sinus piri - During normal respiration the glottis 
 
 (Fig. 329) has the form of a lancet-shaped 
 slit between the bright, yellowish- white vocal cords. If a deep inspiration be 
 taken, the glottis is considerably widened (Fig. 330), and if the mirror be favor- 
 ably adjusted we may see the rings of the trachea, and even the bifurcation of the 
 trachea (Fig. 330). 
 
 If a high note be uttered, the glottis is contracted to a very narrow slit (Fig. 
 33°)- 
 
 Rhinoscopy. — If a small mirror, fixed to a handle at an angle of ioo° to 110°, be introduced 
 into the pharynx, as shown in Fig. 331, and if the mirror be directed upward, certain structures are 
 with difficulty rendered visible (Fig. 332). In the middle is the septum narium [S,n.), and on 
 each side of it the long, oval, large posterior nares {Ch.), below this the soft palate {P.m.), with the 
 pendant uvula ((/.). In the posterior nares are the posterior extremities of the lower (C.i.), middle 
 (Cm.), and upper turbinated bones (C.s.). At the upper part, a portion of the roof of the pharynx 
 [O.R.) is seen, with the arched masses of adenoid tissue lying between the openings of the 
 Eustachian tubes (T.T.), and called by Luschka the pharyngeal tonsils. External to the opening 
 of the Eustachian tube is the tubular eminence (TV.), and outside this is the groove of Rosen- 
 miiller (j¥.). 
 
 Experiments on the Larynx.— Ferrein (jj 741), and, above all, Joh. Miillermade experiments 
 upon the excised larynx. A tracheal tube was tied into the excised human larynx, and air was 
 blown through it, the pressure being measured by means of a mercurial manometer, while various 
 
CONDITIONS AFFECTING THE LARYNGEAL SOUNDS. 
 
 553 
 
 arrangements were adopted for putting the vocal cords on the stretch and for opening or closing 
 the glottis. 
 
 315. CONDITIONS INFLUENCING THE LARYNGEAL 
 SOUNDS. — The pitch of the note emitted by the larynx depends upon : — 
 
 Fig. 329. 
 
 Fig. 330. 
 
 Position of the vocal cords on uttering a high note. 
 
 View of the rings and bifurcation of trachea. 
 
 i. The Tension of the Vocal Cords, i.e., upon the degree of contraction 
 of the crico-thyroid and posterior crico-arytenoid muscles, and also of the internal 
 thyro-arytenoids (§ 313, II, 4). 
 
 2. The Length of the Vocal Cord. — (_a) Children and females with short 
 
 Fig. 331. 
 
 Position of the laryngoscopic mirror in rhinoscopy. 
 
 Composite rhinoscopic view. S.n., Septum na- 
 rium ; C.i., Cm., C.s., lower, middle and 
 upper turbinated bones ; T., Eustachian tube ; 
 W. , tubular eminence; R. t groove of Rosen- 
 miiller; P.m., soft palate; O.R., roof of 
 pharynx; U., uvula. 
 
 vocal cords produce high notes, (b) If the arytenoid cartilages are pressed 
 together by the action of the arytenoid muscles (transverse and oblique), so that 
 the vocal cords alone can vibrate, while their intercartilaginous portions lying 
 between the processus vocales do not, the tone thereby produced is higher 
 
554 RANGE OF THE VOICE. 
 
 (Garcia). In the production of low notes, the vocal cords, as well as 
 margins of the arytenoid cartilages, vibrate. At the same time the space 
 above the entrance to the glottis is enlarged and the larynx becomes more 
 prominent. {/) Every individual has a certain medium pitch of his voice, 
 which corresponds to the smallest possible tension of the intrinsic muscles 
 of the larynx. 
 
 3. The Strength of the Blast. — That the strength of the blast from below 
 raises the pitch of the tones of the human larynx is shown by the fact that tones 
 of the highest pitch can only be uttered by powerful expiratory efforts. With 
 tones of medium pitch, the pressure of the air in the trachea is 160 mm., with 
 high pitch 200 mm., and with very high notes 945 mm., and in whispering 30 mm., 
 of water ( Cagniard-Latour, Griitzner). These results were obtained from a tra- 
 cheal fistula. 
 
 Accessory Phenomena. — The following as yet but partially explained phenomena are observed 
 in connection with the production of high notes : (a) As the pitch of the note rises, the larynx is 
 elevated, partly because the muscles raising it are active, partly because the increased intra-tracheal 
 pressure so lengthens the trachea that the larynx is thereby raised ; the uvula is raised more and 
 more (Zabus). (b) The upper vocal cords approximate to each other more and more, without, 
 however, coming into contact, or participating in the vibrations, (c) The epiglottis inclines more 
 and more backward over the glottis. 
 
 4. The falsetto voice with its soft timbre and the absence of resonance in 
 the air tubes (pectoral fremitus) is particularly interesting. Oertel observed 
 that during the falsetto voice the vocal cords vibrated so as to form nodes across 
 them, but sometimes there was only one node, so that the free margin of the cord 
 and the basal margin vibrated, being separated from each other by a nodal line 
 (parallel to the margins of the vocal cord). During a high falsetto note, there 
 may be three such nodal lines parallel to each other. The nodal lines are pro- 
 duced probably by a partial contraction of the fibres of the thyro-arytenoid muscle 
 (p. 548), while at the same time the vocal cords must be reduced to as thin plates 
 as possible by the action of the crico-thyroid, posterior arytenoid, thyro- and 
 genio-hyoid muscles (Oertei). The form of the glottis is elliptical, while with 
 the chest voice the vocal cords are limited by straight surfaces (Jelenffy, Oertel); 
 the air also passes more freely through the larynx. 
 
 Oertel also found that during the falsetto voice the epiglottis is erect. The apices of the aryte- 
 noid cartilages are slightly inclined backward, the whole larynx is larger from before backward, and 
 narrower from side to side, the aryepiglottidean folds are tense, with sharp margins, and the entrance 
 to the ventricles of Morgagni is narrowed. The vocal cords are narrower, the processus vocales 
 touch each other. The rotation of the arytenoid cartilages necessary for this is brought about by 
 the action of the crico-arytenoid alone, while the thyroarytenoid is to be regarded only as an acces- 
 sory aid. The pitch of the note is increased solely by increased tension of the vocal cords. In 
 addition, there are a number of transverse and longitudinal partial vibrations. During the chest 
 voice, a smaller part of the margin vibrates than in the falsetto voice, so that in the production of 
 the latter we are conscious of less muscular exertion in the larynx. The uvula is raised to the hori- 
 zontal position (Labus). 
 
 Production of Voice. — In order that voice be produced, the following con- 
 ditions are necessary : (1) The necessary amount of air is collected in the chest ; 
 (2) the larynx and its parts are fixed in the proper position; (3) air is then forced 
 by an expiratory effort either through the linear chink of the closed glottis, so 
 that the latter is forced open, or at first some air is allowed to pass through the 
 glottis without producing a sound, but as the blast of air is strengthened, the vocal 
 cords are thrown into vibration. 
 
 316. RANGE OF THE VOICE.— The range of the human voice for 
 chest notes is given in the following schema: — 
 

 SPEECH AND THE FORMATION OF VOWELS. 
 256 Soprano. 
 
 
 
 
 555 
 
 1024 
 
 
 
 171 
 
 | 
 
 Alto. 
 
 684 
 
 
 
 T 
 
 
 r 
 i 
 
 1 
 1 
 
 
 ■0- t- 
 
 EFGAH cdefgah 
 
 c'd' 
 
 e' f g' a' h' 
 
 ■"~ 
 
 u 
 
 , 
 
 
 ! 1 
 
 1 
 
 /L 
 
 1 
 
 m 
 
 
 
 
 fnY 
 
 I J 
 
 T i 
 
 
 
 v y 
 
 » 
 
 
 
 
 
 ■m- 
 
 
 
 
 3 //,j// e //f /' 
 
 g" 
 
 a"h/ 
 
 'c'" 
 
 80 
 
 
 
 Bass. 
 
 342 
 
 
 128 
 
 Tenor. 
 
 512 
 
 The accompanying figures indicate the number of vibrations per second in the corresponding tone. 
 It is evident from t' toy is common to all voices; nevertheless, they have a different timbre. The 
 lowest note or tone, which, however, is only occasionally sung by bass singers, is the contra-F, with 
 42 vibrations : the highest note of the soprano voice is &.'", with 1708 vibrations. 
 
 Timbre. — The voice of every individual has a peculiar quality, clang or timbre, 
 which depends upon the shape of all the cavities connected with the larynx. In 
 the production of nasal tones, the air in the nose is caused to vibrate strongly, so 
 that the entrance to the nares must necessarily be open. 
 
 317. SPEECH— THE VOWELS.— The motor processes connected with 
 the production of speech occur in the resonating cavities, the pharynx, 
 mouth and nose, and are directed toward the production of musical tones and 
 noises. 
 
 Whispering and Audible Speech. — When sounds or noises are produced 
 in the resonating chambers, the larynx being passive, the vox clandestina, or 
 whispering, is produced ; when the vocal cords, however, vibrate at the same 
 time, "audible speech" is produced. [Whispering, therefore, is speech 
 without voice.] Whispering may be fairly loud, but it requires great exertion, 
 i. e., a great expiratory blast, for its production ; hence it is very fatiguing. It 
 may be performed both with inspiration and expiration, while audible speech is 
 but temporary and indistinct if it is produced during inspiration. Whispering is 
 caused by the sound produced by the air passing through the moderately-contracted 
 rima glottidis, and passing over the obtuse margin of the cord. During the pro- 
 duction of audible sounds, however, the sharp margins of the vocal cords are 
 directed toward the air by the position of the processus vocales. jp 
 
 During speech, the soft palate is in action ; at each word it is raised, while, at the same time, 
 Passavant's transverse band is formed in the pharynx (j) 156). The soft palate is raised highest 
 when u and i are sounded, then with and e, and least with a. When sounding m and n it does 
 not move; it is high (like n) during the utterance of the explosives. With 1, s, and especially with 
 the gutteral r, it exhibits a trembling movement ( Gentzen, Falison). 
 
 Speech is composed of vowels and consonants. 
 
 A. Vowels (analysis and artificial formation, §415). — A. During whisper- 
 ing, a vowel is the musical tone produced, either during expiration or inspiration, 
 by the inflated characteristic form of the mouth {Danders), which not only has a 
 definite pitch, but also a particular and characteristic timbre. The characteristic 
 form of the mouth may be called " vowel cavity." 
 
 I. The pitch of the vowels may be estimated musically. It is remarkable that the fundamental 
 tone of the " vowel cavity " is nearly constant at different ages and in the sexes. The different 
 capacities of the mouth can be compensated by different sizes of the oral aperture. The pitch of 
 the vowel cavity may be estimated by placing a number of vibrating tuning forks of different pitch 
 in front of the mouth, and testing them until we find the one which corresponds with the funda- 
 mental tone of the vowel cavity. This is known by the fact that the tone of the tuning fork is 
 intensified by the resonance of the air in the mouth {v. Helmholtz), or the vibrations may be trans- 
 
556 
 
 THE FORMATION OF VOWELS. 
 
 ferred to a vibrating membrane and recorded on a smoked surface, as in the phonautograph of 
 Donders. 
 
 According to Konig, the fundamental tones of the vowel cavity are for 
 U = b, O = b', A= b", E = b"\ I = b"". 
 
 If the vowels be whispered in this series, we find at once that their pitch rises. 
 The fundamental tone in the production of a vowel may vary within certain 
 limits. This may be shown by giving the mouth the characteristic position and 
 then percussing the cheeks {Auerbach) • the sound emitted is that of the vowel, 
 whose pitch will vary according to the position of the mouth. 
 
 When sounding A, the mouth has the form of a funnel widening in front (Fig. 333, A). The 
 tongue lies in the floor of the mouth, and the lips are wide open. The soft palate is moderately 
 raised (Czermak). It is more elevated successively with O, E, U, I. The hyoid bone appears as if 
 at rest, but the larynx is slightly raised. It is higher than with U but lower than with I. 
 
 If we sound A to I, the larynx and the hyoid bone retain their relative position, but both are 
 raised. In passing from A to U, the larynx is depressed as far as possible. The hyoid bone passes 
 slightly forward (Briicke). When sounding A, the space between the larynx, posterior wall of the 
 pharynx, soft palate, and the root of the tongue, is only moderately wide ; it becomes wider with E, 
 and especially with I (Purkinje), but it is smallest with U. 
 
 When sounding U (Fig. 333), the form of the cavity of the mouth is like that of a capacious 
 
 Section of the parts concerned in phonation, Z, tongue : p, soft palate ; e, epiglottis ; g, glottis ; h, hyoid bone ; 
 thyroid, 2, 3, cricoid, 4, arytenoid cartilage. 
 
 flask with a short, narrow neck. The whole resonance apparatus is then longest. The lips are 
 protruded as far as posssible, are arranged in folds and closed, leaving only a small opening. The 
 larynx is depressed as far as possible, while the root of the tongue is approximated to the posterior 
 margin of the palating arch. 
 
 When sounding O, the mouth, as in U, is like a wide-bellied flask with a short neck, but the 
 latter is shorter and wider as the lips are nearer to the teeth. The larynx is slightly higher than 
 with U, while the resonance chambers also are shorter (Fig. 333). 
 
 When sounding I, the cavity of the mouth, at the posterior part, is in the form of a small-bellied 
 flask with a long, narrow neck, of which the belly has the fundamental tone, f, the neck that of 
 A"'. The resonating chambers are shortest, as the larynx is raised as much as possible, while the 
 mouth, owing to the retraction of the lips, is bounded in front by the teeth. The cavity between 
 the hard palate and the back of the tongue is exceedingly narrow, there being only >» median nar- 
 row slit. Hence, the air can only enter with a clear, piping noise, which sets even the vertex of 
 the skull in vibration, and when the ears are stopped the sounds seem very shrill. When the lar- 
 ynx is depressed and the lips protruded, as for sounding U, I cannot be sounded. 
 
 When sounding E, which stands next to I, the cavity has also the form of a flask with a small 
 belly (fundamental tone, f) and with a long, narrow neck (fundamental tone, b /// ) [v. Helmholtz). 
 The neck is wider, so that it does not give rising to a piping noise. The larynx is slightly lower 
 than for I, but not so high as for A. 
 
 Fundamentally there are only three primary vowels — I, A, U, the others and the so-called diph- 
 thongs standing between them [Briicke). 
 
CLASSIFICATION OF CONSONANTS. 557 
 
 Diphthongs occur when, during vocalization, we pass from the position of one 
 vowel into that of another. Distinct diphthongs are sounded only on passing 
 from one vowel with the mouth wide open to one with the mouth narrow ; dur- 
 ing the converse process the vowels appear to our ear to be separate (Briicke). 
 
 II. Timbre or Clang Tint. — Besides its pitch, every vowel has a special 
 timbre, quality, or clang tint. 
 
 The vocal timbre of U (whispering) has, in addition to its fundamental tone, b, a deep, piping 
 timbre. The timbre depends upon the number and pilch of the parliah or overtones of the vowel 
 sound (<S 415). 
 
 Nasal Timbre. — The timbre is modified in a special manner when the vowels are spoken with a 
 " nasal " twang, which is largely the case in the French language. The nasal timbre is produced 
 by the soft palate not cutting off the nasal cavity completely, which happens every time when a. pure 
 vowel is sounded, so that the air in the nasal cavity is thrown into sympathetic vibration. When a 
 vowel is spoken with a nasal timbre, air passes out of the nose and mouth simultaneously, while 
 with a pure vowel sound it passes out only through the mouth. 
 
 When sounding a pure vowel (non-nasal), the shutting off of the nasal cavity from the mouth is 
 so complete, that it requires an artificial pressure of 30 to 100 mm. of mercury to overcome it 
 {Hartmanri). 
 
 The vowels, a, a. (ae), 6 (ce), o, e, are used with a nasal timbre — a nasal i does not occur in any 
 language. Certainly it is very difficult to sound it thus, because, when sounding i, the mouth is so 
 narrow that, when the passage to the nose is open, the air passes almost completely through the lat- 
 ter, while the small amount passing through the mouth scarcely suffices to produce a sound. 
 
 In sounding vowels, we must observe if they are sounded through a previously closed glottis, as is 
 done in the German language in all words beginning with a vowel (spiritus lenis). The glottis, 
 however, may be previously opened with a preliminary breath, followed by the vowel sound ; we ob- 
 tain the aspirate vowel (spiritus asper of the Greeks). 
 
 B. If the vowels are sounded in an audible tone, /. e., along with the sound 
 from the larynx, the fundamental tone of the vocal cavity strengthens in a char- 
 acteristic manner the corresponding partial tones present in the laryngeal sound 
 {Wheatstone, v. Helmholtz). 
 
 318. CONSONANTS. — The consonants are noises which are produced at 
 certain parts of the resonance chambers. [As their name denotes, they can only 
 be sounded in conjunction with a vowel.] 
 
 Classification. — The most obvious classification is according to — (I.) Their acoustic properties, 
 so that they are divided into — ( I ) liquid consonants, i. e., such as are appreciable without a vowel 
 (m, n, 1, r, s) ; (2) mutes, including all the others, which cannot be distinctly heard without an 
 accompanying vowel. (II.) According to their mechanis?n of formation, as well as the type of the 
 organ of speech, by which they are produced. They are divided into — 
 
 1. Explosives — Their enunciation is accompanied by a kind of bursting open of an obstacle, or 
 an explosion, occasioned by the confined and compressed air which causes a stronger or weaker 
 noise ; or, conversely, the current of air is suddenly interrupted, while, at the same time, the nasal 
 cavities are cut off by the soft palate. 
 
 2. Aspirates, in which one part of the canal is constricted or stopped, so that the air rushes out 
 through the constriction, causing a faint whistling noise. (The nasal cavity is cut off.) In uttering 
 L, which is closely related to the aspirates, but differs from them in that the narrow passage for the 
 rush of air is not in the middle but at both sides of the middle of the closed part. (The nasal 
 cavity is shut off.) 
 
 3. Vibratives, which are produced by air being forced through a narrow portion of the canal, 
 so that the margins of the narrow tube are set in vibration. (The nasal cavity is shut off.) 
 
 4. Resonants (also called nasals or semi-vowels). The nasal cavity is completely free, while 
 the vocal canal is completely closed in the front part of the oral channel. According to the posi- 
 tion of the obstruction in the oral cavity, the air in a larger or smaller portion of the mouth is thrown 
 into sympathetic vibration. 
 
 We may also classify them according to the position in which they are produced 
 — the "articulation positions" of Briicke. These are : — 
 
 A. Between both lips ; B, between the tongue and the hard palate ; C, between 
 the tongue and the soft palate ; D, between the true vocal cords. 
 
 A. Consonants of the First Articulation Position. — I. Explosive Labials. — b, the voice is 
 sounded before the slight explosion occurs ; p, the voice is sounded after the much stronger explo- 
 sion has taken place (JCempelen). [The former is spoken of as " voiced " and the latter as 
 " breathed."] 
 
558 PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH. 
 
 2. Aspirate Labials. — f, between the upper incisor teeth and the lower lip (labiodental). It 
 is absent in all true Slavic words (Purkine) ; v, between both lips (labial) ; w is formed when the 
 mouth is in the position for f, but instead of merely forcing in the air, the voice is sounded at the 
 same time. Really there are two different w — one corresponding to the labial f, as in wiirde, and 
 the labiodental, e. g., quelle \Briicke). 
 
 3. Vibrative Labials. — The burring sound, emitted by grooms, but which is not used in civilized 
 language. 
 
 4. Resonant Labials. — m is formed essentially by sounding the voice whereby the air, in the 
 mouth and nose, is thrown into sympathetic vibration ["voiced"]. 
 
 B. Consonants of the Second Articulation Position. — I. The explosives, when enunciated 
 sharply and without the voice, are T hard (also dt and th) ; when they are feeble and produced 
 along with simultaneous laryngeal sounds (voice), we have D soft. 
 
 2. The aspirates embrace S, including s sharp, written s s or s z, which is produced without 
 any audible laryngeal vibration ; or soft, which requires the voice. Then, also, there are modifica- 
 tions according to the position where the noises are produced. The sharp aspirates include Sch, 
 and the hard English Th ; to the soft belong the French J soft, and the English Th soft. L, which 
 occurs in many modifications, belongs here, e. g., the L soft of the French. L may be sounded 
 soft with the voice, or sharp without it. 
 
 3. The vibratives, or R, which is generally voiced, but it can be formed without the larynx. 
 The resonants are N sounds, which also occurs in several modifications. 
 
 C. Consonants of the Third Articulation Position. — I. The explosives are the K sounds, which 
 are hard and breathed and not voiced ; G sounds, which are voiced. 
 
 2. The aspirates, when hard and breathed but not voiced, the Ch, and when sounded softly and 
 not voiced, J is formed. 
 
 3. The vibrative is the palatal R, which is produced by vibration of the uvula (Briicke). 
 
 4. The resonant is the palatal N. 
 
 D. Consonants of the Fourth Articulation Position. — I. An explosive sound does not occur 
 when the glottis is forced open, if a vowel is loudly sounded with the glottis previously closed. If 
 this occurs during whispering, a feeble, short noise, due to the sudden opening of the glottis, may be 
 heard. 
 
 2. The aspirates of the glottis are the H sounds, which are produced when the glottis is moder- 
 ately wide. 
 
 3. A glottis-vibrative occurs in the so-called laryngeal R of lower Saxon (Briicke). 
 
 4. A laryngeal resonant cannot exist. 
 
 The combination of different consonants is accomplished by the successive movements necessary 
 for each being rapidly executed. Compound consonants, however, or such as are formed when the 
 oral parts are adjusted simultaneously for two different consonants, so that a mixed sound is formed 
 from the two. Examples : Sch — tsch, tz, ts — Ps {([>) — Ks (Xg). 
 
 319. PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH.— Aphonia.— 
 
 Paralysis of the motor nerves (vagus) of the larynx by injury, or the pressure of tumors, causes 
 aphonia or loss of voice ( Galen). In aneurism of the aortic arch, the left recurrent nerve may 
 be paralyzed from pressure. The laryngeal nerves may be temporarily paralyzed by rheumatism, 
 over-exertion, and hysteria, or by serous effusions into the laryngeal muscles. If the tensors are 
 paralyzed, monotonia is the chief result ; the disturbances of respiration in paralysis of the larynx 
 are important. As long as the respiration is tranquil, there may be no disturbance, but as soon as 
 increased respiration occurs, great dyspncea sets in, owing to the inability of the glottis to dilate. 
 
 If only one vocal cord is paralyzed, the voice becomes impure and falsetto-like, while we may 
 feel from without that there is less vibration on the paralyzed side (Gerhardl). Sometimes the 
 vocal cords are only so far paralyzed that' they do not move during phonation, but do so during 
 forced respiration and during coughing (phonetic paralysis). 
 
 Diphthongia. — Incomplete unilateral paralysis of the recurrent nerve is sometimes followed by 
 a double tone, owing to the unequal tension of. the two vocal cords. According to Tiirck and 
 
 Schnitzler, however, the double tone occurs when the two 
 Fig. 334' vocal cords touch at some part of their course (e.g., from 
 
 the presence of a tumor, Fig. 334), so that the glottis is 
 divided into two unequal portions, each of which produces 
 its own sound. 
 
 Hoarseness is caused by mucus upon the vocal cords, by 
 roughness, swelling or looseness of the cords. If, while speak- 
 ing, the cords are approximated, and suddenly touch each 
 other, the " speech is broken," owing to the formation of nodal 
 points (g 352). Disease of the pharynx, nasopharyngeal 
 cavity, and uvula may produce a change in the voice reflexly. 
 Paralysis of the soft palate (as well as congenital per- 
 Tumors on the vocal cords causing Nation or cleft palate) causes a nasal timbre of all vowels; 
 double tone from the larynx. the former renders difficult the normal formation of consonants 
 
COMPARATIVE AND HISTORICAL. 559 
 
 of the third articulation position ; resonance is imperfect, while the explosives are weak, owing to 
 the escape of the air through the nose. 
 
 Paralysis of the tongue weakens I ; E and A (JE) are less easily pronounced, while the for- 
 mation of consonants of the second and third articulation position is affected. The term aph- 
 thongia is applied to a condition in which every attempt to speak is followed by spasmodic 
 movements of the tongue (Fleury). 
 
 In paralysis of the lips (facial nerve), and in hare-lip, regard must be had to the formation of 
 consonants of the first articulation position. When the nose is closed, the speech has a character- 
 istic sound. The normal formation of resonants is, of course, at an end. After excision of the 
 larynx, a metal reed enclosed in a tube, and acting like an artificial larynx, is introduced between 
 the trachea and the cavity of the mouth (Czerny). 
 
 Stammering is a disturbance of the formation of sounds. [Stammering is due to long-con- 
 tinued spasmodic contraction of the diaphragm, just as hiccough is (\ 120), and, therefore, it is 
 essentially a spasmodic inspiration. As speech depends upon the expiratory blast, the spasm pre- 
 vents expiration. It may be brought about by mental excitement or emotional conditions. Hence, 
 the treatment of stammering is to regulate the respirations. In stuttering, which is defective 
 speech due to inability to form the proper sounds, the breathing is normal.] 
 
 320. COMPARATIVE— HISTORICAL.— Speech may be classified with the " expres- 
 sion of the emotions " (Darwin). Psychical excitement causes in man characteristic movements, 
 in which certain groups of muscles are always concerned, e.g., laughing, weeping, the facial expres- 
 sion in anger, pain, shame, etc. These movements afford a means whereby one creature can com- 
 municate with another. Primarily in their origin, the movements of expression are reflex motor 
 phenomena ; when they are produced for purposes of explanation, they are voluntary imitations of 
 this reflex. Besides the emotional movements, impressions upon the sense organs produce char- 
 acteristic reflex movements, which may be used for purposes of expression (Geiger), e.g., stroking 
 or painful stimulation of the skin, movements after smelling pleasant or unpleasant or disagreeable 
 odors, the action of sound and light, and the perception of all kinds of objects. 
 
 The expression of the emotions occurs in its simplest form in what is known as expression by 
 means of signs or pantomime or mimicry. Another means is the imitation of sounds by the 
 organ of speech, constituting onamatopoesy, e.g., the hissing of a stream, the roll of thunder, the 
 tumult of a storm, whistling, etc. The expression of speech is, of course, dependent upon the 
 process of ideation and perception. 
 
 The occurrence of different sounds in different languages is very interesting. Some languages 
 (e.g., of the Hurons) have no labials ; in some South Sea Islands, no laryngeal sounds are spoken ; 
 / is absent in Sanskrit and Finnish ; the short e, 0, and the soft sibilants in Sanskrit; d, in Chinese 
 and Mexican, s, in many Polynesian languages ; r, in Chinese, etc. 
 
 Voice in Animals. — Animals, more especially the higher forms, can express their emotions by 
 facial and other gestures. The vocal organs of mammals are essentially the same as those of 
 man. Special resonance organs occur in the orang-outang, mandril, macacus and mycetes monkeys 
 in the form of large cheek pouches, which can be inflated with air, and open between the larynx 
 and the hyoid bone. 
 
 Birds have an upper (larynx) and a lower larynx (syrinx) the latter being placed at the bifur- 
 cation of the trachea, and is the true vocal organ. Two folds of mucous membrane (three in singing 
 birds) project into each bronchus, and are rendered tense by muscles, and are thus adapted to serve 
 for the production of voice. 
 
 Among reptiles the tortoises produce merely a sniffling sound, which in the Emys has a peculiar 
 piping character. The blind snakes are voiceless, the chameleon and the lizards have a very feeble 
 voice ; the cayman and crocodile emit a feeble roaring sound, which is lost in some adults owing 
 to changes in the larynx. The snakes have no special vocal organs, but by forcing out air from 
 their capacious lung they make a peculiar hissing sound, which in some species is loud. Among 
 amphibians the frog has a larynx provided with muscles. The sound emitted without any muscu- 
 lar action is a deep intermittent tone, while more forcible expiration, with contraction of the laryn- 
 geal constrictors, causes a clearer continuous sound. The male, in Rana esculenta, has at each side 
 of the angle of the mouth a sound bag, which can be inflated with air and acts as a resonance 
 chamber. The " croaking " of the male frog is quite characteristic. In Pipa, the larynx is pro- 
 vided with two cartilaginous rods, which are thrown into vibration by the blast of air, and act like 
 vibrating rods or the limbs of a tuning fork. Some fishes emit sounds, either by rubbing together 
 the upper and lower pharyngeal bones, or by the expulsion of air from the swimming bladder, 
 mouth or anus. 
 
 Some insects cause sounds partly by forcing the expired air through their stigmata provided with 
 muscular reeds, which are thus thrown into vibration (bees and many diptera). The wings, owing 
 to the rapid contraction of their muscles, may also cause sounds (flies, cockroach, bees). The 
 Sphinx atropos (death-heap moth) forces air from its sucking stomach. In others, sounds are pro- 
 duced by rubbing their legs on the wing cases (Acridium), or the wing cases on each other (Gryl- 
 lus, locust), or on the thorax (Cerambyx), on the leg (Geotrupes), on the abdomen or the margin of 
 the wing (Nekrophorus). In> Cicadaciae, membranes are pulled upon by muscles, and are thus 
 
560 HISTORICAL. 
 
 caused to vibrate. Friction sounds are produced between the cephalothorax and the abdomen in 
 some spiders (Theridium), and in some crabs (Palinurus). Some mollusca (Pecten) emit a sound 
 on separating their shells. 
 
 Historical. — The Hippocratic School was aware of the fact that division of the trachea abolished 
 the voice, and that the epiglottis prevented the entrance of food into the larynx. Aristotle made 
 numerous observations on the voice of animals. The true cause of the voice escaped him as well 
 as Galen. Galen observed complete loss of voice after double pneumothorax, after section of the 
 intercostal muscles or their nerves, as well as after destruction of part of the spinal cord, even 
 although the diaphragm still contracted. He gave the cartilages of the larynx the names that still 
 distinguish them ; he knew some of the laryngeal muscles, and asserted that voice was produced 
 only when the glottis was narrowed. He compared the larynx to a flute. The weakening of the 
 voice, in feeble conditions, especially after loss of blood, was known to the ancients. Dodart (1700) 
 was the first to explain voice as due to the vibration of the vocal cords by the air passing between 
 them. 
 
 The production of vocal sounds attracted much attention among the ancient Asiatics and Ara- 
 bians — less among the Greeks. Pietro Ponce (f 1584) was the first to advocate instruction in the 
 art of speaking in cases of dumbness. Bacon (1638) studied the shape of the mouth for the pro- 
 nunciation of the various sounds. Kratzenstein (1781) made an artificial apparatus for the pro- 
 duction of vowel sounds, by placing resonators of various forms over vibrating reeds. Von Kem- 
 pelen (176910 1791) constructed the first speaking machine. Rob. Willis (1828) found that an elastic 
 vibrating spring gives the vowels in the series — U, O, A, E, I — according to the depth or height 
 of its tone ; further, that by lengthening or shortening an artificial resonator on an artificial vocal 
 apparatus the vowels may be obtained in the same series. The newest and most important inves- 
 tigations on speech are by Wheatstone, v. Helmholtz, Donders, Briicke, etc., and are mentioned in 
 the context. Hensen succeeded in showing exactly the pitch of vocal tone, thus : The tone is sung 
 against a Konig's capsule with a gas flame. Opposite the flame is placed a tuning fork vibrating 
 horizontally, and in front of one of its limbs is a mirror, in which the image of the flame is reflected. 
 When the vocal tone is of the same number of vibrations as the tuning fork, the flame in the mirror 
 shows one elevation, if double, i. e., the octave, two, and with the double octave, four elevations. 
 
General Physiology of the 
 nerves and electro-physiology. 
 
 321. STRUCTURE OF THE NERVE ELEMENTS.— The ner- 
 vous elements present two distinct forms: — 
 
 1. Nerve f Non-medullated. 2. Nerve ( Various forms and 
 
 Fibres. ( Medullated. Cells. { functions. 
 
 An aggregation of nerve cells constitutes a nerve ganglion. The fibres rep- 
 resent a conducting apparatus, and serve to place the central nervous organs in 
 connection with peripheral end organs. The nerve cells, however, besides trans- 
 mitting impulses, act as physiological centres for automatic or reflex movements, 
 and also for the sensory, perceptive, trophic, and secretory functions. 
 
 I. Nerve Fibres occur in several forms : — 
 
 1. Primitive Fibrils. — The simplest form of nerve fibril, which is visible with a magnifying 
 power of 500 to 800 diameters linear, consists of primitive nerve fibrils. They are very delicate 
 fibres (Fig. 335, 1), often with small varicose swellings here and there in their course, which, 
 however, are due to changes post-mortem. They are stained of a brown or purplish color by the 
 gold chloride method, and they occur when a nerve fibre is near its termination, being formed by 
 the splitting up of the axis cylinder of the nerve fibre, e.g., in the terminations of the corneal 
 nerves, the optic nerve layer in the retina, the terminations of the olfactory fibres, and in a plexi- 
 form arrangement in non-striped muscle (p. 500). Similar fine fibrils occur in the gray matter of 
 the brain and spinal cord, and the finely-divided processes of nerve cells. 
 
 2. Naked or simple axial cylinders (Fig. 335, 2), which represent bundles of primitive fibrils 
 held together by a slightly granular cement, so that they exhibit very delicate longitudinal striation 
 with fine granules scattered in their course. The best example is the axial cylinder process of 
 nerve cells (Fig. 335, I, z). [The thickness of the axis cylinder depends upon the number of 
 fibrils entering into its composition.] 
 
 3. Axis cylinders surrounded with Schwann's sheath or Remak's fibres (3.8 to 6.8 ;j. 
 broad), the latter name being given to them from their discoverer (Fig. 335, 3). [These fibres are 
 also called pale or non-medullated, and from their abundance in the sympathetic nervous system, 
 sympathetic] They consist of a sheath, corresponding to Schwann's sheath [neurilemma, or 
 primitive sheath, which incloses an axial cylinder, while lying here and there under the sheath, and 
 between it and the axial cylinder, are nerve corpuscles. These fibres are always fibrillated longitudi- 
 nally]. The sheath is delicate, structureless, and elastic. Dilute acids clear up the fibres without 
 causing them to swell up, while gold chloride makes them brownish-red. They are widely distributed 
 in the sympathetic nerves [e.g., splenic] and in the branches of the olfactory nerves. All nerves 
 in the embryo, as well as the nerves of many invertebrata, are of this kind. £ According to Ran- 
 vier, these fibres do not possess a sheath, but the nuclei are merely applied to the surface, or slightly 
 embedded in the superficial parts of the fibre, so that they belong to the fibre itself. These fibres 
 also branch and form an anastomosing network (Fig. 336). This the medullated fibres never do. 
 These fibres, when acted on by silver nitrate, never show any crosses. The branched form occurs 
 in the ordinary nerves of distribution, and they are numerous in the vagus, but the olfactory nerves 
 have a distinct sheath which is nucleated.] 
 
 4. Axis cylinders, or nerve fibrils, covered only by a medullary sheath, or white substance 
 of Schwann, are met with in the white and gray matter of the central nervous system, in the optic 
 and auditory nerves. These medullated nerve fibres, without any neurilemma, often show after 
 death varicose swellings in their course [due to the accumulation of fluid between the medulla or 
 myelin and the axis cylinder]. Hence, they are. called varicose fibres. [The varicose appearance 
 is easily produced by squeezing a small piece of the white matter of the spinal cord between a slide 
 and a cover glass. Nitrate of silver does not reveal any crosses, and there are no nodes of Ranvier, 
 while osmic acid reveals no incisures. When acted upon by coagulating reagents, e.g., chromic 
 
 36 561 
 
562 
 
 STRUCTURE OF NERVE FIBRES. 
 
 acid, the medullary sheath appears laminated, so that on transverse section, when the axis Cylinder 
 is stained, it is surrounded by concentric circles (Fig. 337).] 
 
 5. Medullated Nerve Fibres, with Schwann's Sheath (Fig. 335, 5, 6). — These are the 
 most complex nerve fibres, and are 10 to 22.6 /* [rdtaiir t0 s^Vtf i ncn ] broad. They are most 
 numerous in, and, in fact, they make up the great mass of, the cerebrospinal nerves, although they 
 
 Fig. 335. 
 
 , Primitive fibrill* ; 2, axis cylinder; 3, Remak's fibres: 4, medullated varicose fibre : 5, 6, medullated fibre, with 
 Schwann's she »th ; c, neurilemma ; t, t, Ranvier's nodes ; b, white substance of Schwann ; d, cells of the endo- 
 neurium ; rt, axis cylinder ; x, myelin drops ; 7, transverse section of nerve fibres ; 8, nerve fibre acted on with 
 silver nitrate. I, multipolar nerve cell from the spinal cord ; z, axial cylinder process ; y, protoplasmic processes 
 — to the right of it a bipolar cell. II, peripheral ganglionic cell, with a connective-tissue capsule. Ill, ganglionic 
 cell with, o, a spiral, and, n, straight process ; «z, sheath. 
 
 are also present in the sympathetic nerves. [When examined in the fresh and living condition in 
 situ, they appear refractive and homogeneous (Ranvier, Stirling) ; but if acted upon by reagents, 
 they are not only refractive, but exhibit a double contour, the margins being dark and well defined.] 
 Each fibre consists of — [1. Schwann's sheath, neurilemma, or primitive sheath; 2. White substance of 
 Schwann, medullary sheath, or myelin; 3. Axis cylinder composed of fibrils; 4. Nerve corpuscles.] 
 
STRUCTURE OF NERVE FIBRES. 
 
 563 
 
 A. The axis cylinder, which occupies J to \ of the breadth of the fibre, is the essential part of the 
 nerve, and lies in the centre of the fibre (Fig. 335, 6, a) like the wick in the centre of a candle. Its usual 
 shape is cylindrical, but sometimes it is flattened or placed eccentrically [most probably due to the 
 hardening process employed]. It is composed of fibrils [united by cement; they become more 
 obvious near the terminations of the nerve, or after the action of reagents, which sometimes cause 
 the fibrils to appear beaded. It is quite transparent, and stains deeply with carmine or logwood], 
 while during life its consistence is semi-fluid. According to Kupffer, a fluid — nerve serum — lies 
 between the fibrils [while, according to other observers, the whole cylinder is enclosed in an elastic 
 sheath peculiar to itself and composed of neuro-keratin]. 
 
 Fig. 336. 
 
 Remak's fibre from vagus of 
 dog. b, fibrils : n, nucleus ; 
 /, protoplasm surrounding 
 it. 
 
 Fig. 337. 
 
 Fig. 339. 
 
 Transverse section of the nerve fibres 
 of the spinal cord, the axis cylinders 
 like dots surrounded by a clear 
 space (myelin). 
 
 Fig. 33S. 
 
 Intercostal nerve of a mouse (single 
 fasciculus of nerve fibres) stained 
 with silver nitrate. Endothelial 
 sheath stained, and some nodes of 
 Ranvier indicated by crosses. 
 
 Medullated nerve fibres blackened by 
 osmic acid. f t s, Ranvier's node ; 
 srh, Schwann's sheath. 
 
 Fromann's Lines.— Chloroform and collodion render it visible, while it is most easily isolated 
 as a solid rod, by the action of nitric acid with excess of potassium chlorate. When acted on by 
 silver nitrate, Fromann observed transverse markings on it, but their significance is unknown (Fig. 
 335,8). 
 
 B. White substance of Schwann, medullary sheath or myelin, surrounds the axis cylindfr, 
 like an insulating medium around an electric wire. In the perfectly fresh condition it is quite homo- 
 geneous, highly glistening, bright and refractive; its consistence is fluid, so that it oozes out of the 
 
564 STRUCTURE OF NERVE FIBRES. 
 
 cut ends of the fibres in spherical drops (Fig. 335, .r), [myelin drops, which are always marked 
 by concentric lines, are highly refractive, and best seen when afresh nerve is teased in salt solution.] 
 After death, or after the action of reagents, it shrinks slightly from the sheath, so that the fibres 
 have a double contour, while the substance itself breaks up into smaller or larger droplets, due not 
 to coagulation (Pertii), but, according to Toldt, to a process like emulsification, the drops pressing 
 against each other. Thus the fibre it broken up into masses, so that it has a characteristic appear- 
 ance (Fig. 335, 6). It contains a large amount of cerebrin, which swells up to form myelin-like 
 forms in warm water. It also contains fatty matter, so that these fibres are blackened by osmic 
 acid [while boiling ether extracts cholesterin from them]. Chloroform, ether, and berizin, by dissolv- 
 ing the fatty and some other constituents of the fibres, make them very transparent. [Some ob- 
 servers describe a fluid lying between the medulla and the axis cylinder. ] 
 
 C. The Sheath of Schwann, or the neurilemma, lies immediately outside of and invests the 
 white sheath (Fig. 335, 6, c), and is a delicate, structureless membrane, comparable to the sarco- 
 lemma of a muscular fibre. 
 
 D. Nerve Corpuscles. — At fairly wide intervals under the neurilemma, and lying in depressions 
 between it and the medullary sheath, are the nucleated nerve corpuscles, which are readily stained 
 by pigments. [They may be compared to the muscle corpuscles, the nuclei being surrounded by a 
 small amount of protoplasm which sometimes contains pigment. They are not so numerous as in 
 muscle.] 
 
 [Adamkiewicz describes nerve corpuscles, or " demilunes " under the neurilemma, quite dis- 
 tinct from the ordinary nerve corpuscles. They are stained yellow by safranin, while the ordinary 
 nerve corpuscles are stained by methylanilin]. 
 
 Ranvier's Nodes or Constrictions. — The neurilemma forms in broad fibres at longer and in 
 narrower ones at shorter intervals, the nodes or constrictions of Ranvier (Fig. 335, 6, t, t; Fig. 338, 
 f, s). They are constrictions which occur at regular intervals along a nerve fibre ; at them the white 
 substance of Schwann is interrupted, so that the sheath of Schwann lies upon the axis cylinder [or 
 its elastic sheath] at the nodes. The part of the nerve lying between any two nodes [is called an 
 interannular or internodal segment"], and each such segment contains one or more nuclei, so that 
 some observers look upon the whole segment as equivalent to one cell. 
 
 The function of the Nodes seems to be to permit the diffusion of plasma through the outer 
 sheath into the axis cylinder, while the decomposition products are similarly given off. [A coloring 
 matter like picrocarmine diffuses into the fibre only at the nodes, and stains the axis cylinder red, 
 although it does not diffuse through the white substance of Schwann.] 
 
 [Incisures (of Schmidt and Lantermannl. — Each interannular segment in a stretched nerve shows 
 a number of oblique lines running across the white substance, which are called incisures. They 
 indicate that the segment is built up of a series of conical sections, each of which is bevelled at its 
 ends, and the bevels are arranged in an imbricate manner, the one over the other (Fig. 338), while 
 the slight interval between them appears as an incisure. Each such section of the white matter is 
 called a cylinder cone {Kuhnt).\ 
 
 Neuro-Keratin Sheath. — According to Ewald and Kuhne, the axis cylinder, as well as the 
 white substance of Schwann, is covered with an excessively delicate sheath, consisting of neuro- 
 keratin, and the two sheaths are connected by numerous transverse and oblique fibrils, which per- 
 meate the white substance. [The myelin seems to lie in the interstices of this mesh-work.] 
 
 [Rod-like Structures in Myelin. — If a nerve be hardened in ammonium chromate (ox picric 
 acid), M'Carthy has shown that the myelin exhibits rod-like structures, radiating from the axis cyl- 
 inder outward, and which are stained with logwood and carmine. The rods are probably not dis- 
 tinct from each other, but are, perhaps, part of the neuro-keratin network already described.] 
 
 [Action of Nitrate of Silver. — When a small nerve, e.g., the intercostal nerve of a mouse, is 
 acted on by silver nitrate, it is seen to be covered by an endothelial sheath composed of flattened 
 endothelial cells (Fig. 339"), while the nerve fibres themselves exhibit crosses along their course. 
 These crosses are due to the penetration of the silver solution at the nodes, where it stains the cement 
 substance and also part of the axis cylinder, so that the latter sometimes exhibits transverse mark- 
 ings called Fromann's lines (Fig. 335, 8).] 
 
 [New Methods. — Much progress has recently been made in tracing the course of medullated 
 nerve fibres by the action of new staining reagents ; thus, acid fuchsin stains the myelin deeply, leav- 
 ing the other parts unstained, at least it can be so manipulated as to yield this result. Weigert finds 
 that the myelin is also stained by logwood after a tissue has been hardened in cupric sulphate (or 
 acetate) and a chromium salt. By these methods medullated fibres have been traced where their 
 existence was previously not surmised.] 
 
 In the spinal nerves those fibres are thickest which have the longest course before they reach 
 their end organ {Schmalbe), while those ganglion cells are largest which send out the longest nerve 
 fibres (Pierret). [Gaskell finds that the longest nerves are not, necessarily, the thickest, for the 
 visceral nerves in the vagus are small nerves, and yet run a very long course.] 
 
 Division of Nerves. — Nerve fibres run in the nerve trunks without dividing; but when they 
 approach their termination they often divide dichotomously [at a node], giving rise to two similar 
 fibres, but there may be several branches at a node (Fig. 341, /). 
 
STRUCTURE OF THE NERVE SHEATHS. 
 
 565 
 
 [The divisions are numerous in motor nerves to striped muscles.] In the electrical nerves of the 
 malapterurus and gymnotus, there is a great accumulation of Schwann's sheaths round a nerve, so 
 that a nerve fibre is as thick as a sewing needle. Such a fibre, when it divides, breaks up into a 
 bundle of smaller fibres. 
 
 Nerve Sheaths. — [An anatomical nerve trunk consists of bundles of nerve fibres. The bundles 
 are held together by a common connective-tissue sheath (Fig. 340, ep), the epineurium [Axel Key 
 and Retzius), which contains the larger blood vessels, lymphatics, and sometimes fat and plasma 
 cells ] Each bundle is surrounded with its own sheath or perineurium (pe) [which consists of 
 lamellated connective tissue disposed circularly, and between the lamellae are lymph spaces lined 
 by flattened endothelial plates]. These lymph spaces may be injected from and communicate with 
 the lymphatics. 
 
 [The nerve fibres within any bundle are held together by delicate connective tissue, which pene- 
 trates between the adjoining fibres, constituting the endoneurium (ed). It consists of delicate 
 fibres with branched connective-tissue corpuscles (Fig. 335, 6, d), and in it lie the capillaries, which 
 are not very numerous, and are arranged to form elongated open meshes.] 
 
 [Henle's Sheath. — When a nerve is traced to its distribution, it branches and becomes smaller, 
 until it may consist only of a few bundles or even a single bundle of nerve fibres. As the bundle 
 branches, it has to give off part of its lamellated sheath or perineurium to each branch, so that, as 
 we pass to the periphery, the smaller bundles are surrounded by few lamellae. In a bundle con- 
 
 Fig. 340. 
 
 Transverse section ot a nerve (median), ep, epineurium ; pe, perineurium ; ed, endoneurium. 
 
 taining only a few fibres, this sheath may be much reduced, or consist only of thin, flattened connective- 
 tissue corpuscles with a few fibres. A sheath surrounding a few nerve fibres is called Henle's Sheath 
 {Ranvier).~\ 
 
 [Nervi Nervorum. — Marshall and v. Horsley have shown that the nerve sheaths are provided 
 with special nerve fibres, in virtue of which they are endowed with sensibility.] 
 
 Development. — At first nerve fibres consist only of fibrils, which become covered with connective 
 substance, and ultimately the white substance of Schwann is developed in some of them. The 
 growth in length of the fibres takes place by elongation of the individual " interannular " segments, 
 and also by the new formation of these ( Vignal). 
 
 II. Ganglionic or Nerve Cells. — 1. Multipolar nerve cells (Fig. 335, I) occur partly as 
 large cells (100 p, and are, therefore, visible to the unaided eye). In the anterior horn of the 
 spinal cord, and in a different form in the cerebellum, and partly in a smaller form (20 to 10 /*) in 
 the posterior horns of the spinal cord, many parts of the cerebrum and cerebellum, and in the 
 retina. They may be spherical, ovoid, pyramidal [cerebrum], pear- or flask-shaped [cerebellum], 
 and are provided with numerous branched processes which give the cells a characteristic appear- 
 ance. They are devoid of a cell envelope, are of soft consistence, and exhibit a fibrillated structure, 
 which may extend even into the processes. Fine granules lie scattered throughout the cell sub- 
 stance between the fibrils. Not unfrequently yellow or brown granules of pigment are also found, 
 either collected at certain parts in the cell or scattered throughout it. The relatively large 
 
566 
 
 CHEMISTRY OF THE NERVOUS SUBSTANCE. 
 
 Fig. 341. nucleus consists of a clear envelope enclosing a resistant substance. 
 
 !^_^ It does not appear to have a membrane in youth (Schwalbe). Within 
 
 SjsissSv the nucleus lies the nucleolus, which in the recent condition is angu- 
 
 >f§|pfs|j^. lar, provided with processes tmd capable of motion, but after death 
 
 fPllslfjlilfev > s highly refractive and spherical. One of the processes is always 
 
 unbranched, constituting the axial cylinder process (I, s), which 
 remains unbranched; but it soon becomes covered with the white 
 substance of Schwann and the other sheaths of a medullated nerve, 
 so that it becomes the axial cylinder of a nerve fibre. [Thus a nerve 
 fibre is merely an excessively long, unbranched process of a nerve 
 cell pushed outward toward the periphery.] It is not definitely ascer- 
 tained that the cerebral cells have such processes. All the other 
 processes divide very frequently until they form a branched, root-like, 
 complex arrangement of the finest primitive fibrils. These are called 
 protoplasmic processes (l,y). By means of these processes ad- 
 joining cells are brought into communication with each other, so that 
 impulses can be conducted from one cell to another. Further, many 
 of these fibrils approximate to each other and join together to form 
 axis cylinders of other nerve fibres. 
 
 2. Bipolar cells are best developed in fishes, e. g., in the spinal 
 ganglia of the skate, and in the Gasserian ganglion of the pike. 
 They appear to be nucleated, fusiform enlargements of the axis 
 cylinder (Fig. 335, on the right of I). The white substance often 
 stops short on each side of the enlargement, but sometimes the white 
 substance and the sheath of Schwann pass over the enlargement. 
 
 3. Nerve cells with connective-tissue capsules occur in the 
 peripheral ganglia of man (Fig. 335, II), e. g., in the spinal gan- 
 glia. The soft body of the cell, which is provided with several 
 processes,, is covered by a thick, tough capsule composed of sev- 
 eral layers of connective-tissue corpuscles ; .while the inner surface 
 of the composite capsule is lined by a layer of delicate endothelial 
 cells (Fig. 341). The body of the cells in the spinal ganglia is 
 traversed by a network of fine fibrils {Hemming). The capsule is 
 continuous with the sheath of the nerve fibre. 
 
 Rawitz and G. Retzius find that the cells of the spinal ganglia are 
 unipolar, the outgoing fibre taking a half-turn within the capsule' 
 before it leaves the cell (Fig. 341). Retzius [and Ranyier] observed 
 the process to divide like a T. Perhaps this division corresponds to 
 the two processes of a bipolar cell. The jugular ganglion and plexus 
 gangliiformis vagi in man contain only unipolar cells, so that, in this re- 
 spect, they may be comp"ared to spinal ganglia. The same is the case in 
 the Gasseriari ganglion ; while the ciliary, sphenopalatine, otic and sub- 
 maxillary ganglia structurally resemble the ganglja of the sympathetic. 
 4. Ganglionic cells with spiral 'fibres {Beale, J. Arnold) occur chiefly in the abdominal 
 sympathetic of the frog. The body of the cell is usually pyriform in shape, and from it proceeds 
 a straight unbranched process (Fig. 335, III, n), which ultimately becomes the axis cylinder of a 
 nerve. A spiral fibre springs from the cell (? a. network); emerges from it, and curves in a spiral 
 direction round the former (0). The whole cell is surrounded by a nucleated capsule (m). We 
 know nothing of the significance of the different fibres. 
 
 Cell from the Gasserian ganglion. 
 n, nuclei of the sheath ; t, 
 fibre dividing at a node ot 
 Ranvier. 
 
 322. CHEMISTRY OF THE NERVOUS SUBSTANCE.-^Me- 
 chanical Properties of Nerves. — i. Proteids. — Albumin occurs chiefly in 
 the axis- cylinder and in the substance of the ganglionic cells. . Some of this pro- 
 teid substance presents characters not unlike those of myosin (§ 293). Dilute 
 solution of common salt extracts a proteid from nervous matter, which is precipi- 
 tated by the addition of much water and also by a concentrated solution o( 
 common salt {Petrowsky). Potash albumin and a globulin- like substance are also 
 present. . Albuminoids.— -Nuclein occurs especially in the gray matter (§ 250, 
 2); while neuro-keratin, a body containing much sulphur and closely related to 
 keratin, occurs in the corneous sheath of nerve fibres (p. 564). If gray nervous 
 matter be subjected to artificial digestion with trypsin, both of these substances 
 remain undigested (Kuhne and Ewald). Pure neuro-keratin is obtained by treat- 
 ing the residue with- caustic potash. The sheath of Schwann does not yield 
 gelatin, but a substance closely related to elastin (§ 250, 6), from which it differs,- 
 
REACTION AND CHEMICAL COMPOSITION OF NERVES. 
 
 567 
 
 however, in being more soluble in alkalies. The connective tissue of nerves 
 yields gelatin. 
 
 2. Fats and other allied substances soluble in ether, more especially in the white 
 matter : (a) Cerebrin, free from phosphorus (§ 250, 3). 
 
 It is a white powder composed of spherical granules soluble in hot alcohol and ether, but 
 insoluble in cold water. It is decomposed at 8o° C, and its solutions are neutral. When boiled 
 for a long time with acids it splits up into a left rotatory body like sugar, and another unknown pro- 
 duct. Preparation. — Rub up the brain into a thin fluid with baryta water. Extract the separated 
 coagulum with boiling alcohol. The extract is frequently treated with cold ether to remove the 
 cholesterin ( IV. Miiller). Parkus separated from cerebrin its homologue, homocerebrin, which is 
 slightly more soluble in alcohol, and the clyster-like body, encephalin, which is soluble in hot 
 water. 
 
 (b) ^Lecithin (§ 251) and its decomposition products — glycero-phosphoric acid 
 and oleo-phosphoric acid. 
 
 Neurin (or Cholin = C 6 H 15 N0 2 ) is a strongly alkaline, colorless fluid, forming crystalline 
 salts with acids. It is soluble in water and alcohol, and has been formed synthetically from glycol 
 and trimethylamin. Lecithin is a salt of the base neurin. 
 
 (c) Protagon, which contains N and P, is similar to cerebrin, and is, accord- 
 ing to its discoverer (Liebreich), the chief constituent of the brain. 
 
 According to Hoppe-Seyler [and Diaconow], it is a mixture of lecithin and cerebrin. [The 
 
 investigations of Gamgee and Blankenhorn have shown, however, that protagon is a definite 
 
 chemical body. They find that, instead of being unstable, it is a very stable body.] It is a gluco- 
 
 . side, and crystalline, and can be extracted from the brain by warm alcohol, and when boiled with 
 
 baryta yields the decomposition products of lecithin. 
 
 3. The following substances are extracted by water : Xanthin and hypoxanthin (Sckerer) kreatin 
 (Lerch), inosit (IV. Miiller), ordinary lactic acid (Gscheidlen), and volatile fatty acids; leucin (in 
 disease), urea (in ura;mia). All these substances are for the most part products of the regressive 
 metabolism of the tissues. 
 
 Reaction. — Nervous substance, when passive, is neutral or feebly alkaline in 
 reaction, while active (? and dead) it is acid (Funke). The gray matter of the 
 brain, when quite fresh, is alkaline (Liebreich'), but death rapidly causes it to 
 become acid (Gscheidlen). 
 
 The reaction of nerve fibres varies during life. After introducing methyl-blue into the body of 
 
 a living animal, Ehrlich found that the axis cylinder became blue, i.e.; in those nerves which have 
 
 an alkaline reaction (cortex cerebri, cardiac, sensory, motor (non- striped), gustatory and o lfactor y 
 
 fibres), while the termination of motor (voluntary) n erves re mai n uncolored. The latter he regards 
 
 . as acid. ■• 
 
 The nerves after death have a more solid consistence, so that in all probability 
 some coagulation or change, comparable to the stiffening of muscle (j$ 295), 
 occurs in them after death, while at the same time a free acid is liberated. If a 
 fresh brain be rapidly " broiled " at ioo° C, it, like a muscle similarly treated, 
 remains alkaline (§ 295.) 
 
 Chemical Composition.. 
 
 Gray Matter. 
 
 White Matter. 
 
 The solids consist of — 
 Albumins and glutin . , 
 
 81.6 per cent. 
 18.4 " 
 
 554 " 
 17.2 " 
 
 18.7 •' 
 0.5 " 
 6.7 
 
 1.5 " 
 
 68.4 per cent. 
 
 31.6 " 
 
 24.7 " 
 
 99 " 
 .52.1 " 
 
 9-5 " . . 
 3-3 " 
 0.5 " 
 
 Cholesterin and fats 
 
 Cerebrin 
 
 Substances insoluble in ether 
 
 Salts . . 
 
 1000 
 
 100.0 
 
568 MECHANICAL STIMULI. 
 
 In ioo parts of Ash, Breed found potash 32, soda n, magnesia 2, lime 0.7, NaCl 5, iron phos- 
 phate 1.2, fixed phosphoric acid 39, sulphuric acid 0.1, silicic acid 0.4. 
 
 [Ptomaines (p. 275) are obtained from putrefied brain. They have an effect on the motor nerves 
 like curara, but in a much less degree, while the phenomena last for a much shorter time {Guareschi 
 and Mosso)."] 
 
 Mechanical Properties. — One of the most remarkable mechanical proper- 
 ties of nerve fibres is the absence of elastic tension according to the varying posi- 
 tions of the body. Divided nerves do not retract ; such nerves exhibit delicate, 
 microscopic, transverse folds (Fontana's transverse markings) [like watered silk]. 
 
 The cohesion of a nerve is very considerable. When a limb is forcibly torn 
 from the body, as sometimes happens from its becoming entangled in machinery, 
 the nerve not unfrequently remains unsevered, while the other soft parts are rup- 
 tured. [Tillaux found that a weight of no to 120 lbs. was required to rupture 
 the sciatic nerve at the popliteal space, while to break the median or ulnar nerve 
 of a fresh body, a force equal to 40 to 50 lbs. was required. The toughness and 
 elasticity of nerves are often well shown in cases of injury or gun-shot wounds. 
 The median or ulnar nerve will gain 15 to 20 centimetres (6 to 8 inches) before 
 breaking. Weir Mitchell has shown that a healthy nerve will bear a very con- 
 siderable amount of pressure and handling, and, in fact, the method of nerve 
 stretching depends upon this property of a nerve trunk.] 
 
 323. METABOLISM OF NERVES.— Influence of Blood Supply. 
 
 — We know very little regarding the metabolic processes that occur in nerve tissue. 
 Some extractives are obtained from nerve tissue, and they may, perhaps, be re- 
 garded as decomposition products (p. 567). It has not been proved satisfactorily 
 that during the activity of nerves there is an exchange of O and C0 2 . That there 
 is an exchange of materials within the nerves is proved by the fact that after com- 
 pression of the blood vessels of the nerves, the excitability of the nerves 
 falls, and is restored again when the circulation is re-established. Compression of 
 the abdominal aorta causes paralysis and numbness of the lower half of the body, 
 while occlusion of the cerebral vessels causes almost instantaneously cessation of 
 the cerebral functions. The metabolism of the central nervous organs is much 
 more active than that of the nerves themselves. [If the abdominal aorta of a 
 rabbit be compressed for a few minutes the hind limbs are quickly paralyzed, the 
 animal crawls forward on its fore legs, drawing the hind limbs in an extended 
 position after it.] The ganglia form much lymph. 
 
 324. EXCITABILITY OF THE NERVES— STIMULI.— Nerves 
 
 possess the property of being thrown into a state of excitement by stimuli, and 
 are, therefore, said to be excitable or irritable. The stimuli may be applied to, 
 and may act upon, any part of the nerve. [The following are the various kinds 
 of stimuli, i. e., modes of motion, which act upon nerves] : — 
 
 1. Mechanical stimuli act upon nerves when they are applied with sufficient 
 rapidity to produce a change in the form of the nerve particles, e. g. , a blow, 
 pressure, pinching, tension, puncture, section. In the case of sensory nerves, 
 when they are stimulated, pain is produced, as is felt when a limb "sleeps," or 
 when pressure is exerted upon the ulnar nerve at the bend of the elbow. When a 
 motor nerve is stimulated, motion results in the muscle attached to the nerve. If 
 the continuity of the nerve fibres be destroyed, or, what is the same thing, if the 
 continuity of the axial cylinder be interrupted by the mechanical stimulus, the 
 conduction of the impulse across the injured part is interrupted. If the molecular 
 arrangements of the nerves be permanently deranged, e. g., by a violent shock, 
 the excitability of the nerves may be thereby extinguished. 
 
 A slight blow applied to the radial nerve in the fore arm, or to the axillary nerves in the supra- 
 clavicular groove, is followed by a contraction of the muscles supplied by these nerves. Under 
 pathological conditions the excitability of a nerve for mechanical stimuli may be increased enor- 
 mously. 
 
THERMAL AND CHEMICAL STIMULI. 569 
 
 Tigerstedt ascertained that the minimal mechanical stimulus is represented by 900 milligram- 
 millimetres, and the maximum by 7000 to 8000. Strong stimuli cause fatigue, but the fatigue does 
 not extend beyond the part stimulated. A nerve when stimulated mechanically does not become 
 acid. Slight pressure without tension increases the excitability, which diminishes after a short time. 
 The mechanical work produced by an excited muscle in consequence of a stimulus was 100 times 
 greater than the mechanical energy of the mechanical nerve stimulus. 
 
 Continued pressure upon a mixed nerve paralyzes the motor sooner than 
 the sensory fibres. If the stimulus be applied very gradually, the nerve may be 
 rendered inexcitable without manifesting any signs of its being stimulated (Fon- 
 tana, 1758). Paralysis, due to continuous pressure gradually applied, may occur 
 in the region supplied by the brachial nerves ; the left recurrent laryngeal nerve 
 also may be similarly paralyzed from the pressure of an aneurism of the arch of 
 the aorta. 
 
 By increasing the pressure on a nerve by using a gradually increasing weight, there is at first an 
 increase and then a decrease of the excitability. Pressure on » mixed nerve abolishes reflex con- 
 duction sooner than motor conduction {Kronecker and Zederbaum). 
 
 Nerve stretching is one of the methods that has recently been employed for therapeutical pur- 
 poses. If a nerve be exposed and stretched, or if a certain tension be exerted upon it, this acts as 
 a stimulus. Slight extension increases the reflex excitability {Schleich), while violent extension pro- 
 duces a temporary diminution or abolition of the excitability ( Valentin): The centripetal fibres 
 (sensory) of the sciatic nerve are sooner paralyzed thereby than the centrifugal motor {Conrad). 
 During the process of extension mechanical changes are produced, either in the nerve itself or in 
 its end organs, causing an alteration of the excitability', but it may also affect the central organs. 
 The paralysis which sometimes occurs after forcible stretching usually rapidly disappears. There- 
 fore, when a nerve is in an excessively excitable condition, or when this is due to an inflammatory 
 fixation or constriction of the nerve at some part of its course, then nerve stretching may be useful, 
 partly by diminishing the excitability, partly by breaking up the inflammatory adhesions. In cases 
 where stimulation of an afferent nerve gives rise to epileptic or tetanic spasms, nerve stretching may 
 be useful by diminishing the excitability at the periphery, in addition to the other effects already 
 described. It has also been employed in some spinal affections, which may not as yet have resulted 
 in marked degenerative changes. 
 
 Tetanomotor. — For physical purposes, a nerve may be stimulated mechanically by means of 
 Heidenhain's tetanomotor, which is simply an ivory hammer attached to the prolonged spring of 
 a Neef 's hammer of an induction machine. The rapid vibration of the hammer communicates a 
 series of mechanical shocks to the nerve upon which it is caused to beat. Rhythmic extension of 
 a nerve causes contractions and even tetanus. 
 
 2. Thermal Stimuli. — If a frog's nerve be heated to 45° C, its excitability 
 is first increased and then diminished. The higher the temperature, the greater 
 is the excitability, and the shorter its duration (Afanasieff'). If a nerve be heated 
 to 50° C. for a short time, its excitability and conductivity are abolished. The 
 frog's nerve alone regains its excitability on being cooled {Pickford, J. Rosenthal). 
 If the temperature be raised to 65 C, the excitability is abolished without the 
 occurrence of a contraction, while its medulla is broken up {Eckhard). Sudden 
 cooling of a nerve to 5 C. acts as a stimulus, causing contraction in a muscle, 
 while sudden heating to 40 to 45° C. produces the same result. If the temper- 
 ature be increased still more, instead of a single contraction a tetanic condition 
 is produced. All such rapid variations of temperature quickly exhaust the nerve 
 and kill it. If a nerve be frozen gradually, it retains its excitability on being 
 thawed. The excitability lasts long in a cooled nerve ; in fact, it is increased in 
 a motor nerve, but the contractions are not so high and more extended, while the 
 conduction in the nerve takes place more slowly. Among mammalian nerves, the 
 afferent and vaso-dilator nerves at 45° to 50 C. exhibit the results of stimulation, 
 while the others only show a change in their excitability. When cooled to + 5° 
 C, the excitability of all the fibres is diminished (Griitzner). 
 
 3. Chemical Stimuli excite nerves when they act so as to change their con- 
 stitution with,a certain rapidity (p. 509). Most chemical stimuli act by first in- 
 creasing the nervous excitability, and then diminishing or paralyzing it. Chem- 
 ical stimuli, as a rule, have less effect upon sensory than upon motor fibres (Eck- 
 hard, Setschenow). According to Griitzner, the inactivity of chemical stimuli, 
 
570 PHYSIOLOGICAL AND ELECTRICAL STIMULI. 
 
 so often observed when they are applied to sensory nerves, depends in great part 
 upon the non-simultaneous stimulation of all the nerve fibres. Among chemical 
 stimuli are — (a) rapid abstraction of water by dry air, blotting paper, exposure 
 in a chamber containing sulphuric acid, or by the action of solutions which ab- 
 sorb fluids, e.g., concentrated solutions of neutral alkaline salts (NaCl. excites 
 only motor fibres in mammals — Griitzner), sugar, urea, concentrated glycerin (and 
 ? some metallic salts). The subsequent addition of water may abolish the contrac- 
 tions, while the nerye may still remain excitable. The abstraction of water first 
 increases and afterward diminishes the excitability. The imbibition of water 
 diminishes the excitability, (b) Free alkalies, mideral acids (not phosphoric), 
 many organic acids (acetic, oxalic, tartaric, lactic), and most salts of the heavy 
 metals. While the acids act as stimuli, only when they are somewhat concen- 
 trated, the caustic alkalies act in solutions of 0.8 to 0.1 per cent. (Kuhne). 
 Neutral potash salts in a concentrated form rapidly kill a nerve, but they do not ex- 
 cite it nearly so strongly as the soda compounds. Dilute solutions of the neutral 
 potash salts first increase and afterward diminish it (JRanke). (/) Various sub- 
 stances, e.g., dilute alcohol, ether, chloroform, bile, bile salts, and sugar. These 
 substances usually excite contractions, and afterward rapidly kill the nerve. Am- 
 monia (Eckhard), lime water (Kuhne), some metallic salts, carbon bisulphide 
 and ethereal oils kill the nerve without exciting it — at least without producing 
 any contraction in a frog's nerve-muscle preparation. Carbolic acid does the 
 same, although when applied directly to the spinal cord it produces spasms. 
 These substances excite the muscles when they are directly applied to them. 
 Tannic acid does not act as a stimulus either to nerve or muscle. As a general 
 rule, the stimulating solutions must be more concentrated when applied to a nerve 
 than to a muscle, in order that a contraction may be produced. 
 
 [Methods. — If a nerve-muscle preparation of a frog's limb be made, and a straw flag (p. 508) 
 attached to the toes while the femur is fixed in a clamp, and its nerve be then dipped in a saturated 
 solution of common salt, the toes soon begin to twitch, and by and by the whole limb becomes 
 tetanic, and thus keeps the straw flag extended. The effect of fluid on a muscle or nerve is easily 
 tested by fixing the muscle in a clamp, while a drop of the fluid is placed on a greased surface, 
 which gives it a convex form [Kiihne). The end of the muscle or nerve is then brought into con- 
 tact with the cupola of the drop.] 
 
 4. The Physiological or normal stimulus excites the nerves in the normal 
 intact body. Its nature is entirely unknown. The " nerve motion " thereby set 
 up travels either in a " centrifugal " or outgoing direction from the central 
 nervous system, giving rise to motion, inhibition of motion, or secretion ; or in 
 a " centripetal" or ingoing direction from the specific end organs of the nerves 
 of the special senses or the sensory nerves. In the latter case the impulse reaches 
 the central organs, where it may excite sensation or perception, or it may be 
 transferred to the motor areas and be conducted in a centrifugal direction, con- 
 stituting a "reflex " stimulation (§ 360). A single physiological nerve impulse 
 travels more slowly than that excited by the momentary application of an induc- 
 tion shock {Loven, v. Kries). It is not a uniform process, excited by varying 
 intensity and greater or less frequency of stimulation, but it is essentially a pro- 
 cess varying considerably in duration, and it may even last as long as yi second 
 (v. Kries). 
 
 5. Electrical Stimuli. — The electrical current acts most powerfully upon the 
 nerves at the moment when it is applied, and at the moment when it ceases 
 (§ 336) ; i n a similar way, any increase or decrease in the strength of a constant 
 current acts as a stimulus. If an electrical current be applied to a nerve, and its 
 strength be very gradually increased or diminished, then the visible signs of 
 stimulation of the nerve are very slight. As a general rule, the . stimulation is 
 more energetic the more rapid the variations of the strength of the current applied 
 to the nerve, i. e., the more suddenly the intensity of the stimulating current is 
 increased or diminished {Du Bois-Reymond). 
 
EFFECT OF CONSTANT CURRENT. 571 
 
 An electrical current must have a certain strength (liminal intensity) before it is 
 effective. By uniformly increasing the strength of the current, the size of the 
 contraction increases rapidly at first, then more slowly (Tigerstedl and Willhard). 
 
 An electrical current, in order to stimulate a nerve, must act at least during 
 0.0015 second {Fick, 1863, Konig) ; even with currents of slightly longer dura- 
 tion, the opening shock may have no effect. If the duration of the closing shock 
 of a constant current be so arranged that it is just too short to be active, then it 
 merely requires to last 1.3 to 2 times longer to produce the most complete effect 
 (GtUnhageri). 
 
 The electrical current is most active when it flows in the long axis of the nerve ; 
 it is inactive when applied vertically to the axis of the nerve {Galvani,/. Albrecht, 
 A. Meyer). Similarly, muscles are incomparably less excited by transverse than 
 by longitudinal currents {Giuffre). 
 
 The greater the length of nerve traversed by the current, the less the stimulus 
 that is required {Ffaff, Marcuse, Tschirjew). 
 
 Constant Current. — If the constant current be used as a nervous stimulus, 
 the stimulating effect on the sensory nerves is most marked at the moment of 
 closing and opening [or breaking] the current ; during the time the current passes 
 only slight excitement is perceived, but even under these circumstances very strong 
 currents may cause very considerable, and even unbearable, sensations. If a con- 
 stant current be applied to a motor nerve, the greatest effect is produced when 
 the current is closed [closing contraction] and when it is opened [opening 
 contraction]. But while the current is passing, the stimulation does not cease 
 completely ( Wundt) ; for, with a certain strength of stimulus, the muscle remains 
 in a state of tetanus Cgalvanotonus or " closing tetanus") (Pfluger). For 
 the same effect on muscles, see p. 518. With strong currents, this tetanus does 
 not appear, chiefly because the current diminishes the excitability of the nerves, 
 and thus develops resistance, which prevents the stimulus from reaching the 
 muscle. According to Hermann, a descending current applied to the nerve, 
 at a distance from the muscles, causes this tetanus more readily, while an 
 ascending current causes it more readily when the current is closed near the 
 muscle. The constant current is said by Griitzner to have no effect on vaso- 
 motor and secretory fibres. 
 
 Over-maximal Contraction. — By gradually increasing the strength of the electrical stimulus 
 applied to a motor nerve, Fick observed that the muscular contractions (height of the lift) at first 
 increased proportionally to the increase of the stimulus, until a maximal contraction was obtained. 
 If the strength of the stimulus be increased still further, another increase of the contraction above 
 the first-reached maximum is obtained. This is called an " over-maximal contraction." Occasion- 
 ally between the first maximum and the second there is a diminution, or, indeed, absence of or 
 gap in the contractions (Fick). The cause of this lies in the positive pole, which, with a certain 
 strength of current, is sufficient to prevent the further transmission of the excitement (\ 335). On 
 continuing to increase the induction current, ultimately a stage is reached where the stimulation at 
 the negative pole again becomes stronger than the inhibition at the positive, and this overcomes the 
 latter. The contractions before the gap are caused by the occurrence of the induction current 
 (their latent period is short) ; the contractions (long latent period, like that after all opening shocks 
 — Waller, p. 518) after the gap are caused by the disappearance of the induction current, i. c, by 
 polarization ; this is added to the stimulation proceeding from the negative pole, which, after the 
 gap, overcomes the inhibition at the positive pole, and excites the over- maximal contractions ( Tiger- 
 stedt and Willhard). 
 
 Tetanus. — If single shocks of short duration be rapidly applied after each other 
 to a nerve, tetanus in the corresponding muscle is produced (§ 298, III). 
 
 A motor nerve has a greater specific excitability for electrical stimuli than the 
 muscle substance. This is proved by the fact that a feebler stimulus suffices to 
 excite a muscle when applied to the nerve than when it is applied to the muscle 
 directly, as occurs when the terminations of the motor nerves are paralyzed by 
 curara {Rosenthal). 
 
 Soltmann found that the excitability of the motor nerves of new-born ani- 
 
572 DIMINUTION OF THE EXCITABILITY. 
 
 mals for electrical stimuli is less than in adults. The excitability increases until 
 the 5th to 10th month. 
 
 Unequal Excitability. — Under certain circumstances, the nearer the part of 
 the motor nerve stimulated lies to the central nervous system, the greater is the 
 effect produced (contraction) ; [or, what is the same thing, the further the point 
 of a nerve which is stimulated is from the muscle, the stimulus being the same, 
 the greater is the contraction]. According to Fleischl, all parts of the nerve are 
 equally excitable for chemical stimuli. Further, it is said that the higher-placed 
 parts of a nerve are more excitable only when the stimulating current passes in a 
 descending direction ; the reverse is the case when the current ascends {Hermann, 
 Fleischl). On stimulating a sensory nerve, Rutherford and Hallsten found that 
 the reflex contraction was greater the nearer the point stimulated was to the cen- 
 tral nervous system. 
 
 Unequal Excitability in the same Nerve. — Nerve fibres, even when func- 
 tionally the same and included in the same nerve trunk, are not all equally excitable. 
 Thus feeble stimulation of the sciatic nerve of a frog causes contraction of the 
 flexor muscles, while it requires a stronger stimulus to produce contraction of the 
 extensors {Ritter, 1805, Rolletf). According to Ritter, the nerves for the flexors 
 die first. 
 
 Direct stimulation of the muscles in curarized animals shows that the flexors contract with a 
 feebler stimulus (but also fatigue sooner) than the extensors; the pale muscles of the rabbit are 
 also more excitable than the red. As a rule, poisons affect the flexors sooner than the extensors. 
 In some muscles some pale fibres are present, and they are more excitable than the red ( Griitzner) 
 (I 298). 
 
 ■ Unipolar Stimulation. — If one electrode of an induction apparatus be ap- 
 plied to a nerve it may act as a stimulus. Du Bois-Raymond has called this 
 "unipolar induction action." It is due to the movement of the electric current 
 to and from the free ends of the open induction current at the moment of induc- 
 tion. [Unipolar induction is more apt to occur with the opening than the closing 
 shock, because the former is more intense.] 
 
 Upon muscle electrical stimuli act quite as they do upon nerves. Elec- 
 trical currents of very short duration have no effect upon muscles whose nerves are 
 paralyzed by curara {Briicke), and the same is true of greatly fatigued muscles, or 
 muscles about to die or greatly weakened by diseased condition (§ 399). 
 
 325. DIMINUTION OF THE EXCITABILITY— DEGENERA- 
 TION AND REGENERATION OF NERVES.— 1. Normal Nutri- 
 tion. — The continuance of the normal excitability in the nerves of the body 
 depends upon the maintenance of the normal nutrition of the nerves themselves 
 and a due supply of blood. Insufficient nutrition causes in the first instance in- 
 creased excitability, and if the condition be continued the excitability is dimin- 
 ished (§ 339, I). 
 
 When the physician meets with the signs of increased excitability of the nerves, under bad or 
 abnormal conditions of nutrition, this is to be regarded as the beginning of the stage of decrease of 
 the nerve energy. Invigorating measures are required. 
 
 If the terminal nervous apparatus be subjected to a temporary disturbance of its 
 nutrition, the return of the normal nutritive process is heralded by a more or less 
 marked stage of excitement. The more excitable the nervous apparatus the 
 shorter must be the duration of the disturbance of nutrition, e.g., cutting off 
 the arterial blood supply or interfering with the respiration. 
 
 2. Fatigue. — Continued excessive stimulation of a nerve, without sufficient 
 intervals of repose, causes fatigue of the nerve, and by exhaustion rapidly dimin- 
 ishes the excitability. A nerve is more slowly fatigued than a muscle {Bernstein), 
 but it recovers more slowly (§ 304). [Nerves of cold-blooded animals ( Widenskii) 
 and mammals {Bowditch) may be tetanized for hours without becoming fatigued.] 
 
SEPARATION FROM NERVE CENTRES. 
 
 573 
 
 Recovery. — When a nerve recovers, at first it does so slowly then more rap- 
 idly, and afterward again more slowly. If recovery does not occur within half 
 an hour after a frog's nerve has been subjected to very long and intense stimula- 
 tion, it will not take place at all. 
 
 3. Continued inaction of a nerve diminishes and may ultimately abolish 
 the excitability. 
 
 Fig. 342. 
 
 ABC D E 
 
 Degeneration and regeneration of nerves. A, subdivision ot the myelin: 
 B, further disintegration thereof (osmic acid staining) ; C, interruption 
 of the axial cylinder, which is surrounded with the broken-up myelin ; 
 D, accumulation of nuclei, with the remainder of the myelin in a 
 spindle-shaped fibre; E, a new nerve fibre passing in a curved course 
 through an old nerve-fibre sheath : F, a new nerve fibre, with a new 
 sheath of Schwann, sn, within the old sheath of Schwann, sa. 
 
 Thus the central ends of divided sensory nerves, after amputation of a limb, lose their excita- 
 bility, although the nerves are still connected with the central nervous system, because the end 
 organs through which they were normally excited have been removed. 
 
 4. Separation from their Nerve Centres. — The nerve fibres remain in a 
 condition of normal nutrition only when they are directly connected with their 
 centre, which governs the nutritive processes within the nerve. If a nerve 
 
574 
 
 TRAUMATIC AND FATTY DEGENERATION. 
 
 within the body be separated from its centre — either by section of the nerve or 
 compressing it — within a short time it loses its excitability, and the peripheral 
 end undergoes fatty degeneration, which begins in four to six days in warm-blooded 
 animals, and after a long time in cold-blooded ones (Joh. Mutter). See also the 
 changes of the excitability during this condition, the so-called " Reaction of 
 degeneration" (§ 339). If the sensory nerve fibres of the root of a spinal 
 nerve be divided on the central side of the ganglion, the fibres on the peripheral 
 side do not degenerate, for the ganglion is the trophic or nutritive centre for the 
 sensory nerves, but the fibres still in connection with the cord degenerate ( Waller, 
 Bidder). 
 
 [Wallerian Law of Degeneration. — If a spinal nerve be divided, the 
 peripheral part of the nerve and its branches, including the sensory and motor 
 fibres, degenerate completely (Fig. 343, A), while the central parts of the nerve 
 remain unaltered. If the anterior root of a spinal nerve alone be divided before 
 it joins the posterior root, all the peripheral nerve fibres connected with the an- 
 terior root degenerate (Fig. 343, B), so that in the nerve of distribution only the 
 motor fibres degenerate. The portion of the nerve root which remains attached to 
 the cord does not regenerate. If the posterior root alone be divided, between the 
 spinal cord and the ganglion, the effect is reversed, the part of the nerve root 
 lying between the section and the spinal cord degenerates, while the part of- the 
 
 Fig. 343. 
 
 Diagram of the roots of a spinal nerve showing the effect of section (the black parts represent the degenerated parts). 
 A, section of the nerve trunk beyond the ganglion ; B, of the anterior root, and C, of the posterior ; D, excision 
 of the ganglion ; a, anterior,/, posterior root; g, ganglion. 
 
 nerve connected with the ganglion does not degenerate (Fig. 343, C). The cen- 
 tral fibres degenerate because they are separated from the ganglion. If the gan- 
 glion be excised, or if separated, as in Fig. 343, D, both the central and peri- 
 pheral parts of the posterior root degenerate. These experiments of Waller show 
 that the fibres of the anterior and posterior roots are governed by different cen- 
 tres of nutrition or " trophic centres." As the anterior root degenerates when 
 it is separated from the cord, and the posterior when it is separated from its own 
 ganglion, it is assumed that the trophic centre for the fibres of the anterior root 
 lies in the multipolar nerve cells of the anterior horn of the gray matter of the 
 spinal cord, while that for the fibres of the posterior root lies in the cells of the 
 ganglion placed on it. The nature of this supposed trophic influence is entirely 
 unknown.] 
 
 Traumatic and Fatty Degeneration. — Both ends of the nerve at the point of section imme- 
 diately begin to undergo " traumatic degeneration." (In the frog on the first and second day.) After 
 a time, neither the myelin nor axis cylinder are distinguishable [Schiff). According to Engelmann, 
 this condition extends only to the nearest node of Ranvier, and afterward the so-called "fatty degen- 
 eration" begins. The process of "fatty" degeneration begins simultaneously in the whole peripheral 
 portion ; the white substance of Schwann breaks up into masses (Fig. 342, A), just as it does after 
 death, in microscopic preparations; afterward, the myelin forms globules and round masses (B), 
 the axial cylinder is compressed or constricted, and is ultimately broken across (C) in many places 
 (7th day). The nerve fibre seems to break up into two substances — one fatty, the other proteid in 
 
TROPHIC CENTRES AND EFFECTS OF POISONS ON NERVES. 575 
 
 constitution (S. Mayer), the fat being absorbed. The nuclei of Schwann's sheath swell up and 
 proliferate (D— until the tenth day). According to Ranvier, the nuclei of the interannular segments 
 and their surrounding protoplasm proliferate, and ultimately interrupt the continuity of the axis 
 cylinder and the myelin. They then undergo considerable development with simultaneous disap- 
 pearance of the medulla and axis cylinder, or at least the fatty substances formed by their degenera- 
 tion, so that the nerve fibres look like fibres of connective tissue. [According to this view, the pro- 
 cess is in part an active one, due to the growth of the nerve corpuscles breaking up the contents of 
 the neurilemma, which then ultimately undergo chemical degenerative changes.] According to 
 Ranvier, Tizzoni, and others, leucocytes wander into the cut ends of the nerves, and also at Ran- 
 vier's nodes, insinuating themselves into the nerve fibres, where they take myelin into their bodies, 
 and subject it to certain changes. [These cells are best revealed by the action of osmic acid, which 
 blackens any myelin particles in their interior.] Degeneration also takes place in the motorial end 
 plates, beginning first in the non-medullated branches, then in the terminal fibrils, and lastly in the . 
 nerve trunks ( Gessler). 
 
 Regeneration of Nerves. — In order that regeneration of a divided nerve may take place 
 (Cruickskank, iJQjj), the divided ends of the nene must be brought into contact (§ 244). In man 
 this is done 'by means of sutures. About the middle of the fourth week; small clear bands appear 
 within the neurilemma, winding between the nuclei and the remains of the myelin (E). They soon 
 become wider, and receive myelin with incisures, and nodes, and a sheath of Schwann (second to 
 third month — F). The regeneration process takes place in each interannular segment, while the in- 
 dividual segments unite end to end at the nodes of Ranvier ($ 321, I, 5). On this view, each 
 nerve segment of the fibre corresponds to a " cell unit " (£. Neumann, Eichhorst). The same 
 process occurs in nerves ligatured in their course. Several new fibres may be formed within one 
 old nerve sheath. The divided axis cylinders of the central end of the nerve begin to grow about 
 the fourteenth day, until they meet the newly formed ones, with which they unite. 
 
 [Primary and Secondary Nerve Suture. —Numerous experiments on animals and man have 
 established the fact that immediate or primary suture of a nerve, after it is divided, either acci- 
 dentally or intentionally, hastens reunion and regeneration, and accelerates the restoration of 
 function. Secondary suture, i.e., bringing the ends together long after the nerve has been 
 divided, has been practiced with success. Surgeons have recorded cases where the function was 
 restored after division had taken place for 3 to 16 months, and even longer, and in most cases the 
 sensibility was restored first, the average time being 2 to 4 weeks. Motion is recovered much 
 later. The ends of the nerve should be stitched to each other with catgut, the muscles at the same 
 time being kept from becoming atrophied by electrical stimulation and the systematic use of 
 massage ({j 307). After suture of a nerve conductivity is restored in the rabbit in 40 days, on the 
 31st in dogs, and 25th in fowls, but after simple division without suture not till the 60th day in the 
 rabbit. Transplantation of nerve does not succeed (Johnson).] 
 
 Union of Nerves.— The central end of a divided motor nerve may unite with the peripheral 
 end of another and still conduct impulses (Rava). [There seems to be no doubt that sensory 
 fibres will reunite with sensory fibres, and motor fibres with motor fibres, and the regenerated nerve 
 will, in the former case, conduct sensory impulses, and the latter motor impulses. There is very 
 considerable diversity of opinion, however, as to the regeneration or union of sensory with motor 
 fibres. Paul Bert made the following experiment : He stitched the tail of a rat into the animal's 
 back, and after union had taken place, he cut the tail from the body at the root, so that the tail, as 
 it were, grew out of the animal's back, broad end uppermost. On irritating the end of the tail, 
 which was formerly the root, the animal gave signs of pain. This experiment shows that nerve 
 fibres can conduct impulses in both directions. One of two things must have occurred. Either 
 the motor fibres, which normally carried impulses down the tail, now convey them in the opposite 
 direction, and convey them to sensory fibres with which they have united; or the sensory fibres, 
 which normally conducted impulses from the tip upward, now carry them in the opposite direction. 
 If the former weie actually what happened it would show that nerve fibres of different function do 
 unite (\ 349). Reichert asserts that he has succeeded in uniting the hypoglossal with the vagus in 
 the dog. According to Gessler, the end plate is the first to regenerate.] 
 
 Trophic Centres. — The regeneration of the nerve seems to take place under 
 the influence of the nerve centres, which act as their nutritive or trophic 
 centres. Nerves permanently separated from these centres never regenerate. 
 
 During the regeneration of a mixed nerve, sensibility is restored first, subse- 
 quently voluntary motion, and lastly, the movements of the muscles, when their 
 motor nerves are stimulated directly (Schiff, Erb, v. Ziemssen, and others). 
 
 Wallerian Method of Investigation. — As Hie peripheral end of a nerve undergoes degenera- 
 tion after section, we use this method for determining the course of nerve fibres in a complex 
 arrangement of nerves. The course of special nerve fibres may be ascertained by tracing the 
 degeneration tract ( Waller, Budge). If, after section, reunion or regeneration of a motor nerve 
 does not take place, the muscle supplied by this nerve ultimately undergoes fatty degeneration. 
 
576 RITTER-VALLI LAW. 
 
 5. Certain poisons, such as veratrin, at first increase the excitability of the 
 nerves, and afterward abolish it ; with some other poisons, the abolition of the 
 excitability passes off very rapidly, e.g., curara. Conium, cynoglossum, iodide 
 of methyl-strychnin, and iodide of sthyl-strychnin have a similar action. 
 
 If the nerve or muscle of a frog be placed in a solution of the poison, we obtain a different effect 
 from that which results when the poison is injected into the body of the animal. Atropin 
 diminishes the excitability of a nerve-muscle preparation of the frog without causing any previous 
 increase, while alcohol, ether and chloroform increase and then diminish the excitability (Momm- 
 sen). 
 
 6. Modifying Conditions. — Under the action of various operations, e.g., 
 compressing a nerve [so as not absolutely to sever the physiological continuity], 
 it has been found that voluntary impulses or stimuli applied above the compressed 
 spot, give rise to impulses which are conducted through the nerve, and in the 
 case of a motor nerve cause contraction of the muscles, while the excitability of 
 the parts below the injured spot is greatly diminished (Schiff). In a similar 
 manner it is found that the nerves of animals poisoned with C0 2 , curara or 
 coniin, sometimes even the nerves of paralyzed limbs in man, are not excitable to 
 direct stimuli, while they are capable of conducting impressions coming from 
 the central nervous system (Duchenne, v. Ziemssen, £rb). 
 
 7. Ritter-Valli Law. — If a nerve be separated from its centre, or if the 
 centre dies, the excitability of the nerve is increased ; the increase begins at the 
 central end, and travels toward the periphery — the excitability then falls until it 
 disappears entirely. This process takes place more rapidly in the central than 
 in the peripheral part of the nerve, so that the peripheral end of a nerve separated 
 from its centre remains excitable for a longer time than the central end. 
 
 The rapidity of the transmission of impulses in a nerve is increased when the excitability is 
 increased, but it is lessened when the excitability is diminished. In the latter condition an electrical 
 stimulus must last longer in order to be effective ; hence rapid induction shocks may not produce 
 any effect. 
 
 The law of contraction also undergoes some modification in the different stages of the changes 
 of excitability (J 336, II). 
 
 8. Excitable Points. — Many nerves are more excitable at certain parts of 
 their course than at others, and the excitability may last longer at these parts. 
 One of these parts is the upper third of the sciatic nerve of a frog, just where a 
 branch is given off {Budge, Heidenhain). 
 
 The motor and sensory fibres of the upper third of the sciatic nerve (Hallstln) of a frog is more 
 excitable for all stimuli (Griitzner and Elpon) than the lower parts. Whether this arises from 
 injury during preparation (a branch is given off there), or is due to anatomical conditions, e.g., 
 more connective tissue and more nodes in the lower part of the sciatic, is undetermined (Clara 
 Halperson). 
 
 This increased excitability may be due to injury to the nerve in preparing it for experiment. 
 After section or compression of a nerve, all electrical currents employed to stimulate the nerve are 
 far more active when the direction of the current passes away from the point of injury than when 
 it passes in the opposite direction. This is due to the fact that the current produced in the nerve 
 after the lesion is added to the stimulation current (\ 331, 5). Even in intact nerves — sciatic of a 
 frog (v. Fleischl}, where the nerve ends at the periphery or at the centre, or where large branches 
 are given off, there are points which behave in the same way as those points where a lesion has 
 taken place ( Griitzner and Moschner). 
 
 Death of a Nerve. — In a dead nerve the excitability is entirely abolished, 
 death taking place, according to the Ritter-Valli Law, from the centre toward the 
 periphery. The reaction of a dead nerve has been found by some observers to 
 be acid (§ 322). 
 
 The functions of the brain cease immediately after death takes place, while the vital functions of 
 the spinal cord, especially of the white matter, last for a short time ; the large nerve trunks gradually 
 die, then the nerves of the extensor muscles, those of the flexors after three to four hours; while 
 the sympathetic fibres retain their excitability longest, those of the intestine even for ten hours 
 {Onimus). Compare \ 295. The nerves of a dead frog may remain excitable for several days, 
 provided the animal he kept in a cool place. 
 
ELECTRO-PHYSIOLOGY. 577 
 
 ELECTRO-PHYSIOLOGY.— Before beginning the'study of electro-phys- 
 iology, the student ought to read and study carefully the following short prelimi- 
 nary remarks on the physics of this question : — 
 
 326. PHYSICAL PRELIMINARY STATEMENTS— THE GALVANIC CUR- 
 RENT — RHEOCORD. — 1. Electro-motive Force. — If two of the under-mentioned bodies 
 be brought into direct contact, in one of them positive electricity and in the other negative electricity 
 can be detected. The cause of this phenomenon is the electro- motive force. The electro-motive 
 substances may be arranged in a series of the first class, so that if the first-mentioned substance 
 be brought into contact with any of the other bodies, the first substance is negatively the last posi- 
 tively electrified. This series is — carbon, platinum, gold, silver, copper, iron, tin, lead, zinc -|- . 
 
 The amount of the electro-motive force produced by the contact of two of these bodies is greater 
 the wider the bodies are apart in the series. The contact of the bodies may take place at one or 
 more points. If several ol the bodies of this series be arranged in a pile, the electrical tension 
 thereby produced is just as great as if the two extreme bodies were brought into contact, the inter- 
 mediate ones being left out. 
 
 2. The nature of the two electricities is readily determined by placing one of the bodies of the 
 series in contact with a fluid. If zinc be placed in pure or acidulated water, the zinc is -\- (posi- 
 tive) and the water — (negative). If copper be taken instead of zinc, the copper is -\- but the 
 fluid — . Experiment shows that those metals, in contact with fluid, are negatively electrified most 
 strongly which are most acted on chemically by the fluid in which they are placed. Each such 
 combination affords a constant difference of tension or potential. The tension [or power of over- 
 coming resistance] of the amount of electricity obtained from both bodies depends upon the size of 
 the surfaces in contact. The fluids, e.g., the solutions of acids, alkalies, or salts are called exciters 
 of electricity of the second class. They do not form among themselves a definite series with 
 different tensions. When placed in these fluids, the metals lying next the -|- end of the above series, 
 especially zinc, are most strongly electrified negatively, and to a less extent those lying nearer the 
 — end of the series. 
 
 3. Galvanic Battery. — If two different exciters of the first class be placed in fluid without the 
 bodies coming into contact, e.g., zinc and copper, the projecting end of the (negative) zinc shows 
 free negative electricity, while the free end of the (positive) copper shows free positive electricity. 
 Such a combination of two electromotors of the first class with an electromotor of the second class 
 is called & galvanic battery. As long as the two metals in this fluid are kept separate the circuit is 
 said to be open, but as soon as the free projecting ends of the metals are connected outside the fluid, 
 e. g., by a copper wire, the circuit or current is closed, and a galvanic or constant current of elec 
 tricity is obtained. The galvanic current has resistance to encounter in its course, which is called 
 "conduction resistance'' (W). It is directly proportional — (1) to the length (I) of the circuit; (2) 
 and with the same length of circuit, inversely as the section (q) of the same ; and (3) it also de- 
 pends on the molecular properties of the conducting material (specific conduction resistance = s), 
 so that the conduction resistance, W = ( s. I) : q. The resistance to conduction increases with the 
 increase of the temperature of the metals, but diminishes under similar conditions with fluids. 
 
 Ohm's Law. — The strength of a galvanic current (S), or the amount of electricity passing 
 through the closed circuit, is proportional to the electro-motive force (E) — or the electrical tension, 
 but inversely proportional to the total resistance to conduction (L) — 
 So that S = E : L (Ohm's Law, 1827). 
 
 The total resistance to conduction, however, in a closed circuit is composed of — (1) the resist- 
 ance outside the battery ("extraordinary resistance") ; and (2) the resistance within the battery 
 itself (" essential resistance "). The specific resistance to conduction is very variable in different 
 substances ; it is relatively small in metals (e. g., for copper = 1, iron = 6.4, German silver = 12), 
 but very great in fluids (e.g., for a concentrated solution of common salt 6,515,000, for a concen- 
 trated solution of copper sulphate 10,963,600). It is also very great in animal tissues, almost a . 
 million times greater than in metals. When a constant current is applied to the skin so as to traverse 
 the body, the resistance diminishes because of the conduction of water in the epidermis under the 
 action of the constant current (\ 290), and the congestion of the cutaneous blood vessels in conse- 
 quence of the stimulation. But the resistance varies in different parts of the skin, the least being 
 in the palm of the hand and sole of the foot. The chief seat of the resistance is the epidermis, 
 but after its removal, as by a blister, it is greatly diminished. Dead tissue, as a rule, is a worse 
 conductor than living tissues {Jolly). When the current is passed transversely to the direction of 
 the fibres of a muscle, the resistance is nearly nine times as great as when the current passes in the 
 direction of the fibres (Hermann) — a condition which disappears in vigor mortis. In nerves the 
 resistance longitudinally is two and a half million times greater than in mercury, transversely about 
 twelve million times (Hermann). Tetanus and rigor mortis (Du Bois-Reymond) diminish the re- 
 sistance in muscle. 
 
 Deductions. — It follows from Ohm's law that — I. If there is very great resistance to the current 
 outside the battery [z. e., between the electrodes] , as in the case when a nerve or a muscle lies on 
 the electrodes, the strength of the current can only be increased by increasing the number of the 
 electro-motive elements. II. When, however, the extraordinary resistance is very small compared 
 
 37 
 
578 ACTION OF GALVANIC CURRENT ON A MAGNETIC NEEDLE. 
 
 Fig 
 
 with that within the battery itself, the strength of the current cannot be increased by increasing the 
 number of the elements, but only by increasing' the surfaces of the plates in the battery. 
 
 Strength and Density. — We must carefully distinguish the strength (intensity) of the current 
 from its density. As the same amount of electricity always flows through any given transverse sec- 
 tion of the circuit, then, if the size of the transverse section of the circuit varies, the electricity must 
 be of greater density in the narrower parts, and it is evident that the density will be less where the 
 transverse section is greater. Let S = the strength of the current, and q the transverse section of 
 the given part of the circuit, then the density (d) at the latter part is d = S : q. 
 
 If the galvanic current passing from the positive pole of a battery be divided into two or more 
 streams, which are again reunited at the other pole, then the sum of the strength of ail the streams 
 is equal to the strength of the undivided stream. If, however, the different streams are different as 
 regards length, section and material, then the strength of the current passing in each of the streams 
 is inversely proportional to the resistance to the conduction. 
 
 Du Bois-Reymond's Rheocord. — This instrument, constructed on the principle of the " second- 
 ary " or " short circuit," enables us to graduate the strength of a galvanic current to any required 
 
 degree, for the stimulation of nerve and muscle. From the 
 two poles (Fig. 344, a, b) of a constant battery there are two 
 conducting wires (a, c and d, b), which go to the nerve of a 
 frog's nerve-muscle preparation (F). The portion of nerve 
 (c, a) introduced into this circuit (a, c, d, b) offers very great 
 resistance. The second stream or secondary circuit (a A, 
 b B), conducted from a and b, passes through a thick brass 
 plate (A, B), consisting of seven pieces of brass (i to 7) 
 placed end to end, but not in contact. They can all, with 
 the exception of I and 2, be made to form a continuous con- 
 ductor by placing in the spaces between them the brass 
 plugs (S 1 to S 5 ). Evidently, with the arrangement shown 
 in Fig. 344, on^y a minimal part of the current will pass 
 through the nerve (c, d) owing to the very great resistance 
 in it, while by far the greatest part will pass through the 
 good conducting medium of brass (A, L, B). If new 
 resistance be introduced into this circuit, then the a, c, d, b 
 stream will be strengthened. This resistance can be intro- 
 duced into the latter circuit by means of the thin wires 
 marked I a, I b, I c, II, V, X. Suppose all the brass plugs 
 from bj to S 5 to be removed, then the current entering at A 
 must traverse the whole system of thin wires. Thus, there 
 is more resistance to the passage of this current, so that the 
 current through the nerve must be strengthened. If only 
 one brass plug be taken out, then the current passes through 
 only the corresponding length of wire. The resistances 
 offered by the different lengths of wire from 1 a to X are so 
 arranged that I a, I b and I c each represent a unit of resist- 
 ance ; II, double ; V, five times ; and X, ten times the 
 resistance. The length of wire, I a, can also be shortened 
 by the movable bridge (L) [composed of a small tube filled 
 with mercury, through which the wires pass], the scale (x, y) 
 indicating the length of the resistance wires. It is evident 
 that, by means of the bridge and by the method of using the 
 brass plugs, the apparatus can be graduated to yield very 
 variable currents for stimulating nerve or muscle. When the bridge (L) is pushed hard up to I, 2, 
 the current passes directly from A to B, and not through the thin wires (I a). 
 
 The rheostat is another instrument used to vary the resistance of a galvanic current ( Wheatstone). 
 
 327. ACTION OF THE GALVANIC CURRENT ON A MAGNETIC NEEDLE 
 
 THE GALVANOMETER.— In 1820 Oerstedt, of Copenhagen, found that a magnetic 
 
 needle suspended in the magnetic meridian was deflected by a constant current of electricity passed 
 along a wire parallel to it. [The side to which the north pole is deflected depends upon the 
 direction of the current, and whether it passes above or below the needle.] 
 
 Ampere's Rule. — Ampere has given a simple rule for determining the direction. If an observer 
 be placed parallel to and facing the needle, and if the current be passing from his feet to his head, 
 then the north pole of the needle will always be deflected to the left, and the south pole in the 
 opposite direction. The effect exerted by the constant current acts always in a direction toward 
 the so-called electro-magnetic plane. The latter is the plane passing through the north pole of the 
 needle, and two points in the straight wire running parallel with the needle. The force of the con- 
 stant current, which causes the deflection of the magnetic needle, is proportional to the sine of the 
 angle between the electro-magnetic plane and the plane of vibration of the needle. 
 
 Scheme of Du Bois-Reymond's rheocord. 
 
ELECTROLYSIS, POLARIZATION, BATTERIES. 579 
 
 MultipHcator [or Multiplier]. — The deflection of the needle caused by the constant current 
 may be increased by coiling the conducting wire many times in the same direction on a rectangular 
 frame, or merely around and in the same direction as the needle [provided that each turn of the 
 wire be properly insulated from the other]. An instrument constructed on this principle is called a 
 multiplier. The greater the number of turns of the wire the greater is the angle of deflection of the 
 needle, although the deflection is not directly proportional, as the several turns or coils are not at 
 the same distance from, or in the same position as, the needle. By means of the multiplier we may 
 detect the presence [and also the amount and direction] of feeble currents. [The instrument is 
 now termed a Galvanometer], Experience has shown that, when great resistance (as in animal 
 tissues) is opposed to the weak galvanic currents, we must use a very large number of turns of thin 
 wire round the needle. If, however, the resistance in the circuit is but small, e.g., in thermo- 
 electrical arrangement', a few turns of a thick wire round the needle are sufficient. The multiplier 
 may be made more sensitive by weakening the magnetic directive force of the needle, which keeps 
 it pointing to the north. 
 
 Galvanometer and Astatic Needles. — In the multiplier of Schweigger, used for physiological 
 purposes, the tendency of the needle to point to the north is greatly weakened by using the astatic 
 needles of Nobili. [A multiplier or galvanometer with a single magnetic needle always requires 
 comparatively strong currents to deflect the needle. The needle is continually acted upon by 
 the directive magnetic influence of the earth, which tends to keep it in the magnetic meridian, and 
 as soon as it is moved out of the magnetic meridian the directive action of the earth tends to bring 
 it back. Hence, such a simple form of galvanometer is not sufficiently sensitive for detecting feeble 
 currents. In 1827 Nobili devised an astatic combination of needles, whereby the action of the 
 earth's magnetism was diminished.] Two similar magnetic needles are united by a solid light 
 piece of horn [or tortoise shell] , and are so arranged that the north pole of the one is placed over 
 or opposite to the south pole of the other (Fig. 345). [If both needles are equally magnetized, 
 then the earth's influence on the needle is neutralized, so that the needles no longer adjust them- 
 selves in the magnetic meridian ; hence, such a system is called astatic] As it is impossible to 
 make both needles of absolutely equal magnetic strength, one needle is always stronger than the 
 other. The difference, however, must not be so great that the stronger needle points to the north, 
 but only that the freely suspended system of needles forms a certain angle with the magnetic meri- 
 dian, into which position the system always swings after it is deflected from this position. This 
 angular deviation of the astatic system toward the magnetic meridian is called the " free deviation." 
 The more perfectly an astatic condition is reached, the nearer the angle formed by the direction of 
 the free deviation with the magnetic meridian becomes a right angle. The greater, therefore, the 
 astatic condition, the astatic system will make the fewer vibrations in a given time, after it has been 
 deflected from its position. The duration of each single vibration is also very great. [Hence, 
 when using a galvanometer, and adjusting its needle to zero, if the magnets dance about or move 
 quickly, then the system is not sensitive, but a sensitive condition of the needles is indicated by a 
 slow period of oscillation.] 
 
 In making a galvanometer, the turns of the wire must have the same direction as the needles. 
 In Nobili's galvanometer, as improved by Du Bois-Reymond, the upper needle swings above a card 
 divided into degrees (Fig. 345), on which the extent of its deflection may be read off. Even the 
 purest copper wire used for the coils round the needles always contains a trace of iron, which exerts 
 an influence upon the needles. Hence, a small fixed directive or compensatory magnet (r) is 
 placed near one of the poles of the upper needle to compensate for the action of the iron on the 
 needles. 
 
 328. ELECTROLYSIS, POLARIZATION, BATTERIES.— Electrolysis.— Every 
 galvanic current which traverses a fluid conductor causes decomposition or electrolysis of the fluid. 
 The decomposition products, called ions, accumulate at the poles (electrodes) in the fluid, the 
 positive pole (+ ) being called the anode [avd, up, vSuq, a way], the n^ative pole ( — ) the 
 cathode {xard, down, (5i!i!j, a way). The anions accumulate at the anode and the kations at 
 the cathode. 
 
 Transition Resistance. — When the decomposition products accumulate upon the electrodes, 
 by their presence they either increase. or diminish the resistance to the electrical Current. This is 
 called transition resistance. If the resistance within the battery is thereby increased, the transition 
 resistance is said to be positive ; if diminished, negative. 
 
 Galvanic Polarization. — The ions accumulated on the electrodes may also vary the strength 
 of the current, by developing between the anions and kations a new galvanic current, just as occurs 
 between two different bodies connected by a fluid medium. This phenomenon is called galvanic 
 polarization. Thus, when water is decomposed, the electrodes being of platinum, the oxygen 
 (negative) accumulates at the -|- pole, and the hydrogen (positive) at the — pole. Usually, the 
 polarization current has a direction opposite to the original current ; hence we speak of negative 
 polarisation. When the two currents have the same direction, positive polarization obtains. Of 
 course, transition resistance and polarization may occur together during electrolysis. 
 
 Test. — Polarization, when present, may be so slight as not to be visible to the eye, but it may be 
 detected thus : After a time, exclude the primary source of the current, especially the element con^ 
 
580 
 
 CONSTANT BATTERIES, ELEMENTS, OR CELLS. 
 
 nected with the electrodes, and place the free projecting end of the electrodes in connection with 
 a galvanometer, which will at once indicate, by the deflection of its needle, the presence of even 
 the slightest polarization. 
 
 Secondary Decompositions. — The ions excreted during electrolysis cause, especially at their 
 moment of formation, secondary decompositions. With platinum electrodes in a solution of common 
 salt, chlorine accumulates at the anode and sodium at the cathode ; but the latter at once decom- 
 poses the water, and uses the oxygen of the water to oxidize itself, while the hydrogen is deposited 
 secondarily upon the cathode. The amount of polarization increases, although only to a slight 
 extent, with the strength of the current, while it is nearly proportional to the increase of the tem- 
 perature. The attempts to get rid of polarization, which, obviously, must very soon alter the strength 
 of the galvanic current, have led to the discovery of two important arrangements, viz., to the con- 
 struction of constant galvanic batteries {Becquerel), and the so-called non-polarizable elec- 
 trodes (Z>« Bois-Reymond). 
 
 Constant Batteries, Elements, or Cells. — A perfectly constant element produces a constant 
 current, i. e., one remaining of equal strength, by the ions produced by the electrodes being got rid 
 of the moment they are formed, so that they cannot give rise to polarization. For this purpose each 
 
 Fig- 345- 
 
 r P 
 
 Scheme of the galvanometer. N, N, astatic needles sus- 
 pended by the silk fibre, G; P, P, non-polarizable elec- 
 trodes, containing zinc-sulphate solution, s, and pads of 
 blotting paper, b, covered with clay, t, t, on which the 
 muscle, M, is placed ; XI, III, arrangements of the mus- 
 cle on the electrode ; IV, non-polarizable electrodes ; Z, 
 zinc wire ; K, cork ; a, zinc-sulphate solution ; t, t, clay 
 points. 
 
 Fig. 346. 
 
 Large Grove's element. 
 
 of the substances from the tension series used is placed in a special fluid (\ 326), both fluids being 
 separated by a porous septum (porcelain cylinder). 
 
 Grove's Element has two metals and two fluids (Fig. 346). The zinc is in the form of a roll 
 placed in dilute sulphuric acid [1 acid to 7 of water, which is contained in a glass, porcelain or 
 ebonite vessel]. The platinum is in contact with strong nitric acid [which is contained in a porous 
 cell placed inside the roll of zinc]. The O, formed by the electrolysis and deposited on the zinc 
 plate, forms zinc oxide, which is at once dissolved by the sulphuric acid. The hydrogen on the 
 platinum unites at once with the nitric acid, which gives up O and forms nitrous acid and water, thus — 
 [H 2 + HNO s = HN0 2 + H 2 0.] 
 [Platinum is the -j- pole, and zinc the — .] 
 
 [Grove's battery is very powerful, but the nitrous fumes are very disagreeable and irritating; 
 hence these elements should be kept in a special, well- ventilated Tecess in the laboratory, in an evap- 
 orating chamber, or under glass. The fumes also attack instruments.] 
 
 Bunsen's Element is quite similar to Grove's, only a piece of compressed carbon is substituted 
 for the platinum in contact with the nitric acid. 
 
 [The carbon is the -f pole, the zinc the — .] 
 
DANIELL, SMEE, GRENNET AND LECLANCHE'S ELEMENTS. 581 
 
 [Daniell's Element (1836). — It consists of an outer vessel or glass of earthenware, and some- 
 times of metallic copper, filled with a saturated solution of cupric sulphate. A roll of copper, per- 
 forated with a few holes, is placed in the copper solution, and in order that the latter be kept satu- 
 rated, and to supply the place of the copper used up by the battery when in action, there is a small 
 shelf on the copper roll, on which are placed crystals of cupric sulphate. A porous earthenware 
 vessel containing zinc in contact with dilute sulphuric acid (1 : 7) is placed within the copper 
 cylinder.. When the circuit is completed, the zinc is acted on, zinc sulphate being formed, and 
 hydrogen liberated. The hydrogen in statu nascendi passes through the porous cell, reduces the' 
 cupric sulphate to metallic copper, which is precipitated on the copper cylinder, so that the latter is 
 always kept bright and clean. The liberated sulphuric acid replaces that in contact with the zinc. 
 Owing to the absence of polarization, the Daniell is one of the' most constant batteries, and is gen- 
 erally taken as the standard of comparison.] 
 
 [The copper is the + pole, zinc the — .] 
 
 Fig. 348. 
 
 Fig. 347. 
 
 
 Grennet's element. A, the glass vessel ; K, 
 K, carbon ; Z, zinc ; D, E, binding screw 
 for the wires ; B, rod to raise or depress 
 the zinc in the fluid ; C, screw to fix B. 
 
 Leclanche's element. A, outer vessel ; T, porous cylinder, containing 
 K, carbon; B, binding screw; Z, zinc; C, binding screw of nega- 
 tive pole. 
 
 [Smee's Element. — There is only one fluid, viz., dilute sulphuric acid (1:7), in which the 
 two metals, zinc and platinum, or zinc and platinized silver, are placed. 
 The platinum is the -\- pole, and zinc the — .] 
 
 [Grennet's or the Bichromate Element. — It consists of one plate of zinc and two plates 
 of compressed carbon in a fluid, which consists of bichromate of potash, sulphuric acid, and 
 water. The fluid consists of 1 part of potassium bichromate dissolved in 8 parts of water, to which 
 I part of sulphuric acid is added. Measure by weight.'] [The cell consists of a wide-mouthed 
 glass bottle (Fig. 347) ; the carbons remain in the fluid, while the zinc can be raised or depressed. 
 When not in action, the zinc, which is attached to a rod (B), is lifted out of the fluid, and hence 
 this battery is very convenient for purposes of demonstration, although it is not a very constant 
 battery. When in action, the ziuc is acted on by the sulphuric acid, hydrogen being liberated, 
 which reduces the bichromate of potash. 
 
 The carbon is the -\- pole, and the zinc the — .] 
 
 [Leclanche's Element (Fig. 348) consists of an outer glass vessel containing zinc in a solution 
 of ammonium chloride, while the porous cell contains compressed carbon in a fluid mixture of black 
 
582 
 
 REFLECTING GALVANOMETER AND SHUNT. 
 
 oxide of manganese and carbon. It is most frequently used for electric bells, as its feeble current 
 lasts for a long time. 
 
 The carbon is the -f- pole, and the zinc the — .] 
 
 Non-polarizable Electrodes. — If a constant current be applied to moist animal tissues; e.g., 
 nerve or muscle, by means of ordinary electrodes composed either of copper or platinum, of course 
 electrolysis must occur, and in consequence thereof polarization takes place. In order to avoid 
 this, non-polarizable electrodes (Figs. 345 and 349) are used. The researches of Regnault, Mat- 
 teucci and Du Bois-Reymond have proved that such electrodes can be made by taking two pieces 
 of carefully amalgamated pure zinc wire (2, z), and dipping these in a saturated solution of zinc 
 sulphate contained in tubes (a, a), their lower ends being closed by means of modeller's clay (t, t), 
 moistened with 0.6 per cent, normal saline solution. The contact of the tissues with these elec- 
 trodes does not give rise to polarity. 
 
 Arrangement for the Muscle or Nerve Current. — In order to investigate the electrical cur- 
 rents of nerve or muscle, the tissue must be placed on non-polarizable electrodes, which may either 
 have the form described above, or the original form used by Du Bois-Reymond (Fig. 345). The 
 last consists of two zinc troughs (p,p) thoroughly amalgamated inside, insulated on vulcanite, and 
 filled with a saturated solution of zinc sulphate (s, s). In each trough is placed a thick pad or 
 cushion of white blotting paper (A, i) saturated with the same fluid [deriving cushions]. [The 
 cushion consists of many layers, almost sufficient to fill the trough, and they are kept together by a 
 thread. To prevent the action of the zinc sulphate upon the tissue, each cushion is covered with a 
 thin layer of modeller's clay (/, t), moistened with 0.6 per cent, saline solution, which is a good 
 conductor [clay guard]. The clay guard prevents the action of the solution upon the tissue. 
 Connected with the electrodes are a pair of binding screws, whereby the apparatus is connected 
 with the galvanometer (Fig. 345).] 
 
 Fig. 349. 
 
 Non-polarizable electrode of Du Bois Reymond. Z, zinc ; H, movable support ; C, clay point — the 
 whole on a universal joint. 
 
 [Reflecting Galvanometer. — The form of galvanometer now used in this country for physio- 
 logical purposes is that of Sir William Thomson (Fig. 350). In Germany, Wiedemann's form is 
 more commonly used. In Thomson's instrument the astatic needles are very light, and connected 
 to each other by a piece of aluminum , and each set of needles is surrounded by a separate coil of 
 wire, the lower coil (/) winding in a direction opposite to that of the upper (»). A small, round, 
 light, slightly concave mirror is fixed to the upper set of needles. The needles are suspended by 
 a delicate silk fibril, and they can be raised or lowered as required by means of a small milled head. 
 When the milled head is raised the system of needles swings freely. The coils are protected by a 
 glass shade, and the whole stands on a vulcanite base, which is levelled by three screws (s , s). On 
 a brass rod (/>) is a feeble magnet (m), which is used to give an artificial meridian. The magnet 
 (m) can be raised or lowered by means of a milled head.] 
 
 [Lamp and Scale. — When the instrument is to be used, place it so that the coils face east and 
 west. At 3 feet distant from the front of the galvanometer, facing west, is placed the lamp and 
 scale (Fig. 351). There is a small vertical slit in front of the lamp, and the image of this slit is 
 projected on the mirror attached to the upper needles, and by it is reflected on to the paper scale 
 fixed just above the slit. The spot of light is focused at zero by means of the magnet m. The 
 needles are most sensitive when the oscillations occur slowly. The sensitiveness of the needles 
 can be regulated by means of the magnet. In every case the instrument must be quite level, and 
 for this purpose there is a small spirit level in the base of the galvanometer.] 
 
 [Shunt. — As the galvanometer is very delicate, it is convenient to have a shunt to regulate to a 
 certain extent the amount of electricity transmitted through the galvanometer. The shunt (Fig. 
 352) consists of a brass box containing coils of German silver wire, and is constructed on the same 
 principle as resistance coils or the rheocord {\ 326). On the upper surface of the box are several 
 
POLARIZATION AND SECONDARY RESISTANCE. 
 
 583 
 
 plates of brass separated from each other, like those of the rheocord, but which can be united by 
 brass plugs. The two wires coming from the electrodes are connected with the two binding screws, 
 and from the latter two wires are led to the outer two binding screws of the galvanometer. By 
 placing a plug between the brass plates attached to the two binding screws in the figure, the current 
 is short circuited. On removing both plugs the whole of the current must pass through the galva- 
 nometer. If one plug be placed between the central disk of brass and the plate marked \ (the other 
 being left out), then ^ of the current goes through the galvanometer and T 9 ^ to the electrodes. 
 If the plug be placed as shown in the figure opposite -fa, then T ^ part of the current goes to the 
 galvanometer, while •£$$ are short circuited. If the plug be placed opposite 7 J 5 , only y^jj 
 part goes through the galvanometer.] 
 
 Internal Polarization of Moist Bodies. — Nerves and muscular fibres, the juicy parts of 
 vegetables and animals, fibrin and other similar bodies possessing a porous structure rilled with 
 fluid, exhibit the phenomena of polarization when subjected to strong currents — a condition termed 
 internal polarization of moist bodies by Du Bois-Reymond. It is assumed that the solid parts in 
 
 Fig. 350. 
 
 Fig. 351. 
 
 Lamp and scale for Sir William 
 Thomson's galvanometer. 
 
 Fig. 352. 
 
 bir William Thomson's reflecting gal- 
 vanometer, w, upper, /, lower 
 coil ; j, s, levelling screws ; m, 
 magnet on a brass support, 6. 
 
 Shunt for galvanometer {Elliott 
 Brothers). 
 
 the interior of these bodies, which are better conductors, produce electrolysis of the adjoining fluid, 
 ju«-t like metals in contact with fluid. The ions produced by the decomposition of the internal 
 fluids give rise to differences of potential, and thus cause internal polarization ($ 333). 
 
 Cataphoric Action.— If the two electrodes from a galvanic battery be placed in the two com- 
 partments of a fluid, separated from each other by a porous septum, we observe that the fluid par- 
 ticles pass in the direction of the galvanic current, from the -f- to the — pole, so that after some 
 time the fluid in the one-half of the vessel increases, while it diminishes in the other. The phe- 
 nomena of direct transference was called by Du Bois-Reymond the cataphoric action of the con- 
 stant current. The introduction of dissolved substances through the skin by means of a constant 
 current depends upon this action (<g 290), and so does the so-called Porret's phenomenon in 
 living muscle (# 293, I, b\. 
 
 External Secondary Resistance. — This condition also depends on cataphoric action. If each 
 of the copper electrodes of a constant battery be placed in a vessel filled with a solution of cupric 
 sulphate, and from each of which there projects a cushion saturated with this fluid, then, on placing 
 
584 INDUCED OR FARADIC ELECTRICITY. 
 
 a piece of muscle, cartilage, vegetable tissue, or even a prismatic strip of coagulated albumin across 
 these cushions, we observe that, very soon after the circuit is closed, there is a considerable varia- 
 tion of the current. If the direction of the current be reversed, it first becomes stronger, but after- 
 ward diminishes. By constantly altering the direction of the current we cause the same changes in 
 the intensity. If a prismatic strip of coagulated albumin is used for the experiment, we observe 
 that, simultaneously with the enfeeblement of the current in the neighborhood of the -f- pole, the 
 albumin loses water and becomes more shrivelled, while at the — pole the albumin is swollen up 
 and contains more water. If the direction of the current be altered,, the phenomena are also 
 changed. The shrivelling and removal of water in the albumin at the positive pole must be the 
 cause of the resistance in the circuit, which explains the enfeeblement of the galvanic current. 
 This phenomenon is called "external secondary resistance" (Du Bois-Reymond). 
 
 329. INDUCTION— EXTRA CURRENT— UNIPOLAR INDUCTION ACTION 
 —MAGNETIC INDUCTION. — Induction of the Extra Current.— If a galvanic element 
 is closed by means of a short arc of wire, at the moment the circuit is again opened or broken a 
 slight spark is observed. If, however, the circuit is closed by means of a very long wire rolled in a 
 coil, then on breaking the circuit there is a strong spark. If the wires be connected with two elec- 
 trodes, so that a person can hold one in each hand, so that the current at the moment it is opened 
 must pass through the person's body, then there is a violent shock communicated to the hand. This 
 phenomenon is due to a current induced in the long spiral of wire, which Faraday called the extra 
 current. It is caused thus : When the circuit is closed by means of the spiral wire, the galvanic 
 current passing along it excites an electric current in the adjoining coils of the same spiral. At the 
 moment of closing or making the circuit in the spiral, the induced current is in the opposite direc- 
 tion to the galvanic current in the circuit ; hence its strength is lessened, and it causes no shock. 
 At the moment of opening, however, the induced current has the same direction as the galvanic 
 stream, and hence its action is strengthened. 
 
 Magnetization of Iron — If a rod of soft iron be placed in the cavity of a spiral of copper 
 wire, then the soft iron remains magnetic as long as a galvanic current circulates in the spiral. If 
 one end of the iron rod be directed toward the observer, the other away from him, and if, further, 
 the positive current traverses the spiral in the same direction as the hands of a clock, then the 
 end of the magnet directed toward the person is the negative pole of the magnet. The power 
 of the magnet depends upon the number of spiral windings and on the thickness of the iron bar. 
 As soon as the current is opened, the magnetism of the iron rod disappears. 
 
 Induced or Faradic Current. — If a very long, insulated wire be coiled into the form of a spiral 
 roll, which we may call the secondary spiral, and if a similar spiral, the primary spiral, be 
 placed near the former, and the ends of the wire of the primary spiral be connected with the poles 
 of a constant battery, every time the current in the primary circuit is made (closed), or broken 
 (opened), a current takes place, or, as it is said, is induced in the secondary spiral. If the primary 
 circuit be kept closed, and if the secondary spiral be brought nearer to, or removed further from, the 
 primary spiral, a current is also induced in the secondary spiral {Faraday, 7832). The current in 
 the secondary circuit is called the induced or Faradic current. When the primary circuit is closed, 
 or when the two spirals are brought nearer to each other, the current in the secondary spiral has a 
 direction opposite to that in the primary spiral, while the current produced by opening the primary 
 circuit, or by removing the spirals further apart, has the same direction as the primary. During the 
 time the primary circuit is closed, or when both spirals remain at the same distance from each other, 
 there is no current in the secondary spiral. 
 
 Difference between the Opening and Closing Shocks. — The opening [break"! and closing 
 [make] shocks in the secondary spiral are distinguished from each other in the following respects 
 (Fig. 353) : The amount of electricity is the same during the opening as during the closing shock, 
 but during the opening shock the electricity rapidly reaches its maximum of intensity and lasts 
 but a short time, while during the closing shock it gradually increases, but does not reach the 
 same high maximum, and this occurs more slowly. [In Fig. 353, P, and S are the abscissae of 
 the primary (inducing) and induced currents respectively. The vertical lines or ordinates represent 
 the intensity of the current, while the length of the abscissa indicates its duration. The curve I 
 indicates the course of the primary current, and 2, that in the secondary spiral (induced) when the 
 current is closed, while at I the primary current is suddenly opened, when it gives rise to the induced 
 current, 4, in the secondary spiral.] The cause of this difference is the following: When the pri- 
 mary circuit is closed there is developed in it the extra current, which is opposite in direction to the 
 primary current. Hence, it opposes considerable resistance to the complete development of the 
 strength of the primary current, so that the current induced in the secondary spiral mustalso develop 
 slowly. But when the primary spiral is opened, the extra current in the latter has the same direction 
 as the primary current, there is no extra resistance. The rapid and intense action of the opening 
 induction shock is of great physiological importance. 
 
 Opening Shock. — [On applying a single induction shock to a nerve or a muscle, the effect is 
 greater with the opening shock. If the secondary spiral be separated from the primary, so that the 
 induced currents are not sufficient to cause contraction of a muscle when applied to its motor 
 nerve, then, on gradually approximating the secondary to the primary spiral, the opening shock will 
 cause a contraction before the closing one does so.] 
 
HELMHOLTZ S MODIFICATION. 
 
 585 
 
 Helmholtz's Modification. — Under certain circumstances, it is desirable to equalize the opening 
 and closing shocks. This may be done by greatly weakening the extra current, which may be 
 accomplished by making the primary spiral of only a few coils of wire. v. Helmholtz accomplishes 
 the same result by introducing a secondary circuit into the primary current. By this arrangement 
 the current in the primary spiral never completely disappears, but by alternately closing and open- 
 ing this secondary circuit where the resistance is much less, it is alternately weakened and strength- 
 ened. 
 
 [In Fig. 354 a wire is introduced between a and/", while the binding scr;w, f, is separated from 
 the platinum contact, c, of Neef s hammer, but at the same time the screw, d, is raised so that 
 it touches Neef's hammer. The current passes from the battery, K, through the pillar, a, toy in 
 the direction of the arrow, through the primary spiral, P, to the coil of soft wire, g, and back to the 
 battery through h and e. But g is magnetized thereby, and when it is so it attracts c and makes it 
 touch the screw, d. Thus a secondary circuit, or short circuit, is formed through a, b. c, d, e, which 
 weakens the current passing through the electro-magnet, g, so that the elastic metallic spring flies 
 up again and the current through the primary spiral is long circuited, and thus the process is repeated. 
 In Fig. 353 the lines I and 7 indicate the course of the current in the primary circuit of closing (a), 
 and opening («). It must be remembered that in this arrangement there is always a current passing 
 through the primary spiral, P (Fig. 354). The dotted lines, 6 and 8 above and below S , represent 
 the course of the opening (a) and closing shocks (e) in the secondary spiral. Even with this arrange- 
 ment the opening is still slightly stronger than the closing shock.] The two shocks, however, may 
 
 Fig. 353. 
 
 I 
 
 $0 
 
 Fig. 353. — Scheme of the induced currents. Pi, abscissa of the primary, and S„ of the secondary current. A, begin- 
 ning, and E, end of the inducing current ; 1, curve of the primary current weakened by the extra current ; 3, 
 where the primary current is opened; 2 and 4, corresponding currents induced in the secondary spiral; P 3 , 
 height ; ;. e ., the strength of the constant inducing current ; 5 and 7, the curve of the inducing current when it 
 is opened and closed during Helmhultz's modification ; 6 and 8, the corresponding currents induced in the 
 secondary circuit. Fig. 354. — Helmholtz's modification of Neef s hammer. As long as c is not in contact 
 with d,g h remains magnetic ; thus c is attracted to d, and a secondary circuit, a, b, c, d, *?, is formed ; c then 
 springs back again, and thus the process goes on. A new wire is introduced to connect a with /I K, battery. 
 
 be completely equalized by placing a resistance coil or rheostat in the short circuit, which increases 
 the resistance, and thus increases the current through the primary spiral when the short circuit is 
 closed. 
 
 Unipolar induction. — When there is a very rapid current in the primary spiral, not only is there 
 a current induced in the secondary spiral when its free ends are closed, e. g., by being connected 
 with an animal tissue, but there is also a current when one wire is attached to a binding screw con- 
 nected with one end of the wire of the secondary spiral (p. 572). A muscle of a frog's leg, when 
 connected with this wire, contracts, and this is called a unipolar induced contraction. It usually 
 occurs when the primary circuit is opened. The occurrence of these contractions is favored when 
 the other end of the spiral is placed in connection with the ground, and when the frog's muscle 
 preparation is not completely insulated. 
 
 Magneto Induction. — If a magnet be brought near to, or thrust into the interior of, a coil or 
 wire, it excites a current, and also when a piece of soft iron is suddenly rendered magnetic or sud- 
 denly demagnetized. The direction of the current so induced in the spiral is exactly the same as 
 that with Faradic electricity, i. e., the occurrence of the magnetism on approximating the spiral to 
 a magnet, excites an induced current in a direction opposite to that supposed to circulate in the 
 magnet. Conversely, the demagnetization, or the removal of the spiral from the magnet, causes a 
 cu rent in the same direction. 
 
 Acoustic Tetanus. — If a magnet be rapidly moved to and fro near a spiral, which can easily 
 be done by fixing a vibrating magnetic rod at one end and allowing the other end to swing freely 
 
586 
 
 DU BOIS-REYMOND S INDUCTORIUM. 
 
 near the spiral, then the pitch of the note of the vibrating rod gives us the rapidity of the induction 
 shocks. If a frog's nerve-muscle preparation be stimulated we get what Grossmann called " acoustic 
 tetanus." 
 
 330. DU BOIS-REYMOND'S INDUCTORIUM— MAGNETO-INDUCTION AP- 
 PARATUS. — Inductorium of Du Bois-Reymond. — The induction apparatus of Du Bois- 
 Reymond, which is used for physiological purposes, is a modification of the magneto-electro-motor 
 apparatus of Wagner and Neef. A scheme of the apparatus is given in Fig. 355. D represents 
 the constant element, i. e., the galvanic battery. The wire from the positive pole, a, passes to a 
 metallic column, S, which has a horizontal vibrating spring, F, attached to its upper end. To the 
 outer end of the spring a square piece of iron, e, is attached. The middle point of the upper sur- 
 face of the spring [covered with a little piece of platinum] is in contact with a movable $crew, b. 
 A moderately thick copper wire, c, passes from the screw, b, to the primary spiral or coil, x, x, 
 which contains in its interior a number of pieces of soft iron wire, i, i, covered with an insulating 
 varnish. The copper wire which surrounds the primary spiral is covered with silk. The wire, d, 
 is continued from the primary spiral to a horseshoe piece of soft iron, H, around which it is coiled 
 spirally, and from thence it proceeds, at/", back to the negative pole of the battery, £■. When the 
 current in this circuit — called the primary circuit — is closed, the following effects are produced : 
 The horseshoe, H, becomes magnetic, in consequence of which it attracts the movable spring or 
 
 I, Scheme of Du Bois-Rtymond's sledge-induction machine. D, constant element; a, wire from + pole, (^) — 
 pole; S, brass upright ; F, elastic spring ; 6, binding screw; c, wire round primary spiral {x-,jr), containing {/, :") 
 soft iron wire ; K, K, secondary spiral, with board (p, p) on which it can be moved ; H, soft iron magnetized by 
 curr-nt {d,f) passing round it. II, key for secondary circuit, as shown it is short circuited. Ill, electrodes (r, r), 
 with a key (K) for breaking the circuit. 
 
 Neef s hammer, e, whereby the contact of the spring, F, with the screw, b, is broken. Thus the 
 current is broken, the horseshoe is demagnetized, the spring, e, is liberated, and, being elastic, it 
 springs upward again to its original position in contact with b, and thus the current is re-established. 
 The new contact causes H to be magnetized, so that it must alternately rapidly attract and liberate 
 the spring, e, whereby the primary current is rapidly made and broken between Fand b. 
 
 A secondary spiral or coil (K, K) is placed in the same direction as the primary (x, x), but 
 having no connection with it. It moves in grooves upon a longpiece of wood (f,p). The secondary 
 spiral consists of a hollow cylinder of wood covered with numerous coils of thin silk-covered wire. 
 The secondary spiral moving in slots, can be approximated to or even pushed entirely over the 
 primary spiral, or can be removed from it to any distance desired. 
 
 [Fig. 356. shows the actual arrangement of Du Bois-Reymond's inductorium. The primary 
 coil (R') consists of about 150 coils of thick insulated copper wire, the wire being thick, to offer 
 slight resistance to the galvanic current. The secondary coil (R") consists of 6000 turns of thin 
 insulated copper wire arranged on a wooden bobbin ; the whole spiral can be moved along the 
 board (B), to which a millimetre scale (I) is attached, so that the distance of the secondary from the 
 primary spiral may be ascertained. At the left end of the apparatus is Wagner's hammer as 
 adapted by Neef. which is just an automatic arrangement for opening and breaking the primary 
 circuit. When Neef s hammer is used, the wires from the battery are connected as in the figure, 
 
MAGNETO INDUCTION. 
 
 587 
 
 but when single shocks are required, the wires from the battery are connected with a key, and this 
 again with the two terminals of the primary spiral S" and S'".] 
 
 According to the law of induction (§329), when the primary circuit is closed, a current is induced 
 in the secondary circuit in a direction the reverse of that in the primary, while, when it is opened, 
 
 .' &" 
 
 Fig. 356. 
 
 Induction apparatus of Du Bois-Reymond. R', primary, R". secondary spiral ; B, board on which R" moves ; I, 
 
 scale ; H .wires from battery ; P', P", pillars ; H, Neef's hammer ; B', electro-magnet : S', binding screw 
 
 touching the steel spring (H) ; S" and S'", binding screws to which to attach wires when Neef's hammer is not 
 required {Elliott Brothers). 
 
 the induced current has the same direction. Further, according to the laws of magneto induction, 
 there is the magnetization of the iron rods (», i) within the primary spiral (x, x), that causes a 
 reverse current in the secondary spiral (K, K), while the demagnetization of the iron rods on opening 
 
 Fig. 357. 
 
 Fig. 358. 
 
 Magneto induction apparatus, with Stohrer's commutator. 
 
 Du Boif-Reymond's friction key. 
 
 the primary circuit causes an induced current in the same direction. Thus we explain the much 
 more powerful action of the opening shock as compared with the closing shock. [The direction of 
 the inducing current remains the same, while the induced currents are constantly reversed.] 
 
588 ELECTRICAL CURRENTS IN MUSCLE AND NERVE. 
 
 The magneto-induction (R) apparatus of Pixii (1832), improved by Saxton, and still further 
 improved by Stohrer, consists of a very powerful horseshoe steel magnet (Fig. 357). Opposite 
 its two poles (N and S) is a horseshoe-shaped piece of iron (H), which rotates on a horizontal 
 axis (a, b). On the ends of the horseshoe are fixed wooden bobbins (c, d), with an insulated wire 
 coiled round them. When the horseshoe is at rest, as in the figure, it becomes magnetized by the 
 steel magnet, while in the wires of both bobbins (c and d) an electric current is developed every 
 time the horseshoe is demagnetized and again magnetized. When the bobbins rotate in front of 
 the magnet, as each coil approaches one pole a current is induced, and similarly when it is carried 
 past the pole of the magnet, so that four currents are induced in each coil by a single rotation. By 
 means of Slohrer's commutator (m, n) attached to the spindle (a, b), and the divided metal plates 
 ( y, z) which pass to the electrodes, the two currents induced in the bobbins are obtained in the same 
 direction. 
 
 Keys, or arrangements for opening or breaking a circuit, are of great use. Fig. 355, II, shows 
 a scheme of a friction key of Du Bois-Reymond, introduced into the secondary circuit. It con- 
 sists of two brass bars (z and y) fixed to a plate of ebonite, and as long as the key is down on the 
 metal bridge (y, /-, z) it is "short circuited," i. c, the conduction is so good through the thick brass 
 bars, that none of the current goes through the wires leading from the left of the key. When the 
 bridge (r) is lifted the current is opened. [The term accessory circuit is also used for short circuit 
 [Fig. 358 shows the actual form of the key, v being a screw wherewith to clamp it to the table. 
 Similarly, the key electrodes (III) may be used, the current being made as soon as the spring con 
 necting plate (?) is raised by pressing upon k. This instrument is opened by the hand ; a, b are the 
 wires from the battery or induction machine ; r, r, those going to the tissue; G, the handle of the 
 instrument. 
 
 . [Plug Key. — Other forms of keys are in use, e.g., Fig. 359, the plug key, the two brass plates to 
 which the wires are attached being fixed on a plate of ebonite. The brass plug is used to connect 
 
 Fig. 360. 
 
 Fig. 359. 
 
 Fig- 359-' — Plug k e V- Fig. 360. — Capillary conlact. e, vibrating platinum style adjustable by f and g, and dipping 
 into mercury at a ; 6, bent tube filled with mercury, into which dips a wire id) ; a, opening in cross tube (cj. 
 
 the two brass plates. All these are dry contacts, but sometimes a fluid contact is used, as in the 
 mercury key, which merely consists of a block of wood, with a cup of mercury in its centre. The 
 ends of the wires from the battery dip into the mercury ; when both wires dip into the mercury, the 
 circuit is made, and when one is out it is broken.] 
 
 [Capillary Contact Key. — When an ordinary mercury key is used to open and close the primary 
 circuit, the layer of oxide formed on the surface by the opening spark disturbs the conduction after 
 a short time ; hence, it is advisable to wash the surface of the mercury with a dilute solution of 
 alcohol and water ( IV. Stirling). A handy form of " capillary contact " is shown in Fig. 360, such 
 as was used by Kronecker and Stirling in their experiments on the heart. " A glass T tube is pro- 
 vided at the crossing point with a small opening (a). The vertical tube (*) is bent in the form of a U, 
 and filled so full with mercury that the convex surface of the latter projects within the lumen of the 
 transverse tube (c). One end of c is connected with a Mariotte's flask containing diluted alcohol, 
 and the supply of the latter can be regulated by means of a stop-cock. The fluid flows over the 
 apex of the mercury and keeps it clean. The vibrating platinum style (e) is attached to the end of 
 a rod, which, in turn, is connected with the positive pole of the battery, while the platinum wire (d) 
 is connected with the negative pole of the battery."] 
 
 331. ELECTRICAL CURRENTS IN PASSIVE MUSCLE AND NERVE- 
 SKIN CURRENTS. — Methods. — In order to investigate the laws of the muscle current, we 
 must use a muscle composed of parallel fibres, and with a simple arrangement of its fibres in the 
 form of a prism or cylinder (Fig. 361, I and II). The sartorius muscle of the frog supplies the>e 
 conditions. In such a muscle we distinguish the surface or the natural longitudinal section, 
 its tendinous ends or the natural transverse section; further, when the latter is divided trans- 
 versely t> the long axis, the artificial transverse section (Fig. 361, I, c, d); lastly, the term 
 equator (a, b-m, n) is applied to a line so drawn as exactly to divide the length of the muscle into 
 
ELECTRICAL CURRENTS IN MUSCLE AND NERVE. 
 
 589 
 
 halves. As the currents are very feeble, it is necessary to use a galvanometer with a periodic damped 
 magnet (Figs. 345, I, and 350), or a tangent mirror boussole similar to that used for thermo-electric 
 purposes (Fig. 216). The wires leading from the tissue are connected with non-polarizable elec- 
 trodes (Fig. 345, P, P). 
 
 The capillary electrometer of Lippmann may be used for detecting the current (Fig. 362). A 
 thread of mercury enclosed in a capillary tube and touching a conducting fluid, e.g., dilute sulphuric 
 acid, is displaced by the constant current in consequence of the polarization taking place at the point 
 of contact altering the constancy of the capillarity of the mercury. The displacement of the mer- 
 cury which the observer (B) detects by the aid of the microscope (M) is in the direction of the 
 positive current. In Fig. 362, R is a capillary glass tube, filled from above with mercury, and from 
 below with dilute sulphuric acid. Its lower narrow end opens into a wide glass tube, provided 
 below with a platinum wire fused into it and filled with Hg (q), and this again is covered with 
 dilute sulphuric acid (s). The wires are connected with non-polarizable electrodes applied to the 
 -j- and — surfaces of the muscle. On closing the circuit, the thread of mercury passes downward 
 from c in the direction of the arrow. [A very simple and convenient modification of this instru- 
 ment for studying the muscle current has recently been invented by M'Kendrick.] 
 
 Compensation. — The strength of the current in animal tissues is best measured by the com- 
 
 Fig. 361. 
 
 Fig. 362. 
 
 
 t 
 
 n 
 
 
 .} 
 
 / p 
 
 k 
 
 I 
 
 ,'l 
 
 j'e 
 
 
 
 jp^2 
 
 
 III. 
 
 Scheme of the muscle current. 
 
 Capillary electrometer (after Christiani). R, 
 mercury in tube ; c. capillary tube ; s, sul- 
 phuric acid; q, Hg ; B, observer; M., 
 microscope. 
 
 pensation method of Poggendorf and Du Bois-Reymond. A current of known strength, or which 
 can be accurately graduated, is passed in an opposite direction through the same galvanometer or 
 boussole, until the current from the animal tissue is just neutralized or compensated. [When this 
 occurs, the needle deflected by the tissue current returns to zero. The principle is exactly the same 
 as that of weighing a body in terms of some standard weights placed in the opposite scale pan of 
 the balance.] 
 
 i. Perfectly fresh, uninjured muscles yield no current, and the same is 
 true of dead muscle (L. Hermann, 1867). 
 
 2. Strong electrical currents are observed when the transverse section of a 
 muscle is placed on one of the cushions of the non-polarizable electrodes (Fig. 
 345, I, M), while the surface is in connection with the other (Nobili, Matteucci, 
 . Du Bois-Reymond}. The direction of the current is from the (positive) longi- 
 tudinal section to the (negative) transverse section in the conducting wires {i. e., 
 within the muscle itself from the transverse to the longitudinal section (Figs. 345, 
 
590 ELECTRICAL CURRENTS IN MUSCLE AND NERVE. 
 
 I, and 361,) I). This current is stronger the nearer one electrode is to the 
 equator, and the other to the centre of the transverse section ; while the strength 
 diminishes the nearer the one electrode is to the end of the surface, and the other 
 to the margin of the transverse section. 
 
 Smooth muscles also yield similar currents between their transverse and longitudinal surfaces 
 (« 334, II). 
 
 3. Weak electrical currents are obtained when — (a) two points at unequal dis- 
 tances from the equator are connected ; the current then passes from the point 
 nearer the equator (-f ) to the point lying further from it ( — ), but of course this 
 direction is reversed within the muscle itself (Fig. 361, II, ke and le). {b) Simi- 
 larly weak currents are obtained by connecting points of the transverse section at 
 unequal distances from the centre, in which case the current outside the muscle 
 passes from the point lying nearer the edge of the muscle to that nearer the centre 
 of the transverse section (Fig. 361, II, i, c). 
 
 4. When two points on the surface are equidistant from the equator (Fig. 361, 
 I, x, y, v, z, — II, r, e), or two equidistant trom the centre of the transverse sec- 
 tion (II, c) are connected, no current is obtained. 
 
 5. If the transverse section of a muscle be oblique (Fig. 361, III), so that the 
 muscle forms a rhomb, the conditions obtaining under III are disturbed. The 
 point lying nearer to the obtuse angle of the transverse section or surface is posi- 
 tive to the one lying near to the acute angle. The equator is oblique (a, c). These 
 currents are called " deviation currents'''' by Du Bois-Reymond, and their course 
 is indicated by the lines 1, 2, and 3. 
 
 Strength of Electro-motive Force. — The electro-motive force of a strong muscle current 
 (frog) is equal to 0.05 to 0.08 of a Daniell's element ; while the strongest deviation current may be 
 o. I Daniell. The muscles of a curarized animal at first yield stronger currents ; fatigue ol the 
 muscle diminishes the strength of the current (Roeber), while it is completely abolished when the 
 muscle dies. Heating a muscle increases the current ; but above 40 C. it is diminished (Steiner). 
 Cooling diminishes the electro-motive force. The warmed living muscular and nervous substance 
 (Hermann, Worm Miiller, Griitzner) is positive to the cooler portions ; while, if the dead ti.-sues 
 be heated, they behave practically as indifferent bodies as regards the tissues that are not heated. 
 
 6. The passive nerve behaves like muscle, as far as 2, 3, and 4 are concerned. 
 
 The electro-motive force of the strongest nerve current, according to Du Bois-Reymond, is 0.02 
 of a Daniell. Heating a nerve to i5°-25° C. increases the nerve current, while high temperatures 
 diminish it (Steiner). 
 
 7. If the two transversely divided ends of an excised nerve, or two points on 
 the surface equidistant from the equator be tested, a current — the axial current 
 — flows in the nerve fibre in the opposite direction to the direction of the normal 
 impulse in the nerve ; so that in centrifugal nerves it flows in a centripetal direc- 
 tion, and in centripetal nerves in a centrifugal direction {Mendelsohn and Chris- 
 tiani). 
 
 Rheoscopic Limb. — The existence of a muscle current may be proved with- 
 out the aid of a galvanometer : 1. By means of a sensitive nerve-muscle prepara- 
 tion of a frog, or the so-called " physiological rheoscope" Place a moist conductor 
 on the transverse and longitudinal surface of the gastrocnemius of a frog. On 
 placing the sciatic nerve of a nerve-muscle preparation of a frog on this conductor, 
 so as to bridge over or connect these two surfaces, contraction of the muscle con- 
 nected with the nerve occurs at once ; and the same occurs when the nerve is 
 removed. 
 
 [Use a nerve-muscle preparation, or, as it is called, a physiological limb. Hold the preparation 
 by the femur, and allow its own nerve to fall upon the gastrocnemius, and the muscle will contract, 
 but it is better to allow the nerve to fall suddenly upon the cross section of the muscle. The nerve 
 then completes the circuit between the longitudinal and transverse section of the muscle, so that it 
 is stimulated by the current from the latter, the nerve is stimulated, and through it the muscle. 
 That it is so, is proved by tying a thread round the nerve near the muscle, when the latter no longer 
 contracts.] 
 
ELECTRICAL CURRENTS OF ACTIVE MUSCLE. 591 
 
 Contraction without Metals. — Make a transverse section of a gastrocnemius 
 muscle of a frog's nerve-muscle preparation, and allow the sciatic nerve to fall 
 upon this transverse section, when the limb contracts, as the muscle current from 
 the longitudinal to the transverse surface now traverses the nerve {Galvani, Al. v. 
 Humboldt). 
 
 2. Self-stimulation of the Muscle.— We may use the muscle current of an 
 isolated muscle to stimulate the latter directly and cause it to contract. If the 
 transverse and longitudinal surfaces of a curarized frog's nerve-muscle preparation 
 be placed on non-polarizable electrodes, and the circuit be closed by dipping the 
 wires coming from the electrodes in mercury, then the muscle contracts. Simi- 
 larly a nerve may be stimulated with its own current {Du Bois-Reymond and 
 others). If the lower end of a muscle with its transverse section be dipped into 
 normal saline solution (0.6 percent. NaCl), which is quite an indifferent fluid, 
 this fluid forms an accessory circuit between the transverse and adjoining longi- 
 tudinal surface of the muscle, so that the muscle contracts. Other indifferent 
 fluids used in the same way produce a similar result. 
 
 3. Electrolysis. — If the muscle current be conducted through starch mixed 
 with potassic iodide, then the iodide is deposited at the -f- pole, where it makes 
 the starch blue. 
 
 Frog Current. — It is asserted that the total current in the body is the sum of the electrical cur- 
 rents of the several muscles and nerves which, in a frog deprived of its skin, passes from the tip of 
 the toes toward the trunk, and in the trunk from the anus to the head. This is the " corrente pro- 
 pria delta rena" of Leopoldo Nobili (1827), or the "frog current" of Du Bois-Reymond. In 
 mammals the corresponding current passes in the opposite direction. 
 
 After death the currents disappear sooner than the excitability ( Valentin) ; they remain longer 
 in the muscle than the nerves, and in the latter they disappear sooner in the central portions. If 
 the nerve current after a time becomes feeble, it may be strengthened by making a new transverse 
 section of the nerve. A motor nerve completely paralyzed by curara gives a current (Funke), and 
 so does a nerve beginning to undergo degeneration, even two weeks after it has lost its excitability. 
 Muscles in a state of rigor mortis give currents in the opposite direction, owing to inequalities in 
 the decomposition which takes place. The nerve current is reversed by the action of boiling water 
 or drying. 
 
 Currents from Skin and Mucous Membranes. — In the skin of the frog 
 the outer surface is -f- , the inner is — , {Du Bois-Reymond, Budge), and the same 
 is true of the mucous membrane of the intestinal tract {Rosenthal), the cornea 
 {Grunhagen), as well as the non-glandular skin of fishes {Hermann) and molluscs 
 {Oehler). 
 
 Stimulation of the Secretory Nerves of the glandular membranes, besides causing secretion, 
 affects the current of rest {Koeber). This secretion current passes in the same direction in the 
 skin of the frog and warm-blooded animals as the current of rest, although in the frog it is occa- 
 sionally in the opposite direction (Hermann). If the current be conducted uniformly from both 
 the hind feet of a cat, on stimulating the sciatic nerve of one side, not only is there a secretion of 
 sweat (jj 288), but a secretion current is developed (Luchsinger and Hermann). If two symmet- 
 rical parts of the skin in the leg or arm of a man be similarly tested, and the muscle of one side 
 be contracted, a similar current is developed. Destruction or atrophy of the glands abolishes both 
 the power of secretion and the secretion current. There is no secretion current from skin covered 
 with hairs, but devoid of glands (Bubnoff). [The secretion current from the submaxillary gland 
 is referred to in \ 145 (Bayliss and Bradford 'J.] 
 
 332. CURRENTS OF STIMULATED MUSCLE AND NERVE. 
 — 1. Negative Variation of the Muscle Current. — If a muscle, which 
 yields a strong electrical current, be thrown into a state of tetanic contraction by 
 stimulating its motor nerve, then, when the muscle contracts, there is a diminu- 
 tion of the muscle current, and occasionally the needle of the galvanometer may 
 swing almost to zero. This is the negative variation of the muscle current {Du 
 Bois-Reymond). It is larger the greater the primary deflection of the galva- 
 nometer needle and the more energetic the contraction. 
 
 After tetanus the muscle current is weaker than it was before. If the muscle was so placed upon 
 the electrodes that the current was "feeble," equally during tetanus, there is a diminution of this 
 
592 SECONDARY CONTRACTION. 
 
 current. In the inactive arrangement, the contraction of the muscle has no eftect on the needle. 
 If the muscle be prevented from shortening, as by keeping it tense, the negative variation still 
 takes place. 
 
 2. Current during Tetanus. — An excised frog's muscle tetanized through its 
 nerve shows electro-motor force — the so-called " action current." In a tetan- 
 ized frog's gastrocnemius there is a descending current. In completely uninjured 
 human muscles, however, thrown into tetanus by acting on their nerves, there is 
 no such current (Z. Hermann) ; similarly, in quite uninjured frog's muscles, as 
 well as when these muscles are directly and completely tetanized, there is no cur- 
 rent. 
 
 3. Current during the Contraction Wave. — If one end of a muscle be 
 directly excited with a momentary stimulus, so that the contraction wave (§ 299) 
 rapidly passes along the whole length of the muscular fibres, then each part of 
 the muscle, successively and immediately before it contracts, shows the negative 
 variation. Thus the " contraction wave" is preceded by a " negative wave " of 
 the muscle current, the latter occurring during the latent period. Both waves have 
 the same velocity, about 3 metres per second. The negative wave, which first 
 increases and then diminishes, lasts at each point only 0.003 second {Bernstein). 
 
 4. During a Single Contraction. — A single contraction also shows a muscle 
 
 Secondary contraction. The sciatic nerve of A lies on B ; Nerve-muscle preparation of a frog. F, femur ; 
 
 E, electrodes applied to the sciatic nerve of B. S, Sciatic nerve ; I , tendo Achilles. 
 
 current. The best object to use for this purpose is a contracting heart, which is 
 placed upon the non-polarizable electrodes connected with a sensitive galva- 
 nometer. Each beat of the heart causes a deflection of the needle, which occurs 
 before the contraction of the cardiac muscle (Kolliker and H. Miiller). The 
 electrical disturbance in the muscle causing the negative variation always precedes 
 the actual contraction (v. Helmholtz, 1854). When the completely uninjured 
 frog's gastrocnemius contracts by stimulating the nerve, there is at first a descend- 
 ing and then an ascending current (Sig. Meyer, § 344, II). 
 
 Secondary Contraction. — A nerve-muscle preparation may be used to 
 demonstrate the electrical changes that occur during a single contraction. If the 
 sciatic nerve, A, of such a preparation be placed upon another muscle, B, as in 
 Fig. 363, then every time the latter, B, contracts, the frog's muscle, A, connected 
 with the nerve also contracts. 
 
 If the nerve of a frog's nerve-muscle preparation be placed on a contracting 
 mammalian heart, then a contraction of the muscle occurs with every beat of the 
 heart (Matteucci, 1842). The diaphragm, even after section of the phrenic nerve, 
 especially the left, also contracts during the heart beat (Schiff). This is the 
 " secondary contraction " of Galvani. 
 
NEGATIVE VARIATION OF THE NERVE CURRENT. 
 
 593 
 
 Secondary Tetanus. — Similarly, if a nerve of a nerve-muscle preparation be 
 placed on a muscle which is tetanized, then the former also contracts, showing 
 "secondary tetanus" (Z>« Bois-Reymond). The latter experiment is regarded 
 as a proof that, during the process of negative variation in the muscle, many 
 successive variations of the current must take place, as only rapid variations of 
 this kind can produce tetanus by acting on a nerve — continuous variations being 
 unable to do so. 
 
 Usually there is no secondary tetanus in a frog's nerve muscle preparation when it is laid upon a 
 muscle which is tetanized voluntarily, or by chemical stimuli, or by poisoning with strychnin (Her- 
 ing and Friedreich, JCiihne) ; still, Loven has observed secondary strychnin tetanus composed of 
 six to nine shocks per second. Observations with a sensitive galvanometer, or Lippmann's capil- 
 lary electrometer (Fig. 362), show that the spasms of strychnin poisoning, as well as a voluntary 
 contraction, are discontinuous processes (Lovin, p. 521). 
 
 [Nerve-muscle Preparation. — This term has been used on several occasions. 
 It is simply the sciatic nerve with the gastrocnemius of the frog attached to it 
 
 Fig. 365. 
 
 Scheme of Bernstein's differential rheotome; N «, nerve; J, induction machine; G, galvanometer; x,y, deflection 
 of needle ; E, battery and primary circuit with C for opening it at o ; c, for closing galvanometer circuit ; x, z T 
 electrodes in galvanometer circuit ; S, motor. 
 
 (Fig. 364). The sciatic nerve is dissected out entire from the vertebral column 
 to the knee ; the muscles of the thigh separated from the femur, and the latter 
 divided about its middle, so that the preparation can be fixed in a clamp by the- 
 remaining portion of the femur ; while the tendon of the gastrocnemius is divided 
 near to the foot. If a straw flag is to be attached to the foot, do not divide the 
 tendo Achilles.] 
 
 5. Negative Variation in Nerve. — If a nerve be placed with its transverse 
 section on one non-polarizable electrode, and its longitudinal surface on the other, 
 and if it be stimulated electrically, chemically or mechanically, the nerve current 
 is also diminished (Du Bois-Reymond). This negative variation can be prop- 
 agated toward both ends of a nerve, and is composed of very rapid, successive,, 
 periodic interruptions of the original current, just as in a contracted muscle {Bern- 
 stein) ; while Hering succeeded in obtaining from a nerve, as from a muscle, a 
 secondary contraction or secondary tetanus. The amount of the negative varia- 
 tion depends upon the extent of the primary deflection, also upon the degree of 
 38 
 
594 ELECTRICAL CURRENTS DURING ELECTROTONUS: 
 
 nervous excitability, and on the strength of the stimulus employed. The negative 
 variation occurs on stimulating with tetanic as well as with single shocks. The 
 negative variation is not observed in completely uninjured nerves. 
 
 Hering found that the negative variation of the nerve current caused by tetanic stimulation is 
 followed by a positive variation, which occurs immediately after the former. It increases to a 
 certain degree with the duration of the stimulation, as well as with the strength of the stimulus 
 (Effect of Electrotonus, \ 335, I). 
 
 Negative Variation of the Spinal Cord. — This is the same as in nerves generally. If a cur- 
 rent be conducted from the transverse and longitudinal surfaces of the upper part of the medulla 
 oblongata, we observe spontaneous intermittent negative variations, perhaps due to the intermittent 
 excitement of the nerve centres, more especially of the respiratory centre. Similar variations are 
 obtained reflexly by single stimuli applied to the sciatic nerve, while strong stimulation by common 
 salt or induction shocks inhibits them. 
 
 Velocity. — The process of negative variation is propagated at a measureable velocity along the 
 nerve, most rapidly at 15° to 25° C. (Steiner), and at the same rate as the velocity of the nervous 
 impulse itself, about 27 to 28 metres per second. The duration of a single variation (of which the 
 process of negative variation is composed) is only 0.0005 t0 0.0008 second, while the wave length 
 in the nerve is calculated by Bernstein at 18 mm. 
 
 Differential Rheotome. — J. Bernstein estimated the velocity of the negative variation in a 
 nerve by means of a differential rheotome (Fig. 365) thus: A long stretch of a nerve (Nn) is so 
 arranged that at one end of it (N) its transverse and longitudinal surfaces are connected with a 
 galvanometer (Gj, while at the other end (») are placed the electrodes of an induction machine 
 (J). A disk (B), rapidly rotating on its vertical axis (A), has an arrangement (C) at one point of 
 its circumference, by means of which the current of the primary circuit (E) is rapidly opened and 
 closed during each revolution. This causes, with each rotation of the disk, an opening and a 
 closing shock to be applied to the end of the nerve. At the diametrically opposite part of the cir- 
 cumference is an arrangement (c) by which the galvanometer circuit is closed and opened during 
 each revolution. Thus, the stimulation and the closing of the galvanometer circuit occur at the 
 same moment. On rapidly rotating the disk, the galvanometer indicates a strong nerve current, 
 an excursion of the magnetic needle to y. At the moment of stimulation the negative variation 
 has not yet reached the other end of the nerve. If, however, the arrangement which closes the 
 galvanometer circuit be so displaced (to 0) along the circumference that the galvanometer circuit is 
 closed somewhat later than the nerve is stimulated, then the current is weakened by the negative 
 variation (the needle passing backward to x). When we know the velocity of rotation of the disk, 
 it is easy to calculate the rate at which the impulse causing the negative variation passes along a 
 given distance of nerve from N to n. 
 
 The negative variation is absent in degenerated nerves as soon as they lose their excitability. 
 
 Eye Currents. — If a freshly-excised eyeball be placed on the non-polarizable electrodes con- 
 nected with a galvanometer, and if light fall upon the eye, then the normal eye current from the 
 cornea ( -(- ) to the transverse section of the optic nerve ( — ) is at first increased. Yellow light is 
 most powerful, and less so the other colors (Holmgren, M' Kendrick and Dewar). The inner surface 
 of the passive retina is positive to the posterior. When the retina is illuminated there is a double 
 variation, a negative variation with a preliminary positive increase ; while, when the light ceases, 
 there is a simple positive variation. Retinas in which the visual purple has disappeared, owing to 
 the action of light, show no variations (Kiihne and Steiner). 
 
 333. ELECTROTONIC CURRENTS IN NERVE AND MUS- 
 CLE. — 1. Positive Phase of Electrotonus. — If a nerve be so arranged upon 
 the electrodes (Fig. 366, I) that its transverse section lies on one, and its longi- 
 tudinal on the other, electrode, then the galvanometer indicates a strong current. 
 If now a constant current be transmitted through the end of the nerve pro- 
 jecting beyond the electrodes (the so-called "polarizing" end of the nerve), and 
 if the direction of this current coincides with that in the nerve, then the magnetic 
 needle gives a greater deflection, indicating an increase of the nerve current — "the 
 positive phase of electrotonus." The increase is greater the longer the stretch 
 of nerve traversed by the current, the stronger the galvanic current, and the less 
 the distance between the part of the nerve traversed by the constant current and 
 that on the electrodes. 
 
 2. Negative Phase of Electrotonus. — If in the same length of nerve the 
 constant current passes in the opposite direction to the nerve current (Fig. 
 366, II), there is a diminution of the electro-motive force of the latter — 
 "negative phase of electrotonus." 
 
THEORIES OF MUSCLE AND NERVE CURRENTS. 
 
 595 
 
 Nerve current in electrotonus. a. 
 vanometer ; 6, electrodes ; E, 
 stant current. 
 
 gal- 
 con- 
 
 3. Equator. — If two points of the nerve equi- Fig. 366. 
 
 distant from the equator be placed on the electrodes 
 (III), there is no deflection of the galvanometer 
 needle (p. 590, 4). If a constant current be 
 passed through one free projecting end of the 
 nerve, then the galvanometer indicates an electro- 
 motive effect in the same direction as the constant 
 current. 
 
 Electrotonus. — These experiments show that 
 a constant current causes a change of the electro- 
 motive force of the part of the nerve directly- 
 traversed by the constant current, and also in the 
 part of the nerve outside the electrodes. This 
 condition is called electrotonus (Du Bois-Reymond, 
 1843)- 
 
 The electrotonic current is strongest not far from the elec- 
 trodes, and it may be twenty-five times as strong as the nerve 
 current of rest ($ 331, 5) ; it is greater on the anode than on 
 the cathode side ; it undergoes a negative variation like the 
 resting nerve current during tetanus; it occurs at once on 
 closing the constant current, although it diminishes uninter- 
 ruptedly at the cathode (Du Bois-Reymond). These phe- 
 nomena take place only as long as the nerve is excitable. 
 
 If the nerve be ligatured in the projecting part in the galvanometer circuit, the phenomena cease 
 in the ligatured part. The negative variation (§ 332) occurs more rapidly than the electrotonic 
 increase of the current, so that the former is over before the electro-motive increase occurs. The 
 velocity of the electrotonic change in the current is less than the rapidity of propagation of the 
 excitement in the nerves — being only 8 to 10 metres per second ( Tschirjew, Bernstein). 
 
 " The secondary contraction from a nerve " depends upon the electrotonic state. If the 
 sciatic nerve of a frog's nerve-muscle preparation be placed on an excised nerve, and if a constant 
 current be passed through the free end of the latter — non-electrical stimuli being inactive — the 
 muscles contract. This occurs because the electrotonizing current in the excised nerve stimulates 
 the nerve lying on it. By rapidly closing and opening the current, we obtain " secondary tetanus 
 from a nerve" (p. 593). 
 
 Paradoxical Contraction. — Exactly the same occurs when the current is applied to one of the 
 two branches into which the sciatic nerve (cut through above) of the frog divides, i.e., the muscles 
 attached to both branches of the nerve contract. 
 
 Polarizing After-Currents. — When the constant current is opened, there are after-currents 
 depending upon internal polarization (§ 328). In living nerves, muscle and electrical organs this 
 internal polarization current, when a strong primary current of very short duration is used, is always 
 positive, i.e., has the same direction as the primary current. Prolonged duration of the primary 
 current ultimately causes negative polarization. Between these two is a stage when there is no 
 polarization. Positive polarization is especially strong in nerves when the primary current has the 
 direction of the impulse in the nerve ; in muscle, when the primary current is directed from the 
 point of entrance of the nerve into the muscle toward the end of the muscle ((S 334, II). 
 
 4. Muscle Current during Electrotonus. — The constant current also pro- 
 duces an electrotonic condition in muscle ; a constant current in the same 
 direction increases the muscle current, white one in an opposite direction weakens 
 it, but the action is relatively feeble. 
 
 334. THEORIES OF MUSCLE AND NERVE CURRENTS, 
 I. Molecular Theory. — To explain the currents in muscle and nerve, Du Bois- 
 Reymond proposes the so-called molecular theory. According to this theory, a 
 nerve or muscle fibre is composed of a series of small electro-motive molecules 
 arranged one behind the other, and surrounded by a conducting indifferent fluid. 
 The molecules are supposed to have a positive equatorial zone directed toward the 
 surface, and two negative polar surfaces directed toward the transverse section. 
 Every fresh transverse section exposes new negative surfaces, and every artificial 
 longitudinal section new positive areas. 
 
 This scheme explains the strong currents — when the -j- longitudinal surface is connected with 
 
596 Hermann's difference theory. 
 
 the — transverse surface, a current is obtained from the former to the latter — but it does not explain 
 Has feeble currents. To explain their occurrence, we must assume that, on the one hand, the electro- 
 motive force of the molecules is weakened with varying rapidity at unequal distances from the 
 equator; on the other, at unequal distances from the transverse section. Then, of course, differences 
 of electrical tension obtain between the stronger and the feebler molecules. 
 
 Parelectronomy. — But the natural transverse section of a muscle, i.e., the end of the tendon, is 
 not negative, but more or less positive electrically. To explain this condition, Du Bois-Reymond 
 assumes that on the end of the tendon there is a layer of electro- positive muscle substance. He 
 supposes that each of the peripolar elements of muscle consists of two bipolar elements, and that a 
 layer of this half element lies at the end of the tendon, so that its positive side is turned toward 
 the free surface of the tendon. This layer he calls the " parelectronomic layer." It is never com- 
 pletely absent. Sometimes it is so marked as to make the end of the tendon -f- in relation to the 
 surface. Cauterization destroys it.- 
 
 The negative variation is explained by supposing that, during the action of a muscle and nerve, 
 the electro-motive force of all the molecules is diminished. During partial contraction of a muscle 
 the contracted part assumes more the characters of an indifferent conductor, which now becomes 
 connected with the negative zone of the passive contents of the muscular fibres. 
 
 The electrotonic currents beyond the electrodes in nerves must be explained. To explain the 
 electrotonic condition it is assumed that the bipolar molecules are capable of rotation. The polar- 
 izing current acts upon the direction of the molecules, so that they turn their negative surfaces 
 toward the anode, and their positive surfaces to the cathode, whereby the molecules of the intra- 
 polar region have the arrangement of a Volta's pile. In the part of the nerve outside the elec- 
 trodes, the further removed it is the less precisely are the molecules arranged. Hence, the swing 
 of the needle is less the further the extrapolar portion is from the electrodes. 
 
 II. Difference Theory. — The difference theory was proposed by L. Her- 
 mann, and, according to him, the four following considerations are sufficient to 
 explain the occurrence of the galvanic phenomena in living tissues: (i) Proto- 
 plasm, by undergoing partial death in its continuity, whether by injury or by 
 (horny or mucous) metamorphosis, becomes negative toward the uninjured part. 
 (2) Protoplasm, by being partially excited in its continuity, becomes negative to 
 the uninjured -part. (3) Protoplasm, when partially heated in its continuity, be- 
 comes positive, and by cooling negative, to the unchanged part. (4) Protoplasm 
 is strongly polarizable on its surface (muscle, nerve), the polarization constants 
 diminishing with excitement and in the process of dying. 
 
 Streamless Fresh Muscles. — It seems that passive, uninjured, and abso- 
 lutely fresh muscles are completely devoid of a current, e. g. , the heart (Engel- 
 manri), also the musculature of fishes while still covered by the skin. 
 
 As the skin of the frog has currents peculiar to itself, it is possible with certain precautions, after 
 destroying the skin with alkalies, to show the streamless character of frogs' muscles. L. Hermann 
 also finds that the muscle current is always developed after a time, which is very short, when a new 
 transverse section is made. 
 
 Demarcation Current. — Every injury of a muscle or nerve causes at the point of injury (de- 
 marcation surface) a dying substance which behaves negatively to the positive intact substance. 
 The current thus produced is called by Hermann the " demarcation current." If individual parts 
 of a muscle be moistened with potash salts or muscle juice they become negatively electrical ; if 
 these substances be removed, these parts cease to be negative (Biedermann). 
 
 It appears that' all living protoplasmic substance has a special property, whereby injury of a part 
 of it makes it, when dying, negative, while the intact parts remain positively electrical. Thus 
 all transverse sections of living parts of plants -are negative to their surface \Buff); and the same 
 occurs in animal parts, e.g., glands and bones. Engelmann made the remarkable observation that 
 the heart and smooth muscle again lose the negative condition of their transverse section, when the 
 muscle cells are completely dead, as far as the cement substance of the nearest cells ; in nerves, 
 when the divided portion dies, as far as the first node of Ranvier. When all these organs are 
 again completely streamless, then the absolutely dead substance behaves essentially as an indifferent 
 moist conductor. Muscles divided subcutaneously and healed do not exhibit a negative reaction of 
 the surface of their section. 
 
 All these considerations go to show that the pre-existence of a current in living 
 uninjured tissues is very doubtful, and, perhaps, can no longer be maintained. 
 
 Theoretical. — Grilnhagen and L. Hermann explain the electrotonic currents as being due to 
 internal polarization in the nerve fibres between the conducting nucleus of the nerve and the en- 
 closing sheaths. Matteucci found that when a wire is surrounded with a moist conductor, and the 
 covering placed in connection with the electrodes of a constant current, currents similar to the 
 
VARIATIONS OF THE EXCITABILITY DURING ELECTROTONUS. 597 
 
 electrotonic currents in nerves, and due to polarization, are developed. If either the wire or the 
 moist covering be interrupted at any part, then the polarization current does not extend beyond the 
 rupture. The polarization developed on the surface of the wire causes the conducted current to 
 extend beyond the electrodes. Muscles and nerves consist of fibres surrounded by indifferent con- 
 ductors. As soon as a constant current is closed, on their surface, internal polarization is developed, 
 which produces the electrotonic variation ; it disappears again on opening or breaking the current. 
 Polarization is detected by the fact that in a living nerve the galvanic resistance to conduction across 
 a fibre is about five times, and in muscles about seven times greater than in the longitudinal 
 direction. 
 
 Action Currents — The term " action current " is applied by L. Hermann to the currents obtained 
 during the activity of a muscle. When a single stimulation wave (contraction) passes along 
 muscular fibres, which are connected at two points with a galvanometer, then that point through 
 which the wave is just passing is negative to the other. Occasionally, in excised muscles, local 
 contractions occur, and these points are negative to the other passive parts of the muscle (Bieder- 
 mann). In order, therefore, to explain the currents obtained from a frog's leg during tetanus, we 
 must assume that the end of the fibre which is negative partici ates less in the excitement than the 
 middle of the fibre. But this is the case only in dying or fatigued muscles (p. 591, 2). 
 
 According to \ 336, D, the direct application of a constant current to a muscle causes contraction 
 first at the cathode, when the current is closed, and when it is opened, at the anode. This is ex- 
 plained by assuming that, during the closing contraction, the muscle is negative at the cathode, 
 while with the opening contraction the negative condition is at the anode. 
 
 If a muscle be thrown into contraction by stimulating its nerve, then the wave of excitement 
 travels from the entrance of the nerve to both ends of the muscle, which also behave negatively 
 to the passive parts of the muscle. According to the point at which the nerve enters the muscle, 
 the ascending or descending wave of excitement will reach the end (origin or insertion) of the 
 muscle sooner than the other. On placing such a muscle in the galvanometer circuit, then at first 
 that end of the muscle will be negative which lies nearest to the point of entrance of the nerve 
 (e.g., the upper end of the gastrocnemius), and afterward the lower end. Thus there appears rap- 
 idly after each other, at first a descending and then an ascending current in the galvanometer circuit 
 (of course, reversed within the muscle itself) (Sig. Meyer) (§ 332,4). 
 
 The same occurs in the muscles of the human forearm. When these were caused to contract 
 through their nerves, at first the point of entrance of the nerve (10 cm. above the elbow joint) was 
 negative, and then followed the ends of the muscles when the contraction wave, with a velocity of 
 10 to 13 metres per second, reached them (L. Hermann) ((} 399, 1). 
 
 If a completely uninjured, streamless muscle be made to contract directly and in toto, then 
 neither during a single contraction nor in tetanus is there a current, because the whole of the muscle 
 passes at the same moment into a condition of contraction. 
 
 Nerve Currents. — Hermann also supposes that the contents of dying or active nerves behave 
 negatively to the passive normal portion.-.. 
 
 Imbibition Currents — When water flows through capillary spaces, this is accompanied by an 
 electrical movement in the same direction ( Quincke, Zollner). Similarly, the forward movement of 
 water in the capillary interspaces of non-living parts (pores of a porcelain plate) is also connected 
 with electrical movements, which have the same direction as the current of water. The same effect 
 occurs in the movement of water, which results in that condition known as imbibition of a body. 
 We must remember that at the demarcation surface of an injured nerve or muscle imbibition takes 
 place; that also at the contracted parts of a muscle imbibition of fluid occurs ($ 227, II) ; and 
 that during secretion there is a movement of the fluid particles. 
 
 In Plants, electrical phenomena have been observed during the passive bending of vegetable 
 parts (leaves or stalks), as well as during the active movements which are associated with the bend- 
 ing of certain parts, e.g.. as in the mimosa and dionsea (p. 317) {Burdon-Sanderson). These phe- 
 nomena are perhaps explicable by the movement of water which must take place in the interior of 
 the vegetable parts (A. G. Kunkel). The root cap of a sprouting plant is negative to the seed 
 coverings (Hermann) ; the cotyledons positive to the other parts of the seedling (Mitlter-Hett- 
 lingen). In the incubated hen's egg the embryo is -J- , the yelk — [Hermann and v. Gendre). 
 
 335. ELECTRONIC ALTERATION OF THE EXCITABIL- 
 ITY. — Cause of Electrotonus. — If. a certain stretch of a living nerve be trav- 
 ersed by a constant electrical {"polarizing") current, [it passes into a condition 
 of altered excitability {Ritter, 1802, and others), which Du Bois-Reymond 
 called the electrotonic condition, or. simply electrotonus. This condition of altered 
 excitability extends not only over the part actually traversed by the current, intra- 
 polar portion, but it is communicated to the entire nerve. Pfliiger (1859) dis- 
 covered the following laws of electrotonus : — 
 
 At the positive pole anode (Fig. 367, A) the excitability is diminished— this is 
 the region of anelectrotonus ; at the negative pole {cathode — K) it is increased 
 
598 
 
 PROOF OF ELECTROTONUS IN MOTOR NERVES. 
 
 — this is the region of cathelectrotonus. The changes of excitability are most 
 marked in the region of the poles themselves. 
 
 Indifferent Point. — In the intrapolar region a point must exist where the 
 anelectrotonie and cathelectrotonic regions meet, where therefore the excitability- 
 is unchanged ; this is called the indifferent or neutral point. This point lies 
 nearer the anode (z) with a weak current, but with a strong current nearer the 
 cathode (/„) ; hence, in the first case, almost the whole intrapolar portion is more 
 excitable ; in the latter, less excitable. [Expressed otherwise, a weak current in- 
 creases the area over which the negative pole prevails, while the reverse is the case 
 with a strong current.] Very strong currents greatly diminish the conductivity 
 at the anode, and indeed may make the nerve completely incapable of conduction 
 at this part. 
 
 Extrapolar Region. — The extrapolar area, or that lying outside the electrodes, 
 is greater the stronger the current. Further, with the weakest currents, the extra- 
 polar anelectrotonie area is greater than the extrapolar cathelectrotonic. With 
 strong currents this relation is reversed. 
 
 Fig. 367 shows the excitability of a nerve (TV, n) traversed by a constant current in the direction 
 of the arrow. The curve shows the degree of increased excitability in the neighborhood of the 
 cathode (K) as an elevation above the nerve, diminution at the anode (A) as a depression. The 
 
 Fig. 367. 
 
 
 3 
 
 
 
 
 
 //*A 
 
 f x 
 
 A 
 
 + 
 
 
 
 iny' y / 
 
 
 v 
 
 d 
 
 Jc r 
 
 N e a A <\i\i 
 
 ■\. 
 
 
 
 y y 
 
 -n_ '. N. 
 
 
 C 
 
 
 s 
 
 R \ \ 
 
 
 71 
 
 ,* 
 
 .--'' 
 
 
 
 
 
 --' 
 
 
 Scheme of the electrotonic excitability. 
 
 curve m, a, i,,,p, r, shows the degree of excitability with a strong current; e,f, i„ h, k, with a 
 medium current ; lastly, a, b, i, c, d, with a weak current. 
 
 The electrotonic effect increases with the length of the nerve traversed by the current. The 
 changes of the excitability in electrotonus occur instantly when the circuit is closed, while anelec- 
 trotonus develops and extends more slowly. Cold diminishes electrotonus (Hermann and v. 
 Gendre). 
 
 When the polarizing current is opened, at first there is a reversal of the rela- 
 tions of the excitability, and then there follows a transition to the normal condi- 
 tion of excitability of the passive nerve (Pfluger). At the very first moment of 
 closing, Wundt observed that the excitability of the whole nerve was increased. 
 
 I. Proof of Electrotonus in Motor Nerves. — To test the laws of electrotonus, take a frog's 
 nerve-muscle preparation (Fig. 364). A constant current (p. 577) is applied to a limited part of 
 the nerve by means of non-polarizable electrodes. A stimulus, electrical, chemical (saturated solu- 
 tion of common salt), or mechanical is applied either in the region of the anode or cathode; and 
 we observe whether the contraction which results is greater when the polarizing current is opened 
 or closed. We will consider the following cases (Fig. 368): — 
 
 (a) Descending extrapolar anelectrotonus, i, t., with a descending current we have to test 
 the excitability of the extrapolar region at the anode. If the stimulus (common salt) applied at R 
 (while the circuit was open) causes in this case (A) moderately strong contractions in the limb, then 
 these at once become weaker, or disappear as soon as the constant current is transmitted through the 
 nerve. After the circuit is opened, the contractions produced by the salt again occur of the original 
 strength. 
 
PROOF OF ELECTROTONUS IN INHIBITORY NERVES. 
 
 599 
 
 Fig. 368. 
 
 (b) Descending extrapolar cathelectrotonus (A). The stimulus (salt) is at R, and the con- 
 tractions thereby produced are at once increased after closing the polarizing current. On opening 
 it they are again weakened. 
 
 (c) Ascending extrapolar anelectrotonus (B). The salt lies at r. In this case we must 
 distinguish the strength of the polarizing current: (1) When the current is very weak, which can 
 be obtained with the aid of the rheocord (Fig. 344), on closing the 
 polarizing current, there is an increase of the contraction produced by 
 the salt. (2) If, however, the current is stronger, the contractions 
 become either smaller or cease. This is due to the fact that with 
 strong currents the conductivity of the anode is diminished or even 
 abolished (p. 597). Although the salt acts on the excitable nerve, 
 there is no contraction of the muscle, as the conduction of an impulse 
 is prevented by the resistance in the nerve. 
 
 The law of electrotonus may also be demonstrated on a completely 
 isolated nerve. The end of the nerve is properly disposed upon 
 electrodes connected with a galvanometer, so as to obtain a strong 
 current. If the nerve, when the constant current is closed, is stimu- 
 lated in the anelectrotonic area, e. ?., by an induction shock, then the 
 negative variation is weaker than when the polarizing circuit was 
 open. Conversely, it is stronger when it is stimulated in the cathelec- 
 trotonic area (Bernstein). The currents from the extrapolar areas of 
 a nerve in a condition of electrotonus exhibit the negative variation 
 when the nerve is stimulated. 
 
 Proof in Man. — In performing this experiment it is important to 
 remember the distribution of the current in the body. If both elec- 
 trodes, for example, be placed over the course of the ulnar nerve 
 (Fig. 369), the currents entering the nerve at the anode (-)- a a) must 
 diminish the excitability ; only above and below the anode (at c c) the 
 positive current emerges from the nerve and excites cathelectrotonus 
 at these points. Similarly, where the cathode is applied ( — c c) there 
 i< increased excitability; but in higher and lower parts of the nerve, 
 where (at a a) the positive current (coming from -)-) enters the nerve, the excitability is diminished 
 (anelectrotonus) (v. Helmholtz, Erb). If we desire to stimulate in the neighborhood of an elec- 
 trode, then we cannot act upon that part of the nerve whose excitability is influenced by the electrode. 
 
 Fig. 369. 
 
 Method of testing the excita- 
 bility in electrotonus. R, r, 
 R,, r,, where the common 
 salt (stimulus) is applied. 
 
 Scheme oi the distribution of an electrical current in the nerve on galvanizing the ulnar nerve. 
 
 Tn order, therefore, to stimulate directly the same point on which the electrode acts, it is necessary 
 to apply the stimulus at the same time by the electrode itself, e. g., either mechanically or by con- 
 ducting the stimulating current through the polarizing circuit ( Waller and de Watteville). 
 
 II. Proof of Electrotonus in Sensory Nerves. — Isolate the sciatic nerve of a decapitated 
 frog. When this nerve is stimulated in its course with a saturated solution of common salt, reflex 
 movements are excited in the other leg, the spinal cord being still intact. These disappear as soon 
 as a constant current is applied to the nerve, provided the salt lies in the anelectrotonic area (Pfluger, 
 and Zurhelle, Hallstln). 
 
 III. Proof of Electrotonus in Inhibitory Nerves. — To show this, proceed thus : On causing 
 dyspnoea in a rabbit, the number of heart beats is diminished, owing to the action of the dyspnoeic 
 blood on the cardio-inhibitory centre in the medulla oblongata. If, after dividing the vagus on one 
 side," a constant descending current be passed through the other intact vagus, the number of pulse 
 beats is again increased (descending extrapolar anelectrotonus). If, however, the current through 
 
600 
 
 THE LAW OF CONTRACTION. 
 
 the nerve be an ascending one, then with weak currents the number of heart beats increases still 
 more (ascending extrapolar cathelectrotonus). Hence, the action of inhibitory nerves in electrotonus 
 is the opposite of that in motor nerves. 
 
 During the electrotonus of muscle, the excitability of the intrapolar portion 
 is altered. The delay in the conduction is confined to this area alone (v. Bezold) 
 —compare §337, 1. 
 
 336. ELECTROTONUS— LAW OF CONTRACTION.— Opening 
 and Closing Shocks. — A nerve is stimulated both at the moment of the occur- 
 rence and that of disappearance of electrotonus (J. e., by closing and opening the 
 current — Ritter) : (1) When the current is closed, the stimulation occurs only 
 at the cathode, /. e., at the moment when the electrotonus takes place. (2) 
 When the current is opened, stimulation occurs only at the anode, i. e., at the 
 moment when the electrotonus disappears. (3) The stimulation at the occurrence 
 of cathelectrotonus is stronger than at the disappearance of anelectrotonus 
 {Pfluger). 
 
 Ritter's Opening Tetanus. — That stimulation occurs only at the anode, when the current is 
 opened, was proved by Pfluger by means of " Ritter's opening tetanus." Ritter's tetanus consists 
 in this, that when a constant current is passed for a long time through a long stretch of nerve, on 
 opening the current, tetanus lasting for a considerable time results. If the current was a descending 
 one, then this tetanus ceases at once after section of the intrapolar area, a proof that the tetanus 
 resulted from the now separated anode. If the current was an ascending one, section of the nerve 
 has no effect on the tetanus. 
 
 Pfluger and v. Bezold also proved that the closing contraction at the cathode precedes that at the 
 anode. Thus, they observed that with a descending current the closing contraction in the muscle 
 at the moment of closing occurred earlier than the opening contraction at the moment of opening ; 
 and, conversely, with an ascending current, the closing contraction occurred later, and the opening 
 contraction sooner. The difference in time corresponds to the time required for the propagation of 
 the impulse in the intrapolar region (\ 337). If a large part of the intrapolar region in a frog's 
 nerve be rendered inexcitable by applying ammonia to it, then only the electrode next the mus- 
 cle stimulates, i. c, always on closing a descending current and on opening an ascending one 
 (Biedermann). 
 
 A. The law of contraction is valid for all kinds of nerves. — I. The contrac- 
 tion occurring at the closing or opening of a constant current varies with (a) the 
 direction (Pfaff), and (b) the strength of the current (Heidenhain). 
 
 (1) Very feeble currents, in conformity with the third of the above state- 
 ments, cause only a closing contraction, both with an ascending and a descend- 
 ing current. The disappearance of electrotonus is so feeble a stimulus as not to 
 excite the nerve. 
 
 (2) Medium currents cause opening or closing contractions both with an 
 ascending and a descending current. 
 
 (3) Very strong currents cause only a dosing contraction with a descending cur- 
 rent ; the opening shock does not occur, because, with very strong currents, al- 
 most the whole of the intrapolar portion of the electrotonic nerve is incapable of 
 conducting an impulse (p. 598). Ascending currents cause only an of ening con- 
 traction for the same reason. With a certain strength of current, the muscle re- 
 mains tetanic while the current is closed (" closing tetanus"). 
 
 [The law of contraction is formulated : — R = rest ; C = contraction.] 
 
 Strength of Current. 
 
 Ascending. 
 
 Descending. 
 
 On Closing. 
 
 On Opening. 
 
 On Closing. 
 
 On Opening. 
 
 Weak, 
 
 c 
 c 
 
 R 
 
 R 
 C 
 C 
 
 c 
 c 
 c 
 
 R 
 
 c 
 
 R . 
 
 Strong, 
 
THE LAW OF CONTRACTION. 601 
 
 II. In a dying nerve, losing its excitability, according to the Ritter-Valli law 
 (§ 3 2 S> 7)5 tne l aw °f contraction is modified. In the stage of increased excita- 
 bility weak currents cause only closing contractions with both directions of the 
 current. In the following stage, when the excitability begins to diminish, weak 
 currents cause opening and closing contractions with both currents. Lastly, when 
 the excitability is very greatly diminished, the descending current is followed only 
 by a closing contraction, and the ascending by an opening contraction (Ritter, 
 1829). 
 
 III. As the various changes in excitability occur in a centrifugal direction 
 along the nerve, we may detect the various stages simultaneously at different parts 
 along the course of the nerve. According to Valentin, Fick, CI. Bernard, and 
 Schiff, the living intact nerve shows only a closing contraction with both direc- 
 tions of the current, and opening contractions only with very strong currents. 
 
 Fleischl's Law of Contraction. — v. Fleischl and Strieker have stated a different law in re- 
 spect to the fact that the excitability varies at certain points in the course of a nerve. The sciatic 
 nerve is divided into three areas : (1) Stretches from the muscle to the place where the branches 
 for the thigh muscles are given off; (2) from here to the intervertebral ganglion; (3) from here 
 into the spinal cord. Each of these three areas consists'of two parts (" upper and lower pole"), 
 which adjoin each other at an equator. In each upper pole the excitability of the nerve is greater 
 for descending currents, and in each lower pole for ascending ones. At each equator the excitabil- 
 ity of the nerve is the same for ascending and descending currents. The difference in the activity, 
 due to the direction of the current, is greater for each stretch of nerve the greater this stretch is dis- 
 tant from the equator. The excitability is less at those points of the nerve where the three areas 
 join each other. 
 
 Eckhard observed that, on opening an ascending medium current applied to the hypoglossal nerve 
 of a rabbit, one-half of the tongue exhibited a trembling movement instead of a contraction, while 
 on closing a descending current the same result occurred (§ 297, 3). According to Pfluger, the 
 molecules of the passive nerve are in a certain state of medium mobility. In calhelectrotonus the 
 mobility of the molecules is increased, in anelectrotonus, diminished. 
 
 B. The law for inhibitory nerves is similar. Moleschott, v. Bezold, and 
 Donders have found similar results for the vagus, with this difference, that, instead 
 of the contraction of a muscle, there is inhibition of the heart. 
 
 C. For sensory nerves, also, the result is the same, but we must remember 
 that the perceptive organ lies at the central end of the nerve, while in a motor 
 nerve it (muscle) is at the periphery. Pfluger studied the effect of closing and open- 
 ing a current on sensory nerves by observing the reflex movement which 
 resulted. Weak currents cause only closing contractions ; medium currents both 
 opening and closing contractions : descending strong currents only opening con- 
 tractions ; and ascending only closing contractions. Weak currents applied to 
 the human skin cause a sensation with both directions of the current only at closing ; 
 strong descending currents a sensation only at opening ; strong ascending currents a 
 sensation only at closing {Marianini, Matteucci). When the current is closed there 
 is prickly feeling, which increases with the strength or the current (Voltd). Analo- 
 gous phenomena have been observed in the sense organs (sensations of light 
 and sound) by Volta and Ritter. 
 
 D. In muscle, the law of contraction is proved thus — by fixing one end of the 
 muscle, keeping it tense, so that it cannot shorten, and opening and closing the 
 current at this end. The end of the muscle, which is free to move, shows the 
 same law of contraction as if the motor nerve was stimulated {v. Bezold). On 
 closing the current, the contraction begins at the cathode ; on opening, at the 
 anode (Engelmanri). E. Hering and Biedermann showed more clearly that both 
 the closing and- opening contractions are purely polar effects ; when a weak cur- 
 rent applied to a muscle is closed, the first effect is a small contraction limited to 
 the cathodic surface of the muscle. Increase of the current causes increased con- 
 traction which extends to the anode, but which is weaker there than at the 
 cathode ; at the same time, the muscle remains contracted during the time the cur- 
 rent is closed. On opening, the contraction begins at the anode ; even after open- 
 
602 TRANSMISSION OF NERVOUS IMPULSES. 
 
 ing, the muscle for a time may remain contracted, which ceases on closing the 
 current in the same direction. 
 
 By killing the end of a muscle in various ways, the excitability is diminished near this part. 
 Hence, at such a place the polar action is feeble (van Loon and Engelmann, Biedermann). 
 Touching a part with extract of flesh, potash, or alcohol diminishes locally the polar action, while 
 soda salts and veratrin increase it (Biedermann). 
 
 Closing Continued Contraction. — The moderate continued contraction, which is sometimes 
 observed in a muscle while the current is closed (Fig. 301, 0), depends upon the abnormal pro- 
 longation of the closing contraction at the cathode when a strong stimulus is used, or during the 
 stage of dying, or in cooled winter frogs; sometimes the opening of the current is accompanied by 
 a similar contraction proceeding from the anode (Biedermann). This tetanus is also due to the 
 summation of a series of simple contractions (\ 298, III). By acting on a muscle with a two per 
 cent, saline solution containing sodic carbonate, the duration of the contraction is increased consid- 
 erably, and occasionally the muscle shortens rhythmically (j! 296) (Biedermann). 
 
 If the whole muscle is placed in the circuit, the closing contraction is strongest 
 with both directions of the current ; during the time the current is closed a con- 
 tinued contraction is strongest when the current is ascending ( Wundf). 
 
 Inhibitory Action. — The constant current, when applied to a muscle in a 
 condition of continued and sustained contraction, has exactly the opposite effect 
 to that on a relaxed muscle. If a constant current be applied by means of non- 
 polarizable electrodes to a muscle in a state of continued contraction, e.g., after 
 poisoning with veratrin or through the contracted ventricle, when the current is 
 closed there is a relaxation beginning at the anode and extending to the other 
 parts ; on opening the current applied to muscle in continued contraction, the 
 relaxation proceeds from the cathode. Pawlow found nerve fibres in the adductor 
 muscle of the mussel, whose stimulation caused relaxation of the muscular con- 
 traction. 
 
 Ritter's Opening Tetanus. — If a nerve or muscle be traversed by a constant 
 current for some time, we often obtain a prolonged tetanus, after opening the 
 current (Ritter's opening tetanus, 1798). It is set aside by closing the original 
 current, while closing a current in the opposite direction increases it ("Volta's 
 alternative' 1 '''). The continued passage of the current increases the excitability 
 for the opening of the current in the same direction, and for the closing of the 
 reverse current ; conversely, it diminishes it for the closing of the current in the 
 same direction, and for the opening of the reverse current (Volta, Rosenthal, 
 Wundf). 
 
 In a nerve-muscle preparation used to prove the law of contraction, of course a demarcation cur- 
 rent is developed in the nerve (§ 334, II). If an artificial, weak stimulating current be applied to 
 such a nerve, we obtain an interference effect due to these two currents ; closing a weak current 
 causes a contraction, which, however, is not properly a closing contraction, but depends upon the 
 opening of a branch of the demarcation current ; conversely, the opening of a weak current may 
 excite a contraction, which is really due to the closing of a side branch of the nerve current in a 
 secondary circuit through the electrodes (Hering, Biedermann, Griitzner). According to Griitzner 
 and Tiegerstedt, the cause of the opening contraction is partly due to the occurrence of polarizing 
 after-currents (\ 333). 
 
 Engelmann and Griinhagen explain the occurrence of opening and closing tetanus, thus, as due 
 to latent stimulations, drying, variations of the temperature of the prepared nerve, which of them- 
 selves are too feeble to cause tetanus, but which become effective if an increased excitability obtains 
 at the cathode after closure, and at the anode after opening the current. 
 
 Biedermann showed that, under certain conditions, two successive opening contractions can be ob- 
 tained in a frog's nerve-muscle preparation, the second and later one corresponding to Ritter's 
 tetanus. The first of these contractions is due to the disappearance of anelectrotonus in Pfiuger's 
 sense ; the second is explained, like Ritter's opening tetanus, in Engelmann's and Grunhagen's 
 sense. 
 
 337. TRANSMISSION OF NERVOUS IMPULSES.— i. If a 
 motor nerve be stimulated at its central end (1) a condition of excitation is 
 set up, and (2) an impulse is transmitted along the nerve to the muscle with a 
 certain velocity. The latter depends on the former and represents the function 
 of conductivity. The velocity is about 27^ metres [about 90 feet] per second 
 
METHOD OF ESTIMATING RAPIDITY OF A NERVE IMPULSE. 603 
 
 (v. Helmholtz) and for the human motor nerves 33.9 [100 to 120 feet per second] 
 (v. Helmholtz and Baxt). The second depends on the first. 
 
 The velocity is less in the visceral nerves, e.g., in the pharyngeal branches of the vagus 8.2 
 metres [26 feet] (Chauveau) ; in the motor nerves of the lobster 6 metres [18 feet] (Fridiricq and 
 van de Velde). 
 
 Modifying Conditions. — The velocity is influenced by various conditions : 
 Temperature. — It is lessened considerably by cold {v. Helmholtz), but both high 
 and low temperatures of the nerve (above or below 15 to 25 C.) lessen it 
 (Steiner and Trojtzky) ; also curara, the electrotonic condition (v. Bezold) ; or only 
 anelectrotonus, while cath'electrotonus increases it {Rutherford, Wundt). It 
 varies also with the length of the conducting nerve, but it increases with the 
 strength of the stimulus (v. Helmholtz and Baxt ), although not at first (v. Vint- 
 schgau). 
 
 Methods. — (1) V. Helmholtz (1850) estimated the velocity of the nerve impulse in a frog's 
 motor nerve, after the method of Pouillet. The method depends upon the fact that the needle of 
 a galvanometer is deflected by a current of very short duration ; the extent of the deflection being 
 
 Fig. 370. 
 
 w k 
 
 V. Helmholtz's method of estimating the velocity of a nerve impulse. 
 
 proportional to the duration and strength of the current. The apparatus is so arranged that the 
 "time-marking current" is closed at the moment the nerve isfstimulated, and opened again when 
 the muscle contracts. If the nerve attached to a muscle be now stimulated at the further point 
 from the muscle, and a second time near its entrance to the muscle, then in the latter case the time 
 between the application of the stimulus and the beginning of the contraction of the muscle, i. e., 
 the deflection of the galvanometer, will be less than in the former case, as the impulse has to trav- 
 erse the whole length of the nerve to reach the muscle. The difference between the two times is 
 the time required by the impulse to traverse a given distance of nerve. Fig. 370 shows in a. 
 diagrammatic manner the arrangement of the experiment. The galvanometer, G, is placed in the 
 time-marking circuit (open at first), a, b (element), c (piece of platinum on a key, W), introduced 
 into the time-marking circuit, d, e,f, h. The circuit is made by closing the key, S, when d de- 
 presses the platinum plate of the key, W. At once, when the current is closed, the magnetic 
 needle is deflected, and its extent noted. At the same moment in which the current between c and 
 d is closed the primary circuit of the induction machine is opened, the circuit being i, k, I (element), 
 m, O (primary spiral), p. Thereby an opening shock is induced in the secondary spiral, R, which 
 stimulates the nerve of the frog's leg at ». Thus, the closing of the galvanometer circuit exactly 
 coincides with the stimulation of the nerve. The impulse is propagated through the nerve to the 
 muscle, M, and the latter contracts when the impulse reaches it, at the same time opening the time- 
 
604 METHOD OF ESTIMATING RAPIDITY OF A NERVE IMPULSE. 
 
 measuring circuit at the double contact, e and f, by raising the lever, H, which rotates on x. At 
 the moment of opening, the further deflection of the magnetic needle ceases. The contact at / is 
 made by a pointed cupola of mercury. When the lever, H, falls after the contact of the muscle, 
 so that the point, e, comes into contact with the underlying solid plate, y, the contact at f still re- 
 mains open, i. e., through the galvanometer circuit. If the nerve be stimulated with the opening 
 shock, first at », and then at N, the deflection of the needle is greater in the former than in the 
 latter case. From the difference, we calculate the time for the conduction of the impulse in the 
 stretch of the nerve between n and N. 
 
 [2. A simpler method is that shown in the scheme, Fig. 371. Use a pendulum 
 
 Fig. 371. 
 
 Scheme for measuring the velocity of nerve energy. _/| clamp for femur ; m, muscle ; N, nerve ; a , near, b, removed 
 from, C, commutator ; II, secondary ; I, primary spiral of induction machine ; B, battery ; 1,2, key ; 3, tooth 
 on the smoked plate P. 
 
 or spring myograph (Fig. 294), and suspend a frog's gastrocnemius (m), with a 
 long portion of the sciatic nerve (N) dissected out, by fixing the femur in a clamp 
 (/"), while the tendo Achilles is fixed to a lever, which inscribes its movements on 
 the smoked glass plate (P) of the myograph; place the key of the myograph (2) 
 in the circuit with the battery (B), and the primary circuit of the induction 
 machine (I). To the secondary coil (II) attach two wires, and connect them 
 with a commutator without cross-bars (C). Connect the other binding screws 
 of the commutator with two pairs of wires, arranged so that one pair can stimu- 
 
 Fig. 372. 
 
 .-, curve obtained on stimulating a nerve (man) near the muscle ; 2, when the stimulus was applied to the nerve at a 
 distance from the muscle ; D, vibrations of a tuning fork (250 per second). 
 
 late the nerve near the muscle (#), and the other at a distance from it (b). When 
 the glass plate swings from one side to the other, the tooth (3) on its framework 
 opens the key (2) in the primary circuit, and if the commutator be in the position 
 indicated, then the induced current will stimulate the nerve at a, and a curve will 
 be obtained on the glass plate. Rearrange the pendulum as before, but turn the 
 handle of the commutator, and allow the pendulum to swing again. This time 
 the induced current will stimulate the nerve at b, and a second contraction, a 
 
DOUBLE CONDUCTION IN NERVES. 605 
 
 little later than the first one, will be obtained. Register the velocity of the swing 
 by means of a tuning fork, and the curve obtained will be something like Fig. 
 372, although this curve was obtained on a cylinder traveling at a uniform rate. 
 The difference between the beginning of the a and b curves indicates the time 
 that the nerve impulse took to travel from b to a. This time is measured by the 
 tuning fork, and if the distance between the points a and b is known, then the 
 calculation is a simple one. Suppose the stretch of nerve between a and b to be 
 2 inches, and the time required by the impulse to travel from b to a to be ^£-5- 
 second, then we have the simple .calculation — 2 inches : 12 inches: : ^7" : -jV'> 
 or 80 feet per second. In Fig. 372 the experiment was made on man ; the curve 
 1 was obtained by stimulating the nerve near the muscle, and 2 when the nerve 
 was stimulated at a distance of 30 centimetres. The interval between the ver- 
 tical lines corresponds to yj-j- second, i.e., the time required by the nerve impulse 
 to pass along 30 centimetres of nerve, which is equal to a velocity of 30 metres 
 (90 feet) per second.] 
 
 In man v. Helmholtz and Baxt estimated the velocity of the impulse in the median nerve by 
 causing the muscles of the ball of the thumb to write off their contractions on a rapidly revolving 
 cylinder. [In this case the pince myographique of Marey (§ 708) may be used. The ends of the 
 pince are applied so as to embrace the ball of the thumb, so that when the muscles contract the 
 increase in thickness of the muscles expands the pince, which acts on a Marey's tambour, by which 
 the movement is transmitted to another tambour provided with a writing style, and inscribing its 
 movements upon a rapidly moving surface, either rotary or swinging.] The nerve is stimulated at 
 one time in the axilla and again at the wrist. Two curves are obtained, which, of course, do not 
 begin at the same time. The difference in time between the beginning of the two curves is the 
 time taken by the impulse to traverse the above-mentioned length of nerve. [The time is easily 
 ascertained by causing a tuning fork of a known rate of vibration to write its movements under the 
 curves.] 
 
 3. In the sensory nerves of man the velocity of the impulse is probably 
 about the same as in motor nerves. The rates given vary between 94-30 metres 
 [280-90 feet] per second (v. Helmholtz, Kohlrausch, v. Wittich, Schelske and 
 others). 
 
 Method. — Two points are chosen as far apart as possible, and at unequal distances from the 
 brain, and they are successively excited by a momentary stimulus, e.g., an opening induction shock 
 applied successively to the tip of the ear and the great toe. The moment the stimulus is applied, 
 it is indicated on the registering surface. The person experimented on is provided with a key 
 attached to an electric arrangement, by which he can mark on the registering surface the moment he 
 feels the sensation in each case. 
 
 Reaction Time. — The time which elapses between the application of the stimulus and the 
 reaction is called the " reaction time." It is made up of the time necessary for conduction in the 
 sensory nerve, that for the process of perception in the brain, the conduction in the motor nerves to 
 the muscles, by which the signs on the registering surface were made, and lastly by the latent 
 period (p. 516). The reaction time is usually about 0.125 t0 °- 2 second. 
 
 Pathological. — The conduction in the cutaneous nerves is sometimes greatly delayed in altera- 
 tions of the cutaneous sensibility in certain diseases of the spinal cord (§ 364). The sensation itself 
 may be unchanged. Sometimes only the conduction for painful impressions is retarded, so that a 
 painful impression on the skin is first perceived as a tactile sensation, and afterward as pain, or con- 
 versely. When the interval of time between these two sensations is long, then there is a distinctly 
 double sensation (Naunyn, Jiemak, Eulenburg). It is rarely that voluntary movements are exe- 
 cuted much more slowly from causes depending on the motor nerves, but occasionally the time 
 between the voluntary impulse and the contraction is lengthened, but there may be in addition 
 slower or longer continued contraction of the muscle. In tabes dorsalis or locomotor ataxia, the 
 discharge of reflex movements is delayed ; it is slower with thermal stimuli (60°) than with cold 
 ones (5° C, Ewald). 
 
 338. DOUBLE CONDUCTION IN NERVES.— Conductivity is 
 
 that property of a living nerve in virtue of which, on the application of a 
 stimulus, it transmits an impulse. [The nature of a nerve impulse is entirely 
 unknown ; we may conveniently term the process nerve motion, but there is 
 some reason to believe that nerve energy is transmitted by some sort of molec- 
 ular vibration.] The conductivity is destroyed by all influences or conditions 
 
606 THERAPEUTICAL USES OF ELECTRICITY — RHEOPHORES. 
 
 which injure the nerve in its continuity (section, ligature, compression, destruction 
 by chemical agents) ; or which abolish the excitability at any part of its course 
 (absolute deprival of blood ; certain poisons, e.g. , curara for motor nerves ; also 
 strong anelectrotonus, § 335). 
 
 Law of Isolated Conduction. — Conduction always takes place only in the 
 continuity of fibres, the impulse never being transferred to adjoining nerve fibres. 
 
 Double Conduction. — Although apparently conduction in motor nerves 
 takes place only in a centrifugal direction toward the ^uscles, and in sensory 
 nerves in a centripetal direction, i.e., toward the centre ; nevertheless, experiment 
 has proved that a nerve conducts an impulse in both directions. If a pure motor 
 or sensory nerve be stimulated in its course, an impulse is propagated at the same 
 time in a centrifugal and in a centripetal direction. This is the phenomenon of 
 ' ' double conduction. ' ' 
 
 Proofs. — 1. If a nerve be stimulated, its electro-motive properties are affected 
 both above and below the point of stimulation (see Negative Variation in Nerves, 
 
 § 33 2 > 
 
 2. Union of Motor and Sensory Nerves. — If the hypoglossal and lingual 
 nerves be divided in a dog, and if the peripheral end of the hypoglossal be 
 stitched, so as to unite with the central end of the lingual {Bidder), then, several 
 months after the union and restitution of the nerves, stimulation of the central 
 end of the lingual causes contraction in the corresponding half of the tongue. 
 Hence, it has been assumed that the lingual, which is the sensory nerve of the 
 tongue, must conduct the impulse in a peripheral direction to the end of the 
 hypoglossal. 
 
 This experiment is not conclusive, as the trunk of the lingual receives high up the centrifugal 
 fibres from the seventh, viz., the chorda tympani, which may unite with those of the hypoglossal. 
 Further, if the chorda be divided and allowed to degenerate before the above described experiment 
 is made, then no contractions occur on stimulating the lingual above the point of union (J 349). 
 
 3. Bert's Experiment. — Paul Bert removed the skin from the tip of the tail of a rat, and 
 stitched it into the skin of the back of the animal, where it united with the tissues. After the 
 first union had taken place, the tail was then divided at its base, so that the tail, as it were, grew 
 out of the skin on the back of the animal. On stimulating the tail, the animal exhibited signs of 
 sensation, so that the impulses in the sensory nerves must have traversed the nerves from the base 
 to the tip of the tail (g 325). 
 
 4. Electrical Nerves. — If the free end of the electrical centrifugal nerves 
 of the malapterurus be stimulated, the branches given off above the point of 
 stimulation are also excited, so that the whole electrical organ may discharge its 
 electricity {Babuchin, Maniey). 
 
 339. ELECTRO-THERAPEUTICS— REACTION OF DEGENERATION.— Elec: 
 
 tricity is frequently employed for therapeutical purposes, the rapidly interrupted current of the in- 
 duction machine, or Faradic current, being frequently used (especially since Duchenne, 1847), the 
 magneto-electrical apparatus, and the extra-current apparatus. The constant or galvanic current 
 is also used, especially since Remak's time, 1855 ((S 330). 
 
 I. In paralysis, Faradic currents are applied either to the muscles themselves {Duchenne), or 
 the points of entrance of the motor nerves (v. Ziemssen), by means of suitable electrodes, or rheo- 
 phores covered with sponge, etc., and moistened. 
 
 [Rheophores. — Many different forms are used, according to the organ or part to be stimulated, 
 or the effect desired. When electricity is applied to the skin to remove anaesthesia, hyperesthesia, 
 or altered sensibility, and we desire to limit the effect to the skin alone, then the rheophores are 
 applied dry, and are usually made of metal. If, however, deeper-seated structures, as muscles or 
 nerve trunks, are to be affected, the skin must be well moistened and soltened by sponging with 
 warm water, while the rheophores are fitted with sponges moistened with common salt and water 
 which diminishes the resistance of the skin to the passage of electricity (Figs. 373-375)-] > 
 
 In faradizing the paralyzed muscle, the object is to cause artificial movements in it, and thus pre- 
 vent the degeneration which it would otherwise undergo, merely from inaction. If, in addition to 
 the motor nerves, its trophic nerves are also paralyzed, then a muscle atrophies, notwithstanding the 
 faradization ($ 325, 4). The use of the induced current also improves a paralyzed muscle, as it in- 
 creases the blood stream through it, while it affects the metabolism of the muscle refiexly. In 
 addition, weak currents may restore the excitability of enfeebled nerves [v. Bezold, Fngelmatttt). 
 
THERAPEUTICAL ACTIONS OF THE CONSTANT CURRENT. 
 
 607 
 
 The Figs. 376, 377, 378, and 379 indicate the positions of the motor points of the extremities, 
 where, by stimulating at the entrance of the nerve, each muscle may be caused to contract singly. 
 In <j 349 the motor points of the face, and in \ 347 those oi the neck, are indicated. 
 
 The constant current may be employed as a stimulus when it is closed and opened in the form 
 of an interrupted current, by altering its direction and increasing or diminishing its intensity, but it 
 also causes a polar action. On closing the current, the nerve at the cathode is stimulated ; similarly, 
 on opening the current, at the anode (<g 336). Thus, when the current is closed, the excitability of 
 the nerve is increased at the cathode (g 335), which may act favorably upon the nerve. Increased 
 excitability in electrotonus at the anode, although feebler, has been observed during percutaneous 
 galvanization in man. This is especially the case by repeatedly reversing the current, sometimes 
 also by opening and closing, or even with a uniform current. If the increase of the excitability is 
 obtained, then the direction of the current increases the excitability on closing the reverse current, 
 and on opening the one in the same direction. 
 
 Restorative Effect. — Further, in using the constant current, we have to consider its restorative 
 effects, especially when it is ascending. R. Heidenhain found that feeble and fatigued muscles re- 
 cover after the passage of a constant current through them. 
 
 Fig. 375. 
 
 Fig. 373. 
 
 Fig. 374 
 
 T 
 
 Double sponge rheophore. 
 
 Disk rheophore. 
 
 Metallic brush ( Weiss). 
 
 Lastly, the constant current may be useful from its catalytic or cataphoric action (ji 328). The 
 effect is directly upon the tissue elements. It may also act directly or reflexly upon the blood and 
 lymph vessels. 
 
 Faradization in Paralysis. — If the primary cause of the paralysis is in the muscles themselves, 
 then the induced current is generally applied directly to the muscles themselves by means of sponge 
 electrodes (Fig. 373) ; while, if the motor nerves are the primary seat, then the electrodes are 
 applied over them. The current used must be only of very moderate strength ; strong tetanic con- 
 tractions are injurious, and so is too prolonged application (Alb. Eulenburg). 
 
 The galvanic current may also be applied to the muscles or to their motor nerves, or to the cen- 
 tres of the latter, or to both muscle and nerve simultaneously. As a rule, the cathode is placed nearer 
 the centre, as it increases the excitability. When the electrode is moved along the course of the nerve, 
 or when the strength of the current is varied, the action is favored. If the seat of the lesion is in 
 the central nervous system, then the electrodes are applied along the vertebral column, or on the 
 vertebral column, and the course of the nerves at the same time, or one on the head and the other 
 on a point as near as possible to the supposed seat of the lesion. The current must not be too strong 
 nor applied too long. 
 
 Induced v. Constant Current : Reaction of Degeneration. — Paralyzed nerves and muscles 
 behave quite differently as regards the induced (rapidly interrupted) and the constant current. This 
 is called the " reaction of degeneration." We must remember the physiological fact that a dying 
 
608 
 
 REACTION OF DEGENERATION. 
 
 nerve attached to a muscle (§ 325), and also the muscles of a curarized animal, react much less 
 strongly to rapidly interrupted currents than fresh non-curarized muscles. Baierlach, in 1859, found 
 that in a case of facial paralysis the facial muscles contracted but feebly to the induced current, but 
 very energetically on the constant current being used. The excitability for the constant current may 
 
 
 Fig. 376. 
 
 
 
 N. radialis. 
 
 M. triceps (caput <*xt.) 
 
 
 M. brachial, intern. / 
 
 M. triceps . 
 1 (caput :ong ) 
 
 
 M. aupioatorlwng. // 
 
 / M. deltoideus 
 
 
 M. radial, ext.. long. / // 
 
 / \ (post, half). 
 Il \ . (N. axillaris). 
 
 M. radla 1 . ext. biw 
 
 » M ulnar, ext. // // 
 
 
 M. extens. digit, communis. 
 
 I 11 supiuat. beev. / // // 
 
 
 M. extenB. digit rain. \ 
 
 
 jlPu 
 
 M. extens. indicia. . \ 
 
 
 M. abduct, pollic. long. , 
 
 M. extens. pollic. brev. , 
 H. extens. poll. long. v 
 
 M. abduct, digit, mln. (N. ulnaris.) 
 
 Mm. inteross. dorsal. I, II, III, et IV. 
 
 (N. ulnarisj 
 
 Motor points of the radial nerre and the muscles supplied by it ; dorsal surface. 
 
 Fig. 377. 
 
 M. deltoideus (ant. half) N. axillaris. 
 N. musculo-cutaneus. 
 M. biceps bractiii. 
 
 M. hrach. anticas. 
 
 N. medianus. 
 
 M. or teres. 
 
 11. flex, digitor. commnn. profund 
 11. flex, carpi radialis. 
 
 M. flex, digitor. snblim. 
 
 M flex dig euhl. 
 
 i (dig. ind etniin.) 
 
 M. flex poll. 
 
 longtw. 
 
 \ A. medl- 
 
 M. abdnctor pollic, brer. 
 M opponens poiiicla. 
 M. flex. poll. brev. 
 
 M. abductor pollic brer, 
 Mia. lumbrica.ea 
 let II. 
 
 Mm. lainbrl- 
 caleallletlV. 
 
 M. opponens digit min. 
 M. flexor digit, min. 
 M. abductor digit min. 
 
 M. r ftlmiiris Hit. 
 
 N. ulnaris. M. flexor carpi ulnaris. N. ulnaris. 
 
 Motor points of the median and ulnar nerves, with the muscles supplied by them. 
 
 be abnormally increased, but may disappear on recovery taking place. According to Neumann, it 
 is the longer duration of the constant current as opposed to the momentary closing and opening of 
 the induced current which makes the contraction of the muscle possible. If the constant current be 
 
REACTION OF DEGENERATION. 
 
 609 
 
 broken as rapidly as the Faradic current is broken, then the constant current does not cause contrac- 
 tion. Conversely, the induced current may be rendered effective by causing it to last longer. We 
 may also keep the primary circuit of the induction machine closed, and move the secondary spiral 
 to and fro along the slots. Thus we obtain slow gradations of the induced current which act ener- 
 getically upon curarized muscles (Briirke). Hence, in stimulating a muscle or nerve, we have to 
 consider not only the strength, but also the duration, of the current, just as the deflection of the 
 magnetic needle depends upon these two factors. 
 
 [Galvanic excitability is the term applied to the condition of a nerve or muscle, whereby it re- 
 sponds to the opening or closing of a continuous current. The effects differ according as the current 
 is opened or closed, and according to its strength. As a rule, the cathode causes a contraction 
 
 Fig. 378. 
 
 N. crural is. 
 
 Xi 
 O 
 
 N. obturator, 
 
 M. pectineus, 
 
 M. adductor magnus, 
 
 M adduct. longus. 
 
 N. peroneus. 
 
 M. tibial, antic. 
 
 M. exten. dig com. long, 
 
 M. peroneus longus. 
 
 M. peroneus brevis. 
 
 M. ex tens, hallucis long. 
 
 M, extens. digit, comm, 
 brevis. 
 
 M. tensor fasciae lata; 
 (Nn. glut. sup.}. 
 
 M. quadriceps femoris 
 
 (general centre). 
 
 M. rectus femoris. 
 
 M. cruralis. 
 
 M. vastus externus. 
 
 M. vastus interims. 
 M. gastrocnem. extern. 
 
 M. soleus. 
 
 M. flexor hallucis long. 
 y M. abductor digiti. min. 
 
 Z 
 
 n 
 
 c 
 
 Mm. interossei dorsales. 
 
 Motor points of the peroneal and tibial nerves on the front of the leg ; the peroneal on the left, the 
 tibial on the right (after Eichhorst). 
 
 z 
 
 a 
 
 3 
 
 c 
 o> 
 
 Er 
 
 chiefly at closure, the anode at opening the current, while the cathode is the stronger stimulus.. 
 With a weak current the cathode produces a simple contraction on closing the current, but no con- 
 traction from the anode. With a medium current we get with the cathode a strong closing contrac- 
 tion but no opening contraction, while the anode excites feeble opening and closing contractions. 
 With a strong current we get with the cathode a tetanic contraction at closure, and a perceptible- 
 contraction at opening, while with the anode there is contraction both at opening and closing.] 
 
 [The law of contraction is usually expressed by the following formula {Ross, after Erb) : An = 
 anode, Ca = cathode, C = contraction, c = feeble contraction, C = strong contraction, S = 
 closure of current, O = opening of current, Te = tetanic contraction ; so that, expressing the 
 above statements briefly, we have — 
 
 39 
 
610 
 
 REACTION OF DEGENERATION. 
 
 Weak currents produce Ca S C ; 
 
 Medium " " Ca S C, An S c, An O c ; 
 
 Strong " " Ca S Te, An S C, An O C, Ca Of.] 
 
 [Typical Reaction of Degeneration. — When the reaction of the nerve and 
 muscle to electrical stimulation is altered both qualitatively and quantitatively, 
 we have the reaction of degeneration, which is characterized essentially by the 
 following conditions] : The excitability of the muscles is diminished or abolished 
 for the Faradic current, while it is increased for the galvanic current from the 
 3d~s8th day ; it again diminishes, however, with variations, from the 72d-8oth 
 day ; the anode closing contraction is stronger than the cathode closing contrac- 
 tion. The contractions in the affected muscles occur slowly in a peristaltic manner, 
 
 Fig. 379. 
 
 /M. biceps, fern. (cap. long.) 
 (grt. sciat.). 
 
 )M. biceps, fern. (cap. brev.) 
 (grt. sciat.). 
 
 N. peroneus. 
 
 M. gluteus maximus (great sciatic). 
 
 N. ischiadicus. 
 
 M. adduct. magnus (n. obt.). 
 
 M. semitendinosus (grt. sciat.) 
 
 M. semimembranosus (grt. 
 sciat.). 
 
 N. tibialis. 
 
 M. gastrocnem. (cap. extr.). I 
 M. gastrocnem. (cap. int.). 
 
 M. soleus. 
 
 M. flex. dig. comm. long. 
 M. flexor hallucis longus. 
 
 N. tibialis. 
 
 Motor points of the sciatic nerve and its branches j the peroneal and tibial nerves. 
 
 and are local, in contrast with the rapid contraction of a normal muscle. The 
 diminution of the excitability of the nerves is similar for the galvanic and Faradic 
 currents. If the reaction of the nerves be normal, while the muscle during direct 
 stimulation with the constant current exhibits the reaction of degeneration, we 
 speak of "partial reaction of degeneration" {.ErP), which is constantly 
 present in progressive muscular atrophy (Erb, Gunther). 
 
 [The " reaction of degeneration " may occur before there is actual paralysis, as in lead poison- 
 ing. When it occurs, we have to deal with some affection of the nerve fibres or of the trophic 
 nerve cells. When it is established, (il stimulation of the nerve with Faradic and galvanic elec- 
 tricity does not cause contraction of the muscle ; (2) direct Faradic stimulation of the muscles does 
 not cause contraction; (3) the galvanic current usually excites contraction more readily than in a 
 normal muscle, so that the muscle responds to much feebler currents than act on healthy muscles; 
 
ELECTRICAL CHARGING OF THE BODY. 611 
 
 but the contraction is longer and more of a tonic character, and shows a tendency to become tetanic] 
 [The electrical excitability is generally unaffected in paralysis of cerebral origin, and in some forms 
 of spinal paralysis, as primary lateral sclerosis and transverse myelitis (Ross) ; but the " reaction of 
 degeneration" occurs in traumatic paralysis due to injury of the nerve trunks, neuritis, rheumatic 
 facial paralysis, lead palsy, and in affections of the nerve cells in the anterior cornu of the gray 
 matter of the spinal cord.] In rare cases the contraction of the muscles, caused by applying a 
 Faradic current to the nerve, follows a slow peristaltic-like course — "Faradic reaction of degenera- 
 tion" (£. Remak, Kast, Erb). 
 
 II. In Various Forms of Spasm (spasms, contracture, muscular tremor) the constant current 
 is most effective (Remak). By the action of anelectrotonus, a pathological increase of the excita- 
 bility is subdued. Hence, the anode ought to be applied to the part with increased excitability, and 
 if it be a case of reflex spasm, to the points which are the origin or seat of the increased excitability. 
 Weak currents of uniform intensity are most effective. The constant current may also be useful 
 from its cataphoric action, whereby it favors the removal of stimuli from the seat of the irritation. 
 Further, the constant current increases the voluntary control over the affected muscles. In spasms 
 of central origin the constant current may be applied to the central organ itself (Fig. 387). Fara- 
 dization is used in spasmodic affections to increase the vigor of enfeebled antagonistic muscles. 
 Muscles in a condition of contracture are said to become more extensible under the influence of 
 the Faradic current {Remak), as a normal' muscle is more excitable during active contraction 
 
 (§3°i)- 
 
 In cutaneous anaesthesia, the Faradic current applied to the skin by means of hair-brush 
 electrodes (Fig. 375) is frequently used. When using the constant current, the cathode must be 
 applied to the parts with diminished sensibility. The constant current alone is applied to the central 
 seat of the lesion, and care must be taken to what extent the occurrence of cathelectrotonus in the 
 centre affects the occurrence of sensation. 
 
 III. In Hyperesthesia and Neuralgias, Faradic currents are applied with the object of over- 
 stimulating the hypersensitive parts, and thus to benumb them. Besides these powerful currents, 
 weak currents act reflexly and accelerate the blood stream, increase the heart's action, and constrict 
 the blood vessels, while strong currents cause the opposite effects (O. Naumann). Both may be 
 useful. In employing the constant current in neuralgia [Remak), one object is by exciting anelec- 
 trotonus in the hypersensitive nerves, to cause a diminution of the excitability. According to the 
 nature of the case, the anode is placed either on the nerve trunk or even on the centre itself, and 
 the cathode on an indifferent part of the body. The catalytic and cataphoric effects also are most 
 important, for by means of them, especially in recent rheumatic neuralgias, the irritating inflamma- 
 tory products are distributed and conducted away from the part. A descending current is trans- 
 mitted continuously for a time through the nerve trunk, and in recent cases its effects are sometimes 
 very striking. Lastly, of course the constant current may be used as a cutaneous stimulus, while 
 the Faradic current also acts reflexly on the cardiac and vascular activity. 
 
 Recently, Charcot and Ballet have used the electric spark from an electrical machine in cases of 
 anaesthesia, facial paralysis and paralysis agitans. In some cases of spinal paralysis, muscles can 
 be made to contract with the electric spark, which do not contract to a Faradic current. [Elec- 
 tricity is sometimes used to distinguish real from feigned disease, or to distinguish death from a conr 
 dition of trance.] 
 
 Galvano Cautery. — The electrical current is used for thermal purposes, as in the galvano 
 cautery. 
 
 Galvano Puncture. — The electrolytic properties of electrical currents are employed to cause 
 coagulation in aneurisms or varix. [If the electrodes from a constant battery in action be inserted 
 in an aneurismal sac, after a time the fibrin of the blood is deposited in the sac, whereby the cavity 
 of the aneurism is gradually filled up. A galvanic current passed through defibrinated blood causes 
 the formation of a coagulum of proteid matter at the positive pole and bubbles of gas at the 
 negative.] 
 
 340. ELECTRICAL CHARGING OF THE BODY. — Saussure investigated by means 
 of the electroscope the " charge " of a person standing on an insulated stool. The phenomena 
 observed by him, which were always inconstant, were due to the friction of the clothes upon the 
 skin. Gardini, Hemmer, Ahrens (1817), and Nasse regarded the b6dy as normally charged with 
 positive electricity, while Sjosten and others regarded it as negatively charged. Most probably all 
 these phenomena are due to friction, and are modified effects of the air in contact with the hetero- 
 geneous clothing (Hankel). A strong charge resulting in an actual spark has frequently been 
 described. Cardanus (1553) obtained sparks from the tips of the hair of the head. According to 
 Horsford (1837), long sparks were obtained from the tips of the fingers of a nervous woman in 
 Oxford, when she stood upon an insulated carpet. Sparks have often been observed on combing 
 the hair or stroking the back of a cat in the dark. Freshly-voided urine is negatively electrical 
 ( Vasalli- Eandi, Volta) ; so is the freshly- formed web of a spider, while the blood is positive. 
 
 341. COMPARATIVE— HISTORICAL.— Electrical Fishes.— Some of the most inter- 
 esting phenomena connected with animal electricity are obtained in electrical fishes, of which there 
 are about fifty species, including the electrical eel, oiGymnotus electricus, of the lagoons of the region 
 
612 COMPARATIVE — HISTORICAL. 
 
 of the Orinoco in South America ; it may measure over 7 feet in length. The Torpedo marmorala 
 and some allied species, 30 to 70 centimetres [1 to 2^ feet], in the Adriatic and Mediterranean, 
 the Malapterurus electricus of the Nile, and the Marmyrus, also of the same river. By means of 
 special electrical organs (Redi, 1666), these animals can in part voluntarily (gymnotus and malap- 
 terurus), and in part reflexly (torpedo) give a very powerful electrical shock. The electrical organ 
 consists of " compartments " of various forms, separated from each other by connective tissue, and 
 filled with a jelly-like substance, which the nerves enter on one surface and ramify to produce a 
 plexus. From this plexus there proceed branches of the axial cylinder, which end in a nucleated 
 plate, the " electrical plate " (Billharz, M. Schulze). When the " electrical nerves " proceeding to 
 the organ are stimulated, an electrical discharge is the result. 
 
 In Gymnotus the electrical organ consists of several rows of columns arranged along both sides 
 Of the spinal column of the animal, under the skin as far as the tail. It receives on the anterior 
 surface several branches from the intercostal nerves. Besides this large organ there is a smaller one 
 lying on both sides above the anal fins. Here the plates are vertical, and the direction of the elec- 
 trical current in the fish is ascending, so that, of course, it is descending in the surrounding water 
 (Faraday, Du Bois-Reymond). 
 
 In Malapterurus the organ surrounds the body like a mantle, and receives only one nerve fibre 
 (p. 521), whose axis cylinder arises near the medulla oblongata from one gigantic ganglionic cell 
 (Billharz), and is composed of protoplasmic processes (Fritsch). The plates are also vertical, and 
 receive their nerves from the posterior surface. The direction of the current is descending in the 
 fish during the discharge (Du Bois-Reymond). 
 
 In the Torpedo the organ lies immediately under the skin laterally on each side of the head, 
 reaching as far as the pectoral fins. It receives several nerves which arise from the lobus electricus, 
 between the corpora quadrigemina and the medulla oblongata. The plates, which do not increase 
 in number with the growth of the animal (Delle Chiaje, Babuchiri), lie horizontally, while the nerve 
 fibres enter them on their dorsal surfaces, the current in the fish being from the abdominal to the dorsal 
 surface ( Galvani). It is extremely probable that the electric organs are modified muscles, in which 
 the nerve terminations are highly developed, the electrical plates corresponding to the motorial end 
 plates of the muscular fibres, the contractile substance having disappeared, so that during physiological 
 activity the chemical energy is changed into electricity alone, while there is no " work " done. 
 This view is supported by the observation of Babuchin, that during development the organs are 
 originally formed like muscles; further, that the organs when at rest are neutral, but when active or 
 dead, acid; and lastly, they contain a substance related to myosin which coagulates after death 
 (? 2 9S — Weyl). The organs manifest fatigue ; they have a " latent period " of 0.016 second, while 
 one shock of the organ (comparable to the current in an active muscle) lasts 0.07 second. About 
 twenty-five of these shocks go to make a discharge, which lasts about 0.23 second. The discharge, 
 like tetanus, is a discontinuous process (Marey). Mechanical, chemical, thermal and electrical 
 stimuli cause a discharge; a single induction shock is not effective (Sachs). During the electrical 
 discharge the current traverses the muscles of the animal itself; the latter contract in the torpedo, 
 while they do not do so in the gymnotus and malapterurus during the discharge (Steiner). A tor- 
 pedo can give about fifty shocks per minute ; it then becomes fatigued, and requires some time to 
 recover itself. It may only partially discharge its organ (A I. v. Humboldt, Sachs). Cooling makes 
 the organ less active, while heating it to 22 C. makes it more so. The organ becomes tetanic with 
 strychnin (Becquerel), while curara paralyzes it (Sachs). Stimulation of the electrical organ of the 
 torpedo causes a discharge (Matteucci) ; cold retards it, while section of the electrical nerves 
 paralyzes the organ. The electrical fishes themselves are but slightly affected by very strong induc- 
 tion shocks transmitted through the water in which they are swimming (Du Bois-Reymond). The 
 substance of the electrical organs is singly refractive ; excised portions give a current during rest, 
 which has the same direction as the shock ; tetanus of the or^an weakens the current (Sachs, Du 
 Bois-Reymond ) . 
 
 Historical. — Richer (1672) made the first communication about the gymnotus. Walsh (1772) 
 made investigations on the torpedo, on its discharge, and its power of communicating a shock. J. 
 Davy magnetized particles of steel, caused a deflection of the magnetic needle, and obtained elec 
 trolysis with the electrical discharge. Becquerel, Brechet and Matteucci studied the direction of 
 the discharge. Al. v. Humboldt described the habits and actions of the gymnotus of South America. 
 Hausen (1743) and de Sauvages (1744) supposed that electricity was the active force in nerves. 
 The actual investigations into animal electricity began with G. Aloisio Galvani (1791), who 
 observed that frogs' legs connected with an electrical machine contracted, and also when they were 
 touched with two different metals. He believed that nerves and muscles generated electricity. 
 Alessandro Volta ascribed the second experiment to the electrical current produced by the contact 
 of dissimilar metals, and therefore outside the tissues of the frog. The contraction without metals 
 described by Galvani was confirmed by Alex. v. Humboldt (1798). Pfaff (1793) first observed the 
 effect of the direction of the current upon the contraction of a frog's leg obtained by stimulating its 
 nerve. Bunzen made a galvanic pile of frogs' legs. The whole subject entered on a new phase 
 with the construction of the galvanometer and since the introduction of the classical methods 
 devised by Du Bois-Reymond, i.e., from 1 843 onwards. 
 
Physiology ™ peripheral Nerves. 
 
 342. FUNCTIONAL CLASSIFICATION OF NERVE FIBRES. 
 
 — As nerve fibres, on being stimulated, are capable of conducting impulses in both 
 directions (§ 338), it is obvious that the physiological position of a nerve fibre 
 must depend essentially upon its relations to the peripheral end organ on the 
 one hand, and its central connection on the other. Thus, each nerve is dis- 
 tributed to a special area within which, under normal circumstances, in the intact 
 body, it performs its functions. 
 
 I. Centrifugal or Efferent Nerves. — Ca) Motor. — Those nerve fibres 
 whose peripheral end organ consists of a muscle, the central ends of the fibres 
 being connected with nerve cells : — 
 
 1. Motor fibres of striped muscle ($ 292 to 320). 
 
 2. Motor nerves of the heart (§ 57). 
 
 3. Motor nerves of smooth muscle, e.g., the intestine (§ 171). The vasomotor nerves are 
 specially treated of in § 371. 
 
 (b) Secretory .—Those nerve fibres whose peripheral end organ consists of a 
 secretory cell, the central ends of the fibres being connected with nerve cells. 
 
 Examples of secretory nerves are the secretory nerves for saliva (g 145) and those for sweating 
 (J 289, II). It is to be remembered, however, that these fibres not unfrequently lie in the same 
 sheath with other nerve fibres, so that stimulation of a nerve may give rise to several results, accord- 
 ing to the kind of nerve fibres present in the nerve. Thus, the secretory and vasomotor nerves of 
 glands may be excited simultaneously. 
 
 (c) Trophic. — The end organs of these nerve fibres lie in the tissues them- 
 selves, and are as yet unknown. These nerves are called trophic, because they 
 are supposed to govern or control the normal metabolism of the tissues. 
 
 Trophic Influence of Nerves. — The trophic functions of certain nerves are referred to as 
 under : On the influence of the trigeminus on the eye ; the mucous membrane of the mouth and 
 nose ; the face ((S 347) ; the influence of the vagus on the lungs (g 352) ; motor nerves on muscle 
 (§ 3°7) > certain central organs upon certain viscera (jl 379). 
 
 Section of certain nerves influences the growth of the bones. H. Nasse found that, after section 
 of their nerves, the bones showed an absolute diminution of all their individual constituents, while 
 there was an increase of fat. Section of the spermatic nerve is followed by degeneration of the 
 testicle (Nelaton, Obolensky). After extirpation of their secretory nerves, there is degeneration of 
 the submaxillary glands (p. 237). Section of the nerves of the cock's comb interferes with the 
 nutrition of that organ (Legros, Schiff). Section of the cervical sympathetic nerve in young growing 
 animals is followed by a more rapid growth of the ear upon that side {Bidder, Stirling, Strieker), 
 also of the hair on that side (Schiff, Stirling, Sig. Meyer) ; while it is said that the corresponding 
 half of the brain is smaller, which, perhaps, is due to the pressure from the dilated blood vessels 
 ( Brown- Siquard) . 
 
 Blood Vessels. — Lewaschew found that continued uninterrupted stimulation of the sciatic nerve 
 of dogs, by means of chemical stimuli [threads dipped in sulphuric acid], caused hypertrophy of 
 the lower limb and foot, together with the formation of aneurismal dilatations upon the blood 
 vessels. 
 
 Skin and Cutaneous Appendages. — In man, stimulation or paralysis of nerves, or degenera- 
 tion of the gray matter of the spinal cord (Jarisch), is not unfrequently followed by changes in the 
 pigmentation of the skin, in the nails, in the hair and its mode of growth and color. [Injury to the 
 brain, as by a fall, sometimes results in paralysis of the hair follicles, so that, after such an injury, 
 the hair is lost over nearly the whole of the body.] Sometimes there may be eruptions upon the skin 
 apparently traumatic in their origin (v. Barensprung, Leloir). Sometimes there is a tendency to 
 decubitus (§ 379), and in some rare cases of tabes there is a peculiar degeneration of the joints 
 
 613 
 
614 INHIBITORY NERVES. 
 
 (Charcot's disease). The changes which take place in a nerve separated from its centre are de- 
 scribed in | 325. 
 
 [Trophoneuroses. — Some of the chief data on which the existence of trophic nerves is assumed 
 are indicated above. There are many pathological conditions referable to diseases or injuries of 
 nerves.] 
 
 [Muscles. — As is well known, paralysis of a motor nerve leads to simple atrophy of the corres- 
 ponding muscle, provided it be not exercised; but when the motor ganglionic cells of the anterior 
 horn of the gray matter, or the corresponding cells in the crus, pons, and medulla, are paralyzed, 
 there is an active condition of atrophy with proliferation of the muscular nuclei Progressive 
 muscular atrophy, or wasting palsy, is another trophic change in muscle, whereby either individual 
 muscles or groups of muscles are one after the other paralyzed and become atrophied. In pseudo- 
 hypertrophic paralysis there is cirrhosis or increased development of the connective tissue, with 
 a diminution of the true muscular elements, so that although the muscles increase in bulk their 
 power is diminished.] 
 
 [Cutaneous Trophic Affections. — Among these may be mentioned the occurrence of red 
 patches or erythema, urticaria or nettle rash, some forms of lichen, eczema, the bulla; or blebs of 
 pemphigus, and some forms of ichthyosis, each of which may occur in limited areas after injury to 
 a nerve or its spinal or cerebral centre. The relation between the eruption and the distribution of 
 a nerve is sometimes very marked in herpes zoster, which frequently follows the distribution of 
 the intercostal and supraorbital nerves. Glossy skin [Paget, Weir Mitchell) is a condition de- 
 pending upon impaired nutrition and circulation, and due to injuries of nerves. The skin is smooth 
 and glossy in the area of distribution of certain nerves, while the wrinkles and folds have disap- 
 peared. In myxcedema, the subcutaneous tissue and other organs are infiltrated with, while the 
 blood contains mucin. The subcutaneous tissue is swollen and the patient (adult woman) looks as 
 if suffering from renal dropsy. There is marked alteration of the cerebral faculties, and a condi- 
 tion resembling a "cretinoid state," occurs after the excision of the thyroid gland. Victor Horsley 
 has shown that asimilar condition occurs in monkeys after excision of the thyroid gland ({j 103, 
 III).] 
 
 [Laycock described a condition of nervous oedema which occurs in some cases of hemiplegia, 
 and apparently it is independent of renal or cardiac disease.] 
 
 [There are alterations in the color of the skin depending on nervous affections, including local- 
 ized leucoderma, where circumscribed patches of the skin are devoid of pigment. The pigmenta- 
 tion of the skin in Addison's disease or bronzed skin, which occurs in some cases of disease of 
 the suprarenal capsules, may be partly nervous in its origin, more especially when we consider the 
 remarkable pigmentation that occurs around the nipple and some other parts of the body during 
 pregnancy, and in some uterine and ovarian affections (Laycock).~\ 
 
 [In anaesthetic leprosy, the anaesthesia is due to the disease of the nervous structure, which 
 results in disturbances of motion and nutrition. Among other remarkable changes in the skin, 
 perhaps due to trophic conditions, are those of symmetrical and local gangrene, and acute decu- 
 bitus or bed sores.] 
 
 [Bed sores.— Besides the simple chronic form, which results from over- pressure, bad nursing, 
 and inattention to cleanliness, combined with some defect of the nervous conditions, there is 
 another form, acute decubitus, which is due directly to nerve influence (Charcot'). The latter 
 usually appears within a few hours or days of the cerebral or spinal lesion, and the whole cycle of 
 changes — from the appearance of erythematous dusky patch to inflammation, ulceration, and gan- 
 grene of the buttock — are completed in a few days. An acute bed sore may form when every at- 
 tention is paid to the avoidance of pressure and other unfavorable conditions. When it depends on 
 cerebral affections it begins and develops rapidly in the centre of the gluteal region on the paralyzed 
 side, but when it is due to disease of the spinal cord, it forms more in the middle line in the sacral 
 region ; while in unilateral spinal lesions it occurs not on the paralyzed, but on the anaesthetic side, 
 a fact which seems to show that the trophic, like the sensory fibres, decuss-ate in the cord (Ross).~\ 
 
 [There are other forms due to nervous disease, including symmetrical gangrene and local 
 asphyxia of the terminal parts of the body, such as the toes, nose, and external ear, caused, perhaps, 
 by spasm of the small arterioles (Raynaud's disease) ; and the still more curious condition of 
 perforating ulcer of the foot.] 
 
 [Hemorrhage of nervous origin sometimes occurs in the skin, including those that occur in loco- 
 motor ataxia after severe attacks of pain, and hematoma aurium, or the insane ear, which is 
 specially common in general paralytics.] 
 
 (d) Inhibitory nerves are those nerves which modify, inhibit, or suppress a 
 motor or secretory act already in progress. 
 
 Take as an example the effect of the vagus upon the action of the heart. Stimulation of the 
 peripheral end of the vagus causes the heart to stand still in diastole (§ 85) ; the effect of the 
 splanchnic upon the intestinal movements (\ 161). The vaso-dilator nerves, or those whose stimu- 
 lation is followed by dilatation of the blood vessels of the area which they supply, are referred to 
 specially in \ 237. 
 
 [There is the greatest uncertainty as to the nature and mode of action of inhibitory nerves, 
 
THE CRANIAL NERVES. 615 
 
 but take the vagus as a type, which depresses the function of the heart, as shown by the slower 
 rhythm, diminution of the contractions, relaxation of the muscular tissue, lowering of the excitability 
 and conduction. These phenomena are not due to exhaustion. Gaskell points out that the action 
 is beneficial in its after effects, so that this nerve, although it causes diminished activity, is followed 
 by repair of function, so that he groups it as an anabolic nerve, the outward symptoms of cessation 
 of function indicating that constructive chemical changes are going on in the tissue.] 
 
 (e) Thermic and electrical nerves have also been surmised to exist. 
 
 [Gaskell classifies the efferent nerves differently. Besides motor nerves to striped muscle, he 
 groups them as follows : — 
 
 1. Nerves to vascular muscles. 
 
 (a) Vaso-motor, i. e., vaso-constrictor, accelerators and augmentors of the heart. 
 
 (b) Vaso-inhibitory, i. e., vaso-dilators and inhibitors of the heart. 
 
 2. Nerves of the visceral muscles. 
 
 (a) Viscera motor. 
 
 (b) Viscero inhibitory. 
 
 3. Glandular nerves.] 
 
 [Other terms are applied to nerves with reference to the chemical changes they excite in a tis- 
 sue in which they terminate. The ordinary metabolism is the resultant of two processes, one con- 
 structive the other destructive, or of assimilation and dissimilation respectively. The former process 
 is anabolism, the latter katabolism. A motor nerve excites chemical destructive changes in a mus- 
 cle, and is so far the katabolic nerve of that tissue ; in the same way the sympathetic to the heart, 
 by causing more rapid contraction, is also a katabolic nerve, while the vagus, as it arrests the heart's 
 action, brings about a constructive metabolism of the cardiac tissue, is an anabolic nerve 
 {Gasiill).'] 
 
 II. Centripetal or Afferent Nerves. — (a) Sensory Nerves (sensory in 
 the narrower sense), which by means of special end organs conduct sensory 
 impulses to the central nervous system. 
 
 (b) Nerves of Special Sense. Fig. 380. 
 
 (c) Reflex or Excito-motor Nerves. — 
 When the periphery of one of these nerves is stim- 
 ulated, an impulse is set up which is conducted 
 by them to a nerve centre, from whence it is trans- 
 ferred to a centrifugal or efferent fibre, and the 
 mechanism (I, a, b, c, d) in connection with the 
 peripheral end of this efferent fibre is set in action ; 
 thus there are — Reflex motor, Reflex secre- 
 tory, and Reflex inhibitory fibres. [Fig. 380 
 shows the simplest mechanism necessary for a reflex 
 
 motor act. The impulse Starts from the skin, S, Scheme of a reflex motor act. S,skin; 
 
 travels up the nerve a,/, to the nerve centre or effeVmTbre. ne " e ; N - nerve cdl ; '■/• 
 nerve cell, N, situate in the spinal cord, where it 
 
 is modified and transferred to the outgoing fibre, e, f, and conveyed by it to the 
 muscle, M.] 
 
 III. Intercentral Nerves. — These fibres serve to connect ganglionic centres 
 with each other, as, for example, in coordinated movements, and in extensive 
 reflex acts. 
 
 THE CRANIAL NERVES.— 343. I. NERVUS OLFACTORIUS.— Anatomical.— 
 The three-sided, prismatic, tractus olfactorius' lying in a groove on the under surface of the frontal 
 lobe, arises by means of an inner, outer, and upper root, from the tuber olfactorium (Fig. 385, 1). 
 The tractus swells out upon the cribriform plate of the ethmoid bone, and becomes the bulbus 
 olfactorius, which is the analogue of the special portion of the brain, existing in different mammals 
 with a well-developed sense of smell [Gratiolet). From twelve to fifteen olfactory filaments pass 
 through the foramina in the cribriform plate of the ethmoid bone. At first they lie between the peri- 
 osteum and the mucous membrane, but in the lower third of their course they enter the mucous 
 membrane of the regio olfactoria. The bulb consists of white matter below, and above of gray 
 matter mixed with small spindle-shaped ganglionic cells. Henle describes six, and Meynert eight 
 layers of nervous matter seen on transverse section. [The centre for smell lies in the tip of the 
 uncinate gyrus on the inner surface of the cerebral hemisphere (Ferrier). According to Hill, the 
 three roots of the olfactory bulb stream backward, the inner one is small, the middle one is a thick 
 bundle, which grooves the head of the caudate nucleus, curves inward to the anterior commissure, 
 
616 CONNECTIONS OF OPTIC TRACT. 
 
 and crosses via this commissure where it decussates, and passes to the extremity of the temporo- 
 sphenoidal lobe. The outer roots pass transversely into the pyriform lobe, thence via the fornix, 
 corpora albicantia, the bundle of Vicq d'Azyr into the anterior end of the optic thalamus. Hill 
 also points out that the elements contained in the olfactory bulb are identical with those contained 
 in the four outer layers of the retina.] 
 
 Function. — It is the only nerve of smell. Physiologically, it is excited only 
 by gaseous odorous bodies — (Sense of Smell, § 420). Stimulation of the nerve, 
 by any other form of stimulus, in any part of its course, causes a sensation of 
 smell. [It also conveys those impressions which we call flavors, but in this case 
 the sensation is combined with impressions from the organs of taste. In this case 
 the stimulus reaches the nerve by the posterior nares.] Congenital absence or 
 section of both olfactory nerves abolishes the sense of smell (easily performed 
 on young animals. — Biffi). 
 
 Pathological. — The term Hyperosmia is applied to cases where the sense of smell is exces- 
 sively and abnormally acute, as in some hysterical persons, and in cases where there is a purely sub- 
 jective sense of smell, as in some insane persons. The latter is, perhaps, due to an abnormal stim- 
 ulation of the cortical centre ($ 378, IV). Hyposmia and Anosmia (;'. e., diminution and abo- 
 lition of the sense of smell) may be due to mechanical causes, or to over-stimulation. Strychnin 
 sometimes increases, while morphia diminishes, the sense of smell. [Method of Testing, \ 421.] 
 
 344. II. NERVUS OPTICUS.— Anatomical. — The tractus opticus (Fig. 385, II) arises 
 by a number of fibres from the inner gray substance of the thalamus opticus, and the anterior cor- 
 pora quadrigemina ; other fibres cover these structures in the form of a thin plate of nervous matter. 
 The corpora geniculata (Fig. 385, i, e), form ganglia, intercalated, as it were, in the course of cer- 
 tain of the fibres. Another set of fibres, quite distinct from the foregoing, passes between the bun- 
 dles of the crus cerebri, and reaches the multicellular nucleus within the tegmentum of the crus 
 (corpus subthalamicum). Other fibres are said to pass to the spinal cord, directly through the med- 
 ulla oblongata, without the intervention of any gray matter. They are said by Stilling to reach as 
 far as the decussation of the pyramids. According to this view, the optic nerve has a spinal root, 
 which explains the relation of stimulation of the retina to the dilator of the iris. A broad bundle 
 of fibres passes from the origin of the optic tract to the cortical psycho-optic centre, at the apex 
 of the occipital lobe ( Wernicke — \ 379, IV). 
 
 The Optic Tract bends- round the pedunculus cerebri, where it unites with its fellow of the oppo- 
 site side to form the chiasma. 
 
 [Connections of Optic Tract. — There is very considerable difficulty in ascertaining the exact 
 origin of all the fibres of the optic tract. Although as yet the statement of Gratiolet is not proved, 
 that the optic tract is directly connected with every part of the cerebral hemisphere in man, from 
 the frontal to the occipital lobe, still, the researches of D. J. Hamilton have shown that its connec- 
 tions are very extensive. It is certain that some of them are ganglionic, i.e., connected with the 
 ganglia at the base of the brain, while others are cortical, and form connections with the cortex 
 cerebri. The ganglionic fibres arise from the corpora geniculata, pulvinar and anterior corpora 
 quadrigemina, and probably, also, from the substance of the .thalamus. The cortical fibres join 
 the ganglionic to form the optic tract. According to D. J. Hamilton, the connection with the cortex 
 in the frontal region is brought about by " Meynert's commissure." The latter arises directly from 
 the lenticular-nucleus loop, decussates in the lamina cinerea, and passes into the optic nerve of the 
 opposite side. The lenticular-nucleus loop is fonned below the lenticular nucleus by the junction 
 of the stria? medullares ; the striae, medullares form part of the fibres of the internal capsule, and the 
 inner capsule is largely composed of fibres descending from the cortex. Hamilton also asserts that 
 other cortical connections join the tract as it winds round the pedunculus cerebri, and they include 
 [a) a large mass of fibres coming from the motor areas of the opposite cerebral hemisphere, crossing 
 in the corpus callosum, entering the outer capsule, and joining the tract directly ; (b) fibres uniting 
 it to the temporo-sphenoidal lobe of the same side, especially the first and second temporo-sphenoidal 
 convolutions ; (c) fibres to the gyrus hippocampi of the same side ; (d) a large leash of fibres 
 forming the "optic radiation" of Gratiolet, which connect it directly with the tip of the occipital 
 lobe. There are probably also indirect connections with the occipital region through some of 
 the basal ganglia. Although some observers do not admit the connections with the frontal 
 and sphenoidal lobes, all are agreed as to its connection with the occipital by means of the 
 " optic radiation."] 
 
 [The Optic Radiation of Gratiolet is a wide strand of fibres expanding and terminating in the 
 occipital lobes. It is composed of, or, stated otherwise, gives branches to (a) the optic tract directly, 
 (A) the corpus geniculatum internum and externum, (c) to the pulvinar and substance of the thal- 
 amus, (d) a direct sensitive band (Meynert's "sensitive band") to the posterior third of the poste- 
 rior limb of the inner capsule, (e) fibres which run between the island of Reil and the tip of the 
 occipital lobe {D. J. Hamilton).^ 
 
HEMIOPIA AND HEMIANOPSIA 617 
 
 Chiasma. — The extent of the decussation of the optic fibres in the chiasma 
 is subject to variations. As a rule, rather more 
 than half of the fibres of one tract cross to the Fig. 381. 
 
 optic nerve of the opposite side (Fig. 381), so 
 that the left optic tract sends fibres to the left 
 half of both eyes, while the right tract supplies 
 the right half of both eyes (§ 378, IV). [Thus, 
 the corresponding regions of each retina are 
 brought into relation with one hemisphere. The 
 fibres which cross are from the nasal half of each 
 retina.] 
 
 Hence, in man, the destruction of one optic tract (and 
 its central continuation in the occipital lobe of the cere- 
 brum) produces " equilateral or homonymous hemi- Scheme of the semidecussation of the optic 
 opia." In the dog and cat there is a semi-decussation ; nerves. L A., left eye; R. A., right eye. 
 
 hence, in these animals extirpation of one eyeball causes 
 
 atrophy and degeneration of half of the nerve fibres in both optic tracts (Gudden). Baumgarten 
 and Mohr have observed a similar result in man. A sagittal section of the chiasma in the cat pro- 
 duces partial blindness of both eyes {Nicati). According to Gudden, the fibres which decussate 
 are more numerous than those which do not, although J. Stilling maintains that they are only slightly 
 more numerous. According to J. Schilling, the decussating fibres lie in the central axis of the 
 nerve, while those which do not decussate form a layer around the former. 
 
 Other observers maintain that there is complete decussation of all the fibres in the chiasma. 
 Hence, section of one optic nerve causes dilatation of the pupil and blindness on the same side, while 
 section of one optic tract causes dilatation of the pupil and blindness of the opposite eye {Knoll, 
 Brown- Siguard, Mandelstamm). In osseous fishes, both optic nerves are isolated and merely cross 
 over each other, while in the cyclostomata they do not cross at all. [Total decussation occurs in 
 those animals where the eyes do not act together.] 
 
 Injury of the external geniculate body and section of the anterior brachium have the same effect 
 as section of the optic tract of the same side (J 359 — Bechterew). 
 
 In very rare cases the decussation is absent in man, so that the right tract passes directly into the 
 right eyeball, and the left into the left eyeball ( Vesalius, Caldani, Losel), the sight not being inter- 
 fered with ( Vesalius). 
 
 It is quite certain that the individual fibres do not divide in the chiasma. Two commissures, the 
 inferior commissure (Gudden) and Meynert's commissure, unite both optic tracts further back. 
 
 [A special commissure (C. inferior) extends in a curved form across the posterior angle of the 
 chiasma (Gudden). It does not degenerate after enucleation of the eyeballs, so that it is regarded 
 as an intercentral connection. After excision of an eye, there is central degeneration of the fibres 
 of the optic nerve entering the eyeball ( Gudden), and in man about the half of the fibres in the 
 corresponding optic tract (Baumgarten, Mohr). After section of both optic nerves, or enucleation 
 of both eyeballs, there is a degeneration, proceeding centrally, of the whole optic tract. The 
 degeneration extends to the origins in the corpora quadrigemina, corpora geniculata, and pulvinar, 
 but not into the conducting paths leading to the cortical visual centre (v. Monakow) (\ 378, 
 IV, I).] 
 
 Hemiopia and Hemianopsia. — When one optic tract is interfered with or divided, there is 
 interference with or loss of sight in the lateral halves of both retinae, the blind part being separated 
 from the other half of the field of vision by a vertical line. When it is spoken of as paralysis of 
 one-half of the retina, the term hemiopia is applied to it; when with reference to the field of vision, 
 the term hemianopsia is used (see Eye). Suppose the left optic tract to be divided or pressed upon 
 by a tumor at K (Fig. 382), then the outer half of the left and the inner half of the right eye are 
 blind, causing right lateral hemianopsia, i. e., the two halves are affected which correspond in ordi- 
 nary vision, so that the condition is spoken of as homonymous hemianopsia. Suppose the lesion 
 to be at T (Fig. 382), then there is paralysis of the inner halves of both eyes, causing double tem- 
 poral hemianopsia. When there are two/Mesions at N M, which is very rare, the outer halves of 
 both retinae are paralyzed, so that there is double nasal hemianopsia. Tn order to explain some of 
 the eye symptoms that occasionally occur in cerebral disease, Charcot has supposed that some of the 
 fibres which pass from the external geniculate body to the visual centres in the occipital lobe cross 
 behind the corpora quadrigemina, and this is represented in the diagram as occurring at T Q, in 
 the corpora quadrigemina. On this view, all the occipital cortical fibres from one eye would ulti- 
 mately pass to the cortex of the occipital lobe of the opposite hemisphere. This view, however, by 
 no means explains all the facts, for in cases of homonymous hemianopsia the point of central vision 
 on both sides, i. e., both maculae luteae are always unaffected ; so that it is assumed that each macula 
 lutea is connected with both hemispheres. The second crossing suggested by Charcot probably does 
 not occur. [Affections of the optic nerve, i. e., between the eyeball and the chiasma, i. e., in the 
 
618 
 
 NERVUS OCULOMOTORIUS. 
 
 orbit, optic foramen, or within the skull, affect one eye only; of the middle of the chiasma, cause 
 temporal hemiopia ; of the optic tract, between the chiasma and occipital cortex, hemiopia, which 
 is always symmetrical (Gowers)^\ 
 
 Munk supposes that there are three areas in the retina corresponding to three cortical visual spheres, 
 or parts of the visual centre in the occipital lobe (dog) ({I 376). 
 
 Function. — The optic nerve is 
 Fig. 382. 
 
 
 the nerve of sight ; physiologically, it is 
 excited only by the transference of the 
 vibrations of the ether to the rods and 
 cones of the retina (§ 383). Every other 
 form of stimulus, when applied to the 
 nerve in its course or at its centre, causes 
 the sensation of light. Section or degen- 
 eration of the nerve is followed by blind- 
 ness. Stimulation of the optic nerve 
 causes a reflex contraction of the pupils, 
 the efferent nerve being the oculomotorius 
 or third cranial nerve. If the stimulus be 
 very strong, the eyelids are closed and 
 there is a secretion of tears. The influ- 
 ence of light upon the general metabolism 
 is stated at § 127, 9. 
 
 As the optic nerve has special and 
 independent connections with the so-called 
 psycho-optic centre (§ 378, IV), as well as 
 with the centre for narrowing the pupil 
 (§ 345), it is evident that, under patho- 
 logical circumstances, there may be, 
 on the one hand, blindness with retention 
 of the action of the iris, and on the other 
 loss of the movements of the iris, the 
 sense of vision being retained {Wernicke). 
 
 Pathological. — Stimulation of almost the whole 
 of the nervous apparatus may cause excessive sen- 
 sibility of the visual apparatus {hypemsthefia 
 optica), or even visual impressions of the most varied kinds (photopsia, chromatopsia), which 
 in cases of stimulation of the psycho-optic centre may become actual visual hallucinations ({} 378. 
 IT). Material change in, and inflammation of, the nervous apparatus are often followed by a 
 nervous weakness of vision (amblyopia), or even by blindness (amaurosis). Both conditions, 
 however, may be the signs of disturbances of other organs, i.e., they are " sympathetic " signs, due, 
 it may be to changes in the movement of the blood stream, depending upon stimulation of the vaso- 
 motor nerves. The discovery of the partial origin of the optic nerve from the spinal cord explains 
 the occurrence of amblyopia (with partial atrophy of the optic nerve) in disease of the spinal cord, 
 especially in tabes. Many poisons, such as lead and alcohol, disturb vision. Hemeralopia and 
 Nyctalopia. — There are remarkable intermittent forms of amaurosis known as day blindness 
 (hemeralopia), which occurs in some diseases of the liver [and is sometimes associated with 
 incipient cataract. The person can see better in a dim light than during the day or in a bright 
 light. In night bindness (nyctalopia), the person cannot see at night or in a dim light, while 
 vision is good during the day or in a bright light. It depends upon disorder of the eye itself, and 
 is usually associated with imperfect conditions of nutrition. 
 
 345. III. NERVUS OCULOMOTORIUS.— Anatomical.— It springs from the oculo- 
 motorius nucleus (united with that of the trochlearis), which is a direct continuation of the anterior 
 horn of the spinal cord, and lies under the aqueduct of Sylvius (Fig. 385). £The motor nucleus 
 (Fig. 384) gives origin to three sets of fibres, for (1) the most of the muscles of the eyeballs. (2) 
 the sphincter papillse, (3) ciliary muscle. The nucleus of the 3d and 4th nerves is also connected 
 with that of the 6th under the iter, so that all the nerves to the ocular muscles are thus corelated at 
 their centres.] 
 
 The origin is connected with the corpora quadrigemina, to which the intraocular fibres may be 
 traced, and also with the lenticular nucleus through the pedunculus cerebri. Beyond the pons it 
 appears on the inner side of the cerebral peduncle between the superior cerebellar and posterior 
 cerebral arteries (Fig. 385, III). 
 
 j^uQC) cg 
 
 Diagram of the decussation of the optic tracts. T, 
 semi-decussation in the chiasma; TQ, decussa- 
 tion of fibres behind the ext. geniculate bodies 
 (CQ) ; a'b, fibres which do not decussate in the 
 chiasma; 6' a f t fibres "proceeding from the right 
 eye. and coming together in the left hemisphere 
 (LOG) ; LOG, K, lesion of the left optic tract 
 producing right lateral hemianopsia ; A, lesion in 
 the left hemisphere producing crossed amblyopia 
 (right eye) ; T, lesion producing temporal he- 
 mianopsia ; NN, lesion producing nasal hemian- 
 opsia. 
 
FUNCTIONS OF THE THIRD CRANIAL NERVE. 619 
 
 Function. — It contains — (i) the voluntary motor fibres for all the external 
 muscles of the eyeballs — except the external rectus and superior oblique — and for 
 the levator palpebrae superioris. The coordination of the movements of both 
 eyeballs, however, is independent of the will. (2) The fibres for the sphincter 
 pupillm, which are excited reflexly from the retina. (3) The voluntary fibres for 
 the muscle of accommodation, the tensor choroideae or ciliary muscle. The intra- 
 bulbar fibres of 2 and 3 proceed from the branch for the inferior oblique muscle, 
 as the short root of the ciliary ganglion (Fig. 386). They reach the eyeball 
 through the short ciliary nerves of the ganglion. V. Trautvetter, Adamiik, Hen- 
 sen and Volckers observed that stimulation of the nerve caused changes in the 
 eye similar to those which accompany near vision. The three centres for the 
 muscle of accommodation, the sphincter pupillse and the internal rectus muscle, 
 lie directly in relation with each other, in the most posterior part of the floor of 
 the third ventricle (Hensen and Volckers). 
 
 The centre for the reflex stimulation of the sphincter fibres by light is said to 
 be in the corpora quadrigemina, but newer researches locate it in the medulla 
 oblongata (§§ 379, 392). The narrowing of the pupil, which accompanies the 
 act of accommodation for a near object, is to be regarded as an associated move- 
 ment (§ 392, 5). 
 
 Anastomoses. — In man the nerve anastomoses on the sinus cavemosus with the ophthalmic 
 branch of the trigeminus, whereby it receives sensory fibres for the muscles to which it is distributed 
 ( Valentin, Adamiik), with the sympathetic through the carotid plexus, and (?) indirectly through 
 the abducens, whereby it receives vasomotor fibres (?). 
 
 Fig. 383. 
 
 t)Q)©d 
 
 Internal 
 
 External 
 
 Superior 
 
 Inferior 
 
 Inferior 
 
 Superior 
 
 rectus. 
 
 rectus. 
 
 rectus. 
 
 oblique. 
 
 rectus. 
 
 oblique. 
 
 Varieties. — In some rare cases the papillary fibres for the sphincter run in the abducens 
 {Adamiik), or even in the trigeminus [Schtff, v. Grd/e). 
 
 Atropin paral z?s the intrabulbar fibres of the oculomotorius, while Calabar 
 bean stimulates them (or paralyzes the sympathetic, or both — compare § 392). 
 
 Stimulation of the nerve which causes contraction of the pupil, is best demonstrated on the decapi- 
 tated and opened head of a bird. The pupil is dilated in paralysis of the oculomotorius, in asphyxia, 
 sudden cerebral anaemia (e. g., by ligature of the carotids, or beheading), sudden venous conges- 
 tion, and at death. 
 
 Pathological. — Complete paralysis of the oculomotorius is followed by — (1) drooping of the 
 upper eyelid (Ptosis paralytica); (2) immobility of the eyeball; (3) squinting (strabismus) out- 
 ward and downward, and consequently there is double vision (diplopia) ; (4) slight protrusion of 
 the eyeball, because the action of the superior oblique muscle in pulling the eyeball forward is no 
 longer compensated by the action of three paralyzed recti muscles. In animals provided with a re- 
 tractor bulbi muscle, the protrusion of the eyeball is more pronounced ; (5) moderate dilatation of 
 the pupil (mydriasis paralytica) ; (6) the pupil does not contract to light; (7) inability to ac- 
 commodate for a near object. It is to be noted, however, that the paralysis may be confined to 
 individual branches of the nerve, i. e. , there may be incomplete paralysis. 
 
 [Squinting. — In paralysis of the Superior Rectus the eye cannot be moved upward, and 
 especially upward and outward. There is diplopia on looking upward, the false image being above 
 
 the true, and turned to the right when the left eye is affected (Fig. 383, 3). Inferior Rectus 
 
 Defect of downward, and especially downward and outward movement, the eye being directed up- 
 ward and outward. Diplopia with crossed images, the false one is below the true image and placed 
 obliquely, being turned to the left when the left eye is affected. Diplopia is most troublesome when 
 the object is below the line of vision (Fig. 383, 5). Internal Rectus. — Defective inward move- 
 ment, divergent squint, and diplopia, the images being on the same plane, the false one to the 
 patient's right when the left eye is affected. The head is turned to the healthy side when looking 
 
620 
 
 FUNCTIONS OF THE FOURTH CRANIAL NERVE. 
 
 at an object, while there is secondary deviation of the healthy eye outward (Fig. 383, 1). Inferior 
 oblique is rare, the eye is turned slightly downward and inward, and defective movement upward. 
 Diplopia with the false image above the true one, especially on looking upward ; the false image is 
 oblique, and directed to the patient's left when the left eye is affected (Fig. 383, 4).] 
 
 The black cross represents the true image, the thin cross the false image. The left eye is affected 1 
 in all cases {Bristow). 
 
 Stimulation of the branch supplying the levator palpebral in man causes lagophthalmus spas- 
 ticus, while stimulation of the other motor fibres causes a corresponding strabismus spasticus. 
 This latter form of squinting may be caused also reflexly— e. g., in teething, or in cases of diarrhoea 
 
 Fig. 384. 
 
 Conarfum or pineal ffl.-.nd. 
 
 Brachlum conjunetlvum anticum. 
 
 F.raehinm cocjunctivunj 
 poaticum. 
 
 Corpus fanticum 
 quadri- -' 
 
 Locus coer ulcus 
 
 Eminentia teres 
 
 (■run cerebolll 
 ad pontem 
 
 liildte cerebellar 
 lieduncli*. 
 
 Corpus genlculatnm 
 ineduUe- 
 
 Pedunculut cerebri. 
 
 ad corpora quadrl- 
 
 pe in in a, or 
 
 ■ superior cerebellar 
 
 peduncle. 
 
 ad medullam oblon- 
 
 fat.ini, or Inferior 
 cerebellar 
 peduncle. 
 
 cerebellL 
 
 Ala ciueretv 
 
 Accessor! us nucleus 
 
 Obex 
 
 Clavu 
 
 Funiculus cnnentus 
 (I'artof restiform body). 
 
 Funiculus gr.icl'U 
 (Posterior pyramid). 
 
 Medulla oblongata., with the corpora quadrigemina. The numbers IV. — XII. indicate the superficial origins of the 
 cranial nerves, while those (3-12) indicate their deep origin, i. e., the position of their central nuclei ; t, funiculus 
 teres. 
 
 in children ; [the presence of worms or other source of irritation in the intestines of children is a 
 frequent cause of squinting.] Clonic spasms occur in both eyes, and also as involuntary movements 
 of the eyeballs constituting nystagmus, which may be produced by stimulation of the corpora 
 quadrigemina, as well as by other means. Tonic contraction of the sphincter pupillae is called 
 myosis spastica, and clonic contraction, hippus. Spasm of the muscle of accommodation (ciliary 
 muscle) is sometimes observed; owing to the imperfect judgment of distance, this condition is not 
 unfrequently associated with macropia. 
 
 [Conjugate Deviation. — Some movements are produced by non corresponding muscles ; thus, 
 on looking to the right, we use the right external rectus and left internal rectus, and the same is the 
 
THE OPHTHALMIC BRANCH OF THE FIFTH. 621 
 
 case in turning the head to the right e.g., the inferior oblique, some muscles of the right side act 
 along with the left sterno-mastoid. In hemiplegia the muscles on one side are paralyzed, so that 
 the head and often the eyes are turned away from the paralyzed side, i. e., to the side of the brain 
 on which the lesion occurs. This is called " conjugate deviation " of the eyes, with rotation of the 
 head and neck. If the right external rectus be paralyzed from an affection of the sixth nerve, on 
 telling the patient to look to the right it will be found that the left eye will squint more inward even 
 than the right eye, i. e., owing to the strong voluntary effort of the muscle, the left internal rectus 
 which usually acts along with the right external rectus, contracts vigorously, and so we get second- 
 ary deviation of the sound eye. Similar results occur in connection with paralysis of other 
 ocular muscles.] 
 
 346. IV. NERVUS TROCHLEARIS.— Anatomical.— It arises [from the valve of Vieus- 
 sens, i. e., behind the fourth ventricle], but its fibres pass to the oculomotorius from the trochlearis 
 nucleus (Fig. 384), which is to a certain extent a continuation of the anterior horn of the spinal 
 cord. It passes to the lower margin of the corpora quadrigemina, pierces the root of the aqueduct 
 of Sylvius, then into the velum medullare superius, and after decussating with the root of the 
 opposite side behind the iter, it pierces the crus at the supeiior and external border (Fig. 385, IV). 
 Its fibres cross between its nucleus and its distribution. It has also an origin from the locus cceru- 
 leus. The root of the nerve rectives some fibres from the nucleus of the abducens of the opposite 
 side. Physiologically, there is a necessity for a conjunction between the centre and the cortical 
 motor centre for the eye muscles. 
 
 Function. — It is the voluntary motor nerve of the superior oblique muscle. 
 (In coordinated movements, however, it is involuntary.) 
 
 Anastomoses. — Its connections with the plexus caroticus sympathici, and with the first branch 
 of the trigeminus, have the same significance as similar branches of the oculomotorius. 
 
 Pathological. — Paralysis of the trochlearis nerve causes a very slight loss of the mobility of the 
 eyeball outward and downward. There is slight squinting inward and upward, with diplopia or 
 double vision. The images are placed obliquely over each other [the false image being the lower, and 
 directed to the patient's right when the left eye is affected (Fig. 383, 6)] ; they approach each other 
 when the head is turned toward the sound side, and are separated when the head is turned toward 
 the other side. The patient at first directs his head forward, later he rotates it round a vertical axis 
 toward the sound side. In rotating his head (whereby the sound eye may retain the primary posi- 
 tion), the eye rotates with it. Spasm of the trochlearis causes squinting outward and downward. 
 
 347. V. NERVUS TRIGEMINUS.— Anatomical.— The trigeminus (Fig. 386, 5), arises 
 like a spinal nerve by two roots (Fig. 385, V). The smaller, anterior, motor root proceeds from 
 the " motor trigeminal nucleus " (5), which is provided with many multipolar nerve cells, and 
 lies in the floor of the medulla oblongata, not far from the middle line. Fibres connect this nucleus 
 with the cortical motor centres on the opposite side of the cerebrum. Besides this the " descend- 
 ing root " also supplies motor fibres. It extends laterally from the corpora quadrigemina along 
 the aqueduct of Sylvius downward to the exit of the nerve (Henle, Forel). The large posterior 
 sensory root receives fibres : (1) From the small cells of the " sensory trigeminal nucleus" 
 which lies at the level of the pons, and is the analogue of the posterior horn of the gray matter of 
 the spinal cord. (2) From the gray matter of the posterior horn of the spinal cord downward as 
 far as the cervical vertebra. These fibres run into the posterior column of the cord and then appear 
 as the " ascending root " in the trigeminus. (3) Some fibres come from the cerebellum, through 
 the crura cerebelli. The origins of the sensory root anastomose with the motor nuclei of all the 
 nerves arising from the medulla oblongata, with the exception of the abducens. This explains the 
 vast number of reflex relations of the fifth nerve. The thick trunk appears on each side of the 
 pons (Fig. 385), when its posterior root (perhaps in conjunction with some fibres from the anterior) 
 forms the Gasserian ganglion, upon the tip of the petrous part of the temporal bone (Fig. 386). 
 Fibres from the sympathetic proceed from the plexus cavernosus to the ganglion. The nerve 
 divides into three large branches. 
 
 I. The ophthalmic division (Fig. 386, d) receives sympathetic fibres (vaso- 
 motor nerves) from the plexus cavernosus ; it passes through the superior orbital 
 fissure [sphenoidal] into the orbit. Its branches are : — 
 
 1. The small recurrent nerve which gives sensory branches to the tentorium 
 cerebelli. Fibres proceed along with it trom the carotid plexus of the sympathetic, 
 which are the vasomotor nerves for the dura mater. 
 
 2. The lachrymal nerve gives off — (a) Sensory branches to the conjunctiva, 
 the upper eyelid, and the neighboring part of the skin over the temple (Fig. 386, 
 a) ; (6) true sensory fibres to the lachrymal gland (?). Stimulation of this 
 nerve is said to cause a secretion of tears, while its section prevents the reflex 
 secretion excited through the sensory nerves of the eye. After a time, section of 
 
622 
 
 THE OPHTHALMIC BRANCH OF THE FIFTH. 
 
 the nerve is followed by a paralytic secretion of tears (Herzenstein and Wolferz, 
 Demtschenko), although the statement is contested by Reich. The secretion of 
 tears may be excited reflexly by strong stimulation of the retina by light by 
 stimulation of the first and second branches of the trigeminus, and through all 
 the sensory cranial nerves {Demtschenko) (§ 356, A, 6). 
 3. The frontal (/) gives off the supratrochlear, which supplies sensory 
 
 F IG . 385. 
 
 d ,',a 
 
 Part of the base of the brain, with the origins of the cranial nerves ; the convolutions of the island of Reil on the 
 right side, but removed on the left. V, olfactory tract cut short; II, lelt optic nerve ; II', right optic tract ; 
 T, k, cut surface of the left optic thalamus ; C, central lobe, or island of Reil ; S, y, fissure of Sylvius ; X, X, 
 the locus perforatus anticus ; <?, the external, and i, the internal, corpus geniculatum ; A, hypophysis cerebri; 
 t, c, tuber cinereum, with the infundibulum ; a, points to one of the corpora albicantia; P, the cerebral pe- 
 duncle ;_/", the fillet; III, left oculo-motor nerve; X, the locus perforatus posticus; P, W f pons Varolii ; V, 
 the greater part of the fifth nerve ; +, the lesser root (on the right side this mark is placed on the Gasserian 
 ganglion and points to the lesser root) ; i, ophthalmic division of the fifth ; VII, a, facial ; VII, b, auditory ; 
 VIII, vagus ; VIII, a, glossopharyngeal ; VIII, i, spinal . accessory ; IX, hypoglossal ; ft, flocculus;/, k, 
 horizontal fissure of the cerebellum ( CV) ; a, m, amygdala; /, a, anterior pyramid; o, olivary body; e, resti- 
 form body; d f anterior median fissure ; c, I, the lateral column of the spinal cord; C, I, the sub-occipital or 
 first cervical nerve. 
 
 fibres to the upper eyelids, brow, glabelli, and those which excite the. secretion 
 of tears reflexly ; and by its supraorbital branch (J>), analogous branches to 
 the upper eyelid, skin of the forehead, arid the adjoining skin over the temple as 
 far as the vertex. 
 4. The nasociliary nerve (n, c), by its infratrochlear branch supplies fibres, 
 
CILIARY NERVES. 623 
 
 similar to those of 3, to the conjunctiva, caruncula and saccus lacrymalis, the 
 upper eyelid, brow and root of the nose. Its ethmoidal branch supplies the 
 tip and alee of the nose, outside and inside, with sensory branches, as well as the 
 upper part of the septum and the turbinated bones with sensory fibres, which 
 can act as afferent nerves in the reflex secretion of tears ; while it is probable that 
 vasomotor fibres are supplied to these parts through the same channel. (These 
 fibres may be derived from the anastomosis with the sympathetic (?).) The naso- 
 ciliary nerve gives off the long root (/) of the ciliary ganglion (<r), and 1 to 3 
 long ciliary nerves. 
 
 The ciliary ganglion (Fig. 386, c), which, according to Schwalbe, perhaps 
 belongs rather to the third than the fifth nerve, has three roots — (a) the short 
 or oculomotorius (3 — see § 345) ; (b) the long (/), from the nasociliary ; and (c) 
 the sympathetic (s), sometimes united with b, from the carotid plexus. The 
 short ciliary nerves (t), 6 to 10 in number, proceed from the ganglion, along 
 with the long ciliary nerves, to near the entrance of the optic nerve, where they 
 perforate the sclerotic coat and run forward between it and the choroid. 
 
 Ciliary Nerves. — Physiologically, these nerves contain : — 
 
 1. The motor fibres for the sphincter pupillae and tensor choroidese from 
 the root of the oculomotorius (§ 345, 2, 3). 
 
 2. Sensory fibres for the cornea which are distributed as excessively fine 
 fibrils between the epithelium of the conjunctiva bulbi ; they perforate the sclerotic 
 (Giraldes). These fibres cause a reflex secretion of tears (N. lacrymalis) and 
 closure of the eyelids (N. facialis). Sensory fibres are supplied to the iris (pain 
 in iritis and in operations on the iris), the choroid (painful tension when the 
 ciliary muscle is strained), and the sclerotic. 
 
 3. Vasomotor nerves for the blood vessels of the iris, choroid and retina. 
 They arise in part from the sympathetic root, and the anastomosis of the sym- 
 pathetic with the ophthalmic division of the trigeminus ( Wegner). The iris and 
 retina receive most of their vasomotor nerves from the trigeminus itself (Rogow), 
 and few from the sympathetic ; according to Klein and Svetlin the retinal vessels 
 are not influenced either by stimulation or division of the sympathetic. 
 
 4. Motor fibres for the dilator pupillae, which, for the most part, are derived 
 from the sympathetic {Petit, 1727'), through the sympathetic root of the ganglion, 
 and the anastomosis of the sympathetic with the trigeminus (Balogh, Oehl). The 
 ophthalmic division contains independent fibres for the dilatation of the pupil 
 (Schiff), which arise in the medulla oblongata and proceed directly into the 
 ophthalmic (? or arise from the Gasserian ganglion — Oehl). 
 
 It is not conclusively determined whether in man dilator fibres also proceed through the sympa- 
 thetic root of the ciliary ganglion, and reach the iris through the ciliary nerves. In the dog these 
 fibres do not pass through the ciliary ganglion, but go directly along the optic nerve to the eye 
 (Hensen and Volckers). In birds, the dilator fibres run only in the fifth (Zeglinski). For the 
 centre (<j 367, 8). 
 
 After section of the trigeminus, the pupil becomes contracted after a short 
 period of dilatation (rabbit, frog), but this effect is not permanent. After 
 excision of the superior cervical ganglion of the sympathetic, the power of dila- 
 tation of the pupil is not completely abolished. The narrowing of the pupil 
 which follows section of the trigeminus in the rabbit, and which rarely lasts more 
 . than half an hour, may be regarded as due to a reflex stimulation of the oculo- 
 motorius fibres of the sphincter, in consequence of the painful stimulation caused 
 by section of the trigeminus. 
 
 Stimulation of the Sympathetic. — Either in the neck, or in its course to the eye, when the 
 peripheral end of the cervical sympathetic is stimulated, besides other effects on the blood vessels, 
 there is dilatation of the pupil, as well as contraction of the smooth muscular fibres in the orbit and 
 eyelids. The membrana orbitalis, which separates the orbit from the temporal fossa in animals, 
 contains numerous smooth muscular fibres (musculus orbitalis). The corresponding membrane of 
 the inferior orbital fissure [spheno-maxillary fissure] in man has a layer of smooth muscle, one 
 
624 TROPHIC NERVES IN THE TRIGEMINUS. 
 
 millimetre thick, and arranged Tor the most part longitudinally. Both eyelids contain smooth mus- 
 cular fibres which serve to close them ; in the upper lid they lie as a continuation of the levator 
 palpebral superioris, in the lower lid close under the conjunctiva. Tenon's capsule also contains 
 smooth muscular fibres. The sympathetic nerve supplies all these muscles (Heinr. Miiller) — ^the 
 orbital muscle is partly supplied from the spheno-palatine ganglion ) ; in animals the retractor of 
 the third eyelid at the inner angle of the eye is similarly supplied. Hence, stimulation of the sym- 
 pathetic causes dilatation of the pupil and of the palbebral fissure, with protrusion of the eyeball. 
 This result may be caused reflexly by strong stimulation of sensory nerves. Strong stimulation of 
 the nerves of the sexual organs is followed by similar phenomena in the eye. The dilatation of the 
 pupil, which occurs in children affected with intestinal worms, is perhaps an analogous phe- 
 nomenon. The pupil is dilated when the spinal cord is stimulated (at the origin of the sympa- 
 thetic), as in tetanus. 
 
 Section of the Sympathetic, besides other effects, causes narrowing of the fissure between the 
 eyelids, the eyeball sinks in its socket (and in animals, the third eyelid is relaxed and protruded). 
 In dogs, section causes internal squint, as the external rectus receives some motor fibres from the 
 sympathetic (p. 631). (Origin of these fibres from the cilio-spinal region. Spinal cord, \ 362, 1.) 
 
 4. It is probable that trophic fibres occur in the trigeminus, and pass through 
 the ciliary nerves to reach the eye. If the trigeminus be divided within the cra- 
 nium, after six to eight days, inflammation, necrosis of the cornea, and ultimately 
 complete destruction of the eyeball take place, constituting Panophthalmia 
 (Fodira, 1823 ; Magendie). 
 
 Trophic Fibres. — In weighing the evidence for and against the existence of trophic fibres, we 
 must bear in mind the following considerations: 1. Section of the trigeminus makes the whole 
 eye insensible ; the animal is therefore unconscious of direct injury to its eye, and cannot there- 
 fore remove any offending body. Dust or mucus, which may adhere to the eye, is no longer re- 
 moved by the reflex closing of the eyelids; while, owing to the absence of the reflex, the eye is 
 more open and is therefore subject to more injuries ; the reflex secretion of tears is also arrested. 
 Snellen (1857) fixed the ear of a rabbit in front of its eye so as to protect the latter and shield it 
 from injuries, and he found that the inflammation and other events occurred at a later date, while, 
 according to Meissner and Buttner, if the eye be protected by means of a complete capsule, the in- 
 flammation does not occur at all. There can be no doubt that the loss of the sensibility of the eye 
 favors the occurrence of inflammation. But Meissner, Buttner, and Schiff observed thatinflam- 
 mation of the eye occurred when the trophic (most internal) fibres alone were divided, the* eye at 
 the same time retaining its sensibility; this would seem to indicate the existence of trophic fibres, 
 but Cohnheim and Senftleben dispute the statement. Conversely, the sensibility of the eye may be 
 abolished by partial section of the nerve, yet the eye does not become inflamed (Schiff). Ranvier, 
 who denies the existence of trophic nerves, made a circular incision round the margin of the cornea 
 through its superficial layers so as to divide all the corneal nerves. Insensibility of the cornea was 
 thereby produced, but never keratitis. Further, in man and animals who cannot close their eyelids, 
 there is redness with secretion of tears, or slight dryness and opacity of the surface of the eyeball 
 (Xerosis), but never the inflammation already described (Samuel). 2. We must also take into 
 consideration the following : Section of the trigeminus paralyzes the vasomotor nerves in the in- 
 terior of the eyeball, which must undoubtedly cause a disturbance in the intraocular circulation. 
 According to Jesner and Griinhagen, the trigeminus also contains vaso-dilator fibres, whose stimu- 
 lation is followed by increased flow of blood to the eye, with consecutive excretion of the fibrin 
 factors and increase in the amount of albumin of the aqueous humor. 3. After section of the 
 nerve, the intraocular tension is diminished (while stimulation of the nerve is followed by in- 
 crease of the intraocular pressure) (Hippell, Griinhagen, Adamiik). This diminution of the normal 
 tension necessarily must alter the normal relation of the filling of the blood and lymph vessels, 
 and also the movement of the fluids, upon which the normal nutrition is largely dependent. 4. 
 W. Ktihne observed that stimulation of the corneal nerves was followed by contraction of the so- 
 called corneal corpuscles. Very probably the movements of these corpuscles may influence the 
 normal movement of the lymph in the canalicular system of the cornea (g 384) ; these movements, 
 however, would seem to depend upon the nervous system, so that its destruction is likely to produce 
 disturbance of nutrition. 
 
 [There are three conditions on which the changes may depend — (1) mere loss of sensibility, 
 which alone is not sufficient to explain the phenomena ; (2) on vasomotor disturbance, which is 
 excluded by the above facts, and also by the other consideration that, if the fifth nerve be divided 
 and the superior cervical ganglion excised simultaneously, ophthalmia does not occur, and, in fact, 
 excision of this sympathetic ganglion may modify the results of section of the fifth (Sinitzin). Thus, 
 we are forced to (3) the theory of trophic fibres, whose centre is the Gasserian ganglion.] 
 
 Pathological. — In cases of anaesthesia of the trigeminus in man, and, more rarely, in severe 
 irritation of this nerve, inflammation of the conjunctiva, ulceration and perforation of the cornea, 
 and, finally, panophthalmia, have been observed (Charles Bell). This condition has been called 
 ophthalmia neuroparalytica. Samuel found that a similar result was produced by electrical 
 
BRANCHES AND CONNECTIONS OF THE TRIGEMINUS. 
 Fig. 386. 
 
 625 
 
 Semi -diagrammatic representation of the nerves of the eyeball, the connections of the trigeminus and its ganglia, 
 together with the facial and glosso-pharyngeal nerves. 3. Branch to the inferior oblique muscle from the oculo- 
 motorius, with the thick, short root, to the ciliary ganglion (c) ; /, ciliary nerves ; /, long root to the ganglion from 
 the naso-ciliary (« c) ; s, sympathetic root from sympathetic plexus (S y) surrounding the internal carotid (G) ; d, 
 first or ophthalmic division of the trigeminus (5) , with the naso-ciliary (« c), and the terminal branches of the lach- 
 rymal (a), supraorbital (6), and frontal (_/") ; e, second or superior maxillary division of the trigeminus ; R, infraor- 
 bital; «, spheno-palatine (Meckel's) ganglion with its roots; j, from the facial, and v, from the sympathetic ; N, the 
 nasal branches, and //, , the palatine branches of the ganglion, g t third or inferior maxillary division of the tri- 
 geminus ; k, lingual ; i i, chorda tympani ; m, otic ganglion, with the roots from the tympanic plexus, the carotid 
 plexus, and from the 3d branch, and with its branches to the auriculo-temporal (A), and to the chorda {i i) ; L, 
 sub-maxillary ganglion with its roots from the tympani co-lingual, and the sympathetic plexus on the external 
 maxillary artery {g). 7. Facial nerve— -j\ its great superficial petrosal branch ; a. gang, geniculatum ; f3 f branch 
 to the tympanic plexus ; v } branch to the stapedius ; , anastomatic twig to the auricular branch of the vagus ; 
 i 1, chorda tympani; S, stylo-mas to id foramen. 9. Glosso-pharyngeal — X. its tympanic branch; tz and e 
 connections with the facial; U, terminations of the gustatory fibres of 9 in the circumvallate papillae; S,y, sym- 
 pathetic with Gg, s, the superior cervical ganglion ; /, //, ///, lV f the four upper cervical nerves ; P, parotid, 
 M, sub-maxillary gland. 
 
 40 
 
626 Meckel's ganglion and its connections. 
 
 stimulation of the Ga=serian ganglion in animals. There are other affections of the eye depending 
 upon disease of the vaso-motor nerves, which are quite different from the foregoing, as they never 
 lead to degenerative changes. Such is ophthalmia intermittens (due to malaria), a unilateral, 
 intermittent, excessive filling of.the blood vessels of the eye, accompanied by the secretion of tears, 
 photophobia, often accompanied by iritis and effusion of pus into the chambers of the eye. This 
 condition was regarded as a vaso-neurotic affection of the ocular blood vessels by Eulenburg and 
 Landois. Pathological observations, as well as experiments upon animals (Mooren and Rumpf), 
 have shown that there is an intimate physiological connection between the vascular areas of both 
 eyes, so that affections of the vascular area of one eye are apt to induce similar disturbances of the 
 opposite eye. This serves to explain the fact that inflammatory processes in the interior of one eye- 
 ball are apt to produce a similai condition in the other eye. This is the so-called "sympathetic 
 ophthalmia." Thus, stimulation of the ciliary nenes, or the fifth on one side, causes dilatation of 
 the blood vessels not only on its own side, but also on the other side as well (Jesner and Griin- 
 hagen). The pathological condition of glaucoma simplex, where the intraocular tension is greatly 
 increased, is ascribed by Donders to irritation of the trigeminus. [Increased intraocular tension 
 may be produced by irritation of the secretory fibres contained in the fifth nerve (Donders), by 
 stimulating the nucleus of the trigeminus in the medulla oblongata (Hippell and Griinhagen), and 
 also reflexly by irritation of the peripheral branches of the fifth, as by nicotin placed in the eye. It 
 is possible, however, that some forms of glaucoma are produced by diminished removal of the 
 aqueous humor from the eye.] 
 
 II. Superior Maxillary Division (E) Ic gives off — 
 
 i. The delicate recurrent nerve, a sensory branch to the dura mater, which 
 accompanies the vasomotor nerves, derived from the superior cervical ganglion 
 of the sympathetic, and is distributed to the area of the middle meningeal 
 artery. 
 
 2. The subcutaneous malar (o) (or orbital) supplies by its temporal and 
 orbital branches sensibility to the lateral angle of the eye and the adjoining area 
 of skin of the temple and the cheek. Certain fibres of the nerve are said to be 
 the true secretory nerves for tears. Compare N. lacrymalis, p. 621 (Herzenstein 
 and Wolferz). 
 
 3. The dental, anterior, posterior, and medius, and with them the anterior 
 fibres from the infraorbital nerve, supply sensory fibres to the teeth in the upper 
 jaw, the gum, periosteum, and the cavities of the jaw (p. 624). The vasomotor 
 nerves of all these parts are supplied from the upper cervical ganglion of the sym- 
 pathetic. 
 
 4. The infraorbital (R), after its exit from the infraorbital foramen, supplies 
 sensory nerves to the lower eyelid, the bridge and sides of the nose, and the 
 upper lip as far as the angle of the mouth. The accompanying artery receives its 
 vasomotor fibres from the superior cervical ganglion of the sympathetic. With 
 regard to the fibres for the secretion of sweat which occur in it (pig), see § 288. 
 
 The spheno-palatine ganglion (Meckel's — n) forms connections with the 
 II division. To it pass two short sensory root fibres from the II division itself, 
 which are called spheno-palatine. Motor fibres enter the ganglion from behind, 
 through the large superficial petrosal branch of the facial (/ — Bidder, Nuhri) ; 
 and, lastly, gray vasomotor fibres (v) from the sympathetic plexus on the 
 carotid (the deep, large petrosal nerve). The motor and vasomotor fibres from 
 the Vidian nerve, which reaches the ganglion through the canal of the same 
 name. 
 
 Branches of the Ganglion. — The branches proceeding from the ganglion 
 are: (1) The sensory fibres (N) which supply the roof, lateral walls, and septum 
 of the nose (posterior and superior nasal) ; the terminal fibres of the naso-pala- 
 tine pass through the canalis incisivus to the hard palate, behind the incisor teeth. 
 The sensory inferior and posterior nasals for the lower and middle turbinated 
 bones, and both lower nasal ducts, are derived from the anterior palatine branch 
 of the ganglion, which descends in the palato-maxillary canal. Lastly, the sensory 
 branches for the hard (/) and soft palate (/j) and the tonsils arise from the pos- 
 terior palatine nerve. All the sensory fibres of the nose (see also the Ethmoidal 
 nerve), when stimulated, cause the reflex act of sneezing (§ 120). Preparatory 
 
INFERIOR MAXILLARY DIVISION. 627 
 
 to the act of sneezing there is always a peculiar feeling of tickling in the nose, 
 which is perhaps due to dilatation of the nasal blood vessels. This dilatation is 
 rapidly caused by cold, more especially when it is applied directly to the skin. 
 The dilatation of the vessels is followed by an increased secretion of watery fluid 
 from the nasal mucous membrane. Stimulation of the nasal nerves also causes a 
 reflex secretion of tears, and it may also cause stand-still of the respiratory move- 
 ments in the expiratory phase (Hering and Kratschmer) — (compare Respiratory 
 centre, § 368). (2) The motor branches descend in the posterior palatine nerve 
 through the small palatine canal, and give off (K) motor branches to the elevator 
 of the soft palate and azygos uvulae (Nuhn, Fruhwald). The sensory fibres for 
 these muscles are supplied by the trigeminus. According to Politzer, spasmodic 
 contraction of these muscles occasionally causes crackling noises in the ears. (3) 
 The vasomotor nerves of this entire area arise from the sympathetic root, i. e. , 
 from the upper cervical ganglion. (4) The root of the trigeminus supplies the 
 secretory nerves of the mucous glands of the nasal mucous membrane. Stimu- 
 lation excites secretion, while section of the trigeminus diminishes it with simul- 
 taneous atrophic degeneration of the mucous membrane. Thus trophic functions 
 for the mucosa have been ascribed to the trigeminus (Aschenbrandf). 
 
 Stimulation of the Ganglion.— Feeble electrical stimulation of the exposed ganglion causes a 
 copious secretion of mucus and an increase of the temperature in the nose (Prevost), with dilation 
 of the vessels (Aschenbrandt). [Meckel's ganglion has been excised in certain cases of neuralgia 
 ( Walsham).~\ 
 
 III. Inferior Maxillary (G). — It contains all the motor fibres of the fifth, 
 along with a number of sensory fibres ; it gives off — 
 
 1. The recurrent, which springs by itself from the sensory root, enters the 
 skull through the foramen spinosum, and, along with the nerve of the same name 
 from the II division, it supplies sensory fibres to the dura mater. Fibres proceed 
 from it through the petroso-squamosal fissure to the mucous membrane of the cells 
 of the mastoid process. 
 
 2. Motor fibres for the muscles of mastication, viz., the masseteric, the two 
 deep temporal nerves, and the internal and external pterygoid nerves. The sen- 
 sory fibres for the muscles are supplied by the sensory fibres. 
 
 3. The buccinator is a sensory nerve for the mucous membrane of the cheek, 
 and the angle of the mouth as far as the lips. 
 
 According to Jolyet and Laffont, it contains, in addition, vasomotor fibres for the mucous mem- 
 brane of the cheek, lower lip, and their mucous glands ; but these fibres are probably derived from 
 the sympathetic. 
 
 Trophic Fibres. — As this region of the mucous membrane of the mouth ulcerates after section 
 of the trigeminus, some have supposed that the buccinator nerve contains trophic fibres. But, as 
 Rollett pointed out, section of the inferior maxillary nerve paralyzes the muscles of mastication on 
 the same side, and hence the teeth do not act vertically upon each other, but press against the cheek. 
 Owing to the loss of the sensibility of the mouth, food passes between the gum and the cheek, 
 where it may remain attached, undergo decomposition, and perhaps chemically irritate the mucous 
 membrane. At a later stage, owing to the wearing away of the teeth in an oblique manner, ulcers 
 begin to form on the sounit side. Hence, there is no necessity for assuming the existence of trophic 
 fibres in this nerve. After section of the trigeminus, the nasal mucous membrane on the same side 
 becomes red and congested. This is due to the fact that dust or mucus, not being removed from 
 the nose by the usual reflex acts, remains there, irritates, and ultimately causes inflammation. 
 
 4. The lingual (k) receives at an acute angle the chorda tympani (it), a branch 
 of the facial coming from the tympanic cavity. The lingual does not contain 
 any motor fibres ; it is the sensory and tactile nerve of the anterior two-thirds 
 of the tongue, of the anterior palatine arch, the tonsil, and the floor of the mouth. 
 These, as well as all the other sensory fibres of the mouth, when stimulated, cause 
 a reflex secretion of saliva (compare § 145). The lingual is accompanied by 
 the nerve of taste (chorda) for the tip and margins of the tongue (i. e. , the parts 
 not supplied by the glossopharyngeal). After section of the lingual nerve in 
 man, Busch, Inzani and Lusanna found that the tactile sensibility was lost in the 
 
628 SUB-MAXILLARY GANGLION AND ITS CONNECTIONS. 
 
 half of the tongue, and there was loss of taste in the anterior part [two-thirds] of 
 the tongue. The fibres which administer to the sense of taste do not, as a rule, 
 belong to the lingual itself, but are derived from the chorda tympani (p. 631). 
 According to Schiff, the lingual nerve is the gustatory nerve, and some cases of 
 Erb and Senator support this view. Such cases, however, seem to be exceptions 
 to the general rule. The lingual nerve in the substance of the tongue is provided 
 with small ganglia {Remak, Stirling). Schiff observed that section of the lingual 
 (and also of the hypoglossal) caused redness of the tongue, so that vasomotor fibres 
 are present in its course. It is unknown whether these are derived from the anas- 
 tomoses of the Gasserian ganglion with the sympathetic. The lingual appears to 
 receive vaso-dilator fibres from the chorda for the tongue and gum (§ 349). 
 
 After section of the trigeminus, animals frequently bite their tongue, as they cannot feel the posi- 
 tion and movements of this organ in the mouth. 
 
 5. The inferior dental is the sensory branch to the teeth and gum; the 
 vasomotor fibres reach it from the superior cervical ganglion. Before it passes 
 into the canal in the lower jaw it gives off the mylo-hyoid nerve, which supplies 
 motor fibres to the mylo-hyoid and the anterior belly of the digastric, and also 
 some fibres to the triangularis menti and the platysma ; the muscular sensory 
 nerves also lie in these branches. The mental nerve, which issues from the 
 mental foramen, is the sensory nerve for the chin, lower lip, and the skin at the 
 margin of the jaw. 
 
 6. The auriculo temporal gives sensory branches to the anterior wall of 
 the external auditory meatus, the tympanic membrane, the anterior part of the 
 ear, the adjoining region of the temple, and to the maxillary articulation. 
 
 Fig. 387 shows the distribution of the branches of the trigeminus on the head, and the cervical 
 nerves, so that the distribution of anaesthetic and hyperaesthetic areas may easily be made out. 
 
 The otic ganglion (m) lies beneath the foramen ovale on the inner side of the 
 third division. Its roots are — (1) short motor fibres from the third division ; 
 (2) vasomotor from the plexus around the middle meningeal artery (ultimately 
 derived from the cervical ganglion of the sympathetic) ; (3) fibres (A) run from 
 the tympanic branch of the glosso-pharyngeal to the tympanic plexus, and from 
 thence through the canaliculus petrosus in the small superficial petrosal in the 
 cranium, then through a small canal between the apex of the petrous bone 
 and the sphenoid, to reach the otic ganglion. Through the chorda tympani the 
 facial nerve is constantly connected with the ganglion (Fig. 387). 
 
 The branches of the otic ganglion are — (1) the motor twigs for the tensor 
 tympani and tensor of the soft palate (these fibres are mixed with muscular sen- 
 sory fibres — Ludwig and Politzer) ; (2) one or more branches connecting the 
 ganglion with the auriculo-temporal are carried by the roots 2 and 3 from the 
 sympathetic and glosso-pharyngeal, which the auriculo-temporal nerve (A), as it 
 passes through the parotid gland (P), gives off to the gland. These are the 
 secretory fibres for the parotid ; their functions are stated in § 145. 
 
 Section of the trigeminus is followed by inflammatory changes in the (rabbit) tympanic cavity; 
 the degree of inflammation varies much (Berthold and Grunhagen, Kirchner). Section of the 
 sympathetic or glosso-pharyngeal has no effect. 
 
 The sub-maxillary ganglion (Z) lies close to the convex arch of thetympatiico- 
 lingual nerve and the excretory duct of the sub-maxillary gland (M '). Its roots 
 are — (1) branches of the chorda tympani, i, i (which undergo fatty degenera- 
 tion after section of facial nerve — Vulpian). This root supplies secretory fibres 
 to the sub-maxillary and sublingual glands, but it also supplies vaso-dilator fibres 
 for the blood vessels of the same glands (§ 145). In addition, fibres are supplied 
 to the smooth muscular fibres in Wharton's duct. All the fibres of the chorda do 
 not pass into the gland ; some pass along with the lingual nerve into the tongue 
 (see Chorda, under Facial Nerve"). (2) The sympathetic root of the ganglion 
 
SUB-MAXILLARY GANGLION AND ITS CONNECTIONS. 
 
 629 
 
 arises from the plexus around the submental branch of the external maxillary 
 artery (y), i.e., ultimately from the superior cervical ganglion ; it passes to the 
 gland, and contains secretory fibres, whose stimulation is followed by the secre- 
 tion of thick concentrated saliva (trophic nerve of the gland). It also carries 
 the vaso-constrictor nerves to the gland (p. 238). (3) The sensory root springs 
 from the lingual. Some of the fibres, after passing through the ganglion, supply 
 the gland and its excretory ducts, while a few issue from the ganglion, and again 
 join the tympanico-lingual nerve to reach the tongue. 
 
 Pathological. — Trismus, or spasm of the muscles of mastication, supplied by the third divi- 
 
 Fig. 387. 
 
 Dtuse. temporalis. 
 
 Mane, maweter 
 
 TS. hypoglossal. 
 
 Platysma rnyoide-. 
 Muse Bternohyoideua. 
 
 Muse BternothyreoideuB. 
 
 Mime, omohyoldeua. 
 
 Nd. thoracic! anteriores, 
 
 Muse, splenitis. 
 
 Muse, starnoclefdomaatofdetui. 
 
 N. accessoriufl 
 
 Mubq. levator angult ■capulae. 
 
 Mubc cu<nil]ar1n or traperiiia. 
 
 N. dorealia scapulae. 
 
 K. axillaris. 
 
 N. thoracici* 1 -.ng-ti*. 
 
 K. phwnlcua. Krb'a 
 
 Supraclavicular- 
 wtrt. 
 
 Distribution of the sensory nerves on the head as well as the position of the motor points on the neck. SO, area of 
 distribution of the supraorbital nerve; ST, supratrochlear; IT, infra trochlear ; L, lachrymal; N, ethmoidal; 
 JO, infraorbital ; B, buccinator ; SM, subcutaneous malae ; A T, auriculo-temporal ; AM, great auricular ; OMj, 
 great occipital ; OMi, lesser occipital ; C a , three cervical nerves ; CS, cutaneous branches of the cervical nerves ; 
 CW, region of the central convolutions of the brain ; SC, region of the speech centre (third left frontal convolution). 
 
 sion, is usually bilateral ; it may be clonic in its nature (chattering of the teeth), or tonic, when it 
 constitutes the condition of lockjaw or trismus. The spasms are usually individual symptoms of 
 more extensive convulsions, more rarely when they occur alone they are symptomatic of disease of 
 the cerebrum, medulla, pons and cortex of the frontal convolutions {Euienburg). The spasms may 
 be caused reflexly, e.g. t by stimulation of the sensory nerves of the head. 
 
 Paralysis — Degeneration of the motor nuclei, or affections of the intracranial root of the 
 nerve, causes paralysis of the muscles of mastication, which is very rarely bilateral. Paralysis of 
 the tensor tympani is said to cause difficulty of hearing (Romberg), or buzzing in the ears (Bene- 
 diet). We require further observations upon this point, as well as upon paralysis of the tensor of 
 the soft palate. 
 
 Neuralgia may occur in all the branches of the fifth. It consists of severe attacks of pain 
 
630 NERVUS ABDUCENS. 
 
 shooting into the expansions of the nerves. It is usually unilateral, and in fact is often confined to 
 one branch, or even to a few twigs of one branch. The point from which the pain proceeds is fre- 
 quently the bony canal through which the branch issues. The ear, dura mater and tongue are 
 rarely attacked. The attack is not unfrequently accompanied by contractions or twitchings of the 
 corresponding group of the facial muscles. The twitchings are either reflex, or are due to direct 
 peripheral irritation of the fibres of the facial nerve, which are mixed with the terminal branches of 
 the trigeminus. The reflex twitchings may be extensively distributed, involving even the muscles 
 of the arm and trunk. 
 
 Redness or congestion of the affected part of the face is not an unfrequent symptom in neu- 
 ralgia, and it may be accompanied by increased or diminished secretion from the nasal and buccal 
 mucous membranes. This is a reflex phenomenon, the sympathetic being affected. Reflex stimu- 
 lation of the vasomotor nerves frequently gives rise to disturbance of the cerebral activities, owing 
 to changes in the distribution of the blood in the head. Ludwig and Dittmar found that stimula- 
 tion of sensory nerves caused a reflex contraction of the arterial blood vessels, and increase of the 
 blood pressure in the cerebral vessels. Sometimes there is melancholy or hypochondriasis, and in 
 one case of violent pain in the inferior maxillary nerve the attack was accompanied by hallucina- 
 tions of vision. 
 
 The trophic disturbances which sometimes accompany affections of the trigeminus are partic- 
 ularly interesting. They are : a brittle character of the hair, which frequently becomes gray, or 
 may fall out ; circumscribed areas of inflammation of the skin, and the appearance of a vesic- 
 ular eruption upon the face [often following the distribution of certain nerves], and constituting 
 herpes, which may also occur on the cornea, constituting the neuralgic herpes cornese of Schmidt- 
 Rimpler. 
 
 Lastly, there is the progressive atrophy of the face which is usually confined to one side, but 
 may occur on both sides {Eulenburg, Flasher). It is caused very probably by a trophic affection 
 of the trigeminus, although the vasomotor nerves may also be affected reflexly. Landois found 
 that in the famous case of Romberg, a man named Schwahn, the sphygmographic tracing of the 
 carotid pulse of the atrophied side was distinctly smaller than on the sound side. 
 
 Urbantschitsch made the remarkable observation that stimulation of the branches of the trigemi- 
 nus, especially those going to the ear, caused an increase of the sensation of light in the person 
 so stimulated. Blowing upon the cheeks or nasal mucous membrane, electrical stimulation, the use 
 of snuff, smelling strong perfumes — all temporarily increase the sensation of light. The senses of 
 taste and smell, as well as the sensibility of certain areas of the skin, can all be exalted reflexly by 
 gentle stimulation of the trigeminus. In intense affections of the ear, whereby the fibres of the 
 trigeminus are often affected sympathetically, these sensory functions may be diminished. As the 
 ear malady begins to improve, the excitability of these sense organs also again begins to improve. 
 
 [Complete section of the trigeminus results in loss of sensibility in all the 
 parts supplied by it (Fig. 387), including one side of the face, temple, part of 
 the ear, the fore part ot the head, conjunctiva, cornea, mouth, gums, Schneiderian 
 mucous membrane, anterior two-thirds of the tongue, and part of pharynx. In 
 drinking from a vessel, the patient feels as if one side of it were cut away. The 
 muscles of mastication are paralyzed on that side, food is not chewed on one side, 
 and fur accumulates on the tongue on that side. The mucous membranes tend to 
 ulcerate, that of the mouth being chafed by the teeth, the gums get spongy, the 
 nasal mucous membrane tends to ulcerate, so that the smell is interfered with, and 
 ammonia excites no reflex acts, while the eye undergoes panophthalmia.] 
 
 [Gowers is of opinion that the sensation of taste on the posterior part of the tongue, soft palate, 
 and palatine arch depends on the filth nerve and not on the glosso- pharyngeal nerve.] 
 
 348. VI. NERVUS ABDUCENS.— Anatomical.— It rises slightly in front of and partly 
 from the nucleus ot the facial nerve (which corresponds to the anterior horn of the spinal cord), 
 from large-celled ganglia in the deeper part of the anterior region of the fourth ventricle, (emenentia 
 teres, Fig. 384). [Its nucleus is connected with the nucleus of the third nerve of the opposite side. 
 It appears at the posterior margin of the pons (Fig. 385, VI). This nerve has a very long course 
 before it enters the orbit, and as it bends over the posterior margin of the pons, it is liable to be com- 
 pressed there or from pressure upon the tentorium cerebelli, so that both ner\ es are very liable to 
 paralysis.] 
 
 Function. — It is the voluntary nerve of the external rectus muscle. In co- 
 ordinate movements of the eyeballs, however, it is involuntary. 
 
 Anastomoses. — Branches reach it from the sympathetic upon the cavernous sinus (Fig. 386). A 
 few come from the trigeminus, and their function is analogous to similar fibres supplied to the 
 trochlearis and oculomotorius. 
 
THE CHORDA TYMPANI AND TASTE. 631 
 
 Pathological. — Complete paralysis causes squinting inward [or convergent squinf\ and conse- 
 quent diplopia. [The eye cannot be rotated outward beyond the middle line, the double images 
 are in the same horizontal plane and vertical, the false one is to the left of the patient's eye when 
 the left eye is affected (Fig. 383, 2). The feeling of giddiness is often severe. There is secondary 
 deviation to the inner side, and the head is turned toward the affected side.] In dogs, section of 
 the cervical sympathetic causes a slight deviation of the eyeball inward {Petit). This is explained 
 by the fact that the abducens receives a few motor fibres from the cervical sympathetic. Spasm 
 of the abducens causes external squint. 
 
 Squint — In addition to paralysis or stimulation of certain nerves producing squint, it is to be 
 remembered that it may also be caused by a primary affection of the muscles themselves, e.g., con- 
 genital shortness, contracture, or injuries of these muscles. It may also be brought about owing to 
 opacities of the transparent media of the eye ; a person with, say an opacity of the cornea, rotates 
 the affected eye involuntarily, so that the rays of light may enter the eye through the clear part of 
 the media. 
 
 349. VII. NERVUS FACIALIS.— Anatomical.— This nerve consists entirely of efferent 
 fibres, and arises from the floor of the fourth ventricle from the " facial nucleus " (Fig. 384, 7), 
 which lies behind the orgin of the abducens, and also by some fibres from the nucleus of the ab- 
 ducens [although Gower's observations do not confirm this (§ 366).] Other fibres arise from the 
 cerebrum of the opposite side (§ 378, I). It consists of two roots, the smaller — portio intermedia 
 of Wrisberg — forms a connection with the auditory nerve (see f! 350). The original fibres ot the 
 portio intermedia are developed from the glosso-pharyngeal nucleus (Sapolini). It would thus 
 appear that the sensory and gustatory fibres which are present in the chorda tympani enter it through 
 these fibres {Duval, Schultze, Vulpian), so that the portio intermedia is a special part of the nerve 
 of taste, which becomes conjoined with the facial, and runs to the tongue in the chorda. Along 
 with the auditory nerve, it traverses the porus acusticus internus, where it passes into the facial or 
 Fallopian canal. At first it has a transverse direction as far as the hiatus of this canal ; it then 
 bends at an acute angle at the "knee" (a) above the tympanic cavity, to descend in an ossecjus 
 canal in the posterior wall of this space (Fig. 386). It emerges from the stylo-mastoid foramen, 
 pierces the parotid gland, and is distributed in a fan-shaped manner (pes anserinus major). [The 
 superficial origin is at the lower margin of the pons, in the depression between the olivary body 
 and the restiform body, as indicated in Fig. 385, VII a.] 
 
 Its branches (Fig. 386) are : 1. The motor, large superficial petrosal (j). 
 It arises from the "knee " or geniculate ganglion within the Fallopian canal, in 
 the cavity of the skull, runs upon the anterior surface of the temporal bone, 
 traverses the foramen lacerum medium on the under surface of the base of the 
 skull, and passes through the Vidian canal to reach the spheno-palatine ganglion 
 (p. 626). It is uncertain whether this nerve conveys sensory branches from the 
 second division of the trigeminus to the facial. 
 
 2. Connecting branches Q?) pass from the geniculate ganglion to the otic gan- 
 glion. For the course and function of these fibres, see Otic ganglion (p. 628). 
 
 3. The motor branch to the stapedius muscle (/). 
 
 4. The chorda tympani (/, i), arises from the facial before it emerges at the . 
 stylo-mastoid foramen (s), runs through the tympanic cavity (above the tendon of 
 the tensor tympani, between the handle of the malleus and the long process of the 
 incus), passes out of the skull through the petro-tympanic fissure, and then joins 
 the lingual nerve at an acute angle (p. 627, 4). Before it unites with this nerve, 
 it exchanges fibres with the otic ganglion (m). Thus, sensory fibres can enter 
 the chorda from the third division of the trigeminus {E. Bischoff), which may run 
 centripetally to the facial to be distributed along with it. In the same way, sen- 
 sory fibres may pass from the lingual nerve through the chorda into the facial 
 (Longet), Stimulation of the chorda — which even in man may be done in cases 
 where the tympanic membrane is destroyed — causes a prickling feeling in the an- 
 terior margins and tip of the tongue (Troltsck). O. Wolfe found that the section 
 of the chorda in man abolished the sensibility for tactile and thermal stimuli 
 upon the tip of the tongue ; and the same was true of the sense of taste in this 
 region. It is supposed by Calori that these fibres enter the facial nerve at its per- 
 iphery (especially through the auriculo-temporal into the branches of the facial), 
 that they run in a centripetal direction in the facial, and afterward pursue a cen- 
 trifugal course in the chorda. [It is possible that sensory fibres pass from the 
 spheno-palatine ganglion of the fifth through the Vidian nerve and large superfi- 
 
632 BRANCHES OF THE FACIAL. 
 
 cial petrosal to enter the facial. These fibres may be those that appear in the 
 seventh as the chorda fibres which administer to taste. Bigelow asserts that the 
 chorda tympani is not a branch of the facial, but the continuation of the nervus 
 intermedius of Wrisberg.] The chorda also contains secretory and vaso-dilator 
 fibres for the sub-maxillary and sublingual glands (§ 145). 
 
 Gustatory Fibres. — The chorda also contains fibres administering to the sense 
 of taste, for the margin and tip of the tongue (anterior two-thirds), which are 
 conveyed to the tongue along the course of the lingual. Urbantschitsch made 
 observations upon a man whose chorda was freely exposed, and in whom its stim- 
 ulation in the tympanic cavity caused a sensation of taste (and also of touch) in the 
 margins and tip of" the tongue. 
 
 It would seem, therefore, that the gustatory fibres of the chorda have their 
 origin in the glosso-pharyngeal nerve. They may reach the chorda: 1. Through 
 the portio intermedia of Wrisberg, as already mentioned. 
 
 2. There is a channel beyond the stylomastoid foramen, viz., through the ramus communicans 
 cum glosso-pharyngeo (Fig. 386, e), which passes from the last-mentioned nerve in that branch of 
 the facial which contains the motor fibres for the stylohyoid and posterior belly of the digastric 
 (Henle's N. styloideus). This nerve also supplies muscular sensibility to the stylohyoid and pos- 
 terior belly of the digastric muscles. It is also assumed that, by means of these anastomoses, motor 
 fibres are supplied by the facial to the glosso-pharyngeal nerve. 3. A union of the glosso-pharyngeal 
 and facial nerves occurs in the tympanic cavity. The tympanic branch of the glosso-pharyngeal (A) 
 passes into this cavity, where it unites in the tympanic plexus with the small superficial petrosal nerve 
 (P), which springs from the knee on the facial. The gustatory fibres may first pass into the otic 
 ganglion.which is always connected with the chorda (Otic ganglion, p. 628, 6). Lastly, a connec- 
 tion is described through a twig (w) from the petrous ganglion of the glosso-pharyngeal, direct to 
 the facial trunk within the Fallopian canal {Garibaldi). 
 
 Vaso-dilator Fibres. — According to some observers, the chorda contains 
 vaso-dilator fibres for the tongue, but no motor fibres (Heidenhain). 
 
 Pseudo-motor Action. — From one to three weeks after the section of the hypoglossal nerve, 
 stimulation of the chorda causes movements in the tongue {Philippeaux and Vulpian, H. Heiden- 
 kain). These movements are not so energetic, and occur more slowly than those caused by stimu- 
 lation of the hypoglossal. Nicotin first excites, then paralyzes, the motor effect of the chorda. Even 
 after cessation of the circulation, stimulation of the chorda causes movements. Heidenhain supposes 
 that, owing to the stimulation of the chorda, there is an increased secretion of lymph within the 
 musculature, which acts as the cause of the muscular contraction. He called this action " pseudo 
 motor." 
 
 [If, after the union of the central end of the lingualis and the peripheral end of the hypoglossal 
 nerve, the lingualis be stimulated, there is a genuine contraction of the musculature of the tongue on 
 that side. If, after the union of the central end of the hypoglossal with the peripheral end of the 
 lingual, there is no effect. A pseudo-motor contraction is easily distinguished from a true contrac- 
 tion, for when a telephone be connected with the tongue, on stimulating the hypoglossal the tone of 
 the tetanus thereby produced is heard, but on stimulating the lingual, although the pseudo-motor 
 contractions occur, no sound is heard (Rogotvicz).] 
 
 5. Connection with Vagus. — Before the chorda is given off, the trunk of the facial comes into 
 direct relation with the auricular branch of the vagus (S), which crosses it in the mastoid canal (see 
 
 Vagus), and supplies it with sensory nerves. 
 
 6. Peripheral Branches. -^After the facial issues from its canal, it supplies 
 motor fibres to the stylohyoid and posterior belly of the digastric, the occipitalis, 
 and also to all the muscles of the external ear and the muscles of expression, to 
 the buccinator and platysma. The facial also contains secretory fibres for the 
 face (compare § 288). 
 
 Although most of the branches of the facial are under the influence of the will, yet most men 
 cannot voluntarily move the muscles of the nose and ear. 
 
 Anastomoses. — The branches of the seventh nerve on the face anastomose 
 with those of the trigeminus. Thus, sensory fibres are conveyed to the muscles of 
 expression. The sensory branches of the auricular branch of the vagus and the 
 great auricular enter the peripheral ends of the facial and supply sensibility to the 
 
UNILATERAL AND DOUBLE PARALYSIS OF THE FACIAL. 
 
 633 
 
 muscles of the ear, while the sensory fibres of the third cervical nerve similarly 
 supply the platysma with sensibility. Section of the facial at the stylomastoid for- 
 amen is painful, but it is still more so if the peripheral branches on the face are 
 divided (Magendie) (compare Recurrent sensibility, § 355). 
 
 Pathological. — In all cases of paralysis of the facial, the most important point to determine 
 is whether the seat of the affection is in the periphery, in the region of the stylomastoid foramen, 
 or in the course of the long Fallopian canal, or is central (cerebral) in its origin. This point must 
 be determined by an analysis of the symptoms. Paralysis at the stylomastoid foramen is very fre- 
 quently rheumatic, and probably depends upon an exudation compressing the nerve ; the exuda- 
 tion probably occupying the lymph space described by Rudinger on the inner side of the Fallopian 
 canal, between the periosteum and the nerve, and which is a continuation of the arachnoid space. 
 Other causes are — inflammation of the parotid gland, direct injury, and pressure from the forceps 
 during delivery. In the course of the canal, the causes are — fracture of the temporal bone, effu- 
 sion of the blood into the canal, syphilitic effusions, and caries of the temporal bone; the last some- 
 
 Fig. 388. 
 
 M. frontalis. 
 
 M. corrugator supercilii. 
 M. orbicular palpebr. 
 
 Upper branches of the Facial. 
 Trunk of the Facial. 
 Mm. retrahens 
 
 et attolens auricul. 
 
 Muse, occipitalis. 
 
 Middle branches of the Facial. 
 
 M. stylohyoideus. 
 
 M. digastricus. 
 
 Lower branches of the Fac ial 
 
 M. compressor nasi et pyram nasi 
 M. levator lab. sup. alaque nasi. 
 M. levator lab. sup. propr. 
 M. zygomatic, minor. 
 M. dilatat. narium. 
 M. zygomatic major. 
 
 M. orbicularis oris. 
 
 M. levator menti. 
 M. quadratus menti. 
 M. triangularis menti. 
 
 Motor points of the facial nerve and the facial muscles supplied by it. 
 
 times occurs in inflammation of the ear. Among intracranial causes are — affections of the mem- 
 branes of the brain, and of the base of the skull in the region of the nerve, disease of the " facial 
 nucleus ;" lastly, affection of the cortical centre of the nerve and its connections with the nucleus. 
 [No nerve is so liable as the seventh to be paralyzed independently.] 
 
 Symptoms of Unilateral Paralysis of the Facial or [Bell's Paralysis], — 1. Paralysis of 
 the muscles of expression : the forehead is smooth, without folds, the eyelids remain open 
 (Lagophthalmus paralyticus), the outer angle being slightly lower. The anterior surface of the 
 eye rapidly becomes dry, the cornea is dull, as, owing to the paralysis of the orbicularis, the tears 
 are not properly distributed over the conjunctiva, and, in fact, in consequence of the dryness of the 
 eyeball, there may be temporary inflammation (Keratitis xerotica). In order to protect the eye- 
 ball from the light, the patient turns it upward under the upper eyelid {Bell), relaxes the levator 
 palpebrse, which allows the lid to fall somewht {Hasse). The nose is immovable, while the naso- 
 labial fold is obliterated. As the nostrils cannot be dilated, the sense of smell is interfered with. 
 The impairment of the sense of smell depends more, however, upon the imperfect conduction of 
 
634 NERVUS ACUSTICUS. 
 
 the tears, owing to paralysis of the orbicularis palpebrarum and Horner's muscle, and thus causing 
 dryness of the corresponding side of the nasal cavity. Horses, which distend the nostrils widely 
 during respiration, after section of both facial nerves, are said by CI. Bernard to die from interfer- 
 ence with the respiration, or at least they suffer from severe dyspnoea [Ellenberger). The face is 
 drawn toward the sound side, so that the nose, mouth, and chin are oblique. Paralysis of the buc- 
 cinator interferes with the proper formation of the bolus of food; the food collects between the 
 cheek and the gum, from which it is usually removed by the patient with his fingers ; saliva and 
 fluids escape from the angle of the mouth. During vigorous expiration the cheeks are puffed out- 
 ward like a sail. The speech may be affected, owing to the difficulty of sounding the labial con- 
 sonants (especially in double paralysis), and the vowels, u, ii (ue), o (oe) ; while the speech, in 
 paralysis of the branches to both sides of the palate, becomes nasal (j! 628). The acts of whistling, 
 sucking, blowing, and spitting are interfered with. In double paralysis many of these sympioms 
 are greatly intensified, while others, such as the oblique position of the features, disappear. The 
 . features are completely relaxed ; there is no mimetic play of the features, the patients weep and 
 laugh, " as it were, behind a mask " [Romberg). 2. In paralysis of the palate, when the uvula 
 is directed toward the sound side, and the paralyzed half of the palate hangs down and cannot be 
 raised (large superficial petrosal nerve), it is not determined to what extent this condition influences 
 the act of deglutition and the formation of the consonants. 3. Taste is interfered with; either it 
 is absent on the anterior two-thirds of the tongue, or the sensation is delayed and altered. This is 
 due to an affection of the chorda. 4. Diminution of saliva on the affected side was first described 
 by Arnold; still, we must determine to what extent a simultaneous affection of the sense of taste 
 may cause a reflex interference with the secretion of saliva, or whether rapid removal of the saliva 
 through the opened lips and angle of the mouth may cause the dryness on the affected side of the 
 mouth. 5. Roux pointed out that hearing is affected, the sensibility to sounds being increased 
 (Oxyakoia, Hyperakusis Willisiana). The paralysis of the stapedius muscle makes the stapes 
 loose in the fenestra ovalis, so that all impulses from the tympanum act vigorously upon the stapes, 
 which consequently excites considerable vibrations in the fluid of the inner ear. More rarely, in 
 paralysis of the stapedius, it has been observed that low notes are heard at a greater distance than 
 on the sound side (Lucae, Moss). 
 
 As the facial in man appears to contain fibres for the secretion of sweat, this explains the loss 
 of the power of sweating in the face when the nerve begins to atrophy [Strauss, Block). 
 
 Section of the facial in young animals causes atrophy of the corresponding muscles. The 
 facial bones are also imperfectly developed ; they remain smaller, and hence the bones of the sound 
 side of the face grow toward, and ultimately across, the middle line toward the affected side [Brown- 
 Siquard, Briicke, Schauta, Gudden). The salivary glands also remain smaller [Briicke). 
 
 Stimulation — or irritation in the area of (at facial — causes partial or extensive, either direct or 
 reflex, tonic or clonic spasms. The extensive forms are known as " mimetic facial spasm." 
 Among the partial forms, are tonic contraction of the eyelid (Blepharospasm) which is most 
 common; and is caused reflexly by stimulation of the sensory nerves of the eye, e.g., in scrofulous 
 ophthalmia, or from excessive sensibility of the retina (photophobia). More rarely the excitement 
 proceeds from some more distant part, e.g., in one cause recorded by v. Grafe, from inflammatory 
 stimulation of the anterior palatine arch. The centre for the reflex is the facial nucleus. The 
 clonic form of spasm — spasmodic winking (Spasmus nictitans) — is usually of reflex origin, due 
 to irritation of the eye, the dental nerves, or even of more distant nerves. In severe cases the 
 affection may be bilateral, and the spasms may extend to the muscles of the neck, trunk and upper 
 extremities. Contraction of the muscles of the lip may be excited by emotions (rage, grief), or 
 reflexly. Fibrillar contractions occur after section of the facial as a " degeneration phenomenon " 
 (p. S 12 )- [If tne facial be torn out at the stylo-mastoid foramen, there is paralytic oscillation of 
 the lip muscles [Schiff). If in such an animal the posterior root of the annulus of Vieussens be 
 stimulated electrically, as it contains vasp-dilator fibres [Dastre and Mora f), not only do the blood 
 vessels of the cheek and lips dilate, but the veins pulsate and florid blood escapes from the veins, 
 just as occurs in the sub-maxillary gland when the chorda is stimulated. On stimulating the ansa 
 after section of the seventh, there is a pseudomotor effect on the muscles of the cheek and lips, 
 so that there is an analogy between the chorda and the ansa [Rogowicz).~\ Intracranial stimulation 
 of the most varied description may cause spasms. Lastly, facial spasm may be part of a general 
 spasmodic condition, as in epilepsy, chorea, hysteria, tetanus. Aretaeus (81 a.d.) made the inter- 
 esting observation that the muscles of the ear contracted during tetanus. Very rarely have spas- 
 modic elevation of the palate and increased salivation been described as the result of irritation of 
 the facial [Leube). Moos observed a profuse secretion of saliva on stimulating the chorda during 
 an operation on the tympanic cavity. 
 
 350. VIII. NERVUS ACUSTICUS.— Anatomical.— This nerve arises from two nuclei 
 [Stieda], whose ganglionic cells anastomose (Fig. 384, 8, 8', 8"). The nuclei lie in the broadest 
 part of the calamus scriptorius ; a process from a spinal centre reaches them (Boiler). The ante- 
 rior nucleus, which is connected with the portio intermedia Wrisbergii, appears to contain vasomotor 
 fibres. Part of its fibres run through the pedunculus cerebelli to the dentate body of the cerebellum ; 
 very probably they are connected with the regulation of the equilibrium (J 380). The white striae 
 
brenner's formula — the semicircular canals. 635 
 
 medullares, which run transversely across the floor of the fourth ventricle, are said to pass into the 
 pedunculus cerebelli of the opposite side. According to Meynert, fibres of the auditory nerve pass 
 in channels as yet undetermined from the cerebellum to the pedunculus cerebri, and ultimately to 
 the cortex of the brain, where their cortical centre lies in the temporo-sphenoidal lobes ($ 378, IV). 
 In the sheep and horse the two chief branches of the auditory nerve— the cochlear and vestibular 
 nerves — arise separately, which points to the independence of their functions yHorbaczewski) — 
 (Fig. 385, VII 6). In the course of the internal auditory meatus, the auditory and portio inter- 
 media of the facial exchange fibres, but the physiological significance of this is unknown. 
 
 Function. — The acusticus or auditory nerve has a double function: 1. It is 
 the nerve of hearing ; when stimulated, either at its origin, in its course, or at 
 its peripheral terminations, it gives rise to sensations of sound. Every injury, 
 according to its intensity and extent, causes hardness of hearing or even deafness. 
 
 2. Quite distinct from the foregoing is the other function, which depends upon 
 the semicircular canals, viz., that stimulation of the peripheral expansions in 
 the ampulla? influences the movements necessary for maintaining the equilibrium 
 of the body. 
 
 Brenner's Formula. — The relation of the auditory nerve to the galvanic current is very 
 important. In healthy persons, when there is closure at the cathode, there is the sensation of a 
 clang (or tone) in the ear, which continues with variations while the current is closed. When the 
 anode is opened, there is a feebler tone {Brenner's Normal Acoustic Formula). This clang coin- 
 cides exactly with the resonance fundamental tone of the sound-conducting apparatus of the ear 
 itself. ' 
 
 Pathological. — Increased sensibility of the auditory nerve in any part of its course, its centre, 
 or peripheral expansions causes the condition known as hyperakusis, which usually is a sign of 
 extensive increased nervous excitability, as in hysteria. When excessive, it may give rise to dis- 
 tinctly painful impressions, which condition is known as acoustic hyperalgia [Eulenburg). 
 Stimulation of the parts above named causes sensations of sound, the most common being the 
 sensation of singing in the ears, or tinnitus. This condition is often due to changes in the amount 
 of blood in the blood vessels of the ear — either anaemic or hypersemic stimulation. There is well- 
 marked tinnitus after large doses of quinine or salicin, due to the vasomotor effect of these drugs upon 
 the vessels of the labyrinth (JCirckner). Not unfrequently, in cases of tinnitus, the reaction due to 
 the galvanic current is often increased. More rarely there is the so-called "paradoxical reaction" 
 — i.e., on applying the galvanic current to one ear, in addition to the reaction in this ear, there is 
 the opposite result in the non-stimulated ear. In other cases of disease of the auditory nerve, noises 
 rather than musical notes are produced by the current ; stimulation, especially of the cortical 
 centre of the auditory nerve, chiefly in lunatics, may cause auditory delusions (J 378, IV). 
 According as the excitability of the auditory nerve is diminished or abolished, there is the condition 
 of nervous hardness of hearing (Hypakusis), or nervous deafness (Anakusis). 
 
 The Semicircular Canals of the Labyrinth. — Section or injury to these 
 canals does not interfere with hearing, but other important symptoms follow their 
 injury, such as disturbances of equilibrium due to a feeling of giddiness, espe- 
 cially when the injury is bilateral {Flourens). This does not occur in fishes 
 (Kieselbach). The pendulum-like movement of the head in the direction 
 of the plane of the injured canal is very characteristic. If the horizontal canal 
 is divided, the head (of the pigeon) is turned alternately to the right and left. 
 The rotation takes place, especially when the animal is about to execute a move- 
 ment : when it is at rest, the movement is less pronounced. The phenomenon 
 may last for months, and injury to the posterior vertical canal causes a well- 
 marked up and down movement or nodding of the head, the animal itself not 
 unfrequently falling forward or backward. Injury to the superior vertical canals 
 also causes pendulum-like vertical movements of the head, while the animal often 
 falls forward. When all the canals are destroyed, various pendulum-like move- 
 ments are performed, while standing is often impossible. Breur found that elec- 
 trical stimulation of the canals caused rotation of the head, while Landois, on 
 applying a solution of salt to the canals, observed pendulum-like movements, 
 which, however, disappeared after .a time. A 25 per cent, solution of chloral 
 dropped into the ear of a rabbit causes, after fifteen minutes, a similar destruction 
 of the canals {Vulpian). Section of the acoustic nerves within the cranium has 
 the same result (JBechterew). 
 
636 GIDDINESS, NYSTAGMUS. 
 
 Explanation. — Goltz regards the canals as organs of sense for ascertaining the equilibrium or 
 position of the head in space ; Mach, as an organ for ascertaining ihe movements of the head. 
 According to Goltz' s statical theory, every position of the head causes the endolymph to exert 
 the greatest pressure upon a certain part of the canals, and thus excites in a varying degree the 
 nerve terminations in the ampullae. According to Breuer, when the head is .rotated, currents are 
 produced in the endolymph of the canals, which must have a fixed relation to the direction and 
 extent of the movements of the head ; and these currents, therefore, when they are perceived, 
 afford a means of determining the movement of the head. The nervous end organs of the ampullae 
 are arranged for ascertaining this perception. If the semicircular canals are an apparatus— in fact, 
 "sense organs" [Goltz) — for the sensation of the equilibrium, and whose' function is to determine 
 the position or movements of the head, necessarily their destruction or stimulation must alter these 
 perceptions, and so give rise to abnormal movements of the head. Vulpian regards the rotation of 
 the head as due to strong auditory perceptions (?) in consequence of affections of the canals. 
 Bottcher, Tomaszewicz and Baginsky regard the injury to the cerebellum as the cause of the phe- 
 nomena. The pendulum-like movements, however, are so characteristic that they cannot be con- 
 founded with disturbances of the equilibrium which result from injury to the cerebellum. 
 
 [Kinetic Theory. — In 1875 Crum Brown pointed out that if a person be rotated passively, his 
 eyes being bandaged, he can, up to a certain point, indicate pretty accurately the amount of move- 
 ment, but after a time this cannot be done, and if the rotation, 
 as on a potter's wheel, be stopped, the sense of rotation con- 
 F IG. 389. tinues. Crum Brown suggested that currents were produced in 
 
 the endolymph, while the terminal hair cells lagged behind, and 
 were, in fact, dragged through ,the fluid. He pointed out that 
 the right posterior canal is in line with the left superior, and the 
 left posterior with the right superior, a fact which is readily ob- 
 served by looking from behind at a skull, with the semicircular 
 canals exposed (Fig. 389). He assumes that the canals are 
 paired organs, and that each pair is connected with rotation or 
 movement of the head in a particular direction.] 
 
 Giddiness. — This feeling of false impressions as 
 
 to the relations of the surroundings and consequent 
 
 Diagram of the disposition of the semi- movements of the body occurs especially during 
 
 and"kft C s"perior^ S Lp d aifd "rp' acquired changes in the normal movements of the 
 
 right and left posterior; le and" eyes, whether due to involuntary to and fro move- 
 
 RE, right and left external. ments Qf ^ eyebaUs (nyStagHlUS) Or tO paralysis 
 
 of some eye muscle. 
 
 Active or passive movements of the head or of the body are normally accom- 
 panied by simultaneous movements of both eyeballs, which are characteristic for 
 every position of the body. The general character of these "compensatory" 
 bilateral movements of the eyes consists in this, that during the various changes in 
 the position of the head and body the eyes strive to maintain their primary passive 
 position. Section of the aqueduct of Sylvius at the level of the corpora quadri- 
 gemina, of the floor of the fourth ventricle, of the auditory nucleus, both acustici, 
 as well as destruction of both membranous labyrinths, causes disappearance of 
 these movements; while, conversely, stimulation of these parts is followed by 
 bilateral associated movements of the eyeballs. 
 
 Compensatory movements of the eyeballs, under normal circumstances, may be 
 caused reflexly from the membranous labyrinth. Nerve channels, capable of ex- 
 citing reflex movements of both eyes, proceed from both labyrinths, and, indeed, 
 both eyes are affected from both labyrinths. These channels pass through the 
 auditory nerve to the centre (nuclei of the 3d, 4th, 6th and 8th cranial nerves), 
 and from the latter efferent fibres pass to the muscles of the eye (Hogyes). 
 
 Cyon found that stimulation of the horizontal semicircular canal was followed by horizontal nys- 
 tagmus ; of the posterior, by vertical, and of the anterior canal, by diagonal nystagmus. Stimula- 
 tion of one auditory nerve is followed by rotating nystagmus, and rotation of the body of the animal 
 on its axis toward the stimulated side. 
 
 Poisons. — Chloroform and other poisons enfeeble the compensatory movements of the eyeballs, 
 while nicotin and asphyxia suppress them, owing to their action on their nerve centre. 
 
 It is probable that the disturbances of equilibrium and the feeling of giddiness 
 which follow the passage of a galvanic current through the head between the mas- 
 
THE GLOSSOPHARYNGEAL NERVE. 637 
 
 toid processes, are also due to an action upon the semicircular canals of the laby- 
 rinth (§300"). Deviation of the eyeballs is produced by such a galvanic current 
 (Hitzig). The same result is produced when the two electrodes are placed in the 
 external auditory meatuses. 
 
 Pathological. — Meniere's Disease. — The feeling of giddiness, not unfrequently accompanied 
 by tinnitus, which occurs in Meniere's disease, must be referred to an affection of the nerves of the 
 ampullae or their central organs, or of the semicircular canals themselves. By injecting fluid vio- 
 lently into the ear of a rabbit, giddiness, with nystagmus and rotation of the head toward the side 
 operated on, are produced (Baginsky). In cases in man, where the tympanic membrane was 
 defective, Lucae, when employing the so-called ear-air douche at o.i atmosphere, observed abduction 
 of the eyeball with diplopia, giddiness, darkness in front of the eyes, while the respiration was 
 deeper "and accelerated. These phenomena must be due to stimulation or exhaustion of the ves- 
 tibular branch of the auditory nerve (Hogyes). In chronic gastric catarrh a tendency to giddiness 
 is an occasional symptom (Trousseau's gastric giddiness). This may, perhaps, be caused by stimu- 
 lation of the gastric nerves exciting the vasomotor nerves of the labyrinth, which must affect the 
 pressure of the endolymph. Analogous giddiness is excited from the larynx {Charcot) and from 
 the urethra (Erlenmeyer). 
 
 [Vertigo, or giddiness, is a very common symptom in disease, and may be produced by a great 
 many different conditions. It literally means "a turning." As Gowers points out, the most common 
 symptom is that the patient himself has a sense of movement in one or other direction; or objects 
 may appear to move before him ; and more rarely there is actual movement " commonly in the 
 same direction as the subjective sense of movement." It is sometimes due to a want of harmony 
 between the impressions derived from different sense organs or " contradictoriness of sensory impres- 
 sions" (Grainger Stewart), &s is sometimes felt on ascending or descending a stair, or by some 
 persons while standing on a high tower, constituting tower or cliff giddiness. One of the most 
 remarkable conditions is that called "Agoraphobia " (Benedikt, Westphat). The person can walk 
 quite well in a narrow lane or street, but when he attempts to cross a wide square he experiences a 
 feeling closely allied to giddiness. The giddiness of seasickness is proverbial, while some persons 
 • get giddy with waltzing or swinging. Besides occurring in Meniere's disease, it sometimes occurs 
 in locomotor ataxis and some cerebral and cerebellar affections, including cerebral anaemia. Very 
 distressing giddiness and headache are often produced by paralysis of some of the ocular muscles, 
 t. g., the external rectus. Defective or perverted ocular impressions, as well as similar auditory 
 impressions, may give rise to vertigo ; in the latter or labyrinthine form the vertigo may be very 
 severe. Severe vertigo is often accompanied by vomiting. A hard plug of ear wax may press on 
 the membrana tympani, and cause severe giddiness. The forms of dyspeptic giddiness and the 
 toxic forms due to the abuse of alcohol, tobacco, and some other drugs are familiar examples of this 
 condition.] 
 
 [Tinnitus Aurium, or subjective noises in the ear, is a very common symptom in disease of the 
 ear; the noise may be continuous or discontinuous, be buzzing, singing, or rumbling in character.] 
 
 351. IX. NERVUS GLOSSO-PHARVNGEUS.— Anatomical.— This nerve (Fig. 386, 
 9) arises from the nucleus of the same name, which consists partly of large cells (motor) and partly 
 of small cells (belonging to the gustatory fibres). The nucleus lies in the lower half of the fourth 
 ventricle, deep in the medulla oblongata, near the olive (Fig. 384). The nucleus is connected with 
 that of the vagus. A special root ascending from the spinal cord applies itself to the fibres, and 
 perhaps (like the spinal roots of the second and eighth nerves) serves for the production of spinal 
 reflexes (Roller). The fibres collect into two trunks, which afterward unite and leave the medulla 
 oblongata in front of the vagus. In the fossula petrosa it has on it the petrous ganglion, from 
 which, occasionally, a special part on the posterior twig is separated within the skull as the ganglion 
 of Ehrenritter. Communicating branches are sent from the petrous ganglion to the trigeminus, 
 facial (s and -), vagus and carotid plexus. From this ganglion also the tympanic nerve (A) ascends 
 vertically in the tympanic cavity, where it unites with the tympanic plexus This branch (§ 349, 4) 
 gives sensory fibres to the tympanic cavity and the Eustachian tube ; while, in the dog, it also carries 
 secretory fibres for the parotid into the small superficial petrosal nerve (Heidenhain — \ 145). 
 
 Function. — 1. It is the nerve of taste for the posterior third of the tongue, 
 the lateral part of the soft palate, and the glosso-palatine arch (compare § 422). 
 [This is denied by Gowers (p. 630).] 
 
 The nerve of taste for the anterior two-thirds of the tongue is referred to under the lingual (§ 347, 
 III, 4), and chorda tympani nerves (\ 349, 4). The glossal branches are provided with ganglia, 
 especially where the nerve divides at the base of the circurnvallate papillae (Remak, Kolliker, 
 Schwalbe, Stirling). The nerve ends in the circurnvallate papillae (Fig. 320, U), and the end organs 
 are represented by the taste bulbs (\ 422). 
 
 2. It is the sensory nerve for the posterior third of the tongue, the anterior 
 
638 THE CONNECTING AND OTHER BRANCHES OF THE VAGUS. 
 
 surface of the epiglottis, the tonsils, the anterior palatine arch, the soft palate, and 
 a part of the pharynx. From this nerve there may be discharged reflexly, move- 
 ments of deglutition, of the palate and pharynx ( Volkmann), which may pass into 
 those of vomiting (§ 158). These fibres, like the gustatory fibres, can excite a 
 reflex secretion of saliva (§ 145). 
 
 3. It is motor for the stylo-pharyngeus and middle constrictor of the pharynx 
 ( Volkmann) ; and, according to other observers, to the (?) glosso-palatinus (Hein) 
 and the (? ?) levator veli palatini and azygos uvulae (compare Spheno-palatine gang- 
 lion, § 347, II). It is doubtful whether the glosso-pharyngeal nerve is really a 
 motor nerve at its origin — -although Meynert, Huguenin, W. Krause, and Duval 
 have described a motor nucleus — or whether the motor fibres reach the nerve at 
 the petrous ganglion, through the communicating branch from the facial. 
 
 4. A twig accompanies the lingual artery ; this nerve, perhaps, is vaso-dilator for the lingual 
 blood vessels. 
 
 Pathological. — There are no satisfactory observations on man of uncomplicated affections of the 
 glosso-pharyngeal nerve. 
 
 352. X. NERVUS VAGUS. — Anatomical. — The nucleus from which the vagus arises 
 along with the ninth and eleventh nerve is in the ala cinerea in the lower half of the calamus scrip- 
 torius (Fig. 384, 10) [and it is very probably the representative of the cells of the vesicular column 
 of Clarke ({j 366).] It leaves the medulla oblongata by 10 to 15 threads behind the ninth nerve, 
 between the divisions of the lateral column, and has a ganglion (jugular) upon it in the jugular 
 foramen (Fig. 385, VIII). Its branches contain fibres which subserve different functions. 
 
 1. The sensory meningeal branch from the jugular ganglion accompanies the 
 vasomotor fibres of the sympathetic on the middle meningeal artery, and sends 
 fibres to the occipital and transverse sinus. 
 
 When it is irritated, as in congestion of the head and inflammation of the dura mater, it gives rise 
 to vomiting. 
 
 2. The auricular branch (from the jugular ganglion) receives a communicat- 
 ing branch from the petrous ganglion of the ninth nerve, traverses the canaliculus 
 mastoideus, crossing the course of the facial, with which it exchanges fibres whose 
 function is unknown. On its course it gives sensory branches to the posterior 
 part of the auditory meatus and the adjoining part of the outer ear. A branch 
 runs along with posterior auricular branch of the facial, and confers muscular 
 sensibility on the muscles. 
 
 When this nerve is irritated, either through inflammation or by the presence of foreign bodies in 
 the outer ear passage, it may give rise to vomiting. Stimulation of the deep part of the external 
 auditory meatus in the region supplied by the auricular branch causes coughing reflexly \_e . g., from 
 the presence of a pea in the ear] . Similarly, contraction of the blood vessels of the ear may be 
 caused reflexly (Snellen, Lovin). 
 
 The nerve is the remainder of a considerable branch of the vagus which exists in fishes and the 
 larvge of frogs, and runs under the skin along the side of the body. 
 
 3. The connecting branches of the vagus are: (1) A branch which directly 
 connects the petrous ganglion of the 9th with the jugular ganglion of the 10th ; its 
 function is unknown. (2) Directly above the plexus gangliiformis vagi, the vagus 
 is joined by the whole inner half of the spinal accessory. This nerve conveys to 
 the vagus the motor fibres for the larynx {Bischoff, i8j2), and the cervical part 
 of the oesophagus (which, according to Steiner, lie in the inner part of the nerve 
 trunk), as well as the inhibitory fibres for the heart {CI. Bernard). (3) The 
 plexus gangliiformis fibres, whose function is unknown, join the trunk of the vagus 
 from the hypoglossal, superior cervical ganglion of the sympathetic, and the cer- 
 vical plexus. 
 
 4. Pharyngeal Plexus. — The vagus sends one or two branches from the upper 
 part of the plexus gangliiformis to the pharyngeal plexus, where at the level of the 
 middle constrictor of the pharynx it is joined by the pharyngeal branches of the 
 9th nerve and those of the upper cervical sympathetic ganglion, near the ascending 
 pharyngeal artery, to form the pharyngeal plexus. The vagal fibres in this plexus 
 
SUPERIOR AND INFERIOR LARYNGEAL NERVES. 639 
 
 supply the three constrictors of the pharynx with motor fibres, while the tensor 
 palati {Otic ganglion, § 347, III) and levator of the soft palate (compare Spheno- 
 palatine ganglion, § 347, II) also receive motor (? sensory) fibres. Sensory 
 fibres of the vagus from the pharyngeal plexus supply the pharynx from the part 
 beneath the soft palate downward. These fibres excite the pharyngeal constric- 
 tors reflexly during the act of swallowing (§ 156). If stimulated very strongly 
 they may cause vomiting. (The sympathetic fibres of the oesophageal plexus give 
 vasomotor nerves to the oesophageal vessels ; for the oesophageal branches of the 
 9th nerve, see above.) 
 
 5. The vagus supplies two branches to the larynx, the superior and inferior 
 laryngeal. 
 
 (a) The superior laryngeal receives vasomotor fibres from the superior 
 cervical ganglion of the sympathetic. It divides into two branches, external and 
 internal : (1) The external branch receives vasomotor fibres from the same 
 source (they accompany the superior thyroid artery), and supply the cricothyroid 
 muscle with motor fibres and sensory fibres to the lower lateral portion of the 
 laryngeal mucous membrane. (2) The internal branch gives off sensory branches 
 only to the glosso-epiglottidean fold and the adjoining lateral region of the root 
 of the tongue, the aryepiglottidean fold, and to the whole anterior part of the lar- 
 ynx, except the part supplied by the external branch (Longet). Stimulation of 
 any of these sensory fibres causes coughing reflexly. Coughing is produced by 
 stimulation of the sensory branches of the vagus to the tracheal mucous membrane, 
 especially at the bifurcation, and also from the bronchial mucous membrane. 
 Coughing is also caused by stimulation of the auricular branch of the vagus, espe- 
 cially in the deep part of the external auditory meatus, of the pulmonary tissue, 
 especially when altered pathologically ; in pathological conditions (inflammation) 
 of the pleura (? certain changes in the stomach [stomach cough]), of the liver and 
 spleen [Naunyn). The coughing centre is said to lie on each side of the raphe, 
 in the neighborhood of the ala cinerea {Kohts~). Cases of violent coughing may, 
 owing to stimulation of the pharynx, be accompanied by vomiting as an associ- 
 ated movement (§ 120). 
 
 The cough (dog, cat) caused by stimulation of the trachea and bronchi occurs at once, and lasts 
 as long as the stimulus lasts ; in stimulation of the larnyx the first effect is inhibition of the respira- 
 tion accompanied by movements of deglutition, while the cough occurs after the cessation of the 
 stimulation (Kandarazky). 
 
 The superior laryngeal contains afferent fibres which, when stimulated, cause arrest of the res- 
 piration and closure of the rima glottidis {Rosenthal) — (see Respiratory centre, \ 368). Lastly, 
 fibres which are efferent and serve to excite the vasomotor centre, and are in fact, "pressor fibres" — 
 (see Vasomotor centre, \ 371, II). 
 
 (i) The inferior laryngeal (recurrent) bends on the left side around the arch 
 of the aorta, and on the right around the subclavian, and ascends in the groove 
 between the trachea and oesophagus, giving motor fibres to these organs, and the 
 lower constrictors of the pharynx, and passes to the larynx, to supply motor 
 fibres to all its muscles, except the cricothyroid. It also has an inhibitory action 
 upon the respiratory centre (see § 368). 
 
 A connecting branch runs from the superior laryngeal to the inferior (the anastomosis of Galen), 
 which occasionally gives off sensory branches to the upper half of the trachea (sometimes to the 
 larynx ?) ; perhaps, also, to the oesophagus (Longet), and sensory fibres (?) for the muscles of the 
 larynx supplied by the recurrent laryngeal. According to Francois Franck, sensory fibres pass by 
 this anastomosis from the recurrent into the superior laryngeal. According to Waller and Burck- 
 hard, the motor fibres of both laryngeal nerves are all derived from the accessorius ; while Chau- 
 veau maintains that the cricothyroid is an exception. 
 
 Stimulation of the superior laryngeal is painful, and causes contraction of 
 the cricothyroid muscle (while the other laryngeal muscles contract reflexly). 
 Section of both nerves, owing to paralysis of the cricothyroids, causes slight slow- 
 ing of the respirations (Sk/arek). In dogs the voice becomes deeper and coarser, 
 
640 
 
 CARDIAC BRANCHES OF THE VAGUS. 
 
 Fig. 390. 
 
 owing to diminished tension of the vocal cords {Longei). The larynx becomes 
 insensible, so that saliva and particles of food pass into the trachea and lungs, 
 without causing reflex contraction of the glottis or coughing, This excites " trau- 
 matic pneumonia," which results in death (Friedlandef). 
 
 Stimulation of the recurrent nerves causes spasm of the glottis. Section 
 of these nerves paralyzes the laryngeal muscles supplied by them, the voice be- 
 comes husky and hoarse (in the pig — Galen, Riolan, 1618) in man, dog, and cat ; 
 while rabbits retain their shrill cry. The glottis is small, with every inspiration 
 of the vocal cords approximate considerably at their anterior parts, while during 
 expiration they are relaxed and are separated from each other. Hence, the inspi- 
 ration, especially in young individuals whose glottis respiratoria is narrow, is dif- 
 ficult and noisy {Legallois) ; while the expiration takes place easily. After a few 
 days, the animal (carnivore) becomes more quiet, it respires with less effort, and 
 the passive vibratory movements of the vocal cords become less. Even after a 
 considerable interval, if the animal be excited, it is attacked with severe dyspncea, 
 which disappears only when the animal has become quiet again. Owing to paralysis 
 of the laryngeal muscles, foreign bodies are apt to enter the trachea, while the 
 paralysis renders difficult the first part of the process of swallowing in the oesoph- 
 ageal region. Broncho-pneumonia may be produced {Arnsperger). 
 
 6. The depressor nerve, which in the rabbit arises by one branch from the 
 superior laryngeal, and usually, also, by a second root from 
 the trunk of the vagus itself [runs down the neck in close 
 relation with the vagus, sympathetic, and carotid artery, 
 enters the thorax], and joins the cardiac plexus (Fig. 390, sc). 
 It is an afferent nerve, and when its central end is stimu- 
 lated [provided both vagi be divided], it diminishes the 
 energy of the vasomotor centre, and thus causes a fall of the 
 blood pressure (hence the name given to it by Cyon and 
 Ludwig, § 371, II). At the same time [if the vagus on the 
 opposite side be intact], its stimulation affects the cardio- 
 inhibitory centre, and thus reflexly diminishes the number of 
 heart beats. [Its stimulation also gives rise to pain, so that 
 it is the sensory nerve of the heart. If in a rabbit the vagi 
 be divided in the middle of the neck, and the central end 
 of the depressor nerve, which is the smallest of the three 
 nerves near the carotid, be stimulated, after a sho.rt time 
 there is no alteration of the heart beats, but there is a steady 
 fall of the blood pressure (Fig. 103), which is due to a reflex 
 inhibition of the vasomotor centre, resulting in a dilatation 
 of the blood vessels of the abdomen. Of course, if the vagi 
 be intact, there is a reflex inhibitory effect on the heart. It 
 is doubtful if the depressor comes into action when the heart 
 is over-distended. If it did, of course the blood pressure 
 would be reduced by the reflex dilatation of the abdominal 
 blood vessels.] 
 
 The depressor nerve is present in the cat {Bernhardt'), hedgehog 
 
 Scheme of the cardiac nerves C^**"*, Rover), rat and mouse; in the horse and in the man, fibres 
 
 in the rabbit. P, pons; analogous to the depressor re-enter the trunk of the vagus [Bernhardt, 
 
 M, medulla oblongata; Kreidmanti). Depressor fibres are also found in the rabbit in the trunk 
 
 ^•xTinferior-la^: « *' vagus [Dreshfeldt, Stelling). 
 
 7. The cardiac branches, as well as the cardiac plexus, 
 have been described in § 57. These nerves contain the 
 inhibitory fibres for the heart (Fig. 390, ic — cardio-in- 
 hibitory — Edward Weber, November, 1845 ; Budge, independently in May, 
 1846), also sensory fibres for the heart [in the frog {Budge}, and partly in 
 
 Vac 
 
 geal; s c, superior car- 
 diac or depressor; ic, 
 inferior cardiac or car- 
 dio-inhibitory ; H, heart. 
 
PNEUMONIA AFTER SECTION OF THE VAGI. 641 
 
 mammals (GWte)]. Lastly, in some animals the heart receives some of the 
 accelerating fibres through the trunk of the vagus. Feeble stimulation of the 
 vagus occasionally causes acceleration of the beats of the heart {Schiff, Moleschott, 
 Gianuzzi). [This occurs when the vagus contains accelerator fibres.] In an 
 animal . poisoned with nicotin or atropin, which paralyzes the inhibitory fibres of 
 the vagus, stimulation of the vagus is followed by acceleration of the heart beats 
 {Schiff, Schmiedeberg) [owing to the unopposed action of any accelerated fibres 
 that may be present in the nerve, e.g., of the frog]. 
 
 8. The pulmonary branches of the vagus join the anterior and posterior 
 pulmonary plexuses. The anterior pulmonary plexus gives sensory and motor 
 fibres to the trachea, and runs on the anterior surface of the branches of the 
 bronchi into the lungs. The posterior plexus is formed by three to five large 
 branches from the vagus, near the bifurcation of the trachea, together with 
 branches from the lowest cervical ganglion of the sympathetic and fibres from the 
 cardiac plexus. The plexuses of opposite sides exchange fibres, and branches are 
 given off which accompany the bronchi in the lungs. Ganglia occur in the 
 course of the pulmonary branches in the frog {Arnold, W. Stirling) [newt — W. 
 Stirling; and in mammals {Remak, Egerow, W. Stirling)\, in the larynx \Cock, 
 W. Stirling^, in the trachea and bronchi [ W. Stirling, Kandarazki\ Branches 
 proceed from the pulmonary plexus to the pericardium and the superior vena cava 
 {Luschka, Zuckerkandl). 
 
 The functions of the pulmonary branches of the vagus are — (i) they supply 
 motor branches to the smooth muscles of the whole bronchial system (§ 106 — 
 Roy and Graham Brown); (2) they supply a small part of the vasomotor nerves 
 of the pulmonary vessels {Schiff), but by far the largest number of these nerves 
 (? all) is supplied from the connection with the sympathetic (in animals from the 
 first dorsal ganglion) — {Brown-Sequard, A. JFick, Badoud, Lichtheim) ; (3) they 
 supply sensory (cough-exciting) fibres to the whole bronchial system, and to the 
 lungs; (4) they give afferent fibres, which, when stimulated, diminish the activity 
 of the vasomotor centre, and thus cause a fall of the blood pressure during forced 
 expiration ; (5) and similar fibres which act upon the inhibitory centre of the 
 heart, and so influence it as to accelerate the pulse beats (§ 369, II). Simultaneous 
 stimulation of 4 and 5 alters the pulse rhythm {Sommerbrodt) ; (6) they also con- 
 tain afferent fibres from the pulmonary parenchyma to the medulla oblongata, 
 which stimulate the respiratory centre. [These fibres are continually in action], 
 and consequently section of both vagi is followed by diminution of the number 
 of respirations ; the respirations become deeper at the same time, while the same 
 volume of air is changed {Valentin). Stimulation of the central end of the vagus 
 again accelerates the respirations ( Traube, J. Rosenthal). Thus labored and diffi- 
 cult respiration is explained by the fact that the influences conveyed by these fibres 
 which excite the respiratory centre reflexly are cut off; so it is evident that cen- 
 tripetal or afferent impulses proceeding upward in the vagus are intimately con- 
 cerned in maintaining normal reflex respiration ; after these nerves are divided, 
 conditions exciting the respiratory movements must originate directly, especially 
 in the medulla oblongata itself (§ 368). 
 
 Pneumonia after Section of both Vagi. — The inflammation which follows section of both 
 vagi has attracted the attention of many observers since the time of Valsalva, Morgagni (1740),. 
 and Legallois (1812). In offering an explanation of this phenomenon, we must bear in mind the 
 following considerations : (a) Section of both vagi is followed by loss of motor power in the 
 muscles of the larynx, as well as the sensibility of the larynx, trachea, bronchi, and the lungs, pro- 
 vided the section be made above the origin of the superior laryngeal nerves. Hence, the glottis is 
 not closed during swallowing, nor is it closed reflexly when foreign bodies (saliva, particles of food, 
 irrespirable gases) enter the respiratory passages. Even the reflex act of coughing, which, under 
 ordinary circumstances, would get rid of the offending bodies, is abolished. Thus, foreign bodies 
 may readily enter the lungs, and this is favored by the fact that, owing to the simultaneous paralysis 
 of the oesophagus, the food remains in the latter for a time, and may therefore easily enter the 
 larynx. That this constitutes one important factor was proved by Traube, who found that the pneu- 
 
 41 
 
642 OESOPHAGEAL AND GASTRIC PLEXUSES. 
 
 monia was prevented when he caused the animals to respire by means of = tube inserted into the 
 trachea through an aperture in the neck. If, on the contrary, only the motor recurrent nerves 
 were divided and the oesophagus ligatured, so that in the process of attempting to swallow food 
 must necessarily enter the respiratory passages, " traumatic pneumonia " was the invariable re- 
 sult (Traube, O. Frey). (b) A second factor depends on the circumstance that, owing to the 
 labored and difficult respiration, the lungs become surcharged ■with blood, because during the long 
 time that the thorax is distended, the pressure of the air within the lungs is abnormally low. This 
 condition of congestion, or abnormal filling of the pulmonary vessels with blood, is followed by 
 serous exudation (pulmonary oedema), and even by exudation of blood and the formation of pus in 
 the air vesicles (Prey). This same circumstance favors the entrance of fluids through the glottis 
 (\ 352, b). The introduction of a tracheal cannula will prevent the entrance of fluids and the 
 occurrence of inflammation. It is probable that a partial paralysis of the pulmonary vasomotor 
 nerves may be concerned in the inflammation, as this conduces to an engorgement of the pulmonary 
 capillaries, (c) Lastly, it is of consequence to determine whether trophic fibres are present in the 
 vagus, and which may influence the normal condition of the pulmonary tissues. According to 
 Michaelson, the pneumonia which takes place immediately after section of the vagi occurs especially 
 in the lower and middle lobes ; the pneumonia which follows section of the recurrents occurs more 
 slowly, and causes catarrhal inflammation, especially in the upper lobes. Rabbits, as a rule, die 
 within twenty-four hours, with all the symptoms of pneumonia; when the above-mentioned pre- 
 cautions are taken they may live for several days. Dogs may live for a long time. If the gth, 
 10th, and 12th nerves be torn out on one side in a rabbit, death takes place from pneumonia ( Griin- 
 hagen). In birds, bilateral section of the vagi is not followed by pneumonia (Blainville, Bill- 
 roth'), because the upper larynx remains capable of closing firmly — death takes place in eight to 
 ten days with the symptoms of inanition (Einbrodt, Zander, v. Anrep), while the heart under- 
 goes fatty degeneration (Eichhorsf), and so do the liver, stomach, and muscles (v. Anrep). 
 According to Wassilieff, the heart shows cloudy swelling and slight wax -like degeneration. Frogs, 
 which at every respiration open the glottis, and close it during the pause, die of asphyxia. Section 
 of the pulmonary branches has no injurious effect (Bidder). 
 
 9. The oesophageal plexus is formed principally by branches from the vagus 
 above the inferior laryngeal, from the pulmonary plexus and below from the trunk 
 itself. This plexus supplies the oesophagus with motor power (§ 156), the sen- 
 sibility which is present only in the upper part, and it also supplies fibres capable 
 of exciting reflex actions. 
 
 10. The gastric plexus consists of (a) the anterior (left) termination of 
 the vagus, which supplies fibres to the oesophagus and courses along the small 
 curvature, and sends a few fibres through the portal fissure into the liver; 
 (b) the posterior (right) vagus, after giving off a few fibres to the oesophagus, 
 takes part in the formation of the gastric plexus to which (c) sympathetic fibres 
 are added at the pylorus. Section of the vagi is followed by hyperemia of 
 the gastric mucous membrane (Panum, Pincus), but it does not interfere 
 with digestion (Bidder and Schmidt), even when it is performed at the cardia 
 (Kritzler, Schiff). 
 
 11. About two-thirds of the right vagus on the stomach joins the cceliac 
 plexus, and from it branches accompany the arteries to the liver, spleen, pan- 
 creas, duodenum, kidney, and suprarenal capsules. The vagus supplies motor 
 fibres to the stomach, which belong to the root of the vagus itself and not to the 
 accessorius (Stilling, Bischoff, Chauveau). The gastric branches also contain 
 afferent fibres, which, when stimulated, cause reflexly a secretion of saliva (§ 145). 
 It is undetermined whether they also cause vomiting. For the effect of the vagus 
 upon the movements of the intestine (see § 161). According to some ob- 
 servers, stimulation of the vagus is followed by movements of the large as well as 
 of the small intestine (Stilling, Kupffer, C. Ludwig, RemaK). Stimulation of the 
 peripheral end of the vagus causes contraction of the smooth muscular fibres in 
 the capsule and trabeculse of the spleen (in the rabbit and dog, § 103). Stimula- 
 tion of the vagus at the cardia causes increase in the secretion of urine with 
 dilatation of the renal vessels, while the blood of the renal vein becomes more 
 arterial (CI. Bernard). According to Rossbach and Quellhorst, a few vasomotor 
 fibres are supplied by the vagus to the abdominal organs, while the greatest num- 
 ber comes from the splanchnic. According to CEhl, efferent (centrifugal) motor 
 fibres run in the vagus (dog) direct to bladder, as well as afferent fibres whose 
 
REFLEX EFFECTS OF STIMULATION OF THE VAGUS. 643 
 
 stimulation causes reflex contraction of the bladder. So far, this observation has 
 not been confirmed. 
 
 12. Reflex Effects. — The vagus and its branches contain fibres, some of 
 which have been referred to already, which act reflexly (afferent) upon certain 
 nervous mechanisms. 
 
 (a) On the vasomotor centre there act (a) pressor fibres (especially in both laryngeal nerves), 
 whose stimulation is followed by a reflex contraction of the arterial blood channels, and thus cause 
 a rise of the blood pressure ; (b) depressor fibres (in the depressor or the vagus itself), which have 
 exactly an opposite effect. (This subject is specially referred to under the head of the Vasomotor 
 nerve centre, \ 371.) 
 
 (b) On the respiratory centre there act (a) fibres (pulmonary branches) whose stimulation is 
 followed by acceleration of the respiration ; and (b) inhibitory fibres (in both laryngeals), whose 
 stimulation is followed by slowing or arrest of the respiration. (See Respiratory centre, \ 368.) 
 
 (c) On the Cardio-inhibitory System. — [When the central end of one vagus is stimulated, 
 provided the other vagus is intact, the heart may he arrested reflexly in the diastolic phase.] Mayer 
 and Pribram observed that sudden distention of the stomach caused slowing and even arrest of the 
 heart, while at the same time there was contraction of the arteries of the medulla oblongata and 
 increase of the blood pressure. 
 
 (d) On the Vomiting Centre. — This centre may be affected by stimulation of the central end 
 of the vagus, and, as already mentioned, by stimulation of many afferent fibres in the vagus (\ 158). 
 
 (e) On the Pancreatic Secretion. — Stimulation of the central end of the vagus is followed by 
 arrest of this secretion (\ 171). 
 
 (/) According to CI. Bernard, there are fibres present in the pulmonary nerves, which, when 
 they are stimulated, increase reflexly the formation of sugar in the liver, perhaps through the 
 hepatic branches of the vagus. 
 
 Unequal Excitability. — The various branches of the vagus are not all endowed with the same 
 degree of excitability. If the peripheral end of the vagus be stimulated first of all with a weak 
 stimulus, the laryngeal muscles are first affected, and afterward the heart is slowed {Rutherford ). 
 If the central end be stimulated with feeble stimuli, the " excito-respiratory " fibres are exhausted 
 before the " inhibito-respiratory " (Burkarl). According to Steiner, the various fibres are so 
 arranged in the vagus that the afferent fibres lie in the outer, and the efferent in the inner, half of 
 the trunk, in the cervical region. 
 
 Pathological. — Stimulation or paralysis in the area of the vagus must necessarily present a very 
 different picture according as the affection is referred to the whole trunk or only to some of its 
 branches, or whether the affection is unilateral or bilateral. Paralysis of the pharynx and 
 oesophagus, which is usually of central or intracranial origin, interferes with or abolishes deglu- 
 tition, so that when the oesophagus becomes filled with food there is difficulty of breathing, and the 
 food may even pass into the nasal cavities. A peculiar sonorous gurgling is occasionally heard in 
 the relaxed canal (deglutatio sonora). In incomplete paralysis the act of deglutition is delayed 
 and rendered more difficult, while large masses are swallowed more easily than small ones. 
 Increased contraction and spasmodic stricture of the oesophagus are referred to under the phe- 
 nomena of general nervous excitability (\ 186). 
 
 Spasm of the laryngeal muscles causes spasmodic closure of the glottis (Spasmus glotlidis). 
 This condition is most apt to occur in children, and takes place in paroxysms, with symptoms of 
 dyspnoea and crowing inspiration ; if the case be very severe, there may be muscular contractions 
 (of the eye, jaw, digits, etc.). The symptoms are very probably due to the reflex spasms which 
 may be discharged from the sensory nerves of several areas (teeth, intestine, skin). The impulse 
 is conducted along the sensory nerves proceeding from these areas to the medulla oblongata, where 
 it causes the discharge of the reflex mechanism which produces the above-mentioned results. 
 There may be spasm of the dilators of the glottis (Frantzel) and other laryngeal muscles. 
 
 Stimulation of the sensory nerves of the larynx, as is well known, produces coughing. If the 
 stimulation be very intense, as in whooping-cough, the fibres lying in the laryngeal nerves, which 
 inhibit the respiratory centre, may also be stimulated; the number of respirations is diminished 
 and ultimately the respiration ceases, the diaphragm being relaxed : while, with the most intense 
 stimulation, there may be spasmodic expiratory arrest of the respiration with closure of the glottis, 
 which may last for fifteen seconds. Paralysis of the laryngeal nerves, which causes disturbances 
 of speech, has been referred to in \ 313. In bilateral paralysis of the recurrent nerves, in conse- 
 quence of tension upon them due to dilatation of the aorta and the subclavian artery, a consider- 
 able amount of air is breathed out, owing to the futile efforts which the patient makes in trying to 
 speak; expectoration is more difficult, while violent coughing is impossible (v. Ziemssen). Attacks 
 of dyspnoea occur just as in animals, if the person make violent efforts. Some observers (Salter 
 Bergson) have referred the asthma nervosum paroxysms, which last for a quarter of an hour or 
 more, and constitute asthma bronchiole, to stimulation of the pulmonary plexus, causing spasmodic 
 contraction of the bronchial muscle (\ 106). Physical investigation during the paroxysms reveals 
 nothing but the existence of some rhonchi ($ 117). If this condition is really spasmodic in its 
 
644 THE SPINAL ACCESSORY NERVE. 
 
 nature (? of the vessels), it must be usually of a reflex character ; the afferent nerves may be those 
 of the lung, skin or genitals (in hysteria). Perhaps, however, it is due to a temporary paralysis of 
 the pulmonary nerves (afferent), which excite the respiratory centre (excito-respiratory). 
 
 Stimulation of the cardiac branches of the vagus may cause attacks of temporary suspension of 
 the cardiac contractions, which are accompanied by a feeling of great depression and of impending 
 dissolution, with occasionally pain in the region of the heart. Attacks of this sort may be pro- 
 duced reflexly, e.g., by stimulation or irritation of the abdominal organs (as in the experiment of 
 Goltz of tapping the intestines). Hennoch and Silbermann observed slowing of the action of the 
 heart in children suffering from gastric irritation. Similarly, the respiration may be affected reflexly 
 through the vagus, a condition described by Hennoch as asthma dyspepticum. In cases of 
 intermittent paralysis of the cardiac branches of the vagus we rarely find acceleration of the pulse 
 above 160 {Riegel), 200 ( Tuczek, L. Longer, Weil) ; even 240 pulse beats per minute have been 
 recorded (Kuppert), and in such cases the beats vary much in rhythm and force, and they are very 
 irregular. These cases require to be more minutely analyzed, as it is not clear how much is due to 
 paralysis of the vagus and how much to the action of the accelerating mechanism of the heart. 
 Little is known of affections of the intra-abdominal fibres of the vagus. It seems that the sensory 
 branches of the stomach do not come from the vagus. If the trunk of the vagus or its centre be 
 paralyzed, there are labored, deep, slow respirations, such as follow section of both vagi ( Guttmann). 
 
 353. XI. NERVUS ACCESSORIUS WILLISII.— Anatomical.— This nerve arises 
 by two completely separate roots; one from the accessorius nucleus of the medulla oblongata 
 (Fig. 384, 11), which is connected with the vagus nucleus; while the other root arises between the 
 anterior and posterior nerve roots from the spinal cord, usually between the 5th and 6th cervical 
 vertebrae. In the interior of the spinal cord its fibres can be traced to an elongated nucleus lying 
 on the outer side of the anterior cornu, as far downward as the 5th cervical vertebra. Near the 
 jugular foramen both portions come together, but do not exchange fibres ( H 'oil); both roots after- 
 ward separate from each other to form two distinct branches, the anterior (inner), which arises 
 from the medulla oblongata, passing en masse into the plexus gangliiformis vagi. This branch sup- 
 plies the vagus with most of its motor fibres (compare \ 352, 3), and also its cardio-inhibitory 
 fibres. If the accessorius be pulled out by the root in animals, these heart fibres undergo degenera- 
 tion. If the trunk of the vagus be stimulated in the neck four to five days after the operation, the 
 action of the heart is no longer arrested thereby [owing to the degeneration of the cardio-inhibitory 
 fibres] ( Waller, Schiff, Daszkiewicz, Heidenhain) ; according to Heidenhain, the heart-beats are 
 accelerated immediately after pulling out the nerve. [The upper cervical metameres or segments 
 give origin not only to the anterior and posterior roots of the corresponding nerve roots, but between 
 these roots arise the roots of the spinal accessory nerve. This nerve contains /«?£? medullated nerve 
 fibres andy?»« medullated fibres such as characterize the visceral branches of the thoracic and sacral 
 regions [\ 356). The nerve passes by the jugular ganglion of the vagus, then divides into the 
 external and internal branch. All the large fibres pass into the external branch, which, along with 
 branches from the cervical plexus, supply the sterno-mastoid and trapezius. The internal branch, 
 composed of small fibres, passes into the ganglion of the trunk of the vagus. Gaskell therefore 
 regards the internal branch " as formed by the rami viscerales of the upper cervical and vagus 
 nerves.' ' These fine medullated nerve fibres probably arise from the cells of the posterior vesicular 
 column of Clarke. The motor fibres to the trapezius and sterno-mastoid arise from the cells of the 
 lateral horn of gray matter.] 
 
 The external branch arises from the spinal roots. This nerve communicates 
 with the sensory branches of the posterior root of the 1st, more rarely of the 
 2d cervical nerve, and these fibres supply sensibility to the muscles ; it then turns 
 backward above the transverse process of the atlas, and terminates as a motor 
 nerve in the sterno-mastoid and trapezius (Ga/en, Valentin, Volkmanri). The latter 
 muscle usually receives motor fibres also from the cervical plexus (Fig. 386). 
 
 The external branch communicates with several cervical nerves. These fibres either participate 
 in the innervation of the above-named muscles or the accessorius returns part of the sensory fibres 
 supplied by the posterior roots of the two upper cervical nerves. 
 
 Pathological. — Stimulation of the outer branch causes tonic or clonic spasm of the above-named 
 muscles, usually on one side. If the branch to the sterno-mastoid be affected alone, the head is 
 moved with each clonic spasm. If the affection be bilateral, the spasm usually takes place on oppo- 
 site sides alternately, while it is rare to have it on both sides simultaneously. In spasm of the 
 trapezius the head is drawn backward and to the side. Tonic contraction of the flexors of the 
 head causes the characteristic position of the head known as caput obstipum (spasticum) or wry- 
 neck. In paralysis of one of these muscles the head is drawn toward the sound side (torticollis 
 paralyticus). Paralysis of the trapezius is usually only partial. 
 
 Paralysis of the whole trunk of the spinal accessory (usually caused by central conditions), 
 besides causing paralysis of the sterno mastoid and trapezius, also paralyzes the motor branches of 
 the vagus already referred to (£rb, Fr&nkel, Holt). 
 
THE SPINAL NERVES. 64 ') 
 
 354. XII. NERVUS HYPOGLOSSUS.— Anatomical.— It arises from two large-celled 
 nuclei within the lowest part of the calamus scriptorius, and one adjoining small-celled nucleus 
 {Roller), while additional fibres come from the brain ((! 378), and also perhaps from the olive (Fig. 
 384, 12). It springs by 10 to 15 twigs in a line with the anterior roots of the spinal nerve (Fig. 385, 
 IX). In its development part of the hypoglossal behaves as a spinal nerve (Froriep). 
 
 Function. — It is motor to all the muscles of the tongue, including the genio- 
 hyoid and thyro-hyoid. 
 
 Connections. — The trunk of the hypoglossal is connected with — (1 ) the superior cervical ganglion 
 of the sympathetic, which supplies it with vasomotor fibres for the blood vessels of the tongue. After 
 section of the hypoglossal and lingual nerves, the corresponding half of the tongue becomes red 
 and congested [Schiff). (2) There is also a branch from the plexus gangliiformis vagi, its small 
 lingual branch to the commencement of the hypoglossal arch. These fibres supply the hypoglossal 
 with sensory fibres for the muscles of the tongue, for even after section of the lingual the tongue still 
 possesses dull sensibility. It is uncertain whether fibres with a similar .function are partly derived 
 from the cervical nerves or from the anastomosis which takes place with the lingual. (3) It is 
 united with the upper cervical nerves by means of the loops known as the ansa hypoglossi. These 
 connecting fibres run in the descendens noni to the sterno-hyoid, omo-hyoid and sterno-thyroid. Cer- 
 vical fibres do not, as a rule, enter the tongue; stimulation of the root of the hypoglossal acts upon 
 the above-named muscles only very rarely and to a very slight extent (Volkmann). (Compare 
 I 297, 3, and I 336, III.) 
 
 Bilateral section of the nerve causes complete motor paralysis of the tongue. 
 Dogs can no longer lap ; they bite the flaccid tongue. Frogs, which seize their 
 prey with the tongue, must starve ; when the tongue hangs from the mouth, it 
 must prevent the closure of the mouth, so that these animals must die from 
 asphyxia, as air is pumped into the lungs only when the mouth is closed. 
 
 Pathological. — Paralysis of the hypoglossal (glossoplegia), which is usually central in its 
 origin, causes disturbance of speech (§ 319). [In unilateral palsy the tongue lies in the mouth in 
 its normal position, but the base is more prominent on the paralyzed side. When the tongue is 
 protruded it passes to the sound side by the genio hyoglossus ($ 155).] Paralysis of the tongue 
 also interferes with mastication, the formation of the bolus in the mouth, and deglutition in the 
 mouth. Owing to the imperfect movements of the tongue, taste is imperfect, and the singing of 
 high notes and the falsetto voice, which require certain positions of the tongue, appear to be impos- 
 sible (Bennati). 
 
 Spasm of the tongue, which causes aphthongia ($ 318), is usually reflex in its origin, and is 
 extremely rare. Idiopathic cases of spasm of the tongue have been described; the seat of the irri- 
 tation lay either in the cortex cerebri or in the oblongata (Berger, E. Remak). For Pseudo-motor 
 Action, p. 632. 
 
 355. THE SPINAL. NERVES. — Anatomical. — The thirty-one pairs of spinal nerves arise 
 by means of a posterior root (consisting of a few large rounded bundles) from the sulcus between 
 the posterior and lateral columns of the spinal cord, and by means of an anterior root (consisting 
 of numerous fine flat strands), from the furrow between the anterior and lateral columns. The 
 posterior roots, with the exception of the 1st cervical nerve, are the larger. Occasionally the roots 
 on opposite sides are not symmetrical; one or other root, or even a whole nerve, may be absent 
 from the dorsal region [Adamkiewicz). On the posterior root is the spindle shaped spinal gan- 
 glion (J 321, II, 3), which is occasionally double on the lumbar and sacral nerves Beyond the 
 ganglion the two roots unite to form within the spinal canal the mixed trunk of a spinal nerve. 
 The branches of the nerve trunk invariably contain fibres coming from both roots. The number of 
 fibres in the nerve trunk is exactly the same as in the two roots; hence, we must conclude that the 
 nerve cells in the spinal ganglion are intercalated in the course of the fibres ( Gaule and Birge). 
 
 [Structure of a Spinal Ganglion. — The ganglion is invested by a thin, firmly adherent sheath 
 of connective tissue, which sends processes into the swelling, and is continuous with the sheaths of 
 the nerve entering and leaving the ganglion (Fig. 391, c). A longitudinal section of such a gan- 
 glion exhibits the cells arranged in groups, with strands of nerve fibres coursing longitudinally 
 between them (Fig. 391, a, b). The nerve cells are usually globular in form, with a distinct capsule 
 lined with epithelium, and the cell substance itself contains a well-defined nucleus with ■- nuclear 
 envelops and a nucleolus. The capsule of the cell is continuous with the sheath of Schwann of a 
 nerve fibre. The exact relation between the nerve fibres and the nerve cells is difficult to establish, 
 but it is probable that each nerve cell is connected with a nerve fibre. In the spinal ganglia of the 
 vertebrates above fishes, and also in the Gas^erian ganglion, cells are fuund with a single process or 
 fibre attached to them, the nerve-fibre process not unfrequently coiling a few times within the cap- 
 sule. This process, after emerging from the capsule, becomes coated with myelin, and usually 
 soon divides at a node of Ranvier (Fig. 341, /). Ranvier, who first observed this arrangement, 
 described it as a T-shaped fibre. These nerve cells with T-shaped fibres have been observed in the 
 
646 
 
 RECURRENT SENSIBILITY. 
 
 spinal ganglia of all vertebrates above fishes, in the Gasserian and geniculate ganglia, as well as in 
 the jugular and cervical ganglia of the vagus. In fishes the nerve cells of the spinal ganglia are 
 bipolar (Fig. 335, 4).] 
 
 Bell's Law. — Sir Charles Bell discovered (1811) that the anterior roots of 
 the spinal nerves are motor, the posterior are sensory. 
 
 Recurrent Sensibility. — Magendie discovered (1822) the remarkable fact 
 that sensory fibres are also present vs\ the anterior roots, so that their stimulation 
 causes pain. This is due to the fact that sensory fibres pass into the anterior root 
 after the two roots have joined, and these fibres run in the anterior root in a 
 centripetal direction (Schiff, CI. Bernard). The sensibility of the anterior root 
 is abolished at once by section of the posterior root. This condition is called 
 "recurrent sensibility" of the anterior root. When the sensibility of the 
 anterior root is abolished, so is the sensibility of the surface of the spinal cord 
 in the neighborhood of the root. A long time after section of the anterior, and 
 when the degeneration phenomena have had time to develop (§ 325), a few non- 
 degenerated sensory fibres are always to be found in the central stump {Schiff, 
 Vulpiari). Schiff found that, in cases where the motor fibres had undergone 
 degeneration, there were always non-degenerated -fibres to be found in the 
 anterior root, which passed into the membranes of the spinal cord. The sensory 
 fibres pass into the motor root, either at the angle of union of the roots, or in 
 
 Fig. 391. 
 
 Longitudinal section of a spinal ganglion, u, nerve fibre, i, nerve cells, c, capsule. 
 
 the plexus, or in the region of the peripheral terminations. Sensory fibres enter 
 many of the branches of the motor cranial nerves at their periphery^, and after- 
 ward run in a centripetal direction (p. 632). Even into the trunks 'of sensory 
 nerves, sensory branches of other sensory nerves may enter. This explains the 
 remarkable observation, that after section of a nerve trunk (e.g., the median), 
 its peripheral terminations still retain their sensibility (Arloing and Tripier). 
 The tissue of the motor and sensory nerves, like most other tissues of the body, 
 is provided with sensory nerves (Nervi nervorum, p. 565). 
 
 [It does not follow that section of a peripheral cutaneous nerve will cause anaesthesia in the part 
 to which it is distributed; in fact, one of the principal nerve trunks of the brachial plexus may be 
 divided without giving rise to complete anaesthesia in any part of the area of distribution of the 
 sensory branches of the nerve, and even if there be partial or complete cutaneous anaesthesia it is 
 much less in extent than corresponds to the anatomical area of distribution. The anaesthetic area 
 tends to become smaller in extent (Ross). Thus there is not complete independence in the distri- 
 bution of these' nerves. These results are explained by the anastomosis between branches of nerves, 
 the exchange of fibres in the terminal networks, while some sensory fibres enter the peripheral 
 parts of a nerve and run centripetally, perhaps being distributed to the skin and conferring recurrent 
 sensibility on the peripheral part of the nerve.] 
 
 Relative Position of Motor and Sensory Fibres. — In embryos (rabbit) the motor fibres stain 
 more deeply with carmine than the sensory fibres, so that their position in the peripheral nerves of 
 
DEDUCTION FROM BELL S LAW. 
 
 647 
 
 distribution may thereby be made out. In the anterior branch of a spinal nerve, the sensory fibres 
 lie in the outer part of the branch, the motor in the inner part ; while this relation is reversed in the 
 posterior root (Z. Lowe). 
 
 Deduction from Bell's Law. — Careful observation of the effects of section 
 of the roots of the spinal nerves (Magendie, 1822), as well as the discovery of the 
 reflex relation of the stimulation of the sensory roots to the anterior, constituting 
 
 Fig- 393- 
 
 Fig. 392. 
 
 I cl 
 
 ,i9 
 
 10 me 
 Distribution of the cutaneous nerves of the arm. 
 A, dorsal surface;/ sc, supra-clavicular ; 2 ax , 
 axillary ; j cps, superior posterior cutaneous ; 
 4 cmd, median cutaneous; 5cpi t inferior pos- 
 terior cutaneous ; b cm, median cutaneous; 7 
 cl, lateral cutaneous ; 8 u, ulnar ; g ra, radial ; 
 jo me, median ; B , volar surface ; / sc, supra- 
 clavicular ; 2 ax, axillary ; 3 cmd, internal 
 cutaneous; 4 cl, lateral cutaneous ; 5 cm, cu- 
 taneous medius ; 6 me, median ; 7 it, ulnar. 
 
 ...^.A 
 
 Distribution of the cutaneous nerves of the leg 
 (after Henle). A. Anterior surface — 1, crural 
 nerve ; 2, external lateral cutaneous ; 3, ilio- 
 inguinal; 4, lumbo-inguinal ; 5, external sper- 
 matic ; 6, posterior cutaneous ; 7, obturator ; 
 8, great saphenous ; 9, communicating pero- 
 neal ; io, superficial peroneal ; 1 1 , deep pero- 
 neal ; iz, communicating tibial. B. Posterior 
 surface — 1, posterior cutaneous; 2, external 
 femoral cutaneous; 3, obturator; 4, median 
 posterior femoral cutaneous ; 5, communicat- 
 ing peroneal ; 6, great saphenous ; 7, commu- 
 nicating tibial ; 8, plantar cutaneous ; 9, me- 
 dian plantar ; zo, lateral plantar. 
 
 reflex movements {Marshall Hall, Johannes Mutter, 1832), enable us to deduce 
 the following conclusions from Bell's law : r. At the moment of section of the 
 anterior root, there is a contraction in the muscles supplied by this root. 2. 
 There is at the same time a sensation of pain due to the "recurrent sensibility." 
 3. After the section, the corresponding muscles are paralyzed. 4. Stimulation of 
 
648 FUNCTIONS OF THE ANTERIOR SPINAL ROOTS. 
 
 the peripheral trunk of the anterior root (immediately after the operation) causes 
 contraction of the muscles, and eventually pain, owing to the recurrent sensibility. 
 5. Stimulation of the central end is without effect. 6. The peripheral end of the 
 motor nerves degenerates within a short time (§ 325, 4). 7. The central end 
 degenerates somewhat later (§ 325, 3). 8. The sensibility of the paralyzed parts 
 is retained completely. 9. At the moment of section of the posterior root 
 there is severe pain. 10. At the same time movements are discharged reflexly. 
 11. After the section all parts supplied by the divided roots are devoid of sensi- 
 bility. 12. Stimulation of the peripheral trunk of the divided nerve is without 
 effect. 13. Stimulation of the central end causes pain and reflex movements. 
 14. With reference to the degeneration of the peripheral end of the sensory fibres, 
 see § 325, 4. 15. The central end ultimately degenerates. 16. Movement is re- 
 tained completely in the paralyzed parts, e. g., in the extremities. 
 
 Incoordinated Movements of Insensible Limbs. — After section of the posterior roots, e.g., 
 of the nerves for the posterior extremities, the muscles retain their movements, nevertheless there 
 are characteristic disturbances of their motor power. This is expressed in the awkward manner in 
 which the animal executes its movements — it has lost to a large extent its harmony and elegance of 
 motion. This is due to the fact that, owing to the absence of the sensibility of the muscles and 
 skin, the animal is no longer conscious of the resistance which is opposed to its movements. 
 Hence the degree of muscular energy necessary for any particular effort cannot be accurately 
 graduated. Animals which have lost the sensibility of their extremities often allow their limbs 
 to lie in abnormal positions, such as a healthy animal would not tolerate. In man also, when the 
 peripheral ends of the cutaneous nerves are degenerated, there are ataxic phenomena (§ 364, 3). 
 
 Increased Excitability. — Harless (1858)-, Ludwig, and Cyon (controverted by v. Bezold, 
 Uspensky, Griinhagen, and G. Heidenhain) observed that the anterior root is more excitable as 
 long as the posterior roots remain intact and are sensitive, and that their excitability is diminished 
 as soon as the posterior roots are divided. In order to explain this phenomenon, we must assume 
 that in the intact body a series of gentle impulses (impressions of touch, temperature, position of 
 limbs, etc.) are continuously streaming through the posterior roots to the spinal cord, where they 
 are transferred to the motor roots, so that a less stimulus is required to excite the anterior roots 
 than when these reflex impulses of the posterior root, which increase the excitability, are absent. 
 Clearly, a less stimulus will be required to excite a nerve already in a gentle state of excitement 
 than in the case of a fibre which is not so excited. In the former case, the discharging stimulus 
 becomes, as it were, superposed on the excitement already present. (Compare \ 362.) 
 
 The anterior roots of the spinal nerves supply efferent fibres to — 
 
 1. All the voluntary muscles of the trunk and extremities. 
 
 Every muscle always receives its motor fibres from several anterior roots (not from a single nerve 
 root). Hence, every root supplies branches to a particular group of muscles (Preyer, P. Bert, 
 Gad). The experiments of Ferrier and Yeo show that stimulation of each of the anterior roots in 
 apes (brachial and lumbo-sacral plexuses) caused a complex coordinated movement. Section of 
 one root did not cause complete paralysis of these muscles concerned in the coordinated move- 
 ments, although the force of the movement was impaired. These experiments confirm the results 
 of clinical observation on man. The fibres for groups of muscles of different functions {e.g., for 
 flexors, extensors) arise from special limited areas of the spinal cord. The cervical and lumbar 
 enlargements of the spinal cord are great centres for highly coordinated muscular movements. 
 
 2. The anterior roots also supply motor fibres for a number of organs pro- 
 vided with smooth muscular fibres, e. g., the bladder (§ 280), ureter, uterus. 
 [These are the viscero-motor nerves of Gaskell, and from them come also viscero- 
 inhibitory nerves.] 
 
 3. Motor fibres for the smooth muscular fibres of the blood vessels, the vaso- 
 motor, vaso-constrictor, or vaso-hypertonic nerves [also accelerator or aug- 
 mentor nerves of the heart]. They run in the sympathetic for a part of their 
 course (§ 371). 
 
 4. Inhibitory fibres for the blood vessels. These are but imperfectly known. 
 They are also called vaso-dilator or vaso-hypotonic nerves (§ 372). [Also 
 inhibitory nerves for the heart, which leave the spinal axis in the vagus.] 
 
 5. Secretory fibres for the sweat glands of the skin (§ 289). For a part of 
 their course they run in the sympathetic. 
 
 6. The trophic fibres of the tissues (§ 342, I, c). 
 
THE SYMPATHETIC NERVE. 649 
 
 The posterior roots contain all the sensory nerves of the whole of the skin 
 and the internal tissues, except the front part of the head, face, and the internal 
 part of the head. They also contain the tactile nerves for the areas of the skin 
 already mentioned. Stimuli which discharge reflex movements are conducted to 
 the spinal cord through the posterior roots. The sensory fibres of a mixed nerve 
 trunk supply the cutaneous area, which is moved by those muscles (or which covers 
 those muscles — Preyer) to which the same branch supplies the motor fibres 
 {Schroder van der KolK). The special distribution of the motor and sensory 
 nerves of the body belongs to anatomy (Figs. 387, 388, 392, 393). 
 
 356. THE SYMPATHETIC NERVE.— [Anatomical. — The sympathetic nervous system 
 contains a large number of non-medullated or Remak's fibres, and consists of a series of ganglia 
 lying on each side of the vertebral column and connected to each other by inter- ganglionic fibres. 
 The typical distribution obtains in the thoracic region, where the lateral or vertebral ganglia lie 
 close on the vertebrae. In front of this is a second series of ganglia, which do not form a double 
 line, but are connected with the former and with each other. They are the prevertebral or collat- 
 eral ganglia, e.g., semilunar, inferior mesenteric, etc., the nerves connecting them with the former 
 being called rami efferentes. From these fibres proceed to connect them with ganglia lying in or 
 about tissues or organs — the terminal ganglia (Gaskell)."] 
 
 [Each spinal nerve in this region is connected with its corresponding sympathetic ganglion by 
 the ramus communicans, which is formed by fibres both from the anterior and posterior roots of 
 a spinal nerve. It corresponds to the visceral nerve of the morphologist, and is composed of two 
 parts — a white and a gray ramus. The white ramus is composed entirely of medullated fibres, 
 and coming from the anterior and posterior roots of a spinal nerve, passes into the lateral and 
 collateral ganglia. These white rami occur in the dog only from the 2d thoracic to the 2d lumbar 
 nerve (Gaskell). Above and below this the rami are all gray and composed of non-medullated 
 nerve fibres.] 
 
 [In man the four upper rami communicantes from the four upper Cervical nerves all join the 
 superior cervical ganglion (Fig. 386, G g s), the 5th and 6th join the middle cervical, the 7th and 
 8th the inferior cervical ganglion. The lowest pair of ganglia are generally united by a loop on 
 the front of the first coccygeal vertebra, and they lie in relation with the coccygeal ganglion.] 
 
 [Cephalic Portion. — As the sympathetic ascends to the head it forms connections with many 
 of the cranial nerves, and there is a free exchange of fibres between these nerves. (The function 
 and significance of these exchanges are referred to under the physiology of the cranial nerves.)] 
 
 [Dorsal and Abdominal Portion. — Numerous fibres pass from these parts chiefly to the thoracic 
 and abdominal cavities, where they form large gangliated plexuses, from which functionally different 
 fibres proceed to the different organs.] 
 
 [In the dog the 2d, 3d, 4th, and 5th thoracic pass upward into the cervical sympathetic, those in 
 the dorsal region being directed downward from the lateral ganglia to form the splanchnics. The 
 gray non-medullated nerve fibres of each gray ramus are connected with the cells of its ganglion 
 (lateral) ; the fibres do not go beyond the ganglion, but really run to the corresponding spinal nerve 
 to ramify in the sheaths of the nerves, the connective tissue on the vertebrae and the dura mater, 
 and perhaps the other spinal membranes; so that, according to Gaskell, no non-medullated nerves 
 leave the central nervous system by the spinal nerve roots. Thus the white rami communicantes 
 alone constitute the rami visceralis of the morphologist, and all the visceral nerves passing out from 
 the central nervous system into the sympathetic system pass out by them alone. All the nerves in 
 the white ramus are of small calibre (1.8 ft to 2.7 /1) and medullated, while the true motor fibres 
 are much larger (14.4 /* to 19 fi). The small white can be traced upward as medullated fibres into 
 the superior cervical ganglion, and in the thorax over the lateral to form the splanchnics into the 
 collateral ganglia, beyond which they cease to be medullated. By the 2d and 3d sacral nerves 
 some fibres of smallest calibre issue to form the nervi erigentes, which pass over and do not com- 
 municate with the lateral ganglia, but enter the hypogastric plexus, whence they send branches 
 upward to the inferior mesenteric plexus and downward to the bladder, rectum, and generative 
 organs. Gaskell proposes to call them the pelvic splanchnic nerves.] 
 
 [In the cervical region there is no white ramus, and the nerve roots contain no nerve fibres of 
 small calibre. But in this region rises the spinal accessory nerve, between the anterior and 
 posterior roots. It contains small and large nerve fibres ; the former pass into the internal division 
 of this nerve and join the ganglion of the trunk of the vagus, while the large motor fibres form its 
 external branch and supply the sterno-mastoid and trapezius muscles.] 
 
 [All the vasomotor nerves arise in the central nervous system, and they leave the spinal cord 
 as the finest medullated fibres in the anterior roots of all the spinal nerves between the 2d thoracic 
 and 2d lumbar (dog) "along the corresponding ramus visceralis, enter the lateral or main sympa- 
 thetic chain of ganglia, where they become non-medullated, and are thence distributed either directly 
 or after communication with other ganglia" (Gaskell)."] 
 
 ["The vaso-dilator nerves leave the central nervous system among the fine medullated fibres, 
 
650 FUNCTIONS OF THE CERVICAL SYMPATHETIC. 
 
 which help to form the cervico-cranial and sacral rami viscerales, and pass without altering their 
 character into the distal ganglia" (Gaskell).] 
 
 ["The viscero- motor nerves upon which the peristaltic contraction of the thoracic portion of 
 the oesophagus, stomach, and intestines depends, leave the central nervous system in the outflow of 
 fine medullated nerves which occurs in the upper part of the cervical region, and pass by way of 
 the rami viscerales of the accessory and vagus nerves to the ganglion trunci vagi, where they become 
 non-medullated " [Gaskell).'] 
 
 [" The inhibitory nerves of the circular muscles of the alimentary canal and its appendages leave 
 the central nervous system in the anterior roots, and pass out among the fine medullated fibres 
 of the rami viscerales into the distal ganglia without communication with the proximal ganglia" 
 {Gaskell).] 
 
 [Structure of a Ganglion. — The structure of the sympathetic nerve fibres and nerve cells has 
 already been described in \ 321. On making a section of a sympathetic ganglion, e.g., the 
 human superior cervical, we observe groups of cells with bundles of nerve fibres — chiefly non- 
 medullated — running between them, and the whole surrounded by a laminated capsule of connective 
 tissue, which sends septa into the ganglion. The nerve cells have many processes, and are, there- 
 fore, multipolar, and each cell is surrounded by a capsule with nuclei on its inner surface (Fig. 335, 
 II). The processes pierce the capsule, and one of them certainly — and perhaps all the processes — 
 are connected with a nerve fibre. Not unfrequently yellowish-brown pigment is found in the cell 
 substance. Similar cells have been found in the ophthalmic, sub- maxillary, otic, and spheno-palatine 
 ganglia.] 
 
 Functions. — The following is merely a general summary : — 
 I. Independent functions of the sympathetic are those of certain nerve 
 plexuses which remain after all the nervous connections with the cerebro-spinal 
 branches have been divided. The activities of these plexuses may be influenced 
 — either in the direction of inhibition or stimulation — through fibres reaching 
 them from the cerebro-spinal nerves. 
 To these belong : — 
 
 1. The automatic ganglia of the heart (§58). 
 
 2. The mesenteric plexus of the intestine (§ 161). 
 
 3. The plexuses of the uterus, Fallopian tubes, ureters (also of the blood and 
 lymph vessels). 
 
 II. Dependent Functions. — Fibres run in the sympathetic, which (like the 
 peripheral nerves) are active only when their connection with the central nervous 
 system is maintained, e. g., the sensory fibres of the splanchnic. Others again 
 convey impulses from the central nervous system to the ganglia, while the ganglia, 
 in turn, modify the impulses which inhibit or excite the movements of the corre- 
 sponding organs. 
 
 The following statement is a resume of the functions of the sympathetic, according to the ana- 
 tomical arrangement : — 
 
 A. Cervical Part of the Sympathetic. — 1. Pupil- dilating fibres (com- 
 pare Ciliary ganglion, § 347, I, and Iris, § 392). According to Budge, these fibres 
 arise from the spinal cord and run through the upper two dorsal and lowest two 
 cervical nerves into the cervical sympathetic, which conveys them to the" head. 
 Section of the cervical sympathetic or its rami communicantes causes contraction 
 of the pupil. (The central origin of these fibres is referred to in § 362, 1, and 
 §367,8.) 
 
 2. Motor fibres for Miiller's smooth muscle of the orbit, and partly for the 
 external rectus muscle (§ 348). 
 
 3. Vasomotor branches for the outer ear and the side of the face {CI. Ber- 
 nard), tympanum {Prussak), conjunctiva, iris, choroid, retina {only in part — see 
 Ciliary ganglion, §347, I), for the vessels of the oesophagus, larynx, thyroid gland 
 — fibres for the vessels of the brain and its membranes {Donders and Callenfels) ; ' 
 but, according to Nothnagel, fibres also arise from the cranial nerves which form 
 connections with the carotid plexus. 
 
 4. Secretory (trophic) and vasomotor fibres for the salivary glands (§ 145). 
 
 5. Sweat-secretory fibres (see § 288, II). 
 
 6. According to Wolferz and Demtschenko, the lachrymal glands receive sym- 
 pathetic secretory fibres (?). 
 
SECTION AND STIMULATION OF THE CERVICAL SYMPATHETIC. 651 
 
 B. Thoracic and Abdominal Sympathetic. — First of all there is — 
 i. The sympathetic portion of the cardiac plexus (§57, 2), which receives 
 accelerating or augmentor fibres for the heart from the lower cervical and 1st 
 thoracic ganglion (CI. Bernard, v. Bezold, Cyoh, Schmiedeberg). The fibres arise 
 partly from the sympathetic and partly from the plexus around the vertebral artery 
 (v. Bezold, Bever). (Compare § 370.) 
 
 2. The cervical sympathetic and the splanchnic contain fibres which, when their 
 central ends are stimulated, excite the cardio-inhibitory system in the me- 
 dulla oblongata {Bernstein). 
 
 3. The cervical sympathetic contains afferent fibres which, when stimulated, 
 excite the vasomotor centre in the medulla oblongata (Aubert). 
 
 4. The functions of the splanchnic are referred to in §§164, 175, 276 and 
 
 5. The functions of the cceliac and mesenteric plexuses are referred to in 
 §§ 183 and 192. After extirpation of the cceliac ganglion, Lamansky observed 
 temporary disturbance of digestion, undigested food being passed per anum. 
 
 6. For the secretory fibres for sweating, see § 289, II. 
 
 7. Lastly, the abdominal portion of the sympathetic contains motor and vaso- 
 motor fibres for the spleen, the large intestine (accompanying its arteries), bladder 
 (§ 280), ureters, uterus (running in the hypogastric plexus), vas deferens and vesic- 
 ula? seminales. Stimulation of all of these nerve channels causes increased move- 
 ment of the organs, but it must be remembered that the diminished supply of 
 blood thereby produced also acts as a stimulus (§ 161). Section of these nerves 
 is followed by dilatation of the blood vessels, with subsequent derangement of the 
 circulation, and ultimately of the nutrition. The relation of the suprarenal 
 bodies to the sympathetic is referred to in § 103, IV. The renal plexus is 
 referred to in § 276, while the cavernous plexus is treated of in §436. 
 
 Pathological. — Considering the numerous connections of the sympathetic, we would naturally 
 suppose that it offers an extensive area for pathological changes. It is to be observed that all affec- 
 tions involving the vasomotor system are referred to in \ 371. 
 
 The cervical sympathetic is most frequently paralyzed or stimulated ^by traumatic conditions, 
 wounds by bullets or knives, tumors, enlarged lymph glands, aneurisms, inflammation of the apices 
 of the lungs and the adjacent pleura, while exostoses of the vertebrae may stimulate it in part or 
 paralyze it in part. The phenomena so produced have been partly analyzed in treating of the cili- 
 ary ganglion ({} 347, I). Stimulation of the cervical sympathetic in man causes dilatation of 
 the pupil (mydriasis spastica), pallor of the face,'and occasionally hyperidrosis or profuse sweating 
 (| 289, 2, and \ 288) ; disturbance of vision for near objects, as the pupil cannot be contracted (see 
 Accommodation), and hence the spherical aberration of the lens (g 391) must also interfere with 
 vision ; protrusion of the eyeball with widening of the palpebral fissure. Paralysis or section of 
 the cervical sympathetic causes increased fullness of the blood vessels of the side of the head 
 with occasional anidrosis. Contraction of the pupil (myosis paralytica), which undergoes changes 
 in its diameter during accommodation, but not as the effect of the stimulation of light — atropin 
 dilates it slightly. The slit between the eyelids is narrowed, the eyeball retracted and sunk in the 
 orbit, the cornea somewhat flattened, and the consistence of the eyeball diminished. Stimulation of 
 the sympathetic is followed by an increased secretion of saliva (\ 145). The above described symp- 
 toms have been occasionally accompanied by unilateral atrophy of the face. 
 
 [Section of the Cervical Sympathetic. — This experiment is easily done on 
 a rabbit, preferably an albino one. Divide the nerve in the neck, and immedi- 
 ately thereafter (1) the ear and adjoining parts on that side become greatly con- 
 gested with blood, blood vessels appear that were formerly not visible, as a result 
 of the increased quantity of blood in the ear (hyperaamia), there is (2) a rise of 
 the temperature amounting to even 4 to 6° C. (CI. Bernard}. These are the 
 vasomotor changes. (3) The pupil is contracted, the cornea flattened, and there 
 is retraction of the eyeball and consequent narrowing of the palpebral fissure. 
 These are the oculo-pupillary symptoms. Stimulation (electrical) of the peri- 
 pheral end produces the opposite results, — pallor of the ears, owing to 'contraction 
 of the blood vessels, with consequent fall of temperature ; dilatation of the pupil, 
 bulging of the cornea, protrusion of the eyeball (exophthalmos), and widening 
 
652 COMPARATIVE HISTORICAL. 
 
 of the palpebral fissure. At the same time, the blood vessels to the salivary glands 
 are contracted, and there is a secretion of thick saliva. The last results are due to 
 the vaso-constrictor and secretory fibres. The vasomotor and oculo-pupillary fibres, 
 although they lie in the same trunk in the neck, do not issue from the cord by 
 the same nerve roots, the latter come out of the cord with the anterior roots of the 
 ist and 2d dorsal nerves (dog), while section of the cord between the 2d and 4th 
 dorsal vertebrae produces the vasomotor changes only. The nasal mucous mem- 
 brane and lachrymal gland are influenced by the sympathetic] 
 
 [Division of the cervical sympathetic in young growing animals results in hypertrophy of the 
 ear, and increased growth of the hair on that side {Bidder, TV. Stirling).'] 
 
 [The vago-sympathetic nerve (dog) in the neck contains vaso-dilator fibres (really in the 
 sympathetic) for the skin and mucous membranes of that side of the head. Weak stimulation of 
 the central end of the sympathetic causes dilatation of the blood vessels of these parts. The vaso- 
 dilator fibres of the superior maxillary nerve probably come from the same source. The centre for 
 these nerves is in the dorsal region of the cord between the ist and 5th dorsal vertebrae, when the 
 fibres pass out with the rami communicantes to enter the cervical sympathetic [Daslre and Moral). 
 The vaso-dilator fibres occur in the posterior segment of the ring of Vieussens, and when they are 
 stimulated after section of the 7th cranial nerve, there is a " pseudomotor " effect on the muscles 
 of the cheek and lip (§ 349).] 
 
 Irritation in the area of the splanchnic, as occurs occasionally in lead poisoning, is characterized 
 by violent pain (lead colic), inhibition of the intestinal movements (hence, the persistent constipa- 
 tion), slowing of the heart's action, brought about reflexly, just as in Goltz's " tapping" experiment. 
 Irritation in the area of the sensory nerves of the sympathetic may give rise to that condition which 
 is called by Romberg neuralgia hypogastrica, a painful affection of the lower abdominal and sacral 
 regions, hysteralgia, neuralgia testis, which are localized in the plexuses of the sympathetic. In 
 affections of the abdominal sympathetic there may be severe constipation, with diminished or in- 
 creased secretion of the intestinal glands (§ 186). 
 
 357. COMPARATIVE— HISTORICAL. — Comparative. — Some of the cranial nerves 
 may be absent, others, again, may be abortive, or exist as branches of other nerves. The facial 
 nerve, which supplies the muscles of expression in man, and is, at the same time, the nerve for facial 
 respiratory movements, diminishes more and more in the lower classes of the vertebrata, pari passu, 
 with the diminution of the facial muscles. In birds and reptiles it supplies the muscles of the 
 hyoid bone, or the superficial cervical muscles of the nape of the neck. In amphibians (frog) the 
 facial no longer exists as a separate nerve, the nerve which corresponds to it springing from the tri- 
 geminus. In fishes the 5th and 7th nerves form a joint complex nerve. The part corresponding 
 to the facial (also called ramus opercularis trigemini) is the chief motor nerve of the muscles of the 
 gill cover, and is, therefore, the respiratory nerve. In the cyclostomata (lamprey) there is an inde- 
 pendent facial. The vagus is present in all vertebrata ; in fishes it gives off a large nerve, the lat- 
 eral nerve of the body (N. lateralis), which runs along each side of the body close to the lateral 
 canal. It is also present iu the tadpole. Its rudimentary representative in man is the auricular 
 branch. In the frog the 9th, 10th, and nth arise together from one trunk, and the 7th and 8th from 
 another. In fishes and amphibia the hypoglossal is the first cervical nerve. In amphioxus the cere- 
 bral and spinal nerves are not distinct from each other. The spinal nerves are remarkably similar 
 in all classes of the vertebrata. The sympathetic is absent in the cyclostomata, whej-e jtJi^ieDre- 
 sented by the vagus. Its course is along tn^^eT[e1SraT^61uTmirv?ftefe"iFre"cetve'S" the rami commu- 
 nicantes of the spinal nerves. In the region of the head its connections with the 5th and 10th nerves 
 are sDecially developed. In frogs, and still more so in birds, the number of connections with the 
 cranial nerves increases. 
 
 Historical. — The vagus and sympathetic were known to the Hippocratic School. According to 
 Erasistratus, all the nerves proceed from the brain and spinal cord. Herophilus was the first to 
 distinguish the nerves from the tendons, which Aristotle confounded with each other. Marianus 
 (80 a.d.) recognized seven pairs of cranial nerves. Galen was in possession of a wide range of im- 
 portant facts in the physiology of the nervous system (J 140) ; he observed that loss of voice fol- 
 lowed ligature of the recurrent nerves ; and he was acquainted with the accessorius, and the ganglia 
 on the abdominal nerves. The Cauda equina is referred to in the Talmud; Coiter (1573) prescribed 
 exactly the anterior and posterior spinal nerve roots. Van Helmont (f 1644) states that the peri- 
 pheral motor nerves also give rise to impressions of pain, and Cesalpinus (1571) remarks that inter- 
 ruption of the blood stream makes the pirts insensible. Thomas Willis described the chief ganglia 
 (1664). In Des Cartes there is the first indication of reflex movements; Stephen Hales and Robert 
 Whytt showed that the spinal cord was necessary for such acts. Prochaska described the reflex 
 channels [while Marshall Hall established the doctrine of reflex, or, as he called them, "diastal- 
 tic " actions]. Duverney (1761) discovered the ciliary ganglion. Gall traced more carefully the 
 course of the 3d and 6th nerves, and also the spinal nerves into the gray matter. Hitherto only 
 nine nerves of the brain had been enumerated ; Sommerring separated the facial from the auditory 
 nerve, Andsrsch the 9th, 10th, and nth nerves. 
 
PHYSIOLOGY OF THE NERVE CENTRES. 
 
 358. GENERAL. — [The nerve fibres and nerve cells constitute the elements , 
 out of which nerve centres are formed, being held together by connective tissue.* ' 
 In the process of evolution groups of nerve cells with connecting fibres are ar- 
 ranged to constitute nervous masses, whereby there is a corresponding integration 
 of function. Thus with structural integration there is a functional integration. 
 When the structure suffers so also does the function, and those parts which are 
 most evolved, as well as those actions which have to be learned by practice, are 
 the first to suffer during the dissolution of the nervous system.] 
 
 General Functions. — The central organs of the nervous system are in general 
 characterized by the following properties : — 
 
 1. They contain nerve cells, which are either arranged in groups in the in- 
 terior of the central organs of the nervous system, or embedded in the peripheral 
 branches of the nerves. [Nerve cells are centres of activity, originate impulses 
 and conduct impulses as well, while nerve fibres are chiefly conductors.] 
 
 2. The nerve centres are capable of discharging reflexes, e. g., reflex motor, 
 reflex secretory, and reflex inhibitory acts. 
 
 3. The centres may be the seat of automatic excitement, i. <?., they may 
 manifest phenomena, without the application of any apparent external stimulus. 
 The energy so liberated may be transferred to act upon other organs. This auto- 
 matic state of excitement or stimulation may be continuous, i. e., may be continued 
 without interruption, when it is called tonic automatic or tonus ; or it may be 
 intermittent, and occur with a certain rhythm {rhythmical automatic). 
 
 4. The central organs are trophic centres for the nerves proceeding from 
 them ; they may also perform similar functions for the tissues innervated by 
 them. 
 
 5. The physical activities are dependent upon an intact condition of the 
 ganglionic central organs. These various functions are distributed over different 
 centres. 
 
 As a single momentary stimulus, e. g., an opening induction shock, or a puncture of a transverse 
 section of the spinal cord, may produce a longer tetanus, whilst the same stimulus, if applied to the 
 motor nerves, causes only a single contraction, it seems as if the central nervous system possessed 
 the property of transforming an instantaneous stimulus into a long-continued state of stimulation 
 {JR. Marchand). The organs causing continued movement are the ganglionic cells of the anterior 
 horn of the spinal cord [Birke). 
 
 [The term " centre " is merely applied to an aggregation of nerve cells so related to each other 
 as to subserve a certain function, but inasmuch as these cells are connected to each other and with 
 other cells in many ways, various combinations of them may result; again, we have also to take in 
 account the greater or less resistance in some paths than others, so that the variety of combinations 
 which these cells may subserve is enormous. These cells give off processes which branch, and 
 anastomose with processes from other cells. Thus innumerable ways are opened up to nervous 
 impulses by these combinations, so that in a certain way we may regard a cell as a junction of these 
 conducting fibres, or a " shunt " whereby an impulse may be shunted on to one or other branch in 
 the direction of least resistance, or in the best beaten path as it were, while there may be a " block " 
 in other directions.] 
 
 653 
 
THE SPINAL CORD. 
 
 359. STRUCTURE OF THE SPINAL CORD.— [The key to the 
 
 study of the central nervous system is to remember that it begins as an involution 
 of the epiblast, and is original tubular, with a central canal, dilated in the brain 
 end into ventricles. In the spinal cord there are three concentric parts : first, 
 the columnar ciliated epithelium, outside this the central gray tube, and covering 
 in all the outer white conducting fibres (J5fi7/).] 
 
 Structure. — The spinal cord consists of white matter externally and gray matter internally. [It 
 is invested by membranes, the pia mater, composed of two layers and consisting of connective 
 tissue with blood vessels, being firmly adherent to the white matter and sending septa into the 
 
 Transverse section of the spinal cord ; in the centre is the bntterfiy form of the gray matter surrounded by white 
 matter. p, posterior, and a, anterior, horns of. the gray matter ; PR, posterior roots ; A R, anterior roots of a 
 spinal nerve ; A, A, the white anterior ; L, L, the lateral ; P, P, the posterior columns. 
 
 substance of the cord. Both layers dip into the anterior median fissure, and only the inner one into 
 the posterior median groove. The arachnoid is a more delicate membrane and non-vascular, while 
 the dura mater is a tough membrane lining the vertebral canal, and forming a theca or protective 
 coat for the cord (§ 381).] The gray matter has the form of two crescents )-( placed back to 
 back [or a capital H], in which we can distinguish an anterior (a) and a posterior horn (/), a 
 middle part, and gray commissure connecting the two crescents. In the centre of this gray com- 
 missure is a canal — central canal— which runs from the calamus scriptorius downward ; it is lined 
 throughout by a single layer of ciliated cylindrical epithelium [in the fcetus, the cilia not being visible 
 in the adult], and the canal itself is the representative of the embryonal "medullary tube." [The 
 part of the gray commissure in front of this canal is called the anterior, and the part behind, the 
 posterior gray commissure.] [In front of the gray commissure, and between it and the base of the 
 anterior median fissure, are bundles of white nerve fibres passing in a horizontal or oblique direction 
 from the anterior column of one side to the gray matter of the anterior cornu of the opposite side 
 (Fig. 394). These decussating fibres constitute the white commissure.] 
 
 The white matter surrounds the gray, and is arranged in several columns [anterior, lateral, and 
 posterior — by the passage of the nerve roots to the cornua]. Along the anterior surface of the cord 
 
 654 
 
STRUCTURE OF THE WHITE MATTER. 
 
 655 
 
 there runs a well-marked fissure, which dips into the cord itself, but does not reach the gray matter, 
 as a mass of white matter — the white commissure — runs from one side of the cord to the other. 
 Between this fissure, known as the anterior median fissure, and the line of exit of the anterior 
 roots of the spinal nerves, lies the anterior column (A) ; the white matter lying laterally between 
 the origin of the anterior and posterior roots of the spinal nerves is the lateral column (L), while 
 the white matter lying between the line of origin of the posterior roots and the so-called posterior 
 median fissure is the posterior column (P). [The posterior median fissure is not a real fissure 
 
 Fig. 395. 
 
 Fig. 395. — Transverse section of the white matter ot the spinal cord with connective-tissue septa between the fibres. 
 Fig. 306. — Multipolar nerve cells from the gray matter of the anterior horn of the spinal cord (ox), a, nerve 
 cell; b, axis cylinder ; c, gray matter ; d, white matter of column ; c, e, branches of cells. 
 
 but is filled up with the inner layer of the pia mater, which dips down from the under surface of 
 this membrane quite to the gray matter of the posterior commissure.] Each posterior column, in 
 certain regions of the cord, may be subdivided into an inner part lying next the fissure, the postero- 
 median or Goll's column, or the inner root zone ( Charcot, Fig. 403, c ) ; and an outer larger part 
 next the posterior root, known as the postero-external or Burdock's column, or the outer root lone 
 (Charcot, Fig. 403, d). 
 The white matter consists chiefly of medullated fibres without the sheath of Schwann and Ran- 
 
 Fig. 397. 
 
 Diagram of the absolute and relative extent of the gray matter, and of the white columns in successive sectional areas 
 of the spinal cord, as well as the sectional areas of the several entering nerve roots. NR, nerve roots; AC, LC, 
 P C, anterior, lateral and posterior columns ; Gr, gray matter. 
 
 vier's nodes, but provided with the neuro-keratin sheaths of Ktthne and Ewald (§ 321), the fibres 
 themselves being chiefly arranged longitudinally. The nerve fibres qf the nerve roots, as well as 
 those that pass from the gray matter into the columns, have a transverse or oblique course. There 
 are also decussating fibres in the anterior or white commissure. [In a transverse section of the 
 white matter of the spinal cord the nerve fibres are of different sizes, and appear like small circles 
 with a rounded dot in their centre — the axis cylinder; the latter may be stained with carmine or 
 other dye (Fig. 395). They are smallest in the postero-median or Goll's column, and largest in the 
 
656 
 
 ARRANGEMENT OF NERVE CELLS. 
 
 Fig. 398. 
 
 crossed and direct pyramidal tracts, which are motor. The white substance of Schwann, especially 
 in preparations hardened in salts of chromium, often presents the appearance of concentric lines. 
 Fine septa of connective tissue carrying blood vessels lie between groups of the nerve fibres, while 
 here and there between the nerve fibres may be seen branched neuroglia corpuscles. Immediately 
 beneath the pia mater there is a pretty thick layer of neuroglia, which invests the prolongations of 
 the pia into the cord.] 
 
 [The gray matter differs in shape in the different regions of the cord, and so does the gray, 
 commissure (Fig. 398). The latter is thicker and shorter in the cervical than in the dorsal region, 
 while it is very narrow in the lumbar region. 1 he amount of gray matter undergoes a great increase 
 opposite the origins of the large nerves, the increase being most marked opposite the cervical and 
 lumbar enlargements. Ludwig and Woroschiloff constructed a series of curves from measurements 
 by Stilling of the sectional areas of the gray and white matter of the cord, as well as of the several 
 nerve roots. These curves have been arranged in the following convenient form by Schafer, after 
 Woroschiloff (Fig. 397) : — 
 
 [In the cervical region the lateral white columns are large, the anterior cornu of the gray matter 
 is wide and large, while the posterior cornu is narrow ; Goll's column is marked off by a depression 
 
 and a prolongation of the pia mater; the cord itself is 
 broadest from side to side. In the dorsal region the gray 
 matter is small in animals, and both cornua are narrow 
 and of nearly equal breadth, while the cord itself is 
 smaller and cylindrical. In it the intermedio- lateral and 
 posterior vesicular groups of cells are distinct. They have, 
 probably, relations to viscera. The commissure lies well 
 forward betwten the crescents. In the lumbar region 
 the gray matter is relatively and absolutely greatest, while 
 the white lateral columns are small, the central canal in 
 the commissure being nearly in the middle of the cord. 
 In the conus medullaris the gray matter makes up the 
 great mass of it, with a few white fibres externally (Fig. 
 
 398)-] 
 
 1 he anterior cornu of the gray matter is shorter and 
 broader, and does not reach so near to the surface as the 
 posterior ; moreover, each anterior nerve root arises from 
 it by several bundles ; it contains several groups of large 
 multipolar ganglionic cells (Fig. 396); the posterior 
 cornu is more pointed, longer and narrower, and reaches 
 nearer to the surface, the posterior root arising by a single 
 bundle at the postero-lateral fissure ; while the cornu itself 
 contains a few fusiform nerve cells, and is covered by the 
 substantia gelatinosa of Rolando, which is merely an 
 accumulation of neuroglia. 
 
 [The outer margin of the gray matter near its middle 
 is not so sharply defined from the white matter as else- 
 where; and, in fact, a kind of anastamosis of the gray 
 matter projects into the lateral column, especially in the 
 cervical region, constituting the processus reticularis (Fig 
 
 399,0-1 
 
 [Arrangement of Nerve Cells. — The nerve cells are 
 arranged in four groups, forming columns more or less 
 continuous. There are those of the anterior and posterior 
 horns, those of the lateral column (intermedio-lateral), 
 and the posterior vesicular column of Clarke. The ante- 
 rior and posterior groups exist as continuous columns along 
 the entire cord. The cells of the anterior horn being very 
 large (67 to 135^), while the fusiform cells of the posterior 
 horn are 18 ft in diameter. Those of the lateral column 
 are distinct, except in the lumbar and cervical enlarge- 
 ments, where they blend with the anterior horn. The column of Clarke (cells 40 to 90 /x) is dis- 
 continued, and is limited to (1) the thoracic region, (2) cervico-cranial region, (3) sacral region, 
 being most conspicuous in (1) [Gaskell), where it corresponds absolutely to the outflow of visceral 
 nerves.- In the sacral region it corresponds to the " sacral nucleus of Stilling," while in the cervical 
 region it begins in the dog at the 2d cervical nerve, forming the cervical nucleus, being continued 
 above into the nuclei of the vagus and glosso-pharyngeal nerves. The cells of this column give rise 
 to small medullated nerve fibres or the leucenteric fibres of Gaskell.] 
 
 The multipolar ganglion cells are largest, and arranged in groups in the anterior horns of the 
 gray matter (Fig. 394 — " motor ganglionic cells ") ; while smaller spindled-shaped (" sensory ") 
 cells occur in much smaller numbers in the. gray matter of the posterior horn. 
 
 Transverse sections of the spinal cord in dif- 
 ferent regions. A, through the middle of 
 the cervical; B, the dorsal ; C, the lumbar 
 enlargement ; D, upper part of the conus 
 medullaris ; E, at the 5th sacral vertebra ; 
 F, at coccyx ; A, B, C, enlarged twice ; 
 D, E, F, thrice ; a , anterior, p, posterior 
 root. 
 
NEUROGLIA. 
 
 657 
 
 [In a longitudinal section of the cord (Fig. 400) these cells are seen to be arranged iri columns, 
 the large multipolar cells in the anterior horn (m) ; at the same time the longitudinal direction of 
 the nerve fibres in the anterior (a) and posterior white columns (c), the horizontal direction of the 
 fibres of the anterior and posterior nerve roots (b and/ - ).] 
 
 The gray matter contains an exceedingly delicate fibrous network of the finest nerve fibrils 
 [Gerlach), which is produced by the repeated division of the protoplasmic processes of the multi- 
 polar ganglionic cells. Medullated nerve fibres traverse and divide in the gray matter and become 
 non-medullated ; some of them merely pass through the gray matter of the non-medullated fibres 
 and terminate in Gerlach's network. Fibres pass from the gray matter of one side to that of the 
 other through the commissures in front of and behind the central canal. 
 
 Gerlach's Theory. — According to Gerlach, the connection of the fibres and cells is as follows : 
 The fibres of the anterior root proceed directly to the ganglionic cells of the anterior horn, with 
 which they form direct communications by means of the unbranched axial cylinder processes (Fig. 
 401, z). The gray network of protoplasmic processes, produced by the repeated branchings of the 
 fibres of these cells, gives origin to broad fibres. A part of the latter (the median bundle) passes 
 
 Fig. 399. 
 A.M.F 
 
 P.M.F 
 
 Transverse section of the spinal cord (lower dorsal). A, L, P, anterioi . lateral, and posterior columns ; A. M. F., 
 P. M. F., anterior and posterior median fissures ; a, b, c, cells of the anterior horn ; d, posterior cornu and sub- 
 stantia gelatinosa ; e t central canal ; f t veins ; g, anterior root bundles ; h, posterior root bundles ; i, white com- 
 missure ; j, gray commissure ; /, reticular formation. 
 
 through the anterior white commissure to the other side, and then ascends in the anterior column of 
 the opposite side. Other fibres (the lateral bundle) pass into the lateral column of the same side, 
 and ascend in it as far as the decussation of the pyramids, where they cross in the medulla to the 
 other side. The fibres of the posterior root enter the posterior horn, and, after dividing, terminate 
 in the nervous protoplasmic network of the gray matter. By means of this network they are con- 
 nected indirectly with the ganglionic cells of the posterior horn, which are said not to have an axial 
 cylinder process. The gray network, which connects the ganglia of the anterior and posterior horns 
 with each other, also sends fibres, which pass to the other side of the cord in front of and behind 
 the central canal. They then take a backward course, to ascend partly in the posterior horns and 
 partly in the lateral columns. 
 
 Neuroglia. — The connective tissue of the spinal cord arises in part from the pia mater and 
 
 passes only into the white matter, carrying with it blood vessels, and forming septa, which separate the 
 
 nerve fibres info bundles, We must distinguish from the ordinary connective tissue that special form 
 
 in the gray matter to which Ykcljow gave the name of neuroglia, which is the proper sustentacular 
 
 42 
 
658 
 
 BLOOD VESSELS OF THE SPINAL CORD. 
 
 tissue. It is composed of a fine network, which consists of round and large branched cells embedded 
 in a completely homogeneous transparent ground substance. The central canal is surrounded with 
 a denser layer of this tissue, known as the " central ependyma." The neuroglia is also abundant 
 on the sides and apex of the posterior horns, where it is called the gelatinous substance of Ro- 
 
 Fig. 400. 
 
 Fig. 401. 
 
 iiliiilll 
 
 
 mm 
 
 
 ■111 
 
 jHffii 
 
 s-l 
 
 
 IP 
 
 SI 
 
 { w 
 
 wm 
 
 m 
 
 
 Fig. 400.— Longitudinal section, of the human soinal cord, a, anterior, c, posterior, d, lateral white columns; I, 
 anterior, c, posterior nerve roots ;/, horizontal (pyramidal) fibres passing to m, cells of anterior cornu ; «, oblique 
 fibres of posterior root. Fig. 401. — Multipolar nerve cell, from the anterior horn of the spinal cord, z, axis 
 cylinder process ; y, branched processes. 
 
 lando. Similar neurolgia also occurs in the brain. On the surface of the central nervous system, 
 and in the gelatinous substance, is, in addition, a fine network of neurokeratin (§ 321). 
 
 [Blood Vessels. — The anterior median artery gives off branches, which dip into the fissure of 
 the same name, pass to its base, and, after perforating the anterior commissure, divide into two 
 branches, one for each mass of gray matter, and each branch in turn splits into three, which supply 
 
 Fig. 402. — Injected blood vessels of the spinal cord. Fig. 403. — Scheme of the conducting paths in the spinal cord at 
 the 3d dorsal nerve. The black part is the gray matter, w, anterior, A, iv, posterior, root: a, direct, and^ - , 
 crossed, pyramidal tracts : b, anterior column ground bundle ; c, Goll's column ; d, postero-external column ; 
 e and_/i mixed lateral paths ; A, direct cerebellar tracts. 
 
 part of the interior, median, and posterior gray matter. The posterior root artery enters the gray 
 matter along the course of the posterior nerve roots. Some branches also pass from the pia mater 
 into the substance of the cord, and are known as the antero- and median-lateral branches, while 
 others dip in near Goll's column, and another in the postero-external column. The large central 
 
flechsig's systems of conducting fibres. 659 
 
 artery supplies the gray matter. The general result is that the gray matter is much more vascular 
 than tjie white, as is shown in Fig. 402. Adamkiewicz has given a most minute description of the 
 blood vessels of the spinal cord. Some small vessels come from the pia and send branches to the 
 white matter, and unbranched arteries to the gray matter, where they form a capillary plexus. The 
 blood vessels are surrounded by perivascular lymph spaces (His).] [With regard to the blood 
 vessels supplying the cord as a whole, Moxon has pointed out that, owing to the cord not being as 
 long as the vertebral canal, the lower nerves have to run down within the vertebral canal before 
 they emerge from the appropriate inter-vertebral foramina. As reenforcing arteries enter the 
 cord along the course of these nerves, necessarily the branches entering along the course of the 
 lumbar and lower dorsal nerves are long, and this, together with their small sire, offers considerable 
 resistance to the blood stream. Hence, perhaps, why the lower part of the cord is so apt to be 
 affected by various pathological conditions.] 
 
 [Functions of the Spinal Cord. — (i) It is a great conducting medium, 
 conducting impulses upward and downward, and within itself from side to side, 
 (2) the great reflex centre; or rather series of so-called centres; (3) impulses 
 originate within it.] 
 
 Conducting Systems. — The whole of the longitudinal fibres of the spinal 
 cord may be arranged systematically in special bundles, according to their func- 
 tion. 
 
 [Methods. — The course of the fibres and their division into so-called systems has been ascer- 
 tained partly by anatomical and embryological, partly by physiological and pathological 
 means. Apart from experimental methods, such as dividing one column of the cord and observing 
 the results, we have the following methods of investigation : ( 1 ) Tiirck found that injury or disease 
 of certain parts of the brain was followed by a degeneration downward, or secondary descending 
 degeneration of certain of the nerve fibres connected with the seat of injury, i. c, they were sepa- 
 rated from their trophic centres and underwent degeneration. (2) P. Schieferdecker found also, after 
 section of the cord, that above and below the level of the section, certain definite tracts of white matter 
 underwent degeneration [thus showing that certain tracts had their trophic centre below ; this constitutes 
 secondary ascending degeneration]. [(3) Gudden's Method. — He showed, as regards the 
 brain, that excision of a sense organ in a young growing animal was followed by atrophy of the 
 nerve fibres and some other parts connected with it. Thus the optic nerve and anterior corpora 
 quadrigemina atrophy after excision of the eyeball in young rabbits.] (4) Embryological. — 
 Flechsig showed that the fibres of the cord [and the brain also] during development became covered 
 with myelin at different periods, those fibres become medullated latest which had the longest 
 course. In this way he mapped out the following system : — 
 
 Flechsig's System of Fibres. — i. In the anterior column lie {a) the un- 
 crossed, anterior, or direct pyramidal tract ; and external to it is (b) the anterior 
 ground bundle, or anterior radicular zone (Fig. 403). 
 
 2. In the posterior column he distinguishes (<r) Goll's column, or the pos- 
 tero-median (postero-internal) column ; and (d) Burdach's funiculus cuneatus, or 
 the posterior radicular zone, or the postero-external column. 
 
 3. In the lateral column are (/) the anterior, and (/) the lateral mixed paths, 
 (g) the lateral or crossed pyramidal tract, and (Ji) the direct cerebellar tract. All 
 the impulses from the central convolutions [motor areas] of the cerebrum, by 
 means of which voluntary movements are executed, are conducted by the pyra- 
 midal tracts a and g (§ 365). The fibres in these tracts descend from the cen- 
 tral convolutions [i. e., the motor areas], pass through the white matter of the 
 cerebrum, converging like the rays of a fan to the internal capsule, where they lie 
 in the knee and anterior two-thirds of its posterior segment (the fibres for the face 
 at the knee, and behind in order those for the arm and leg), they then enter the 
 middle third of the crosta, pass through the pons into the anterior pyramids of the 
 medulla oblongata, where the great mass crosses over to the lateral column of the 
 opposite side of the cord (crossed pyramidal tract), a small part descending 
 in the cord on the same side as the antero-median tract (direct pyramidal tract, 
 a). In the cord these fibres are probably connected with large multipolar nerve 
 cells in the anterior cornu, and from the latter the motor nerves proceed to the 
 muscles]. The direct cerebellar tract, h, connects the cerebellum directly by as- 
 cending fibres, which proceed through the restiform body from Clarke's column 
 of nerve cells in the gray matter. As fibres from the posterior roots also enter 
 
660 
 
 SECONDARY DEGENERATION AND TROPHIC CENTRES. 
 
 the latter, it follows that h connects the posterior nerve roots of the trunks (but 
 not of the extremities) with the cerebellum ; b, <?,/(and ? a small part of d\ rep- 
 resents the channels which connect the gray matter of the spinal cord and that of 
 the medulla oblongata ; they represent the channels for reflex effects, and they also 
 contain those fibres which are the direct continuation of the anterior spinal nerve 
 roots, which enter the cord at different levels and penetrate into the gray matter. 
 In e and/there are some sensory paths. Lastly, c unites the posterior roots with 
 the gray nuclei of the funiculi graciles of the medulla oblongata ; d connects some 
 of the posterior nerve roots through the restiform body with the vermiform pro- 
 cess of the cerebellum (Flecksig). The direction of conduction in the posterior 
 columns, which are continuations of some of the fibres of the posterior roots, is 
 upward, as part of them degenerates upward after section of the posterior root. 
 Of the fibres of each posterior root, some pass directly into the posterior horn, 
 another part ascends in the posterior column of the same side, and gradually, as it 
 ascends, it comes nearer the posterior median fissure. Some of these fibres enter 
 the gray matter of the posterior horn at a higher level. The fibres of the posterior 
 
 Fig. 404. 
 
 2' ? 
 
 AR 
 
 S 3' 
 
 TR 
 
 Transverse section of the spinal cord, showing the secondary degeneration tracts. AR, anterior, TR, posterior root; 
 i f 1' (CPT), region of the crossed pyramidal tract; 2, 2' (DPT), direct pyramidal tract; PEC, postero-external 
 column ; LC, lateral column (B. Bramwell). 
 
 columns run upward only as far as the decussation of the pyramids, where they 
 seem to end, or at least form connections with the nerve cells of the funiculi gra- 
 ciles [clava], and cuneati [triangular nucleus]. 
 
 Further, the transverse sectional area of the direct and crossed pyramidal tracts (a and^-), the 
 lateral cerebellar tract (A), and Goll's column (c ) gradually diminish from above downward; they 
 serve to connect intracranial central parts with the ganglionic centres distributed along the spinal 
 cord. The anterior root bundle (6), the funiculus cuneatus (d), and the anterior mixed lateral tracts 
 (e) vary in diameter at different parts qf the cord, corresponding to the number of nerve roots. It 
 has been concluded from this that these tracts serve to connect the gray matter at different levels in 
 the cord with each other, and ultimately with the medulla oblongata, so that they do not pass directly 
 to the higher parts of the brain (Fig. 397). 
 
 Nutritive Centres of the Conducting Paths. — Tifrck observed that the 
 destruction of certain parts of the brain caused a secondary degeneration of 
 certain parts of the cord, corresponding to the parts called pyramidal tracts by 
 Fleschig (Fig. 404). P. Schieferdecker found the same effects below where he 
 divided the spinal cord in a dog. Hence it is concluded that the nutritive or 
 trophic centre of the pyramidal tracts lies in the cerebrum. The trophic centre for 
 
REFLEX SPASMS. 
 
 661 
 
 the fibres of the anterior root lies in the multipolar nerve cells of the anterior 
 cornu of the gray matter of the cord. After section of the spinal cord, Goll's 
 column and the direct cerebellar tracts degenerate upward. The nutritive centre 
 of the latter is very probably in the nerve cells of Clarke's column, and that of 
 the former perhaps in the spinal ganglion of the posterior root. Those fibres of 
 the spinal cord which do not degenerate after section of the cord, especially numer- 
 ous in the lateral and anterior columns (Sckieferdecker, Singer), are commissural 
 in function, connecting ganglionic cells with each other, and are, therefore, pro- 
 vided with a trophic centre at both ends. 
 
 Time of Development. — With regard to the time of development of the individual systems, 
 Flechsig finds that the first formed paths are those between the periphery and the central gray matter, 
 especially the nerve roots, i. e., they are the first to be covered with the myelin. Then fibres which 
 connect the gray matter at different levels are formed — the fibres which connect the gray matter of 
 the cord with the cerebellum, and also the former with the tegmentum of the cerebral peduncle. At 
 last the fibres which connect the ganglia of the pedunculus cerebri, and perhaps also the gray matter 
 of the cortex cerebri with the gray matter of the cord are formed. In cases of anencephalous foetuses, 
 i. e., where the cerebrum is absent, neither the pyramidal tracts nor the pyramids are developed. In 
 the drain before birth, medullated nerve fibres are formed in the paracentral, central and occipital 
 convolutions, and in the island of Reil, and last of all in the frontal convolutions ( Tttcssek). 
 
 360. SPINAL REFLEXES. — By the term reflex movement is meant a movement caused 
 by the stimulation of an afferent (sensory) nerve. The stimulus, on being applied to an afferent 
 
 Fig. 405. 
 
 Fig. 406. 
 
 Fig. 405. — Scheme of a reflex arc. S, skin ; M, muscle ; N, nerve cell, with of, afferent, and ef, efferent fibres. 
 Fig. 406. — Section of a spinal segment, showing a unilateral and crossed reflex act. A, anterior, and P, posterior 
 surface; M, muscle; S, skin; G, ganglion. 
 
 nerve, sets up a state of excitement (nervous impulse) in that nerve, which state of excitement is 
 transmitted or conducted in a centripetal direction along the nerve to the centre (spinal cord in this 
 case), where the nerve cells represent the nerve centre; in the centre, the impulse is transferred 
 to the motor, efferent or centrifugal channel. Three factors, therefore, are essential for a reflex 
 motor act — a centripetal or afferent fibre, a transferring centre, a centrifugal or efferent fibre ; these 
 together constitute a reflex arc (Fig. 405). In a purely reflex act, all voluntary activity is ex- 
 eluded. 
 
 Reflex movements may be divided into the three following groups : — 
 
 I. The simple or partial reflexes, which are characterized by the fact that stimulation of a 
 sensory area discharges movement in one muscle only, or, at least, in one limited group of muscles. 
 Examples : A blow upon the knee causes a contraction in the quadriceps extensor cruris ; contact 
 with the conjunctiva causes closure of the eyelids. In the former case the afferent channels arise 
 in the tendon of the quadriceps, and the efferent channels lie in the nerve which supplies the quad- 
 riceps; in the latter case the afferent nerve is the 5th and the efferent the 7th cranial nerve. In 
 the former case the centre is in the lumbar region of the cord ; in the latter, in the gray matter of 
 the medulla oblongata. 
 
 II. The Extensive Incoordinate Reflexes, or Reflex Spasms. — These 
 movements occur in the form of clonic or tetanic contractions ; individual groups 
 of muscles, or all the muscles of the body, may be implicated. Causes : A reflex 
 spasm depends upon a double cause — (as") Either the gray matter or the spinal cord is 
 in a condition of exalted excitability , so that the nervous impulse, after having reached 
 
662 
 
 SUMMATION OF STIMULI AND PFLUGER S LAW. 
 
 Fig. 407. 
 
 the centre, is easily transferred to the neigh- 
 boring centres. This excessive excitability 
 is produced by certain poisons, more espe- 
 cially by strychnin, brucia, caffein (Aubert), 
 atropin, nicotin, carbolic acid, etc. The 
 slightest touch applied to an animal poi- 
 soned with strychnin is sufficient to throw 
 the animal at once into spasms. Pathologi- 
 cal conditions may cause a similar result ; 
 thus, there is excessive excitability in hydro- 
 phobia and tetanus. On the other hand, 
 the central organ may be in such a condi- 
 tion that extensive reflexes cannot take 
 place ; thus, in the condition of apncea, 
 the spasms that occur in poisoning with 
 strychnin do not take place (_/. Rosenthal 
 and Leube, Uspensky), and the same result 
 is brought about by passive artificial respi- 
 ratory movements (v. Ebner — § 361, 3). 
 The performance of other passive periodic 
 movements in various parts of the body also 
 produces a similar condition (Buchheim). 
 If the spinal cord be cooled very consider- 
 ably, reflex spasms may not occur (Kunde). 
 (b) Extensive reflex movements may also 
 take place when the discharging stimulus 
 is very strong. Examples of this condi- 
 tion occur in man ; thus, intense- neuralgia 
 may be accompanied by extensive spasmodic 
 movements. 
 
 [Fig. 407 shows the mechanism of simple and complex reflex movements. Suppose the skin to 
 be stimulated at P, an impulse is sent to A, and from it to a muscle, 1, on the same side, resulting 
 in a unilateral simple reflex movement.- The resistance being less in this direction than in the 
 other channels. If the impulse be stronger, or the transverse resistance in the cord diminished, the 
 impulse may pass to B, thence to 2, resulting in a symmetrical reflex movement on both sides. 
 But if a very strong impulse reaches the cord, or if the excitability of the gray matter be increased, 
 e. g., by strychnin, the resistance to the diffusion of the impulse is diminished, and it passes upward 
 to C and D, resulting in more complex movements; thus, there is irradiation— or it may even 
 affect the centres in the medulla oblongata, E, giving rise to general convulsive movements.] 
 
 Summation of Stimuli. — By this term is meant that a single weak stimulus, 
 which in itself is incapable of discharging a reflex act, may, if repeated sufficiently 
 often, produce this act. The single impulses are conducted to the spinal cord, 
 in which the process of " summation " takes place. According to J. Rosenthal, 
 3 feeble stimuli per second are capable of producing this effect, although 16 
 stimuli per second are most effective. On increasing the number of stimuli per 
 second, no further increase of the reflex act is possible. Other observers {Stir- 
 ling, Ward) have found that stimuli, such as induction shocks, are active within 
 much wider limits, e.g., from 0.05 to 0.4 second interval. W. Stirling has shown 
 that it is extremely probable that all reflex acts are due to the repetition of impulses' 
 in the nerve centres. 
 
 [Strychnin interferes with the summation of stimuli, but the reflex excitability is so greatly exalted 
 that a minimal stimulus is at the same time a maximal one.] 
 
 Pfluger's Law of Reflex Actions. — ( 1 ) The reflex movement occurs on the same side on which 
 the sensory nerve is stimulated, while only those muscles contract whose nerves arise from the same 
 segment of the spinal cord. (2) If the reflex occurs on the other side, only the corresponding 
 muscles contract. (3) If the contractions be unequal upon the two sides, then the most vigorous 
 contractions always occur on the side which is stimulated. (4) If the reflex excitement extends to 
 
 Scheme of mode of propagation of reflex movements. 
 P, skin ; A, B, C, D, motor cells in spinal cord ; 
 1 t z > 3j 4. 5; muscles (Beaunis). 
 
GOLTZ'S CROAKING EXPERIMENT. 663 
 
 other motor nerves, those nerves are always affected which lie in the direction of the medulla 
 oblongata. Lastly, all the muscles of the body may be thrown into contraction. 
 
 Crossed Reflexes. — They are exceptions to these rules. If the region of the eye be irritated 
 in a frog whose cerebrum is removed, there is frequently a reflex contraction in^the hind limb of the 
 opposite side {Luchsinger, Langendorff). In beheaded tritons and tortoises, and in deeply- narcotized 
 dogs and cats, tickling one fore limb is frequently followed by a movement of the hind limb of. the 
 opposite side (Luchsinger). This phenomenon is called a " crossed reflex " (Fig. 406). " If the 
 spinal cord be divided along the middle line throughout its entire extent, then, of course, the reflexes 
 are confined to one side only (Schiff). 
 
 Extensor Tetanus. — General spasms usually manifest themselves as " extensor tetanus," because 
 the extensors overcome the flexor muscles. Nerves which arise from the medulla oblongata may 
 be excited through the stimulation of distant afferent nerves, without general spasms being produced. 
 
 Strychnin is the most powerful reflex-producing poison we possess, and it acts upon the gray 
 matter of the spinal cord. [An animal poisoned with strychnin exhibits tetanic spasms on the appli- 
 cation of the slightest stimulus. All the muscles become rigid, but the extensors overcome the 
 flexors.] If the heart of a frog be ligatured, and the poison alterward applied directly to the spinal 
 cord, reflex spasms are produced, proving that strychnin acts upon the spinal cord. During the 
 spasm the heart is arrested in diastole, owing to the stimulation of the vagus, while the arterial 
 blood pressure is greatly increased, owing to stimulation of the csntral vasomotor centres of the 
 medulla oblongata and spinal cord. Mammals may die from asphyxia during the attack ; still, after 
 large doses, death may occur, owing to paralysis of the spinal cord, due to the frequently-recurring 
 spasms. Fowls are unaffected by comparatively large doses. [We can prove that strychnin dots 
 not produce spasms by acting on the brain, muscle or nerve. Destroy the brain of a frog, divide - 
 one sciatic nerve high up, and inject a small dose of strychnin into the dorsal lymph sack ; in a few 
 minutes all the muscles of the body, except those supplied by the divided nerve, will be in spasms, 
 showing that, although the poisoned blood has circulated in the nerves and muscles of the leg, it 
 does not act on them. Destroy the spinal cord, and the spasms cease at once.] 
 
 Other Poisons. — Chlorojorm diminishes the reflex excitability by acting upon the centre, and 
 a similar effect is produced by picrotoxin, morphia, narcotin, thebain, aconitin, quinine, hydrocyanic 
 acid. [W. Stirling finds that chloral, potassic bromide and chloride, ammonium chloride, but not 
 sodium chloride, greatly diminish the reflex excitability. Nicotin increases it in frogs (Sreusberg).] 
 
 A constant current of electricity passed longitudinally through the cord diminishes the reflexes 
 (Ranke), especially if the direction of the current is from above downward (Legros and Onimus, 
 Uspensky). 
 
 III. Extensive coordinated reflexes are due to stimulation of a sensory- 
 nerve, causing the discharge of complicated reflex movements in whole groups of 
 different muscles, the movements being "purposive" in character, i. <?., as if 
 they were intended for a particular purpose. 
 
 Methods. — The experiments are made upon cold-blooded animals (decapitated or pithed frogs, 
 tortoises, or eels), or upon mammals. In the latter, artificial respiration is kept up, and the four 
 arteries going to the head are ligatured, in order to eliminate the action of the brain (Sig. Mayer, 
 Luchsinger). The reflexes of the lower part of the spinal cord may be studied on animals (or men), 
 in cases where the spinal cord is divided transversely in the upper dorsal region. In such cases 
 some time must elapse in order that the primary effect of the lesion (the so-called shock), which 
 usually causes a diminution of the reflexes, may pass off. Very young mammals exhibit reflexes for 
 a considerable time after they are beheaded. 
 
 Examples. — 1. The protective movements of pithed or decapitated frogs. 
 [If a drop of a dilute acid be applied to the skin of such a frog, immediately it 
 strives to get rid of the offending body, and it generally succeeds in doing so.] 
 Similarly, it kicks against any fixed body pushed against it. These movements 
 are so purposive in their character, and the actions of groups of muscles are so 
 adjusted to perform a particular act, that Pfliiger regarded them as directed by 
 and due to "consciousness of the spinal cord." If a flame be applied to the side 
 or part of the body of an eel, the body is moved away from the flame. The tail 
 of a decapitated triton, tortoise, newt, eel, or snake is directed toward a gentle 
 stimulus, but if a violent stimulus is used, it is directed away from it {Luchsinger). 
 
 2. Goltz's Croaking Experiment. — A pithed (male) frog, i. <?., one with its 
 cerebral lobes alone removed (or one with its eyes or ears destroyed — Langendorff), 
 croaks every time the skin of its back or flanks is gently stroked. [Some male 
 frogs, when held up by the finger and thumb immediately behind the fore legs, 
 croak every time gentle pressure is made on their flank.] 
 
664 REFLEX TIME AND INHIBITION OF REFLEXES. 
 
 3. Goltz's " Embrace Experiment." — During the breeding season, in 
 spring, the part of the body of the male frog, between the skull and the fourth 
 vertebra, embraces every rigid object which is brought into contact with, and 
 gently stimulates, the skin over the sternum. 
 
 4. In mammals (dogs) the following reflex acts are performed by the posterior 
 part of the spinal cord, even after it is separated from the rest of the cord : 
 Scratching with the hind feet a part of the skin which has been tickled (just^as 
 in intact animals) ; the movements necessary for emptying the bladder and for 
 defsecation, as well as those necessary for erection ; the movements necessary for 
 parturition (Goltz, Freusberg and Gergens). Coordinated movements do not, as 
 a rule, occur simultaneously in portions of the spinal cord lying widely apart after 
 removal of the medulla oblongata. According to Ludwig and Owsjannikow, the 
 medulla oblongata, perhaps, contains a reflex organ of a higher order, which forms, 
 as it were, a centre for combining, through the medium of the nerve fibres, the 
 various reflex provinces in the spinal cord. 
 
 5. Coordinated reflexes may occur in man during sleep, and during patho- 
 logical comatose conditions. 
 
 Most of the movements which we perform while we are awake, and which we execute uncon- 
 sciously — or even when our psychical activities are concentrated upon some other object — really 
 belong to the category of coordinated reflexes. Many complicated motor acts must first be learned 
 — e.g., dancing, skating, riding, walking — before unconscious harmonious coSrdinated reflexes can 
 again be discharged. The coordinated reflex movements of coughing, sneezing, and vomiting 
 depend upon the spinal cord, together with the medulla oblongata. 
 
 The following facts are also important : — 
 
 1. Reflexes are more easily and more completely discharged when the specific 
 end organ of the afferent nerve is stimulated than when the trunk of the nerve 
 is stimulated in its course {Marshall Hall, 1837). 
 
 2. A stronger stimulus is required to discharge a reflex movement than for the 
 direct stimulation of motor nerves. 
 
 3. A movement produced reflexly is of shorter duration than the corresponding 
 movement executed voluntarily. Further, the occurrence of the movement after 
 the moment of stimulation is distinctly delayed. In the frog, a period nearly twelve 
 times as long elapses before the occurrence of the contraction than is occupied in 
 the transmission of the impulse in the sensory and motor nerves {Helmholtz, 1854). 
 Thus, the spinal cord offers resistance to the transmission of impulses through it. 
 
 The term " reflex time " is applied to the time necessary for transferring the impulse from the 
 afferent fibre to the nerve cells of the cord, and from them to the efferent fibre. In the frog it is 
 equal to 0.008 to 0.015 second. The time, however, is increased by almost one-third if the impulse 
 pass to the other side of the cord, or if it pass along the cord, e. g., from the sensory nerves of the 
 anterior extremity to the motor roots of the posterior limb. Heat diminishes the reflex time and 
 increases the reflex excitability. Lowering the temperature (winter frogs), as well as the reflex ex- 
 citing poisons already mentioned, lengthen the reflex time, while the reflex excitability is simulta- 
 neously increased. Conversely, the reflex time diminishes as the strength of the stimulus increases, 
 and if may even become of minimal duration (_/. Rosenthal). The reflex time is determined by 
 ascertaining the moment at which the sensory nerve is stimulated, and the subsequent contraction 
 occurs. Deduct from this the time of latent stimulation ($ 298, I), and the time necessary for the 
 conduction of the impulse (f! 298) in the afferent and efferent nerves [v. Helmholtz, J. Rosenthal, 
 Exner, Wundt). 
 
 [Influence of Poisons. — The latent period and reflex time are influenced by a large number 
 of conditions. In a research as yet unpublished, W. Stirling finds that the latent period may re- 
 main nearly constant in a pithed frog for nearly two days, when tested by Tiirck's method. Sodic 
 chloride does not influence the time, nor does sodic bromide or iodide. Potassic chloride, however, 
 lengthens it enormously, or even abolishes reflex action after a very short time, and so do potassic 
 bromide, ammonium chloride and bromide, chloral and croton-chloral. The lithia salts also lengthen 
 the reflex time, or abolish the reflex act after a time.] 
 
 361. INHIBITION OF THE REFLEXES.— Within the body there 
 are mechanisms which can suppress or inhibit the discharge of reflexes, and they 
 may therefore be termed mechanisms inhibiting the reflexes. These are : — 
 
EXAMPLES AND NATURE OF INHIBITION. 665 
 
 i. Voluntary Inhibition. — Reflexes may be inhibited voluntarily, both in 
 the region of the spinal cord and brain. Examples : Keeping the eyelids open 
 when the eyeball is touched; arrest of movement when the skin is tickled. We 
 must observe, however, that the suppression of reflexes is possible only up to a 
 certain point. If the stimulus be strong, and repeated with sufficient frequency, 
 the reflex impulse ultimately overcomes the voluntary effort. It is impossible to 
 suppress those reflex movements which cannot at any time be performed volun- 
 tarily. Thus, erection, ejaculation, parturition, and the movements of the iris, 
 are neither direct voluntary acts, nor can they, when they are excited reflexly, be 
 suppressed by the will. 
 
 2. Setschenow's inhibitory centre is another cerebral apparatus, which 
 in the frog is placed in the optic lobes. If the optic lobes be separated from 
 the rest of the brain and spinal cord by a section made below it, the reflex 
 excitability is increased. If the optic lobes be stimulated with a crystal of 
 common salt or blood, the reflex movements are suppressed. The same results 
 obtain when only one side is operated on. Similar organs are supposed to> 
 be present in the corpora quadrigemina and medulla oblongata of the higher 
 vertebrates. 
 
 [Quinine greatly diminishes the reflex excitability in the frog, but if the medulla oblongata be 
 dividad, the reflex excitability of the cord is restored. The depression is ascribed by Chaperon to. 
 the action of the quinine on Setschenow's centres.] 
 
 3. Strong stimulation of a sensory nerve inhibits reflex movements. The 
 reflex does not take place if an afferent nerve be stimulated very powerfully 
 (Go/tz, Lewisson, A. Fick, and Erlenmeyer). Examples : Suppressing a sneeze- 
 by friction of the nose [compressing the skin of the nose over the exit of the- 
 nasal nerve] ; suppression of the movements produced by tickling, by biting the 
 tongue. Very violent stimulation may even suppress the coordinated reflex 
 movements usually controlled by voluntary impulses. Violent pain of the abdom- 
 inal organs (intestine, uterus, kidneys, bladder, or liver) may prevent a person, 
 from walking or even from standing. To the same category belongs the fact that 
 persons fall down when internal organs richly supplied with nerves are injured, . 
 there being neither injury of the motor nerves nor loss of blood to account for the 
 phenomenon. 
 
 It is important to note that in the suppression of reflexes, antagonistic muscles are often thrown. 
 into action, whether voluntarily or by the stimulaion of sensory nerves, i. e., reflexly. In some 
 cases, in order to cause suppression of the reflex, it appears to be sufficient to direct our attention to 
 the execution of such a complicated reflex act. 1 hus, some persons cannot sneeze when they think 
 intently upon this act itself [Darwin). The voluntary impulse rapidly reaches the reflex centre, 
 and begins to influence it so that the normal course of the reflex stimulation, due to an impulse from 
 the periphery, is interfered with (Schldsser). 
 
 [Nature of Inhibition. — The foregoing view assumes the existence of inhibitory centres, but it 
 is important to point out that it has been attempted to explain this phenomenon without postulating 
 the existence of inhibitory centres. During inhibition the function of an organ is restrained — dur- 
 ing paralysis it is abolished, so that there is a sharp distinction between the two conditions. The 
 analogy between inhibitory phenomena and the effects of interference of waves of light or sound 
 has been pointed out by Bernard and Romanes, while Lauder Brunton has shown good reason for 
 placing the question on a physical basis, and indicating that inhibition is not dependent on the ex- 
 istence of special inhibitory centres, but that stimulation and inhibition are different phases of 
 excitement, the two terms being relative conditions depending on the length of the path along which 
 the impulse has to travel and the rate of its transmission. Brunton points out that the known facts 
 are more consistent with an hypothesis of the interference of waves, one with another, than that 
 there are inhibitory centres for every so-called inhibitory act in the body (see p. 614).] 
 
 [Some drugs affect the reflex excitability directly by acting on the spinal cord, e.g., methylconine, ' 
 but other drugs may produce the same result indirectly by affecting the heart and the blood supply 
 to the cord. If the abdominal aorta of a rabbit be compressed for a few minutes to cut off the 
 supply of blood to the cord and lower limbs, temporary paraplegia is produced.] 
 
 If frogs be asphyxiated in air deprived of all its O, the brain and spinal cord 'become completely 
 unexcitable, and can no longer discharge reflex acts. The motor nerves and the muscles, however, 
 suffer very little, and may retain their excitability for many days {Aubert). 
 
666 THE SUPERFICIAL REFLEXES. 
 
 Tiirck's method of testing the reflex excitability of a frog is the following : 
 A frog is pithed, and after it has recovered from the shock its foot is dipped into 
 dilute sulphuric acid '[2 per 1000]. The time which elapses between the leg being 
 dipped in and the moment it is withdrawn is noted. [The time may be estimated 
 by means of a metronome, or the movements may be inscribed upon a recording 
 surface (Baxt). The time which elapses is known as the " period of latent stim- 
 ulation."] 
 
 This time is greatly prolonged after the optic lobes have been stimulated with a crystal of 
 common salt or blood, or after the stimulation of a sensory nerve. 
 
 Setschenow distinguished tactile reflexes, which are discharged by stimulation of the nerves of 
 touch; and pathic, which are due to stimulation of sensory (pain-conducting) fibres. He and 
 Paschutin suppose that the tactile reflexes are suppressed by voluntary impulses, and the pathic by 
 the centre in the optic lobes. 
 
 Theory of Reflex Movements. — The following theory has been propounded to account for the 
 phenomena already described : It is assumed that the afferent fibre within the gray matter of the 
 spinal cord joins one or more nerve cells, and thus is placed in communication in all directions with 
 the network of fibres in the gray substance. Any impulse reaching the gray matter of the cord has 
 to overcome considerable resistance. The least resistance lies in the direction of those efferent 
 fibres which emerge in the same plane and upon the same side as the entering fibre. Thus the 
 feeblest stimulus gives rise to a simple reflex, which generally is merely a simple protective move- 
 ment for the part of the skin which is stimulated. Still greater resistance is opposed in the direction 
 of other motor ganglia. If the reflex impulse is to pass to these ganglia, either the discharging 
 stimulus must be considerably increased, or the resistance within the connections of the ganglia of 
 the gray matter must be diminished. The latter condition is produced by the action of the above- 
 named poisons, as well as during general increased nervous excitability (hysteria, nervousness). 
 Thus, extensive reflex spasms may be produced either by increasing the stimulus or by diminishing 
 the resistance to conduction in the spinal cord. Those conditions which render the occurrence of 
 reflexes more difficult, or abolish them altogether, must be regarded as increasing the resistance in 
 the reflex arc in the cord. The action of the reflex inhibitory mechanism may be viewed in a 
 similar manner. 
 
 The fibres of the reflex arc must have a connection with the reflex inhibitory paths ; we must 
 assume that equally by the reflex inhibitory stimulation resistance is introduced into the reflex arc. 
 The explanation of extensive coordinated movements is accompanied with difficulties. It is assumed, 
 that by use and also by heredity, those ganglionic cells which are the first to receive the impulse, 
 are placed in the path of least resistance in connection with those cells which transfer the impulse 
 to the groups of muscles, whose contraction, resulting in a coordinated purposive movement, pre- 
 vents the body or the limb from being affected by any injurious influences. 
 
 Pathological. — Anomalies of reflex activity afford an important field to the physician in the 
 investigation of nervous diseases. Enfeeblement, or even complete abolition of the reflexes 
 may occur: (1) Owing to diminished sensibility or complete insensibility of the afferent fibres; 
 (2) in analogous affections of the central organ ; (3) or, lastly, of the efferent fibres. Where there 
 is general depression of the nervous activity (as after shocks, compression or inflammation of the 
 central nervous organs ; in asphyxia, in deep coma, and in consequence of the action of many 
 poisons), the reflexes may be greatly diminished or even abolished. 
 
 [Reflexes. — The physician, by studying the condition of the reflexes, can 
 form an idea as to the condition of practically every inch of the spinal cord. 
 There are three groups of reflexes, (a) the superficial, (£) the deep or tendon, 
 (V) the organic reflexes.] 
 
 [The superficial or skin reflexes are excited by stimulating the skin, e.g., by 
 tickling, pricking, scratching, etc. We can obtain a series of reflexes from below 
 as far up as the lower part of the cervical region. The plantar reflex is obtained 
 by tickling the soles of the feet, when the leg on that side, or, it may be, both 
 legs are drawn up. It is always present in health, and its centre is in the lumbar 
 enlargement of the cord. The cremasteric reflex is well marked in boys, and is 
 easily produced by exciting the skin on the inner side of the thigh, when the 
 testicle on that side is retracted. The gluteal reflex consists in a contraction of 
 the gluteal muscles, when the skin over the buttock is stimulated. The abdo- 
 minal reflex consists in a similar contraction of the abdominal muscles, when the 
 skin over the abdomen in the mammary line is stimulated. The epigastric 
 reflex is obtained by stimulating the skin in front between the fourth and sixth 
 ribs. The interscapular reflex results in a contraction of the muscles attached 
 
TENDON REFLEXES. 
 
 667 
 
 to the scapula, when the skin between the scapulae is stimulated. Its centre cor- 
 responds to the lower cervical and upper dorsal region.] 
 
 [The following table, after Gowers, shows the relation of each reflex to the spinal segment or 
 segments on which it depends : — 
 
 
 . . . . 6 
 
 tt 
 
 .... 7 
 .... 8 
 
 
 
 it 
 tt 
 
 . . . . s 
 .... 6 
 
 tt 
 It 
 
 .... 7 
 .... 8 
 
 tt 
 
 .... 9 
 
 tt 
 
 . . . . io 
 
 tt 
 
 .... ii 
 
 It 
 
 .... 12 
 
 1 
 
 Interscapular. 
 
 • Epigastric. 
 
 - Abdominal. 
 
 Lumbar , 
 
 Sacral 
 
 il 
 
 n 
 l\ 
 
 ■ 4 
 
 ■ 5 
 
 Cremasteric. 
 > Knee Re/lex. 
 
 4 t Gluteal. 
 
 ^C3 
 
 Plantar. 
 
 ■ Vesical. 
 
 Rectal. 
 
 Sexual.] 
 
 Tendon Reflexes. — Under pathological conditions, special attention is 
 directed to the so-called tendon reflexes, which depend upon the fact that a blow 
 upon a tendon {e.g., the quadriceps femoris, tendo- Achilles, etc.), discharges a 
 contraction of the corresponding muscle {Westphal, Erb (1875), Eulenberg and 
 others) ; that the patellar tendon reflex (also called " knee phenomenon") or simply 
 " knee reflex," or "knee jerk," is invariably absent in cases of ataxic tabes 
 dorsalis, while in spastic spinal paralysis it is abnormally strong and extensive 
 {Erb). [The "knee jerk" is elicited by percussing the ligamentum patellae, 
 and is due to a single spasm of the rectus. The latent period is .03 to .04 second, 
 and it is argued by Waller and others that it is doubtful if this tendon reflex is sub- 
 served by a spinal nervous arc, while admitting the effect of the spinal cord in 
 modifying the response of the muscle.] Section of the motor nerves abolishes 
 the patellar phenomenon in rabbits {Schultz), and so does section of the cord 
 opposite the 5th and 6th lumbar vertebras {Tschirjew, Senator). Landois finds 
 that in his own person the contraction occurs 0.048 second after the blow upon 
 the ligamentum patellae. According to Waller, the patellar reflex and the tendo- 
 Achilles reflex occurs 0.03 to 0.4 second, and according to Eulenberg, 0.032 
 second after the blow. According to Westphal these phenomena are not simple 
 reflex processes, but complex conditions intimately dependent upon the muscle 
 tonus, so that when the tonus of the quadriceps femoris is diminished the phe- 
 nomenon is abolished. In order that the phenomenon may take place, it is neces- 
 sary that the outer part of the posterior column of the spinal cord remain intact 
 ( Westphal). [A "jaw jerk " is obtained by suddenly depressing the lower jaw 
 {Gowers, Beevor and De Watteville), and the last observer finds that the latent 
 period is .02 second, and if this be the case, it is an argument against these so-called 
 "tendon reflexes" being true reflexes, and that they are direct contractions of 
 the muscles due to sudden stimulation by extension.] 
 
 Another important diagnostic reflex is the " abdominal reflex " {O. Rosen- 
 bach), which consists in this, that when the skin of the abdomen is stroked, e. g. , 
 with the handle of a percussion hammer, the abdominal muscles contract. When 
 this reflex is absent on both sides in a cerebral affection, it indicates a diffuse 
 disease of the brain ; its absence on one side indicates a local affection of the op- 
 posite half of the brain. The cremasteric, conjunctival, mammilary, 
 pupillary, and nasal reflexes may also be specially investigated. In hemiplegia 
 complicated with cerebral lesions, the reflexes on the paralyzed side are diminished, 
 whilst not unfrequently the patellar reflex may be increased. In extensive cerebral 
 affections accompanied by coma the reflexes are absent on both sides, including, of 
 course, those of the anus and bladder {O. Rosenbach). 
 
 [Horsley finds that in the deepest narcosis produced by nitrous oxide gas the superficial reflexes 
 ('• g-i plantar, conjunctival) are abolished, when the deep' (knee jerk) remain. Anaemia of the* 
 
668 CENTRES IN THE SPINAL CORD. 
 
 lumbar enlargement (compression of the abdominal aorta) causes disappearances of both reflexes 
 {Privosi). Chloroform and asphyxia abolish the deep as well as the superficial reflexes. Horsley 
 regards the so-called deep reflex or knee jerk not as depending on a centre in the cord, but the con- 
 traction of the rectus femoris is due to local irritation of the muscle from sudden elongation.] 
 
 [Method. — The knee jerk is easily elicited by striking the patellar tendon 
 with the edge of the hand or a percussion hammer when the leg is semi-flexed, as 
 when the legs are hanging over the edge of a table or when one leg is crossed over 
 the other. It is almost invariably present in health, but it becomes greatly exag- 
 gerated in descending degeneration of the lateral columns and lateral sclerosis.] 
 
 [Ankle clonus is another tendon reflex, and it is never present in health. If 
 the leg be nearly extended, and pressure made upon the sole of the foot so as sud- 
 denly to flex the foot at the ankle, a series of (5 to 7 per second) rhythmical 
 contractions of the muscles of the calf takes place. Gowers describes a modifi- 
 cation elicited by tapping the muscles of the front of the leg, the "front tap con- 
 traction." Ankle clonus is excessive in sclerosis of the lateral columns and spastic 
 paralysis.] 
 
 [The organic reflexes include a consideration of the acts of micturition, erec- 
 tion, ejaculation, defaecation, and those connected with the motor and secretory 
 digestive processes, respiration, and circulation.] 
 
 [In " ankle clonus" excited by sudden passive flexion of the foot, there is a multiple spasm of 
 the gastrocnemius. Here also the latent period is about 0.3 to 0.4 second and the rhythm 8 to to 
 per second. This short latent period has led some observers to doubt the essentially reflex nature 
 of this act.] 
 
 When we are about to sleep (g 374) there is first of all a temporary increase of the reflexes; in 
 the first sleep the reflexes are diminished, and the pupils are contracted. In deep sleep the abdom- 
 inal, cremasteric, and patellar reflexes are absent; while tickling the soles of the feet and the nose 
 only acts when the stimulus is of a certain intensity. In narcosis, e. g., chloroform or morphia, 
 the abdominal, then the conjunctival and patellar reflexes disappear; lastly, the pupils contract (0. 
 Sosenbach). 
 
 Abnormal increase of the reflex activity usually indicates an increase of the excitability of the 
 reflex centre, although an abnormal sensibility of the afferent nerve may be the cause. As the har- 
 monious equilibrium of the voluntary movements is largely dependent upon and regulated by the re- 
 flexes, it is evident that in affections of the spinal cord there are frequent disturbances of the volun- 
 tary movements, e. g., the characteristic disturbance of motion in attempting to walk, and in grasp- 
 ing movements exhibited by persons suffering from ataxic tabes dorsalis [or, as it is more generally 
 called, locomotor ataxia.~\ 
 
 362. CENTRES IN THE SPINAL CORD.— At various parts of the 
 spinal cord are placed centres capable of being excited reflexly, and which can 
 bring about the discharge of certain complicated, yet well coordinated, motor 
 acts. These centres still retain their activity after the spinal cord is separated from 
 the medulla oblongata ; further, those centres lying in the lower part of the spinal 
 cord still retain their activity after being separated from the higher centres, but in 
 the normal intact body they are subjected to the control of higher reflex centres 
 in the medulla oblongata. Hence, we may speak of them as subordinate spinal 
 centres. The cerebrum, also, partly by the production of perceptions, and partly 
 as the organ of volition, can excite or suppress the action of certain of these sub- 
 ordinate spinal centres. [For the significance of term " Centre," see p. 653.] 
 
 1. The cilio-spinal centre {Budge) connected with the dilatation of the 
 pupil lies in the lower cervical part of the cord, and extends downward to the 
 region of the first to the third dorsal vertebra. It is excited by diminution of 
 light ; both pupils always react simultaneously, when one retina is shaded. . Uni- 
 lateral extirpation of this part of the spinal cord causes contraction of the pupil 
 on the same side. The motor fibres pass out by the anterior roots of the two lower 
 cervical and two upper dorsal nerves, into the cervical sympathetic (§ 392). Even 
 the idea of darkness may sometimes, though rarely, cause dilatation of the pupil 
 {Budge). 
 
 In goats and cats this centre, even after being separated from the medulla oblongata, can be ex- 
 cited directly by dyspnceic blood, and also reflexly by the stimulation of sensory nerves, c. g., the 
 
MUSCLE TONUS. 669 
 
 median, especially when the reflex excitability of the cord is increased by the action of strychnin or 
 atropin (Luchsinger). For the dilator centre in the medulla oblongata see § 3671 8. 
 
 2. The ano-spinal centre (Budge) or centre controlling the act of defeca- 
 tion. The afferent nerves lie in the haemorrhoidal and inferior mesenteric 
 plexuses, the centre at the 5th (dog) or 6th to 7th (rabbit) lumbar vertebra; the 
 efferent fibres arise from the pudendal plexus and pass to the sphincter muscles. 
 For the relation of this centre to the cerebrum see § 160. After section of trie 
 spinal cord [in dogs], Goltz observed that the sphincter contracted rhythmically 
 upon the finger introduced into the anus ; the coordinated activity of the centre 
 therefore would seem to be possible only when the centre remains in connection 
 with the brain. 
 
 3. The vesico-spinal centre (Budge") for regulating micturition, or Budge's 
 vesico-spinal centre. The centre for the sphincter muscle lies at the 5th (dog) or 
 the 7th (rabbit) lumbar vertebra, and that for the muscles of the bladder some- 
 what higher. The centre acts only in a properly coordinated way in connection 
 with the brain (§ 280). 
 
 4. The erection centre (§ 436) also lies in the lumbar region. The afferent 
 nerves are the sensory nerves of the penis ; the efferent nerves for the deep artery 
 of the penis are the vaso-dilator nerves, arising from the 1st to 3d sacral nerves, 
 or Eckhard's nervi erigentes — while the motor nerves for the ischio-cavernosus 
 and deep transverse perineal muscles arise from the 3d to 4th sacral nerves (§ 356). 
 The latter may also be excited voluntarily, the former also partly by the brain, by 
 directing the attention to the sexual activity. Eckhard observed erection to take 
 place after stimulation of the higher regions of the spinal cord, as well as of the 
 pons and crura cerebri. 
 
 5. The ejaculation centre. The afferent nerve is the dorsal of the penis, the 
 centre (Budge's genito-spinal centre) lies at the 4th lumbar vertebra (rabbit) ; the 
 motor fibres of the vas deferens arise from the 4th and 5th lumbar nerves, which 
 pass into the sympathetic, and from thence to the vas deferens. The motor fibres 
 for the bulbo-cavernosus muscle, which ejects the semen from the bulb of the 
 urethra, lie in the 3d and 4th sacral nerves (perineal). 
 
 6. The parturition centre (§ 453) lies at the 1st and 2d lumbar vertebra 
 (Korner) ; the afferent fibres come from the uterine plexus, to which also the 
 motor fibres proceed. Goltz and Freusberg observed that a bitch became preg- 
 nant after its spinal cord was divided at the 1st lumbar vertebra. 
 
 7. Vasomotor Centres. — Both vasomotor and vaso-dilator centres are dis- 
 tributed throughout the whole spinal axis. To them belongs the centre for the 
 spleen, which in the dog is opposite the ist~4th cervical vertebras (Bulgak). They 
 can be excited reflexly, but they are also controlled by the dominating centre in 
 the medulla oblongata (§ 371). Psychical disturbance (cerebrum) influences 
 them (§ 377). 
 
 [8. Perhaps there are vaso-dilator centres.] 
 
 9. The sweat centre is, perhaps, distributed similarly to the vasomotor centre 
 (§ 288). 
 
 The reflex movements discharged from these centres are orderly coordinated reflexes, and may 
 thus be compared to the orderly reflexes of the trunk and extremities. 
 
 Muscle Tonus. — Formerly automatic functions were ascribed to the spinal cord, one of these 
 being that it caused a moderate active tension of the muscles— a condition that was termed muscle 
 tone, or tonus. The existence of tonus in a striped muscle was thought to be proved by the fact 
 that, when such a muscle was divided, its ends retracted. This is due merely to the fact that all 
 the muscles are stretched slightly beyond their normal length (J 301). Even paralyzed muscles, 
 which have lost their muscular tone, show the same phenomenon. Formerly, the stronger contrac- 
 tion of certain muscles, after paralysis of their antagonists, and the retraction of the facial muscles 
 to the sound side, after paralysis of the facial nerve, were also regarded as due to tonus. This 
 result is simply due to the fact that, after the activity of the intact muscles, the other ones have no? 
 sufficient power to restore the parts to their normal median position. The following experiment of 
 Auerbach and Heidenhain is against the assumption of a tonic contraction : If the muscles of the 
 
670 EXCITABILITY OF THE SPINAL CORD. 
 
 leg of a decapitated frog be stretched, it is found that they do not elongate after section of the 
 sciatic nerve, or after it is paralyzed by touching it with ammonia or carbolic acid. 
 
 Reflex Tonus. — If, however, a decapitated frog be suspended in an abnormal position, we 
 observe, after section of the sciatic nerve, or the posterior nerve roots on one side, that the leg on 
 that side hangs limp, while the leg of the sound side is slightly retracted. The sensory nerves of 
 the latter are slightly and continually stimulated by the weight of the limb, so that a slight reflex 
 retraction of the leg takes place, which disappears as soon as the sensory nerves of the leg are 
 divided. If we choose to call this slight retraction tonus, then it is a reflex tonus {Brondgeest). 
 (See the experiments of Harless, C. Ludwig, and Cyon — \ 3S5-) 
 
 363. EXCITABILITY OF THE SPINAL CORD.— Even at the pres- 
 ent time observers are by no means agreed whether the spinal cord, like peripheral 
 nerves, is excitable, or whether it is distinguished by the remarkable peculiarity 
 that most of its conducting paths and ganglia do not react to direct electrical and 
 mechanical stimuli. 
 
 If stimuli be cautiously applied either to the white or gray matter there is neither movement nor 
 sensation ( Van Deen {1841), Brown-Siquard, Schiff, Huizinga, Sigm. Mayer). In doing this ex- 
 periment, we must be careful not to stimulate the roots of the spinal nerves, as these respond at once 
 to stimuli, and thus may give rise to movements or sensations. As the spinal cord conducts to the 
 brain impulses communicated to it from the stimulated posterior roots, but does not itself respond 
 to stimuli which produce sensations, Schiff has applied to it the term " sesthesodic." Further, as 
 the cord can conduct both voluntary and reflex motor impulses, without, however, itself being 
 affected by motor impulses applied to it directly, he calls it "kinesodic." Schiff's views are as 
 follows : — 
 
 i . In the posterior columns the sensory root fibres of the posterior root 
 which traverse these columns give rise to painful impressions, but the proper paths 
 of the posterior columns themselves do not do so. The proof that stimulation of 
 the posterior column produces sensory impressions, he finds in the fact that dila- 
 tation of the pupil occurred with every stimulation (§ 392). Removal of the pos- 
 terior column produces anaesthesia (loss of tactile sensation). Algesia [or the 
 sensation of pain] remains intact, although at first there may even be hyperalgesia. 
 
 2. The anterior columns are non-excitable, both for striped and non-striped 
 muscle, as long as the stimuli are applied only to the proper paths of this column. 
 But movements may follow, either when the anterior nerve roots are stimulated, 
 or when, by the escape of the current, the posterior columns are affected, whereby 
 reflex movements are produced. 
 
 According to Schiff, therefore, all the phenomena of irritation, which occur when an uninjured 
 cord is stimulated (spasms, contracture), are caused either by simultaneous stimulation of the ante- 
 rior roots, or are reflexes from the posterior columns alone, or simultaneously from the posterior 
 columns and the posterior roots. Diseases affecting only the anterior and lateral columns alone 
 never produce symptoms of irritation, but always of paralysis In complete anaesthesia and apnoea 
 every form of stimulus is quite inactive. According to Schiff's view, all centres, both spinal and 
 cerebral, are inexcitable by artificial means. 
 
 Direct Excitability. — Many observers, however, oppose these views, and contend that the 
 spinal cord is excitable to direct stimulation. Fick observed movements to take place when he 
 stimulated the white columns of the cord of a frog, isolated for a' long distance so as to avoid the 
 escape of the stimulating currents. Biedermann comes to the following conclusions : the transverse 
 section of a motor nerve is most excitable. Weak stimuli (descending opening shocks) excite the 
 cut surface of the transversely divided spinal cord, but do not act when applied further down. 
 Luchsinger asserts that, after dipping the anterior part of a beheaded snake into warm water, the 
 reflex movements of the upper part of the cord are abolished, while the direct excitability remains. 
 
 3. Excitability of the Vasomotors. — The vaso-constrictor nerves, 
 which proceed from the vasomotor centre and run downward in the [lateral 
 columns of the] cord, are excitable by all stimuli along their whole course ; direct 
 stimulation of any transverse section of the cord constricts all the blood vessels 
 below the point of section (C. Ludwig and Thiry). In the same way, the fibres 
 which ascend in the cord, and increase the action of the vasomotor centre — 
 pressor fibres, are also excitable (C. Ludwig and Diltmar — § 364, 10). Stimulation 
 of these fibres, although it affects the vasomotor centre refiexly, does not cause 
 
CONDUCTING PATHS IN SPINAL CORD. 671 
 
 sensation. Schiff maintains, however, that these are not the direct results of 
 stimulation. 
 
 4. Chemical Stimuli, such as the application of common salt, or wetting 
 the cut surface with blood, appear to excite the spinal cord. 
 
 5. The motor centres are directly excited by blood heated above 40 C, 
 or by asphyxiated blood, or by sudden and complete anaemia of the cord pro- 
 duced by ligature of the aorta (Sigm. Mayer) ; and also by certain poisons — 
 picrotoxin, nicotin and compounds of barium {Luchsinger). 
 
 Action of Blood and Poisons. — In experiments of this kind the spinal cord ought to be 
 divided at the first lumbar vertebra at least twenty hours before the experiment is begun. It is 
 well to divide the posterior roots beforehand to avoid reflex movements. If, in a cat thus operated 
 on, dyspncea be produced, or its blood overheated, then spasms, contraction of the vessels and secre- 
 tion of sweat occur in the hind limbs, together with evacuation of the contents of the bladder and 
 rectum, while there are movements of the uterus and the vas deferens. Some poisons act in a 
 similar manner. In animals with the medulla oblongata divided, rhythmical respiratory movements 
 may he produced if the spinal cord has been previously rendered very sensitive by strychnin or 
 overheated blood (P. v. Rokitansky, v. Schroff—\ 368). 
 
 Hyperesthesia. — After unilateral section of the cord, or even only of the 
 posterior or lateral columns, there is hyperesthesia on the same side below the 
 point of section (Fodira {1823), and others), so that rabbits shriek on the slightest 
 touch. The phenomenon may last for three weeks, and then give place to normal 
 or sub-normal excitability. On the sound side the sensibility remains perma- 
 nently diminished. A similar result has been observed in cases of injury in man. 
 An analogous phenomenon, or a tendency to contraction in the muscles below the 
 section (Hyperkinesia), has been observed by Brown-Sequard after section of 
 the anterior columns. 
 
 364. THE CONDUCTING PATHS IN THE SPINAL CORD.— 
 [Posterior Root. — The fibres of the posterior root enter the cord in three 
 bundles {a) the inner one, or internal radicular fasciculus sweeps through 
 the postero-external column to enter the gray matter. It is supposed to convey 
 the impressions from tendons and those for touch and locality. Hence, when 
 this column is diseased, as in locomotor ataxia, the deep reflexes, especially the 
 patellar tendon reflex, are enfeebled, or it may be abolished, while the implica- 
 tion of the fibres of the internal fasciculus gives rise to severe pain. (6) The 
 outer radicular fibres enter the gray matter of the posterior horn, and are sup- 
 posed to convey the impressions for cutaneous reflexes and temperature. (<r) The 
 central fibres pass directly into the gray matter, and are supposed to conduct 
 painful impressions into the gray matter.] 
 
 1. Localized tactile sensations (temperature, pressure and the muscular 
 sense impressions) are conducted upward through the posterior roots to the 
 ganglia of the posterior cornu, and, lastly, into the posterior column of the same 
 
 - side. 
 
 In man the conducting path from the legs runs in Coil's column, while those for the arms run in 
 the ground bundle (Fig. 403) (Flechsig). 
 
 In rabbits the path of localized tactile impressions lies in the lower dorsal region in the lateral 
 columns (Ludwig and Woroschiloff, Ott and Meade- Smith). 
 
 Anaesthesia. — Section of individual parts of the lateral columns abolishes the sensibility for the 
 parts of the skin connected with the part destroyed, while total section produces the same result 
 for the whole of the opposite side of the body below the section. The condition where tactile and 
 muscular sensibility is lost is known as anesthesia. 
 
 2. Localized voluntary movements in man are conducted on the same 
 side through the anterior and lateral columns (§§ 358 and 365), in the parts known 
 as the pyramidal tracts. The impulses then pass into the cells of the anterior 
 cornu, and thence to the corresponding anterior nerve roots to the muscles. The 
 exact section experiments of Ludwig and Woroschiloff showed that, in the lower 
 dorsal region of the rabbit, these paths were confined to the lateral columns. 
 
672 LOCOMOTOR ATAXIA. 
 
 Every motor nerve fibre is connected with a nerve cell in the anterior horn of the 
 frog's spinal cord (Gaule and Birge). Section of one lateral column abolishes 
 voluntary movement in the corresponding individual muscles below the point of 
 section. It is obvious, from the conduction in i and 2, that the lateral columns 
 must increase in thickness and number of fibres from below upward [Stilling, 
 Wbroschiloff) [see Fig. 397]. 
 
 3. Tactile (extensive and coordinated) Reflexes. — The fibres enter by the 
 posterior root, and proceed to the posterior cornu. The groups of ganglionic cell?, 
 which control the coordinated reflexes, are connected together by fibres which run 
 in the anterior tracts, the anterior ground bundle and (?) the direct cerebellar 
 tracts (p. 659). The fibres for the muscles which are contracted pass from the 
 motor ganglia outward through the anterior roots. 
 
 In ataxic tabes dorsalis, or locomotor ataxia, there is a degeneration of the posterior columns, 
 characterized by a peculiar motor disturbance. The voluntary movements can be executed with full 
 and normal vigor, but the finer harmonious adjustments are wanting or impaired, both in intensity 
 and extent. These depend in part upon the normal existence of tactile and muscular impressions, 
 whose channels lie in the posterior columns. After degeneration of the latter, there is not only 
 anaesthesia, but also a disturbance in the discharge of tactile reflexes, for which the centripetal arc is 
 interrupted. But a simultaneous lesion of the sensory nerves alone may in a similar matter materi- 
 ally influence the harmony of the movements, owing to the analgesia and the disappearance of the 
 pathic reflexes ({> 355). As the fibres of the posterior root traverse the white posterior columns, 
 we can account for the disturbances of sensation which characterize the degenerations of these parts 
 (Charcot and Pierret). But even the posterior roots themselves may undergo degeneration, and 
 this may also give rise to disturbances of sensation (p. 648). The sensory disturbances usually con- 
 sist in an abnormal increase of the tactile or painful sensations, with lightning pains shooting down 
 the limbs, and this condition may lead on to one where the tactile and painful sensations are abol- 
 ished. At the same time, owing to stimulation of the posterior columns, the tactile sensibility is 
 altered, giving rise to the sensation of formication, or a feeling of constriction [" girdle sensa- 
 tion"]. The conduction of sensory impressions is often slowed ($ 337). The sensibility of the 
 muscles, joints, and internal parts is altered. 
 
 The maintenance of the equilibrium is largely guided by the impulses which travel inward 
 to the coordinating centres through the sensory nerves, special and general, deep and superficial. 
 In many cases of locomotor ataxia, if the patient place his feet close together and close his eyes, he 
 sways from side to side and may fall over, because by cutting off the guiding sensations obtained 
 through the optic nerve, the other enfeebled impulses obtained from the skin and the deeper struct- 
 ures are too feeble to excite proper coordination. 
 
 4. The inhibition of tactile reflexes occurs through the anterior columns ; 
 the impulses pass from the anterior column at the corresponding level into the 
 gray matter, where they form connections with the reflex conducting apparatus. 
 
 5. The conduction of painful impressions occurs through the posterior roots, 
 and thence through the whole of the gray matter. There is a partial decussation 
 of these impulses in the cord, the conducting fibres passing from one side to the 
 other. The further course of these fibres to the brain is given in § 365. 
 
 The experiments of Weiss on dogs, by dividing the lateral column at the limit of the dorsal and 
 lumbar regions, showed that each lateral column contains sensory fibres for both sides. The chief 
 mass of the motor fibres remains on the same side. Section of both lateral columns abolishes 
 completely sensibility and mobility on both sides. The anterior columns and the gray matter are 
 not sufficient to maintain these. If all the gray matter be divided, except a small connecting por- 
 tion, this is sufficient to conduct painful impressions. In this case, however, the conduction is slower 
 (Schiff). Only when the gray matter is completely divided is the conduction of painful impressions 
 from below completely interrupted. This gives rise to the condition of analgesia, in which, when 
 the posterior columns are still intact, tactile impressions are still conducted. This condition is some- 
 times observed in man during incomplete narcosis from chloroform and morphia ( Thiersch). Those 
 poisons act sooner on the nerves which administer to painful sensations than on those for tactile im- 
 pressions, so that the person operated on is conscious of the contact of a knife, but not of the pain- 
 ful sensations caused by the knife dividing the parts. 
 
 Irradiation of Pain. — As painful impressions are conducted by the whole of the gray matter, 
 and as the impressions are more powerful the stronger the painful impression, we may thus explain 
 the so called irradiation of painful impressions. During violent pain, the pain seems to extend to 
 wide areas ; thus, in violent toothache, proceeding from a particular tooth, the pain may be felt in 
 the whole jaw, or it may be over one side of the head. 
 
CONDUCTION IN THE SPINAL CORD. 673 
 
 6. The conduction of spasmodic, involuntary, incoordinated movements 
 takes place through the gray matter, and from the latter through the anterior 
 roots. 
 
 It occurs in epilepsy, in poisoning with strychnin, in uremic poisoning, and tetanus (§ 360, II). 
 The anaemic and dyspnceic spasms are excited in and conducted from the medulla oblongata, and 
 are communicated through the whole of the gray matter. 
 
 7. The conduction of extensive reflex spasms takes place from the posterior 
 roots, perhaps, to the cells of the posterior cornu and then to the cells of the 
 anterior cornu, above and below the plane of the entering impulse (Fig. 407), 
 and, lastly, into the anterior roots, under the conditions already referred to in 
 
 § 36c n. 
 
 8. The inhibition of pathic reflexes occurs through the anterior columns 
 downward, and then into the gray matter to the connecting channels of the" reflex 
 organ, into which it introduces resistance. 
 
 9. The vasomotor fibres run in the lateral columns (JDittmar), and, after 
 they have passed into the ganglia of the gray matter at the corresponding level, 
 they leave the spinal cord by the anterior roots. They reach the muscles of 
 the blood vessels either through the paths of the spinal nerves, or they pass 
 through the rami communicantes into the sympathetic, and thence into the 
 visceral plexuses (§ 356). 
 
 Section of the spinal cord paralyzes all the vasomotor nerves below the point of section; while 
 stimulation of the peripheral end of the spinal cord causes contraction of all these vessels. [Ott's 
 experiments on cats show that the vasomotor fibres run in the lateral columns, and that they as well 
 as the sudorific nerves decussate in the cord.] 
 
 10. Pressor fibres enter through the posterior roots, run upward to the lateral 
 columns, and undergo an incomplete decussation (C. Ludwig and Miescher). 
 
 They ultimately terminate in the dominating vasomotor centre in the medulla oblongata, which 
 they excite reflexly. Similarly, depressor fibres must pass upward in the spinal cord, but we know 
 nothing as to their course. 
 
 11. From the respiratory centre in the medulla oblongata, respiratory nerves 
 run downward in the lateral columns on the same side, and without forming any 
 connections with the ganglia of the anterior cornu (?), pass through the anterior 
 roots into the motor nerves of the respiratory muscles (Schiff). 
 
 Unilateral, or total destruction of the spinal cord, the higher up it is done, accordingly paralyzes 
 more and more of the respiratory nerves, on the same or on both sides. Section of the cord above 
 the origin of the phrenic nerves causes death, owing to the paralysis of these nerves of the diaphragm 
 
 (8 »3)- 
 
 In pathological cases, in degeneration of, or direct injury to, the spinal cord or its individual 
 parts, we must be careful to observe whether there may not be present simultaneously paralytic and 
 irritative phenomena, whereby the symptoms are obscured. 
 
 [Complete transverse section of the cord results immediately in com- 
 plete paralysis or motion and sensation in all the parts supplied by nerves below 
 the seat of the injury, although the muscles below the injury retain their normal 
 trophic and electrical conditions. There is a narrow hypersesthetic area at the 
 upper limit of the paralyzed area, and when this occurs in the dorsal region, it 
 gives rise to the feeling of a belt tightly drawn round the waist, or the "girdle 
 sensation." There is, also, vasomotor paralysis below the lesion, but the blood 
 vessels soon regain their tone owing to the subsidiary vasomotor centres in the 
 cord. The remote effects come on much later, and are secondary descending 
 degeneration in the crossed and direct pyramidal tracts and ascending degenera- 
 tion in the postero-internal columns (Fig. 404). According to the seat of the 
 lesion, the functions of the bladder and rectum may be interfered with. Injury 
 to the upper cervical region sometimes causes hyperpyrexia.] 
 
 43 
 
674 
 
 EFFECTS OF SECTION OF THE CORD. 
 
 [Unilateral section results in paralysis of voluntary motion in the muscles 
 supplied by nerves given off below the seat of the injury, 
 although the muscles do not atrophy, but when secondary 
 descending degeneration occurs they become rigid, and ex- 
 hibit the ordinary signs of contracture. There is vasomotor 
 paralysis on the same side, although this passes off below the 
 injury, while the ordinary and muscular sensibility are dimin- 
 ished on both sides (Fig. 408). • There is bilateral anaesthesia. 
 On the opposite side there is total anaesthesia and analgesia 
 below the lesion, but on the same side in the dorsal region 
 there is a narrow circular anaesthetic zone (Fig. 408, b~), cor- 
 responding to the sensory nerve fibres destroyed at the level 
 of the section. The sensory nerves decussate shortly after 
 they enter the cord, hence the anaesthesia on the opposite 
 side, but they do not cross at once, but run obliquely upward 
 before they enter the gray matter of the opposite side, so that 
 a unilateral section will involve some fibres coming from the 
 same side, and hence the slightly diminished sensibility in a 
 circular area on the same side. There is a narrow hyperaes- 
 thetic area on the same side as the lesion, at the upper limit 
 of paralyzed cutaneous area (Fig. 408, c), due, perhaps, to 
 stimulation of the cut ends of the sensory fibres on that side. 
 In man there is hyperesthesia (to touch, tickling, pain, heat 
 and cold) on the parts below the lesion on the same side, but 
 the cause of this is not known. The remote effects are due 
 to the usual descending and ascending degeneration which 
 set in.] 
 
 [In monkeys, after hemisection of the cord in the dorsal region, there 
 is paralysis of voluntary motion and retention of sensibility with vasomotor 
 paralysis of the same side, and retention of voluntary motion with anaes- 
 thesia and analgesia on the opposite side. The existence of hyperaesthesia on the side of the lesion 
 is not certain in these animals, but there is no doubt of it in man. Ferrier also, finds (in opposition 
 to Brown-Sequard) that the muscular sense is paralyzed as well as all other forms of sensibility, on 
 the side opposite to the lesion, but unimpaired on the side of the lesion. The muscular sense, in 
 fact, is entirely separable from the motor innervation of muscle {Ferrier). The power of emptying 
 the bladder and rectum was not affected.] 
 
 Diagrammatic represen- 
 tation of a lesion of 
 the left half of the 
 spinal cord in the 
 dorsal region. (a) 
 oblique lines, motor 
 and vasomotor pa- 
 ralysis ; (A, d} com- 
 plete anaesthesia ; {a, 
 r) hyperaesthesia of 
 the skin [Erb). 
 
THE BRAIN. 
 
 365. GENERAL SCHEMA OF THE BRAIN.— In an organ so complicated in its struc- 
 ture as the brain, it is necessary to have a general view of the chief arrangements of its individual 
 parts. Meynert gave a plan of the general arrangement of this organ, and although this plan may 
 not be quite correct, still it is useful in the stU'Hy of brain function 
 
 [A special layer of gray matter of the -cerebrum . is placed externally and spread as a thin 
 coating over the white matter, or centrum ovale, which lies internally, and consists of nerve fibres 
 or the white matter. That part lying in each hemisphere is the centrum semi-ovale. The gray 
 matter is folded into gyri, or convolutions, separated from each other by fissures, or sulci. 
 Some of the latter are very marked, and serve to separate adjacent lobes, while the lobes themselves 
 
 Fio. 409. 
 
 Dissection of the brain from above, showing the lateral, 3d, and 4th ventricles, with the basal ganglia and surround- 
 ing parts, a, knee of the corpus callosum ; b, anterior part of the right corpus striatum ; 6' , gray matter dissected 
 off to show white fibres ; c, points to taenia semicircularis ; d, optic thalamus ; e, anterior pillars of fornix, with 
 5th ventricle in front of them, between the two laminae of the septum lucidum ; f, middle or soft commissure : g, 
 3d ventricle ; h, i, corpora quadrigemina ; k, superior cerebellar peduncle ; /, hippocampus major ; tn t posterior 
 cornu of lateral ventricle : n, eminentia collateralis ; 0, 4th ventricle ; /, medulla oblongata ; s, cerebellum, with 
 r, arbor vitae. 
 
 are further subdivided by sulci into convolutions. For a description of the lobes, see \ 375. Some 
 masses of gray matter are disposed at the base of the brain, forming the corpus striatum (pro- 
 jecting into the lateral ventricles), which, in reality, is composed of two parts — the nucleus caudatus 
 and lenticular nucleus (Fig. 409, b) ; the optic thalamus, which lies behind the former and bounds 
 the 3d ventricle (Fig. 409, d) ; the corpora quadrigemina, lying on the upper surface of the crura 
 cerebri (Fig. 409, A, i) ; and within the tegmentum of the crura cerebri are the red nucleus and 
 locus niger. Lastly, there is the continuation of the gray matter of the cord up through the 
 medulla, pons, and around the iter, forming the central gray tube and terminating anteriorly at 
 the tuber cinereum. These various parts are connected in a variety of ways with each other, some 
 
 675 
 
676 
 
 PROJECTION SYSTEMS OF MEYNERT. 
 
 by transverse fibres stretching between the two sides of the brain, while other longitudinal fibres 
 bring the hinder and lower parts in relation with the fore parts.] 
 
 [Under cover of the occipital lobes, but connected with the cerebrum in front and the spinal cord 
 below, is the cerebellum, which has its gray matter externally and its white core internally. Thus, 
 we have to consider cerebro-spinal and cerebello-spinal connections.] 
 
 Meynert's Projection Systems. — The cortex of the cerebium consists of convolutions and 
 
 Fig. 410. 
 
 I, Scheme of the brain. C, C, cortex cerebri ; C, $, corpus striatum ; N, /, nucleus lenticularis ; T, o, optic thal- 
 amus ; v, corpora quadrigemina; P, pedunculus cerebri ; H, tegmentum; and/, crusta; 1,1, corona radiataot 
 the corpus striatum ! 2,2., of the lenticular nucleus; 3, 3, of the optic thalamus; 4, 4, of the corpora quadrigemina ; 
 5, direct fibres to the cortex cerebri (Mechsig) ; 6, 6, fibres from the corpora quadrigemina to the tegmentum ; 
 m, further course of these fibres ; 8, 8, fibres from the corpus striatum and lenticular nucleus to the crusta of the 
 pedunculus cerebri; M, further course of these; S,S, course of the sensory fibres; R, transverse section of the 
 spinal cord ; v, W, anterior, and A, W, posterior roots ; a. a, association system of fibres ; c, c, commissural 
 fibres. II, Transverse section through the posterior pair of the corpora quadrigemina and the pedunculi cerebri 
 of man, — p, crusta of the peduncle; s, substantia nigra :. v, corpora quadrigemina, with a section ot the aqueduct. 
 Ill, The same of the dog ; IV, of an ape ; V, of the guinea pig. [See p. 675.] 
 
 sulci, the " peripheral gray matter " (Fig. 410, C), which is recognized as a nervous structure 
 from the presence of numerous ganglionic cells in it (§ 358, 1). From it proceed all the motor 
 fibres which are excited by the will, and to it proceed all the fibres comina; from the organs of 
 special sense and sensory organs, which give rise to the psychical perception of external impressions. 
 [In Fig. 410 the decussation of the sensory fibres is represented as occurring near the medulla 
 oblongata. It is more probable that a large number of the sensory fibres decussate shortly after 
 
CEREBELLOSPINAL CONNECTIONS. 
 
 677 
 
 they enter the cord, as is represented in Fig. 412. Some observers assert that some of the sensory 
 fibres decussate in the medulla oblongata.] 
 
 First Projection System. — The channels lead to and from the cortex cerebri, some of them 
 traversing the basal ganglia, or ganglia of the cerebrum, the corpus striatum ( C, s), composed of 
 the caudate nucleus and lenticular nucleus ( N, I), optic thalamus ( T, o) and corpora quadrigemina ; 
 some fibres form connections with cells within this central gray matter. The fibres which proceed 
 from the cortex through the corona radiata in a radiate direction constitute Meynert' s first projection 
 system. Besides these, the white substance also contains two other systems of fibres : (a) Commis- 
 sural fibres, such as the corpus callosum and the anterior commissure (c, c), which are supposed to 
 connect the two hemispheres with each other ; and (i) a connecting or association system, whereby 
 two different areas of the same side are connected together [a, a). The ganglionic gray matter of 
 the basal ganglia forms the first stage in the course of a large number of the fibres. When they 
 enter the central r gray matter they are interrupted in their course. According to Meynert, the 
 corona radiata contains bundles of fibres from the corpus striatum, lenticular nucleus, optic thalamus 
 and corpora quadrigemina. 
 
 The second projection system consists of longitudinal bundles of fibres, which proceed down- 
 ward and reach the so-called " central gray tube," which is the ganglionic gray matter reaching 
 from the 3d ventricle through the aqueduct of Sylvius and the medulla oblongata to the lowest part 
 of the gray matter of the spinal cord. It lines the inner surface of the medullary tube. It is the 
 
 Fig. 411. 
 
 Floor of the fourth ventricle and the connections of the cerebellum. On the left side the three cerebellar peduncles 
 are cut short ; on the right the connections of the superior and inferior peduncles have been preserved, while the 
 middle one has been cut short. 1, median groove of the fourth ventricle with the fasciculi teretes ; 2, the stria: 
 of the auditory nerve on each side emerging from it ; 3, inferior peduncle ; 4, posterior pyramid and clava, with 
 the calamus scriptorius above it ; 5, superior peduncle ; 6, fillet to the side of the crura cerebri ; 8, corpora quad- 
 rigemina. 
 
 second stage in the course of the fibres extending from the basal ganglia to the central tubular gray 
 matter. The fibres of this system must, obviously, vary greatly in length. 
 
 [While there are three concentric tubes in the spinal cord (§ 359,),. in the part which forms the 
 brain an extra layer of gray matter is added— the peripheral gray tube — constituting the cortex of 
 the cerebral hemispheres and cerebellum and the corpora quadrigemina. Thus, the white matter 
 lies between two concentric masses of gray matter (Hill).'] 
 
 Connections of the Cerebellum. —The cerebellum consists of two somewhat flattened hemi- 
 spheres connected across the middle line by the middle lobe or vermiform process, which is the 
 fundamental portion of the organ, as it is best developed in lower animals, while as yet the lateral 
 lobes are but small or absent, e. g., in birds. The surface is furrowed by sulci so as to cause it to 
 resemble a series of folia, leaflets or laminae ; larger fissures divide it into lobes. Peduncles. — 
 The two superior peduncles connect it with the corpora quadrigemina and the crura cerebri. The 
 fibres come from the lower part of the cerebellum and from its dentate nucleus, and the greater por- 
 tion of these fibres decussate inthe upper part of the pons and the tegmentum, some of them be- 
 coming connected with the red nucleus in the tegmentum of the opposite side. Some of the fibres 
 seem to connect the cerebellum with the frontal lobes, constituting a fronto-cerebellar tract, and they 
 are also crossed ( Gowers). When the cerebellum is congenitally absent these fibres are absent 
 (Flechsig). By the two inferior peduncles or restiform bodies, it is connected with all the columns 
 
678 CEREBROSPINAL CONNECTIONS. 
 
 of the spinal cord, and it is to be noted that some of the fibres forming these peduncles are con- 
 nected with the olivary body of the opposite side, so that they decussate. The middle peduncle is 
 formed by the transverse fibres of the pons (Fig. 411). It is evident that there is a cerebello spinal 
 as well as cerebro-spinal connection to be considered. 
 
 [The gray matter is external and the white internal, and on section the foliated branched ap. 
 pearance of the cerebellum constitutes the arbor vita. Within each lateral lobe is a folded mass of 
 gray matter like that in the olivary body, called the corpus dentatum, and from its interior white 
 fibres proceed. Stilling describes roof nuclei in the front part of the middle lobe, so called be- 
 cause they lie in the roof of the fourth ventricle. As is shown in Fig. 411, the white fibres of 
 the superior peduncle pass to the gray matter on the inferior surface of the cerebellum, while the 
 inferior peduncular fibres pass to the superior surface, chiefly of the median part ; but both are said 
 to form connections with the corpus dentatum ; the middle peduncle is connected with the gray 
 matter of the lateral lobes. The minute structure is described in § 380.] 
 
 The Third Projection System. — Lastly, from the central tubular gray matter there proceeds 
 the third system, or the peripheral nerves, motor and sensory. They are more numerous.than the 
 fibres of the second system. 
 
 Conduction to and from Cerebrum — Voluntary Motor Fibres. — 
 The course of the fibres which convey impulses for voluntary motion — the pyra- 
 midal tracts — proceed from the motor regions of the cerebrum (§§ 375, 378, 1), 
 passing into and through the white matter of the cerebrum, and converge 
 to the internal capsule, which lies between the nucleus caudatus and opticus 
 thalamus internally and the lenticular nucleus externally (Fig. 439). [The 
 motor fibres for the face and tongue occupy the knee of the capsule (F), those for 
 the arm the anterior third of the posterior segment or limb (A), and those for the 
 leg the middle third (L). They enter the cms and occupy its middle third, the 
 fibres for the face being next the middle line, and those for the leg most external, 
 the fibres for the arm lying between the two. They pass into the pons, where the 
 fibres for the face (and tongue) cross to the opposite side, to become connected 
 with the nuclei from which the facial and hypoglossal nerves arise. The fibres for 
 the arm and leg (and trunk) continue their course to the medulla oblongata, where 
 they form the anterior pyramids.] By far the greater proportion of the fibres 
 cross at the decussation of the pyramids to form the crossed pyramidal tracts 
 or lateral pyramidal tracts of the lateral column of the opposite side. The small 
 uncrossed portion is continued as the direct pyramidal tract on the same side. 
 The latter fibres, perhaps, supply those muscles of the trunk (<?. g. , respiratory, 
 abdominal, and perineal), which always act together on both sides. According 
 to other observers, however, they cross to the other side of the cord through the 
 anterior white commissure, and descend in the crossed pyramidal tract or pyra- 
 midal tract of the lateral column. The fibres of the pyramidal tracts form con- 
 nections with the multipolar ganglionic cells of the anterior cornu of the gray 
 matter of the spinal cord at successively lower levels, and from each multipolar cell 
 a single unbranched process is directed peripherally, which ultimately becomes a 
 nerve fibre. The pyramidal tracts thus end in the multipolar nerve cells of the gray 
 matter of the spinal cord, from which the anterior roots of the spinal nerves arise. 
 
 [The course of the pyramidal tracts and the decussation of these fibres in the 
 medulla oblongata, explains why a hemorrhage involving the cerebral motor 
 centres, or affecting these- fibres in any part of their course above the decussation, 
 results in paralysis of the muscles supplied by the fibres so involved on the opposite 
 side of the body.] 
 
 In their passage through the brain, the paths for direct motor impulses are not interrupted any- 
 where in their course by ganglion cells, not even in the corpus striatum or pons. They pass in a 
 direct uninterrupted course [so that they have the longest course of any fibres in the central nervous 
 system]. 
 
 Variation in Decussation. — There are variations as to the number of fibres which cross at the 
 pyramids {Flechsig). In some cases the usual arrangement is reversed, and in some rare instances 
 there is no decussation, so that the pyramidal tracts from the brain remain on the same side. In 
 this way we may explain the very rare cases where paralysis of the voluntary movements takes place 
 on the same side as the Usion of the cerebrum [Morgagni, Pierrel). This is direct paralysis. 
 [Usually about 90 per cent, of the fibres decussate.] 
 
COURSE OF THE SENSORY NERVES. 679 
 
 The motor cranial nerves have the centres through which they are excited 
 voluntarily in the cortex cerebri (§ 378). The paths for such voluntary impulses 
 also pass through the internal capsule and the crusta of the cerebral peduncle. [In 
 the internal capsule the fibres for the face (and tongue) lie in the knee, while they 
 occupy the part of the middle of the crusta next the middle line. Their course 
 is then directed across the middle line to their respective nuclei, from which fibres 
 proceed to the muscles supplied by these nuclei.] The exact course of many of 
 the fibres is still unknown. The hypoglossal nerve runs with the pyramidal tracts, 
 and behaves like the anterior root of a spinal nerve (§§ 354, 357). 
 
 [Sensory Paths. — Our knowledge is by no means precise. Sensory impulses, 
 passing into the cord, enter it by the posterior nerve roots, and may pass to the 
 cerebrum or cerebellum. If to the cerebellum, the course probably is partly to 
 the direct cerebellar tract and posterior column to the restiform body, thence to 
 the cerebellum. If t'p the cerebrum, they cross the middle line in the cord not 
 far above where they enter and pass to the lateral column, in front of the pyra- 
 midal tract. Some enter the posterior column and others ascend in the gray matter 
 to pass upward. In the medulla it is probable that those fibres which do not de- 
 cussate there do so in the pons, the impulses perhaps traveling upward in the 
 formatio reticularis, thence into the posterior half of the pons, into the tegmentum 
 of the crus under the corpora quadrigemina, to enter the posterior third of the 
 posterior limb of the internal capsule (Fig. 439, S). But, of course, the sensory 
 fibres from the face have to be connected with the sensory centres in the cerebrum, 
 so that the sensory paths from the cord, i. e. , from the trunk and limbs are joined 
 by those from the face in the pons, and they also occupy part of the posterior 
 third of the posterior segment of the internal capsule, so that this important part • 
 of the internal capsule conducts sensory impulses from the opposite half of the 
 body. Some of the fibres pass into the optic thalamus, and others enter the white 
 matter of the cerebrum, but their exact course is very uncertain. The sensory 
 fibres derived from the organs of special sense, e. g., the ear, go to the superior 
 temporo-sphenoidal convolution, but whether directly or indirectly we do not 
 know ; perhaps some of those for vision traverse the optic thalamus. Some of the 
 afferent fibres perhaps go to the occipital region, and Gowers asserts that some of 
 them go to the parietal and central regions, *'. e., to the "motor" regions, for 
 he holds "that disease of the motor cortex often causes impairment of the tactile 
 sensibility."] 
 
 [Charcot has called the posterior third of the posterior segment of the internal 
 capsule, lying between the posterior part of the lenticular nucleus and the optic 
 thalamus, the " Carrefour Sensitiv " or " Sensory Crossway " (Fig. 439, Sj. 
 If it be divided, there is hemiansesthesia of the opposite side.] 
 
 Sensory Decussation in Cord. — As the greater part of the sensory fibres 
 from the skin decussate in the spinal cord, and thus pass to the opposite side of 
 the cord (Fig. 41 2), unilateral section of the spinal cord in man (and monkey — 
 Ferrier) abolishes sensibility on the opposite side below the lesion. There is 
 hyperesthesia of the parts below the seat of the section on the side of the injury 
 (§ 3^3)- From experiments on mammals, Brown-Sequard concludes that the de- 
 cussating sensory nerve fibres pass to the opposite side within the cord at different 
 levels, the lowest being the fibres for touch, then those for tickling and pain, and, 
 highest of all, those which administer to sensations of temperature. 
 
 All the fibres, therefore, which connect the spinal cord with the gray matter of 
 the brain, undergo a complete decussation in their course. Hence, in man a de- 
 structive affection of one hemisphere usually causes complete motor paralysis and 
 loss of sensibility on the opposite side of the body. The fibres proceeding from 
 the nuclei of origin of the cranial nerves also cross within the cranium. 
 
 Not unfrequently the motor paralysis and anaesthesia occur on the same side of the head, in which 
 case the lesion (due to pressure or inflammation} involves the cranial nerves lying at the base of the 
 brain. 
 
680 
 
 CONDUCTING PATHS IN THE SPINAL CORD. 
 
 The positions of decussation are (i) in the spinal cord, (2) in the medulla oblongata, and, 
 lastly (3), in the pons. The decussation is complete in the peduncle. 
 
 Diagram of a spinal segment as a spinal centre and conducting medium. B, right, B', left cerebral hemisphere ; MO, 
 lower end of medulla oblongata ; 1, motor tract from the right hemisphere, the larger part decussating at MO, and 
 passing down the lateral column of the cord on the opposite side to the muscles M and M' ; 2, motor tract from 
 the left hemisphere; S, S', sensitive areas on the left side of the body; 3', 3, the main sensory tract from the left 
 side of the body — it decussates shortly after entering the cord ; S a , S 3 , sensitive areas, and 4', 4, tracts from the 
 right side of the body. The arrows indicate the direction of the impulses {Bramwell)). [Here all the sensory 
 fibres are shown as crossing the cord.] 
 
THE MEDULLA OBLONGATA. 
 
 681 
 
 Alternate Paralysis. — Gubler observed that unilateral injury to the pons caused paralysis of the 
 facial nerve on the same side, but paralysis of the opposite half of the body. He concluded that 
 the nerves of the trunk decussate before they reach the pons, while the facial fibres decussate within 
 the pons. To these rare cases the name " alternate hemiplegia " is given. [When hemorrhage 
 takes place into the lower part of the lateral half of the pons, there may be alternate paralysis, but 
 when the upper part of the lateral half is injured, the facial is paralyzed on the same side as the 
 body, § 379.] 
 
 The olfactory nerve is said not to decussate (?) while the optic nerve undergoes a partial decus- 
 sation at the chiasma (§ 344). Some observers assert that the fibres of the trochlearis decussate at 
 their origin. 
 
 366. THE MEDULLA OBLONGATA.— [Structure.— In the medulla oblongata the 
 fibres from the cord are rearranged, the gray matter is also much changed, while new gray matter 
 is added. Each half of the medulla oblongata consists of the following parts from before back- 
 wards : The anterior pyramid, olivary body, restiform body, and posterior pyramid, or 
 funiculus gracilis (Figs. 413, 414, 415). By the divergence of the posterior pyramids and the resti- 
 form bodies, the floor of the 4th ventricle is exposed. As the central canal of the cord gradually 
 
 fn- 
 
 Section of the decussation of the pyramids. Jla , anterior median fissure, displaced laterally by the fibres decussating - 
 atrf; V, anterior column; C'a, anterior cornu, with its nerve cells, a, 6 cc, central canal; £, lateral column; 
 fr, formatio reticularis ; ce, neck, and g, head ot the posterior cornu ; rpCl, posterior root of the zst cervical . 
 nerve ; nc, first indication of the nucleus of the funiculus cuneatus ; ng, nucleus (clava) of the funiculus gracilis ; 
 H l , funiculus gracilis; II' 1 , funiculus cuneatus; sip, posterior median fissure; x, groups of ganglionic cells in 
 the base of the posterior cornu. X 6. 
 
 comes nearer to the posterior surface of the medulla it opens into the 4th ventricle. At the lower 
 end of the medulla oblongata, on separating the anterior pyramids, we may see the decussation . 
 of the pyramids where the fibres cross over to the lateral columns of the cord. The anterior 
 pyramid receives the direct pyramidal tract of the anterior column of the cord from its own side, 
 and the crossed pyramidal tract from the lateral column of the cord of the opposite side (Fig. 413). 
 The decussating fibres (crossed pyramidal tract) of the lateral column pass across in bundles to ■ 
 form the decussation of the pyramids. Most of the pyramidal fibres pass through the pons directly 
 to the cerebrum, a few fibres pass to the cerebellum, while some join fibres proceeding from the 
 olivary body to form the olivary fasciculus or fillet.] 
 
 [Thus only a part of the anterior column of the cord — direct pyramidal tract — is continued into 
 the anterior pyramid, where it lies external to the fibres which pass to the lateral column of the . 
 opposite side. The remainder of the anterior column — the antero-external fibres — are continued 
 upward, but lie deeper under cover of the anterior pyramid, where they serve to form part of the 
 formatio reticularis (p. 682).] 
 
 [Of the fibres of the lateral column of the cord, some, the direct cerebellar tract, pass backward 
 
682 STRUCTURE OF THE MEDULLA OBLONGATA. 
 
 to join the restiform body and go to the cerebellum. These fibres lie as a thin layer on the surface 
 of the restiform body. The crossed pyramidal fibres cross obliquely at the lower end of the medulla 
 to the anterior pyramid of the opposite side, and in their course they traverse the gray matter of 
 the anterior cornu (Fig. 413, py). These fibres form the larger and mesial portion of the anterior 
 pyramid. The remaining fibres of the lateral columns are continued upward, and pass beneath 
 the olivary body, where they are concealed by this structure and also by the arcuate fibres, but they 
 appear in the floor of the medulla oblongata and are called fasciculus teres, which goes to the cere- 
 brum. As they pass upward they help to form the lateral part of the formatio reticularis.] 
 
 [The posterior pyramid of the oblongata is merely the upward continuation of the postero- 
 median column, or funiculus gracillis of the cord. As it passes upward at the medulla it broadens 
 out, forming the clava, which tapers away above. The clava contains a mass of gray matter — the 
 clavate nucleus.] 
 
 [The restiform body consists chiefly of the upward continuation of the postero-external column 
 or funiculus cuneatus of the cord. It contains a mass of gray matter, called the cuneate or tri- 
 angular nucleus. Above the level of the clava the funiculus cuneatus forms part of the lateral 
 boundary of the 4th ventricle. Immediately outside this, i.e., between it and the continuation of 
 the posterior nerve roots, is a longitudinal prominence, which Schwalbe has called the funiculus 
 of Rolando. It is formed by the head of the posterior cornu of gray matter coming nearer the 
 surface. It also forms part of the restiform body. Some arcuate fibres issue from the anterior 
 median fissure, turn transversely outward over the anterior pyramids and olivary body, and pass 
 along with the funiculus cuneatus, the funiculus of Rolando, and the direct cerebellar fibres, to 
 enter the corresponding lateral lobe of the cerebellum, all these structures forming its inferior 
 peduncle. Some observers suggest that the funiculus cuneatus and funiculus of Rolando do not pass 
 into the cerebellum.] 
 
 [The olivary body forms a well-marked oval or olive-shaped body, which does not extend the 
 whole length of the medulla (Fig. 415, 0). Above, it is separated from the pons by a groove from 
 which the 6th nerve emerges. In the groove between it and the anterior pyramid arise the strands 
 of the hypoglossal nerve, while in a corresponding groove along its outer surface is the line of exit 
 of the vagus, glossopharyngeal, and spinal accessory nerves. It is covered on its surface by longi- 
 tudinal and arcuate fibres, while in its interior it contains the dentate nucleus.] 
 
 [The functions of the olivary bodies are quite unknown, but it is important to remember that 
 they are connected by fibres with the dentate nuclei of the cerebellum. Fibres pass injo the olivary 
 body from the posterior column of the cord of the opposite side, and it is also connected with the 
 dentate body of the' opposite side, while, as we know, the dentate body is connected with the teg- 
 mentum, so that through the left dentate body of the opposite side the tegmentum of say the right 
 crus is connected with the right olivary body (Gmaers).] 
 
 [Decussation of the Pyramids is the term given to those fibres which cross obliquely in 
 several bundles at the lower part of the medulla from the anterior pyramid of the medulla into the 
 lateral column of the cord of the opposite side (Fig. 413, d) to form its lateral pyramid tracts or 
 crossed pyramidal tracts. The number of fibres which decussate varies, and in some cases all the 
 fibres may cross.] , 
 
 [The gray matter of the medulla is largely a continuation of that of the cord, although it is 
 arranged differently. As the fibres from the lateral column of the cord pass over to form part of the 
 anterior pyramid of the medulla on the opposite side, they traverse the gray matter, and thus cut 
 off the tip of the anterior cornu, which is also pushed backward by the olivary body, and exists as 
 a distinct mass, the nucleus lateralis (Fig. 414, »/). Part of the anterior gray matter also appears 
 in the floor of the 4th ventricle as the eminence of the fasciculus teres, and from part of it springs 
 the hypoglossal nerve (Fig. 415, XII). The neck joining the modified anterior and posterior 
 cornua is much broken up by the passage of longitudinal and transverse fibres through it, so that it ■ 
 forms a formatio reticularis (Fig. 414, fr), separating the two cornua. The caput cornu posterioris 
 comes to be covered higher up by the ascending root of the 5th nerve (Fig. 414, a V), and arcuate 
 fibres passing to the restiform body. The posterior cornu is also broken up and is thrown outward, 
 its caput giving rise to part of the elevation seen on the surface and described as the funiculus of 
 Rolando, while part of the base now greatly enlarged forms the gray matter in the funiculus gracilis 
 [clavate nucleus] (Fig. 413, ng) and funiculus cuneatus [cuneate or triangular nucleus] (Fig. 413, 
 nc). Nearer the middle line, the gray matter of the posterior gray cornu appears in the floor of 
 the 4th ventricle, above where the central canal opens into it, as the nuclei of the spinal accessory, 
 vagus and glossopharyngeal nerves.] 
 
 [In the floor of the 4th ventricle near the raphe, and quite superficial, is a longitudinal mass of 
 large multipolar nerve cells, derived from the base of the anterior cornu from which the several 
 bundles forming the hypoglossal nerve springs, it is the hypoglossal nucleus (Fig. 415, nXII), 
 the nerve fibres passing obliquely outward to appear between the anterior pyramid and the olivary 
 body. Internal to it and next the median groove is a small mass of cells continuous with those in 
 the raphe, and called the nucleus of the funiculus teres (Fig. 415, nt). Around the central canal 
 at the lower part of the medulla is a group of cells (Fig. 415, nXI), which becomes displaced lat- 
 erally as it comes nearer the surface in the floor of the medulla oblongata, where it lies outside the 
 hypoglossal nucleus, and corresponds to the prominence of the ala cinerea (Fig. 415, nX), and 
 
THE GRAY MATTER OF THE MEDULLA OBLONGATA. 
 
 683 
 
 from it and its continuation upward arise from below upward part of the spinal accessory (nth), 
 and the vagus (loth, corresponding to the position of the eminentia cinerea— Fig. 415, JC), so that 
 this column of cells forms the vago-accessorius nucleus. External to and in front of this is the 
 nucleus for the glosso-pharyngeal nerve. Further up in the medulla, on a level with the auditory 
 strise and outside the previous column, is a tract of cells from which the auditory nerve (8th) in great 
 part arises ; it is the principal auditory nucleus. It lies just under the commencement of the 
 inferior cerebellar peduncle (Fig. 384, 8' 8" %'"). It consists of an outer and inner nucleus, which 
 extend to the middle line. It forms connections with the cerebellum, and some fibres are said to 
 enter the inferior cerebellar peduncle. This is an important relationship, as we know that the ves- 
 tibular branch of the auditory nerve comes partly from the semicircular canals, so that in this way 
 these organs may be connected with the cerebellum.] 
 
 [Superadded Gray Matter. — There is a superadded mass of gray matter not represented in the 
 cord, that of the olivary body, enclosing a nucleus, the corpus dentatum, with its wavy strip of 
 gray matter containing many small multipolar nerve cells embedded in neuroglia. The gray matter 
 is covered on the surface by longitudinal and transverse fibres. It is open toward the middle line 
 
 Fig. 414. 
 dp. ?' "7 O' n.e. 
 
 Fig. 415. 
 nM i t/ ft /* 
 
 n.c. 
 
 n.ar 
 
 Fig. 414. — Section of the medulla oblongata at the so-called upper decussation of the pyramids. fia, anterior 
 sip, and posterior median fissure ; nJil, nucleus of the accessorius vagi ; nXII, nucleus of the hypoglossal ; da, 
 the so-called superior or anterior decussation of the pyramids ; py, anterior pyramid ; n, Ar, nucleus arciformis ; 
 O 1 , median parolivary body ; O, beginning of the nucleus of the olivary body ; nl, nucleus of the lateral column ; 
 Fr, formatio reticularis; g, substantia gelatinosa, with \aV) the ascending root of the trigeminus; nc, nucleus 
 of the funiculus cuneatus ; nc 1 , external nucleus of the funiculus cuneatus ; ng, nucleus of the funiculus gracilis 
 (orclava); f/ 1 , funiculus gracilis; H 3 , funiculus cuneatus; cc, central canal; /a, /a 1 , /a 9 , external arciform 
 fibres X 4. FlG- 4*5- — Section of the medulla oblongata through the olivary body. nXII, nucleus of the hypo- 
 glossal ; nX, nX x , more or less cellular parts of the nucleus of the vagus ; XII, hypoglossal nerve ; X, vagu* ; 
 n, am, nucleus ambiguus; til, nucleus lateralis ; o, olivary nucleus; oal, external, and cam, internal parolivary 
 body ; /s, the round bundle, or funiculus solitarius ; Cr, restiform body ; p, anterior pyramid, surrounded by 
 arciform fibres ; fan, pal, fibres proceeding from the olive to the raphe (pedunculus oliva:) ; r, raphe. X 4- 
 
 (hilum) and into it run white fibres forming its peduncle (Fig. 415,/, 0, 1). These fibres diverge 
 like a fan, some of them ending in connection with the small multipolar cells of the dentate body, 
 while others traverse the lamina of gray matter and pass backward to appear as arcuate fibres which 
 join the restiform body ; others, again, pass directly through to the surface of the olivary body, which 
 they help to cover as the superficial arcuate fibres. The accessory olivary nuclei (Fig. 414, 0', 
 0") are two small masses of gray matter similar to the last, and looking as if they were detached 
 from it, one lying above and external, sometimes called the parolivary body, and the other slightly 
 below and internal to the olivary nucleus, the latter be:ng separated from the dentate body by the 
 roots of the hypoglossal nerve. The latter is sometimes called internal parolivary body, or nucleus 
 of the pyramid. ] 
 
 [The formatio reticularis occupies the greater part of the central and lateral parts of the me- 
 dulla, and is produced by the intercrossing of bundles of fibres running longitudinally and more or 
 less transversely in the medulla (Fig. 414,/; r). In the more lateral portions are large multipolar 
 nerve cells, perhaps continued upwar.t fmm part of the anterior cornu, while the part next the raphe 
 has no such cells. The longitudinal fibres consist of the upward prolongation of the antero-external 
 
684 FUNCTIONS OF THE MEDULLA OBLONGATA. 
 
 columns of the cord, while some seem to arise from the clavate nuclei and olives as arcuate fibres 
 passing upward. In the lateral portions, the longitudinal fibres are the direct continuation upward 
 of Flechsig's anterolateral mixed tracts of the lateral columns (p. 659). The horizontal fibres are 
 formed by arcuate fibres, some of which run more or less transversely outward from the raphe. The 
 superficial arcuate fibres (Fig. 415,/, a, e) appear in the anterior median fissure, and, perhaps, come 
 through the raphe from the opposite side of the medulla, curve round the anterior pyramids, form a 
 kind of capsule for the olives, and join the restiform body (p. 682), but they are reinforced by some 
 of the deep arcuate fibres which traverse the olivary body ( p. 682). The deep arcuate fibres run 
 from the clavate and triangular nuclei horizontally inward to the raphe and cross to the other side, 
 others pass from the raphe to the olivary body and through it to the restiform body. In the raphe, 
 which contains nerve cells, some fibres run transversely, others longitudinally, and others from before 
 backward.] 
 
 [Other Nerve Nuclei — Sixth Nerve. — Under the elevation called eminentia teres (Fig. 384) 
 in front of the auditory striae, close to the middle line, is a tract of large multipolar nerve cells. It 
 was once thought to be the common nucleus of 6th and 7th facial nerves, but Gowers has shown 
 that " the facial ascends to this nucleus, forms a loop round it (some fibres, indeed, go through it), 
 and then passes downward, forward and outward to a column of cells more deeply placed in the 
 medulla than any other nucleus in the lower part." But the 7th has no real origin from this nucleus. 
 Facial Nerve. — The nucleus lies deep in the formatio reticularis of the pons under the floor of 
 the 4th ventricle, but outside the position of the nucleus of the 6th (Fig. 384, 7). It extends down- 
 ward about as far as the auditory striae or a little lower. The fifth nerve arises from its motor 
 nucleus (with large multipolar cells), which lies more superficially above and external to the 6th 
 (Fig. 384, 5). The fibres run backward, where they are joined by fibres from the upper sensory 
 nucleus, but another sensory nuc'eus extends down nearly to the lower end of the medulla (5"). 
 Doubtless, this extensive origin brings this nerve into intimate relation with the other cranial nerves, 
 and accounts for the numerous reflex acts which can be discharged through the 5th nerve. Some 
 sensory fibres are said to pass up beneath the corpora quadrigemina ( Gowers). The fourth nerve 
 arises from the valve of Vieussens, i. e., the lamina of white and gray matter which stretches between 
 the superior cerebellar peduncles. It arises, therefore, behind the 4th ventricle, but some of the 
 fibres spring from some nerve cells at the lower part of the nucleus of the 3d nerve. Some fibres 
 also descend in the pons to form a connection with the nucleus of the 6th nerve. The fibres decus- 
 sate behind the aqueduct, so that in it alone, of all the cranial nerves, decussation occurs between its 
 nucleus and its superficial origin {Gowers). The third nerve arises from a tract of cells beneath 
 the aqueduct and near the middle line, and the fibres descend through the tegmentum to appear at 
 the inner side of the crus cerebri. Gowers points out that, in reality, there are three distinct func- 
 tional centres, (1) for accommodation (ciliary muscle), (2) for the light reflex of the iris, and (3) 
 most of the external muscles of the eyeball. It is important to notice the connection between the 
 nuclei of the 3d, 4th and 6th nerves, in relation to innervation of the ocular muscles.] 
 
 Functions. — The medulla oblongata, which connects the spinal cord with the 
 brain, has many points of resemblance with the former. [Like the cord, it is 
 concerned in the (1) conduction of impulses.] (2) In it numerous reflex cen- 
 tres are present, e. g. , for simple reflexes similar to the nerve centres in the spinal 
 cord, e.g., closure of the eyelids [so that they subserve the transference of afferent 
 into efferent impulses]. There are other centres present which seem to dominate 
 or control similar centres placed in the cord, e. g., the great vasomotor centre, the 
 sweat-secreting, pupil-dilating centres, and the centre for combining the reflex 
 movements of the body. Some of the centres are capable of being excited re- 
 flexly (§ 358, 2). (3) It is also said to contain automatic centres (§ 358, 3). 
 The normal functions of the centres depend upon the exchanges of blood 
 gases effected by the circulation of the blood through the medulla. If this 
 gaseous exchange be interrupted or interfered with, as by asphyxia, sudden anaemia 
 or venous congestion, these centres are first excited, and exhibit a condition of 
 increased excitability, and, if they are over-stimulated, at last they are paralyzed. 
 An excessive temperature also acts as a stimulus. All the centres, however, are 
 not active at the same time, and they do not all exhibit the same degree of ex- 
 citability. Normally, the respiratory centre and the vasomotor centre are con- 
 tinually in a state of rhythmical activity. In some animals the inhibitory centre 
 of the heart remains continually non-excited, in others it is stimulated very slightly 
 under normal conditions, simultaneously with the stimulation of the respiratory 
 centre and only during inspiration. The spasm centre is not stimulated under 
 normal conditions, and during intra-uterine life the respiratory centre remains 
 quiescent. The medulla oblongata, therefore, contains a collocation of nerve 
 
CENTRES IN THE MEDULLA OBLONGATA. 685 
 
 centres which are essential for the maintenance of life, as well as various conduct- 
 ing paths of the utmost importance. We shall treat of the reflex, and afterward of 
 the automatic centres. 
 
 367. REFLEX CENTRES OF THE MEDULLA OBLONGATA. 
 
 — The medulla oblongata contains a number of reflex centres, which minister to 
 the discharge of a large number of coordinated movements. 
 
 1. Centre for Closure of the Eyelids. — The sensory branches of the 5th 
 cranial nerve to the cornea, conjunctiva, and the skin in the region of the eye are 
 the afferent nerves. They conduct impulses to the medulla oblongata, where 
 they are transferred to, and excite part of, the centre of the facial nerve, and 
 through branches of the facial the efferent impulses are conveyed to the orbicu- 
 laris palpebrarum. The centre lies close to the calamus scriptorius (Exner). 
 
 The reflex closure of the eyelids always occurs on both sides, but closure may be produced volun- 
 tarily on one side (winking). When the stimulation is strong, the corrugator and other groups of 
 muscles which raise the cheek and nose toward the eye may also contract, and so form a more 
 perfect protection and closure of the eye. Intense stimulation of the retina causes closure of the 
 eyelids [and in this case the shortest reflex known, the latent period, is 0.5 second ( Waller)']. 
 
 2. Sneezing Centre. — The afferent channels are the internal nasal branches 
 of the trigeminus and the olfactory, the latter in the case of intense odors. The 
 efferent or motor paths lie in the nerves for the muscles of expiration (§§ 1 20, 
 3, and 347, II). Sneezing cannot be performed voluntarily [but it may be inhib- 
 ited by compressing the nasal nerve at its exit on the nose]. 
 
 3. Coughing Centre. — According to Kohts, it is placed a little above the 
 inspiratory centre ; the afferent paths are the sensory branches of the vagus 
 (§352, 5, a). The efferent paths lie in. the nerves of expiration and those that 
 close the glottis (§120, i). 
 
 4. Centre for the Movements of Sucking and Mastication. — The 
 afferent paths lie in the sensory branches of the nerves of the mouth and lips 
 (2d and 3d branches of the trigeminus and glosso-pharyngeal). The efferent 
 nerves for suction (§ 152) are : Facial for the lips, hypoglossal for the tongue, the 
 inferior maxillary division of the trigeminus for the muscles which elevate and 
 depress the jaw. For the movements of mastication the same nerves are in action 
 (§ !S3)j Dut when food passes within the dental arch the hypoglossal is concerned 
 in the movements of the tongue, and the facial for the buccinator. 
 
 5. Centre for the Secretion of Saliva (p. 241), which lies in the floor of 
 the 4th ventricle. Stimulation of the medulla oblongata causes a profuse secre- 
 tion of saliva, when the chorda tympani and glosso-pharyngeal nerves are intact, 
 a much feebler secretion when the nerves are divided, and no secretion at all 
 when the cervical sympathetic is extirpated at the same time (Griitzner). 
 
 6. Swallowing Centre in the floor of the 4th ventricle (§ 156). — The 
 afferent paths lie in the sensory branches of the nerves of the mouth, palate, 
 and pharynx (2d and 3d branches of the trigeminus, glosso-pharyngeal, and 
 vagus) ; the efferent channels in the motor branches of the pharyngeal plexus 
 (§ 352. 4)- 
 
 According to Steiner, every time we swallow there is a slight stimulation of the respiratory centre, 
 resulting in a slight contraction of the diaphragm. [Kronecker has shown that if a glass of water 
 be sipped slowly, the action of the cardio-inhibitory centre is interfered with reflexly, so that the 
 heart beats much more rapidly, whereby the circulation is accelerated, hence probably why sipping 
 an alcoholic drink intoxicates more rapidly than when it is quickly swallowed.] 
 
 7. Vomiting Centre (§ 158). — The relation of certain branches of the vagus 
 to this act are given at § 352, 2, and 12, d. 
 
 8. The upper centre for the dilator pupillae muscle, the smooth muscles 
 of the orbit, and the eyelids lies in the medulla oblongata. The fibres pass out 
 partly in the trigeminus (§ 347, I, 3), partly in the lateral columns of the spinal 
 cord as far down as the cilio-spinal region, and pass out by the two lowest cervical 
 
686 POSITION OF THE RESPIRATORY CENTRE. 
 
 and the two upper dorsal nerves into the cervical sympathetic (§ 356, A, 1). The 
 centre is normally excited reflexly by shading the retina, i. e., by diminishing 
 the amount of light admitted into the eye. It is directly excited by the circula- 
 tion of dyspnceic blood in the medulla. (The centre for contracting the pupil is 
 referred to at §§ 345 and 392.) 
 
 9. There is a subordinate centre in the medulla oblongata, which seems to be concerned in bring, 
 ing the various reflex centres of the cord into relation with each other. Owsjannikow found that, 
 on dividing the medulla 6 mm. above the calamus scriptorius (rabbit) the general reflex movements 
 of the body still occurred, and the anterior and posterior extremities participated in such general 
 movements. If, however, the section was made I mm. nearer the calamus, only local partial reflex 
 actions occurred (§ 360, III, 4) ; [thus, on stimulating the hind leg, the fore legs did not react — 
 the transference of the reflex was interfered with]. The centre reaches upward to slightly above 
 the lowest third of the oblongata. 
 
 Pathological. — The medulla oblongata is sometimes the seat of a typical disease, known as 
 bulbar paralysis, or glosso-pharyngo-labial paralysis (Duchenne, i860), in which there is a pro- 
 gressive invasion of the different nerve nuclei (centres), of the cranial nerves which arise within 
 the medulla, these centres being the motor portions of an important reflex apparatus. Usually the 
 disease begins with paralysis of the tongue, accompanied by fibrillar contractions, whereby speech, 
 formation of the food into a bolus, and swallowing are interfered with (§ 354). The secretion of 
 thick viscid saliva points to the impossibility of secreting a thin, watery facial saliva (§ 145, A), 
 owing to paralysis of this nerve nucleus. Swallowing may be impossible, owing to paralysis 
 of the pharynx and palate. This interferes with the formation of consonants [especially the 
 Unguals, /, t, s, r, by and by the labial explosives b, p,] (J 318, C); the speech becomes nasal, 
 while fluids and solid food often pass into the nose. Then follows paralysis of the branches 
 of the facial to the lips, and there is a characteristic expression of the mouth " as if it were 
 frozen." All the muscles of the face may be paralyzed; sometimes the laryngeal muscles are 
 paralyzed, leading to the loss of voice and the entrance of food into the windpipe. The heart 
 beats are often slowed, pointing to stimulation of the cardio-inhibitory fibres (arising from the acces- 
 sorius). Attacks of dyspnoea, like those following paralysis of the recurrent nerves (jj 313, II. I, 
 and \ 352, 5, b), and death may occur. Paralysis of the muscles of mastication, contraction of the 
 pupil, and paralysis of the abducens are rare. [This disease is always bilateral, and it is important 
 to note that it affects the nuclei of those muscles that guard the orifices of the mouth, including the 
 tongue, the posterior nares including the soft palate, and the rima glottidis with the vocal cords.] 
 
 368. THE RESPIRATORY CENTRE AND THE INNERVA- 
 TION OF THE RESPIRATORY APPARATUS.— The respiratory 
 centre lies in the medulla oblongata (Legallois), .behind the point of origin of 
 the vagi, on both sides of the posterior aspect of the apex of the calamus scrip- 
 torius, between the nuclei of the vagus and accessorius (jFlourens), and was named 
 by Flourens the vital point, or nceud vital. The centre is double, one for each 
 side, and it may be separated by means of a longitudinal incision (Longef), whereby 
 the respiratory movements continue symmetrically on both sides. Section of 
 Vagi. — If one vagus be divided, respiration on that side is slowed. If both vagi 
 be divided, the respirations become much slower and deeper, but the respiratory 
 movements are symmetrical on both sides. Stimulation of the central end of one 
 vagus, both being divided, causes an arrest of the respiration only on the same 
 side, the other side continues to breathe. The same result is obtained by stimula- 
 tion of the trigeminus on one side {Langendorff). When the centre is divided 
 transversely on one side, the respiratory movements on the same side cease 
 (Schiff). Most probably the dominating respiratory centre lies in the medulla 
 oblongata, and upon it depends the rhythm and symmetry of the respiratory 
 movements ; but, in addition, other and subordinate centres are placed in the 
 spinal cord, and these are governed by the oblongata centre. If the spinal cord 
 be divided in newly-born animals (dog, cat) below the medulla oblongata, respi- 
 ratory movements of the thorax are sometimes observed (Bracket (1835), Lauten- 
 bach, and Langendorff). 
 
 [If the cord be divided below the medulla, or the cranial arteries ligatured (rabbit), there may 
 still be respiratory movements, which become more distinct if strychnin be previously administered, 
 so that Langendorff assumes the existence of a spinal respiratory centre, which he finds is also in- 
 fluenced by reflex stimulation of sensory nerves.] 
 
CEREBRAL INSPIRATORY CENTRE. 
 
 687 
 
 Fig. 416. 
 
 Anatomical. — According to Giercke, Heidenhain, and Langendorff, those parts of the medulla, 
 oblongata whose destruction causes cessation of the respiratory movements are not gray cellular 
 substance, but only single or double strands of nervous matter running downward in the substance 
 of the medulla oblongata. These strands are said to arise partly from the roots of the vagus, 
 trigeminus, spinal accessory, and glosso-pharyngeal (Meynerl), forming connections by means of 
 fibres with the other side, and descending as far downward as the cervical enlargement of the spinal 
 cord (Goll). According to this view, this strand represents an inter-central band connecting the 
 spinal cord (the place of origin of the motor respiratory nerves) with the nuclei of the above-named 
 cranial nerves. 
 
 Cerebral Inspiratory Centre. — According to Christiani, there is a cerebral 
 inspiratory centre in the optic thalamus in the 
 floor of the 3d ventricle, which is stimulated 
 through the optic and auditory nerves, even 
 after extirpation of the cerebrum and corpora 
 striata; when it is stimulated directly, it 
 deepens and accelerates the inspiratory move- 
 ments, and may even cause a stand-still of the 
 respiration in the inspiratory phase. This 
 inspiratory dentre may be extirpated. After 
 this operation, an expiratory centre is active 
 in the substance of the anterior pair of the 
 corpora quadrigemina, not far from the aque- 
 duct of Sylvius. Lastly, Martin and Booker 
 describe a second cerebral inspiratory centre 
 in the posterior pair of the corpora quadri- 
 gemina. These three centres are connected 
 with the centres in the medulla oblongata. 
 
 Inspiratory and Expiratory Centres. 
 — The respiratory centre consists of two cen- 
 tres, which are in a state of activity alternately 
 — an inspiratory and an expiratory centre 
 (Fig. 416), each one forming the motor cen- 
 tral point for the acts of inspiration and ex- 
 piration (§11 2). The centre is automatic, 
 for, after section of all the sensory nerves 
 which can act reflexly upon the centre, it still 
 retains its activity. The degree of excita- 
 bility and the stimulation of the centre depend 
 upon the state of the blood, and chiefly 
 upon the amount of the- blood gases, the O 
 and C0 2 (_/. Rosenthal). 
 
 According to the condition of the centre, there are several well-recognized 
 respiratory conditions: — 
 
 1. Apncea. — Complete cessation of the respiration constituting apncea, i.e., 
 cessation of the respiratory movements, owing to the absence of the proper stimu- 
 lus, due to the blood being saturated with O and poor in C0 2 . Such blood satu- 
 rated with O fails to stimulate the centre, and hence the respiratory muscles are 
 quiescent. This seems to be the condition in the foetus during intra-uterine life. 
 If air be vigorously and rapidly forced into the lungs of an animal by artificial 
 respiration, the animal will cease to breathe for a time after cessation of the arti- 
 ficial respiration {Hook, i66f), the blood being so arterialized that it no longer 
 stimulates the respiratory centre. If a person takes a series of rapid, deep respi- 
 rations, his blood becomes surcharged with oxygen, and long " apnceic pauses " 
 occur. 
 
 Apnoeic Blood. — A. Ewald found that the arterial blood of apnoeic animals was completely 
 saturated with O, while the C0 2 was diminished; the venous blood contained less O than normal 
 — this latter condition being due to the apnoeic blood causing a considerable fall of the blood pressure 
 
 Scheme of the chief respiratory nerves (Ruther- 
 ford), ins, inspiratory, and e xp, expiratory 
 centre — motor nerves are in smooth lines. 
 Expiratory motor nerves to abdominal mus- 
 cles, ab ; to muscles of back, do._ Inspiratory 
 motor nerves, ph. phrenic to diaphragm, d; 
 int. intercostal nerves : ri. recurrent laryn- 
 geal : ex. pulmonary fibres of vagus that ex- 
 cite inspiratory centre ; ex* , pulmonary fibres 
 that excite expiratory centre ; ex", fibres of 
 sup. laryngeal that excite expiratory centre ; 
 ink, fibres of sup. laryngeal that inhibit the 
 inspiratory centre. 
 
688 ASPHYXIA. 
 
 • and consequent slowing of the blood stream, so that the O can be more completely taken from the 
 blood in the capillaries (Pfluger). The amount of O used in apncea, on the whole, is not increased 
 (§ 127). Gad remarks that during forced artificial respiration, the pulmonary alveoli contain a 
 very large amount of atmospheric air ; hence they are able to arterialize the blood for a longer time, 
 thus diminishing the necessity for respiration. 
 
 [Drugs. — If the excitability of the respiratory centre be diminished by chloral, apncea is readily 
 induced, while, if the centre be excited, as by apomorphine, it is difficult to produce it.] 
 
 2. Eupnoea. — The normal stimulation of the respiratory centre, eupncea, is 
 caused by the blood in which the amount of O and C0 2 does not exceed the 
 normal limits (§§ 35 and 36). 
 
 3. Dyspnoea. — All conditions which diminish the O and increase the C0 2 in 
 the blood circulating through the medulla and respiratory centre cause accelera- 
 tion and deepening of the respirations, which may ultimately pass into vigorous 
 and labored activity of all the respiratory muscles, constituting dyspnoea, when the 
 difficulty of breathing is very great (§ 134). [Changes in .the rhythm, § in.] 
 
 4. Asphyxia. — If blood, abnormal as regards the amount and quality of its 
 gases, continues to circulate in the medulla, or if the condition of the blood be- 
 come still more abnormal, the respiratory centre is over-stimulated, and ultimately 
 exhausted. The respirations are diminished both in number and depth, and they 
 become feeble and gasping in character ; ultimately the movements of the respi- 
 ratory muscles cease, and the heart itself soon ceases to beat. This constitutes the 
 condition of asphyxia, and if it be continued death from suffocation takes place. 
 (Langendorff asserts that in asphyxiated frogs the muscles and gray nervous sub- 
 stance have an acid reaction.) If the conditions causing the abnormal condition 
 of the blood be removed, the asphyxia may be prevented under favorable circum- 
 stances, especially by using artificial respiration (§ 134) ; the respiratory mus- 
 cles begin to act and the heart begins to beat, so that the normal eupnceic stage 
 is reached through the condition of dyspnoea. If the venous condition of the 
 blood be produced slowly and very gradually, asphyxia may take place without 
 there being any symptoms of dyspnoea, as occurs when death takes place quietly 
 and very gradually (§ 324, 5). 
 
 Causes of Dyspncea. — (1) Direct limitation of the activity of the respiratory organs; 
 diminution of the respiratory surface by inflammation, acute oedema ($ 47), or collapse of the 
 alveoli, occlusion of the capillaries of the alveoli, compression of the lungs, entrance of air into 
 the pleura, obstruction or compression of the windpipe. (2) Obstruction to the entrance of the 
 normal amount of air by strangulation, or enclosure in an insufficient space. (3) Enfeeblement of 
 the circulation, so that the medulla oblongata does not receive a sufficient amount of blood ; in 
 degeneration of the heart, valvular cardiac disease, and artificially by ligature of the carotid and 
 vertebral arteries [Kussmaul and Tenner), or by preventing the free efflux of venous blood from 
 the skull, or by the injection of a large quantity of air or indifferent particles into the right heart. 
 (4) Direct loss of blood, which acts by arresting the exchange of gases in the medulla (J. Rosen- 
 thal). This is the cause of the " biting or snapping at the air " manifested by the decapitated 
 heads of young animals, e.g., kittens. [The phenomenon is well marked in the head of a tortoise 
 separated from the body ( W. Stirling)."] All these factors act rapidly upon the respiratory activity, 
 and at first the respirations are deeper and more rapid, and afterward the respiratory movements 
 become more violent and general convulsions occur, ending with expiratory spasm, which is fol- 
 lowed by a stage of cessation of the respiration and complete relaxation. Before death takes 
 place there are usually a few "snapping " or gasping efforts at inspiration (Hogyes, Sigm. Mayer — 
 Jill). 
 
 Condition of the Blood Gases. — As a general rule, in the production of dyspncea the want of 
 O and the excess of C0 2 act simultaneously (Pfluger and Dohmen), but each of these alone may 
 act as an efficient cause. According to Bernstein, blood containing a small amount of O acts 
 chiefly upon the inspiratory centre, and blood rich in C0 2 on the expiratory centre. Dyspncea, 
 from want of O, occurs during respiration in a space of moderate size (| 133), in spaces where the 
 tension of the air is diminished, and by breathing in indifferent gases or those containing no free 0. 
 When the blood is freely ventilated with N or H, the amount of C0 2 in the blood may even be 
 diminished, and death occurs with all the signs of asphyxia (Pfluger). Dyspnoea, from the blood 
 being overcharged with C0 2 , occurs by breathing air conta'ning much C0 2 ($ 133). Air contain- 
 ing much C0 2 may cause dyspncea, even when the amount of O in the blood is greater than that 
 in the atmosphere ( Thiry). The blood may even contain more O than normal (Pfluger). 
 
 Heat Dyspnoea. — An increased temperature increases the activity of the respiratory centre 
 
CONDITIONS ACTING ON THE RESPIRATORY CENTRE. 689 
 
 (J 214, II, 3). This occurs when blood warmer than natural flows through the brain, as Fick and 
 Goldstein observed when they placed the exposed carotids in warm tubes, so as to heat the blood 
 passing through them. In this case the heated blood acts directly upon the brain, the medulla and 
 the cerebral respiratory centres {Gad). Direct cooling diminishes the excitability (Frediricq). 
 When the temperature is increased, vigorous artificial respiration does not produce apncea, although 
 the blood is highly arterialized (Ackermann). Emetics act in a similar manner (Nermann and 
 Grimm). 
 
 Electrical stimulation of the medulla oblongata separated from the brain discharges respiratory 
 movements (Kronecker and Marckwald), or increases those already present. Langendorff found 
 that electrical, mechanical or chemical (salts) stimulation usually caused an expiratory effect, while 
 stimulation of the cervical spinal cord (subordinate centre) gave an inspiratory effect. According 
 to Laborde, a superficial lesion in the region of the calamus scriptorius causes stand- still of the 
 respiration for a few minutes. If the peripheral end of the vagus be stimulated so as to arrest the 
 action of the heart, the respirations also cease after a few seconds. Arrest of the heart's action 
 causes a temporary ana;mia of the medulla, in consequence of which its excitability is lowered, so 
 that the respirations cease for a time (Langendorff ). 
 
 Action on the Centre. — The respiratory centre, besides being capable of 
 being stimulated directly, may be influenced by the will, and also reflexly by 
 stimulation of a number of afferent nerves. 
 
 1. By a voluntary impulse we may arrest the respiration for a short time, 
 but only until the blood oecomes so venous as to excite the centre to increased 
 action. The number and depth of the respirations may be voluntarily increased 
 for a long time, and we may also voluntarily change the rhythm of respiration. 
 
 2. The respiratory centre may be influenced reflexly both by fibres which 
 excite it to increased action and by others which inhibit its action, (a) The 
 exciting fibres lie in the pulmonary branches of the vagus, in the optic, audi- 
 tory and sensory cutaneous nerves, and normally their action overcomes the 
 action of the inhibitory fibres. Thus a cold bath deepens the respirations, and 
 causes a moderate acceleration of the pulmonary ventilation (Speck). 
 
 Section of both vagi causes slower and deeper respiratory movements, 
 owing to the cutting off of those impulses which under normal conditions pass 
 from the lungs to excite the respiratory centre. The amount of air taken in 
 and C0 2 given off, however, is unchanged. The inspiratory efforts are more 
 vigorous and not so purposive (Gad). Weak tetanizing currents applied to the 
 central end of the vagus cause acceleration of the respirations (Budge, Eckhard), 
 while at the same time the efforts of the respiratory muscles may be increased or 
 diminished or remain unchanged (Gad). Strong tetanizing currents cause stand- 
 still of the respiration in the inspiratory phase (Traube) or expiratory phase 
 (Budge, Burkart). Single induction shocks have no effect (Marckwald and Kro- 
 necker). 
 
 Wedenski and Heidenhain have recently reinvestigated the effect of stimulation of the vagus 
 upon the respiration. They find that a temporary weak electrical stimulus applied to the central 
 end of the vagus, at the beginning of inspiration (rabbit), affects the depth of the succeeding 
 inspirations, while a similar strong stimulus affects also the depth of the following expirations. If 
 the stimulus be applied just at the commencement of expiration, stronger stimuli being required in 
 this case, there is a diminution of the expiration and of the following inspiration. Continued tetanic 
 stimulation of the vagus may cause decrease in the depth of the expirations, or at the same time 
 alteration in the depth of the inspirations, without affecting the respiratory rhythm ; when the stimu- 
 lation is stronger, inspiration and expiration are diminished with or without alteration of the fre- 
 quency, and with the strongest stimuli respirations cease either in the inspiratory or expiratory 
 phase. 
 
 (b) The inhibitory nerves which affect the respiratory centre lie in the superior 
 laryngeal nerve (Rosenthal), and also in the inferior (Pfluger and Burkart, Her- 
 ing, Breuer) (Fig. 416, inh). 
 
 According to Langendorff, direct electrical, mechanical, or chemical stimulation of the centre may 
 arrest respiration, perhaps in consequence of the stimulus affecting the central ends of these inhibi- 
 tory nerves where they enter the ganglia of the respiratory centre. 
 
 Stimulation of the superior or inferior laryngeal nerves (b) or their central ends 
 causes slowing, and even arrest of the respiration (in expiration — Rosenthal). 
 44 
 
690 METHODS OF PERFORMING ARTIFICIAL RESPIRATION. 
 
 Arrest of the respiration in expiration is also caused by stimulation of the nasal 
 {Hering and Kratschmer) and ophthalmic branches of the trigeminus {Christiani) ; 
 stimulation of the pulmonary branches of the vagus by breathing irritating gases 
 {Knoll), although other gases cause stand-still in inspiration. Chemical stimula- 
 tion of the trunk of the vagus — by dilute solutions of sodic carbonate — causes 
 expiratory inhibition of the respiration ; and mechanical stimulation — rubbing 
 with a glass rod — inspiratory inhibition {Knoll). The stimulation of sensory 
 cutaneous nerves, especially of the chest and abdomen, as occurs on taking a cold 
 douche, and stimulation of the splanchnics, cause stand-still in expiration {Schiff, 
 Falk), the first cause often giving rise to temporary clonic contractions of the re- 
 spiratory muscles. The respirations are often slowed to a very great extent by 
 pressure upon the brain [whether the pressure be due to a depressed fracture or 
 effusion into the ventricles and subarachnoid space]. The respiration may be 
 greatly oppressed and stertorous. 
 
 The amount of work done by the respiratory muscles is altered during the reflex slowing of the 
 respiratory muscles, the work being increased during slow respiration, owing to the ineffectual in- 
 spiratory efforts (Gad). The volume of the gases which passes through the lungs during a given 
 time remains unchanged ( Valentin), and the gaseous exchanges are not altered at first ( Voit and 
 Rauber). 
 
 Automatic Regulation of the Respiratory Centre. — Under normal cir- 
 cumstances, it would seem that the pulmonary branches of the vagus act upon the 
 two respiratory centres, so as to set in action what has been termed the self-adjust-, 
 ing mechanism ; thus, the inspiratory dilatation of the lungs stimulates mechani- 
 cally the fibres which reflexly excite the expiratory centres, while the diminution 
 of the lungs during expiration excites the nerves which proceed to the inspiratory 
 centre {Hering and Breuer). 
 
 Discharge of the First Respiration. — The foetus is in an apnceic condition 
 until birth, when the umbilical cord is cut. During intra-uterine life O is freely 
 supplied to it by the activity of the placenta. All conditions which interfere with 
 this due supply of O, as compression of the umbilical vessels and prolonged labor 
 pains, cause a decrease of the O and an increase of the C0 2 in the blood, so that the 
 condition of the foetal blood is so altered as to stimulate the respiratory centre, 
 and thus the impulse is given for the discharge of the first respiratory movement 
 {Schwartz). A foetus still within the unopened foetal membranes may make re- 
 spiratory movements {Vesalius, 1542). If the exchange of gases be interrupted 
 to a sufficient extent, dyspnoea and ultimately death of the foetus may occur. If, 
 however, the venous condition of the mother's blood develops very slowly, as in 
 cases of quiet, slow death of the mother, the medulla oblongata of the foetus may 
 gradually die without any respiratory movement being discharged (§ 324, 5). 
 
 According to this view, the respiratory movements are due to the direct action of the dyspnoeic 
 blood upon the medulla oblongata. Death of the mother acts like compression of the umbilical 
 . cord. In the former case, the maternal venous blood robs the foetal blood of its O, so that death of 
 the foetus occurs more rapidly (Zuntz). If the mother be rapidly poisoned with CO (§ 17), the foetus 
 may live longer, as the CO-hsemoglobin of the maternal blood cannot take any O from the foetal 
 blood (g 16—Hogyes). In slow poisoning, the CO passes into the foetal blood (Grehant and Quin- 
 quand). 
 
 In many cases, especially in cases of very prolonged labor, the excitability of the respiratory centre 
 may be so diminished, that after birth the dyspnoeic condition of the blood alone is not sufficient to 
 excite respiration in a normal rhythmical manner. In such cases stimulation of the skin also acts, 
 t. g., partly by the cooling produced by the evaporation of the amniotic fluid from the skin. When 
 air has entered the lungs by the first respiratory movements, the air within the lungs also excites the 
 pulmonary branches of the vagus (Pflu^er), and thus the respiratory centre is stimulated reflexly to 
 increased activity. According to v. Preuschen's observations, stimulation of the cutaneous nerves • 
 is more effective than that of the pulmonary branches of the vagus. In animals which have been 
 rendered apnoeic by free ventilation of their lungs, respiratory movements maybe discharged by 
 strong cutaneous stimuli, c . g., dashing on of cold water. The mechanical stimulation of the skin 
 by friction or sharp blows, or the application of a cold douche, excites the respiratory centre (Arti- 
 ficial Respiration, \ 134). 
 
DIRECT STIMULATION OF THE CARDIO-INHIBITORY CENTRE. 691 
 
 [Action of Drugs on the Respiratory Centre. — Ammonia, salts of zinc and copper, strychnin, 
 atropin, duboisin, apomorphin, emetin, the digitalis group, and heat increase the rapidity and depth 
 of the respirations, while they become frequent and shallower after the use of alcohol, opium, 
 chloral, chloroform, physostigmin. The excitability of the centre is first increased and then di- 
 minished by caffein, nicotin, quinine, and saponin (Brunton).] 
 
 '369. THE CENTRE FOR THE INHIBITORY NERVES OF 
 THE HEART— (CARDIO-INHIBITORY).— The fibres of the vagus 
 which when moderately stimulated diminish the action of the heart, when strongly 
 stimulated, however, arrest its action and cause it to stand still in diastole (§352,7), 
 are supplied to the vagus through the spinal accessory nerve (§ 353), and have 
 their centre in the medulla oblongata. 
 
 [Gaskell has shown that stimulation of the vagus not only influences the rhythm 
 of the heart's action, but it modifies the other functions of the cardiac muscle. 
 Stimulation of the vagus influences — (a) the automatic rhyth?n, i. e., the rate 
 at which the heart contracts automatically ; (J>) the force of the contractions, more 
 especially the auricles, although in some animals, e. g., the tortoise, the ventricles 
 are not affected ; (c) the power of conduction, i. <?., the capacity for conducting 
 the muscular contractions. According to Gaskell, the vagus acts upon the rhyth- 
 mical power of the muscular fibres of the heart.] 
 
 This centre may be excited directly in the medulla, and also reflexly, by 
 stimulating certain afferent nerves. 
 
 Many observers assume that this centre is in a state of tonic excitement, i. <?., that there is a 
 continuous, uninterrupted, regulating and inhibitory action of this centre upon the heart through the 
 fibres of the vagus. According to Bernstein, this tonic excitement is caused reflexly through the 
 abdominal and cervical sympathetic. 
 
 I. Direct Stimulation of the Centre. — This centre may be stimulated 
 directly by the same stimuli that act upon the respiratory centre. (1) Sudden 
 anamia of the oblongata, by ligature of both carotids, both subclavians, or decapi- 
 tating a rabbit, the vagi alone being left undivided, causes slowing and even 
 temporary arrest of the action of the heart. (2) Sudden venous hyperemia acts in 
 a similar manner, and it can be produced by ligaturing all the veins returning 
 from the head {Landois, Hermann and Escher). (3) The increased venosity of 
 the blood, produced either by direct cessation of the respirations (rabbit) or by 
 forcing into the lungs a quantity of air containing much CO z {Traube). As the 
 circulation in the placenta (the respiratory organ of the foetus) is interfered 
 with during severe labor, this sufficiently explains the constant enfeeblement of 
 the action of the heart during protracted labor ; it is due to stimulation of the 
 central end of the vagus by the dyspnceic blood {B. S. Schultze). (4) At the 
 moment the respiratory centre is excited, and an inspiration occurs, there is a 
 variation in the inhibitory activity of the cardiac centre {Bonders, Pftiiger, Eri- 
 dericq — § 74, a, 4). (5) The centre is excited by increased blood pressure within 
 the cerebral arteries. 
 
 II. The cardio-inhibitory centre may be excited reflexly — (1) By stimulation 
 of sensory nerves (Zoven, Kratschmer). (2) By stimulation of the central end of 
 one vagus, provided the other vagus is intact (v. Bezold, Donders, Aubert and 
 Roever). (3) By stimulation of the sensory nerves of the intestines by tapping 
 upon the belly (Goltz's tapping experiment), whereby the action of the heart 
 is arrested. Stimulation of the splanchnic directly {Asp and Ludwig), or of the 
 abdominal or cervical sympathetic {Bernstein), produces the same result. Very 
 strong stimulation of sensory nerves, however, arrests the above-named reflex 
 effects upon the vagus (§ 361, 3). 
 
 Tapping Experiment. — Goltz's experiment succeeds at once by tapping the intestines of a frog 
 directly, say with the handle of a scalpel, especially if the intestine has been exposed to the air for 
 a short time, so as to become inflamed ( Tarchanoff). Stimulation of the stomach of the dog causes 
 slowing of the heart beat (Si?. Mayer and Pribram). [M'William finds that the action of the 
 heart of the eel may be arrested reflexly with very great facility. The reflex inhibition is obtained 
 
692 STIMULATION OF THE TRUNK OF THE VAGUS. 
 
 by slight stimulation of the gills (through the branchial nerves), the skin of the head and tail and 
 parietal peritoneum, by severe injury of almost any part of the animal except the abdominal 
 organs.] 
 
 [Effect of Swallowing Fluids. — Kronecker has shown that the act of swallowing interferes 
 with or abolishes temporarily the cardio-inhibitory action of the vagus, so that the pulse rate is 
 greatly accelerated. Merely sipping a wineglassful of water may raise the rate 30 per cent. Hence, 
 sipping cold water acts as a powerful cardiac stimulant.] 
 
 According to Hering, the excitability of the cardio-inhibitory centre is diminished by vigorous 
 artificial ventilation of the lungs with atmospheric air. At the same time there is a considerable 
 fall of the blood pressure (g 353, 8, 4). In man, a vigorous expiration, owing to the increased 
 intra-pulmonary pressure, causes an acceleration of the heart beat, which Sommerbrodt ascribes to 
 a diminution of the activity of the vagi. At the same time the activity of the vasomotor centre is 
 diminished (£ 60, 2). 
 
 Stimulation of the trunk of the vagus from the centre downward, along 
 its whole course, and also of certain of its cardiac branches [inferior cardiac], 
 causes the heart either to beat more slowly or arrests its action in diastole. The 
 result depends upon the strength of the stimulus employed ; feeble stimuli slow 
 the action of the heart, while strong stimuli arrest it in diastole. The frog's heart 
 may be arrested by stimulating the fibres of the vagus upon the sinus venosus. 
 If strong stimuli be applied either to the centre or to the course of the nerve for a 
 long time, the part stimulated becomes fatigued, and the heart beats more rapidly 
 in spite of the continued stimulation. If a part of the nerve lying nearer the 
 heart be stimulated, inhibition of the heart's action is brought about, as the 
 stimulus acts upon a fresh portion of nerve. 
 
 The following points have also been ascertained regarding the stimulation of the inhibitory 
 fibres : — 
 
 1 . The experiments of Lowit on the frog's heart, confirmed by Heidenhain, showed that electrical 
 and chemical stimulation of the vagus produces different results as regards the extent of the ven- 
 tricular systole, as well as the number of heart beats ; the contractions either become smaller or 
 less frequent, or they become smaller and less frequent simultaneously. Strong stimuli cause, in 
 addition, well-marked relaxation of heart muscle during diastole. 
 
 2. In order to cause inhibition of the heart, a continuous stimulus is not necessary. 
 
 3. Donders, with Prahl and Niiel, observed that arrest of the heart's action did not take place 
 immediately the stimulus was applied to the vagus, but about \ of a second— period of latent 
 stimulation — elapsed before the effect was produced on the heart. 
 
 A rhythmically-interrupted moderate stimulus suffices [v. Bezold) ; 18 to 20 stimuli per second 
 are required for mammals, and 2 to 3 per second for cold-blooded animals. If the heart be arrested 
 by stimulation of the vagus, it can still contract, if it be excited directly, e. g., by pricking it with 
 a needle, when it executes a. single contraction. [This holds good only for some animals, e.g.,hog, 
 tortoise, birds and mammals. In fishes only the ventricle responds to stimulation during marked 
 inhibition ; in the newt only the bulbus arteriosus. In the newt's heart the sinus, auricles and ven- 
 tricle are all inexcitable to direct stimulation during strong inhibition.] 
 
 5. According to A. B. Meyer, inhibitory fibres are present only in the right vagus in the turtle. 
 It is usually stated that the right vagus is more effective than the left in other animals, e. g., rabbit, 
 [Masoin, Arloing and Tripier) ; but this is subject to many exceptions (Zandois and Langen- 
 dorff). [In the newt the right vagus acts more readily on the ventricle than on the other parts of 
 the heart ; slight stimulation of the right vagus can arrest the ventricle, while the sinus and auricles 
 go on beating.] 
 
 6. The vagus has been compressed by the finger in neck of man (Czermak, Concato); but this 
 experiment is accompanied by danger, and ought not to be undertaken. The electrotonic condition 
 of the vagus is stated in \ 335, III. 
 
 7. Schirf found that stimulation of the vagus of the frog caused acceleration of the heart beat 
 when he displaced the blood of the heart with saline solution. If blood serum be supplied to the 
 heart the vagus regains its inhibitory action. 
 
 8. Many soda salts in a proper concentration arrest the inhibitory action of the vagus, while pot- 
 ash salts restore the inhibitory function of the vagi suspended by the soda salts. If, however, the 
 soda or potash salts act too long upon the heart, they produce a condition in which, after the inhibi- 
 tory function of the vagi is abolished, 1t is not again restored. The heart's action in this condition 
 is usually arhythmical (Lowit). 
 
 9. If the intracardial pressure be greatly increased, so as to accelerate greatly the cardiac 
 pulsations, the activity of the vagus is correspondingly diminished (J. M. Zudwig and Zuchsin- 
 ger). 
 
 [Differences in Animals. — Perhaps the most remarkable fact in the influence of the vagus on 
 the eel's heart and that of all other fishes examined is that vagus stimulation causes the sinus and 
 
THE NERVUS ACCELERANS. 
 
 693 
 
 auricle to be entirely inexcitable to direct stimulation during strong inhibition. Nerve stimulation 
 has, in this case, the very peculiar effect of rendering the muscular tissue temporarily incapable of 
 responding to even the strongest direct stimuli, e.g.. powerful induction shocks. This would appear 
 to be decisive evidence that the vagus acts on muscle directly, and not simply on automatic motor 
 ganglia, as was held according to the old view. 
 
 Poisons. — Muscarin stimulates the terminations of the vagus in the heart, and causes the heart 
 to stand still in diastole {Schmiedeberg and Koppe). If alropin be applied in solution to the heart 
 this action is set aside, and the heart begins to beat again. Digitalin diminishes the number of heart 
 beats by stimulating the cardio-inhibitory centre (vagus) in the medulla. Large doses diminish the 
 excitability of the vagus centre, and increase at the same time the accelerating cardiac ganglia, so 
 that the heart beats are thereby increased. In small doses, digitalin raises the blood pressure by 
 stimulating the vasomotor centre and the elements Of the vascular wall (Klug). Nicotin first excites 
 the vagus, then rapidly paralyzes it. Hydrocyanic acid 'has the same effect {Preyer). Atropin(v. 
 Betold ) and curara (large dose — CI. Bernard and Kolliker) paralyze the vagi, and so does a very 
 low temperature or high fever. 
 
 370. THE CENTRE FOR THE ACCELERATING CARDIAC 
 NERVES AND THE ACCELERATING FIBRES.— Nervus Ac- 
 
 celerans. — It is more than probable that a centre exists in the medulla oblongata 
 
 which sends accelerating fibres to the heart. These fibres pass from the medulla 
 
 oblongata — but from which part thereof has not been exactly ascertained — through 
 
 the spinal cord, and leave the cord through the rami coinmunicantes of the lower 
 
 cervical and upper six dorsal nerves {Strieker), to pass into the sympathetic nerve. 
 
 Some of these fibres, issuing from the spinal cord, pass through the first thoracic 
 
 sympathetic ganglion and the ring of Vieussens, to join the cardiac plexus (Figs. 
 
 417, 418). [These fibres, issuing from the spinal cord, 
 
 frequently accompany the nerve running along the f ig . 417. 
 
 vertebral artery], and they constitute the Nervus ac- 
 
 celerans cordis. [Fig. 418 shows the accelerator fibres 
 
 passing through the ganglion stellatum of the cat to 
 
 join the cardiac plexus.] If the vagi of an animal be 
 
 divided, stimulation of the medulla oblongata, of the 
 
 lower end of the divided ceivical spinal cord, even 
 
 the lower cervical ganglion, or of the upper dorsal 
 
 ganglion of the sympathetic {Gang, stellatum), causes 
 
 acceleration of the heart beats in the dog and rabbit 
 
 without the blood pressure undergoing any change 
 
 {CI'. Bernard, v. Bezold, Cyori). 
 
 On stimulating the medulla oblongata or the cervical portion 
 of the spinal cord, the vasomotor nerves are, of course, simultane- 
 ously excited. The consequence is that the blood vessels, sup- 
 plied by vasomotor nerves from the spot which is stimulated, con- 
 tract, and the blood pressure is greatly increased. Again, a sim- 
 ple increase of the blood pressure accelerates the action of the 
 heart; this experiment does not prove directly the existence of 
 accelerating fibres lying in the upper part ot the spinal cord. If, 
 however, the splanchnic nerves be divided beforehand, and, as 
 they supply the largest vasomotor area in the body, the result of 
 their division is to cause a great fall of the blood pressure, then 
 on stimulating the above-named parts, after this operation, the 
 heart beats are still increased in number, so that its increase can- 
 not be due to the increased blood pressure. Indirectly it may 
 be shown, by dividing or extirpating all the nerves of the cardiac 
 plexus, or at least all the nerves going to the heart, that stimula- 
 tion of the medulla oblongata, or cervical part of the spinal cord, 
 no longer causes an increased frequency of the heart's action to 
 the same extent as before division of these nerves. The slightly 
 increased frequency in this case is due to the increased blood 
 pressure. 
 
 The accelerating centre is certainly not continually 
 in a state of tonic excitement, as section of the accelerans nerve does not cause 
 
 Scheme of tbe course of the accele- 
 rans fibres. P.pons; MO, medulla 
 oblongata ; C, spinal cord ; V, in- 
 hibitory centre for heart ; A, accele- 
 rans centre; Vac, vagus; SL, su- 
 perior, IL, inferior laryngeal ; SC, 
 superior^ IC, inferior cardiac: H, 
 heart; C, cerebral impulse ; S, cer- 
 vical sympathetic : a, a, accelerans 
 fibres. 
 
694 THE CARDIAC PLEXUS. 
 
 slowing of the action of the heart ; the same is true of destruction of the medulla 
 oblongata or of the cervical spinal cord. In the latter case the splanchnic nerves 
 must be divided beforehand to avoid the slowing effect on the action of the heart 
 produced by the great fall of the blood pressure consequent upon destruction of 
 the cord, otherwise we might be apt to ascribe the result to the action of the ac- 
 celerating centre, when it is in reality due to the diminished blood pressure 
 {Brothers Cyon). 
 
 According to the results of the older observers (v. Bezold and others), some 
 accelerating fibres run in the cervical sympathetic. A few fibres pass through the 
 vagus to reach the heart (§ 352, 7), and when they are stimulated the heart beat 
 is accelerated and the cardiac contractions strengthened {Heidenhain and Lowit). 
 The inhibitory fibres of the vagus lose their excitability more readily than the 
 
 Fig. 418. 
 
 Cardiac plexus, and ganglion stellatum ot the cat. R, right, L, left X * % ', i , vagus ; 2', cervical sympathetic, and in 
 the annulus of Vieussens ; 2, communicating branches from the middle cervical ganglion and the ganglion stel- 
 latum ; 2", thoracic sympathetic; 3, recurrent laryngeal ; 4, depressor nerve ; 5, middle cervical ganglion ; 5', 
 communication between 5 and the vagus ; 6, ganglion stellatum (1st thoracic ganglion) ; 7, communicating 
 branches with the vagus ; 8, nervus accelerans ; 8,8', 8", roots of accelerans ; g, branch of the ganglion stellatum. 
 
 accelerating fibres, but the vagus fibres are more excitable than those of the 
 accelerans. 
 
 Modifying Conditions. — When the peripheral end of the nervus accelerans is stimulated, a 
 considerable time elapses before the effect upon the frequency of the heart takes place, i. e., it has 
 a long latent period. Further the acceleration thus produced disappears gradually. If the vagus 
 and accelerans fibres be stimulated simultaneously, only the inhibitory action of the vagus is 
 manifested. If, while the accelerans is being stimulated, the vagus be suddenly excited, there is a 
 prompt diminution in the number of the heart beats ; and if the stimulation of the vagus is stopped, 
 the accelerating effect of the accelerans is again rapidly manifested (C. Ludwig with Schmiedeberg, 
 Bowditch, Baxt). According to the experiments of Strieker and Wagner on dogs, with both vagi 
 divided, a diminution of the number of the heart beats occured when both accelerantes were 
 divided. This would indicate a tonic innervation of the latter nerves. 
 
POSITION OF THE VASOMOTOR CENTRE. 695 
 
 [Accelerans in the Frog. — Gaskell showed that stimulation of the vagus 
 might produce two opposing effects ; the one of the nature of inhibition, the other 
 of augmentation. In the crocodile, the accelerans fibres leave the sympathetic 
 chain at the large ganglion corresponding to the ganglion stellatum of the dog, 
 and run along the vertebral artery up to the superior vena cava, and after an anas- 
 tomosing with branches of the vagus, pass to the heart. "Stimulation of these 
 fibres increases the rate of the cardiac rhythm, and augments the force of auricular 
 contractions ; while stimulation of the vagus slows the rhythm, and diminishes 
 the strength of the auricular contractions." The strength of the ventricular con- 
 traction, both in the tortoise and crocodile, does not seem to be influenced by 
 stimulation of the vagus, and probably, also, it is unaffected by the sympathetic. 
 The so-called vagus of the frog in reality consists of pure vagus fibres and sym- 
 pathetic fibres, and is, in fact, a vago-sympathetic. Gaskell finds that stimulation 
 of the sympathetic, before it joins the combined ganglion of the sympathetic and 
 vagus, produces purely augmentor or accelerating effects ; while stimulation of the 
 vagus, before it enters the ganglion, produces purely inhibitory effects. The two 
 sets of fibres are quite distinct, so that in the frog the sympathetic is' a purely 
 augmentor (accelerator), and the vagus a purely inhibitory nerve. Acceleration 
 is merely one of the effects produced by stimulation of these nerves, so that Gas- 
 kell suggests that they ought to be called "augmentor," or simply cardiac 
 sympathetic nerves.] 
 
 [In his more recent researches Gaskell asserts that vagus stimulation produces first an inhibitory 
 or depressing effect, but that it ultimately improves the condition of the heart as regards force, rate 
 or regularity — one or all of these. He regards it as a true anabolic nerve (§ 342, d).] 
 
 371. VASOMOTOR CENTRE AND VASOMOTOR NERVES.— 
 Vasomotor Centre. — The chief dominating or general centre which sup- 
 plies all the non-striped muscles of the arterial system with motor nerves 
 (vasomotor, vaso-constrictor, vaso-hypertonic nerves) lies in the medulla oblon- 
 gata, at a point which contains many ganglionic cells {Ludwig and Thiry). Those 
 nerves which pass to the blood vessels are known as vasomotor nerves. The 
 centre (which is 3 millimetres long and i*4 millimetre broad in the rabbit), 
 reaches from the region of the upper part of the floor of the medulla oblongata 
 to within 4 to 5 mm. of the calamus scriptorius. Each half of the body has its 
 own centre placed 2*4 millimetres from the middle line on its own side, in that 
 part of the medulla oblongata which represents the upward continuation of the 
 lateral columns of the spinal cord ; according to Ludwig and Owsjannikow, and 
 Dittmar, in the lower part of the superior olives. Stimulation of this central 
 area causes contraction of all the arteries, and in consequence there is great in- 
 crease of the arterial blood pressure, resulting in swelling of the veins and heart. 
 Paralysis of this centre causes relaxation and dilatation of all the arteries, and 
 consequently there is an enormous fall of the blood pressure. Under ordinary 
 circumstances the vasomotor centre is in a condition of moderate tonic excitement 
 (§ 366). Just as in the case of the cardiac and respiratory centres the vasomotor 
 centre may be excited directly and reflexly. 
 
 [Position — How Ascertained. — As stimulation of the central end. of a sen- 
 sory nerve, e. g. , the sciatic, in an animal under the influence of curara, causes a 
 rise in the blood pressure, even after removal of the cerebrum, it is evident that 
 the centre is not in the cerebrum itself. By making a series of sections from above 
 downward, it is found that this reflex effect is not affected until a short distance 
 above the medulla oblongata is reached. If more and more of the medulla ob- 
 longata be removed from above downward, then the reflex rise of the blood pressure 
 becomes less and less, until, when the section is made 4 to 5 mm. above the calamus 
 scriptorius, the effect ceases altogether. This is taken to be the lower limit of the 
 general vasomotor centre. The bilateral centre corresponds to some large multi- 
 polar nerve cells, described by Clarke as the antero-lateral nucleus.] 
 
696 COURSE OF THE VASOMOTOR FIBRES. 
 
 I. Direct Stimulation of the Centre. — The amount and quality of the 
 gases contained in the blood flowing through the medulla are of primary import- 
 ance. In the condition of apncea (§ 368, 1) the centre seems to be very slightly 
 excited, as the blood pressure undergoes a considerable decrease. When the 
 mixture of blood gases is such as exists under normal circumstances, the centre is 
 in a state of moderate excitement, and running parallel with the respiratory move- 
 ments are variations in the excitement of the centre (Traube-Hering curves — § 85), 
 these variations being indicated by the rise of the blood pressure. When the 
 blood is highly venous, produced either by asphyxia or by the inspiration of air 
 containing a large amount of CO w the centre is strongly excited, so that all the 
 arteries of the body contract, while the venous system and the heart become dis- 
 tended with blood (Thiry). At the same time the velocity of the blood stream is 
 increased (Heidenhain). The same result is produced by sudden anremia of the 
 oblongata by ligature of both the carotid and subclavian arteries {Nawalichin, 
 Sigm. Mayer), and no doubt, also, by the sudden stagnation of the blood in venous 
 hypersemia. 
 
 Action of Poisons. — Strychnin stimulates the centre directly, even in curarized dogs, and so 
 do nicoiin and Calabar bean. 
 
 Emptiness of the Arteries after Death. — The venosity of the blood which occurs after death 
 always produces an energetic stimulation of the vasomotor centre, in consequence of which the 
 arteries are firmly contracted. The blood is thereby forced toward the capillaries and veins, and 
 fhu? is explained the "emptiness of the arteries after death." 
 
 Effect on Hemorrhage. — Blood flows much more freely from large wounds when the vaso- 
 motor centre is intact than if it be destroyed (frog). As psychical excitement undoubtedly influences 
 the vasomotor centre, we may thus explain the influence of psychical excitement (speaking, etc.) 
 upon the cessation of hemorrhage. If the hemorrhage be severe, stimulation of the medulla oblon- 
 gata, due to the anaemia, may ultimately cause constriction of the small arteries, and thus arrest the 
 bleeding. Thus, surgeons are acquainted with the fact that dangerous hemorrhage is often arrested 
 as soon as unconsciousness, due to cerebral anaemia, occurs. If the heart be ligatured in a frog, all 
 the blood is ultimately forced into the veins, and this result is also due to the anaemic stimulation of 
 the oblongata ( Goltz). In mammals, when the heart is ligatured, the equilibration of the blood 
 pressure between the arterial and venous systems takes place more slowly when the medulla oblon- 
 gata is destroyed than when it is intact (v. Bezold, Gsckeidlen). 
 
 [Effect of Destruction of the Vasomotor Centre. — If two frogs be pithed and their hearts 
 exposed, and both be suspended, then the hearts of both will be found to beat rhythmically and fill 
 with blood. Destroy the medulla oblongata and spinal cord of one of them, then immediately in 
 this case the heart, although continuing to beat with an altered rhythm, ceases to be filled with 
 blood ; it appears collapsed, pale, and bloodless. There is a great accumulation of the blood in the 
 abdominal organs and veins, and it is not returned to the heart, so that the arteries are empty. This 
 experiment of Goltz is held to show the existence of venous tonus depending on a cerebro-spinal 
 centre. If a limb of this frog be amputated, there is little or no hemorrhage, while in the other frog 
 the hemorrhage is severe. The bearing of this experiment on conditions of " shock " is evident.] 
 
 Direct Electrical Stimulation. — On stimulating the centre directly in animals, it is found that 
 single induction shocks only become effective when they succeed each other at the rate of 2 to 3 
 shocks per second. Thus there is a "summation" of the single shocks. The maximum contrac- 
 tion of the arteries, as expressed by the maximum blood pressure, is reached when 10-12 strong, ox 
 20-25 moderately strong shocks per second are applied [JCronecker and Nicolaides). 
 
 Course of the Vasomotor Nerves. — From the vasomotor centre some fibres proceed directly 
 through some of the cranial nerves to their area of distribution ; through the trigeminus partly to the 
 interior of the eye (fi 347, 1, 2), through the lingual and hypoglossal to the tongue ($ 347, III, 4), 
 through the vagus to a limited extent to the lungs (g 352, 8, 2), and to the intestines (| 352, 11 ). 
 All the other vasomotor nerves descend in the lateral columns of the spinal cord (\ 364, 9); hence 
 stimulation of the lower cut end of the spinal cord causes contraction of the blood vessels supplied 
 by the nerves below the point of section (Pfluger). In their course through the cord these fibres 
 form connections with the subordinate vasomotor centres in the gray matter of the cord ($ 362, 7), 
 and then leave the cord either directly through the anterior roots of the spinal nerves to their areas 
 of distribution, or they pass through the rami communicantes into the sympathetic, and from them 
 reach the blood vessels to which they are distributed ($ 356). 
 
 Cephalic Vasomotors. — The following is the arrangement of these nerves in the region of the 
 head : The cervical portion of the sympathetic supplies the great majority of the blood vessels of 
 the head (see Sympathetic, \ 356, A, 3 — CI. Bernard). In some animals the great auricular nerve 
 supplies a few vasomotor fibres to its own area of distribution (Schiff, Love'n, Moreau). The vaso- 
 motor nerves to the upper extremities pass through the anterior roots of the middle dorsal nerves 
 
REFLEX STIMULATION OF THE VASOMOTOR CENTRE. 697 
 
 into the thoracic sympathetic, and upward to the 1st thoracic ganglion, and from thence through the 
 rami communicantes to the brachial plexus (Schiff, Cyon). The skin of the trunk receives its 
 vasomotor nerves through the dorsal and lumbar nerves. The vasomotor nerves to the lower ex- 
 tremities pass through the nerves of the lumbar and sacral plexuses into the sympathetic, and 
 from thence to the lower limbs (Pftuger, Schiff, CI. Bernard). The lungs, in addition to a few 
 fibres through the vagus, are supplied from the cervical spinal cord through the 1st thoracic gan- 
 glion {Brown- ittquard, Fick and Badoud, Lichtheim). The splanchnic is the greatest vasomotor 
 nerve in the body, and supplies the abdominal viscera {\ 356, B — Bezo/d, Ludwig and Cyon). 
 The vasomotor nerves of the liver (g 173, 6), kidney (g 276), and spleen (§ 103) have been 
 referred to already. According to Strieker, most of the vasomotor nerves leave the spinal cord 
 between the 5th cervical and the 1st dorsal vertebrae. [Gaskell finds that in the dog they begin to 
 leave the cord at the 2d dorsal nerve (g 366).] 
 
 As a general rule, the blood vessels of the trunk and extremities are innervated from those nerves 
 which give other fibres [e.g., sensory) to those regions. The different vascular areas behave differ- 
 ently with regard to the intensity of the action of the vasomotor nerves. The most powerful vaso- 
 motor nerves are those that act upon the blood vessels of peripheral parts, e.g., the toes, the fingers 
 and ears ; while those that act upon central parts seem to be less active {Lewaschew), e.g., on the 
 pulmonic circulation ({! 88). 
 
 II. Reflex Stimulation of the Centre. — There are fibres contained in the 
 different afferent nerves whose stimulation affects the vasomotor centre. There 
 are nerve fibres whose stimulation excites the vasomotor centre, thus causing a 
 stronger contraction of the arteries, and consequently an increase of the arterial 
 blood pressure. These are called "pressor" fibres. Conversely, there are 
 other fibres whose stimulation refiexly diminishes the excitability of the vasomotor 
 centre. These act as reflex inhibitory nerves on the centre, and are known as 
 " depressor" nerves. 
 
 Pressor, or excito-vasomotor nerves, have already been referred to in connec- 
 tion with the superior and inferior laryngeal nerves (§ 352, 12, a) ; in the trigem- 
 inus, which, when stimulated directly (§ 347), causes a pressor action, as well 
 as when stimulating vapors are blown into the nostrils (Hering and Kratschmer). 
 [The rise of the blood pressure in this case, however, is accompanied by a change 
 in the character of the heart's beat and in the respirations. Rutherford has 
 shown that in the rabbit the vapor of chloroform, ether, amylic nitrite, acetic 
 acid or ammonia held before the nose of a rabbit greatly retards or even arrests 
 the heart's action, and the same is true if the nostrils be closed by the hand. 
 This arrest does not occur if the trachea be opened, and Rutherford regards the 
 result as due not to the stimulation of the sensory fibres of the trigeminus, but to 
 the state of the blood acting on the cardio-inhibitory nerve apparatus.] Hubert 
 and Roever found pressor fibres in the cervical sympathetic ; S. Mayer and Prib- 
 ram found that mechanical stimulation of the stomach, especially of its serosa, 
 caused pressor effects (§ 352, 12, e). According to Loven, the first effect of 
 stimulating every sensory nerve is a pressor action. 
 
 [If a dog be poisoned with curara, and the central end of one sciatic nerve be 
 stimulated, there is a great and steady rise of the blood pressure, chiefly owing to 
 the contraction of the abdominal blood vessels, and at the same time there is no 
 change in the heart beat. If, however, the animal be poisoned with chloral, 
 there is a fall of the blood pressure resembling a depressor effect.] 
 
 O. Naumann found that weak electrical stimulation of the skin caused at first contraction of the 
 blood vessels, especially of the mesentery, lungs and the web, with simultaneous excitement of the 
 cardiac activity and acceleration of the circulation (frog). Strong stimuli, however, had an oppo- 
 site effect, i.e., a depressor effect, with simultaneous decrease of the cardiac activity. The applica- 
 tion of heat and cold to the skin produces refiexly a change in the lumen of the blood vessels and 
 in the cardiac activity {RShrig, Winternitz). Pinching the skin causes contraction of the vessels 
 of the pia mater of the rabbit {ScAiiller), and the same result was produced by a warm bath, while 
 cold dilated the vessels. These results are due partly to pressor and partly to depressor effects, but 
 the chief cause of the dilatation of the blood vessels is the increased blood pressure due to the cold 
 constricting the cutaneous vessels. Heat, of course, has the opposite effect. 
 
 Depressor fibres, i.e., fibres whose stimulation diminishes the activity of the 
 vasomotor centre, are present in many nerves. They are specially numerous in 
 
698 LOCAL AND SECONDARY RESULTS OF VASOMOTOR ACTION. 
 
 the superior cardiac branch of the vagus, which is known as the depressor nerve 
 (§ 35 2 > 6). The trunk of the vagus below the latter also contains depressor 
 fibres (v. Bezold and Dreschfeld), as well as the pulmonary fibres (dog) (Taljan- 
 zeff). The latter also act as depressors during strong expiratory efforts (§ 74) ; 
 while Hering found that inflating the lungs (to 50 mm. Hg pressure) caused a fall 
 of the blood pressure (and also accelerated the heart beats — § 369, II). Stimu- 
 lation of the central end of sensory nerves, especially when it is intense and long- 
 continued, causes dilatation of the blood vessels in the area supplied them (Zovin). 
 According to Latschenberger and Deahna, all sensory nerves contain both pressor 
 and depressor fibres. 
 
 [If a rabbit be poisoned with curara, and the central end of the great auric- 
 ular nerve be stimulated, there is a double effect — one local and the other 
 general ; the blood vessels throughout the body, but especially in the splanchnic 
 area contract, so that there is a general rise of the blood pressure, while the blood 
 vessels of the ear are dilated. If the central end of the tibial nerve be stimu- 
 lated, there is a rise of the general blood pressure, but a local dilatation of the 
 saphena artery in the limb of that side (Loven). Again, the temperature of one 
 hand- and the condition of its blood vessels influences that of the other. If one 
 hand be dipped in cold water, the temperature of the other hand falls. Thus 
 pressor and depressor effects may be obtained from the same nerve. The vaso- 
 motor centre, therefore, primarily regulates the condition of the blood vessels, 
 but through them it obtains its importance by regulating and controlling the 
 blood supply according to the needs of an organ.] 
 
 The central artery of a rabbit's ear contracts regularly and rhythmically 3 to 5 times per minute. 
 Schiff observed that stimulation of sensory nerves caused a dilatation of the artery, which was pre- 
 ceded by a slight temporary constriction. 
 
 Depressor effects are produced in the area of an artery to which direct pressure is applied, as 
 occurs, for example, when the sphygmograph is applied for a long time — the pulse curves become 
 larger, and there are signs of diminished arterial tension (§ 75). 
 
 Rhythmical Contraction of Arteries. — In the intact body slow alternating contraction and 
 dilatation, without there being a uniform rhythm, have been observed in the arteries of the ear of 
 the rabbit, the membrane of a bat's wing, and the web of a frog's foot. This arrangement, observed 
 by Schiff, supplies more or less blood to the parts according to the action of external conditions. It 
 has been called a "periodic regulatory muscular movement." 
 
 Direct local applications may influence the lumen of the blood vessels ; cold and moderate elec- 
 trical stimuli cause contraction ; while, conversely, heat and strong mechanical or electrical stimuli 
 cause dilatation, although with the latter two there is usually a preliminary constriction. 
 
 Effect on Temperature. — The vasomotor nerves influence the temperature, 
 not only of individual parts, but of the whole body. 
 
 1. Local Effects. — Section of a peripheral vasomotor nerve, e. g., the cer- 
 vical sympathetic, is followed by dilatation of the blood vessels of the parts 
 supplied by it (such as the ear of the rabbit), the intra-arterial pressure dilating 
 the paralyzed walls of the vessels. Much arterial blood, therefore, passes into and 
 causes a congestion and redness of the parts, or hyperemia, while at the same time 
 the temperature is increased. There is also increased transudation through the 
 dilated capillaries within the dilated areas ; the velocity of the blood stream is of 
 course diminished, and the blood pressure increased. The pulse is also felt more 
 easily, because the blood vessels are dilated. Owing to the increase of blood 
 stream, the blood may flow from the veins almost arterial (bright red) in its char- 
 acters, and the pulse may even be propagated into the veins, so that the blood 
 spouts from them (67. Bernard). Stimulation of the peripheral end of a vaso- 
 motor nerve causes the opposite results — pallor, owing to contraction of the 
 vessels, diminished transudation, and fall of the temperature on the surface. The 
 smaller arteries may contract so much that their lumen is almost obliterated. Con- 
 tinued stimulation ultimately exhausts the nerve, and causes at the same time the 
 phenomena of paralysis of the vascular wall. 
 
 Secondary Results. — The immediate results of paralysis of the vasomotor nerves lead to other 
 
EFFECT ON THE TEMPERATURE OF THE WHOLE BODY. 699 
 
 effects ; the paralysis of the muscles of the blood vessels must lead to congestion of the blood in the 
 part; the blood moves more slowly, so that the parts in contact with the air cool more easily, and 
 hence the first stage of increase of the temperature may be followed by a fall of the temperature. 
 The ear of a rabbit with the sympathetic divided, after several weeks becomes cooler than the ear 
 on the sound one. If in man the motor muscular nerves, as well as the vasomotor fibres, are para- 
 lyzed, then the paralyzed limb becomes cooler, because the paralyzed muscles no longer contract 
 to aid in the production of heat (§ 338), and also because the dilatation of the muscular arteries, 
 which accompanies a muscular contraction, is absent. Should atrophy of the paralyzed muscles set 
 in the blood vessels also become smaller. Hence paralyzed limbs in man generally become cooler 
 as time goes on. The primary effect, however, in a limb, c. g., after section of the sciatic or lesion 
 of the brachial plexus, is an increase of the temperature. 
 
 If, at the same time, the vasomotor nerves of a large area of the skin be par- 
 alyzed, e. g., the lower half of the body after section of the spinal cord, then so 
 much heat is given off from the dilated blood vessels that either the warming of 
 the skin lasts for a very short time and to a slight degree, or there may be cooling 
 at once. Some observers ( Tschetschichin, Naunyn, Quincke, Heidenhain, Wood) 
 observed a rise of the temperature after section of the cervical spinal cord, but 
 Riegel did not observe this increase. 
 
 2. Effect on the Temperature of the Whole Body. — Stimulation or 
 paralysis of the vasomotor nerves of a small area has practically no effect on the 
 general temperature of the body. If, however, the vasomotor nerves of a consider- 
 able area of the skin be suddenly paralyzed, then the temperature of the entire 
 body falls, because more heat is given off from the dilated vessels than under 
 normal circumstances. This occurs when the spinal cord is divided high up in 
 the neck. The inhalation of a few drops of amyl nitrite, which dilates the blood 
 vessels of the skin, causes a fall of the temperature (Sassetzki and Manasseiri). 
 Conversely, stimulation of the vasomotor nerves of a large area increases the tem- 
 perature, because the constricted vessels give off less heat. The temperature in 
 fever may be partly explained in this way (§ 220, 4). 
 
 The activity of the heart, /*. e., the number and energy of the cardiac con- 
 tractions, is influenced by the condition of the vasomotor nerves. When a large 
 vasomotor area is paralyzed, the muscular blood channels are dilated, so that the 
 blood does not flow to the heart at the usual rate and in the usual amount, as the 
 pressure is considerably diminished. Hence the heart executes extremely small 
 and low contractions. Strieker even observed that the heart of a clog ceased to 
 beat on extirpating the spinal cord from the first cervical to the eighth dorsal 
 vertebra. Conversely, we know that stimulation of a large vasomotor area by 
 constricting the blood vessels raises the arterial blood pressure considerably. As 
 the arterial pressure affects the pressure within the left ventricle, it may act as a 
 mechanical stimulus to the cardiac wall, and increase the cardiac contractions both 
 in number and strength. Hence, the circulation is accelerated (Heidenhain, 
 Slavjansky). 
 
 Splanchnic. — By far the largest vasomotor area in the body is that controlled by the splanchnic 
 nerves, as they supply the blood vessels of the abdomen (§ 161) ; hence stimulation of their peri- 
 pheral ends is followed by a great rise of the blood pressure. When they are divided, there is such 
 a fall of the blood pressure, that other parts of the body become more or less ansemic, and the 
 animal may even die from " being bled into its own belly." Animals whose portal vein is ligatured 
 die for the same rea on (C. Luiiwig and Thiry), [see \ 87]. The capacity of the vascular system, 
 depending as it does in part upon the condition of the vasomotor nerves, influences the body weight. 
 Stimulation of certain vascular areas may cause the rapid excretion of water, and we may thus 
 account in part for the diminution of the body weight which has been sometimes observed after an 
 epileptic attack terminating with polyuria. 
 
 Trophic Disturbances sometimes occur after affections of the vasomotor nerves (§ 342, 1, c). 
 Paralysis of the vasomotor nerves not only causes dilatation of the blood vessels and local increase 
 of the blood pressure, but it may also cause increased transudation through the capillaries [f! 203]. 
 When the active contraction of the muscles is abolished, at the same time the blood stream becomes 
 slower; and in some cases the skin becomes livid owing to the venous congestion. There is a 
 diminution of the normal transpiration, and the epidermis may be dry and peel off in scales. The 
 growth of the hair and nails may be affected by the congestion of blood, and other tissues may also 
 suffer. 
 
700 PATHOLOGICAL VASOMOTOR PHENOMENA. 
 
 Vasomotor Centres in the Spinal Cord. — Besides the dominating centre 
 in the medulla oblongata, the blood vessels are acted upon by local or subordinate 
 vasomotor centres in the spinal cord, as is proved by the following observations : 
 If the spinal cord of an animal be divided, then all the blood vessels supplied by 
 vasomotor nerves below the point of section are paralyzed, as the' vasomotor fibres 
 proceed from the medulla oblongata. If the animal lives, the blood vessels re- 
 gain their tone and their former calibre, while the rhythmical movements of their 
 muscular walls are ascribed to the subordinate centres in the lower part of the 
 spinal cord {Lister, Goltz, Vulpian — § 362, 7). 
 
 These subordinate centres may also be influenced reflexly ; after destruction of the medulla ob- 
 longata the arteries of the frog's web still contract reflexly when the sensory nerves of the hind leg 
 are stimulated {Putnam, Nussbaum, Vulpian) . 
 
 If now the lower divided part of the cord be crushed, the blood vessels again 
 dilate, owing to the destruction of the subordinate centres. In animals which 
 survive this operation, the vessels of the paralyzed parts gradually recover their 
 normal diameter and rhythmical movements. This effect is ascribed to ganglia 
 which are supposed to exist along the course of the vessels. These ganglia [or 
 peripheral nervous mechanisms] might be compared to the ganglia of the heart, 
 and seem by themselves capable of sustaining the movements of the vascular wall. 
 Even the blood vessels of an excised kidney exhibit periodic variations of their 
 calibre ( C. Ludwig and Mossd). It is important to observe that the walls of the 
 blood vessels contract as soon as the blood becomes highly venous. Hence the 
 blood vessels offer a greater resistance to the passage of venous than to the arte- 
 rial blood ( C. Ludwig). Nevertheless, the blood vessels, although they recover 
 part of their tone and mobility, never do so completely. 
 
 The effects of direct mechanical, chemical, and electrical stimuli on blood vessels may be due to 
 their action on these peripheral nervous mechanisms. The arteries may contract so much as almost 
 to disappear, but sometimes dilatation follows the primary stimulus. 
 
 Lewaschfw found that limbs in which the vasomotor fibres had undergone degeneration reacted 
 like intact limbs to variations of temperature ; heat relaxed the vessels, and cold constricted them. 
 It is, however, doubtful if the variations of the vascular lumen depend upon the stimulation of the 
 peripheral nervous mechanisms. Amyl nitrite and digitalis are supposed to act on those hypothetical 
 mechanism 1 !. 
 
 The pulsating veins in the bat's wing still continue to beat after section of all their nerves, which 
 is in favor of the existence of local nervous mechanisms (Lucksinger, Sehiff). 
 
 Influence of the Cerebrum. — The cerebrum influences the vasomotor centre, 
 as is proved by the sudden pallor that accompanies some psychical conditions, 
 such as fright or terror. There is a centre in the gray matter of the cerebrum 
 where stimulation causes cooling of the opposite side of the body. 
 
 Although there is one general vasomotor centre in the medulla oblongata which 
 influences all the blood vessels of the body, it is really a complex composite centre, 
 consisting of a number of closely aggregated centres, each of which presides over 
 a particular vascular area. We know something of the hepatic (§ 175) and renal 
 centres (§ 276). 
 
 Many poisons excite the vasomotor nerves, such as ergotin, tannic acid, copaiba, and cubebs ; 
 others first excite, and then paralyze, e.g., chloral hydrate, morphia, landanosin, veratrin, nicotin, 
 Calabar bean, alcohol; others rapidly paralyze them, e.g., amyl nitrite, CO ({! 17), atropin, mus- 
 carin. The paralytic action of the poison is proved by the fact that, after section of the vagi and 
 accelerantes, neither the pressor nor the depressor nerves, when stimulated, produce any effect. 
 Many pathological conditions affect the vasomotor nerves. 
 
 The veins are also influenced by vasomotor nerves (Goltz), and so are the 
 lymphatics, but we know very little about this condition. 
 
 Pathological. — The angio-neuroses, or nervous affections of blood vessels, form a most im- 
 portant group of diseases. The parts primarily affected may be either the peripheral nervous 
 mechanisms, the subordinate centres in the cord, the dominating centre in the medulla, or the gray 
 matter of the cerebrum. The effect may be direct or reflex. The dilatation of the vessels may 
 also be due to stimulation of vasodilator nerves, and the physician must be careful to distinguish 
 
VASODILATOR CENTRE AND VASODILATOR NERVES. 701 
 
 whether the result is due to paralysis of the vaso- constrictor nerves or stimulation of the vaso-dilator 
 fibres. 
 
 Angio-neuroses of the skin occur in affections of the vasomotor nerves, either as a diffuse 
 redness or pallor ; or there may be circumscribed affections. Sometimes, owing to the stimula- 
 tion of individual Vasomotor nerves, there are local cutaneous arterio spasms (Nothnagel). In 
 certain acute febrile attacks— after previous initial violent stimulation of the vasomotor nerves, 
 especially during the cold stage of fever — there may be different forms of paralytic phenomena of 
 the cutaneous vessels. In some cases of epilepsy in man, Trousseau observed irregular, red, angio- 
 paralytic patches (taches cerebrates ). Continued strong stimulation may lead to interruption of 
 the circulation, which may result in gangrene of the skin ( IVeiss) and deeper-seated parts. 
 
 Hemicrania, due to unilateral spasm of the branches of the carotid on the head, is accompanied 
 by. severe headache (Du Bois-Reymond). The cervical sympathetic nerve is intensely stimulated; 
 a pale, collapsed and cool side of the face, contraction of the temporal artery like a firm whipcord, 
 dilatation of the pupil, secretion of thick saliva are sure signs of this affection. This form may be 
 followed by the opposite condition of paralysis of the cervical sympathetic, where the effects are 
 reversed. Sometimes the two conditions may alternate. 
 
 Basedow's disease is a remarkable condition, in which the vasomotor nerves are concerned ; 
 the heart beats very rapidly (90 to 120 to 200 beats per minute), causing palpitation; there is 
 swelling of the thyroid gland (struma) and projection of the eyeballs (exophthalmos), with 
 imperfectly codrdinated movements of the upper eyelid, whereby the plane of vision is raised or 
 lowered. Perhaps in this disease we have to deal with a simultaneous stimulation of the accelerans 
 cordis (§ 370), the motor fibres of Miiller's muscles of the orbit and eyelids (fj 347, I), as well as 
 of the vaso-dilators of the thyroid gland. The disease may be due to direct stimulation of the 
 sympathetic channels or their spinal origins, or it may be referred to some reflex cause. It has 
 also been explained, however, thus, that the exophthalmus and struma are the consequence 
 of vasomotor paralysis, which results in enlargement of the blood vessels, while the increased 
 cardiac action is a sign of the diminished or arrested inhibitory action of the vagus. All 
 these phenomena may be caused, according to Filehne, by injury to the upper part of both 
 restiform bodies in rabbits. 
 
 Visceral Angio-neuroses. — The occurrence of sudden hyperaemia with transudations and 
 ecchymoses in some thoracic or abdominal organs may have a neurotic basis. As already men- 
 tioned, injury to the pons, corpus striatum and optic thalamus may give rise to hyperemia, and 
 ecchymoses in the lungs, pleurae, intestines and kidneys. According to Brown-Sequard, compression 
 or section of one-half of the pons causes ecchymoses, especially in the lung of the opposite side; 
 he also observed ecchymoses in the renal capsule after injury of the lumbar portion of the spinal 
 cord (<} 379). 
 
 The dependence of diabetes mellitus upon injury to the vasomotor nerves is referred to in 
 $ 175; the action of the vasomotor nerves on the secretion of urine in \ 276; and fever in 
 I 220. 
 
 372. VASO-DILATOR CENTRE AND VASO-DILATOR 
 NERVES. — Although a vaso-dilator centre has not been definitely proved 
 to exist in the medulla, still its existence there has been surmised. Its action is 
 opposite to that of the vasomotor centre. The centre is certainly not in a con- 
 tinuous or tonic state of excitement. The vaso-dilator nerves behave in their 
 functions similarly to the cardiac branches of the vagus; both, when stimulated, 
 cause relaxation and rest {Schiff, CI. Bernard). [They are not paralyzed, how- 
 ever, by a large dose of atropin.] Hence, these nerves have been called vaso- 
 inhibitory, vaso-hypotonic or vaso-dilator nerves. 
 
 The existence of vaso-dilator nerves is assumed in accordance with such facts as 
 the following : If the chorda tympani be divided, there is no change in the 
 blood vessels of the sub-maxillary gland ; but if its peripheral end be stimulated, 
 in addition to other results (§ 145), there is dilatation of the blood vessels of the 
 sub-maxillary glands, so that its veins discharge bright florid blood, while they 
 spout like an artery. Similarly, if the nervi erigentes be divided, there is no 
 effect on the blood vessels of the penis (§ 362, 4) ; but if their peripheral ends be 
 stimulated with Faradic electricity, the sinuses of the corpora cavernosa dilate, 
 become filled with blood, and erection takes place (§ 436). [Other examples in 
 muscle and elsewhere are referred to below.] 
 
 Dyspnceic blood stimulates this centre as well as the vasomotor centre, so that 
 the cutaneous vessels are dilated, while simultaneously the vessels of the internal 
 organs are contracted and the organs anaemic, owing to the stimulation of their 
 vasomotor centre (Dastre and Moral). 
 
702 SPASM AND SWEAT CENTRE. 
 
 Course of the Vasodilator Nerves. — To some organs they pass as special nerves ; to other 
 parts of the body, however, they proceed along with the vasomotor and other nerves. According to 
 Dastra and Morat, the vaso-dilator nerves for the bucco-labial region (dog) pass out from the 
 cord by the 1st to the 5th dorsal nerves, and go through the rami communicantes into the sympa- 
 thetic, then to the superior cervical ganglion, and, lastly, through the carotid and inter carotid plexus 
 into the trigeminus. [The fibres occur in the posterior segment of the ring of Vieussens, and if they 
 be stimulated there is dilatation of the vessels in the lip and cheek on that side (p. 652).] The 
 maxillary branch of the trigeminus, however, also contains vaso-dilator fibres proper to itself 
 ( Laffont). In the gray matter of the cord there is a special subordinate centre for the vaso-dilator 
 fibres of the bucco-labial region. This centre may be acted on reflexly by stimulation of the vagus, 
 especially its pulmonary branches, and even by stimulating the sciatic nerve. The ear receives its 
 nerves from the 1st dorsal and lowest cervical ganglion, the upper limb from the thoracic portion, 
 and the lower limb from the abdominal portion of the sympathetic. The vaso-dilator fibres run 
 to the sub-maxillary and sub-lingual glands in the chorda tympani (J 349, 4), while those for the 
 posterior part of the tongue run in the glosso-pharyngeal nerve (§ 351, 4 — Vulpian). Perhaps 
 the vagus contains those for the kidneys (§ 276J. Stimulation of the nervi erigentes pro- 
 ceeding from the sacral plexus causes dilatation of the. arteries of the penis, together with con- 
 gestion of the corpora cavernosa (\ 436) {Eckhard, Lovin). Eckhard found that erection of the 
 penis can be produced by stimulation of the spinal cord and of the pons as far as the peduncles, 
 which may explain the phenomenon of priapism in connection with pathological irritations in these 
 regions. 
 
 The muscles receive their vaso-dilator fibres for their vessels through the trunks of the motor 
 nerves. Stimulation of a motor nerve or the spinal cord causes not only contraction of the corre- 
 sponding muscles, but also dilatation of their blood vessels ({} 294, II — C. Ludwig and Sczelkow, 
 Hafiz, Gaskell, Heidenhain) — the dilatation of the vessels taking place even when the muscle is 
 prevented from shortening. [Gaskell observed under the microscope the dilatation produced by 
 stimulation of the nerve to the mylo-hyoid muscle of the frog.] Goltz showed that in the nerves 
 to the limbs, e.g., in the sciatic nerve, the vasomotor and vaso-dilator fibres occur in the same nerve 
 If the peripheral end of this nerve be stimulated, immediately after it is divided, the actign of the 
 vaso-constrictor fibres overcomes that of the dilators. If the peripheral end be stimulated several 
 days after the section, when the vaso-constrictors have lost their excitability, the blood vessels dilate 
 under the action of the vaso-dilator fibres. Stimuli, which are applied at long intervals to the nerve, 
 act especially on the vasodilator fibres ; while tetanizing stimuli act on the vasomotors. The sciatic 
 nerve receives both kinds of fibres from the sympathetic. It is assumed that the peripheral nervous 
 mechanisms in connection with the blood vessels are influenced by both kinds of vascular nerves; 
 the vasomotats (constrictors) increase, while the vaso-dilators diminish, the activity of these mech- 
 anisms or ganglit. Psychical conditions act upon the vasodilator nerves; the blush of shame, 
 which is not confinetf to thejace, but may even extend over the whole skin, is probably due to stim- 
 ulation of the vaso dilator centra. 
 
 Influence on Temperature. — The vaso-dilator nerves obviously have a considerable influence 
 on the temperature of the body and on the heal of the individual parts of the body. Both vascular 
 centres must act as important regulatory mechanisms for the radiation ol heat through the cutaneous 
 vessels (§ 214, II). Probably they are kept in activity reflexly by sensory nerves. Disturbances in 
 their function may lead to an abnormal accumulation of heat, as in fever (g 220), or to abnormal 
 cooling (g 213, 7). Some observers, however, assume the existence of an intracranial "heat-regu- 
 lating centre " (Tschetschichin, Naunyn, Quincke), whose situation is unknown. According ta 
 Wood, separation of the medulla oblongata from the pons causes an increased radiation and a di- 
 minished production of heat, due to the cutting off of the influences from the heat -regulating centre 
 (8 377). 
 
 373. THE SPASM CENTRE— THE SWEAT CENTRE.— Spasm 
 Centre. — In the medulla oblongata, just where it joins the pons, there is a cen- 
 tre whose stimulation causes general spasms. The centre may be excited by sud- 
 denly producing a highly venous condition of the blood ("asphyxia spasms," in 
 cases of drowning in mammals, but not in frogs) by sudden ansemia of the medulla 
 oblongata, either in consequence of hemorrhage or ligature of both carotids and 
 subclavians {Kussmaul and Tenner), and, lastly, by sudden venous stagnation caused 
 by compressing the veins coming from the head. In all these cases the stimula- 
 tion of the centre is due to the sudden interruption of the normal exchange of 
 the gases. When these factors act quite gradually, death may take place without 
 convulsions. Intense direct stimulation of the medulla, as by its sudden destruc- 
 tion, causes general convulsions. 
 
 Position. — Nothnagel attempted by direct stimulation to map out its position in rabbits ; it ex- 
 tends from the area above the ala cinerea upward to the corpora quadrigemina. It is limited exter- 
 
PSYCHICAL FUNCTIONS OF THE BRAIN. 703 
 
 nally by the locus cceruleus and the tuberculurn acusticum. In the frog it lies in the lower half of 
 the 4th ventricle {Heubel). The centre is affected in extensive reflex spasms (J 364, 6), eg., in 
 poisoning with strychnin and in hydrophobia. 
 
 Poisons. — Many inorganic and organic poisons, most cardiac poisons, nicotin, picrotoxin, ammo- 
 nia (g 277), and the compounds of barium, cause death after producing convulsions, by acting on 
 the spasm centre {Kober, Heubel, Bohtn). 
 
 If the arteries going to the brain be ligatured so as to paralyze the oblongata, then on ligaturing 
 the abdominal aorta spasms of the lower limbs occur, owing to the anaemic stimulation of the motor 
 ganglia of the spinal cord (Sigm. Mayer). 
 
 Pathological — Epilepsy. — Schroder van der Kolk found the blood vessels of the oblongata dilated 
 and increased in cases of epilepsy. Brown-SSquard observed that injury to the central ur peripheral 
 nervous system (spinal cord, oblongata, peduncle, corpora quadrigemma, sciatic nerve) of guinea 
 pigs produced epilepsy, and this condition even became hereditary. Stimulation of the cheek or 
 ol the face, " epileptic zone," on the same side as the injury (spinal cord), caused at once an at- 
 tack of epilepsy; but when the peduncle was injured the opposite side must be stimulated. West- 
 phal made guinea pigs epileptic by repeated light blows on the skull, and this condition also became 
 hereditary. In these cases there was effusion of blood in the medulla oblongata and upper part of 
 the spinal cord {\\ 375 and 378, I). Direct stimulation of the cerebrum also produces epileptic 
 convulsions. Strong electrical stimulation of the motor areas of the cortex cerebri is often followed 
 by an epileptic attack (\ 375)- [It is no unfrequent occurrence that, while one is stimulating the 
 motor areas of the cortex cerebri of a dog, to find the animal exhibiting symptoms of local or general 
 epilepsy.] 
 
 Sweat Centre. — A dominating centre for the secretion of the sweat of the 
 entire surface of the body (§ 289, II) — with subordinate spinal centres (§ 362, 8) 
 — occurs in the medulla oblongata (Adamkiewicz, Marmi, Nawrockt). It is 
 double, and in rare cases the excitability is unequal on the two sides, as is mani- 
 fested by unilateral perspiration (§ 289, 2). 
 
 Poisons. — Calabar bean, nicotin, picrotoxin, camphor, ammonium acetate, cause a secretion of 
 sweat, by acting directly on the sweat centre. Muscarin causes local stimulation of the peripheral 
 sweat fibres — it causes sweating of the hind limbs after section of the sciatic nerves. Atropin ar- 
 rests the action of muscarin (Oil, Wood, Field, Nawrocki). 
 
 [Regeneration of the Spinal Cord. — In some animals true nervous matter is reproduced after 
 part of the spinal cord has been destroyed, at least this is so in tritons and lizards (H. Miiller). As 
 is well known, in these animals when the tail is removed it is reproduced, and Miiller found that a 
 part of the spinal cord corresponding to the new part of the tail is reproduced. Morphologically the 
 elements were the same, but the spinal nerves were not reproduced, while physiologically the new 
 nerve substance was not functionally active ; it corresponds, as it were, to a lower stage of develop- 
 ment. According to Masius and Vanlair, an excised portion of the spinal cord of a frog is repro- 
 duced after six months ; while Brown-Sequard maintains that reunion of the divided surfaces of the 
 cord takes place in pigeons after six to fifteen months. A partial reunion is asserted to occur in dogs 
 by Dentan, Naunyn, and Eichhorst, although Schieferdecker obtained only negative results, the 
 divided ends being united only by connective tissue (Schwalbe).~\ 
 
 374. PSYCHICAL FUNCTIONS OF THE BRAIN.— The hemi- 
 spheres of the cerebrum are usually said to be the seat of all the psychical activities. 
 Only when they are intact are the processes of thinking, feeling, and willing pos- 
 sible. After they are destroyed, the organism comes to be like a complicated 
 machine, and its whole activity is only the expression of the external and internal 
 stimuli which act upon it. The psychical activities appear to be located in both 
 hemispheres, so that after destruction of a considerable part' of one of them the 
 other seems to act in place of the part destroyed. [Objection has been taken to 
 the term the "seat of" the will and intelligence, and undoubtedly it is more 
 consistent with what we know, or rather do not know, to say that the existence of 
 volition and intelligence is dependent on the connection of the cerebral cortex 
 with the rest of the brain.] 
 
 [That a certain condition of the cerebral hemispheres is necessary for the manifestation of the in- 
 tellectual faculties is admitted on all hands, for compression of the brain, e.g., by a depressed frac- 
 ture of the skull, and sudden cessation of the supply of blood to the brain abolish consciousness. The 
 intellectual faculties are affected by inflammation of the meninges involving the surface of the brain, 
 the action of drugs affects the intellectual and other faculties, but while all this is admitted we can- 
 not say precisely upon what parts of the brain ideation depends. The pre-frontal area, or the con- 
 volutions in front of the ascending frontal supplied by the anterior cerebral artery, are sometimes 
 
704 EXTIRPATION OF THE CEREBRUM. 
 
 regarded a; the anatomical substratum of certain mental acts. At any rate, electrical stimulation of 
 these parts is not followed by muscular motion, and, according to Ferrier, if this region be extirpated 
 in the monkey, there is no motor or sensory disturbance in this animal ; the animal exhibits emo- 
 tional feeling, all its special senses remain, and the power of voluntary motion is retained, but never- 
 theless there is a decided alteration in the animal's character and behavior, so that it exhibits consid- 
 erable psychological alterations, and, according to Ferrier, " it has lost to all appearance the faculty 
 of attention and intelligent observation."] 
 
 Observations on Man. — Cases in which considerable unilateral lesions or destruction of one 
 hemisphere have taken place, without the psychical activities appearing to suffer, sometimes occur. 
 The following is a case communicated by Longet: A boy, 1 6 years of age, had his parietal bone 
 fractured by a stone falling on it, so that part of the protruding brain matter had to be removed. 
 On reapplying the bandages more brain matter had to be removed. After 18 days he fell out of 
 bed, and more brain matter protruded, which was-removed. On the 35th day he got intoxicated, 
 tore off the bandages, and with them a part of the brain matter. After his recovery the boy still 
 retained his intelligence, but he was hemiplegic. Even when both hemispheres are moderately 
 destroyed the intelligence appears to be intact ; thus Trousseau describes the case of an officer 
 whose fore-brain was pierced transversely by a bullet. There was scarcely any appearance of his 
 mental or bodily faculties being affected. In other cases, destruction of parts of the brain pecu- 
 liarly alters the character. We must be extremely careful, however, in forming conclusions in all 
 such cases. [In the celebrated " American crowbar case " recorded by Bigelow, a young man 
 was hit by a bar of iron \y£ inch in diameter, which traversed the anterior part of the left hemi- 
 sphere, going clear out at the top of his head. This man lived for thirteen years without any per- 
 manent alterations of motor or sensory functions ; but " the man's disposition and character were 
 observed to have undergone a serious change." There were, however, some changes which might 
 be referable to injury to the frontal region. In all cases it is most important to know both the 
 exact site and the extent of the lesion. Ross points out that the characteristic features of lesions 
 in the pre-frontal cortical region are afforded by " psychical disturbances, consisting of dementia, 
 apathy and somnolency."] 
 
 Imperfect Development of the Cerebrum. — Microcephalia and hydrocephalus yield every 
 result between diminution of the psychical activities and idiocy. Extensive inflammation, degen- 
 eration, pressure, anaemia of the blood vessels, and the actions of many poisons produce the same 
 effect. 
 
 Flourens' Doctrine. — Flourens assumed that the whole of the cerebrum is concerned in 
 every psychical process. From his experiments on pigeons, he concluded that, if a small part of the 
 hemispheres remained intact, it was sufficient for the manifestation of the mental functions; just in 
 proportion as the gray matter of the hemispheres is removed all the functions of the cerebrum are 
 emeebled, and when all the gray matter is removed all the functions are abolished. According to 
 this view, neither the different faculties nor the different perceptions are localized in special areas. 
 Goltz holds a somewhat similar view to that of Flourens. He assumes that if an uninjured part of 
 the cerebrum remain, it can to a certain extent perform the functions of the parts that have been 
 removed. This Vulpian has called the law of " functional substitution " (loi de suppleance). 
 
 The phrenological doctrine of Gall (f 1828) and Spurzheim assumes that the different mental 
 faculties are located in different parts of the brain, and it is assumed that a large development of a 
 particular organ may be detected by examining the external configuration of the head (Crani- 
 oscopy). 
 
 Extirpation of the Cerebrum. — 'After the removal of both cerebral hemi- 
 spheres in animals, every voluntary movement and every conscious impression and 
 sensory perception entirely ceases. On the other hand, the whole mechanical 
 movements and the maintenance of the equilibrium of the movements are retained. 
 The maintenance of the equilibrium depends upon the mid-brain, and is 
 regulated by important reflex channels (§ 379,). The mid-brain (corpora quadri- 
 gemina) is connected not only with the gray matter of the spinal cord and 
 medulla oblongata, the seat of extensive reflex mechanisms (§ 367), but it also 
 receives fibres coming from the higher organs of sense, which also excite move- 
 ments reflexly. The corpora quadrigemina are also supposed to contain a reflex 
 inhibitory apparatus (§ 361, 2). The joint action of all these parts makes the 
 corpora quadrigemina one of the most important organs for the harmonious exe- 
 cution of movements, and this even in a higher degree than the medulla oblongata 
 itself {Goltz). Animals with their corpora quadrigemina intact retain the equi- 
 librium of their bodies under the most varied conditions, but they lose this power 
 as soon as the mid-brain is destroyed {Goltz). Christiani locates the coordinating 
 centre for the change of place and the maintenance of the equilibrium in mam- 
 mals in front of the inspiratory centre in the 3d ventricle (§ 368). 
 
REMOVAL OF THE CEREBRUM FROM A FROG. 
 
 705 
 
 That impressions from the skin and sense organs are concerned in the maintenance of the 
 equilibrium is proved by the following facts : A frog without its cerebrum at once loses its power of 
 balancing itself as soon as the skin is removed from its hind limbs. The action of impressions 
 communicated through the eyes is proved by the difficulty or impossibility of maintaining the equi- 
 librium in nystagmus (§ 350), and by the vertigo which often accompanies paralysis of the external 
 ocular muscles. In persons whose cutaneous sensibility is diminished, the eyes are the chief organs 
 for the maintenance of the equilibrium ; they fall over when the eyes are closed. [This is well 
 illustrated in cases of locomotor ataxia (p. 672).] 
 
 Frog. — A frog with its cerebrum removed retains its power of maintaining its 
 equilibrium. It can sit, spring or execute complicated coordinated movements 
 when appropriate stimuli are applied ; when placed on its back, it immediately 
 turns into its normal position on its belly; if stimulated, it gives one or two 
 springs and then comes to rest ; when thrown into water, it swims to the margin 
 of the vessel, and it may crawl up the side, and sit passive upon the edge of the 
 vessel. When incited to move, it exhibits the most complete harmony and unity 
 in all its movements. It sits on the same place continually as if in sleep, it takes 
 no food, it has no feelings of hunger and thirst, it shows no symptoms of fear, 
 and ultimately, if left alone, it becomes desiccated like a mummy on the spot 
 
 Fig. 419. 
 
 vwmamH /k 
 
 Fig. 421. 
 
 Frog without its cerebrum avoiding an 
 object placed in its path. 
 
 Fig. 420. 
 
 Pigeon with its cerebral hemispheres removed. 
 
 Frog without its cerebrum moving on au 
 inclined board (Goltz). 
 
 where it sits. [If the flanks of such a frog be stroked, it croaks with the utmost 
 regularity according to the number of times it is stroked. Langendorff has 
 shown that a frog croaks under the same circumstances when both optic nerves 
 are divided. It seems to be influenced by light ; for, if an object be placed in 
 front of it so as to throw a strong shadow, then on stimulating the frog it will 
 spring not against the object, a, but in the direction, b (Fig. 419). Steiner finds 
 that if a glass plate be substituted for an opaque object like a book, the frog 
 always jumps against this obstacle. Its balancing movements on a board are 
 quite remarkable and acrobatic in character. If it be placed on a board, and the 
 board gently inclined (Fig. 420), it does not fall off as a frog merely with its 
 spinal cord will do, but as the board is inclined so as to alter the animal's centre 
 of gravity it slowly crawls up the board until its equilibrium is restored. If the 
 board be sloped as in Fig. 420 it will crawl up until it sits on the edge, and if the 
 board be still further tilted, the frog will move as indicated in the figure. It only 
 does so, however, when the board is inclined, and it rests as soon as its centre of 
 gravity is restored. It responds to every stimulus just like a complex machine, 
 answering each stimulus with an appropriate action.] 
 45 
 
706 REMOVAL OF THE CEREBRUM. 
 
 A pigeon without its cerebral hemispheres behaves in a similar manner (Fig. 
 421). When undisturbed it sits continuously, as if in sleep, but when stimulated 
 it shows complete harmony of all its movements ; it can walk, fly, perch, and 
 balance its body. The sensory nerves and those of special sensation conduct 
 impulses to the brain ; they only discharge reflex movements, but they do not 
 excite conscious impressions. Hence the bird starts when a pistol is fired close 
 to its ear; it closes its eyes when it is brought near a flame, and the pupils 
 contract ; it turns away its head when the vapor of ammonia is applied to its 
 nostrils. All these impressions are not perceived as conscious perceptions. The 
 perceptive faculties — the will and memory — are abolished ; the animal never 
 takes food or drinks spontaneously. But if food be placed at the back part of its 
 throat it is swallowed [reflex act], and in this way the animal may be maintained 
 alive for months {Flourens, Longet, Goltz, and others). 
 
 Mammals (rabbit), owing to the great loss of blood consequent on removal 
 of the cerebrum, are not well suited for experiments of this kind.* Immediately 
 after the operation they show great signs of muscular weakness. When they recover 
 they present the same general phenomena ; only when they are stimulated they 
 run, as it were, blindfold against an obstacle. Vulpian observed a peculiar shriek 
 or cry which such a rabbit makes under the circumstances. Sometimes even in 
 man a peculiar cry is emitted in some cases of pressure or inflammation rendering 
 the cerebral hemispheres inactive. 
 
 Observations on somnambulists show that in man also complete harmony of 
 all movements may be retained, without the assistance of the will or conscious 
 impressions and perceptions. As a matter of fact, many of our ordinary move- 
 ments are accomplished without our being conscious of them. They take place 
 under the guidance of the basal ganglia. 
 
 The degree of intelligence in the animal kingdom is, in relation to the size of the cerebral 
 hemispheres, in proportion to the mass of the other parts of the central nervous system. Taking 
 the brain alone into consideration, we observe that those animals have the highest intelligence in 
 which the cerebral hemispheres greatly exceed the mid-brain in weight. The mid-brain is repre- 
 sented by the optic lobes in the lower vertebrates, and by the corpora quadrigemina in the higher 
 vertebrates. In Fig. 428, VI represents the brain of a carp ; V, frog ; and IV, pigeon. In all 
 these cases 1 indicates the cerebral hemispheres ; 2, the optic lobes ; 3, the cerebellum ; and 4, the 
 medulla oblongata. In the carp the cerebral hemispheres are smaller than the optic lobes, in the 
 frog they exceed the latter in size. In the pigeon the cerebrum begins to project backward over the 
 cerebellum. The degree of intelligence increases in these animals in this proportion. In the dog's 
 brain (Fig. 428, II) the hemispheres completely cover the corpora quadrigemina, but the cerebellum 
 still lies behind the cerebrum. In man the occipital lobes of the cerebrum completely overlap the 
 cerebellum (Fig. 424). [The projection of the occipital lobes over the cerebellum is due to the 
 development of the frontal lobes pushing backward the convolutions that lie behind them, and not 
 entirely to increased development of the occipital lobes.] 
 
 Meynert's Theory. — According to Meynert, we may represent this relation in another way. As 
 is known, fibres proceed downward from the cerebral hemispheres through the crusta or basis of the 
 cerebral peduncle. These fibres are separated from the upper fibres or tegmentum of the peduncle 
 by the locus niger, the tegmentum being connected with the corpora quadrigemina and the optic 
 thalamus. The larger, therefore, the cerebral hemispheres the more numerous will be the fibres 
 proceeding from it. In Fig. 428, II, is a transverse section of the posterior corpora quadrigemina, 
 with the aqueduct of Sylvius and both cerebral peduncles of an adult man ; /, p, is the crusta of 
 each peduncle, and above it lies the locus niger, j. Fig. 428, IV, shows the same parts in a monkey ; 
 
 III, in a dog; and V, in a guinea pig. The crusta diminishes in the above series. There is a cor- 
 responding diminution of the cerebral hemispheres, and at the same time in the intelligence of the 
 corresponding animals. 
 
 Sulci and Gyri. — The degree of intelligence also depends upon the number and depth of the 
 convolutions. In the lowest vertebrates (fish, frog, bird) the furrows or sulci are absent (Fig. 428, 
 
 IV, V, VI) ; in the rabbit there are two shallow furrows on each side (III). The dog has a com- 
 plexly furrowed cerebrum (I, II). Most remarkable is the complexity of the sulci and convolu- 
 tions of the cerebrum of the elephant, one of the most intelligent of animals. Nevertheless some 
 very stupid animals, as the ox, have very complex convolutions. 
 
 The absolute weight of the brain cannot be taken as guide to the intelligence. The elephant 
 has absolutely the heaviest brain, but man has relatively the heaviest brain. 
 
 The mean weight of the brain in man is about 1358 grammes; of woman, 1220 grammes 
 
REACTION TIME. 
 
 707 
 
 {Bischoff). [We ought, also, to take into account the complexity of the convolutions and the 
 depth of the gray matter, its vascularity, and the extent of anastomoses between its nerve cells.] 
 
 Time an Element in all Psychical Processes. — Every psychical process 
 requires a certain time for its occurrence — a certain time always elapses between 
 the application of the stimulus and the conscious reaction. 
 
 Nature of Stimulus. 
 
 Reaction Time. 
 
 Name of Observer, 
 
 Shock on forehead 
 
 .12 
 ■'3 
 •17 
 
 •«3 
 •15 
 .16 
 
 ... { 
 
 •IS 
 .16 
 .16 
 •23 
 
 Exner. 
 Do. 
 Do. 
 Do. 
 Do. 
 Donders. 
 
 v. Vintschgau and 
 Honigschmied. 
 Do. 
 Do. 
 Do. 
 Do. 
 
 Shock on toe of left foot 
 
 
 Visual impression of electric spark 
 
 Hearing a sound 
 
 Saline taste 
 
 Taste of sugar 
 
 " acids 
 
 " quinine 
 
 4 i 
 
 Reaction Time. — This time is known as " reaction time" and is distinctly longer than the 
 simple reflex time required for a reflex act. It can be measured by causing the person experimented 
 on to indicate by means of an electrical signal the moment when the stimulus is applied. The 
 reaction time consists of the following events: (1) The duration of perception, i.e., when we become 
 conscious of the impression ; (2) the duration of the time required to direct the attention to the 
 impression ; and (3) the duration of the voluntary impulse, together with (4) the time required for 
 conducting the impulse in the afferent nerves to the centre, and (5) the time for the impulse to travel 
 outward in the motor nerves. If the signal be made with the hand, then the reaction time for the 
 impression of soundis 0.136 to 0.167 second; for taste, 0.15 to 0.23; touch, 0.133 t0 0.201 second 
 {Horsck, v. Vintschgau and Honigschmied, Auerbach, Exner, and others) ; for olfactory impres- 
 sions, which, of course, depend upon many conditions (the phase of respiration, current of air), 0.2 
 to 0.5 second. Intense stimulation, increased attention, practice, expectation, and knowledge of the 
 kind of stimulus to be applied, all diminish the time. Tactile impressions are most rapidly perceived 
 when they are applied to the most sensitive parts (v. Vintschgau). The time is increased with very 
 strong stimuli, and when objects difficult to be distinguished are applied (z/; Helmholtz and Baxt). 
 The time required to direct the attention to a number consisting of 1 to 3 figures, Tigerstedt and 
 Bergquist found to be 0.015 to °'°35 second. Alcohol and the anaesthetics alter the time; according 
 to their degree of action they shorten or lengthen it [JCraplin). In order that two shocks applied 
 after each other be distinguished as two distinct impressions, a certain interval must elapse between 
 the two shocks; for the ear, 0.002 to 0.0075 second; for the eye, 0.044 to °-47 second: for the 
 finger, 0.277 second. 
 
 [The Dilemma. — When a person is experimented on, and is not told whether the right or left 
 side is to be stimulated or what colored disk may be presented to the eye, then the time to respond 
 correctly is longer.] 
 
 [Drugs and other conditions affect the reaction time. Ether and chloroform lengthen it, while 
 alcohol does the same, but the person imagines he ready reacts quicker. Noises also lengthen it.] 
 
 In sleep and waking we observe the periodicity of the active and passive conditions of the brain. 
 During sleep there is diminished excitability of the whole nervous system, which is only partly due 
 to the fatigue of afferent nerves, but is largely due to the condition of the central nervous system. 
 During sleep we require to apply strong stimuli to produce reflex acts. In the deepest sleep the 
 psychical or mental processes seem to be completely in abeyance, so that a person asleep might be 
 compared to an animal with its cerebral hemispheres removed. Toward the approach of the period 
 when a person wakens, psychical activity may manifest itself in the form of dreams, which differ, 
 however, from normal mental processes. They consist either of impressions, where there is no 
 objective cause (hallucinations), or of voluntary impulses which are not executed, or trains of thought 
 where the reasoning and judging powers are disturbed. Often, especially near the time of waking, 
 the actual stimuli may so act as to give rise to impressions which become mixed with the thoughts 
 of a dream. The diminished activity of the heart (f! 70, 3, c), the respiration ($S 127, 4), the gastric 
 and intestinal movements (§ 213, 4), the formation of heat ($ 216, 4), and the secretions, point to a 
 diminished excitability of the corresponding nerve centres, and the diminished reflex excitability to 
 a corresponding condition of the spinal cord. The pupils are contracted during sleep the deeper 
 the latter is, so that in the deepest sleep they do not become contracted on the application of light. 
 The pupils dilate when sensory or auditory stimuli are applied, and that the more the lighter the 
 
708 HYPNOTISM. 
 
 sleep; they are widest at the moment of awaking (Plothe). [Hughlings- Jackson finds that the 
 retina is more anaemic than in the waking state.] During sleep there seems to be a condition of 
 increased action of certain sphincter muscles — those for contracting the pupil and closing the eyelids 
 {Rosenbach). The soundness of the sleep may be determined by the intensity of the sound required 
 to waken a person. Kohlschutter found that at first sleep deepens very quickly, then more slowly, 
 and the maximum is reached after one hour (according to Monninghoff and Priesbergen after ij£ 
 hours) ; it then rapidly lightens, until several hours before waking it is very light. External or 
 internal stimuli may suddenly diminish the depth of the sleep, but this may be followed again by 
 deep sleep. The deeper the sleep, the longer it lasts. [Durham asserts that the brain is ansemic; 
 the arteries and veins of the pia mater are contracted during sleep and the brain is smaller, but is 
 this cause or effect ?] 
 
 The cause of sleep is the using up of the potential energy, especially in the central nervous 
 system, which renders a restitution of energy necessary. Perhaps the accumulation of the decom- 
 position products of the nervous activity may also act (? lactates— Preyer) as producers of sleep. 
 Sleep cannot be kept up for above a certain time, nor can it be inteirupted voluntarily. Many 
 narcotics rapidly produce sleep. [The diastolic phase of cerebral activity, as sleep has been called, 
 is largely dependent on the absence of stimuli. We must suppose that there are two factors, one 
 central, represented by the excitability of the cerebrum, which will vary under different conditions, 
 and the impulses reaching the cerebrum through the different sense organs. We know that a 
 tendency to sleep is favored by removal of external stimuli, by shutting the eyes, retiring to a quiet 
 place, etc. The external sensory impressions, indeed, influence the whole metabolism. Strumpell 
 describes the case of a boy whose sensory inlets were all paralyzed except one eye and one ear, and 
 when these inlets were closed the boy fell asleep, showing how intimately the waking condition is 
 bound up with sensory afferent impulses reaching the cerebral centres.] 
 
 [Hypnotics, such as opium, morphia, KBr, chloral, are drugs which induce sleep.] 
 
 Hypnotism, or Animal Magnetism. — [Most important observations on this subject were made 
 by Braid of Manchester, and many of the recent re-discoveries of Weinhold, Heidenhain, and 
 others confirm Braid's results.] Heidenhain assumes that the cause of this condition is due to an 
 inhibition of the ganglionic cells of the cerebrum, produced by continuous feeble stimulation of the 
 face (slightly stroking the skin or electrical applications), or of the optic nerve (as by gazing steadily 
 at a small, brilliant object), or of the auditory nerve (by uniform sounds) ; while sudden and strong 
 stimulation of the same nerves, especially blowing upon the face, abolishes the condition. Berger 
 [and so did Carpenter and Braid long ago] attributes great importance to the psychological factor, 
 whereby the attention was directed to a particular part of the body. The facility with which differ- 
 ent persons become hypnotic varies very greatly. When the hypnotic condition has been produced 
 a number of times, its subsequent occurrence is facilitated, e.g., by merely pressing upon the brow, 
 by placing the body passively in a certain position, or by stroking the skin. In some people the 
 mere idea of the condition suffices. A hypnotized person is no longer able to open his eyelids 
 when they are pressed together. This is followed by spasm of the apparatus for accommodation in 
 the eye, the range of accommodation is diminished, and there may be deviation of the position of 
 the eyeballs; then follow phenomena of stimulation of the sympathetic in the oblongata; dilatation 
 of the fissure of the eyelids and the pupil, exophthalmos, and increase of the respiration and pulse. 
 At a certain stage there may be a great increase in the sensitiveness of the functions of the sense 
 organs, and also of the muscular sensibility. Afterward there may be analgesia of the part stroked, 
 and loss of taste ; the sense of temperature is lost less readily, and still later that of sight, smell, 
 and hearing. Owing to the abolition or suspension of consciousness, stimuli applied to the sense 
 organs do not produce conscious impressions or perceptions. But stimuli applied tothe sense organs 
 of a hypnotized person cause movements, which, however, are unconscious, although they stimulate 
 voluntary acts. In persons with greatly increased reflex excitability, voluntary movements may ex- 
 cite reflex spasms ; the person may be unable to coSrdinate his organs for speech. 
 
 Types. — According to Griitzner, there are several forms of hypnotism : (i) Passive sleep, where 
 words are still understood, which occurs especially in girls ; (2) owing to the increased reflex ex- 
 citability of the striped muscles certain groups of muscles may be contracted — a condition which 
 may last for days, especially in strong people ; at the same time ataxia may occur, and the muscles 
 may fail to perform their functions (artificial catalepsy). During the stage of lethargy in hyster- 
 ical persons the tendon reflexes are often absent {Charcot and Richer) ; (3) autonomy at call, i. e., 
 the hypnotized person — in most cases the consciousness is still retained — obeys a command, in his 
 condition of light sleep. When the hand is grasped or the head stroked he executes involuntary 
 movements — runs about, dances, rides on a stool, and the like ; (4) hallucinations occur only in 
 some individuals when they waken from a deep sleep, the hallucinations (usually consisting of the 
 sensation of sparks of fire or odors) being very strong and well pronounced; (5) imitation is rare, 
 ordinary movements, such as walking, are easily imitated, the finer movements occur rarely. The 
 " echo speech " is produced by pressure upon the neck, speaking into the throat, or against the 
 abdomen. Pressure over the right eyebrow often ushers in the speech. Color sensation is sus- 
 pended by placing the warm hand on the eye, or by stroking the opposite side of the head (Cohn). 
 Stroking the limbs in the reverse direction gradually removes the rigidity of the limbs and 
 causes the person to waken. Blowing on a part does so at once. Insane persons can be 
 
STRUCTURE OF THE CEREBRUM. 
 
 709 
 
 hypnotized. Disagreeable results follow only when 
 the condition is induced too often and too con- 
 tinuously. 
 
 Hypnotism in Animals. — A hen remains in a 
 fixed position when an object is suddenly placed 
 before its eyes, or when a straw is placed over its 
 beak, or when the head of the animal is pressed 
 on the ground and a chalk line made before its 
 beak (Kircher's expprimentum mirabile, 1644). 
 [Langley has hypnotized a crocodile.] Birds, 
 rabbits, and frogs remain passive for a time after 
 they have been gently stroked on the back for a 
 time. Crayfish stand on their head and claws 
 (Czermak). 
 
 375. STRUCTURE OF THE CERE- 
 BRUM—MOTOR CORTICAL CEN- 
 TRES.— [Cerebral Convolution.— A vertical 
 section of a cerebral convolution consists of a thin 
 layer of gray matter externally inclosing a white core 
 (Fig. 423). The cortex consists of cells embedded 
 in a matrix, and to these proceed nerve fibres from 
 the white matter. The cells of the cortex vary 
 in size, form, and distribution in the different 
 layers and also in different convolutions. Taking 
 such a convolution as the ascending frontal we 
 get the appearances shown in Fig. 422. It is cov- 
 ered on its surface by the pia mater. (1) The 
 most superficial layer is narrow, and consists of 
 much neuroglia, a network of branched nerve 
 fibrils, and a few scattered small multipolar nerve 
 cells; (2) a layer of close-set small pyramidal 
 nerve cells ; (3) the thickest layer or formation of 
 the cornu ammonis, consisting of several layers 
 of large pyramidal cells, which are larger in the 
 deeper than in the more superficial layers. Each 
 cell is more or less pyramidal in shape, giving off 
 several processes — (a) an apical process, which is 
 often very long, and runs toward the surface of 
 the cerebrum, where it is said to terminate in an 
 ovoid corpuscle, closely resembling those in which 
 the ultimate branches of Purkinje's cells of the cere- 
 bellum end ; (i) the unbranched median basilar 
 process, which is an axial cylinder process, and 
 becomes continuous with the axial cylinder of a 
 nerve fibre of the white matter. It ultimately 
 becomes invested by myelin, [c ) The lateral pro- 
 cesses are given off chiefly near the base of the 
 cell, and they soon branch to form part of the 
 ground plexus of fibrils which everywhere per- 
 vades the gray matter. At the lowest part of this 
 layer the cells are larger than elsewhere, present- 
 ing some resemblance to the cells of the anterior 
 cornu of the gray matter of the spinal cord. Bv 
 some it is described as a special layer, and termed 
 the ganglion cell layer. This layer is specially 
 well marked in those convolutions which are de- 
 scribed as containing motor centres. Among the 
 large cells are a few small angular-looking cells, 
 which become more numerous lower down, and 
 form (4) a narrow layer of numerous small branched, 
 irregular, ganglionic cells — the " granular forma- 
 tion " of Meynert. (5) A layer of spindle-shaped 
 fusiform branched cells — the claustral formation 
 of Meynert — lying for the most part parallel to 
 the surface of the convolution. No layer is com- 
 posed exclusively of one form of cell. The above 
 represents the motor type. Then follows the white 
 
 Vertical section of the 3d cerebral convolution (man). 
 1, superficial layer; 2, layer of smallpyramidalcMls; 
 3, layer of large pyramidal corpuscles ; 4, granule 
 layer; 5, layer of fusiform corpuscles; m, white matter. 
 
710 
 
 BLOOD VESSELS OF THE CEREBRUM. 
 
 matter (w\ consisting of medullated nerve fibres, which run in groups into the gray matter, where 
 they lose their myelin. The fibres are somewhat smaller than in the other parts of the nervous 
 system (diameter y^^ inch), and between them lie a few nuclear elements. Each cell is sur- 
 rounded by a lymph space, as in those of the cord.] 
 
 [Recent Results. — Exner finds that after prolonged immersion of the cerebrum in I per cent, 
 osmic acid and subsequent staining with ammoniacal carmine, that what has hitherto been described 
 as " ground substance " in the gray matter really consists of well-formed medullated fibres. 
 The first layer contains many medullated nerve fibres differing in thickness and direction. In the 
 new-born child none are medullated. Similar fibres exist in the second layer, while in the third 
 they are in groups, and very numerous in the fourth. The nerve fibres do not seem to divide in 
 the cortex, and Exner suggests that some of them serve to connect the different layers in the cortex. 
 Fuchs finds that there are no medullated fibre* either in the cortex or medulla until the end of the first 
 month of life. The medullated fibres appear in the uppermost layer at the fifth month, and in the 
 second at the end of the first year, the radial bundles in the deeper layers at the second month. The 
 medullated fibres increase until the seventh or eighth year, when they have the same arrangement 
 as in the adult.] 
 
 [Variations. — Although the above description indicates the typical arrangement in the motor area, 
 
 i, i, medullary arteries ; and i', i', in groups between the convolutions ; 2, 2, arteries of the cortex cerebri ; a, large 
 meshed plexus in first layer; b, closer plexus in middle layer ; c, opener plexus in the gray matter next the white 
 substance, with its vessels (if). 
 
 still, the gray matter differs in different parts of the brain. In the gray matter of the cornu ammonis 
 the large pyramidal cells of (3) make up the chief mass; in the claustrum (4) is most abundant. In 
 the central convolutions (ascending frontal and parietal), according to Betz, Mierzejewski and 
 Bevan Lewis, very large pyramidal cells are found in the lower part of the third layer. Similar cells 
 have been found in the posterior extremities of the frontal convolutions in some animals, the posterior 
 parietal lobule, and paracentral lobule, all of which have motor functions. In those convolu- 
 tions which are regarded as subserving sensory functions, a somewhat different type prevails, e.g., 
 the occipital gyri or annectant convolutions (B. Lewis). The very large pyramidal cells are absent, 
 while the granule layer exists as a well-marked layer between the layer of large pyramidal cells 
 and the ganglion cell layer.] 
 
 Blood Vessels. — The gray matter is much more vascular than the white, and when injected a 
 section of a convolution presents the appearance shown in Fig. 423. The nutritive arteries con- 
 sist of — (a) the long medullary arteries (1), which pass from the pia mater through the gray 
 matter into the central white matter or centrum ovale. They are terminal arteries, and do not 
 communicate with each other in their course; they thus supply independent vascular areas, nor do 
 they anastomose with any of the arteries derived from the ganglionic system of blood vessels: 12 to 
 
CONVOLUTIONS OF THE CEREBRUM. 
 
 711 
 
 15 of them are seen in a section of a convolution, (i) The short cortical nutritive arteries (2) are 
 smaller and shorter than the foregoing. Although some of them enter the white matter, they chiefly 
 supply the cortex, where they form an open meshed plexus in the first layer {a), while in the next 
 layer (6) the plexus of capillaries is dense, the plexus again being wider in the inner layers (f).] 
 
 [Central or Ganglionic Arteries. — From the trunks constituting the circle of Willis (Fig. in 
 \ 381), branches are given off, which pass upward and enter the brain to supply the basal ganglia 
 with blood. They are arranged in several groups, but they are all terminal, each one supplying 
 its own area, nor do they anastomose with the arteries of the cortex.] 
 
 Cerebral Arteries. — From a practical point of view, the distribution of the blood vessels of the 
 brain is important. The artery of the Sylvian fissure supplies the motor areas of the brain in 
 animals; in man, the precentral lobule is supplied by a branch of the anterior cerebral artery 
 {JDuret). The region of the third left frontal convolution, which is connected with the function of 
 speech, is supplied by a special branch of the Sylvian artery. Those areas of the frontal lobes 
 
 Fig. 424. 
 
 Lett side of the human brain (diagrammatic). F, frontal : P, parietal ; O, occipital ; T, temporo-sphenoidal lobe ; 
 S, fissure of Sylvius : S', horizontal, S", ascending ramus of S ; c, sulcus centralis, or fissure of Rolando ; A, 
 ascending frontal, and B, ascending parietal convolution ; F lt superior, F 2 , middle, and F 3 , inferior frontal convo- 
 lutions : /i, superior, and f^ t inferior frontal fissures ; f 3 , sulcus praecentralis ; P, superior parietal lobule; P aj 
 inferior parietal lobule, consisting of P s , supramarginal gyrus, and P a ', angular gyrus ; ifi, sulcus interparietalis ; 
 cm, termination of calloso-marginal fissure; O n firet, O^, second, ? , third occipital convolutions ; po, parieto- 
 occipital fissure ; 0, transverse-occipital fissure ; o 3> inferior longitudinal occipital fissure ; T lt firet, T 2 , second, 
 T 3 , temporo-sphenoidal convolutions ; r t , first, r 3 , second temporo-sphenoidal fissures. 
 
 whose injury results in disturbance of the intelligence (Ferrier) are supplied by the anterior cerebral 
 artery. Those regions of the cortex cerebri whose injury, according to Ferrier, causes hemianaes- 
 thesia are supplied by the posterior cerebral artery. 
 
 [In connection with the localization of the centres in the cortex, it is important to be thoroughly 
 acquainted with the arrangement of the cerebral convolutions. Each half of the outer cerebral 
 surface is divided by certain fissures into five lobes — frontal,, parietal, occipital, temporo- 
 sphenoidal and central, or island of Reil (Fig. 424). The frontal lobe (Fig. 424) consists of 
 three convolutions, with numerous secondary folds running nearly horizontal, named superior (Fj), 
 middle (F 2 ) and inferior (F 3 ) frontal convolutions. Behind these is a large convolution, the ascending 
 frontal (A), which ascends almost vertically, immediately behind these, separated from them, how- 
 ever, by the precentral fissure (/ 8 ), and mapped off behind by the fissure ot Rolando, or the central 
 sulcus (<:).] 
 
712 
 
 CONVOLUTIONS OF THE CEREBRUM. 
 
 [The parietal lobe (Fig. 424, P) is limited in front by the fissure of Rolando, below, in part by 
 the Sylvian fissure, and behind by the parieto-occipital fissure. It consists of the ascending parietal 
 (posterior central) convolution (Fig. 424, B), which ascends just behind the fissure of Rolando, and 
 parallel to the ascending frontal, with which it is continuous below ; above it becomes continuous 
 with the superior parietal lobule (Pj), while the latter is separated from the inferior parietal lobule 
 (pli courbe) by the interparietal sulcus. The inferior parietal lobule consists of (a) a part arching 
 over the upper end of the Sylvian fissure, the supramarginal convolution (P 2 ), which is continuous 
 with the superior temporo-sphenoidal convolution. Behind is (b) the angular gyrus (P 2 a ), which 
 arches round the posterior end of the parallel fissure, and becomes connected with the middle 
 temporo-sphenoidal convolution.] 
 
 [The temporo-sphenoidal lobe (Fig. 424, T) consists of three horizontal convolutions — supe- 
 rior, middle and inferior — the two former being separated by the parallel sulcus, while the whole 
 lobe is mapped off from the frontal by the Sylvian fissure (S).] 
 
 [The occipital lobe (Fig. 424, O) is small, forms the rounded posterior end of the cerebrum, 
 and is separated from the parietal lobe by the parieto-occipital fissure, which fissure is bridged over 
 at the lower part by the four annectant gyri (pit's de passage of Gratiolet). It has three convolu- 
 tions — superior (Oj), middle (0 2 ) and inferior (0 3 ) — on its outer surface.] 
 
 [The central lobe, or island of Reil, consists of five or six short, straight convolutions (gyri 
 
 Fig. 425. 
 
 Median aspect of the right hemisphere. CC, corpus callosum divided longitudinally ; Gf, gyrus fornicatus ; H, 
 gyrus hippocampi ; k, sulcus hippocampi : U, uncinate gyrus ; cm, calloso-margihal fissure ; F, first frontal con- 
 volution ; c, terminal portion of fissure of Rolando ; A, ascending frontal ; E, ascending parietal convolution and 
 paracentral lobule ; Pi', praecuneus or quadrate lobule ; Oz, cuneus ; Po, parieto-occipital fissure; o lt transverse 
 occipital fissure ; oc, calcarine fissure ; oc* ', superior, oc", inferior ramus of the same : D, gyrus descendens ; T 4I 
 gyrus occipito-temporalis lateralis (lobulus fusiformis) ; T 6 , gyrus occipito-temporalis medialis (lobulus lingualis). 
 
 operti — Fig. 426) radiating outward and backward from near the anterior perforated spot, and can 
 only be seen when the margins of the Sylvian fissure are pulled asunder. The operculum, con- 
 sisting of the extremities of the inferior frontal, ascending parietal and frontal convolutions, lie out- 
 side it, cover it, and conceal it from view.] 
 
 [On the inner or mesial surface of the cerebrum are — the gyrus fornicatus (Fig. 425, Gf ), or 
 convolution of the corpus callosum, which runs parallel to and bends round the anterior and poste- 
 rior extremities of the corpus callosum, terminating posteriorly in the gyrus uncinatus or gyrus 
 hippocampi (Fig. 425, H), and ending anteriorly in a crooked extremity, the subiculum cornu am- 
 monis (Fig. 425, U). Above it is the calloso marginal fissure (Fig. 425, cm), and running parallel 
 to it is the marginal convolution (Fig. 425), which lies between the latter fissure and the margin 
 of the longitudinal fissure; it is, however, merely the mesial aspect of the frontal and parietal con- 
 volutions. The quadrate lobule or praecuneus lies (Fig. 425, Pi) between the posterior extrem- 
 ity of the calloso-marginal fissure and the parieto-occipital fissure ; it is merely the mesial aspect of 
 the ascending parietal convolution. The parieto-occipital fissure terminates below in the calcarine 
 fissure (Fig. 425, oc), and the latter runs backward in the occipital lobe, dividing it into two 
 branches, oc', oc". Between the parieto-occipital and calcarine fissures lies the wedge-shaped 
 lobule termed the cuneus (Fig. 425, oz). The calcarine fissure indicates on the surface the position 
 of the calcar avis or hippocampus minor, in the posterior cornu of the lateral ventricle. The 
 
CONDITIONS AFFECTING THE MOTOR CENTRES. 
 
 713 
 
 dentate fissure or sulcus hippocampi (Fig. 425, h), marks the position of the elevation of the 
 hippocampus major, or cornu ammonis, in the lateral ventricle. The temporo-sphenofdal lobe 
 terminates anteriorly in the uncinate gyrus, while, running along the former and the occipital 
 lobes is the collateral fissure (occipitotemporal sulcus), which marks the position of the emenentia 
 collateralis in the descending cornu of the lateral ventricle, while it also separates the superior from 
 the inferior temporo-occipital convolutions (T 4 and T 5 ).] 
 
 Motor Centres. — Fritsch and Hitzig (1870) discovered a series of circum- 
 scribed regions on the surface of the cerebral 
 
 convolutions, whose stimulation by means of Fig. 426. 
 
 electricity causes coordinated movements in 
 quite distinct groups of muscles of the opposite 
 side of the body (Fig. 428, I, II). 
 
 Methods — Stimulation. — The surface of the cere- 
 brum is exposed in an animal (dog, monkey) by remov- 
 ing a part of the skull covering the so-called motor con- 
 volutions and dividing the dura mater. When the con- 
 volutions are fully exposed, a pair of blunt, non-polariz- 
 able (£ 328) needle electrodes are applied near each 
 other to various parts of the cerebral surface. We may 
 employ the closing or opening shock of a constant 
 current, or the constant current may be rapidly inter- 
 rupted, the current being of such a strength as to be 
 distinctly perceived when it is applied to the tip of the 
 tongue {Fritsch and Hitzig). Or the induced current 
 may be used (Ferrier, i8y?) of such a strength that it 
 is readily felt when applied to the tip of the tongue. 
 The cerebrum is completely insensible to severe opera- 
 tions made upon it. 
 
 The areas of the cerebral cortex, whose 
 stimulation discharges the characteristic move- 
 ments, are regarded as actual centres, because 
 the reaction time after stimulation of the 
 centres and the duration of the muscular con- 
 traction are longer than when the Subcortical Orbital surface of the left frontal lobe and the 
 
 fibres which lead toward the deeper parts of isl ?? d , ? f K Rei1 ' the i 1 ? of . the "emporo-sphe- 
 
 ... -ill,- noidal lobe removed to show the latter. 17, 
 
 the brain are Stimulated. Another CirCUm- convolution of the margin of the longitudinal 
 
 stance favoring this view is that the excitabil- 
 ity of these areas is influenced by the stimu- 
 lation of afferent nerves (Bubnoff and Hei- 
 denhain). It may be that these centres are 
 acted upon by voluntary impulses in the exe- 
 cution of voluntary movements. Hence, they have been called "psychomotor 
 centres." The motor areas of the cerebrum (dog, cat, sheep) are characterized 
 by the presence of specially large pyramidal cells (Beiz, Merzejewsky, Bevan, 
 Lewis) ; while similar cells were found by Obersteiner in the areas marked 4 and 
 8 (Fig. 428), and Betz found them in the ascending frontal convolution of man, 
 in the third frontal convolution, and in the island of Reil. O. Saltmann found 
 that stimulation of the motor areas in newly-born animals is without result, 
 while only the deeper fibres of the corona radiata are excitable. 
 
 Modifying Conditions. — In the condition of deep narcosis produced by chloroform, ether, 
 chloral, morphia, or in apncea, the excitability of the centres is abolished (Schiff), whilst the sub- 
 cortical conducting paths still retain their excitability {Bubnoff and Heidenhain). Small doses of 
 these poisons and also of atropin at first increase the excitability of the centres. Moderate loss of 
 blood excites them, while a great loss of blood diminishes and then abolishes the excitability (Muni 
 and Orschansky). Slight inflammation increases, while cooling diminishes, the excitability. If the 
 cortex cerebri be removed in animals, the excitability of the fibres of the corona radiata is com- 
 pletely abolished about the fourth day, just as in the case of a peripheral nerve separated from its 
 centre (Albertoni, Michieli, Dupuy, Franck, and Pilres). 
 
 fissure ; O, olfactory fissure, with the olfactory 
 lobe removed ; T R, triradiate fissure; i" and 
 1'", convolutions on the orbital surface; I, I, 
 i, 1, under surface of the infero-frontal convo- 
 lution ; 4, under surface of the ascending 
 frontal, and 5, of the ascending parietal con- 
 volutions ; C, central lobe or island. 
 
714 
 
 COiNJJITIONS AFFECTING THE MOTOR CENTRES. 
 
 Stimulation of Subcortical Parts. — As the fibres of the corona radiata converge toward the 
 centre of the hemisphere, it is evident that, after removal of the cortex, stimulation of these fibres in 
 the deeper parts of the hemisphere is followed by the same motor resalts (Gli&y and. jEe&Aard). 
 The stimulus is applied merely to a deeper part of the motor path. If the stimulus be applied to 
 pirts situated still more deeply, as, for example, to the internal capsule, general contraction of the 
 muscles on the opposite side is the result. 
 
 Time Relations of the Stimulation. — According to Franck and Pitres, the time which elapses 
 between the moment of stimulation of the cortex and the resulting movement, after deducting the 
 period of latent stimulation for the muscles and the time necessary for the conduction of the impulse 
 through the cord and nerves of the extremities, is 0.045 second. Heidenhain and Bubnoff found 
 that, during moderate morphia-narcosis, when the stimulating current was increased in strength, the 
 muscular contraction and the reaction time became shorter. After removal of the cortex, the occur- 
 rence of the muscular contraction from the moment of stimulation of the white matter is diminished 
 
 Fig. 427. 
 
 View of the brain from above (semi-diagrammatic). S,, end of ramus of the Sylvian fissure. 
 
 to the same parts as in Fig. 424. 
 
 The other letters refer 
 
 ]^ to y£. The form of the muscular contraction is longer and more extended when the cortex, 
 than when the subcortical, paths are stimulated. If the animal (dog) be in a state of high reflex 
 excitability these differences disappear; in both cases the contraction follows very rapidly {Bubnoff 
 and Heidenhain). If the stimulus be very strong, the muscles of the same side may contract, but 
 somewhat later than those of the opposite side. If the motor areas for the fore and hind limbs be 
 stimulated simultaneously, the latter contract somewhat after the former. 
 
 Number of Stimuli. — If 40 stimuli per second be applied to a motor area, then the corresponding 
 muscles yield 40 single contractions ; while with 46 single stimuli per second there results a continued 
 complete contraction {Franck and Pitres). In one and the same animal the same number of stimuli 
 is required to produce a continuous contraction, whether the cortical centre, the motor nerve, or even 
 the muscle itself be stimulated. With very feeble stimuli summation of stimuli takes place, for 
 the muscular contraction only begins after several ineffective stimuli have been applied. [It is gen- 
 erally held that the rhythm of a contracting muscle is the same as the rhythm of the stimuli applied 
 
EFFECT OF STIMULI ON THE MOTOR FIBRES. 715 
 
 to its motor nerve, but Schafer and Horsley contend that this holds good for rates of stimuli to 
 about 10 or 12 per second. They find that the same is true for the cortex cerebri, corona radiata, 
 and medulla- spinalis, viz., that the muscular response does not vary with the rhythm (». e., number 
 of stimuli per sec), but that the rhythm is constant — about 10 per sec. — and independent of the 
 number of stimuli per sec, provided they are above 10 per sec. applied to these parts. Indeed, all 
 voluntary contractions show a similar rate of undulation in the muscle curve. Perhaps the rhythm 
 of the efferent impulses is modified in the motor nerve cells of the spinal cord.] 
 
 [The matter, as regards electrical stimulation of the cortex cerebri, resolves it- 
 self into this, that stimulation of certain cortical areas always causes contraction 
 in definite muscles or groups of muscles, resulting in definite coordinated move- 
 ments on the opposite side of the body; the areas have been called "motor 
 areas." They have been mapped out and ascertained in a large number of 
 animals, and the question comes to be, Are there similar areas in man ?] 
 
 Primary Fissures and Convolutions of the Dog's Brain. — The position of the motor centres 
 in the dog's brain is indicated in Fig. 428, I and II. The dog's brain is marked by two " primary 
 fissures," viz., the sulcus cruciatus (Leurei) (S), which intersects the longitudinal fissure at a right 
 angle at the junction of its anterior with its middle third. This fissure has been called the sulcus 
 frontalis (Owen), or the fissura coronalis. The second primary fissure is the fossa Sylvii (F). Four 
 " primary convolutions," in addition, are arranged with reference to these primary fissures. The 
 first primary convolution (I), in the form of a sharply-curved knee, embraces the fossa Sylvii (F). 
 The second convolution (II) runs nearly parallel to the first. The fourth primary convolution (IV) 
 bounds the longitudinal fissure, and is separated from its fellow of the opposite side by the falx 
 cerebri; anteriorly it embraces the sulcus cruciatus (S), so that it is divided into two parts by this 
 sulcus, a part, the gyrus prsecruciatus orpraefrontalis, lying in front of the sulcus, and the gyrus postcru- 
 ciatus (postfrontalis) lying behind it. The third primary convolution (HI) runs parallel to the 
 fourth. Some authors count the convolutions from the longitudinal fissure outward. In Fig. 428, I 
 and II, the motor areas or centres are indicated by dots in the individual primary convolutions. We 
 must remember, however, that the centres are not mere points, but that they vary in size from that 
 of a pea upward, according to the size of the animal. Motor areas have been mapped out in the 
 brain of the monkey, rabbit, rat, bird, and frog. 
 
 Position of the Motor Centres (Dog). — Fritsch and Hitzig, in 1870, mapped out the follow- 
 ing motor areas, whose position may be readily found on referring to Fig. 428 : I is the centre for 
 the muscles of the neck ; 2, for the extensors and adductors of the /ore limb ; 3, for the flexion and 
 rotation of the fore leg ; 4, for the movements of the kind limb, which Luciani and Tamburini re- 
 solved into two antagonistic centres; 5, for the muscles of the face, or the facial centre. In 1873 
 Ferrier discovered the following additional centres : 6, for the lateral switching movements of the 
 tail; 7, for the retraction and abduction of the fore limb ; 8, for the elevation of the shoulder and 
 extension of the fore limb, as in walking ; the area marked 9, 9, 9, controls the movements of the 
 orbicularis palpebrarum, and of the zygomaticus (closure of the eyelids), together with the upward 
 movement of the eyeball and narrowing of the pupil. Stimulation of the areas a, a (Fig. II), is fol- 
 lowed by retraction and elevation of the angle of the mouth, with partial opening of the mouth ; at 
 b, Ferrier observed opening of the mouth with protrusion and retraction of the tongue, while the dog 
 not unfrequently howled. He called this centre the "oral centre." Stimulation of c, c, causes re- 
 traction of the angle of the mouth, owing to the action of the platysma, while c' causes elevation of 
 the angle of the mouth and of one-half of the face, until the eye may be closed, just as in 9. Stim- 
 ulation of d is followed by opening of the eye and dilatation of the pupil, while the eyes and head 
 are turned toward the other side. According to H. Munk, the prefro ntal region has an influence 
 upon the attitude of the body. The perineal muscles contract when the gyrus postcruciatus is stim- 
 ulated. Stimulation of the gyrus prjecruciatus on its anterior and sloping aspect causes movements 
 in the pharynx and larynx. 
 
 The position of the individual motor areas may vary somewhat, and they may 
 be slightly different on the two sides (Luciani and Famburini}. 
 
 Strong Stimuli. — If the stimulation be very strong, not only the muscles on 
 the opposite side contract, but those on the same side may also contract. These 
 latter movements belong to the class of associated movements, and are due to con- 
 duction through commissural fibres. Those muscles, which usually (muscles of 
 mastication) or always (muscle of eye, larynx, and face) act together, appear to 
 have a centre not only in the opposite, but also in the hemisphere of the same side 
 (Exner). [All observers have found that stimulation of the facial centre causes 
 identical (associated) movements on both sides of the face, so that both sides of 
 the face seem to be represented in each hemisphere. Schafer and Horsley's experi- 
 ments make it very probable that some other muscles, e.g., some of the trunk mus- 
 
716 
 
 EFFECT OF STIMULI ON THE MOTOR CENTRES. 
 
 cles, pectorals, and recti abdominis, are represented bilaterally in the hemispheres. 
 This is an important point in relation to recovery after the supposed destruction of 
 a centre, and has an intimate bearing on the question of " Substitution," in refer- 
 ence to the restoration of nerve function.] 
 
 Fig. 428. 
 
 , Cerebrum of the dog from above ; II, from the side; I, II, III, IV, the four primary convolutions, — S, sulcus cru- 
 ciatus: /•, Sylvian fossa; o> olfactory lobe ; p, optic nerve; 1, motor area for the muscles of the neck ; 2, ex- 
 tensors and abductors of the fore limb : 3, flexors and rotators of the fore limb ; 4, the muscles of the hind limb ; 
 5, the facial muscles ; 6. lateral switching movements of the tail; 7, retraction and abduction of the fore limb ; 
 8, elevation of the shoulder and extension of the fore limb (movements as in walking) ; 9, a, orbicularis palpe- 
 brarum, zygomaticus, closure of the eyelids. II, a, a, retraction and elevation of the angle of the mouth; b, 
 opening of the mouth and movements of the oral centre; c, c, platysma; d, opening of the eye; I, r, thermic 
 centre, according to Eulenberg and Landois. Ill, cerebrum of the rabbit from above ; IV, cerebrum of the pig- 
 eon from above ; V, cerebrum of the frog from above ; VI, cerebrum of the carp from above — (in all these is 
 the olfactory lobe ; 1, cerebrum; 2, optic lobe; 3, cerebellum; 4, medulla oblongata). 
 
 Mechanical stimulation has no effect upon these centres. Landois and 
 Eulenberg observed that chemical stimulation of these centres by means of 
 common salt caused movements in the extremities. 
 
CEREBRAL EPILEPSY. 
 
 717 
 
 Cerebral Epilepsy. — It is of great practical diagnostic importance to ascer- 
 tain if stimulation of the motor areas in man, due to local diseases (inflammation, 
 tumors, softening, degenerative irritation), causes movements. [Hughlings- Jack- 
 son has shown that local diseases of the cortex may cause spasmodic contractions 
 in certain groups of muscles, a condition known as " Jacksonian Epilepsy,"] 
 and he explains in this way the occurrence of unilateral local epileptiform spasms, 
 which were observed by Ferrier and Landois to occur after inflammatory irrita- 
 tion. Luciani observed these spasms in dogs, and sometimes they were so violent 
 and general as to constitute an attack of epilepsy. This condition became 
 
 Fig. 429. 
 
 The brain with the chief convolutions (after Ecker). See also Figs. 424-427 in their relation to the skull. The num- 
 bers 1 to 14, and the letters a to d, indicate cortical areas (p. 718). S, Sylvian fissure ; C, central sulcus, or fis- 
 sure of Rolando ; A, anterior, and B, posterior, central convolutions; F„ upper, Fa, middle, and F 3 , lowest 
 frontal convolution ; f l , superior, and./ r 3 , inferior frontal fissure ; f 3 , sulcus praecentrafis ; P, , superior, P 3 , infe- 
 rior parietal lobe, with P s , gyrus supramarginalis ; P 2 J , gyrus angularis ; ip, sulcus interparietals : cm, end of 
 calloso-marginal fissure ; lt 2 , O., occipital convolutions ; po, parieto-occipital fissure; T, , T 2 , T 3 , temporo- 
 sphenoidal convoluf ions ; K,, K a , K 8 , points in the coronal suture ; 4 X , 4 9 , in the lambdoidal suture. 
 
 hereditary, and the animals ultimately died from epilepsy (§ 373). According to 
 Eckhard, epileptic attacks are never produced by stimulation of the surface of 
 the posterior convolutions. 
 
 Strong stimulation of the motor regions may give rise in dogs to a complete general convulsive 
 epileptic attack, which usually begins with contractions of the groups of muscles specially related 
 to the stimulated centre (Ferrier, Eulenberg and Landois, Albertoni, Luciani and Tamburini), 
 then often passes to the corresponding limb of the opposite side (associated movements) ; and, lastly, 
 all the muscles of the body are thrown into tonic and then into clonic spasms. The opposite side 
 of the body has been observed to pass into spasm from below upward, after the contractions were 
 developed in the other side. The spasmodic excitement passes from centre to centre, an interme- 
 
718 
 
 MOTOR CENTRES IN THE MARGINAL CONVOLUTION. 
 
 diate motor region never being passed over. Sometimes feeble stimulation above the internal cap- 
 sule is sufficient to cause this condition. After this condition has once been produced, the slightest 
 stimulation may suffice to bring on a new epileptic attack (§ 373). Stimulation of the subcortical 
 white matter causes epilepsy, which, however, begins in the muscles of the same side (Bubnoff and 
 Heidenhain), These contractions are due to an escape of the electrical current, which thus reaches 
 the medulla oblongata (g 373). If certain motor areas are extirpated, the epileptic attack is absent 
 from the muscles controlled by these areas (Luciani). Separation of the motor cortical area by 
 means of a horizontal section during an attack cuts short the latter (Muni). During an epileptic 
 attack it is possible to excise the motor area of one extremity and thus exclude this limb from the 
 attack while the rest of the body is convulsed. 
 
 Effect of Drugs. — The continued use of potassium bromide prevents the possibility of producing 
 epilepsy on stimulating the cortical areas. Airopin in small doses increases the excitability of the 
 motor areas, while in large doses it paralyzes them. 
 
 [Motor Centres in the Monkey. — Ferrier has mapped out a large number 
 of centres on the outer surface of the brain in the monkey, and to each centre he 
 has given a number. These numbers have been transferred to corresponding con- 
 volutions on the human brain, and numbered accordingly. These convolutions 
 in the monkey occupy the posterior extremities of the posterior and middle 
 frontal convolutions, the ascending frontal, ascending parietal, and part of the 
 parietal lobule.] 
 
 [Fig. 429 represents these areas transferred to the corresponding areas in man. (1) On the 
 superior parietal lobule (advance of the opposite hind limb, as in walking). (2), (3), (4) Around 
 the upper extremity of the fissure of Rolando (complex movements of the opposite leg and arm, 
 and of the trunk, as in swimming), (a), (b), (c), (d), On the ascending parietal or posterior cen- 
 tral convolution (individual and combined movements of the fingers and wrist of the opposite hand 
 or prehensile movements). (J) Posterior end of the superior frontal convolution (extension for- 
 ward of the opposite arm and hand). (6) Upper part of the ascending frontal or anterior central 
 convolution (supination and flexion of the opposite forearm). (7) Middle of the same convolution 
 (retraction and elevation of the opposite angle of the moulh). (8) At the lower end of the same 
 convolution (elevation of the ala nasi and upper lip, and depression of the lower lip on the oppo- 
 site side). (9), (10), Broca's convolution (opening of the mouth with protrusion and retraction of 
 the tongue — aphasic region). (11) Between 10 and the lower end of the ascending parietal con- 
 volution (retraction of the opposite angle of the mouth, the head turns toward one side). (12) 
 Posterior part of the superior and middle frontal convolutions (the eyes open widely, the pupils 
 dilate, and the head and eyes turn toward the opposite side). (13), (13') Supramarginal and 
 angular gyrus (the eyes move toward the opposite side, and upward or downward — centre of- 
 vision). (14) Superior temporo-sphenoidal convolution (pricking of the opposite ear, pupils dilate, 
 and the head and eyes turn to the opposite side — hearing centre).] 
 
 [Schafer and Horsley have extended Ferrier' s researches, and shown that motor 
 centres exist in the marginal convolution (Fig. 430), which is excitable only 
 
 in that portion which corresponds in 
 
 Fig. 430. 
 
 extent (antero-posteriorly) with the ex- 
 citable portion of the outer surface of 
 the hemisphere. Anteriorly it reaches 
 forward to a line which is opposite the 
 junction of the posterior and middle 
 thirds of the superior frontal convolu- 
 tion (centre 12), while posteriorly it 
 extends backward to opposite the pari- 
 etal lobule, including the paracentral 
 lobule, which contains large multipolar 
 pyramidal motor cells. The rest of the 
 mesial surface is excitable. They find 
 that the centres are arranged from before 
 backward in the following order : the 
 motor region of the elbow and shoulder, 
 then follow centres for the trunk muscles, 
 such as give rise to arching of the trunk 
 in the dorsal and lumbar regions ; also flexion (ilio-psoas muscle) and extension 
 
 Inner surface of right hemisphere. AS, area governing 
 the movements of the arm and shoulder ; Tr, of 
 the trunk; leg, those of the leg; Gf, gyrus forni- 
 catus ; CC, corpus callosum ; u, uncinate gyrus ; 
 O, occipital lobe. 
 
DESTRUCTION OF MOTOR CENTRES. 719 
 
 (glutei) of the hip ; hamstring and extensors of the knee ; movements of the 
 ankle and digits. The centre for the thigh muscles is in the paracentral lobule.] 
 
 [Excitation of the Area AS produces movements of the arm. These vary according to the spot 
 stimulated, but toward the anterior part of the area, movements of the wrist and fore arm, toward 
 the posterior part movements of the arm and shoulder, are more frequently the result of the exci- 
 tation. Excitation of Tr produces movements of the trunk, generally arching and rotation. Those 
 movements which are called forth by stimulating the anterior part of the area are u-ually confined 
 to the upper part of the trunk (thoracic region), and are often associated with movements of the 
 shoulder and arm ; those called forth by stimulating the posterior part are movements of the ab- 
 dominal and pelvic regions and of the tail, and are often associated with movements of the hip and 
 leg. Excitation of the area L. produces movements in the lower limb. These vary according to 
 the part stimulated, extension of the hip being especially associated with excitation of the anterior 
 part of the area, and contraction of the hamstrings with excitation of the middle part.] 
 
 [Do similar Centres exist in Man ? — The results of clinical and patholog- 
 ical investigations show that similar, although not absolutely identical, areas exist 
 in man. The motor areas, or those 
 
 which have a special relation to volun- FlG - 43 1 - 
 
 tary motion in man, occupy the"cen- ~ 
 
 tral" convolutions, *. e., the ascending 
 frontal and ascending parietal convo- 
 lutions along with the superior parietal 
 lobule, and along the mesial surface of 
 the hemisphere the paracentral lobule 
 and precuneus (Fig. 431). In this 
 region the upper third of the ascend- 
 ing frontal and parietal convolutions 
 along with the superior parietal being 
 the leg area (Fig. 431, leg), the mid- 
 dle third of the ascending parietal and 
 
 ascending parietal for the arm, and the Motor areas in man shaded— outer surface of the left side of 
 Upper part Of the lowest third of these humMbram^ Dotted area, the aphasic region (modified 
 
 convolutions for the face, while the 
 
 very lowest part of the ascending frontal convolution is the area for the move- 
 ments of the lips (L) and tongue (T), (compare Fig. 433). The last area, with 
 the posterior extremity of the third left frontal convolution, is the centre for 
 voluntary speech. We cannot say whether these " centres " are sharply mapped 
 off from each other. In any case a very strong stimulation of one centre may in- 
 volve an adjacent area. So far as is yet known, centres Nos. 5 and 12, as repre- 
 sented on the monkey's brain — those on the posterior extremity of the superior 
 and middle frontal convolutions — (5) for extension forward of the arm and hand, 
 and (12) for opening the eyes and turning the head toward the opposite side (as 
 in surprise) are not represented in the human brain.] 
 
 [Gowers maintains that this region is not exclusively motor, but that destruction of these parts 
 also leads to some loss of sensation. Starr also asserts that perceptions occur in the gray matter of 
 the cortex of the " central " region and parietal convolutions, and that the various sensory areas for 
 the various parts of the body lie about and coincide to some extent with the motor various areas for 
 similar parts, but the sensory area is more extensive than the motor area, extending into the parietal 
 behind the motor area, which is confined to the ascending frontal and parietal convolutions.] 
 
 [II. Method of Destruction of Parts of the Cortex. — Much confusion in this matter has 
 arisen from comparing the results obtained on animals of different species. It seems quite certain 
 that the results obtained in the dog are quite different from those in the monkey. The motor areas 
 may be simply excised with a knife, or the surface of the brain may be washed away with a stream 
 of water, as was done by Goltz in dogs.] 
 
 [In the dog the areas which are described as motor may be removed either by the knife (Her- 
 mann), or by means of a stream of water so directed as to wash away the gray matter. In both 
 cases, although there was some paralysis on the opposite side of the body, this was but temporary, 
 for the paralysis disappeared within a few days, the animals having very decided control over their 
 muscles, although Goltz admits that certain acts, especially those which the dogs had been trained 
 to execute, c. g., giving a paw, were executed " clumsily," indicating some failure of complete con- 
 
720 EXTIRPATION OF THE MOTOR CENTRES. 
 
 trol, which Goltz ascribed to loss of tactile sensibility. Goltz thinks that the extent of the injury has 
 more to do with the result than the locality. The restoration of motion was not due to the action 
 of the corresponding centre of the opposite side, as destruction of this centre, although it produced 
 the usual symptoms on the side which it governed, had no effect on the previous result ( Carville 
 and Duret).] 
 
 [In the monkey there can be no doubt, from the experiments of Ferrier, that 
 destruction of a motor centre, e. g., that for the arm, results in permanent ^ pa- 
 ralysis of the arm of the opposite side, and if the centres for the arm and leg are 
 destroyed there is permanent hemiplegia of the opposite side. Indeed, Schafer 
 and Horsley have removed the motor centres on the outer surface of the hemi- 
 spheres and those for the trunk muscles in the marginal convolution, and they find 
 that the result is absolute hemiplegia.] 
 
 [In man records of destructive lesions of the motor areas in whole or part have 
 now accumulated to such an extent as to leave no doubt, that if there be say a de- 
 structive lesion of the middle third of the cortex of the ascending frontal and 
 ascending parietal convolutions, there will be paralysis of the arm of the opposite 
 side, and the same is true for the other centres.] 
 
 [In extirpation of the motor centres much confusion has arisen from com- 
 paring the results obtained on different animals. In the dog there is no permanent 
 motor paralysis, in the monkey and man there is. The difference is this, that in 
 the dog the lower centres, perhaps the basal ganglia, are able to subserve the exe- 
 cution of those coordinated movements required for standing, progression, etc. 
 As we proceed higher in the animal scale, the motor cortical centres assume more 
 and more of the functions subserved by the basal ganglia in lower animals. There 
 is, as it were, a gradual displacement of motor centres to the cortical region as we 
 ascend in the zoological scale.] 
 
 Differences in Animals. — The higher the development of the intelligence of the animals the 
 more their movements have been learned, and have gradually come to be controlled by the will ; 
 in them the disturbance of the motor phenomena becomes more pronounced and persistent after 
 destruction of the cortical psychomotor centres. While in the lower vertebrates, including the 
 birds, extirpation of the whole hemispheres does not materially interfere with the movements, the 
 coordinated reflex movements being sufficient ; in dogs occasionally, but exceptionally, extirpation 
 of sexeral motor areas produces visible permanent disturbance of motor acts, while in monkeys 
 and man ($ 378) the paralytic phenomena may be intense and persistent. 
 
 Acquired Movements. — Among the movements performed by men are many which have been 
 acquired after much practice, and have been subjected to voluntary control, e.g., the movements of 
 the hands for many manual occupations. After a lesion of the psychomotor centres, such move- 
 ments are reacquired only very slowly and incompletely, or it may be not at all. [The interference 
 with these finer acquired movements sometimes becomes very marked in lesions of the motor areas 
 produced by hemorrhage, and in some cases of hemiplegia.] Those movements, however, which 
 are, as it were, innate [or, as they are sometimes termed, fundamental in opposition to acquired], 
 and are under the control of the will without much practice — such as the associated movements of 
 the eyes, face, some of those of the limbs — are either rapidly restored after the lesion, or they ap- 
 pear to suffer but slightly. After a lesion of the cerebral cortex, the facial muscles are never so 
 completely paralyzed as from a lesion of the trunk of the facial nerve ; usually the eye can be 
 closed in the former case. The movements necessary for sucking have been performed by a hemi- 
 cephalic infant. 
 
 Theoretical. — Hitzig ascribes the disturbance of movement, after the removal of the motor 
 centres, to the loss of the " muscular sensibility." Schiff ascribes it to the loss of tactile sensibility. 
 According to Ferrier, the tactile and sensory impressions are not appreciably diminished or altered. 
 The descending degeneration of the pyramidal tracts in the lateral columns, according to Schiff, 
 occurs after section of the posterior half of the cervical spinal cord, or even after section of the pos- 
 terior part of the lateral columns. After dividing the latter, and allowing secondary degeneration 
 to take place, it is not possible to discharge movements by stimulating the cortex cerebri. [Schiff 
 divided the posterior column of the cord, and found that stimulation of the opposite motor cortex 
 failed to excite movements in the opposite fore limbs. He supposed that this result was due to as- 
 cending degeneration. Horsley finds, however, that Schiff's results are due to transverse aseptic 
 myelitis at the seat of operation, and causing a " block" there in the motor tract.] The posterior 
 columns and their continuation upward to the brain are supposed- to carry the impulses upward to 
 the cerebrum (ascending limb of the reflex arc), where, after being modified in the centres, they are 
 carried outward by the pyramidal tracts (descending limb of the reflex arc). [Some hold that the 
 posterior columns are directly connected with the cortical motor area, while others think that a 
 
THE SENSORY CORTICAL CENTRES. 721 
 
 sensory perceptive centre is interposed between the afferent and efferent impulses.] Between, but 
 deeper in the brain, lie the centres for tactile sensibility. Landois and Eulenberg observed in * 
 dog, from which the motor centres for the extremities had been removed on both sides, that the move- 
 ments became completely ataxic, i. e., the animal could not execute such coSrdinated movements 
 as walking, standing, etc. Goltz regards the disturbances of movement after injury of the cortex 
 as due to inhibition. Schiff maintains that when the cortex cerebri is stimulated we do not stimu- 
 late a cortical centre, but only the sensory channels of a reflex arc, the continuation of the posterior 
 columns, so that on this supposition the movements resulting from stimulation of the motor points 
 would be reflex movements. The centres lie deeper in the brain. This view is not generally en- 
 tertained. 
 
 Modifying Conditions. — The excitability of the motor centres is capable of 
 being considerably modified. Stimulation of sensory nerves diminishes it ; thus 
 the curve of contraction of the muscles becomes lower and longer, while the re- 
 action time is lengthened simultaneously. Only when, owing to strong stimula- 
 tion, the reflex muscular contractions are vigorous, the excitability of the cortical 
 centres appears to be increased. Specially noteworthy is the fact that, in a cer- 
 tain stage of morphia-narcosis, a stimulus which is too feeble to discharge a 
 contraction becomes effective at once, if immediately before the stimulus is applied 
 to the cortical centre the skin of certain cutaneous areas be subjected to gentle 
 tactile stimulation. When strong pressure is applied to the foot the contractions 
 become tonic in their nature, so that all stimuli, which under normal conditions 
 produce only temporary stimulation, now stimulate these centres continuously. 
 If during the tonic contraction one gently strokes the back of the foot, blows on 
 the face, gently taps the nose or stimulates the sciatic nerve, suddenly relaxation 
 of the muscles again occurs. These phenomena call to mind the analogous ob- 
 servations in hypnotized animals (§ 374). Another very remarkable observation 
 is that, when either owing to a reflex effect, or owing to strong electrical stimula- 
 tion of a cortical centre, contracture of the corresponding muscles is produced, 
 then feeble stimulation of the same centre, but also of other centres, suppresses 
 movement. Thus we have the remarkable fact that, according to the strength of 
 the stimulus applied to the motor apparatus, we can either produce movement or 
 suppress a movement already in progress (Bubnoff and Heidenhain). 
 
 [Excision of the Thyroid affects the nerve centres. After thyroidectomy (twenty-four hours) 
 the tetanus obtained by stimulating the cortex is greatly changed. It ceases when the stimulating 
 current is shut off as suddenly as that observed on stimulating the corona radiata. In more advanced 
 cases the tetanus is soon exhausted, and is often followed by clonic epileptoid spasms. In the latter 
 stages, after thyroidectomy, there may be only a feeble tetanus, or none at all, on stimulating the 
 motor areas, so great is the state of depression of function ol these centres (J/orsUjr).] 
 
 [Warner has directed ".ttention to visible muscular movements apart from those studied in 
 epilepsy, chorea, athetois — and including attitude, gait, movements of the eyeballs, position of the 
 hand, and posture in general, etc as expressive of states of the brain and nerve centres.] 
 
 376. THE SENSORY CORTICAL CENTRES.— [There must be 
 some connection between the surface of the brain and the afferent channels through 
 which sensory impulses pass inward, and although the channels for sensory 
 impulses are, perhaps, not so definitely localized as those for voluntary motion, 
 still, we know that sensory impulses for the opposite half of the body travel up- 
 ward through the posterior third of the posterior limb of the internal capsule 
 (Fig. 439, S), to radiate, in all probability, into the occipital and temporo-sphe- 
 noidal lobes. Parts of these convolutions are sometimes spoken of as " sensory 
 centres " or " psycho-sensorial " areas.] 
 
 [The same methods have been applied to the investigation of these centres, viz., stimulation and 
 extirpation. Stimulation. — Ferrier found that electrical stimulation of the angular gyrus (monkey) 
 caused movements of the eyeballs toward the side, with sometimes associated movements of the 
 head, but he regarded these as reflex movements, so that for this and other reasons he, in his earliest 
 contributions, regarded the angular gyrus and adjacent parts as the " centre for vision." On stimu- 
 lating the first temporo-sphenoidal convolution, the monkey pricked the opposite ear, the pupils dilated, 
 while the head and ears turned to the opposite side ; it exhibited movements similar to those caused 
 by a loud sound. These movements are also reflex phenomena, so that he located the " auditory 
 46. 
 
722 
 
 THE VISUAL CENTRE. 
 
 centre " in this region, and on somewhat similar grounds. As the result of inferences from the 
 stimulation and extirpation of other parts, he referred the centres for smell and taste to the tip of 
 the temporo-sphenoidal lobe, and touch to the hippocampus major; but all these statements have 
 not been confirmed.] 
 
 [Goltz experimented on dogs by washing away the cortex cerebri, and found that when a 
 sufficient amount of the gray matter is removed, and after recovery from the immediate effects of 
 the operation, there is a peculiar defect of vision and other sensory defects ; but, so far, Goltz has not 
 found that there is any difference in this respect between removal of the anterior and posterior lobes 
 of the dog's brain. The dog is not blind, as it can see and use his eyes to avoid obstacles, but it 
 seemed as if the animal failed to recognize, as such, e.g., food or flesh placed before it, while exhi- 
 bitions which before the operation greatly excited the dog ceased to do so. Goltz caused his servant 
 to dress himself in a mummer's red-colored garb, which greatly excited the dog, but after the opera- 
 tion the dog, although it was not blind, was no longer excited thereby. Nor was it afterward cowed 
 by the appearance of a whip. After a time there was recovery, to a certain extent, if the animal 
 was trained, whether by the deposition of new impressions, or by opening up new channels, or by 
 the partial recovery of some parts of the gray matter not removed, it is impossible to say.] 
 
 [Munk has mapped out the surface of the brain into a series of "sensory" or psycho- sensorial 
 centres, but he distinguishes between complete and total extirpation of these centres and the phe- 
 nomena which follow these operations.] 
 
 When these centres are partially disorganized, the mechanism of the sensory 
 activity may remain intact, but " the conscious link is wanting." A dog with its 
 centres thus destroyed sees, hears, or smells, but it no longer knows what it sees, 
 hears, or smells. These centres are, in a certain sense, the seat of experience that 
 has been acquired through the organs of sense. Stimulation of these centres 
 may give rise to movements, such as occur when sudden intense sensory impres- 
 sions are produced. These movements, therefore, are to be regarded as reflex, 
 partly as extensive coordinated reflex movements, and are in no way to be con- 
 founded with the movements which result from direct stimulation of the motor 
 cortical centres. To this belongs dilatation of the pupil and the fissure of the 
 eyelids, as well as lateral movements of the eyeball. 
 
 i. The "visual centre," according to Munk, embraces the outer convex 
 part of the occipital lobe of the dog's brain. [This 
 centre and its connections are represented in Fig. 432. 
 It is, therefore, in the area supplied by the posterior 
 cerebral artery.] If this region be completely destroyed, 
 the dog remains permanently blind (" cortical or ab- 
 solute blindness ") in the eye of the opposite side. 
 If, however, only the central circular area be destroyed, 
 there is loss of the conscious visual sensation of the 
 opposite side, which may be called "psychical blind- 
 ness " {Munk) [a condition of visual defect like that 
 observed by Goltz in the dog, in which the dog saw an 
 object, e.g., its food, but failed to recognize it as such. 
 There is a certain amount of recovery if the whole visual 
 area be not removed]. 
 
 [Ferrier and Yeo, however, find that after operations ■ 
 conducted antiseptically, removal of both occipital lobes 
 (monkeys) does not cause any recognizable disturbance 
 of vision or other bodily or mental derangement, pro- 
 vided the lesion does not extend beyond the parieto- 
 occipital fissure. Nor does destruction of both angular 
 gyri cause permanent loss of vision ; such loss of vision 
 lasts only three days, so that in Ferrier's original ex- 
 periments the animals lived for too short a time after 
 the operation to enable a just conclusion to be arrived 
 at. Destruction of both angular gyri and occipital lobes causes total and perma- 
 nent blindness in both eyes in monkeys, without any impairment of the other 
 senses or motor power.] 
 
 Fig. 432. 
 
 1 
 
 Course of the psycho-optic fibres 
 (after Munk). 
 
THE AUDITORY AREA. 723 
 
 Mauthner denies the existence of cortical blindness, and believes that, after destruction of the 
 middle of the visual centre, the reason why the dog does not recognize the object with the opposite 
 eye is because, owing to their being only indirect vision, there is no distinct impression on the retina; 
 The position of the visual centre has been variously stated by different observers. According to 
 Ferrier, in the dog it lies in the occipital part of the III primary convolution, near the spot marked 
 e, e, e, in Fig. 428 ; according to his newer researches, in the occipital lobe and gyrus angularis. 
 
 Connection With the Retina. — Munk asserts that in dogs both retinae are connected with each 
 psycho-optic cortical centre, and in such a manner that the greatest part of each retina is connected 
 with the opposite cortical centre, and only by its most external lateral marginal part with the centre 
 of the same side. If we imagine the surface of one retina to be projected upon the centres, then the 
 most external margin of the first is connected with the centre of the same side, the inner margin of 
 the retina with the inner area of the opposite centre, the upper margin with the anterior area, and 
 the lower marginal part of the retina with the posterior area of the opposite side. The (shaded) 
 middle of the centre corresponds to the position of direct vision of the retina of the opposite side 
 (compare <S 344). 
 
 Stimulation of the visual centre in dogs causes movements of the eyes toward 
 the other side, sometimes with similar movements of the heart and contraction of 
 the pupils. If one eye be excised from new-born dogs, the opposite psycho-optic 
 centre, after several months, is less developed {Munk). After extirpation of 
 the visual centre in young dogs, the channels which connect it with the optic nerve 
 undergo degeneration (v. Monakow) (§ 344). 
 
 In monkeys the centre lies at the tip of the occipital lobe. Unilateral destruction causes blindness 
 of the halves of both retina: lying on the side of the injury. The visual centre in pigeons (Fig. 
 428, IV, where I is placed) lies somewhat behind and internal to the highest curvature of the hemi- 
 spheres (M' Kendrick, Ferrier, Musehold). The visual centre in the frog lies in the optic lobe 
 (Blaschko). 
 
 [The visual path is along the optic nerve to the chiasma, where the fibres from the nasal half 
 of each retina cross to the optic tract, some of the fibres, perhaps, becoming connected with the 
 external corpora geniculata, and some with the pulvinar of the optic thalamus and corpora quadri- 
 gemina, while the great mass sweeps backward to the occipital lobes as the optic expansion of Gra- 
 tiolet. Destruction of this path behind the chiasma causes hemiopia, and certain diseases of the 
 occipital cortex cause a similar result. Perhaps, however, there is another centre in the angular 
 gyrus (and supramarginal lobe), for in cases of word-blindness disease has been found in these 
 regions. Sometimes flashes of light or the appearance of a ball of fire forms the aura in epilepsy, 
 and Hughlings- Jackson thinks that discharging lesions of the right occipital lobe cause colored 
 vision more frequently than on the left.] 
 
 2. The centre for hearing, or " auditory area," lies in the dog, according 
 to Ferrier, in the region of the second primary convolution at /,/,/, (Fig. 428, 
 II), while in the monkey and man it is in the first temporo-sphenoidal convolution 
 (Ferrier's centre, No. 14). Munk locates it in the same region. According to 
 Munk, destruction of the entire region causes deafness of the opposite ear, while 
 destruction of the middle shaded part alone causes "psychical deafness" 
 (" SeelentauMeit"). Stimulation of the centre is followed by a reaction which 
 closely resembles that produced by a sudden fright or that produced by a sudden 
 unexpected noise. The ear muscles are moved in different directions [the animal 
 pricks its ears] {Ferrier). [Ferrier locates the centre for hearing in the monkey 
 in the superior temporo-sphenoidal convolution, and he finds that when the centres 
 on both sides are extirpated, the animal is absolutely deaf; it takes no cognizance 
 of a pistol fired in its neighborhood. In man, injuries to the first and second 
 temporo-sphenoidal convolutions on one side do not appear to cause complete 
 deafness, of one ear, as it seems that the sense of hearing for each ear is perhaps 
 represented on both sides. Bilateral lesions of these convolutions in man causes 
 complete deafness. Disease of these two convolutions is associated with " word- 
 deafness" (p. 732). Wernicke cites a case of a person first affected with word- 
 deafness, who afterward became completely deaf; and after death a bilateral lesion 
 was found in the first temporo-sphenoidal convolution. These convolutions are 
 supplied with blood from the Sylvian artery, a branch of the middle meningeal.] 
 
 [Auditory Aurae. — Equally important with these effects of disease are the sensory impressions, 
 or "aurae," which sometimes usher in an attack of epilepsy; sometimes these aurae consist of 
 
724 THE THERMAL CORTICAL CENTRES. 
 
 sounds or noises, and in these cases the seat of the disease is often in the first temporo-sphenoidal 
 convolution.] 
 
 [The auditory paths are from the auditory nuclei in the medulla oblongata 
 through the pons, where they perhaps cross into the tegmentum, thence into the 
 "sensory crossway," and onward to the auditory centre.] 
 
 [3. The olfactory centre is placed by Ferrier in the subiculum cornu am- 
 monis, or the inner surface of the anterior extremity of the uncinate gyrus (Fig. 
 430). M'Lane Hamilton has recorded a case of epilepsy ushered in by an aura of 
 a disagreeable odor, in which there was atrophy of the gray matter of the right 
 uncinate gyrus.] 
 
 [Olfactory Path. — Although the outer root of the olfactory tract runs direct to the uncinate gyrus, 
 in hemianesthesia resulting from injury to the " sensory crossway," smell is lost on the opposite side, 
 while it is lost on the same side when the uncinate gyrus is involved. It may be that the impulses 
 go first to their own side and then cross afterward.] 
 
 [4. We do not know the centre for taste, and even the course of the nerve of 
 taste is disputed. Ferrier places it close to that of smell.] 
 
 On stimulating the subiculum in monkeys, dogs, cats and rabbits, he observed peculiar movements 
 of the lips and partial closure of the nostrils on the same side (J 365). In man, subjective olfactory 
 and gustatory perceptions are regarded as irritative phenomena, while loss of these sensory activities, 
 often complicated with other cerebral phenomena, are regarded as symptoms of their paralysis. 
 
 [The Gustatory Path crosses in the posterior part of the posterior segment of the internal capsule. 
 While Gowers admits that the chorda tympani is the nerve of taste for the anterior two-thirds of 
 the tongue, he thinks that it reaches the facial nerve from the spheno-palatine ganglion through the 
 Vidian nerve. He denies that the glosso-pharyngeal is concerned in taste, and " he believes that 
 taste impressions reach the brain solely by the roots of the 5th nerve " He admits that the nerves 
 of taste to the back part of the tongue may be distributed with the glosso-pharyngeal, reaching 
 them through the otic ganglion by the small superficial petrosal and tympanic plexus.] 
 
 [5. Ferrier places the centre for tactile sensation in the hippocampal region, close 
 to the distribution of part of the posterior cerebral artery ; so far this has not been 
 confirmed. The centre for the sensation of pain has not been denned, probably 
 it is very diffuse.] 
 
 6. Munk is of opinion that the surface of the cerebrum in the region of the motor centres acts at 
 the same time as " sensory areas " (Fiihlsphare), i. t., they serve as centres for the tactile and 
 muscular sensations and those of the innervation of the opposite side. He asserts that after injury 
 to these regions the corresponding functions are affected. 
 
 According to Bechterew, the centres for the perception of tactile impressions, those of innerva- 
 tion, of the muscular sense, and painful impressions are placed in the neighborhood of the motor 
 areas (dog) ; the first immediately behind and external to the motor areas, the others in the region 
 close to the origin of the Sylvian fissure. [So far this agrees with the views of Starr yp. 719).] 
 
 Goltz, who first accurately described the disturbances of vision following upon injuries to the 
 cortex in dogs, is opposed to the view of sensory localization. He believes that each eye is con- 
 nected with both hemispheres. He asserts that the disturbance of vision, after injury to the brain, 
 consists merely in a diminished color and space sense. The recovery of the visual perception of 
 one eye after injury of one side of the cortex cerebri he explains by supposing that this injury 
 merely causes a temporary inhibition of the visual activity in the opposite eye, which disappears at 
 a later period. Instead of psychical blindness and deafness he speaks of a " cerebro-optical " and 
 " cerebro-acoustical weakness." 
 
 377. THE THERMAL CORTICAL CENTRES.— A. Eulenberg and Landois dis- 
 covered an area on the cortex cerebri whose stimulation produced an undoubted effect upon the 
 temperature and condition of the blood vessels of the opposite extremities. This region ( Fig. 428, 
 I, /), generally embraces the area, in which at the same time the motor centres for the flexors and 
 rotators of the fore limb (3), and for the muscles of the hind limb (4) are placed. The areas for 
 the anterior and posterior limbs are placed apart, that for the anterior limb lies somewhat more ante- 
 riorly, close to the lateral end of the crucial salcus. Destruction of this region causes increase of 
 the temperature of the opposite extremities; the temperature may vary considerably (l.5°to2°, 
 and even to 13 °C). This result has been confirmed by Hitzig, Bechterew, Wood and others. 
 This rise of the temperature is usually present for a considerable time after the injury, although it 
 may then undergo variations. Sometimes it may last three months, in other cases it gradually 
 reaches the normal in two or three days. In well-marked cases there is a diminution of the resist- 
 ance of the wall of the femoral artery to pressure, and the pulse curve is not so high (Seinke), 
 
TOPOGRAPHY OF THE CORTEX CEREBRI. 725 
 
 Ix>cal electrical stimulation of the area causes a slight temporary cooling of the opposite extremi- 
 ties, which may be detected by the thermo-electric method. Stimulation by means of common salt 
 acts in the same way, but in this case the phenomena of destruction of the centre soon appear. As 
 yet it has not been proved that there is a similar area for each half of the head. The cerebro-epileptic 
 attacks (<S 375 ) increase the bodily temperature, partly owing to the increased production of heat by 
 the muscles ($ 302), partly owing to diminished radiation of heat through the cutaneous vessels, in 
 consequence of stimulation of the thermal cortical nerves. The experiments led to no definite 
 results when performed on rabbits. According to Wood, destruction of these centres occasions an 
 increased production of heat that can be measured by calorimetric methods, while stimulation 
 causes the opposite result. 
 
 These experiments explain how psychical stimulation of the cerebrum may have an effect upon the 
 diameter of the blood vessels and on the temperature, as evidenced by sudden paleness and con- 
 gestion (| 378, III). 
 
 [Heat Production. — Injury to the fore-brain has no effect on the temperature. If the brain of 
 a rabbit be punctured through the large fontanelle and the stylette be forced through the gray 
 matter on the surface, white matter, and the median portion of the corpus striatum right to the base 
 of the brain, there is a rapid rise of the temperature which may last several days. Injury to the 
 gray cortex does not affect the temperature. After puncture of the corpus striatum the highest tem- 
 perature is reached only after twenty-four to seventy hours, but when the puncture reaches the base 
 of the brain this result occurs in two to four hours. Electrical stimulation of these areas causes the 
 same effect on the temperature. Direct injury to certain parts of the brain is followed by a rise of 
 the temperature — or fever. There is at the same time an increase of the O taken in, the C0 2 given 
 off and a decided increase of the N given off, indicating an increase in the proteid metabolism, 
 which points to an increased production of heat (Aronsohn and Sachs, Richet, Wood).'] 
 
 General and Theoretical. — Goltz's View. — Goltz uses a different method to remove the cortex 
 cerebri — he makes an opening in the skull of a dog, and by means, of a stream of water washes 
 away the desired amount of brain matter. He describes, first of all, inhibitory phenomena, 
 which are temporary and due to a temporary suppression of the activity of the nervous apparatus, 
 which, however, is not injured anatomically, but may be explained in the same way as the suppres- 
 sion of reflexes by strong stimulation of sensory nerves (g 361, 3). In addition, there are the per- 
 manent phenomena, due to the disappearance of the activity of the nervous apparatus, which is 
 removed by the operation. A dog with a large mass of its cerebral cortex removed may be com 
 pared to an eating complex reflex machine. It behaves like an intensely stupid dog, walks slowly, 
 with its head hanging down ; its cutaneous sensibility is diminished in all its qualities — it is less sen- 
 sitive to pressure on the skin ; it takes less cognizance of variations of temperature, and does not 
 comprehend how to feel ; it can with difficulty accommodate itself to the outer world, especially 
 with regard to seeking out and taking its food. On the other hand, there is no paralysis of its 
 muscles. The dog still sees, but it 'does not understand what it does see; it looks like a somnam- 
 bulist, who avoids obstacles without obtaining a clear perception of their nature. It hears, as it 
 can be wakened from sleep by a call, but it hears like a person just wakened from a deep sleep by 
 a voice — such a person does not at once obtain a distinct perception of the sound. The same is the 
 case with the other senses. It howls from hunger, and eats until its stomach is filled ; it manifests 
 no symptoms of sexual excitement. 
 
 With regard to the localization of the different centres in the cerebrum, Goltz obtained the fol- 
 lowing results : He finds that a dog with both parietal lobes destroyed has its sensibility perma- 
 nently blunted, its intelligence diminished, and is vicious ; while when both occipital lobes are 
 destroyed there is severe and permanent disturbance of vision. He supposes that every part of the 
 brain is concerned in the functions of willing, feeling, perception and thinking. Every section is, 
 independently of the others, connected by conductions with all the voluntary muscles, and on the 
 other hand with all the sensory nerves of the body. He regards it as possible that the individual 
 lobes have different functions. 
 
 Inhibitory Phenomena. — Injury to the brain also causes inhibitory phenomena, such as the dis- 
 turbances of motion, the complete hemiplegia which is frequently observed after large unilateral 
 injuries of the cortex cerebri ; these are regarded by Goltz as inhibitory phenomena due to the 
 injury acting on lower infra-cortical centres whose action inhibits movement, but these movements 
 are recovered as soon as the inhibitory action ceases. 
 
 378. PHYSIOLOGICAL TOPOGRAPHY OF THE HUMAN 
 CORTEX CEREBRI.— We accept the arrangement of convolutions accord- 
 ing to Ecker, of which a short resume is given in § 375. 
 
 I. The cortical motor regions for the face and the limbs are grouped around 
 the fissure of Rolando, including the ascending frontal, ascending parietal, and 
 part of the parietal lobule (Fig. 431). The centre for the face occupies the low- 
 est third of the ascending frontal convolution and reaches also on the lowest fifth 
 of the ascending parietal. The arm centre occupies the middle third of the 
 ascending frontal and middle three-fifths of the ascending parietal convolutions, 
 
726 
 
 HEMIPLEGIA. 
 
 while the leg centre lies at the upper end of the sulcus and extends backward into 
 the parietal lobule (and perhaps on to the superior frontal convolution') (Fig. 431). 
 This leg centre is continued over on to the paracentral lobule opposite the upper 
 end of the fissure of Rolando in the marginal convolution on the mesial aspect 
 of the hemisphere (Fig. 433) where the centres for the muscles of the trunk also 
 exist (p. 719). The centre for speech is in the posterior part of the third left 
 frontal convolution (Fig. 431). 
 
 Blood Supply. — These convolutions are supplied with blood from four to five branches of the Syl- 
 vian artery, which may sometimes be plugged with an embolon. When a clot lodges in this artery, 
 the branches to the basal ganglia may remain pervious, while the cortical branches may be plugged 
 (Duret, Hcubner) (\ 381). 
 
 [Hemiplegia consists of motor paralysis of one-half of the body, although, as 
 a rule, all the muscles are not paralyzed to the same extent ; in some there may be 
 
 Fig. 433. 
 
 Transverse section of the cerebral hemisphere. CCa, corpus callosum; NC, caudate nucleus; NL, lenticular nu- 
 cleus; IC, internal capsule; CA, internal carotid artery; flSL, lenticular-striate artery ("Artery of hemor- 
 rhage ") ; F. A, L, T, position of motor areas governing the movements of the face, arm, leg, and trunk muscles 
 of the opposite side (Horsley). 
 
 complete paralysis, i. e., they are entirely removed from voluntary control, while 
 in others there is merely impaired voluntary control. It may be caused by affec- 
 tions of the cortical centres or by lesion of the motor tracts above the medulla, 
 and the paralysis is always on the side opposite to the lesion owing to the decussa- 
 tion of the motor paths in the medulla. If the case be a severe one, we have 
 what Charcot terms hemipUgie centrale vulgaire, or "complete hemiplegia," due 
 to lesion of the cortical centres for the face, arm, and leg. While the arm and 
 leg are completely paralyzed, the lower part of the face is more affected than the 
 upper half, which is usually not much affected. All those movements under vol- 
 untary control, and especially those that have been learned, are abolished, while 
 the associated and bilateral movements, which even animals can execute imme- 
 diately after birth, remain more or less unaffected. Hence the hand is more par- 
 alyzed than the arm ; this, again, than the leg ; the lower facial branches more 
 
POSITION OF THE MOTOR CENTRES. 727 
 
 than the upper ; the nerves of the trunk scarcely at all (Ferrier). When an ex- 
 traordinary effort is made, it will be found, that there is some impairment of the 
 power of the muscles of mastication and respiration, although the muscles on 
 opposite sides act together (Gowers). The trunk muscles, as a rule, are but 
 slightly affected, or not at all, as their centre is elsewhere. There may be altera- 
 tions of sensibility and of the reflexes.] 
 
 Conjugate deviation of the eyes with rotation of the head is frequently present in the early 
 period of hemiplegia, although it usually disappears. When a person turns his head to one side, 
 there is an associated movement of certain of the ocular muscles with those of the neck. The 
 head and eyes are usually turned to the side of the lesion ; this is termed " conjugate deviation," 
 so that the power of voluntarily moving the eyes and head to the paralyzed side is temporarily lost. 
 The unopposed muscles rotate the head and eyes to the sound side. If the lesion be in the pos- 
 terior part of the pons, the deviation is to the paralyzed side {Pttvost). 
 
 [Subsequent Effects. — If there be say a hemorrhage into these motor regions, or from the 
 lenticulo-striate artery, so as to compress the pyramidal fibres in the knee and anterior two-thirds 
 of posterior segment of the internal capsule, then there is usually tonic or persistent contraction of 
 the muscles affected. These tonic spasms may accompany the hemorrhage, or come on a few days 
 after it and make up the condition of early rigidity. The contraction — if any — accompanying the 
 hemorrhage is due to direct irritation of the pyramidal fibres, while that which comes on a few days 
 later, and usually lasts a few weeks, is also due to irritation of these fibres, probably produced by 
 inflammatory action in and around the seat of the lesion. The affected limb is stiff and resists 
 passive movement. After a few weeks, late rigidity sets in and is persistent, and it is characterized 
 by structural changes in the pyramidal paths which lead to other results. There is secondary de- 
 scending degeneration in the pyramidal tracts, which cause " contracture" {Charcot) in the 
 paialyzed limbs, while at the same time the deep or tendinous and periosteal reflexes (ankle clonus, 
 rectus clonus, and the deep reflexes of the arm tendons, are exaggerated). The spastic rigidity is 
 usually more marked in the arm than leg, and it generally affects the flexors more than the extensors, 
 so that the upper arm is drawn close to the trunk, the elbow, arm, and fingers flexed ; in the leg 
 the extensors of the leg overcome the peronei. Hitzig has pointed out that the contracture is less 
 during sleep and after rest. The muscles at first can be stretched by sustained pressure, but after 
 months or years structural changes occur in the muscles, ligaments, and tendons, and the limbs 
 assume a permanent and characteristic attitude.] 
 
 In hemiplegic persons, the power of the unparalyzed side is sometimes diminished (Brtrwn- 
 Slquard, Charcot, Pitres), which is not sufficiently explained by the fact that some bundles of the 
 pyramidal tracts remain on the same side. 
 
 Acquired Movements. — Some movements performed by man are learned only after much 
 practice, and are only completely brought under the influence of the will after a time, such as the 
 movements of the hand in learning a trade. Such movements are reacquired only very slowly, or 
 not at all, after injury to the psychomotor centres. Those movements, however, which the body 
 performs without previous training, such as the associated movements of the eyeballs, the face, and 
 some of those of the legs, are rapidly recovered after such an injury, or they suffer but little, if at 
 all. Thus the facial muscles seem never to be so completely paralyzed after a lesion of the facial 
 cortical centre, as in affections of the trunk of the facial nerve the eye especially can be closed. 
 Sucking movements have been observed in hemicephalous foetuses. 
 
 Degeneration of the Pyramidal Tracts. — After destruction of the cortical 
 motor areas, descending degeneration of the cortico-motor paths, or "pyramidal 
 tracts," takes place (§ 365). Degenerative changes have been found to occur 
 within the white matter under the cortex, in the anterior two-thirds of posterior 
 segment of the internal capsule [in the middle third of the crusta (Figs. 434,* 
 435, L], pons, in the pyramids of the medulla oblongata (Fig. 434), and thence 
 they have been traced into the pyramidal paths (anterior and lateral) of the spinal 
 cord {Charcot, Singer, M. Rosenthal). It is evident that lesions of these tracts at 
 any part of their course must have the same result, viz., to produce hemiplegia. 
 (For the subsequent effects, see p. 660.) In a case of congenital absence of the 
 left fore arm, Edinger found that the right central convolutions were developed. 
 
 Ataxic motor conditions similar to those that occur in animals (p. 721) take place in man, and 
 are known as cerebral ataxia. 
 
 The Position of the Centres is given at p. 718. 
 
 [But we may have localized lesions affecting one or more of the cortical 
 motor areas ; these are called Monoplegias. Cases in man are now sufficiently 
 
728 
 
 POSITION OF THE MOTOR CENTRES. 
 
 numerous to permit of accurate diagnosis.] Crural [rare lesions recorded in the 
 convolutions at the upper end of the fissure of Rolando, and the continuation of 
 this area on to the paracentral lobule of the marginal convolution], — brachio- 
 crural, more common, upper and middle thirds of the ascending frontal and 
 ascending parietal convolutions — brachial, brachio-facial — facial, the last in 
 the lowest part of the central convolutions. 
 
 [Convulsions and spasms may be discharged from motor cortical lesions, and 
 these, whether they affect the general or localized areas, give rise to unilateral 
 convolutions and monospasms respectively.] 
 
 Paralysis of the muscles of the neck and throat indicates a lesion of the central convolutions, and 
 so does paralysis of the muscles of the eye. Lesions of the cortex always cause simultaneous move- 
 ments of the head and eyeballs 
 
 Irritation of the Motor Centres. — If the motor centres are irritated by 
 pathological processes, such as hypersemia, or inflammation, in a syphilitic dia- 
 
 Fig. 434. 
 
 Fig. 434. — Secondary descending generation in middle third of right crus and in medulla after destruction of the 
 cortical motor centres on the right side. Fig. 435. — Horizontal section of the cerebral peduncle in secondary 
 degeneration of the pyramidal tracts, where the lesion was limited to the middle third of the posterior segment 
 of the internal capsule. F, healthy crusta ; L, locus niger; P, internal third of the crusta on the diseased side ; 
 D, secondary degeneration in the middle third of the crusta; CQ, corpora quadrigemina with the iter below them. 
 
 thesis — more rarely by tumors, tubercle, cysts, cicatrices, fragments of bone — 
 there arise spasmodic movements in the corresponding muscle groups. This con- 
 dition of a sudden discharge of the gray matter resulting in local spasms is called 
 " Jacksonian or cerebral epilepsy." 
 
 Monospasm. — According to the seat of the spasm, it is called facial, brachial, crural, mono- 
 spasm, etc. Of course, these spasms may affect several groups of muscles. Bartholow and Scia- 
 manna have stimulated the exposed human brain successfully with electricity. 
 
 Cerebral Epilepsy. — Very powerful stimulation of one side may give rise to 
 bilateral spasms, with loss of consciousness. In this case impulses are conducted 
 to the other hemisphere by commissural fibres (§ 379). 
 
 Movements of the Eye. — Nothing definite is known regarding the centre in the cortex for 
 voluntary combined movements of the eyeballs in man. In paralytic affections of the cortex and of 
 the paths proceeding from it, we occasionally find both eyes with a lateral deviation. If the par- 
 alytic affection lies in one cerebral hemisphere, the conjugate deviation of the eyeballs is toward 
 
APHASIA. 729 
 
 the sound side (p. 620). If it is situated in the conducting paths, after these have decussated, viz., 
 in the pons, the eyes are turned toward the paralyzed side (Priyost). 
 
 If the part be irritated so as to produce spasms in the opposite half of the body, of course the 
 eyes are turned in the opposite direction to that in pure paralysis (Landouzy and Grasset). Instead 
 of the lateral deviation of the eyeballs already described, occasionally in cerebral paralysis there is 
 merely a weakening of the lateral recti muscles, so that during rest the eyes are not yet turned 
 toward the sound side, but they cannot be turned strongly toward the affected side (Leicktenstern, 
 Hunnius). The centre for the levator palpebrae superioris appears to be placed in the gyrus angu- 
 laris [Grasset, Landouzy, Chauffard). 
 
 II. The Centre for Speech. — The investigations of Bouilland [1825], Dax 
 [1836], Broca [1861], Kussmaul, and Broadbent and others have shown that the 
 third left frontal convolution of the cerebrum (Figs. 429, F, 3, and 431) is 
 of essential importance for speech, while probably, also, the insula, or island of 
 Reil, is concerned. It is seen to be deeply placed on lifting up the overhanging 
 part of the brain called the operculum, lying between the two branches of the 
 Sylvian fissure (S). The motor centres for the organs of speech (lips, tongue) lie 
 in this region, and in this region also the psychical processes in the act of speech 
 are completed. In the great majority of mankind the centre for speech is located 
 in the left hemisphere. The fact that most men are right-handed also points to a 
 finer construction of the motor, apparatus for the upper extremity, which must also 
 be located in the left hemisphere. Men, therefore, with pronounced right-handed- 
 ness (droitiers) are evidently left-brained (gauchers du cerveau — Broca). By far 
 the greater number of mankind are "left-brained speakers" {Kussmaul); still 
 there are exceptions. As a matter of fact, cases of left-handed persons have been 
 observed who lost their power of speech after a lesion of the right hemisphere 
 ( Ogle, Habershoti). Investigations on the brains of remarkable men have shown 
 that in them the third frontal convolution is more extensive and more complex 
 than in men of a lower mental calibre. In deaf mutes it is very simple ; micro- 
 cephales and monkeys possess only a rudimentary third frontal (Rudinger). 
 
 The motor tracts for speech pass along the upper edge of the island of Reil, then into the sub- 
 stance of the hemispheres internal to the posterior edge of the knee of the internal capsule; from 
 thence through the crusta of the left cerebral peduncle into the left half of the pons, where it crosses, 
 then into the medulla oblongata, which is the place where all the motor nerves (trigeminus, facial, 
 hypoglossal, vagus, and respiratory nerves) concerned in speech arise. Total destruction of these 
 paths, therefore, causes total aphasia ; while partial destruction causes a greater or less disturbance 
 of the mechanism of articulation, which has been called " anarthria " by Leyden and Wernicke. 
 
 Conditions. — Three activities are required for speech — (1) the normal move- 
 ment of the vocal apparatus (tongue, lips, mouth, and respiratory apparatus) ; (2) 
 a knowledge of the signs for objects and ideas (oral, written, or imitative or mi- 
 metic signs) ; (3) the correct union of both. 
 
 Aphasia. — Injury of the speech centre causes either a loss or more or less con- 
 siderable disturbance of the power of speech. The loss of the power of speech is 
 called "aphasia." [Aphasia, as usually understood, means the partial or com- 
 plete loss of the power of articulate speech from cerebral causes.] 
 
 The following forms of aphasia may be distinguished : — 
 
 1. Ataxic aphasia for the oro-lingual hemiparesis of Ferrier), i.e., the loss of speech, owing to 
 inability to execute the various movements of the mouth necessary for speech. Whenever such a 
 person attempts to speak, he merely executes incoordinated grimaces and utters inarticulate sounds. 
 [The muscles concerned in articulation, however, are not paralyzed, but there is an absence of co- 
 ordination of these muscles due to disease of the cortical centre.] Hence, the patient cannot repeat 
 what is said to him. Nevertheless, the psychical processes necessary for speech are completely re- 
 tained, and all words are remembered ; and hence these persons can still give expression to their 
 thoughts graphically or by writing. If, however, the finely adjusted movements necessary for writ- 
 ing are lost, owing to an affection of the centre of the hand, then there arises at the same time the 
 condition of agraphia, or inability to execute those movements necessary for writing. Such a per- 
 son, when he desires to express his ideas in writing, only succeeds in making a few unintelligible 
 scrawls on the paper. Occasionally such patients suffer from loss of the power of imitation or 
 aminia (Kussmaul). 
 
 ■*. Amnesic Aphasia, or Loss of the Memory of Words. — Should the patient, however, hear the 
 
730 APHASIA. 
 
 word, its significance recurs to him. The movements necessary for speech remain intact ; hence 
 such a patient can at once repeat or write down what is said to him. Sometimes only certain kinds 
 of words are forgotten, or it may be "even only parts of these words are spoken. [Nouns and proper 
 names usually go first.] Cases of amnesic aphasia, or the mixed ataxic-amncsic form of disturbance 
 of speech, point to a lesion of the third frontal convolution and of the island of Reil on the left side. 
 Another form of amnesic aphasia consists in this, that the words remain in one's memory but do not 
 come when they are wanted, i.e., the association between the idea and the proper word to give ex- 
 pression to it is inhibited [Kussmaul). It is common for old people to forget the names of persons 
 or proper names; indeed, such a phenomenon is common within physiological limits, and it may 
 ultimately pass into the pathological condition of amnesia senilis. Among the disturbances of 
 speech of cerebral origin, Kussmaul reckons the following: — 
 
 3. Paraphasia, or the inability to connect rightly the ideas with the proper words to express 
 these ideas, so that, instead of giving expression to the proper ideas, the sense may be inverted, or 
 the form of words may be unintelligible. It is as if the person were continually making a " slip of 
 the tongue." 
 
 4. Agrammatism and ataxaphasia, or the inability to form the words grammatically and to ar- 
 range them synthetically into sentences. Besides these, there is — 
 
 5. A pathological slow way of speaking (bradyphasia), or a pathological and stuttering way of 
 reading (tumultus sermonis), both conditions being due to derangement of the cortex [Kuss- 
 maul). The disturbance of speech depending essentially upon affections of the peripheral nerves, 
 or of the muscles of the organs of the voice and speech, are already referred to in \\ 319, 349, and 
 354- 
 
 [In word-blindness the person cannot name a letter or a word, so that he 
 Fig. 436. Fig. 437. 
 
 Figs. 436, 437. — Schemes of aphasia. A, centre or auditory images ; M, or motor images ; B, perception centre ; 
 Oc, eye; E, reading centre ; 1 to 7 lesions [Lichtheim). 
 
 cannot understand symbols, such as printed or written words, or it may be any 
 familiar object, although he can see quite well, while he can speak fluently and 
 write correctly.] 
 
 [In word-deafness the person hears other sounds and is not deaf, but he does 
 not hear words.] 
 
 [The study of aphasia in its various forms is simplified by a study of the mode of acquisition of 
 language by a child. The child hears spoken words and obtains auditory memories or impressions 
 of these sounds (called by Lichtheim " auditory word-representations "), and this must form 
 the starting-point of language, and by and by it begins to coordinate its muscles to produce sounds 
 imitative of these. Thus we have two centres, one for " auditory images " (Fig. 436, A), and the 
 other for " motor images " (Fig. 436, M), and these two must be connected, thus establishing a 
 reflex arc. There is a receptive and an emissive department as represented in the scheme. We 
 must assume the existence of a higher centre (B), " where conceps are elaborated," where these 
 sounds become intelligible. Volitional language requires a connection between B and M, as well 
 as between A and M. But we have also reading and writing. Suppose O to represent a centre 
 for visual impressions (printed words or writing), which we can understand through the connection 
 between such visual impressions and auditory impressions, whereby a path is established through 
 OA (Fig. 437). In reading aloud, however, the oro-lingual muscles must be coordinated, so we 
 have the path OAM opened up. In writing or copying written characters, the movements of the 
 hand are special, and perhaps require a special centre, or at least a special arrangement of the chan- 
 nels for impulses in the centre ; the movements are learned under the guidance of ocular impres- 
 
THERMAL AND SENSORY CORTICAL CENTRES. 731 
 
 sions, so we connect O and E, E being the centre guiding the movements in writing. As to 
 volitional writing the impulses pass through M, but does it pass directly to E, or indirectly through 
 A ? Lichtheim assumes that it goes direct from M to E. It is evident that there are seven chan- 
 nels which may be interrupted, each one giving rise to a different form of aphasia (I to 7).] 
 
 [Looked at from another point of view, either the ingoing (a) or outgoing (?«) channels or cen- 
 tres, or the commissural fibres between both, may be affected. If the motor centre is affected, we 
 have Wernicke's " motor aphasia ; " if the sensory, his " sensorial aphasia."] 
 
 [In the most common form, or ataxic aphasia {KussmauT), which was that described by Broca, 
 or the " motor aphasia" of Wernicke, the lesion is in Fig. 436, in M, i. e., in the motor, or what 
 Ross calls the emissive department. In such a case it is obvious that there will be loss of (1) volitional 
 speech, (2) repetition of words, (3) reading aloud, (4) volitional writing, and (5) writing to dicta- 
 tion; while there will exist (a) understanding of spoken words, (b) also of written words, (c) and 
 the faculty of copying. If the lesion be in A, we have the " sensorial aphasia" of Wernicke, i. c, 
 in the acoustic word centre; we find loss of (1) understanding of spoken language, (2) also of 
 written language, (3) faculty of repeating words, (4) and of writing to dictation, (5) and of reading 
 aloud ; there will exist (a) the faculty of writing, (b) of copying words, and (c) of volitional 
 speech, but the volitional speech is imperfect, the wrong word being often used, so that there is the 
 condition of "paraphasia." If the connection between A and M be destroyed, other results will 
 follow, and such cases of " commissural " aphasia have been described by Wernicke. If the inter- 
 ruption be between B and M we have a not uncommon variety of motor aphasia (4), where there 
 is loss of (1) volitional speech, and (2) volitional writing, and there exist [a) understanding of 
 spoken language, (b) of written language, (c) the faculty of copying; but it differs from Broca's 
 aphasia in that there also exists {d ) the faculty of repeating words, (e) writing to dictation, (f), and 
 reading aloud. If the lesion is in Mm (5) the symptoms will be those of Broca's aphasia, but there 
 will exist (1) the faculty of volitional writing, and (2) of writing to dictation. Many examples of 
 this occur where patients have lost the faculty of speaking, but can express their thoughts in writ- 
 ing. In lesions of the path AB (6) there will be loss of (1) understanding of spoken language, 
 and (2) of written language, and there will exist (a) volitional speech (but it will be paraphasic), 
 (b) volitional writing (but it will have the characters of paragraphia, (c) the faculty of repeating 
 words, (d) reading aloud, (e) writing to dictation, and (/) power of copying words. The person 
 will be quite unable to understand what he repeats, reads aloud, or copies.] 
 
 III. The thermal centre of Eulenberg and Landois for the extremities is associated with the 
 motor areas. Injury or degeneration of these areas causes inequality of the temperature on both 
 sides (Bechterew). In long-standing paralysis the initially high temperature of the affected limb 
 may fall lower than that of the sound limb ($ 377). In cases of insanity, with general progressive 
 paralysis, due to inflammation of the cortex cerebri, the temperature of the axilla on the same side 
 is usually higher on the side which is the seat of the paralysis. In cases of convulsions, due to in- 
 flammatory irritation of the cortex cerebri, during the attack the temperature on the same side as 
 the centre is several tenths of a degree higher than on the other side {Reinhard). 
 
 IV. The sensory regions are those areas in which conscious perceptions of 
 the sensory impressions are accomplished. Perhaps they are the substratum of 
 sensory perceptions, and of the memory of sensory impressions. 
 
 1. The psycho-optic or visual centre, according to Munk, Meynert, and 
 Huguenin, includes the occipital lobes (Fig. 429, o 1 , o 2 , o 3 ), while according to 
 Exner the first and second occipital convolutions are its chief seats. Huguenin 
 observed, in a case of long-standing blindness, consecutive disappearance of the 
 occipital convolutions on both sides of the parieto-occipital fissure, while Giova- 
 nardi, in a case of congenital absence of the eyes, observed atrophy of the occi- 
 pital lobes, which were separated by a deep furrow from the rest of the brain. 
 Stimulation of the centre gives rise to the phenomena of light and color. Injury 
 causes disturbance of vision, especially hemiopia of the same side (§ 344 — 
 Westphal, Jastrowitz). When one centre is the seat of irritation there is pho- 
 topsia of the same halves of both eyes {Charcot, Prinaud'). Stimulation of both 
 centres causes the occurrence of the phenomena of light or color, or visual hal- 
 lucinations in the entire field of vision. Cases of injury to the brain, where the 
 sensations of light and space are quite intact, and where the color sense alone is 
 abolished, seem to indicate that the color sense centre must be specially localized 
 in the visual centre (Samelsohn, Stefan). After injury of certain parts, especially 
 of the lower parietal lobe, " psychical blindness " may occur. A special form of 
 this condition is known as "word-blindness " or alexia (Coecitas verbalis), 
 which consists in this, that the patient is no longer able to recognize ordinary 
 written or printed characters (p. 730). 
 
732 
 
 THE AUDITORY, GUSTATORY AND OLFACTORY CENTRES. 
 
 Charcot records an interesting case of psychical blindness. After a violent paroxysm of rage, an 
 intelligent man suddenly lost the memory of visual impressions ; all objects (persons, streets, houses) 
 which were well known to him appeared to be quite strange, so that he did not even recognize him- 
 self in a mirror. Visual perceptions were entirely absent from his dreams. 
 
 Clinical observations on hemiopia (§ 344) show that the field of vision of each eye is divided 
 into a larger outer and a smaller inner portion, separated from each other by a vertical line passing 
 through the macula lutea. Each right or left half of both visual fields is related to one hemisphere ; 
 both left halves are projected upon the left occipital lobes, and both right upon the right occipital 
 lobes. Thus, in binocular vision every picture (when not too small) must be seen in two halves ; 
 the left half by the left, the right half by the right hemisphere ( Wernicke). 
 
 As a result of pathological stimulation of the visual centre, especially in the insane, visual spectres 
 may be produced. Pick observed a case where the hallucinations were confined to the right eye. 
 
 2. The psycho-acoustic or auditory centre lies on both sides (crossed) in 
 the temporo-sphenoidal lobes; when it is completely removed deafness results, 
 while partial (left side) injury causes psychical deafness. Among the phenomena 
 caused by partial injury is surditas verbalis (word-deafness), which may occur 
 
 Fig. 438. 
 
 Relation of the fissures and convolutions to the surface of the scalp -f Most prominent part of the parietal emi- 
 nence ; a, convex line bounding parietal lobe below ; b, convex line bounding the temporo-sphenoidal lobe behind 
 (R. W. Heid). 
 
 alone or in conjunction with coecitas verbalis. Wernicke found in all cases of 
 word-deafness softening of the first left temporo-sphenoidal convolution (p. 730). 
 In left-handed persons the centre lies, perhaps, in the right temporo-sphenoidal 
 lobes ■( Westphal). 
 
 Clinical. — We may refer the coecitas and surditas verbalis (Kussmaul) to the aphataxic group 
 of diseases, in so far as they resemble the amnesic form. A person word-blind or word-deaf resem- 
 bles one who, in early youth, has learned a foreign tongue, which he has completely forgotten at a 
 later period. He hears or reads the words and written characters ; he can even repeat or write the 
 words, but he has completely lost the significance of the signs. While an amnesic aphasic person 
 has only lost the key to open his vocal treasure, in a person who is word-blind or word-deaf even 
 this is gone. From a case of recovery it is known that to the patient the word sounds like a con- 
 fused noise. Huguenin found atrophy of the temporo-sphenoidal lobes after long- continued deafness. 
 
 3. Gustatory and Olfactory Centre. — In the uncinate gyrus, on the inner 
 side of the temporo-sphenoidal lobe (especially on the inner side of that marked 
 
THE BASAL GANGLIA. 733 
 
 U in Fig. 425), Ferrier locates the joint centres for smell and taste. These two 
 centres do not seem to be distinct locally from each other. 
 
 4. Tactile Areas. — According to Tripier, Exner, Petrina, and others, all the 
 tactile cerebral fields from different parts of the body coincide with the motor 
 cortical centres for these parts. 
 
 Occasionally, in epileptics, strong stimulation of the sensory centres, as expressed in the excessive 
 subjective sensations, accompanies the spasmodic attacks (compare \ 393, 12). Such epileptiform 
 hallucinations, however, occur without spasms, and are accompanied only by disturbances of con- 
 sciousness of very short duration (Berger). 
 
 Course of the Psycho-sensory Paths. — The nerve fibres which conduct 
 impulses from the sensory organs to the sensory cortical centres, pass through 
 the posterior third of the posterior limb of the intestinal capsule between the optic 
 thalamus and the lenticular nucleus (Fig. 439, S). Hence section of this part of 
 the internal capsule causes hemianaesthesia of the opposite half of the body 
 {Charcot^ Veyssiere, Carville, Duref). In such a case sensory functions are abol- 
 ished — only the viscera retaining their sensibility. There may also be loss of 
 hearing (Veller, Donkiti), smell and taste, and hemiopia {Bechterew). 
 
 In cases where there is more or less injury or degeneration of these paths, there is a corresponding 
 greater or less pronounced loss of the pressure and temperature sense, of the cutaneous and muscular 
 sensibility, of taste, smell, and hearing. The eye is rarely quite blind, but the sharpness of vision 
 is interfered with, the field of vision is narrowed, while the color sense may be partially or completely 
 lost. The eye on the same side may suffer to a slight extent. 
 
 V. Numerous cases of injury of the anterior frontal region, without inter- 
 ference with motor or sensory functions, have been collected by Charcot, Pitres, 
 Ferrier, and others. On the other hand, enfeeblement of the intelligence and 
 idiocy are often observed in acquired or congenital defects of the prefrontal region. 
 In highly intellectual men, Riidinger found, in addition, a considerable develop- 
 ment of the temporo-sphenoidal lobe. According to Flechsig, there is no doubt 
 that the frontal lobes and the temporo-occipital zone are related to intellectual 
 processes, more especially the "higher" of these. 
 
 Topography of the Brain. — The relations of the chief fissures and convolutions of the brain 
 to the surface of the skull are given in Fig. 429, the brain being represented after Ecker. [Turner 
 and others have given minute directions for finding the position of the different convolutions by 
 reference to the sutures and other prominent parts of the skull. The foregoing diagram (Fig. 438), 
 by R. W. Reid, shows the relation of the convolutions to certain fixed lines.] 
 
 379. THE BASAL GANGLIA— THE MID-BRAIN.- [The corpus 
 striatum in reality consists of two parts, an intra-ventricular portion projecting 
 into the lateral ventricle and called the caudate nucleus, and an extra-ven- 
 tricular portion the lenticular nucleus. Between the head of the caudate nu- 
 cleus internally and the lenticular nucleus externally lies the anterior division of 
 the internal capsule. The fibres which pass between these ganglia do not seem to 
 form connections with them. The expanded head of the caudate nucleus is in 
 front, and lies inside and around the front of the lenticular nucleus, with which 
 and the anterior perforated space it is continuous ; it sweeps backward into a 
 tailed extremity, which nearly surrounds the lenticular nucleus like a loop. The 
 lenticular nucleus is biconvex in a horizontal section (Fig. 439), but triangular 
 and subdivided into three divisions when seen in a vertical section (Fig. 433).] 
 
 [The older observations on the corpora striata in man may be dismissed, as a 
 distinction was not drawn between injury to its two parts on the one hand and the 
 internal capsule on the other.] 
 
 [The caudate nucleus and lenticular nucleus in their development are 
 coordinate with the development of the cortex cerebri (Fig. 439). Electrical 
 stimulation of these ganglia causes general muscular contractions in the oppo- 
 site half of the body. The same result is obtained as if all the motor cortical 
 centres were stimulated simultaneously.] 
 
734 
 
 THE BASAL GANGLIA. 
 
 Gliky did not observe movements on stimulating the corpus striatum in rabbits ; it would seem 
 that in these animals the motor paths do not traverse these ganglia, but merely pass alongside of 
 
 [Lesions of the lenticular nucleus or of the cordate nucleus do not seem to 
 give rise to any permanent symptoms, provided the internal capsule be not injured.] 
 
 Fig. 439. 
 
 Septum luoldum. 
 Columnae fomiois. 
 
 Corpus striatum. 
 S triii terniinalis 
 Thalamus opticus 
 
 Cornu antlcum. 
 
 Ca:'u t nuclei caudati 
 
 Capstila interna 
 (anterior limb), 
 Capsula externa. 
 Island of ftell. 
 
 Nucleus lentil ormia. 
 Claustram. 
 
 Capsula Interna 
 (posterior limb). 
 Thalamus optioua 
 
 Corpus ganioula- 
 lum mediate. 
 
 Caudate nucleus 
 
 Hlppwaunpus. 
 
 Human brain, with the hemispheres removed by a horizontal incision on the right side. 4, trochlear; 8, acoustic 
 nerve ; 6, origin of the abducens ; F, A, L, position of the pyramidal (motor) fibres fur the face, arm, and leg; 
 S, sensory fibres. 
 
 Destruction of the internal capsule, however, causes paralysis of motion or 
 sensibility, or both, on the opposite side of the body, according to the part of 
 it which is injured. • The corpus striatum is quite insensible to painful stimulation 
 (Longef). 
 
THE INTERNAL CAPSULE. 735 
 
 Pathological. — In man, a lesion, not too small, destroying the anterior part of the corpus stri- 
 atum is followed by permanent paralysis of the opposite side provided the internal capsule is in- 
 jured, but the paralysis gradually disappears if the lenticular and caudate nucleus only are affected 
 (compare $ 365). Sometimes there is dilatation of the blood vessels in consequence of vasomotor 
 paralysis ($ 377) if the posterior part is injured [Nothnagel) ; redness and a slightly increased tem- 
 perature of the paralyzed extremities, at least for a certain time ; swelling or cedema of the ex- 
 tremities ; sweating ; anomalies of the pulse detectable by the sphygmograph ; decubitus acutus on 
 the paralyzed side ; abnormalities of the nails, hair, skin ; acute inflammations of joints, especially 
 of the shoulder. Later, contracture or permanent contraction of the paralyzed muscles takes place 
 (J/uguenin, Charcot). In some cases there is cutaneous anaesthesia, and occasionally enfeeblement 
 of the sense organs of the paralyzed side, and both when the posterior third or sensory crossway 
 of the posterior section of the internal capsule is affected. Usually, however, hemiplegia and hemi- 
 anmsthesia occur together. 
 
 Optic Thalamus. — Ferrier did not observe any movements to occur on 
 stimulating the optic thalami with electricity. As the pulvinar or posterior ex- 
 tremity of the optic thalamus is one of the parts connected with the origin of the 
 optic nerve, and is also connected by fibres with the cortex cerebri, it is probably 
 related to the sense of sight. Injury to the posterior third in man results in dis- 
 turbance of vision {Nothnagel). Ferrier surmises that the sensory fibres pass 
 through the optic thalami on their way to the cortex, so that when they are de- 
 stroyed insensibility of the opposite half of the body is produced. Removal of 
 the optic thalamus, or destruction of the part in the neighborhood of the inspira- 
 tory centre in the wall of the third ventricle, influences the coordinated move- 
 ments in the rabbit (Christiani). 
 
 We know very little definitely as to the functions of these organs. After injury to one thalamus 
 there has been observed enfeeblement or paralysis of the muscles of the opposite side, together with 
 mouvements de manege, and sometimes hemianesthesia of the opposite side, with or without affec- 
 tions of the motor spheres, have been recorded. Extirpation of certain cortical areas (rabbit) is 
 followed by atrophy of certain parts of the thalamus (v. Monakow). 
 
 .[Internal Capsule. — In connection with the functions of the basal ganglia, it is 
 most important to remember their relation to the internal capsule. The corpus stri- 
 atum consists of an intra-ventricular part, the caudate nucleus; and an extra-ventric- 
 ular part, the lenticular nucleus. The lenticular nucleus consists of three parts, best 
 seen in a vertical section (Fig. 440, 1, 2, 3), with white matter between them, 
 the stria medullares. The anterior limb of the internal capsule sweeps between 
 the caudate and lenticular nucleus, while the posterior segment lies between the 
 optic thalamus and the lenticular nucleus (Fig. 440). External to the first divi- 
 sion of the lenticular nucleus is the external capsule (Figs. 439, 440), whose 
 function is unknown. External to this is the claustrum, whose function is also 
 unknown. It is evident that hemorrhage into or about the basal ganglia is apt to 
 involve the fibres of the internal capsule. [When the lenticulo-striate artery, or, 
 as it is called, the "artery of hemorrhage" (Fig. 433, aSL), ruptures, it may 
 destroy not only the lenticular nucleus, but the internal capsule will be compressed, 
 and the same is the case with the lenticulo-optic artery ; the external capsule will 
 tend to force the blood inward. We know that in the posterior segment of 
 the capsule the volitional or pyramidal fibres lie in the following order from before 
 backward, those for the face (and tongue) in the knee, in the anterior third those 
 for the arm and hand, and in the middle third for the leg, and, perhaps, behind 
 these those for the trunk (Fig. 439, F, A, L) ; so that a very small lesion in this 
 region will affect a large number of these fibres, converging as they do, like the 
 rays of a fan, from the motor cortical areas, where the arrangement of these cen- 
 tres is a supero-inferior one (Fig. 433), to become an antero-posteriorone in the 
 knee and posterior limb of the internal capsule (Fig. 439). The posterior third 
 of this limb is sensory and is the " sensory crossway." 
 
 [Horsley points out that hemorrhage from the lenticulo-striate artery affects in order the muscles 
 of the face, arm, leg and trunk, while recovery is in the inverse order.] 
 
736 
 
 PEDUNCLE AND PONS. 
 
 Pedunculi Cerebri. — Injury to one cerebral peduncle causes, in the first place, 
 violent pain and spasm of the opposite side, while the blood vessels on that side 
 contract and the salivary glands secrete. These phenomena of irritation are fol- 
 lowed by paralytic symptoms of the opposite side, viz., anaesthesia (§365) and 
 paresis, or incomplete voluntary control over the muscles, as well as paralysis of 
 
 Fig. 440. 
 
 Nucleus caudatus. 
 
 Corpus callosum. 
 Pillars of the fornix. 
 
 Internal capsule. 
 Optic thalamus. - 
 
 Soft commissure. 
 
 Externalcapsule. — - 
 
 Claustrum. 
 
 Frontal section through the right cerebral hemisphere in front of the soft commissure (posterior surface of the section). 
 
 the vasomotor nerves. In affections of the cerebral peduncle in man, we must 
 remember the relation of the oculomotorius to it, as the latter is often paralyzed 
 on the same side {Nothnagel) [while the extremities, tongue, and half the face are 
 paralyzed on the opposite side from the lesion]. 
 
 Fig. 441. 
 
 Scheme of the fibres in the pons ; PT, 
 pyramidal tracts ; F, facial fibres ; 
 w, upper, /, lower lesion; MO, 
 medulla oblongata ; DP, decussa- 
 tion of pyramids. 
 
 The middle third of the crusta of the cerebral peduncle (Fig. 
 435) includes the direct pyramidal tracts (gg 365, 378). The 
 fibres of the inner third connect the frontal lobes, through the 
 superior cerebellar peduncles, with the cerebellum. In the outer 
 third are fibres which connect the pons with the temporal and 
 occipital cerebral lobes (Flechsig). The fibres which pass from 
 the tegmentum into the corona radiata conduct sensory impulses 
 {Flechsig). 
 
 Pons Varolii. — Stimulation or section of the pons 
 causes pain and spasms ; after the section there may 
 be sensory, motor and vasomotor paralysis, together 
 with forced movements. For diagnostic purposes in 
 man, it is important to observe if alternate hemiplegia 
 be present (Nothnagel.) 
 
 [In lesions situated in the lower half of one side of the pons 
 there is facial paralysis on the same side as the lesion and paraly- 
 sis (motor and sensory, and more or less complete) on the oppo- 
 site side of the body ; this is called alternate paralysis ; while, 
 if the lesion be in the upper half of one side of the pons, the 
 facial paralysis is on the same side as the paralysis of the body. 
 But the parts supplied by the 5th and 6th nerves may also be 
 
STIMULATION OF THE CORPORA QUADRIGEMINA. 737 
 
 involved. This is explained by Fig. 441, where the upper facial fibres cross in the pons. Sudden 
 and extensive lesions of the pons are often associated with hyperpyrexia, the temperature often 
 rising rapidly within an hour, perhaps from the gray matter in the floor of the 4th ventricle being 
 affected ; but whether it is due to some effect on a heat- regulating or heat-producing centre is un- 
 certain. Tumors of considerable size may press on the pons without producing very marked 
 symptoms, as tumors tend to push aside tissues, unless they be infiltrating in their character. 
 Lesions of the transverse superficial fibres (middle cerebellar peduncles) often give rise to 
 involuntary forced movements, there being a tendency to move to one side or the other.] 
 
 The Corpora Quadrigemina. — Destruction of these bodies on one side 
 in mammals, or their homologues, the optic lobes in birds, amphibians and 
 fishes, causes actual blindness, which may be on the same or the opposite side, 
 according to the relation of the fibres crossing at the optic chiasma (§ 344). 
 Total destruction causes blindness of both eyes. At the same time, the reflex 
 contraction of the pupil, due to stimulation of the retina with light, no longer 
 takes place (Flourens), where the optic is the afferent and the oculomotorius the 
 efferent nerve (§ 345). If the cerebral hemispheres alone be removed the pupil 
 still contracts to light, as well as after mechanical stimulation of the optic nerve 
 (If. Mayo). Destruction of the corpora quadrigemina interferes with the com- 
 plete harmony of the motor acts ; disturbance of equilibrium and incoordination 
 of movements occur (Serres). In frogs, Goltz observed not only awkward, 
 clumsy movements, but at the same time the animals have to a large extent lost 
 the power of completely balancing the body (p. 705). A similar result was 
 observed in pigeons (M Kendrick) and rabbits (Ferrier). Extirpation of the eye- 
 ball is followed by atrophy of the opposite anterior corpus quadrigeminum 
 ( Gudderi). 
 
 According to Bechterew, the fibres of one optic tract pass through the anterior brachium (Fig. 
 439) into the anterior pair (nates) of the corpora quadrigemina ; while those fibres which cross in 
 the chiasma (Fig. 381) pass into the posterior pair (testes). According to this arrangement we 
 have partial blindness, according as one or other pair of these bodies is destroyed. 
 
 [In man very little is known regarding the effects of disease of the corpora quadrigemina, inter- 
 ference with the ocular muscles being the most marked symptom, but the incoordination of move- 
 ment which has been observed may be due to pressure upon the superior cerebellar peduncle, while 
 it is by no means certain that the defects of vision are directly due to lesions of these bodies.] 
 
 Stimulation of the Corpora Quadrigemina. — The corpora quadrigemina react to electrical, 
 chemical and mechanical stimuli. The results of stimulation are very variously stated. Accord- 
 ing to some observers there is dilatation of the pupil on the same side ; according to Ferrier, it may 
 be the pupil on the opposite or on the same side. The stimulation may be conducted from the cor- 
 pora quadrigemina to the medulla oblongata, and to the origin of the sympathetic, for after section 
 of the sympathetic nerve in the neck dilatation of the pupil no longer takes place (ICnoll). Accord- 
 ing to Knoll, the contraction of the pupil observed by the older experimenters occurs only when 
 the adjoining optic tract is stimulated. Stimulation of the right anterior corpus quadrigeminum 
 causes deviation of both eyes to the left (and conversely) ; on continuing the stimulation, the head 
 is turned to this side. On dividing the corpora quadrigemina by a vertical median incision, stimu- 
 lation of one side causes the result to take place only on one side (Adamuk). Ferrier observed 
 signs of pain on stimulating these organs in mammals. Carville and Duret conclude from their 
 experiments that these organs are centres for the extensor movements of the trunk. Ferrier found, 
 on stimulating one optic lobe in a pigeon, dilatation of the opposite pupil, turning of the head 
 toward the other side and backward, movement of the opposite wing and leg; strong stimulation 
 caused flapping movements of both wings. Danilewsky, Ferrier and Lauder Brunton observed a 
 riae of the blood pressure and slowing of the heart beat, together with deeper inspiration and 
 expiration. According to Valentin and Budge, stimulation also causes movement of the intestines 
 and bladder, perhaps, excited secondarily by the action of the vasomotor nerves. 
 
 Bechterew ascribes all the phenomena, except those of vision itself, which accompany injury or 
 stimulation of these bodies, to affections of deeper-seated parts. He asserts that the corpora quad- 
 rigemina contain neither the centre for the movements of the pupils nor that for the combined 
 movements of the eyeballs; not even the centre for maintaining the equilibrium of the body. 
 Stimulation of these bodies causes the animals to perform marked movements. Reflex phenomena, 
 nystagmus, forced movements and unsteadiness of the gait only occur, however, when the deeper 
 parts are injured. 
 
 Pathological. — Lesions of the anterior pair in man, according to the extent of the lesion, cause 
 disturbance of vision, failure of the pupil to contract to light, and even blindness ; there may be 
 paralysis of the oculomotorii on both sides. Disease of the posterior pair may be associated with 
 disturbances of coSrdination (Nothnagel). 
 
 47 
 
738 FOKCED MOVEMENTS — STRABISMUS AND NYSTAGMUS. 
 
 Forced Movements. — It is evident from what has been said regarding the 
 importance of the corpora quadrigemina for the harmonious execution of move- 
 ments, that unilateral injury of such parts as are connected to them by conduct- 
 ing channels must give rise to peculiar unilateral disturbance of the equilibrium, 
 causing variations from the symmetrical movements of both sides of the body. 
 These movements are called forced movements. To this class belong the mouve- 
 ment de manege, where the animal, instead of moving in a straight line, runs 
 round in a circle ; index movements, where the anterior part of the body is 
 moved round the posterior part, which remains in its place, just like the move- 
 ments of an index round its axis ; and rolling movements, when the animal rolls 
 on its long axis. All these forms of movement may pass into each other, and 
 they are, in fact, merely different varieties of the same kind of movement. The 
 parts of the nervous system whose injury produces these movements are the corpus 
 striatum, optic thalamus, cerebral peduncle, pons, middle cerebellar peduncles, 
 and certain parts of the medulla oblongata. Eulenberg observed index move- 
 ments in the rabbit after injury to the surface of the brain, and Bechterew 
 observed the same in dogs. Forced movements, together with nystagmus and 
 rotation of the eyeballs, are caused by injury to the olives {Bechterew). The 
 statements of observers vary as to the direction and kind of movement produced 
 by injuring individual parts. The following observations have been made : Sec- 
 tion of the anterior part of the pons and of the crura cerebelli causes index, 
 or, it may be, rolling movements toward the other side ; section of the posterior 
 part of the same regions causes rolling movements toward the same side, while 
 the same result is caused by a deeper puncture into the tuberculum acusticum, or 
 into the restiform body. Section of one cerebral peduncle causes mouvements 
 de manege, while the body is curved with the convexity toward the same side. 
 The nearer to the pons the section is made the smaller is the circle described ; 
 ultimately index movements occur. Injury to one optic thalamus produces results 
 similar to puncture of the anterior part of the cerebral peduncle, because the 
 latter is injured along with it at the same time. Injury to the anterior part of one 
 optic thalamus causes the opposite kind of forced movement, viz., with the con- 
 cavity of the body toward the injured side. Injury to the spinal portion of the 
 medulla oblongata is followed by bending of the head and vertebral column, with 
 the convexity toward the injured side, along with movements in a circle. When 
 the anterior end of the calamus and the part above it are injured, the movements 
 are toward the sound side. 
 
 Strabismus and Nystagmus. — Among the forced movements may be reck- 
 oned deviation of the eyeballs, strabismus or squinting, and involuntary oscillation 
 of the eyeballs, constituting nystagmus. The latter condition occurs after superfi- 
 cial lesions of the restiform body, as well as of the floor of the 4th ventricle. A 
 unilateral deep transverse injury, from the apex of the calamus upward as far as 
 the tuberculum acusticum, causes the eye of the same side to squint downward and 
 forward, that of the other side backward and upward. Section of both sides causes 
 this condition to disappear (Schwahn). Hence, Eckhard assumes that the me- 
 dulla oblongata is the seat of an apparatus controlling the movements of the eyes 
 {Eckhard). 
 
 In pathological degeneration of the olivary body of the medulla oblongata in man, Meschede ob- 
 served intense rotatory movements toward the same side. 
 
 Theory. — In order to explain the occurrence of forced movements, it is suggested that there is 
 unilateral incomplete paralysis (Lafarque), so that the animal in its efforts to move onward leaves 
 the paralytic side slightly behind ther other, and hence there is a variation from the symmetry of the 
 movements. Brown-Sequard regards the matter in exactly an opposite light, viz., as due to stimu- 
 lation from injury causing an excessive activity of one-half of the body. Henle ascribes the move- 
 ments to vertigo, or a feeling of giddiness caused by the injury. In all operations on the central 
 nervous system, where the equilibrium is deeply affected, there is a considerable increase in the 
 number and depth of the respirations (Landois). 
 
 Other Effects. — Some observers noticed variations of the blood pressure and a change in the 
 
STRUCTURE AND FUNCTIONS OF THE CEREBELLUM. 739 
 
 number of heart beats after stimulation of the cortex cerebri, e.g., after electrical stimulation of the 
 motor areas for the extremities {Bochefontaine). Balogh observed acceleration of the pulse on 
 stimulating several points on the cortex cerebri of the dog, and from one point slowing of the pulse. 
 Eckhard stimulated the surface of the brain in rabbits, and as a rule he observed that as long as sin- 
 gle crossed movements occurred in the anterior extremities there was no effect upon the heart, but 
 that the heart became affected as soon as other movements occurred. This consists in slow, strong 
 pulse beats, with occasional weaker beats, while at the same time the blood pressure is slightly in- 
 creased {Bochefontaine). If the vagi be divided beforehand, the effect upon the pulse disappears, 
 while the increase of the blood pressure remains. That psychical processes affect the action of the 
 heart was known to Homer and Cbrysipp. Bochefontaine and Lepine, on stimulating several points, 
 especially in the neighborhood of the sulcus cruciatus in a dog, observed increased secretion of 
 saliva, slowing of the movements of the stomach, peristalsis of the intestine, contraction of the 
 spleen, of the uterus, of the bladder, and increased respirations. Bufalini, on stimulating those parts 
 of the cortex which cause movements of the jaw, observed the secretion of gastric juice with in- 
 crease of the temperature of the stomach. Schiff, Brown-Sequard, Ebstein, Klosterhalfen, and 
 others, have observed that injury to the pons, corpus striatum, thalamus, cerebral peduncle, and 
 medulla oblongata often causes hypersemia and hemorrhage into the lung (according to Brown- 
 Sequard, especially after injury to one side of the pons, which affects the opposite lung), under the 
 pleura, in the stomach, intestine, and kidneys. Gastric hemorrhage is common after injury to the 
 pons just where the cerebral peduncles join it. Similar phenomena have been observed in man after 
 apoplexy or cerebral hemorrhage. 
 
 Specially interesting is the cerebral unilateral decubitus acutus described by Charcot, which 
 always occurs on the paralyzed side of the body, i.e., on the side opposite to the cerebral injury. It 
 begins on the second or third day, rapidly causes enormous destruction and sloughing of the tissues 
 on the back and lower extremities, and death soon takes place. The decubitus which occurs after 
 spinal injuries usually begins in the middle line of the buttocks, and extends symmetrically on both 
 sides. In cases of unilateral injury to the spinal cord the decubitus occurs on the corresponding side 
 of the sacral region (p. 614). 
 
 [Corpus Callosum. — It is usually stated that the corpus callosum connects the convolutions of 
 one side of the brain with those of the other, i.e., it is an inter-hemispherical commissure. D.J. 
 Hamilton, however, states that it is not an inter-hemispheric commissure, but is due to cortical fibres 
 coming from the cortex cerebri to be connected with the basal ganglia of the opposite side. On this 
 view, the " corona radiata," as usually understood, consists only of the fibres which pass from the 
 cerebral peduncle directly up to the cortex on the same side, and are contained in the posterior di- 
 vision and knee of the internal capsule. They correspond to the motor pyramidal tracts. Hamilton \ 
 maintains that all the other fibres of the internal capsule pass into the crossed callosal tract, and, I 
 instead of running directly up to the cortex on the same side, cross in the corpus callosum to the » 
 cortex of the opposite side. Beevor, relying on the examination of the brain of monkeys, by Wei 
 gert's method, denies that any fibres of the corpus callosum pass into the external or internal cap- 
 sules, and he maintains the old view that the corpus callosum is a commissure between the two hemi- 
 spheres.] 
 
 380. STRUCTURE AND FUNCTIONS OF THE CEREBELLUM.— [Structure. 
 — On examining a vertical section of a cerebellar leaflet we observe the following microscopic ap- 
 pearances : Externally is the pia mater with its blood vessels (Fig. 442, a) which penetrate into the 
 gray matter, within is the medulla composed of white fibres. The gray matter consists of b, a 
 broad outer or molecular layer largely composed of branched fibrils, and internal to it is d, the 
 "granular," nuclear, or rust-colored layer. On the boundary line between these two is the layer of 
 Purkinje's cells, c. The cells of Purkinje form a single layer of large, multipolar, flask-shaped nerve 
 cells, which have been compared to the branched antlers of a stag. From their outer surface is 
 given off a process which rapidly divides and gives rise to a large number of smaller processes running 
 outward in the outer gray layer. Some of these processes form part of the ground plexus of fibrils 
 in this layer. An unbranched axial cylinder process is sent inward to the granular layers, where it 
 becomes continuous with a nerve fibre. Every cell of Purkinje being continuous with a straight, 
 unbranched medullated nerve fibre. The unbranched fibres run straight from the medulla through 
 the granular layer, forming no connection with its granules. A second set of branched or anasto- 
 mosing, often varicose, nerve fibres finer than the foregoing pass from the medulla into the granular 
 layer, where they form a network which is continued into the molecular layer. The granular 
 layer is composed of closely-packed granules of two kinds, one is stained by haematoxylin and the 
 other with eosin (Denissenko). The hsematoxylin-stained cells are most numerous, and consist of a 
 nucleus surrounded by protoplasm, and they are what were formerly called granules. The eosin- 
 stained cells [which are also stained by nigrosin {Beevor)] are interposed in the course of medul- 
 lated nerve fibres. The haematoxylin cells, called glia cells by Beevor, have processes and form a 
 network throughout the granular layer, which also extends into the molecular layer. This network 
 is regarded as the continuation of the modified myelin of the nerve fibres, and it forms a capsule for 
 the cells of Purkinje. The molecular layer consists of a ground substance, composed of a spongy 
 network of fine fibrils which seem to be of the nature of neuro-keratin, strengthened here and there 
 by stronger fibres. In the meshes lies a homogeneous substance. Some of this substance is more 
 
 ie » 
 
F40 
 
 FUNCTIONS OF THE CEREBELLUM. 
 
 condensed to form a limitans externa on the surface of the cerebellum, while on the boundary line 
 next the granular layer the branches of the glia cells form a limitans interna, and between the two 
 stretches the neuro-keratin network. Some small variocose nerve fibres exist in this layer continuous 
 with those in the granular layer. The branched process of the cells of Purkinje is fibrillated, 
 and the finer processes are composed also of fibrils, which are gradually distributed until they be- 
 come isolated. It is suggested by Beevor that these fibrils bend at a right angle in a plane parallel 
 to surface, and rearrange themselves as fibres surrounded by a medullated sheath, and that these 
 fibres run inward through the molecular and granular layers — as the branched fibres — to the 
 medulla.] 
 
 Fig. 442. Fig. 443. 
 
 Pigeon with its cerebellum removed. 
 
 Function. — Injuries of the cerebellum 
 cause disturbances of the equilibrium of 
 the body. Most probably the cerebellum 
 is a great and important central organ for 
 the finer coordination and integration of 
 movements. The fact that it is connected 
 with all the columns of the spinal cord, 
 with the central ganglia of the corpora 
 quadrigemina, and cerebrum, renders this 
 very probable. The direct cerebellar 
 tracts from the lateral column of the cord 
 conduct sensory impressions to the cere- 
 bellum, and thus indicate the posture of 
 the trunk. The cerebellum may affect 
 the motor nerves of the cord through 
 fibres which pass downward in the lateral 
 columns of the cord from the restiform 
 bodies (Flechsig). Injury of the cere- 
 bellum produces neither disturbance of the 
 psychical activities, nor does it interfere 
 with the will or consciousness. Injuries to 
 the cerebellum itself do not give rise to pain. 
 
 According to Schiff, the cerebellum does not actually regulate the coordination of movements. 
 According to him there is a mechanism on both sides of the middle line, which increases all the 
 complicated muscular movements ; not only those for powerful contractions, but also the peculiar 
 fine movements which fix the limbs and joints. Luciani asserts that destruction of the cerebellum 
 produces a condition of incomplete tonus, there being a want of energy to control the voluntary 
 muscles. Each half of the organ acts on both halves of the body. 
 
 Removal of Cerebellum. — The immediate results produced by injury to or 
 removal of the cerebellum have been admirably described by Flourens (Fig. 443). 
 On removing the most superficial layers in a pigeon, the animal merely showed 
 signs of weakness and interference with the uniformity of its movements. On 
 
 'Vertical section of the cerebellum, a, pia mater; b, 
 external layer ; c, layer of Purkinje's cells ; d, inner 
 layer ; e, medullary white matter. 
 
EXTIRPATION OF THE CEREBELLUM. 741 
 
 removing more of cerebellum, the animal became greatly excited, and made violent 
 irregular movements, which did not partake of the character of convulsions. The 
 sensorium was unaffected, while vision and hearing were intact. Coordinated 
 movements, such as walking, flying, springing and turning, could be executed but 
 imperfectly. After removal of the deepest layers, the power of executing the above- 
 named movements was completely abolished. On placing the pigeon on its back, it 
 could not get on its legs ; at the same time it made continually the greatest exertions 
 in its movements, but these were always incoordinated, and therefore without any 
 satisfactory result. The will, intelligence, and perception remained intact ; the 
 animal could see and hear, sought to avoid obstacles placed in its way ; it gradu- 
 ally exhausted itself in fruitless efforts to get on its legs, and ultimately remained 
 in its abnormal position quite exhausted. Flourens concluded from these experi- 
 ments that the cerebellum is the centre for coordinating voluntary movements. 
 Lussana and Morganti regard the cerebellum as the seat of the muscular sense. 
 
 [Extirpation in Mammals. — The dangers attending this operation are so great that but few 
 animals survive. Luciani, however, by using antiseptic and other precautions, has been able to do 
 this so that complete cicatrization was obtained, the animal (young bitch) being restored to health 
 for a few months. The cerebellum alone was removed, but not its peduncles. As in all other 
 similar operations, we must distinguish sharply the phenomena manifested during recovery from 
 those after complete recovery. During the first period of six weeks, from the time of the operation 
 until complete recovery, the symptoms are those of injury and irritation of the divided peduncles, 
 along with those resulting from the removal of the organ. They are clonic contractions of the 
 . muscles of the fore limb, neck and back, passing into tonic contractions when the animal attemps 
 to move, and also weakness of the hind legs, so that all the normal voluntary movements are inter- 
 fered with, i.e., incoordinated, although these symptoms may be explained by the injury to adjoin- 
 ing parts. There was no sensory disturbance or loss of the muscular sense, although closing the 
 eyes rendered standing impossible. As recovery takes place these symptoms disappear, and the 
 animal enters on the second period, where the symptoms depending on the actual loss of the organ 
 are pronounced. The contracture and pseudo-paralytic weakness disappear, while there are altera- 
 tions in the tone of the individual muscles, producing a sort of " cerebellar ataxy." The dog 
 could swim in quite a normal manner, its power of equilibration was not interfered with, but acts 
 requiring a greater development of muscular energy could not be properly executed. This period 
 lasted four to five months. After this time its health gave way, there was otitis, conjunctivitis, 
 articular and cutaneous inflammations, while a peculiar form of marasmus set in, the animal dying 
 after eight months. In fishes, also, the removal of the cerebellum does not affect their power of 
 locomotion (Bandelet).] 
 
 Duration of the Phenomena. — After superficial lesions, or after a deep 
 incision, the disturbances of coordination soon pass away {Flourens). If the 
 injury affects the lowest third of the cerebellum, the motor disturbances remain 
 permanently. Symmetrical lesions do not disturb coordination (Schiff). After 
 removing the greater portion of the cerebellum in birds, Weir Mitchell has 
 observed that the original disturbances gradually disappear ; and after months 
 only slight weakness and a condition of rapid fatigue remain. 
 
 In the dog, superficial injuries of the vermiform process, or of one-half of the organ, produce 
 merely temporary disturbances ; while deep injuries to the vermiform process, or removal of one 
 hemisphere and a part of the vermiform process, cause permanent rigidity of the legs and shaking 
 of the head ; if the worm and both halves are destroyed, there follows permanent pronounced dis- 
 turbance of coordination (v. Mering). According to Baginsky, destruction of a large part of the 
 vermiform process alone causes in mammals permanent disturbance of coordination. Ferrier found 
 that a vertical section of the cerebellum in monkeys produced only inconsiderable disturbances of 
 equilibrium ; after injury of the anterior part of the middle lobe the animal often tumbles forward, 
 while, when the posterior part is injured, it falls backward. After injury of the lateral lobe the 
 animal is drawn toward the affected side (Schiff, Vulpian, Ferrier, Hitzig). If the middle com- 
 missure be injured the animal rolls violently on its long axis toward the injured side .(Magendie). 
 Paralysis never occurs after injuries of the cerebellum, nor is there ever disturbance of sensation or 
 of the sense of touch. Luciani found that mirasmus ultimately set in in animals with the cere- 
 bellum extirpated. In frogs an important organ concerned with motion lies at the junction of the 
 oblongata with the cerebellum [Eckhard). After it is removed the animal can no longer execute 
 coordinated jumping movements, nor can it crawl (Goltz). 
 
 [In man the cerebellum is connected with the maintenance of the equilibrium. There may be 
 a lesion of the hemispheres without any marked symptoms, but if the middle lobe be injured or 
 
742 
 
 PROTECTIVE APPARATUS OF THE BRAIN. 
 
 pressed on by a tumor there is usually a reeling or staggering gait like that of a drunken man. 
 Ross points out that if the tumor ajfect the upper part of this lobe the tendency is to fall backward, 
 and if in the lower part, to fall forward or to revolve round a horizontal axis. Vomiting is fre- 
 quently persistent and well-marked, while there may be nystagmus and tonic retraction of the 
 head.] 
 
 After injuries of the cerebellum, involuntary oscillations of the eyeballs or nystagmus, as welt as 
 squinting (Magendie, Hertwig), have been observed ; while Ferrier observed movements of the 
 eyeballs after electrical stimulation. According to Curschmann, Eckhard and Schwahn, this occurs 
 only when the medulla oblongata is involved ($ 379). 
 
 Effects of Electricity and Vertigo.— If an electrical current be passed through the head, by 
 placing the electrodes in the mastoid fossae behind both ears, with the + pole behind the right and 
 the — pole behind the left ear, then on closing the current there is severe vertigo and the head 
 and body lean to the + pole, while the objects around seem to-be displaced to the left. If the 
 eyes be closed while the current is passing, the movements appear to be transferred to the person 
 himself, so that he has a feeling of rotation to the left {Purkinje). At the moment the head leans 
 toward the anode the eyes turn in that direction, and often exhibit nystagmus. The electrical cur- 
 rent probably stimulates the nerves of the ampullae, as we know that affections of these bodies 
 cause vertigo (g 350). . The cerebellum has no relation to the sexual activities, as was maintained 
 by Gall. The contractions of the uterus observed by Valentin, Budge and Spiegelberg, after 
 stimulation of the cerebellum, are as yet unexplained. 
 
 Pathological. — Lesions of one hemisphere may give rise to no symptoms, but if the middle lobe is 
 involved there is incoordination of movement, especially a tendency to fall, unsteady gait and pro- 
 
 Fig. 444. 
 
 mm h 
 
 mm mm 
 
 Vertical section of the cortex cerebri and its membranes ; X i'A- <"«, cortex cerebri ; *, intima piae dipping into the 
 sulci ; a, arachnoid, connected with/ by means ot the loose subarachnoid trabecular in the subarachnoid space, 
 sa ; v, v, blood vessels : d, dura ; and sd t subdural space. 
 
 nounced vertigo. Irritative lesions of the middle peduncle cause complete gyrating movements of 
 the body around its axis, together with rotation of the eyes (Nonal) and head (Notknagel). 
 
 381. PROTECTIVE APPARATUS OF THE BRAIN.— The Membranes.— The 
 dura mater cerebralis is intimately united to the periosteum of the cavity of the skull, while the 
 spinal dura mater forms around the spinal cord a freely suspended long sack, fixed only on its ante- 
 rior surface. It is a fibrous membrane, consisting of firm bundles of connective tissue intermixed 
 with numerous elastic fibres, and provided with flattened connective- tissue corpuscles and Waldeyer's 
 plasma cells. The smooth inner surface is covered with a layer of endothelium. It is but slightly 
 supplied with blood vessels, although they are more numerous in the outer layers ; the lymphatics 
 are numerous, while nerves whose terminations are unknown give to the dura its exquisite sensi- 
 bility to painful operations on it. Pacinian corpuscles have been found in the dura over the tem- 
 poral bone. The lymphatic subdural space {Key and Retzius) lies between the dura and the 
 arachnoid, and between the pia and arachnoid is the subarachnoid space (Fig. 444). These two 
 spaces do not communicate directly. The delicate arachnoid, thin and partially perforated, poor in 
 blood vessels and without nerves, is covered on both surfaces with squamous endothelium. Only 
 on the spinal "cord is it separated from the pia, so that between the two lies the lymphatic sub- 
 arachnoid space; over the brain the two membranes are for the most part united together, except 
 the parts bridging over the sulci between adjacent convolutions. The arachnoid passes from convo- 
 lution to convolution without dipping into the sulci, while the pia dips into each sulcus (Fig. 444, a). 
 f\ The ventricles of the brain communicate freely with the lymphatic subarachnoid space, but not 
 
THE MOVEMENTS OF THE BRAIN. 743 
 
 with the subdural space [Waldeyer and Fischer). The pia consists of delicate bundles of con- J 
 nective tissue without any admixture of elastic fibres; it is richly supplied with blood vessels and * 
 lymphatics, and carries nerves which accompany the blood vessels into the substance of the brain 
 (JColliker). The lymphatics open into the subarachnoid space (§ 196). . 
 
 [Subarachnoid Fluid, or cerebro spinal fluid, lies in the subarachnoid space, which is traversed \ 
 by trabeculse of connective tissue. Within the brain are a series of cavities called ventricles, 
 which communicate one with another in a definite way. The fourth ventricle is lined by a laye*r 
 of columnar epithelium, and covered in dorsally by a membrane and continuation of the pia mater, 
 from the middle of which there hangs into the roof of the fourth ventricle two vascular processes 
 composed of capillaries — the choroid plexuses of the fourth ventricle, which are comparable to the 
 larger plexuses of the lateral ventricles. In this membrane is the foramen of Magendie and two I 
 other smaller foramina, whereby the fluid in the subarachnoid space communicates - with that in the I 
 fourth, ventricle ; but the lymphatics of the nerve sheaths can be injected from the subarachnoid 
 space, so that there is direct continuity of the fluid in the ventricles of the brain with that in sub- 
 arachnoid space, perivascular spaces of the cerebral substance, and the perineural lymphatics of 
 nerves. The average quantity is about 2 ounces, and if it be suddenly withdrawn epilepsy or 
 convulsions may be produced, or if it be rapidly increased in amount coma maybe produced. . The 
 middle and posterior parts of the brain and the medulla oblongata do not rest directly on bone, 
 but are separated by a distinct interval from their osseous case, an interval occupied by the cerebro- 
 spinal fluid and traversed by trabeculse, so that, as Hilton expresses it, this fluid forms a perfect 
 water bed for those parts, being sustained by the venous circulation and the elasticity of the dura. 
 It has important mechanical functions protecting delicate parts of the brain from injury ; by dis- 
 tributing vibratory impulses it insulates the nerve roots and has important relations to the quantity 
 of blood in the brain and the cerebral circulation (Chemical Composition, \ 198).] 
 
 [Spina Bifida. — Sometimes the laminae of the vertebrae in the lumbar or other region of the 
 spinal column are imperfectly developed, in which case the membranes project through as a tumor 
 distended by cerebro-spinal fluid and covered by skin. The effects of rapid tapping or compressing 
 the sack are readily studied in such cases.] 
 
 The Pacchionian bodies, or granulations, are connective-tissue villi, which serve for the out- 
 flow of lymph from the subdural and subarachnoid spaces into the sinuses of the dura mater, espe- 
 cially the longitudinal sinus. The subarachnoid space also communicates with the spaces in the 
 spongy bone of the skull, and with the veins of the skull and surface of the face [Kollmann). 
 The subdural space also communicates with the lymphatic spaces in the dura, while the latter com- 
 municate directly with the veins of the dura. Both the subdural and subarachnoid lymphatic 
 spaces communicate with the lymphatics of the nasal mucous membrane. The space outside the 
 dura of the spinal cord is called the epidural space, and may be regarded as lymphatic in its 
 nature ; the pleural and peritoneal cavities may be filled from it ; but it does not communicate with 
 the cavity of the skull ( Waldeyer and Fischer). The plexuses of blood vessels are surrounded by 
 undeveloped connective tissue. The tela; choroidese in the new-born are still covered with ciliated 
 epithelium. 
 
 The Movements of the Brain. — The pulsations of the large basal cerebral 
 vessels communicate their pulsatile movements (§ 79, 6) to the brain — the 
 respiratory movements also affect it, so that the brain rises during expiration 
 and sinks during inspiration. Lastly, there are slight alternating vascular eleva- 
 tions and depressions, occurring 2 to 6 times per minute, due to the periodic 
 dilatation and contraction of the blood vessels (§ 371). Psychical excitement 
 influences these, and they are most regular during sleep {Burckhardt, Mays). 
 The movements are best seen, especially where the membranes of the brain offer 
 little resistance, e.g., over the fontanelles in children, and where the membranes 
 have been exposed by trephining. The presence of the cerebro-spinal fluid is 
 most important for the occurrence of these movements, as it propagates the pres- 
 sure uniformly, so that every systolic and expiratory dilatation of the blood vessels 
 is concentrated upon those parts of the cerebral membrane which do not offer any 
 resistance {Donders). When the fluid escapes, the movements may almost dis- 
 appear. 
 
 Mental excitement increases the pulsations of the brain. At the moment of awaking, the amount 
 of blood in the brain diminishes ; sensory stimuli applied during sleep, so that the sleeper does not 
 awake, increase the amount of blood. As the arteries within the rigid skull case change their vol- 
 ume with each pulse beat, the veins (sinuses) exhibit at every beat a pulsatile variation in volume, 
 the opposite of that occurring in the arteries (Mosso). 
 
 The Cerebral Blood Vessels.— The blood vessels of the pia, of course, are regulated by the 
 vasomotor nerves (§ 356, A, 3), and their calibre may also be influenced by the stimulation of more 
 distant parts of the body (g 347). Donders trephined the skull so as to make a round hole, and 
 
744 
 
 THE GANGLIONIC CEREBRAL ARTERIES. 
 
 filled it with a piece of glass, so that with a microscope he could observe changes in the calibre of 
 the blood vessels. Paralysis of the vasomotor nerves and narcotics dilate the blood vessels ; they 
 become greatly contracted at death ({S 373, I). The blood vessels are dilated during cerebral 
 activity (| 100, A) as well as during sleep. Increased pressure within the skull causes great de- 
 rangement of the cerebral activity ; labored respiration (ji 368, B), unconsciousness even to coma, 
 and paralytic phenomena — all of which may, in part, be referable to disturbances of the circulation. 
 It all the cranial arteries be ligatured suddenly, there is immediate loss of consciousness, together 
 with strong stimulation of the medulla oblongata and its centres, and death takes place rapidly with 
 convulsions (compare $ 373). 
 
 By the free anastomosis which takes place at the base of the brain forming the circle of 
 Willis (Fig. 445), the individual parts of the brain are preserved from want of blood, when one or 
 other blood vessel is compressed or ligatured. Within the brain the arteries are distributed as 
 " terminal " arteries, i. e., the terminal branches of any one artery end in their own area, and do 
 not anastomose with those of adjoining areas (Cohnheim). On the other hand, the peripheral 
 
 Fig. 445. 
 
 Arteries of the base of the brain, or circle of Willis. C C, internal carotids ; C A, anterior cerebral ; S S, Sylvian ar- 
 teries ; V V, vertebrals ; B, basilar ; C P, posterior cerebrals ; i, 2, 3, 4, 4, 4, groups of nutrient arteries. The 
 dotted line shows the limit of the ganglionic area. 
 
 arteries (arteries of the corpus callosum, Sylvian fissure, and deep cerebral) which run externally on 
 the brain form free anastomoses ( Tichomirow). 
 
 [The nutrient or ganglionic arteries for the central ganglia arise in groups from the circle of 
 Willis, or from the first two centimetres of its trunks. The antero-median group ( 1) supplies the 
 anterior part of the head of the caudate nucleus. The postero-median (2} enter the posterior 
 perforated space and supply the internal surface of the optic thalami and the walls of the third 
 ventricle. The antero-lateral groups (3,3) from the middle cerebral enter the anterior perforated 
 space, supply the corpora striata, the anterior part of the optic thalamus, and the internal capsule. 
 These branches are apt to rupture. The postero-lateral (4, 4) supply a large part of the optic 
 thalami (Charcot). A line drawn at a distance of two centimetres outside the circle of Willis 
 encloses the ganglionic area. The cerebral convolutions are supplied by the large branches of 
 the circle of Willis. The anterior cerebral curves round the corpus callosum, and supplies the 
 gyrus rectus and the supraorbital, the first and second frontal convolutions, the upper part of the 
 ascending frontal, and the inner surface of the hemisphere as far as the quadrate lobule (Fig. 370, 
 I). The posterior cerebral goes to the region of the occipital lobe and the inferior aspect of the 
 
THE VENOUS CIRCULATION. 
 
 745 
 
 temporal lobe ; the middle cerebral or Sylvian artery divides into four branches, which go to the 
 posterior part of the frontal lobe, ascending frontal, and to all the parietal lobes, i. e., chiefly to the 
 motor areas (III), the angular gyrus, and to the first temporo-sphenoidal lobule. The terminal 
 branches of these ganglionic arteries do not anastomose with the cortical system. Fig. 446 shows 
 the ganglionic arteries piercing the basal ganglia. Obviously, when hemorrhage of the lenticulo- 
 striate artery or " artery of hemorrhage " (4, 4) occurs, it will compress the lenticular nucleus, or 
 tear it up, and may even injure the parts outside, such as the external capsule, claustrum (T), and 
 island of Reil (R), or those inside, e.g., the internal capsule.] 
 
 [Thus the anterior cerebral supplies the prefrontal area and a small part of the motor area, that 
 for the leg centre in the paracentral lobule and upper end of the ascending front (and perhaps for 
 the trunk). The posterior cerebral supplies the centre for vision, and that connected with the 
 course of the posterior part of the optic expansion, and also the sensory part of the internal capsule. 
 The middle cerebral supplies the motor areas of the cortex except part of the leg centre and the 
 basal ganglia, the auditory centre, and that for speech [Gowers).'] 
 
 [The cerebral circulation has many peculiarities. The curves on the arteries serve to modify 
 the effect of the cardiac shock; the circle of Willis permits within limits a free circulation, but in 
 as far as the skull is largely a rigid box, it was at one time taught that, as the brain substance and 
 its fluids were practically incompressible, it was impossible to alter the amount of blood in the 
 brain. This is a mistake. The amount of blood undergoes an alteration in this way, that when 
 
 Fig. 446. 
 
 Transverse section of the cerebrum behind the optic chiasma. Arteries of the corpus striatum. C k, optic chiasma ; 
 B, section of optic tract; L, lenticular nucleus ; I, internal capsule; C. caudate nucleus ; E, external capsule ; 
 T, claustrum ; R, convolutions of the island of Reil ; V V, section of the lateral ventricles ; P P, pillars of the 
 fornix ; O, gray substance of the third ventricle. Vascular areas — I, anterior cerebral artery ; II, Sylvian artery ; 
 III, posterior cerebral artery ; 1, internal carotid ; 2, Sylvian, 3, anterior cerebral artery ; 4, 4, lenticulo-striate 
 arteries ; 5, 5, lenticular arteries. 
 
 more blood passes in, some cerebro-spinal fluid moves out, and vice versa, so that there is an inti- 
 mate relation between these fluids. In the developing skull the cerebro-spinal fluid may accumulate 
 in large amount within the ventricles, and greatly distend both them and the yielding skull case 
 from internal pressure, as in acute hydrocephalus. The peculiarities and independence of the 
 cortical and ganglionic arteries have already been referred to. Plugging by means of a clot, 
 vegetation or wart carried from the heart is common in the left middle cerebral artery. Why ? 
 When the plug is washed away by the blood stream, owing to the left carotid springing from the 
 aorta nearly in line with the blood current, the plug readily passes into the carotid, and so into the 
 left middle cerebral, which is in line with the internal carotid. In such a case, the convolutions 
 and parts supplied by it are suddenly deprived of blood with immediate and serious results] 
 
 [The venous circulation is peculiar. The sinuses are really spaces between the layers of the 
 tough dura mater, and partly bounded by bone. The blood moves in the longitudinal sinus from 
 before backward, but most of the cortical veins open into it in a forward direction, so that their 
 stream is opposed to that in the sinus. Thus, the blood which enters the brain by ascending arteries 
 reaches the sinuses by ascending veins, the reverse of what obtains elsewhere, where ascending 
 veins convey blood from descending arteries, whereby the hydrostatic pressure and gravity aid the 
 circulation, but here gravitation is opposed to the flow of blood in the cerebral veins. This will 
 help to explain the occurrence of thrombosis in these vessels. Some of the veins on the surface 
 communicate with intracranial veins, e. g., those of the nose, the facial through the ophthalmic, 
 
 ll 
 
746 COMPARATIVE HISTORICAL. 
 
 mastoid veins and veins of the diplce. Hence, morbid processes affecting the scalp (erysipelas), 
 ear (caries), or face (carbuncle) may readily affect intracranial structures ( Gowers).'] 
 
 If a person who ha« been in bed for a long time, and whose blood is small in amount, be suddenly 
 lifted up into the erect position, cerebral anemia is not unfrequently produced, owing to hydrostatic 
 causes. At the same time there may be loss of consciousness and impairment of the senses. Lie- 
 bermeister regards the thyroid gland as a collateral blood reservoir which empties its blood toward 
 the head during such changes of the position of the body. Perhaps this may explain the swelling 
 of the thyroid as a compensatory act, when the heart beats violently and the brain is surcharged 
 with blood (§§ 103, III, and 371). Very violent muscular exertion, as well as marked activity of 
 other organs, cause a very considerable fall of ^the blood pressure in the carotid. 
 
 Pressure on the Brain. — The brain and the fluid surrounding it are constantly subjected to a 
 certain mean pressure, which must ultimately depend upon the blood pressure within the vascular 
 system. The investigations of Naunyn and Schreiber on the cerebral pressure (01 cerebro-spinal 
 pressure) showed that.the pressure must be slightly less than the pressure within the carotid before 
 the symptoms proper to pressure on the brain occur. These are sudden attacks of headache, with 
 vertigo, or it may be loss of consciousness, vomiting, slowing of the pulse, slow and shallow respi- 
 ration, convulsions — while the pressure of the cerebro-spinal fluid is increased. The cause of these 
 phenomena lies in the anaemia of the brain. If the pressure is moderate, the above-named symp- 
 toms may remain latent ; nevertheless, disturbances of the nutrition of the brain occur, with con- 
 secutive phenomena, such as persistent slight headache, feeling of vertigo, muscular weakness and 
 disturbances of vision (owing to neuro-retinitis with choked disk). Increase of the blood pressure 
 diminishes the symptoms, while diminution of the blood pressure causes more pronounced phe- 
 nomena of cerebro-spinal pressure. In the dog. pain begins with a pressure of 70 to 80 mm. Hg. 
 Consciousness is abolished when the pressure is higher, and at 80 to 100 mm. spasms take place. A 
 pressure of 100 to 120 mm. causes slowing of the pulse, owing to stimulation of the vagus at its 
 origin; the respirations are temporarily accelerated and then diminish. Long-continued severe 
 compression always, sooner or later, ends fatally. The blood pressure at first is increased, owing to 
 reflex stimulation of the vasomotor centre from the pressure stimulating the sensory nerves ; ulti- 
 mately the blood pressure falls and the pulse becomes very slow. Irregular variations in the blood 
 pressure point to a direct central stimulation of the vasomotor centre by pressure. The application 
 of continued, slowly-increasing pressure compresses the brain (Adamkiewicz). 
 
 382. COMPARATIVE— HISTORICAL.— Comparative. — Nerves are absent in the pro- 
 tozoa. Neuromuscular cells (g 296) occur in the ccelenterata, in the hydroida and medusae, and 
 they are the first indications of a nervous apparatus. The umbrella of the medusa is covered with 
 a plexus of nerve fibrils, which at various parts along its margin is provided with small cellular 
 thickenings corresponding to ganglia, and from these nerve fibres proceed to the sense organs. 
 Many of the worms possess a nervous ring in the cephalic portion, and in those provided with an 
 intestine a single or double nervous cord, in the form of a ring, surrounds the pharynx. Branches 
 (often two) pass from this into the elongated body, and usually these carry ganglia corresponding to 
 each ring of the body of the animal. In the leech only one gangliated cord is present. In the 
 echinodermata a large nerve ring surrounds the miuth, and from it large nerves proceed, corre- 
 sponding to the chief trunks of the water-vascular system. At the points where the nerves are given 
 off, the nervous ring is provided with the so-called " ambulacral brains." The arthropoda are 
 provided with a large cephalic ganglion placed above the pharynx, from which nerves pass to the 
 sense organs. Another ganglion lies on the under surface of the pharynx, and is connected with 
 the former by commissures. The pharynx is thus embraced by a gangliated ring, and from it pro- 
 ceed the abdominal gangliated double chain, along the ventral surface of the body, through the 
 thorax and abdomen. Sometimes several ganglia unite to form a large compound ganglion, while 
 in other cases each segment of the body contains its own ganglia. In the mollusca the oesopha- 
 geal nervous ring is present, although the ganglionic masses vary much in position within it. A 
 number of compound ganglia lie scattered in different parts of the body, and are united by nerves 
 to the former. They represent the sympathetic system. In the cephalopoda the oesophageal ring 
 has almost no commissure, and a part of the ganglionic matter is enclosed in a cartilaginous capsule, 
 and is often spoken of as a "brain." Additional ganglia are found in the mantle, heart and stomach. 
 In vertebrates the nervous system invariably lies on the dorsal aspect of the body. In the amphi- 
 oxus there is no separation into brain and spinal cord. (See \\ yjt, and 375.) 
 
 Historical. — Alkmaon (580 B.C.) placed the seat of consciousness in the brain; Galen (131-203 
 A.D.) regarded it as the seat of the impulses for voluntary movements. Aristotle (384 B.c) ascribed 
 the relatively largest brain to man; he stated that it was inexcitable to stimuli (insensible). One of 
 the functions he ascribed to the brain was to cool the heat ascending from the heart. Herophilus 
 (300 B.C.) gave the name calamus scriptorius, and he regarded the 4th ventricle as the most important 
 organ for the maintenance of life. Even in Homer there are repeated references to the dangers of 
 injuries of the neck. Aretaeus and Cassius Felix (97 a.d. ) were aware of the fact that lesion of 
 one cerebral hemisphere caused paralysis on the opposite side of the body. Galen was acquainted 
 with the path in the spinal cord connected with movement and sensation. Vesalius (lS4°) de- 
 scribed the five ventricles of the brain. R. Colombo (1559) observed the movements of the brain 
 
HISTORICAL. 747 
 
 isochronous with the action of the heart. A more careful description of these movements was 
 given by Riolan (1618). Coiter (1573) discovered that- an animal can live after removal of its 
 cerebrum. About the middle of the 17th century, Wepfer discovered the hemorrhagic nature of 
 apoplexy. Schneider (1660) estimated the weight of the brain in different animals. Mistichelli 
 (1709) and Petit (1710) described the decussation of the fibres of the spinal cord below the pons. 
 Gall discovered the partial origin of the optic nerve from the anterior pair of the corpora quadri- 
 gemina, and by dissecting the brain from below he attempted to trace the course of the nerve fibres 
 to the convolutions (1810). Rolando described more accurately the form of the gray matter of the 
 spinal cord. Carus (1814} discovered the central canal. The most compendious work on the brain 
 was written by Burdach (18 19-1826). The more recent observations are referred to. in the text. 
 
Physiology of the Sense Organs, 
 
 383. INTRODUCTORY OBSERVATIONS.— Requisite Condi- 
 tions. — The sense organs have the function of transferring to the sensorium im- 
 pressions of the various phenomena of the external world; they are, in fact, the 
 intermediate instruments of sensory perceptions. In order that this may occur, the 
 following conditions must be fulfilled: (1) The sense organ, provided with its 
 specific end organ, must be anatomically perfect, and capable of acting physio- 
 logically. (2) A " specific stimulus " must be present, which, under normal 
 conditions, acts upon the end organ. (3) The sense organ must be connected 
 with the cerebrum by means of a nerve, and the conduction through this path 
 must be uninterrupted. (4) During the act of stimulation, the psychical activity 
 (attention) must be directed to the process, and then the sensation results, e.g. , 
 of light or sound, through the sense organ. (5) Lastly, when by a psychical act 
 the sensation is referred to the external cause, then there is a conscious sensory 
 perception. Often, however, this relation is completed as an unconscious con- 
 clusion, as it is essentially a deduction from previous experience. 
 
 Stimuli. — With regard to the stimuli which are applied to the sensory apparatus, we distinguish : 
 (1) Adequate or homologous stimuli, i.e., stimuli for whose action the sense organs are specially 
 adapted, such as the rods and cones of the retina for the vibrations of the ether. Thus each sense 
 organ has a specific form of stimulus best adapted to act upon it. This is what Johannes Miiller 
 called the law of specific energy. (2) There are many other forms of stimuli (mechanical, thermal, 
 chemical, electrical, internal somatic) which act upon the sense organs, producing the flash of light 
 beheld when the eye is struck ; singing in the ears when there is congestion of -the head. These 
 heterologous stimuli act upon the nervous elements of the sensory apparatus along their entire 
 course, from the end organ to the cortex cerebri. The homologous stimuli, on the other hand, act 
 only on the end organ, i.e., light has no effect whatever upon the trunk of the exposed optic nerve. 
 
 Strength and Liminal Intensity. — Homologous stimuli act upon the sen- 
 sory organs only within certain limits as to strength. Very feeble stimuli at first 
 produce no effect. That strength of stimulus which is just sufficient to cause the 
 first trace of a sensation is called by Fechner the " liminal intensity " of the 
 sensation. As the strength of the stimulus increases so also do the sensations, but 
 the sensations increase equally when the strength of the stimulus increases in rela- 
 tive proportions. Thus we have the same sensation of equal increase of light 
 when, instead of 10 candles, 11, or instead of 100 candles, no are lighted — the 
 proportion of increase in both cases is equal to one-tenth. As the logarithm of 
 the numbers increases in an equal degree when the numbers increase in the same 
 relative proportion, the law may be expressed thus: "The sensations do not in- 
 crease with the absolute strength of the stimuli, but nearly as the logarithm of the 
 strength of the stimulus." This is Fechner's " psycho-physical law," but its 
 accuracy has recently been challenged by E. Hering. [It holds good only with 
 regard to stimuli of medium strength.] If the specific stimulus be too intense it 
 gives rise to peculiar painful sensations, e.g., a feeling of blindness or deafness, as 
 the case may be. The sense organs respond to adequate stimuli, but only within 
 certain limits of the stimulus, e.g. , the ear responds only to vibrating bodies emit- 
 ting a certain range of vibrations per second ; the retina responds only to the 
 vibrations of the ether between red and violet, but not to the so-called heat vibra- 
 tions or to the chemically active vibrations. 
 
 748 
 
FECHNER S LAW. 
 
 749 
 
 [Fechner's Law. — Expressed in another way, the result depends on (i) the strength of the 
 stimulus, and (2) the degree of excitability. Supposing the latter to be constant while the former is 
 varied, it is found that if the stimulus be doubled, tripled or quadrupled, the sensation increases 
 only as the logarithm of the stimulus. Suppose the stimulus to be increased 10, 100 or 1000 
 times, then the sensation increases only as I, 2 or 3. Just as there is & lower limit of excitation, 
 liminal intensity (or threshold), so there is an upper limit or maximum of excitation, or height of 
 sensibility ( Wundi), when any further increase produces no appreciable increase in the sensation. 
 Thus we do not notice any difference between the central and peripheral portion of the sun's disk, 
 though the difference of light intensity is enormous [Sully). Between these two is the range of 
 sensibility ( Wundl). There is always a constant ratio between the strength of the stimulus and the 
 intensity of the sensation. The stronger the stimulus already applied the stronger must be the 
 increase of the stimulus in order to cause a perceptible increase of the sensation (Weber's Law). 
 The necessary increment is proportional to the intensity of the stimulus, and it varies for each sense 
 organ. If a weight of 10 grams be placed in the hand, it is found that 3.3 grams must be added 
 or removed before a difference in the sensation is perceptible ; if 100 grams are held, 33.3 grams 
 must be added or removed to obtain a perceptible difference in the sensation. The magnitude of 
 the fraction indicating the increment of stimulus necessary to obtain a perceptible difference of the 
 sensation is spoken of as the constant proportion or the discriminative sensibility. In the above 
 case it is I : 3. The following table gives approximately the constant proportion for each sense : — 
 
 Tactile Sensation 1:3.^ 
 
 Thermal I : 3. jf 
 
 Auditory 1 : 3. y t 
 
 Muscular Sensation 
 Visual " 
 
 6 : ioo. T fo 
 ' : IOO Tfo] 
 
 The term after sensation is applied to the following phenomenon, viz., that, 
 as a rule, the sensation lasts longer than the stimulus producing it ; thus there is 
 an after sensation after pressure is applied to the skin. Subjective sensations 
 occur when stimuli due to internal somatic causes excite the nervous apparatus of 
 the sense organ. The highest degrees of these, depending mostly upon patho- 
 logical stimulation of the psycho-sensorial cortical centres, are characterized as 
 hallucinations, e.g., when a delirious person imagines he sees figures or hears 
 sounds which have no objective reality. In opposition to this condition the term 
 illusion is applied to modifications by the sensorium of sensations actually caused 
 by external objects, e.g. , when the rolling of a wagon is mistaken for thunder. 
 
 In a new-born child the sense of touch is strongly developed, pairi slightly, muscular sensations 
 are undoubtedly present, while smell and taste are frequently confounded. Auditory stimuli are 
 heard from the second day onward, the stimulus of light immediately after birth, but a peripheral field 
 of vision does not yet exist (Cuignet). Toward the fourth to fifth week the movements of conver- 
 gence and accommodation are noticeable, while after four months colors are distinguished. The 
 various stimuli are not perceived simultaneously — a reflex inhibitory centre is not yet developed 
 (Genzmer). 
 
THE VISUAL APPARATUS-THE EYE. 
 
 384. ANATOMICO-HISTOLOGICAL OBSERVATIONS.— In the 
 
 following remarks it is assumed that the student is familiar with the anatomical 
 structure of the eye : — 
 
 The cornea, for the sake of simplicity, is regarded as uniformly spherical, although, properly 
 speaking, it differs slightly from this form. It is more like a vertical section of a somewhat oblique 
 ellipsoid, which we must suppose to be formed by rotating an ellipse around its long axis (Brilcke). 
 It is nearly of uniform thickness throughout, only in the infant it is slightly thicker in the centre, 
 and in the adult slightly thinner. The cornea consists of the following layers : — 
 
 [1. Anterior stratified epithelium. 4. Posterior elastic lamina. 
 
 2. Anterior elastic lamina. 5. Single layer of epithelium.] 
 
 3. Substantia propria. 
 
 1. The anterior epithelium, stratified and nucleated (Fig. 449, a), consists of many layers of 
 
 Fig. 447. 
 
 Fig. 448. 
 
 Fig. 447.— Cornea of the frog treated with chloride of gold, showing the corneal corpuscles stained, and a few nerve 
 fibrils. Fig. 448. — Cornea of the frog treated with silver nitrate; the ground substance is stained, while the 
 spaces for the corneal corpuscles are left unstained 
 
 cells. The deepest cells are more or less columnar, are arranged side by side, and are called sup- 
 porting cells. The cells of the middle layers are more arched, and dip with finger-shaped processes 
 into corresponding spaces between their neighbors. The most superficial cells are flat, perfectly 
 smooth, hard, keratin-containing squamous epithelium. 2. The epithelial layer rests upon the 
 anterior elastic membrane (Bowman's elastic lamina), a structureless, clear basement-like mem- 
 brane (i), whose existence is denied by Briicke. 3. The substantia propria of the cornea consists 
 of (chondrin-yielding) fibres (Johannes Muller, Rollett) composed of delicate fibrils of connective 
 tissue. The fibres are arranged in mat-like, thin lamellae (/), more or less united together, and are 
 placed in layers over each other. Toward the anterior elastic lamina the fibres bend round and per-, 
 forate the superficial lamellae, thus serving as supporting fibres. [These perforating fibres are com- 
 parable to Sharpey's fibres in bone.] Between the lamellae are a series of intercommunicating 
 spaces lined by endothelium. These spaces are really lymph spaces, and they communicate with 
 the lymphatics of the conjunctiva. The fixed corneal corpuscles (c) lie in these spaces, and are 
 provided with numerous processes, which anastomose with the processes of corpuscles lying between 
 
 750 
 
THE CORNEA AND BOWMAN S TUBES. 
 
 751 
 
 the lamellae above and below them, and on either side of them. Ktihne observed that stimulation 
 of the corneal nerves was followed by contraction of these cells ($ 201, 7) ; while Kiihne and Wal- 
 deyer maintain that they are connected with the corneal nerve fibrils. 
 
 [The corneal corpuscles are looked upon as branched connective-tissue corpuscles lying in and 
 not quite filling the branched spaces between the lamellae. The processes anastomose freely with 
 similar cells in the same plane, and to a less extent with the processes of cells in planes immediately 
 above and below them. In a section stained with gold chloride they present the appearance seen 
 in Fig. 447. In a vertical section of the cornea they appear fusiform (Fig. 449) and parallel to the 
 free surface of the cornea. If the cornea of a frog be pencilled with silver nitrate, the cement sub- 
 stance between the lamellae is blackened, and the branched cell spaces remain clear, as in Fig. 448. 
 The one figure represents, as it were, the positive, and the other the negative image.] 
 
 Fig. 449. 
 
 Antero-posterior section at the junction of the cornea with the sclerotic, a, anterior corneal, or conjunctival epithe- 
 lium ; £, Bowman's lamina; c, corneal corpuscles lying in the juice canals; £, corneal lamellas (the whole 
 thickness lying between b and d is the substantia propria cornea: ) : d, Descemet's membrane ; e, epithelium cov- 
 ering it ; _/", junction of cornea with the sclerotic ; g t limbus conjunctivae ; h, conjunctiva ; i, canal of Schlemm ; 
 k, Leber's venous plexus (is regarded by Leber as belonging to i) ; w, m, meshes in the tissue of the lig. iridis 
 pectinatum ; «, attachment of the iris ; 0, longitudinal ; p, circular (divided transversely) bundles of fibres of the 
 sclerotic ; '/, perichoroidal space ; s, meridional [radiating] ; t , equatorial (circular) bundles of the ciliary muscle; 
 ;/, transverse section of a ciliary artery ; v, epithelium of the iris (a continuation of that on the posterior surface 
 of the cornea) ; w, substance of the iris ; jr, pigment of the iris ; z, a ciliary process. 
 
 [Bowman's tubes are artificial productions, formed by forcing air or a colored fluid between 
 the lamellae, when it passes between the bundles of fibrils, forming a series of tubes with dilatations 
 on them and running at right angles to one another between the lamellae.] 
 
 According to v. Recklinghausen, leucocytes also pass into these lymph spaces or juice canals. 
 The importance of these leucocytes in inflammation is referred to in \ 200. 4. The transparent 
 structureless posterior elastic membrane ((f), the membrane of Descernet or Demours, is in many 
 animals fibrillated, and shows evidence of stratification, while toward the margin of the cornea 
 there are occasionally slight conical elevations. This membrane is very tough and very resistant (oft 
 great importance in inflammation). If it be removed, it rolls up toward the convex side. At its 
 periphery it becomes continuous with the fibro-elastic reticulated ligamentum pectinatum iridis, 
 
752 
 
 THE NERVES OF THE CORNEA. 
 
 whose trabecule are covered by epithelium. 5. The posterior single layer of epithelium consists 
 of flat, delicate nucleated cells (e), which are continued from the margin of the cornea on to the 
 anterior surface of the iris (v). Fine juice canals exist in the spaces between the individual cells 
 (v. Recklinghausen). These spaces communicate with a system of fine tubes under the epithelium, 
 perforate Descemet's membrane, and thus communicate with the corneal spaces (Preiss). 
 
 •SJiS&i. 
 
 Vertical section of the cornea stained with gold chloride. «, nerve fibrils ; a, perforating branch ; r, nucleus ; f % 
 6, inter-epithelial termination of fibrils ; s , anterior elastic lamina. 
 
 The nerves of the cornea, which are derived from the long and short ciliary nerves (§ 347), are 
 partly sensory in function. They enter the cornea at its margin as medullated fibres, but the myelin 
 soon disappears, while the axial cylinders split up into fibrils. [The axial cylinders branch and form 
 a plexus between the lamellae, especially near the anterior surface, the fundamental or ground 
 plexus (Fig. 450, n). There are triangular nuclei at the nodal points, but they probably belong to 
 the sheath of flattened cells which cover the larger branches. There is a finer and denser plexus 
 
 Fig. 451. 
 
 Nerve plexus in cornea after gold chloride, n, nerve ; a, fibrils. 
 
 of fibrils immediately under the anterior epithelium, sub-epithelial plexus (Fig. 451), which is 
 derived from the former, the fibrils arising in pencils or groups. Some fibrils perforate the anterior 
 .elastic lamina, rami perforantes, and pass between the anterior epithelial cells to form the intra- 
 epithelial network (Fig. 450, b,p). Some observers suppose that they terminate in free, pointed, 
 or bulbous ends. There is also a fine plexus of fibrils in the posterior layers of the cornea, near 
 
THE CHOROID AND CILIARY MUSCLE. 
 
 753 
 
 Descemet's membrane. It gives off numerous fine fibrils, which come into intimate, if not direct, 
 anatomical relation with the corneal corpuscles. The trophic fibres of the cornea (§ 347) are, per- 
 haps, those deeper branches which are connected with the corneal corpuscles.] 
 
 [Method. — These fibrils are best revealed by staining a cornea with chloride of gold, which stains 
 them of a purplish tinge after exposure to light (Cohnheim).~\ 
 
 Blood Vessels occur only in the outer margin of the cornea (Fig. 452, v), and extend 2 mm. 
 over the cornea above, 1.5 mm. below, and I mm. laterally — the most external capillaries form 
 arched loops, and thus turn on themselves. The cornea is nourished from the blood vessels in its 
 margin. Opacities of the cornea give rise to many forms of visual defects. 
 
 The sclerotic is a thick fibrous membrane, composed of, p, circular (equatorial) and, 0, longi- 
 tudinal (meridional) bundles of connective tissue woven together. The spaces between the bundles 
 contain colorless and pigmented connective-tissue corpuscles ( Waldeyer)^ and also leucocytes. It 
 is thickest posteriorly, thinner at the equator, 
 
 while in front of this it again becomes thicker, ow- F IG _ 4 j 2 . 
 
 ing to the insertion of the tendons of the straight 
 muscles of the eyeball. It contains few blood ves- 
 sels, which form a wide-meshed capillary plexus 
 immediately under its deep surface. Other vessels 
 form an arterial ring around the entrance of the 
 optic nerve. It rarely is quite spherical ; it 
 rather resembles an ellipsoid, which we might 
 imagine to be formed by the rotation of an 
 ellipse around its short axis (short eyes) or around 
 its long axis (long eyes). Above and below the 
 sclerotic overlaps like a fold the clear margin of 
 the cornea ; hence, when the cornea is viewed 
 from before it appears transversely elliptical, 
 when seen from behind it appears circular. Fol- 
 lowing the margin of the cornea, but lying still 
 within the substance of the sclerotic, is the circu- 
 lar canal of Schlemm, i, which communicates 
 with other anastomosing veins, the venus plexus 
 of Leber, k. Schwalbe and Waldeyer regarded 
 Schlemm's canal as a lymphatic. Posteriorly, 
 the sclerotic becomes continuous with the fibrous 
 covering of the optic nerve derived from the dura 
 mater. The sclerotic is provided with nerves, 
 which are said to terminate in the cells of the 
 scleral, substance (Helfreick, Konigstein). 
 
 The tunica uvea, or the uveal tract, is com- 
 posed of the choroid, the ciliary part of the cho- 
 roid, and the iris. 
 
 The choroid is composed of the following 
 layers: (1) Most internally is the transparent 
 limiting membrane, 0.7 /i in thickness, but it 
 is slightly thicker anteriorly. (2) The very 
 vascular capillary network of the chorio-capil- 
 laris, or membrane of Ruysch, embedded in a 
 
 homogeneous layer. Then follows— (3). ajayer Diagram f the blood vessels of the eye (Leier) (horizon- 
 tal view, veins black, arteries light, with a double con- 
 tour), a, a, short posterior ciliary; b, long posterior 
 ciliary ; c, c*, anterior ciliary artery and vein ; d, d r , 
 artery and vein of the conjunctiva; e y J, central artery 
 and vein of retina ;./", blood vessels of the inner, and^-, 
 of the outer optic sheath ; h, vorticose vein ; 1, posterior 
 short ciliary vein confiued to the sclerotic ; k, branch of 
 the posterior short ciliary artery to the optic nerve; /, 
 anastomosis of the choroidal vessels with those of the 
 optic ; ?«, chorio-capillaris ; «, episcleral branches ; o, 
 recurrent choroidal artery ; /, great circular artery of 
 iris (transverse section) ; a t blood vessels of the iris ; 
 r, ciliary process ; j, branch of a vorticose vein from 
 the ciliary muscle ; t, branch of the anterior ciliary 
 vein to the ciliary muscle ; u, circular vein ; v, margin- 
 al loops of vessels on the cornea ; w, anterior artery 
 and vein of the conjunctiva. 
 
 of a thick elastic network, covered on both sur 
 faces by endothelium {Sattler). (4) The cho- 
 roid proper consists of a layer with pigmented 
 connective-tissue corpuscles, together with a 
 thick elastic network, containing the numerous 
 venous vessels as well as the arteries. The pig- 
 mented layers, called the supra- choroidea, or 
 lamina fusca, which surrounds the large lym- 
 phatic space lined with endothelium, and called 
 the perichoroidal space, q. In new-born in- 
 fants, which, according to Aristotle, have the 
 iris dark-blue, the uveal tissue is devoid of pig- 
 ment ; in brunettes it is developed later, and in 
 blondes not at all. 
 
 In the ciliary part of the choroid the pigmented connective- tissue corpuscles are not so numerous. 
 
 The ciliary muscle (tensor choroidese, or muscle of accommodation) is placed in this region. It 
 
 arises, s, by means of a branched, reticulated, connective tissue origin, from the inner side of the 
 
 junction of the cornea and sclerotic, near the canal of Schlemm, and passes backward to be inserted 
 
 48 
 
754 THE VEINS. 
 
 into the choroid. This constitutes the radiating fibres. Other fibres lying internal to these are 
 arranged circularly, /, in bundles in the ciliary margin. These circular fibres are sometimes called 
 Heinrich Miiller's muscle. The muscle consists of smooth muscular fibres, and is supplied by the 
 oculomototius (\ 345, 3). 
 
 The iris consists of the following parts from before backward : a layer of epithelial cells (v) 
 continuous with those covering the posterior surface of the cornea, a layer of reticulated connective 
 tissue, the layer of blood vessels, and, lastly, a posterior limiting membrane, which contains the 
 pigmentary epithelium (x), [Michel). In brunettes, the texture of the iris contains pigmented con- 
 nective-tissue corpuscles. The iris contains two muscles composed of smooth muscular fibres — one 
 set constituting the sphincter pupillse (circular, Fig. 467), which surrounds the pupil, and lies 
 nearer the posterior than the anterior surface of the iris ($ 392). Its nerve of supply is derived from 
 the oculomotorius (§ 345, 2). The other fibres constitute the dilator pupillse (radiating), which 
 • consists of a thinner layer of fibres arranged in a radiate manner. Some of the fibres reach to the 
 margin of the pupil, while others bend into the sphincter. At the outer margin of the iris the radial 
 bundles are arranged in anastomosing arches, and form a circular muscular layer (Merkel). The 
 chief nerve of supply for the dilator fibres is the sympathetic (§ 347, 3). Ganglia occur in the 
 ciliary nerves in the choroid [and they are found, also, in the iris]. Gerlach has recently applied 
 the term ligamentum annulare bulbi to that complex fibrous arrangement which surrounds, the iris, 
 and at the same time forms the point of union of the ciliary body, iris, ciliary muscle, sinus venosus 
 iridis, and the line of junction of the cornea and sclerotic. 
 
 The choroidal vessels are of great impoitance in connection with the nutrition of the eye. 
 According to Leber, they are arranged as tollows: The arteries are — 1. The short posterior 
 ciliary (Fig. 452, a, a), which are about twenty in number and perforate the sclerotic near the 
 optic nerve. They terminate in the vascular network of the chorio-capillaris (m), which reaches 
 as far as the ora-serrata. 2. The long posterior ciliary, one lies on the nasal and the other on 
 the temporal side, and they run (b) to the ciliary part of the choroid, where they divide dichoto- 
 mously, and penetrate into the iris, where they help to form the circulus arteriosus iridis major (p). 
 3. The anterior ciliary (c), which arise from the muscular branches, perforate the sclerotic ante- 
 riorly, and give branches to the ciliary part of the choroid and to the iris. About twelve branches 
 run backward (0) from them to the chorio-capillaris. 
 
 The Veins. — 1. The anterior ciliary veins (c) rtceive the blood from the anterior part of the 
 uvea and carry it outward. These branches are connected with Schlemm's canal and Leber's 
 venous plexus. They do not receive any blood from the iris. 2. The venous plexus of the 
 ciliary processes (r) receives the blood from the iris (q), and passes backward to the choroidal veins. 
 3. The large vasa vorticosa Stenonis (h) perforate the scltrolic behind the equator of the bulb. 
 
 The inner margin of the iris rests upon the anterior surface of the lens ; the posterior chamber is 
 small in adults, and in the newborn child it may be said scarcely to exist, it is so small. When 
 Berlin blue is injected into the anterior chamber of the eye, it generally passes into the anterior 
 ciliary veins (Sch^valbe). Even in living animals carmin also behaves in a.similar manner (Heis- 
 rath), so that these observers conclude that there is a direct communication between the veins and 
 the aqueous chamber, as these substances do not diffuse through membranes. 
 
 Internal to the choroid lies the single layer of hexagonal cells (0.0135 to °- 02 mm> m breadth) 
 filled with crystalline pigment. Th is laye r really belongs to the retina. It consists of a single layer 
 of cells as far as the ora-serrata — it'is conTirraetTon to tn^TSlisrry'processes and the posterior surface 
 of the iris (Fig. 449, x), where it forms several layers. In albinos it is devoid of pigment ; on the 
 other hand, the uppermost cells, which lie on the ridges of the ciliary processes, are always devoid 
 of pigment. [The processes of these cells vary in length with the nature and kind of light acting 
 on the retina (<! 398).] 
 I The retina externally is in contact with the layer of hexagonal pigment cells (Pi), which in its 
 I development and functions really belongs to the retina. The cells are not flat, but they send pig- 
 mented processes into the spaces between the ends of the rods. In some animals (rabbit) the cells 
 contain fatty granules and other substances. The cells are larger and darker at the ora-serrata 
 (JCiihne). The retina is composed of the following layers proceeding from without inward : — 
 
 6. Inner nuclear layer. 
 
 [1. Layer of pigment cells. 
 
 2. Rods and cones. 
 
 3. External limiting membrane. 
 
 4. Outer nuclear layer. 
 
 5. Outer molecular (granular or inter- 
 
 nuclear) layer. 
 
 7. Inner molecular (granular) layer. 
 
 8. Layer of nerve cells (ganglionic) 
 
 layer. 
 
 9. Layer of nerve fibres. 
 
 10. Internal limiting membrane."] 
 
 1. The hexagonal pigment cells already described. 2. The layer of rods and cones (St) 
 or neuro- epithelium of Schwalbe \bacillary layer, or the visual cells, or visual epithelium of Kuhne] 
 (Fig. 454). These lie externally next the choroid, but they are absent at the entrance of the optic 
 nerve. Then follows the external limiting membrane (Le), which is perforated by the bases of 
 the rods and cones. 3. The external nuclear layer (au.K), which with all the succeeding layers 
 are called "brain layers" by Schwalbe. 4. The external granular (augr), or internuclear layer, 
 which is perforated by the fibres which proceed inwaid from the nuclei of 3 (Merkel) to reach 5, 
 
THE RETINA. 
 
 F55 
 
 the nuclei of the internal nuclear layer (inK). The nuclei of this layer, which are connected 
 by fibres with the rods and cones, are marked by transverse lines in the macula lutea (Krattse, 
 Denissenko). 6. The finely granular internal granular layer [in.gr), through which the fibres 
 proceeding from the inner nuclear layer cannot be traced. It would seem as if these fibres break 
 up into the finest fibrils, into which, also, the branched processes of the ganglionic cells of 7, the 
 ganglionic layer, extend. According to v. Vintschgau, the processes of the ganglionic cells are 
 connected with the fibres. 8. The next, or fibrous layer, consists of the fibres of the optic nerve 
 (0), and most internally is the internal limiting membrane ( Li), According to W. Krause, there 
 are 400,000 broad, and as many narrow, optic fibres, so that for every fibre there are 7 cones, about 
 100 rods, and 7 pigment cells. The optic fibres are absent from the macula lutea, where, however, 
 there are numerous ganglionic cells. Between the two homogeneous limiting membranes ( Le and 
 Li) lies the connective-tissue substance of the retina. It contains the perforating fibres, or 
 
 Fig. 454. 
 
 F'G. 453- 
 
 JIA Li 
 
 Fig. 453. — Vertical section of human retina, a, rods and cones : b, ext. and 7", int. limit, memb. ; c, ext. and f t int. 
 nucl. layers ; e, ext. and g, int. gran, layers ; ft, blood vessel and nerve cells :_ i, nerve fibres. Fig. 454. — Layers 
 of the retina. Pi, hexagonal pigment cells ; St, rods and cones ; Le, ext. limiting membrane ; au.K, ext. nuclear 
 layer ; augr, ext. granular layer ; tnJC, int. nuclear ; in.er, int. granular ; Ggl, ganglionic nerve cells ; o, fibres oi 
 optic nerve ; Li, int. limit, membrane; Rk, fibres of Mullet- ; K, nuclei ; Sy, spaces for the nervous elements. 
 
 Muller's fibres, which run in a radiate manner between the two membranes and hold the various 
 layers of the retina together. They begin by a wing-shaped expansion at the internal limiting 
 membrane {Rk), and in their course outward contain nuclei [k). They are absent at the yellow 
 spot. The supporting tissue forms a network in all the layers, holes being left for the nervous 
 portions (Sg). The inner segments of the rods and cones are also surrounded by a sustentacular 
 substance. As the retina passes forward to the ora serrata it becomes thinner and thinner, gradually 
 becoming richer in connective-tissue elements and poorer in nerve elements, until, in the ciliary 
 part, only the cylindrical cells remain (Fig. 453). 
 
 [Macula Lutea and Fovea Centralis. — There are no rods in the fovea, while the cones are 
 longer and narrower than in the other parts of the retina (Fig. 455). The other layers, also, are 
 thinner, especially at the macula lutea, but they become thicker toward the margins of the fovea, 
 
756 
 
 VISUAL PURPLE OR RHODOPSIN. 
 
 where the ganglionic layer consists of several rows of bipolar cells. The yellow tint is due to 
 pigment lying between the layers composing the yellow spot.] 
 
 The blood vessels of the retina lie in the inner layers near the inner granular layer. Only near 
 the entrance of the optic nerve are they connected by fine branches with the choroidal vessels; they 
 are surrounded by perivascular lymph spaces. The greatest number of capillaries runs in the layers 
 external to the inner granular layer [Hesse, His). The fovea centralis is devoid of blood vessels 
 {Nettleship, Becker). Except in mammals, the eel (Denissenio), and some tortoises (//. Muller), 
 the retina receives no blood vessels. Destruction of the retina is followed by blindness. 
 
 [Retinal Epithelium. — The single layer of pigmentary cells containing granules of melanin 
 sends processes downward, like the hairs of a brush, betwe.-n the rods and cones. Kiihne has 
 shown that the nature and amount of light influences the condition of these processes (Fig. 497). 
 The protoplasm of these cells in a frog kept for several hours in the dark is retracted, and the pig- 
 ment granules lie chiefly in the body of the cell and in the processes near the cell. In a frog kept 
 in bright daylight, the processes loaded with pigment penetrate downward between the rods and 
 cones as far as the external limiting membrane.] 
 
 Each rod and cone consists of an outer and an inner segment. During life the outer segment 
 contains a reddish pigment or the visual purple {Bolt). 
 
 Visual purple [or rhodopsin] may be preserved by keeping the eye in darkness, but it is soon 
 bleached by daylight, while it is again restored when the eye is placed in darkness. It can be 
 extracted from the retina by means of a 2.5 per cent, solution of the bile acids, especially from 
 eyes that have been kept in 10 per cent, solution of common salt (Ayres). The rods are 0.04. 
 to 0.06 mm. high and 0.0016 to 0.0018 mm. broad, and exhibit longitudinal striatum, pro- 
 
 Fig. 455. 
 
 Section of the fovea centralia. a, cones ; b andf , int. and ext. limit, memb. ; c, ext. and e, nuclear layer ; d, fibres ; 
 
 /, nerve cells'. 
 
 duced by the presence of fine grooves;. a fine fibril runs in their interior {Ritler). The external 
 segment occasionally cleaves transversely into a number of fine transparent disks. [It is a very 
 resistant structure, and in this respect resembles neurokeratin.] Krause found an ellipsoidal body, 
 the " rod ellipsoid," at the junction of the inner and outer segments of the rods. The cones are 
 devoid of visual purple, but their outer segment is striated longitudinally, and it also readily breaks 
 across into thin disks. Only cones are present in the macula lutea. In the neighborhood of the 
 yellow spot each cone is surrounded by a ring of rods. The cones become less numerous toward 
 the periphery of the retina. In nocturnal animals, such as the owl and bat, there are either no 
 cones or imperfect ones. The retinae of birds contain many cones, that of the tortoise only cones. 
 The rods and cones rest on the sieve-like perforated external limiting membrane {Le). Both send 
 processes through the membrane, the cones to the larger and higher-placed nuclei, the rods to the 
 nuclei, with transverse markings in the external nuclear layer. [The cones are particularly large 
 in some fishes, e.g., the cod, while the skate has no cones, but only rods. The same is the case in the 
 shark and sturgeon, hedgehog, bat and the mole.] 
 
 [Distribution and Regeneration of Rhodopsin. — Keep a rabbit in the dark for some time, 
 kill it, remove its eyeball, and examine its retina by the aid of monochromatic (sodium) light. The 
 retina will be purple-red in color, all except the macula lutea and a small part at the ora serrata. 
 The pigment is confined to the outer segments of the rods. It is absent in pigeons, hens and one 
 bat, although the last has only rods. It is found both in nocturnal and diurnal animals. ' Its color 
 is quickly bleached by light, and it fades rapidly at a temperature of 50° to 76° C , while trypsin, 
 alum and ammonia do not affect it. It is restored in the retina by the action of the retinal epithe- 
 lium. If the retinal epithelium or choroid be lifted off from an' excised eye exposed to light, the 
 
THE VITREOUS HUMOR. 
 
 757 
 
 Fig. 456. 
 
 LUC 
 
 in t 
 
 purple is destroyed, but if the eye be placed in darkness and the retinal epithelium replaced, the 
 color is restored.] 
 
 Chemistry of the Retina. — The reaction of the retina, when quite fresh, is acid, and becomes 
 alkaline in darkness. The rods and cones contain albumin, neuro-keratrin, nuclein, and in the 
 cones are the pigmented oil globules, the so-called " chromophanes." The other layers contain 
 the constituents of the gray matter of the brain. 
 
 [Cones. — There is no coloring matter in the outer segment of the cones, but in fishes, reptiles, 
 and birds the inner segment contains a globular colored body often red and yellow, the pigment 
 being held in solution by a fatty body. Kiihne has separated a green (chlorophane), a yellow 
 (xanthophane), and a red (rhodophane) pigment. They all give a blue with iodine (Sckwalbe), 
 and are bleached by light.] 
 
 The crystalline lens is enclosed in a transparent capsule, thicker anteriorly than posteriorly, and 
 it is covered on the inner surface of the anterior wall by a layer of low epithelium. Toward the 
 margin of the lens, these cells elongate into nucleated fibres 
 (Robinski), which all bend round the margin of the lens, and 
 on both sides of the lens abut with their ends against each of the 
 triradiate figures. The lens fibres contain globulin enclosed in 
 a kind of membrane. Owing to mutual pressure, they are hex- 
 agonal when seen in transverse section (Fig. 456, 2), while 
 many animals, especially fishes, their margins are serrated [the 
 teeth dovetail into each other]. For the sake of simplicity, we 
 may regard the lens as a biconvex body with spherical surfaces, 
 the posterior surface being more curved. As a matter of fact, 
 the anterior part is part of an ellipsoid formed by rotation on its 
 short axis. The posterior surface resembles the section of a 
 paraboloid, i. <?., we might regard it as formed by the rotation of 
 a parabola on its axis (Briicke). The outer layers of the lens 
 have less refractive power than the more internal layers. The 
 central part of the lens or nucleus is, at the same time, firmer, 
 and more convex than the entire lens. The margin of the lens 
 is always separated from the ciliary processes by an intermediate 
 space. 
 
 [Chemistry. — The lens contains about two-thirds of its 
 weight of water, while its chief solid is a globulin, called by 
 Berzelius crystallin (24.6 per cent.), with a little serum albu- 
 min, salts, cholesterin, and fats.] 
 
 [Cataract.— Sometimes the lens becomes more or less opaque, 
 the opacity beginning either in the middle or- outer parts of the 
 lens. This is generally due to fatty degeneration of the fibres, 
 cholesterin being deposited. An opaque cataractous condition 
 of the lens may be produced in frogs by injecting a solution of some salts or sugar into the lymph 
 sacks ; the result is that these salts absorb the water from the lens, and thus make it opaque. The 
 cataract of diabetes is probably produced from the presence of grape sugar in the blood.] 
 
 The zonule of Zinn, at the ora serrata, is applied as a folded membrane to the ciliary part of 
 the uvea, so that the ciliary processes are pressed into its folds, and are united to it. It passes to the 
 margins of the lens, where it is inserted by a series of folds into the anterior part of the capsule of 
 the lens. Behind the zonule of Zinn, and reaching as far as the vitreous humor, is the canal of 
 Petit. The zonule is a fibrous, perforated membrane (Sckwalbe, Vlacowitsch). According to 
 Merkel, the canal of Petit is enclosed by very fine fibres, so that it is really not a canal but a complex 
 communicating system of spaces (Gerlach). Nevertheless, the zonule represents a stretched mem- 
 brane, holding the lens in position, and may, therefore, be regarded as the suspensory ligament 
 of the lens. 
 
 Opacity or cloudiness of the lens (gray cataract) hinders the passage of light into the eye. The 
 absence of the lens (Aphakia), as after operations for cataract, maybe remedied by a pair of strong 
 convex spectacles. Of course such an eye does not possess the power of accommodation. 
 
 The vitreous humor, as far as the ora serrata, is bounded by the internal limiting membrane of 
 the retina (Henle, Iwanoff). From here forward, lying between both, are the mer ^diona ljibr es of / 
 the zonule, which are united with the surface of the vitreous and the ciliary processes! A part ot 
 the fibrous layer bends into the saucer-shaped depression, and bounds it. A canal, 2 mm. in diam- 
 eter, runs from the optic papilla to the posterior surface of the capsule of the lens ; it is called the 
 hyaloid canal, and was formerly traversed by blood vessels. The peripheral part of the vitreous 
 humor is laminated like an onion, the middle is homogeneous ; in the former, especially in the 
 foetus, are round fusiform or branched cells of the mucous tissue of the vitreous, while in the centre 
 there are disintegrated remains of these cells {Iwanoff). The vitreous contains a very small per- 
 centage of solids, and 1.5 per cent of mucin [and according to Picard there is 0.5 per cent, of 
 urea, and about .75 of sodic chloride]. 
 
 [Structure. — The vitreous consists essentially of mucous tissue, in whose meshes lies a very 
 
 , Fibres of the lens ; 2, transverse sec- 
 tions oi the lens fibres. 
 
758 
 
 INTRAOCULAR PRESSURE. 
 
 watery fluid, containing the organic and inorganic bodies in solution. According to Younan, the 
 vitreous contains two types of cells — (i) amoeboid cells of various shapes and sizes. They lie on 
 the inner surface of the lining hyaloid membrane and the other membranes in the cortex of the 
 vitreous ; (2) large branching multipolar cells. The vitreous is permeated by a large number of 
 transparent, clear, homogeneous hyaloid membranes, which are so disposed as to give rise to a 
 concentric lamination. The canal of Stilling represents in the adult the situation of the hyaloid 
 artery of the foetus. It can readily be injected by a colored fluid. In preparations of the vitreous, 
 Younan finds fibres not unlike elastic fibres, and other fibres more especially after staining with 
 chloride of gold.] 
 
 The lymphatics of the eye consist of an anterior and a posterior set (Schwalbe). The anterior 
 consist of the anterior and posterior chambers of the eye (aqueous), which communicate with the 
 lymphatics of the iris, ciliary processes, cornea, and conjunctiva. The posterior consist of the 
 perichoroidal space between the sclerotic and the choroid \Schwalbe). This space is connected by 
 means of the perivascular lymphatics around the trunks of the vasa vorticosa, with the large lymph 
 space of Tenon, which lies between the sclerotic and Tenon's capsule (Schwalbe). Posteriorly this 
 is continued into a lymph channel, which invests the surface of the optic nerve ; while anteriorly it 
 communicates directly with the sub conjunctival lymph spaces of the eyeball (Gerlach). The optic 
 
 Fig. 457. 
 
 W^^^^^^^^' 
 
 Wm&* 
 
 w 
 
 Iffti 
 
 Wm0m 
 
 1,71 1 WEB* 
 
 Mil 
 
 I'm, 
 
 m L ' ' • "< ' fMwi 
 
 •Mm . i^€m:mmj 
 'mil ! < ; " 7v/v(V 
 
 'Horizontal section of the entrance of the optic nerve and the coats of the eye. a, inner, 6, outer layers of the retina ; 
 f , choroid ; if, sclerotic ; e, physiological cup ; /", central artery of retina in axial canal ; g, its point of bifurcation ; 
 h, lamina cribrosa ; /, outer (dural) sheath ; in, outer (subdural) space ; n, inner (subarachnoid) space ; r, middle 
 (arachnoid) sheath ; /, inner (pial) sheath ; ;', bundles of nerve fibres ; k, longitudinal septa of connective tissue.' 
 
 nerve has three sheaths — (i) the dural ; (2) the arachnoid ; and (3) the pial sheath, derived 
 from the corresponding membranes of the brain. Two lymph spaces lie between these three sheaths 
 — the subdural space between I and x, and the subarachnoid space between 2 and 3 (Fig. 547)- 
 Both spaces are lined by endothelium ; and the fine trabecular passing from one wall to the other 
 are similarly covered. According to Axel Key and Retzius, these lymph spaces communicate an- 
 teriorly with the perichoroidal space. 
 
 The aqueous humor closely resembles the cerebrospinal fluid, and contains albumin and sugar ; 
 the former is increased, and the latter disappears after death. The same occurs in the vitreous. The 
 albumen increases when the difference between the blood pressure and the intraocular pressure rises. 
 Such variations of pressure, and also intense stimuli applied to the eye, cause the production of 
 fibrin in the anterior chamber (Jesner and Grilnhagen). 
 
 Intraocular Pressure. — The cavity of the bulb is practically filled with watery fluids, which, 
 during life, are constantly subjected to a certain pressure, the " intraocular pressure." Ultimately, 
 this depends upon the blood pressure within the arteries of the retina and uvea, and must rise and 
 fall with it. The pressure is determined by pressing upon the eyeball, and ascertaining whether it 
 is tense, or soft and compressible. Just as in the case of the arterial pressure, the intraocular pres- 
 
DIOPTRIC OBSERVATIONS. 759 
 
 sure is influenced by many circumstances ; it is increased at every pulse beat and at every expiration, 
 while it is decreased during inspiration. The elastic tension of the sclerotic and cornea regulates 
 the increase of the arterial pressure by acting like the air chamber in a fire engine ; thus, when more 
 arterial blood is pumped into the eyeball, more venous blood is also expelled. The constancy of 
 the intraocular pressure is also influenced by the fact that, just as the aqueous humor is removed, it 
 is secreted, or rather formed, as rapidly as it is absorbed (§ 392). 
 
 The secretion of the aqueous humor occurs pretty rapidly, as may be surmised from the fact 
 that haemoglobin is found in the aqueous humor half an hour after dissolved blood (lamb's) is in- 
 jected into the blood vessels of a dog. It is rapidly reformed, after evacuation, through a wound 
 in the cornea. According to J^nies, the watery fluid within the eyeball is secreted, especially from 
 the chorio-capillaris, and reaches the suprachoroidal space, in the lymph sheaths of the optic nerve, 
 and partly through the network of the sclerotic. It saturates the retina, vitreous, lens, and for the 
 most part passes through the zonula ciliaris into the posterior chamber, and through the pupil into 
 the anterior chamber. The movements of the fluid within the eyeball have been recently studied 
 by Ehrlich, who used fluorescin, an indifferent substance, which on being introduced into the body 
 passes into the fluids of the eyeball, and in a very dilute solution may be recognized by its green fluor- 
 escence in reflected light. From observations on the entrance of this substance into the eye Scholer, 
 and Uhthoff regard the posterior surface of the iris and the ciliary body as the secretory organs for 
 the aqueous humor. It passes through the pupil into the anterior chamber ; some passes into the 
 lens, and along the canal of Petit into the vitreous humor (Pfliiger). Section of the cervical sym- 
 pathetic, and still more of the trigeminus, accelerates the secretion of the aqueous, but its amount is 
 diminished. If the substance is dropped into the conjunctival sack it percolates toward the centre 
 of the cornea, and through the latter into the anterior chamber (Pfliiger). 
 
 The outflow of the aqueous humor, according to Leber and Heisrath, takes place chiefly between 
 the meshes of the ligamentum pectinatum iridis (Fig. 449, m, m), through which it passes into the 
 channels of the circulus venosus, and the canal of Schlemm (z, i). A very small part of the 
 aqueous passes through the cornea into the sub-conjunctival connective tissue, and even into the 
 conjunctival sack. After burning the limbus cornese with a hot needle this outflow is arrested, the 
 eyeball becomes very hard, so that the intrabulbar vessels are subjected to high pressure (Scholer). 
 Perhaps there is a direct communication between the anterior ciliary veins and the anterior chamber 
 (p. 754). None of the water is conducted from the eyeball by any special efferent lymphatics 
 (Leber). Under normal circumstances the pressure is nearly the same in the vitreous and aqueous 
 chambers, but atropin seems to diminish the pressure in the former and to increase it in the latter, 
 whilst Calabar bean has an opposite action (Ad. Weber). Arrest of the outflow of the venous 
 blood often increases the pressure in the vitreous, and diminishes that in the aqueous chamber. 
 Compression of the bulb from without cause-* more fluid to pass out of the eye temporarily than 
 enters it. The diminution of the intraocular pressure is well marked after section of the trigeminus, 
 while it rises when this nerve is stimulated. The statements vary regarding the effect of the sym- 
 pathetic nerve upon the pressure. Interruption to the venous outflow increases the pressure, while 
 an imperfect supply of blood, the outflow being normal, diminishes the pressure. The innervation 
 of the blood vessels of the eye is referred to at f| 347. 
 
 385. DIOPTRIC OBSERVATIONS.— The eye as an optical instrument is comparable to a 
 camera obscura ; in both an inverted diminished image of the objects of the external world 
 is formed upon a background, the field of projection. [In the case of the eye this is represented 
 by the retina.] Instead of the single lens of the camera, the eye has several refractive media 
 placed behind each other — cornea, aqueous humor, lens (whose individual parts — capsule, cortical 
 layers, and nucleus, all possess different refractive indices), and vitreous humor. Every two of these 
 adjacent media are bounded by a " refractive surface," which maybe regarded as spherical. The 
 field of projection of the eye is the retina, which is colored with the visual purple (Boll, Kuhne) . As 
 this substance is bleached chemically by the direct action of light, so that the pictures may be tem- 
 porarily fixed upon the retina, the compaiisonof the eye with the camera of the photographer be- 
 comes more striking. In order that the passage of the rays of light through the media of the eye 
 may be rightly understood, we must know the following factors: (1) the refractive indices of a'l 
 the media ; (2) the form of the refractive surfaces; (3) the distance of the various media from each 
 other, and from the field of projection or retina. 
 
 Action of a Converging Lens. — We must know how a convex lens acts upon light. In a 
 convex lens we distinguish the centre of curvature (Fig. 458, I, m, m^), i. e„ the centre of both 
 spherical surfaces. The line connecting both is called the chief axis ; the centre of this line is the 
 optical centre of the lens (0). All rays which pass through the optical centre of the lens pass 
 through unbent or without being refracted ; they are called the chief or principal rays (», n t ). The 
 following are the laws regulating the action of a convex lens upon rays of light : — 
 
 1. Rays which fall upon the lens, parallel with the principal axis (11,/, a), are so refracted that 
 they are collected on the other side of the lens, at a point called the focus or principal focus (/). 
 The distance of this point from the central point (a) of the lens is called the focal distance (/, 0) of 
 the lens. The converse of this condition is evident, viz., rays which diverge from a focus and reach 
 the lens pass through it to the other side, parallel with the principal axis, without again coming 
 together. 
 
760 
 
 ACTION OF LENSES ON LIGHT. 
 
 2. Rays of light proceeding from a srurce of light (IV, /) in the prolonged principal axis, but 
 beyond the focal point (/), again converge to a point on the other side of the lens. The following 
 cases may occur : (a) When the distance of the light from the lens is equal to twice the focal 
 distance, the focus, or point of convergence, lies at the same distance on the other side of the lens, 
 
 Figures illustrating the action of lenses upon rays of light passing through them. 
 
 i. e., twice the focal distance, (b) If the luminous point be moved nearer to the focus, then the 
 focal point is moved further away.- [c ) If the light is still further from the lens than twice the focal 
 distance, then the focal point comes correspondingly near to the lens. 
 
 3. Rays proceeding from a point of the chief axis (III, b) within the focal distance pass out at 
 
 Fig. 460. 
 
 
 
 
 sfr; 
 
 Siilf 
 
 S 
 
 — -^ ' : . "Br. 
 
 
 .' :■■'..' 
 
 ' ■ 
 
 the other side less divergent, but do not come to a focus again. Conversely, rays which are con- 
 vergent and pass through a collecting lens have their focal point within the focal distance. 
 
 4. If the luminous point (V, a) is placed in the secondary ray (a, 6), the same laws obtain, pro- 
 vided the angle formed by the secondary ray with the principal axis is small. 
 
REFRACTIVE INDICES. 761 
 
 Formation of Images by Convex Lenses.— After what has been stated regarding the position 
 of the point of convergence of rays proceeding from a luminous point, the construction of the image 
 of any object by a convex lens is easily accomplished. This is done simply by projecting images 
 of the various parts of the object. Thus, evidently in V, b is the focal point of the object a., while 
 v is the focal point of the object /. The picture is inverted. Collecting lenses form an inverted 
 and real image (i. e., upon a screen) only of such objects as are placed beyond the focal point of 
 the lens. 
 
 With regard to the size and distance of the image from the lens, there are the following cases : 
 (a) If the object be placed at twice the focal distance from the lens, the image of the same is just 
 the same size and at the same distance from the lens as the object is.i (b) If the object be nearer 
 than the focus, the image recedes, and at the same time becomes larger, (c) If the object be 
 further removed from the lens than twice the focal distance, then the image is nearer to the lens, 
 and at the same time becomes smaller. 
 
 Position of the Focal Point. — The distance of the focal point from the lens is readily calcu- 
 lated according to the following formula : Where / = the distance of the luminous point, b = the 
 
 distance of the image, and/ = the focal distance of the lens: — |- _=_,or_ = ._ -. 
 
 I b f b f I 
 
 Example. — Let /= 24 centimetres, / = 6 cm. Then - = y — =- B , so that b = 8 cm., 
 
 b 6 24 8 
 
 i. e., the image is formed 8 cm. behind the lens. Further, let /= 10 cm.,/= 5 cm. (2. e., I — 
 2f). Then _ = = — ; so that i= 10, i. e., the image is placed at twice the focal distance 
 
 of the lens. Lastly, let / = 00. Then _= — — — ; so that b =f, i. e., the image of parallel rays 
 
 coming from infinity lies in the focal point of the lens. 
 
 Refractive Indices. — A ray of light, which passes in a perpendicular direction from one medium 
 into another medium of different density, passes through the latter without changing its course or 
 being refracted. In Fig. 459, if G D, U J_ A B.then so is D D, J_ A B; for a plane surface A B 
 is the horizontal, and G D the vertical line. If the surface is spherical, then the vertical line is the 
 prolonged radius of this sphere. If, however, the ray of light falls obliquely upon the surface, it is 
 " refracted," i. e., it is bent out of its original course. The incident and the refracted ray, never- 
 theless, lie in one plane. When the oblique incident ray passes from a less dense medium (e.g., air) 
 into one more dense (e.g., water), the refracted or excident ray is bent toward the perpendicular. 
 If, conversely, it pass from a more dense to a less dense medium, it is bent away from the perpen- 
 dicular. The angle (z G D S) which the incident ray (S D) forms with the perpendicular (G D) 
 is called the angle of incidence, the angle formed by the refracted ray (D S^ with the prolonged 
 perpendicular (D D) is called the angle of refraction, D D S, (r). The refractive power is 
 expressed as the " refractive index.'.' The term refractive index («) means that number which 
 shows for a certain substance how many times the sine of the angle of incidence is greater than the 
 sine of the angle of refraction^ when a ray of light passes from the air into that substance. Thus, 
 » = sin. i : sin. r = ab, : cd. On comparing the refractive indices of two media, we always assume 
 that the ray passes from air into the medium. On passing from the air into water, the ray of light 
 is so refracted that the sine of the angle of incidence is to the sine of the angle of refraction as 
 
 4:3; the refractive index is = — (or more exactly = 1.336). With glass the proportion is = 3 : 2 
 
 (= 1.535) — (Snellius, 1620 ; Descartes'). 
 
 The construction of the refracted ray, the refractive index being given, is simple. Example. 
 — Suppose in Fig. 460, L = the air, G = a dense medium (glass) with a spherical surface, x y, and 
 with its centre at m ; p = the oblique incident ray, then m Z is the perpendicular, <) = i the 
 
 3 
 angle of incidence. The refractive index given is — > the object is to find the direction of the 
 
 refracted way. From as centre describe a circle with a radius of any length ; from a draw a per- 
 pendicular, a b to m Z; then a b is the sine of the angle of incidence, i. Divide the line a b into 
 three equal parts, and prolong it to the extent of two of these parts, viz., to^. Draw the line p 
 parallel to m Z. The line joining to n is the direction of the refracted ray. On making a line, 
 », s, perpendicular to m Z, n s = b p. Further, n s = sine <) = r. So that a b : s n (or : b p) 
 
 . . 3 
 
 = 3 : 2 or sin. 1 : sin. r = — • 
 J 2 
 
 Optical Cardinal Point of a Simple Collecting System. — Two refractive media (Fig. 461, 
 L and G) which are separated from each other by a spherical surface (a, b) form a simple collect- 
 ing system. It is easy to estimate the construction of an incident ray coming from the first medium 
 (L) and falling obliquely upon the surface (a, b) separating the two media, as well as to ascertain 
 its direction in the second medium, G, and also from the position of a luminous point in the first 
 medium to estimate the position of the corresponding focal point in the second medium. The 
 factors required to be known are the following: L (Fig. 461) is the first, and G the second 
 
762 
 
 CONSTRUCTION OF A REFRACTED RAY. 
 
 medium, a, i = the spherical surface whose centre is m. Of course, all the radii drawn from m 
 to a b (m x, m n) are perpendiculars, so that all rays falling in the direction of the radii must pass 
 unrefracted through m. AH rays of this sort are called rays or lines of direction ; m, as the point 
 of intersection of all these, is called the nodal point. The line which connects in with the vertex 
 of the spherical surface, x, and which is prolonged in both directions, is called the optic axis, O Q. 
 A plane (E, F) in x, perpendicular to O Q, is called the principal plane, and in it x is the prin- 
 cipal point. The following facts have been ascertained : (l ) All rays (a to a 5 ), which in the first 
 medium are parallel with each other and with the optic axis, and fall upon a b, are so refracted in 
 the second medium that they are ail-again united in one point {p x ) of the second medium. This 
 is called the second principal focus. A plane in this point perpendicular to O Q is called the second 
 
 Fig. 461. 
 
 focal plane (C, D). (2) All rays (c to c 2 ), which in the first medium are parallel to each other 
 but not parallel to O Q, reunite in a point of the second f >cal plane (r), where the non-refracted 
 directive ray {c x , m r) meets this. (In this case the angle formed by the rays c to c 2 with C Q must 
 be very small.) The propositions I and 2 of course maybe reversed; the divergent rays pro- 
 ceeding from/ toward a b pass into the first medium parallel to each other, and also with the axis 
 C Q (a to a 5 ) ; and the rays proceeding from r pass into the first medium parallel to each other, 
 but not parallel to the axis Q (as c to <r 2 ). (3) All rays, which in the second medium are parallel 
 to each other (b to b 5 ) and witn the axis Q, reunite in a point in the first medium (p), called the 
 first focal point ; of course, the converse of this is true. A plane in this point perpendicular to 
 
 '"'■'" :■!'■■:" ,.' 
 
 ui^li'iliiiil'i 
 
 O Q is called the first focal plane (A, B). The radius of the refractive surface (*, x) is equal to 
 the difference of the distance of both focal points (p and p x ) from the principal focus (x) ; thus 
 m x -=p x x — p x. From these comparatively simple propositions it is easy to determine the fol- 
 lowing points : — 
 
 1. The Construction of the Refracted Ray. — Let A (Fig. 462) be the first; B the second 
 medium; c, d, the spherical surface separating the two; a, b, the optical axis; It, the nodal point; 
 / the first and/j the second principal focus; C, D, the second focal plane.- Suppose x, y to repre- 
 sent the direction of the incident ray, what is the construction of the refracted ray in the second 
 medium ? Prolong the unrefracted ray, P, k, Q parallel to x, y, then y, Q is the direction of the 
 refracted ray (according to 2). 
 
CONSTRUCTION OF A REFRACTED RAY. 
 
 763 
 
 2. Construction of the Image for a given Object. — In Fig. 463, B, c, d, a,b, k,p, and/j, C, 
 D are as before. Suppose a luminous point (0) in the first medium, what is the position of the image 
 in the second medium ? Prolong the unrefracted ray (o, k, P), and draw the ray (o, x) parallel to 
 the axis {a, i). The parallel rays (a, e, and o, x) reunite \Dp according to proposition 1). Prolong 
 x,pj until it intersects the ray (0, P), then the image of is at P, the rays of light (0, x, and M) 
 proceeding from the luminous point (0) reunite in P. 
 
 Construction of the Refracted Ray and the Image in several Refractive Media. — If 
 
 Fig. 463. 
 
 several refractive media be placed behind each other, we must proceed from medium to medium 
 with the same methods as above described. This would be very tedious, especially when dealing 
 with small objects. Gauss (1840) calculated that in such cases the method of construction is very 
 simple. If the several media are " centred," i.e., if all have the same optic axis, then the refrac- 
 tive indices of such a centred system may be represented by two equal strong refractive surfaces at 
 a certain distance. The rays falling upon the first surface are not refracted by it, but are essentially 
 projected forward parallel with themselves to the second surface. Refraction takes place first at the 
 
 Fig. 464. 
 
 n, 
 in 
 
 
 p ^^ 
 
 /n 
 
 1 1* 
 
 1 
 4^ 
 
 A, 
 
 F, 
 
 a 
 
 
 
 
 
 
 b 
 
 
 
 hr 
 
 H, 
 
 
 k k,T--^^\ 
 
 «. F 
 
 
 
 ' 
 
 h 
 
 11 
 
 '-' 
 
 F, 
 
 second surface, just as if only one refractive surface was present. In order to make the calculation, 
 we must know the refractive indices of the media, the radii of the refractive surfaces, and the dis- 
 tance of the refractive surfaces from each other. 
 
 Construction of the refracted ray is accomplished as follows : Let a, b (Fig. 464, I), represent the 
 optical axis ; H, the first focal point determined by calculation ; h, h, the principal plane ; H, the 
 second focal point ; h 1 , h , , the second principal plane ; k, the first, and i 1 , the second nodal point ; 
 F, the second focal point ; and F„ Fj, the second focal plane. Make the ray of direction/, k x , 
 
764 
 
 FORMATION OF A RETINAL IMAGE. 
 
 parallel to m lt n x . According to proposition 2, p, k x , and m lt n t must meet in a point of the 
 plane F lf Fj. As/, k x passes through unrefracted, the ray from n 1 must, therefore, fall at r; » t r 
 is, therefore, the direction of the refracted ray. 
 
 Construction of the Focal Point. — Let o (Fig. 464, II) be a luminous point, what is the posi- 
 tion of its image in the last medium ? Prolong from the ray of direction 0, k, and make o, x par- 
 allel to a, 6. Both rays are prolonged in a parallel direction to the second focal plane. The ray 
 parallel to a, b goes through F ; m, k 1 as the ray of direction passes through unrefracted. O, where 
 », F, and m, k l intersect each other, is the position of the image of o. 
 
 386. DIOPTRIC LAWS AND THE EYE— FORMATION OF 
 THE RETINAL IMAGE— OPHTHALMOMETER.— Position of 
 the Cardinal Points. — The eye surrounded with air on the anterior surface of 
 the cornea, represents a concentric system of refractive media with spherical sepa- 
 rating surfaces. . In order to ascertain the course of the rays through the various 
 media of the eye, we must know the position of both principal points, both nodal 
 points as well as the two principal focal points. Gauss, Listing, and v. Helmholtz 
 have calculated the position of these points. In order to make this calculation, 
 we require to know the refractive indices of the media of the eye, the radii of the 
 refractive surfaces, and the distance of the latter from each other. These will be 
 referred to afterward. The following results were obtained : (1) The first principal 
 poinds 2.1746 mm. ; and (2) the second principal point is 2.5724 mm. behind the 
 anterior surface of the cornea. (3) The first nodal point, 0.7580 mm.; and (4) 
 
 Fig. 465. 
 
 B 
 
 ^ — ~ 
 
 \~^ — ■ — ______ 
 
 * 
 
 ..---" a] 
 
 
 
 \ 
 
 
 
 .. -••■"" ( 
 
 ;• 
 
 "" ""^-—-" 
 
 ! 
 
 
 Uyi 
 
 ■^it'jS^ 
 
 : -^ i ^ 
 
 
 
 --^_1 — — " 
 
 L;;;;^^^^ 
 
 
 
 ~zV 
 
 
 
 m 
 
 the second nodal point, 0.3602 mm. in front of the posterior surface of the lens. 
 (5) The second principal I focus, 14.6470 mm. behind the" posterior surface of the 
 lens; and (6) the first principal focus, 12.8326 in front of the anterior surface of 
 the cornea. 
 
 Listing's Reduced Eye. — The distance between the two principal points, on 
 the two nodal points, is so small (only 0.4 mm.), that practically, without introduc- 
 ing any great error in the construction, we may assume one mean nodal or principal 
 point lying between the two nodal or principal points. By this simple procedure 
 we gain one refractive surface for all the media of the eye, and only one nodal 
 point, through which all the rays of direction from without must pass without be- 
 ing refracted. This schematic simplified eye is called " the reduced eye " of List- 
 ing. 
 
 Formation of the Retinal Image. — The construction of the image on the 
 retina thus becomes very simple. In' distinct vision the inverted image is formed 
 on the retina. Let A B (Fig. 465) represent an object placed vertically in front 
 of the eye. A pencil of rays passes from A into the eye ; the ray of direction, A 
 d, passes without refraction through the nodal point, k. Further, as the focal point 
 for the luminous point, A, is upon the retina, all the rays proceeding from A must 
 reunite in d. The same is true of the rays proceeding from B, and, of course, 
 for rays sent out from an intermediate point of the body, A, B. The retinal image 
 
THE OPHTHALMOMETER. 
 
 765 
 
 is, as it were, an endless mosaic of many foci of the object. As all the rays of 
 direction must pass through the combined nodal point, k, this is also called the 
 " point of intersection of the visual rays." 
 
 The inverted image on the retina is easily seen in an excised eye of an albino rabbit, or in any 
 other eye, by removing a portion of the sclerotic and choroid, and supplying its place with a piece 
 of glass. 
 
 The size of the retinal image may also be calculated, provided we know the size of the object 
 and its distance from the cornea. As the two triangles, A, B, k, and c, d, k, are similar, A, B : 
 c, d =/, k : k. g, so that c, d = (A, B, k, g) :/, k. All these values are krtown, viz., k, g = 
 15.16 mm.; further,/", k = a, k X o,f, where u,f is measured directly, and a, k = 7.44 mm. 
 The size of A B is measured directly. 
 
 The angle, A k B, is called the visual angle, and of course it is equal to the 
 angle c k d. It is evident that the nearer objects, x y, and r s, must have the 
 same visual angle. Hence, all the three objects, A B, x y, and r s, give a retinal 
 image of the same size. Such objects, whose ends when united with the nodal 
 point form a visual angle of the same size, and consequently form retinal images 
 of the same size, have the same " apparent size." 
 
 In order to determine the optical cardinal points by calculation after the method 
 of Gauss, we must know the following factors: — 
 
 1. The refractive indices, which are — for the cornea, 1.377; aqueous humor, 
 1.377 ; lens, 1.454 (as the mean value of all the layers) ; vitreous humor, 1.336 ; 
 air being taken as 1, and water 1.335. 
 
 Fig. 466. 
 
 Scheme of the ophthalmometer of Helmholtz. 
 
 2. The radii of the spherical refractive surfaces, which are — of the cornea, 7.7 
 mm. ; of the anterior surface of the lens, 10.3 ; of the posterior, 6.1 mm. 
 
 3. The distance of the refractive surfaces — from the vertex of the cornea to the 
 anterior surface of the lens, 3.4 mm. ; from the latter to the posterior surface of 
 the lens (axis of the lens), 4 mm. ; diameter of the vitreous humor, 14.6 mm. 
 The total length of the optic axis is 22.0 mm. 
 
 [KUhne's Artificial Eye. — The formation of an inverted image and the other points in the 
 dioptrics of the eye can be studied most effectively on KUhne's artificial eye, the course of the rays 
 of light being visible in water tinged with eosine.] 
 
 The Ophthalmometer. — This is an instrument to enable us to measure the radii of the refrac- 
 tive media of the eye. As the normal curvature cannot be accurately measured on the dead eje 
 {Petit, 1723), owing to the rapid collapse of the ocular tunics, we have recourse to the process of 
 Kohlrausch for calculating the radii of the refractive surfaces -from the size of the reflected images 
 in the. living eye. The size of a luminous body is to the size of its reflected image as the distance of 
 both to half the radius of the convex mirror. Hence it is necessary to measure the size of the re- 
 fleeted image. This is done by means of the ophthalmometer of Helmholtz (Fig. 466). The 
 apparatus is constructed on the following principle : If we observe, an object through a glass plate 
 placed obliquely, the object appears to be displaced laterally ; the displacement becomes greater 
 the more obliquely the plate is moved. Suppose the observer, A, to look through the telescope, F, 
 which has the plate, G, placed obliquely in front of the upper half of its objective, he sees the cor- 
 neal reflected image, a, b, of the eye, B, and the image appears to be displaced laterally, viz., to a', 
 b'. If a second plate, G, be placed in front of the lower half of the telescope, but placed in the 
 opposite direction, so that both plates, corresponding to the middle line of the objective, intersect at 
 an angle, then the observer sees the reflected image, a b, displaced laterally to a", b" . As both 
 glass plates rotate round their point of intersection, the position of both is so selected that both re- 
 
766 ACCOMMODATION OF THE EYE. 
 
 fleeted images just touch each other with their inner margins (so that b' abuts closely upon a"). 
 The size of the reflected image can be determined from the size of the angle formed by both plates, 
 but we must take into calculation the thickness of the glass plates and their refractive indices. The 
 size of the corneal image, and also that in the lens, may be ascertained in the passive eye, and also 
 in the eye accommodated for a near object, and the length of the radius of the curved surface may 
 be calculated therefrom {Helmholtz, Bonders, Mauthner). 
 
 Fluorescence.— All the media of the eye, even the retina, are slightly fluorescent ; the lens 
 most, the vitreous humor least (v. Helmholtz). 
 
 Erect Vision. — As the retinal image is inverted, we must explain how we see 
 objects erect. By a psychical act, the impulses from any point of the retina are 
 again referred to the exterior, in the direction through the nodal point ; thus the 
 stimulation of the point, d (Fig. 465), is referred to A, that of c to B. The 
 reference of the image to the external world happens thus, that all points appear 
 to lie in a surface floating in front of the eye, which is called the field of vision. 
 The field of vision is the inverted surface of the retina projected externally ; 
 hence the field of vision appears erect again, as the inverted retinal image is again 
 projected externally but inverted. 
 
 That the stimulation of any point is again projected in an inverse direction through the nodal 
 point, is proved by the simple experiment that pressure upon the outer aspect of the eyeball is 
 projected or referred to the inner aspect of the field of vision. The entoptical phenomena of the 
 retina are similarly projected externally and inverted; so that, e.g., the entrance of the optic nerve 
 lies external to the yellow Spot (see \ 393). All sensations from the retina are projected externally, 
 
 387. ACCOMMODATION OF THE EYE.— According to No. 2 (p. 760), the rays of 
 light proceeding from a luminous point, e.g., a flame, and acted upon by a collecting (convex) lens, 
 are brought to a focus or focal point, which has always a definite relation to the luminous object. 
 If a projection surface or screen be placed at this distance from the lens, a real and inverted image 
 of the object is obtained upon the screen. If the screen be placed nearer to the lens (Fig. 760, IV, 
 a, b), or further away from it {c, d), no distinct image of the object is formed, but diffusion circles 
 are obtained, because in the former case the rays have not united, and in the latter because the rays, 
 after uniting, have crossed each other and become divergent. If the luminous point be brought 
 nearer to, or removed further from, the lens, in order to obtain a distinct image, in every case the 
 screen must be brought nearer, or removed from the lens, to keep the same distance between the 
 lens and the screen. If, however, the screen be fixed permanently, while the distance between the 
 luminous point and the lens varies, a distinct image can only be obtained upon the screen, provided 
 the lens, as the luminous point approaches it, becomes more convex, i.e., refracts the rays of light 
 more strongly — conversely, when the distance between the luminous point and the lens becomes 
 greater, the lens must become less curved, i. e., refract less strongly. 
 
 In the eye, the projection surface or screen is represented by the retina, which is permanently 
 fixed at a certain distance ; but the eye has the power of forming distinct images of near and 
 distant objects upon the retina, so that the refractive power, i. e.,xh& form of the crystalline lens in 
 the eye, must undergo a change in curvature corresponding in. every case to the distance of the 
 object. [It is important to remember that we cannot see a near object and a distant one with equal 
 distinctness at the same time, and hence arises the necessity for accommodation.] 
 
 Accommodation. — By the term accommodation of the eye is understood the 
 property of the eye, whereby it forms distinct images of distant as well as near 
 objects upon the retina. This power depends upon the fact that the crystalline 
 lens alters its curvature, becoming more- convex (thicker), or less curved 
 (flatter), according to the distance of the object. When the lens is absent from 
 the eyeball, accommodation is impossible (7%. Young, Donders — p. 758). 
 
 During rest [or negative accommodation], or when the eye is passive, it 
 is accommodated for the greatest distance, i. <?., images of objects placed at an 
 infinite distance {e. g. , the moon) are formed upon the retina. In this case, rays 
 coming from such a distance are practically parallel, and when they enter the eye 
 are, in the passive normal (emmetropic) eye, brought to a focus on the retina. 
 When looking at a distant object, a distinct image is formed on the retina without 
 the aid of any muscular action. 
 
 That distant objects are seen without the aid of any muscular action is shown by the following 
 considerations: (1) The normal, or emmetropic, eye can see distant objects clearly and distinctly 
 without our experiencing any feeling of effort. On opening the eyelids after a long period of rest, 
 
ACCOMMODATION. 
 
 767 
 
 the objects at a distance are at once distinctly visible in the field of vision. (2) If, in consequence 
 of paralysis, of the mechanism of accommodation {e.g., through paralysis of the oculomotor nerve — 
 § 345' 7)» * ne eve 1S unable to focus images of objects placed at different distances, still distinct 
 
 Fig. 467. 
 
 Anterior quadrant of a horizontal section of the eyeball, cornea, and lens, a, substantia propria of the cornea; b, 
 Bowman's elastic membrane ; c, anterior corneal epithelium ; d, Descemet's membrane ; e, its epithelium ; f, 
 conjunctiva; g, sclerotic ; h, iris ; i, sphincter iridis ; j, ligamentum pectinatum iridis, with the adjoining vacuo- 
 lated tissue ; k, canal of Schlemm ; /, longitudinal, ///, circular muscular fibres of the ciliary muscle; n, ciliary 
 process ; 0, ciliary part of the retina ; q, canal of Petit, with 2, zonule of Zinn in front of it ; and £, the posterior 
 layer of the hyaloid membrane ; r, anterior, s, posterior part of the capsule of the lens ; t, choroid ; «, pericho- 
 roidal space ; T, pigment epithelium of the iris ; x, margin of the lens. 
 
 Scheme of accommodation for near and distant objects. The right side of the figure represents the condition of the 
 lens during accommodation for a near object, and the left side when the eye is at rest. The letters indicate the 
 same parts on both sides ; those on the right side are marked with a stroke ; A, left, B t right half of the lens ; C, 
 cornea; S, sclerotic; C.S. f canal of Schlemm ; V. JC, anterior chamber; J, iris ; P, margin of the pupil ; V, 
 anterior surface ; ff, posterior surface of the lens ; ft, margin of the lens ; F, margin of the ciliary processes ; a 
 and 6, space between the two former; the line Z, A, indicates the thickness of the lens during accommodation 
 for a near object ; Z, Y, the thickness of the lens when the eye is passive, 
 
 images are obtained of distant objects. Thus, paralysis- of the mechanism of accommodation is 
 always accompanied by inability to focus a near object, never a distant object. A temporary 
 
768 
 
 NERVES. 
 
 paralysis with the same results occurs when a solution of atropin or duboisin is dropped into the 
 eye, and also in poisoning with these drugs (g 392). 
 
 When the eye is accommodated for a near object [positive accommoda- 
 tion], the lens is thicker, its anter ior surface is moje cuxved (convex), and 
 projects further into the anteriorcEamber of~the eye ( Cramer, v. Helmholtz). 
 The mechanism producing this result is the following : During rest the lens is 
 kept somewhat flattened against the vitreous humor lying behind it by the tension 
 of the stretched zonule of Zinn (Fig. 467, Z), which is attached round the margin 
 of the lens. When the muscle of accommodation, the ciliary muscle (/, m), 
 contracts, it pulls forward the margin of the choroid, so that the zonule of Zinn 
 in intimate relation with it is relaxed. [When we accommodate for a near 
 object the ciliary muscle contracts, pulls forward the choroid, relaxes the 
 zonule of Zinn, and this in turn diminishes the tension of the anterior part of 
 the capsule of the lensl] The lens assumes a more curved form in virtue of its 
 elasticity, so that it becomes more convex as soon as the tension of the zonule 
 of Zinn, which keeps it flattened, is diminished (v. Helmholtz). As the posterior 
 surface of the lens lies in the saucer-shaped, unyielding depression of the vitreous 
 humor, the anterior surface of the lens in becoming more convex must neces- 
 sarily protrude more forward. 
 
 Nerves. — According to Hensen and Volckers, the origin of the nerves of accom- 
 modation lies in the most anterior root bundles of the oculomotorius. Stimu- 
 lation of the posterior part of the floor of the third ventricle causes accommoda- 
 tion ; if a part lying slightly posterior to this be stimulated, contraction of the 
 pupil occurs. On stimulating the limit between the third ventricle and the aque- 
 duct there results contraction of the internal rectus muscle, while stimulation 
 of the other parts around the iter causes contraction of the superior rectus, levator 
 palpebrae, rectus inferior and inferior oblique muscles. 
 
 Proofs. — That the lens undergoes an alteration in its curvature during accommodation is proved 
 by the following facts : — 
 
 1. Purkinje-Sanson's Images. — If a lighted candle be held atone side of the eye, or if light 
 be allowed to fall on the eye through two triangular holes, placed above each other and cut in a 
 piece of cardboard, the observer will see in the latter case three pairs of reflected images [in the 
 lormer, three images]. The brightest and most distinct image (or pair of images) is erect, and is 
 
 Fig. 469. 
 
 Fig. 470. 
 
 Sanson-Purkinje's images, a, b, c, during negative, 
 and a n b„ c ft positive accommodation. 
 
 produced by the anterior surface of the cornea (Fig. 
 469, a). The second image (or pair of images) is also 
 erect. It is the largest, but it is not so bright (*), and it 
 is reflected by the anterior surface of the lens. (The 
 size of a reflected image from a convex mirror is greater 
 the longer the radius of curvature of the reflecting surface.) 
 The latter image lies 8 mm. behind the plane of the pupil. 
 The third image (or pair of images) is of medium size and 
 medium brightness — it is inverted and lies nearly in the 
 plane of the pupil (c). The posterior capsule of the lens 
 which reflects the last image acts like a concave mirror. 
 If a luminous object be placed at a distance from a con- 
 cave mirror, its inverted, diminished, real image lies close 
 to the focus toward the side of the object. If the images 
 
 Phakoscope of Helmholtz. 
 
CHANGES DURING ACCOMMODATION. 769 
 
 be studied when the observed eye is passive, i.e., in the phase of negative accommodation, on asking 
 the person experimented upon to accommodate his eye for a near object, at once a change in the 
 relative position and size of some of the images is apparent. The middle pair of images reflected 
 by the anterior surface of the lens diminish in size and approach each other (b,), which depends 
 upon the fact that the anterior surface of the lens has become more convex. At the same time the 
 image (or pair of images) comes nearer to the image formed by the cornea (a, and c,) as the 
 anterior surface of the lens lies nearer to the cornea. The other images (or pairs of images) 
 neither change their size nor position, v. Helmholtz, with the aid of the ophthalmometer, has 
 measured the diminution of the radius of curvature of the anterior surface of the lens during accom- 
 modation for a near object. 
 
 [Phakoscope. — These images may be readily shown by means of the phakoscope of v. Helm- 
 holtz (Fig. 470). It consists of a triangular box blackened inside and with its angles cut off. The 
 observer's eye is placed at a, while on the opposite side of the box are two prisms, b, b 1 ; the 
 observed eye is placed at the side of the box opposite to C. When a candle is held in front of the 
 prisms, b and b 1 , three pairs of images are seen in the observed eye. Ask the person to accommo- 
 date for a distant object, and note the position of the images. On pushing up the slide, C, with a 
 pin attached to it, and asking him to accommodate for the pin, i.e., for a near object, the position 
 and size of the middle images chiefly will be seen to alter as described above.] 
 
 2. In consequence of the increased curvature of the lens during accommodation for a near 
 object, the refractive indices within the eye must undergo a change. According to v. Helmholtz, 
 the following measurements obtain in negative and positive accommodation respectively :— 
 
 Accommodation. 
 
 Radius of the cornea 
 
 Radius of anterior surface of lens 
 
 Radius of posterior surface of lens 
 
 Position of the vertex of the outer surface of the lens behind 
 
 the vertex of the cornea 
 
 Position of the posterior vertex of the lens 
 
 Position of the anterior focal point 
 
 Position of the first principal point 
 
 Position of the second principal point 
 
 Position of the posterior focal point behind the anterior vertex 
 
 of the cornea 
 
 22.23 
 
 Negative — Mm. 
 
 Positive — Mm. 
 
 8 
 
 8 
 
 10 
 
 6 
 
 6 
 
 5-5 
 
 3-6 
 
 3-2 
 
 7.2 
 
 7.2 
 
 12.9 
 
 11.24 
 
 1.94 
 
 2.03 
 
 6.96 
 
 6.5. 
 
 20.25 
 
 3. Lateral View of the Pupil. — If the passive eye be looked at from the side, we observe only 
 a small black strip of the pupil, which becomes broader as soon as the person experimented on ac- 
 commodates for a near object, as the whole pupil is pushed more forward. 
 
 4. Focal Line. — If light be admitted through the cornea into the anterior chamber, the " focal 
 line " formed by the concave surface of the cornea falls upon the iris. If the experiment be made 
 upon a person whose eye is accommodated for a distant object, so that the line lies near the margin 
 of the pupil, it gradually recedes toward the scleral margin of the iris, as soon as the person ac- . 
 commodates for a near object, because the iris becomes more oblique as its inner margin is pushed 
 forward. 
 
 5. Change in Size of Pupil. — Oh accommodating for a near object, the pupil contracts, 
 while in accommodation for a distant object it dilates (Descartes, 1637). The contraction takes 
 place slightly after the accommodation (ponders). This phenomenon may be regarded as an 
 associated movement, as both the ciliary muscle and the sphincter pupillse are supplied by the 
 oculomotorius (g 345, 2, 3). A reference to Fig. 467 shows that the latter also directly supports the 
 ciliary muscle; as the inner margin of the iris passes inward (toward r), its tension tends to be 
 propagated to the ciliary margin of the choroid, which also must pass inward. The ciliary pro- 
 cesses are made tense, chiefly by the ciliary muscle (tensor choroidse). Accommodation can still 
 be performed, even though the iris be absent or cleft. 
 
 6. Internal Rotation of the Eye. — On rotating the eyeball inward, accommodation for a near 
 object is performed involuntarily. As rotation of both eyeballs inward takes place when the axes 
 of vision are directed to a near object, it is evident that this must be accompanied involuntarily by 
 an accommodation of the eye for a near object. 
 
 7. Time for Accommodation. — A person can accommodate from a near to a distant object 
 (which depends upon relaxation of the ciliary muscle) much more rapidly than conversely, from a 
 distant to a near object ( Vierordt, Aeby). The process of accommodation requires a longer time the 
 nearer the object is brought to the eye ( Vierordt, Vblckers, and Hensen). The time necessary for 
 the image reflected from the anterior surface of the lens to change its place during accommodation 
 is less than that required for subjective accommodation (Aubert and Angelucci). 
 
 49 
 
770 
 
 REFRACTIVE POWER OF THE EYE. 
 
 I 
 
 8. Line of Accommodation. — When the eye is placed in a certain position during accommo- 
 dation, we may see not one point alone distinctly, but a whole series of points behind each other. 
 Czermak called the line in which these points lie the line of accommodation. The more the eye 
 is accommodated for a distant object the longer this line becomes. All objects placed at a greater 
 distance from the eye than 60 to 70 metres appear equally distinct to the eye. The line becomes 
 shorter the more we accommodate for a near object, i. e., when we accommodate as much as pos- 
 sible for a near object, a second point can only be seen indistinctly at a short distance behind the 
 object looked at. 
 
 9. The nerves concerned in the mechanism of accommodation are referred to under Oculomo- 
 torius ({! 345, and again in g 704). 
 
 Scheiner's Experiment. — The experiment which bears the name of Scheiner 
 (1619) serves to illustrate the refractive action of the lens during accommodation 
 
 for a near object as well as for a distant 
 Fig. 471. object. Make two small pin holes (S, d) 
 
 r R in a cardboard (Fig. 471, K, Kj), the holes 
 
 being nearer to each other than the diam- 
 eter of the pupil. On looking through 
 these holes, S, d, at two needles (/ and r) 
 placed behind each other, then on accom- 
 modating for the near needle (/), the far 
 needle (r) becomes double and inverted. 
 On accommodating for the near needle 
 (/), of course the rays proceeding from it 
 fall upon the retina at the focus (/,) ; while 
 the rays coming from the far needle (f) 
 have already united and crossed in the vit- 
 reous humor, whence they diverge more and 
 more and form two pictures (r t , r tl ) on the 
 retina. If the right hole in the cardboard 
 (</) be closed, the left picture on the retina 
 < (/■„) of the double images of the far needle 
 disappears. An analogous result is obtained 
 on accommodating for the far needle (R). 
 The near needle (P) gives a double image 
 (P /; P^), because the rays from it have not 
 yet come to a focus. On closing the right 
 hole (d t ), the right double image (P,) dis- 
 appears {Porterfield). When the eye of 
 the observer is accommodated for the near 
 needle, on closing one aperture the double 
 image of the distant point disappears on that side ; but if the eye is accommo- 
 dated for the distant needle, on closing one hole' the crossed image of the near 
 needle disappears. 
 
 388. REFRACTIVE POWER OF THE EYE— ANOMALIES 
 OF REFRACTION.— Far Point— Near Point.— The limits of distinct 
 vision vary very greatly in different eyes. We distinguish the far point [p. r., 
 punctum remotum] and the near [p. p., punctum proximum] ; the former 
 indicates the distance to which an object may be removed from the eye, and may 
 still be seen distinctly; the latter the distance to which any object may be brought 
 to the eye, and may still be seen distinctly. The distance between these two 
 points is called the range of accommodation. The types of eyeball are 
 characterized as follows : — 
 
 1. The normal or emmetropic eye is so arranged when at rest that parallel 
 rays (Fig. 472, r, r) coming from the most distant objects can be focussed on the 
 retina (r,). The far point, therefore, is = 00 (infinity). When accommodating 
 as much as possible for a near object, whereby the convexity of the lens is 
 
 Scheiner's experiment. 
 
MYOPIC AND HYPERMETROPIC EYES. 
 
 771 
 
 Condition of refraction in the normal passive eye and during 
 accommodation. 
 
 increased (Fig. 472, a), rays from Fig. 472. 
 
 a luminous point placed at a dis- 
 tance of s inches are still focussed 
 on the retina, i.e., the near point is 
 = 5 inches (1 inch = 27 mm.). 
 The range of accommodation, or 
 ["the range of distinct vision"'], 
 therefore, is from 5 inches (10-12 
 cm.) to 00 . 
 
 2. The short-sighted (myopic 
 or long) eye (Fig. 473) cannot, when 
 at rest, bring parallel rays from 
 infinity to a focus on the retina. 
 These rays decussate within the 
 vitreous humor (at O), and after 
 crossing form a diffusion circle upon 
 the retina. The object must be re- 
 moved from the passive eye to a 
 
 distance of 60 to 120 inches (to/), in order that the rays may be focussed on the 
 retina. The passive myopic eye, therefore, can only focus divergent rays upon 
 the retina. The far point, therefore, lies abnormally near. With an intense 
 effort at accommodation, objects at a distance of 4 to 2 inches, or even less, from 
 
 Fig. 473. 
 
 
 Myopic eye. 
 
 the eye may be seen distinctly. The near point, therefore, lies abnormally near ; 
 the range of accommodation is diminished. 
 
 Short-sightedness, or myopia, usually depends upon congenital, and frequently hereditary, 
 elongation of the eyeball. This anomaly of the refractive media is easily corrected by using a 
 diverging lens (concave), which makes parallel rays divergent, so that they can then be brought 
 to a focus on the retina. It is remarkable that most children are myopic when they are born. This 
 myopia, however, depends upon a two-curved condition of the cornea and lens, and on the lens 
 being too near to the cornea. As the eye grows, this short-sightedness disappears. The cause of 
 myopia in children is ascribed to the continued activity of the ciliary muscle in reading, writing, 
 etc., or the continued convergence of the eyeballs, whereby the external pressure upon the eyeball 
 is increased. 
 
 3. The long-sighted eye (Fig. 474), hypermetropic, hyperoptic (flat eye), 
 when at rest, can only cause convergent rays to come to a focus on the retina. 
 Distinct images can only be formed when the rays proceeding from objects are 
 rendered convergent by means of a convex lens, as parallel rays would come to a 
 focus behind the retina (at /). All rays proceeding from natural objects are 
 either divergent, or at most nearly parallel, never convergent. Hence it follows 
 that no long-sighted person, when the eye ispassive, i.e., is negatively accommo- 
 dated, can see distinctly without a convex lens. When the ciliary muscle con- 
 tracts, slightly convergent, parallel, and even slightly divergent rays may be 
 focussed, according to the increasing degree of the accommodation. The far 
 
772 
 
 THE POWER OR FORCE OF ACCOMMODATION. 
 
 Fig. 474. 
 
 Hypermetropic eye. 
 
 point of the eye is negative, the near 
 point abnormally distant (over 8 to 80 
 inches), while the range of accommo- 
 dation is infinitely great. 
 
 The cause of hypermetropia is abnormal 
 shortness of the eye, which, is generally due 
 fc-'—s^rf h to imperfect development in all directions. 
 It is corrected by using a convex lens. 
 
 [Defective Accommodation. — 
 In the presbyopic eye, or long- 
 sighted eye of old people, the near 
 point is farther away than normal, but 
 the far point is still unaffected. In such cases the person cannot see a near object 
 distinctly, unless it be held at a considerable distance from the eye. It is due to 
 a defect in the mechanism of accommodation, the lens becoming somewhat flatter, 
 less elastic, and denser with old age, while the ciliary muscle becomes weaker. 
 In hypermetropia, on the contrary, the mechanism of accommodation may be 
 perfect, yet from the shape of the eye the person cannot focus on his retina the 
 rays of light from a near object. In presbyopia the range of distinct vision is 
 diminished. The defect is remedied by weak convex glasses. The defect 
 usually begins about forty-five years of of age.] 
 
 Estimation of the Far Point — Snellen's Types. — In order to determine the far point of an 
 eye, gradually bring nearer to the eye objects which form a visual angle of 5 minutes («. g., Snel- 
 len's small type letters, or the medium type, 4 to 8, of Jaeger), until they can be seen distinctly. 
 The distance from the eye indicates the far point. In order to determine the far point of a myopic 
 person, place at 20 inches distant from the eye the same objects which give a visual angle of 5 
 minutes, and ascertain the concave lens which will enable the person to see the objects distinctly. 
 To estimate the near point, bring small objects (e. g., the finest print), nearer and nearer to the eye, 
 until it finally becomes indistinct. The distance at which one can still see distinctly indicates the 
 far point. 
 
 Optometer. — The optometer may also be used to determine the near and far points. A small 
 object, e. g., a needle, is so arranged as to be movable along a scale, along which the eye to be in- 
 vestigated can look as a person looks along the sight of a rifle. The needle is moved as near as 
 possible, and then removed as far as possible, in each case as long as it is seen distinctly. The dis- 
 tance of the near and far point and the range of accommodation can be read off directly upon the 
 scale (Grdfe). 
 
 389. THE POWER OR FORCE OF ACCOMMODATION.— Force of Accommoda- 
 tion. — The range of accommodation, which is easily determined experimentally, does not by itself 
 determine the proper power or force of accommodation. The measure of the latter depends upon the 
 mechanical work done by the muscle of accommodation, or the ciliary muscle. Of course, this 
 cannot be directly determined in the eye itself. Hence this force is measured by the optical effect, 
 which results in consequence of the change in the shape of the lens, brought about by the energy of 
 the contracting muscle. 
 
 In the normal eye, during the passive condition, the rays coming from infinity, and, therefore, 
 parallel (which are dotted in Fig. 475), are focussed upon the retina at f If rays coming from a 
 distance of 5 inches (p. 773) are to be focussed, the whole available energy of the ciliary muscle 
 must be brought into play to allow the lens to become more convex, so that the rays may be brought 
 to a focus at f The energy of accommodation, therefore, produces an optical effect in as far as it 
 
 increases the convexity of the anterior 
 Fig. 475. surface of the passive lens (A), by the 
 
 '" amount indicated by B. Practically, 
 
 we may regard the matter as if a new 
 convex lens (B) were added to the ex- 
 isting convex lens (A). What, there- 
 fore, must be the focal distance of the 
 lens (B) in order that rays coming 
 from the near point (5 inches) may be 
 focussed upon the retina at /? Evi- 
 dently the lens B must make the diverg- 
 ing rays coming from p parallel, and 
 then A can focus them at /. Convex 
 
SPECTACLES. 773 
 
 lenses cause those rays proceeding from their focal points to pass out at the other side as parallel 
 rays (g 385, I). In our case, therefore, the lens must have a focal distance of 5 inches. The nor- 
 mal eye, therefore, with the far point = 00, and the near point = 5 inches, has a power of accom- 
 modation equal to a lens of 5 inches focal distance. When the lens by the energy of accommoda- 
 tion is rendered more powerfully refractive, the increase (B) can readily be eliminated by placing be- 
 fore the eye a concave lens which possesses exactly the opposite optical effect of the increase of ac- 
 commodation (B). Hence, it follows that it is possible to indicate the power (force) of accommo- 
 dation of the eye by a lens of a definite focal distance, i.e, by the optical effect produced by the latter. 
 Therefore, according to Donders, the measure of the force of accommodation of the eye is the 
 reciprocal value of the focal distance of a concave lens, which, when placed before the accommo- 
 dated eye, so refracts the rays of light coming from the near point (p) as if they came from the far 
 point. 
 
 Example. — We may calculate the force of the accommodation according to the following for- 
 mula: — = — — , i.e., the force of accommodation, expressed as the dioptric value of a lens (of x 
 
 inch focal distance), is equal to the difference of the reciprocal values of the distances of the near 
 point (p) and of the far point {r) of the eye. In the emmetropic eye, as already mentioned,/ = 5> 
 
 r = 00. Its force of accommodation is, therefore, - — — 5 , so that x = 5, i. <?., it is equal to a 
 
 x p o 
 
 lens of 5 inches focal distance. In a myopic eye,/ = 4, r = 12, so that - = , i.e., x =. 
 
 6. In another myopic eye, with/ = 4 and r= 20, then x = 5, which is a normal force of accom- 
 modation. Hence, it is evident that two different eyes, possessing a very different range of accom- 
 modation, may, nevertheless, have the same force of accommodation. Example. — The one eye has 
 
 / = 4, r = 00 , the other, / = 2, r = 4. In both cases, - = - , so that the force of accommoda- 
 
 x 4 
 tion of both eyes is equal to the dioptric value of a lens of 4 inches focal distance. Conversely, two 
 eyes may have the same range of accommodation, and yet their force of accommodation be very 
 unequal. Example. — The one eye hasp = 3, r = 6 ; the other/ = 6, r = 9. Both, therefore, 
 
 have a range of accommodation of 3 inches. For these, the force of accommodation, - = --,, 
 
 x 3 6 
 
 x = 6 ; and -=> — , x = 18. 
 x 6 9 
 
 Relation </the range to the force of accommodation. — The general law is, that the ranges of 
 accommodation of two eyes being equally great, then their forces of accommodation are equal, pro- 
 vided that their near points are the same. If the ranges of accommodation for both eyes are equally 
 great, but their near points unequal, then the forces of accommodation are also unequal — the latter 
 being greater in the eyes with the smallest near point. This is due to the fact that every difference 
 of distance near a lens has a much greater effect upon the image compared with differences in the 
 distance far from a lens. The emmetropic eye can see distinctly objects at 60 to 70 metres, and 
 even to infinity, without accommodation. 
 
 While / and r may be directly estimated in the emmetropic and myopic eyes, this is impossible 
 with the hypermetropic (long-sighted) eye. The far point in the latter is negative, indeed in every 
 pronounced hypermetropia even the near point may be negative. The far point may be estimated 
 by making the hypermetropic eye practically a normal eye by using suitable convex lenses. The 
 relative near point may then be determined by means of the lens. 
 
 Even from the 15th year onward, the power of accommodation is generally diminished for near 
 objects —perhaps this is due to a diminution of the elasticity of the lens {Donders). 
 
 390. SPECTACLES. — The focal distance of concave (diverging) as well as convex (converg- 
 ing) spectacles depends upon the refractive index of the glass (usually 3 : 2), and on the length of 
 the radius of curvature. If the curvature of both sides of the lens is the same (biconcave or bicon- 
 vex), then with the ordinary refractive index of glass the focal distance is the same as the radius of 
 curvature. If one surface of the lens is plane, then the focal distance is twice as great as the radius 
 of the spherical surface. Spectacles are arranged according to their focal distance in inches, but a 
 lens of shorter focal distance than I inch is generally not used. They may also be arranged accord- 
 ing to their refractive power. In this case the refractive power of a lens of I inch focus is taken 
 as the unit. A lens of 2 inches focus refracts light only half as much as the unit measure of 1 inch 
 focus ; a lens of 3 inches focus refracts "^ as strongly, etc. This is the case both with convex and 
 concave lenses, the latter, of course, having a negative focal distance; thus, " concave — W " indi- 
 cates that a concave lens diverges the rays of light one-eighth as strongly as the concave lens of 1 inch 
 (negative) focal distance. 
 
 Choice of Spectacles. — Having determined the near point in a myopic eye, of course we re- 
 quire to render parallel the divergent rays coming from the far point, just as if they came from infin- 
 ity. This is done by selecting a concave lens of the focal distance of the far point. The greatest 
 distance is the far point of the emmetropic eye. Suppose a myopic eye with a far point of 6 inches 
 
7'74 CHROMATIC AND SPHERICAL ABERRATION. 
 
 then such a person requires a concave lens of 6 inches focus to enable him to see distinctly at the 
 greatest distance. Thus, in a myopic eye, the distance of the far point from the eye is directly equal 
 to the focus of the (weakest) concave lens, which enables one to see distinctly objects at the greatest 
 distance. These lenses generally have the same number as the spectacles required to correct the 
 defect. Example. — A myopic eye with a far point of 8 inches requires a concave lens of 8 inches 
 focus, i.e., the concave spectacle, No. 8. For the hypermetropic (long-sighted) eye, the focal dis- 
 tance of the strongest convex lens, which enables the hypermetropic eye to see the most distant 
 objects distinctly, is at the same time the distance of the far point from the eye. Example. — A 
 hypermetropic eye which can see the mos^ distant objects with the aid of a convex lens of 12 inches 
 focus has a far point of 1 2 ; the proper spectacles is convex, No. 1 2. 
 
 [Dioptric. — The focal length of a lens used to be expressed in inches, and as the unit was taken 
 as I inch, necessarily all weaker lenses were expressed in fractions of an inch. In the method 
 advocated by Donders, the standard is a lens of a focal distance of I metre (33.337 English inches, 
 about 40 inches), and this unit is called a dioptric. Thus, the standard is a weak lens, so that the 
 stronger lenses are multiples of ^his. Thus, a lens of 2 dioptrics is = one of about 20 inches 
 focus; 10 dioptrics = 4 inches focus; and so on. The lenses are numbered from No. I, i. e., I 
 dioptric, onward. It is convenient to use signs instead of the words convex and concave. For 
 convex the sign plus -\- is used, and for concave the sign minus — . Thus, a -|- 4.0 means a convex 
 lens of 4 dioptrics, and a — 4.0 = a concave lens of 4 dioptrics.] 
 
 In all cases of myopia or hypermetropia the person ought to wear the proper spectacles. In a 
 myopic eye, when the far point is still more than 5 inches, the patient ought always to wear spec- 
 tacles ; but generally the working distance, e. g., for reading, writing, and for handicrafts, is about 
 12 inches from the eye. If the person desires to do finer work (etching, drawing), requiring the 
 object to be brought nearer to the eye, so as to obtain a larger image upon the retina, then he should 
 either remove the spectacles altogether or use a weaker pair. 
 
 The hypermetropic person ought to wear his convex spectacles when looking at a near object, 
 and especially when the illumination is feeble, because then, owing to the dilatation of the pupil, the 
 diffusion circles of the eye tend to become very pronounced. It is advisable to wear at first convex 
 spectacles which are slightly too strong. Cylindrical lenses are referred to under Astigmatism. 
 Spectacles provided with dull-colored or blue glasses are used to protect the retina when the light 
 is too intense. Stenopaic spectacles are narrow diaphragms placed in front of the eye, which 
 cause it to move in a definite direction in order to see through the opening of the diaphragm. 
 
 391. CHROMATIC AND SPHERICAL ABERRATION, ASTIG- 
 MATISM.— Chromatic Aberration. — All the rays of white light, which 
 undergo refraction, are at the same time broken up by dispersion into a bundle of 
 rays, which, when they are received on a screen, form a spectrum. This is due 
 to the fact that the different colors of the spectrum possess different degrees of 
 refrangibility. The violet rays are refracted most strongly, the red rays least. 
 
 A white point on a black ground does not form a sharp simple image on the retina, but many 
 colored points appear after each other. If the eye is accommodated so strongly as to focus the 
 violet rays to a sharp image, then all the other colors must form concentric diffusion circles, which 
 become larger toward the red. In the centre of all the circles, where all the colors of the spectrum 
 are superposed, a white point is produced by their mixture, while around it are placed the colored 
 circles. The distance of the focus of the red rays from that of the violet in the eye = 0.58 to 0.62 
 mm. The focal distance for red is, according to v. Helmholtz, for the reduced eye, 20.524 mm.; 
 for violet, 20.140 mm. Hence the near and far points for violet light are nearer each other than in 
 the case of red light; white objects, therefore, appear reddish -when beyond the far point, but when 
 nearer than the near point they are violet. Hence the eye must accommodate more strongly for 
 red rays than for violet, so that we judge red objects to be nearer us than violet objects placed at an 
 equal distance (Briicke). 
 
 Monochromatic or Spherical Aberration. — Apart from the decomposition or dispersion of 
 white light into its components, the rays of white light, proceeding from a point if transmitted 
 through refractive spherical surfaces, we find that before the rays are again brought to a focus, the 
 marginal rays are more strongly refracted than those passing through the central parts of the lens. 
 Hence there is not one focus, but many. In the eye this defect is naturally corrected by the iris, 
 which, acting as a diaphragm, cuts off the marginal rays (Fig. 465), especially when the lens is 
 most convex, when the pupil also is' most contracted. In addition, the margin of the lens has less 
 refractive power than the central substance ; lastly, the margins of the refractive spherical surfaces 
 of the eye are less curved toward their margins than the parts lying nearer to the optical axis. 
 Compare the form of the cornea (p. 750) and the lens (p. 757). 
 
 Imperfect Centring of the Refractive Surfaces. — The sharp projection of an image is some- 
 what interfered with by the fact that the refractive surfaces are not exactly centred (Briicke). Thus, 
 the vertex of the cornea is not exactly in the termination of the optic axis; the vertices of both 
 surfaces of the lens, and even the different layers of the lens itself, are not exactly in the optic axis. 
 The variations, however, and the disturbances produced thereby, are very small indeed. 
 
FUNCTIONS OF THE IRIS. 
 
 775 
 
 Regular Astigmatism. — When the curvature of the refractive surfaces of the eye is unequally- 
 great in its different meridians, of course the rays of light cannot be united or focussed in one point. 
 Generally, in such cases, the cornea is more curved in its vertical meridian and least in the hori- 
 zontal (as is shown by ophthalmometry: measurements, p. 765). The rays passing through the 
 vertical meridian come to a focus, first, in a horizontal focal line ; while the rays entering horizon- 
 tally unite afterward in a vertical line. There is thus no common focus for the light rays in the 
 eye ; hence the name astigmatism. The lens, also, is unequally curved in its meridians, but it is 
 the reverse of the cornea ; consequently, a part of the inequality of the curvature of the cornea is 
 thereby compensated, and only a part of it affects the rays of light. The emmetropic eye has a very 
 slight degree of this inequality (normal astigmatism). If two very fine lines of equal thickness be 
 drawn on white paper, so as to intersect each other at right angles.it will be found that, in order to see 
 the horizontal line quite sharply, the paper must be brought slightly nearer to the eye than when 
 
 Fig. 476. 
 
 Action of an astigmatic surface on a cone of light (Frost). 
 
 Fig. 477. 
 
 we focus the vertical line. When the inequality of curvature of the meridians is considerable, of 
 course exact vision is no longer possible. 
 
 [Fig. 476 shows the effect of an astigmatic surface on the rays of light. Let a b c d be such a 
 surface, and suppose diverging rays to proceed from/. The rays passing through c d come to a 
 focus at/j, while those passing through the vertical meridian are focussed at/ 2 . The outline of 
 the cone of rays between a b c dsxAf l varies, as shown in the figure. At a certain part it is oval, 
 with its axis vertical, at another the long axis of the oval is horizontal, while at other places it is 
 circular, or the rays are focussed in a horizontal or vertical line.] 
 
 Correction. — This condition is corrected by a cylindrical lens, i.e., a lens so cut as to be with- 
 out curvature in one direction, while in the other direction (vertical to the former) it is curved. 
 The lens is placed in front of the eye, so that the direction of its curvature coincides with the 
 direction of least curvature of the eye (v. Helmholtz, Knapp, Bonders). 
 The section C a b c d of the cylindrical lens (Fig. 477) represents a plano- 
 convex, the section C a /3 y 8, a concavo-convex 'lens. 
 
 [Test. — Draw to lines of equal thickness at right angles to each other. 
 An astigmatic person cannot see both lines with equal distinctness at the 
 same time, one line will appear thicker than the other. Or a series of lines 
 radiating from a centre may be used (astigmatic clock) ; when that line 
 which is parallel to the astigmatic meridian will be seen most distinctly ; 
 while, with the vertical meridian most curved, it would be the vertical 
 line.] 
 
 Irregular Astigmatism. — Owing to the radiate arrangement of the 
 fibres in the interior of the crystalline lens, and in consequence of the 
 unequal course of the fibres within the different parts of one and the same 
 meridian of the lens, the rays of light passing through one meridian of 
 the lens, cannot all be brought to one focus. Hence, we do not obtain a 
 distinct, sharp image of distant luminous points, such as stars or street 
 lamps, but we see a radiate jagged figure provided with rays. The same 
 obtains on holding a piece of cardboard with a small hole in it toward 
 the light, at a distance from the eye slightly greater than the far point. 
 Slight degrees of this irregular astigmatism are normal, but when it is 
 highly developed it greatly interferes with vision, by forming several foci 
 of an object instead of one Polyopia monocularis). Of course this condition cannot obtain in 
 an eye devoid of a lens. 
 
 392. THE IRIS. — Functions. — i. The iris acts like a diaphragm in an 
 optical apparatus by cutting off the marginal rays (Fig. 465), which, if they 
 entered the eye, would cause spherical aberration, and thus produce indistinct 
 vision. 
 
 Cylindrical glasses for astig- 
 matism. 
 
776 MOVEMENTS OF THE IRIS. 
 
 2. As the pupil contracts strongly in a bright light, and dilates when the light 
 is feeble, it regulates the amount of light entering the eye ; thus fewer rays 
 enter the eye when the light is strong than when it is feeble. 
 
 3. To a certain extent it supports the action of the ciliary muscle. 
 Muscles and Nerves. — The iris is provided with two sets of muscular fibres 
 
 — the sphincter, which immediately surrounds the pupil and is supplied by the 
 oculomotorius (§ 345, 2), and the dilator pupillas (p. 754), supplied chiefly by 
 the cervical sympathetic (§ 356, A, 1), and the trigeminus (§ 347, 3). Both 
 muscles stand in an antagonistic relation to each other (§ 345), the pupil dilates 
 moderately after section or paralysis of the oculomotorius, owing to the contrac- 
 tion of the dilator fibres which are supplied by the cervical sympathetic ; con- 
 versely, the pupil contracts when the sympathetic is divided or extirpated {Petit, 
 17 2f). When both nerves are stimulated simultaneously, the pupil contracts, so 
 that the excitability of the oculomotorius overcomes the sympathetic. 
 
 [The existence of a dilator pupillse muscle is not universally recognized, and in fact some 
 observers doubt its existence. The muscular nature of the radial fibres in the posterior limiting 
 membrane of the iris is denied by Grunhagen, while Koganei regards these as in no case muscular, 
 and that the dilating fibres are represented by fibres radiating from the iris. These fibres are well 
 developed in birds and the otter, exist in traces in the rabbit, and are absent in man. Gaskell 
 points out that in this case the size of the pupil must in part depend on the elasticity of the radial 
 fibres of the iris, while the dilator nerve fibres must act on the sphincter fibres, causing them to 
 relax. Gaskell groups the sphincter of the iris with those muscles " supplied by two nerves of oppo- 
 site character, the one motor the other inhibitory."] 
 
 Nerves. — Arnstein and A. Meyer have studied the mode of termination of the nerve fibres in 
 the iris. All the medullated nerve fibres lose their white sheaths after a time ; most of the fibres 
 {motor) in the region of the sphincter consist of naked bundles of fibrils. A network of very deli- 
 cate sensory nerves lies under the anterior epithelium. Numerous fibrils pass to the capillaries and 
 arteries as vasomotor nerves. [Many ganglionic cells are intercalated in the course of the fibres.] 
 
 Movements of the iris occur under the following conditions : — 
 
 1 . Action of light on the retina causes (according to its intensity and amount) a correspond- 
 ing contraction of the pupil ; the same effect is produced by stimulation of the optic nerve itself 
 (Herbert Mayo, f 1852). This movement is a reflex act [the afferent nerve being the optic and 
 the efferent the oculomotorius; the impulse is transferred from the former to the latter in a centre 
 situated somewhere below the corpora quadrigemina (Fig. 478, C)]. The older observers locate 
 the centre in the corpora quadrigemina, the recent observers in the medulla oblongata (p. 737). 
 Both pupils always react, although only one retina be stimulated; generally, under normal circum- 
 stances both contract to the same extent (Danders), owing to the intercentral communication 
 [coupling] of the two pupillo-constricting centres. [This is called consensual contraction of the 
 pupil.]' After section of the optic nerve the pupil dilates, and subsequent section of the oculomo- 
 torius no longer produces any further dilatation (Knoll). 
 
 2. The centre for the dilator fibres of the pupil (pupillo-dilating centre) is excited by dysp- 
 nceic blood (§ 367, 8). If the dyspnoea ultimately passes into asphyxia, the dilatation of the pupil 
 diminishes. Of course, if the peripheral dilating fibres (g 247, 3) [e.g., the sympathetic nerve in 
 the neck] be previously divided, this effect cannot take place, as the dyspnceic blood acts on the 
 centre and not on the nerve fibres. 
 
 3. The centre, as well as the subordinate " cilio-spinal region" of the spinal cord (\ 362, 1), 
 is also capable of being excited reflexly ; painful stimulation of sensory nerves, in addition to 
 causing protrusion of the eyeballs (§ 347), a fact proved in the case of persons subjected to torture, 
 produces dilatation of the pupils (Arndt, Bernard, Westphal, Luchsinger) ; while a similar effect 
 is caused by labor pains, a loud call in the ear, stimulation of the nerves of the sexual organs, and 
 even by slight tactile impressions (Foa and ' Schiff). According to Bechterew, the foregoing results 
 are due to inhibition of the light reflex in the sense expressed in \ 361, 3. 
 
 4. The condition of the blood vessels of the iris influences the size of the pupil ; all condi- 
 tions causing injection or congestion of these vessels contract the pupil, all conditions diminishing 
 them dilate it. The pupil, therefore, is contracted by forced expiration, which prevents the return 
 of venous blood from the head, momentarily by every pulse beat, owing to the diastolic filling of 
 the arteries; diminution of the intraocular pressure, e. g., after puncture of the anterior chamber, 
 because, owing to the diminished intraocular pressure, there is less resistance to the passage of blood 
 into the blood vessels of the iris (Hensen and Volckers) ; paralysis of the vasomotor fibres of the 
 iris (§ 347, 2). Conversely, the pupil is dilated by conditions the reverse of those already men- 
 tioned, and also by strong muscular exertion, whereby blood flows freely into the dilated muscular 
 blood vessels ; also when death takes place. The condition of the filling of the blood vessels also 
 explains the fact that the pupil dilated with atropin becomes smaller when a part of the sympathetic 
 in the upper cervical ganglion, carrying the vasomotor fibres of the iris; is excised ; also, that after 
 
ACTION OF DRUGS ON THE PUPIL. 
 
 777 
 
 extirpation of this ganglion atropin always causes a less diminution of the pupil on this side. The 
 fact that when the pupil is already dilated by stimulation of the sympathetic, it is further dilated by 
 atropin, is due to a diminished injection of the blood vessels of the iris. If an animal with its pupils 
 dilated with atropin be rapidly bled, the pupils contract, owing to the anaemic stimulation of the origin 
 of the oculomotorius (Moriggia). The dilatation of the pupils observed in cases of neuralgia of 
 the trigeminus is partly due to the stimulation of the dilating fibres, partly to the stimulation of the 
 vasomotor fibres of the iris ((! 347, 2). 
 
 5. Contraction of the pupil occurs as an associated movement during accommodation for a 
 near object (p. 769), and when the eyeballs are rotated inward, which is the case during sleep 
 (p. 708). Conversely, intense movements of the iris, caused by variations in the brightness of 
 dazzling illumination, e. g., of the electric light, are followed by disturbing associated movements 
 of the ciliary muscle (Ljubinsky). In certain movements discharged from the medulla oblongata 
 (forced respiration, chewing, swallowing, vomiting), dilatation of the pupil occurs as a kind of asso- 
 ciated movement. 
 
 [Argyll Robertson Pupil. — In this condition the pupil does not contract to light, although it 
 contracts when the eye is accommodated for a near object, vision usually being normal. The lesion 
 is situated on those structures connecting the afferent and efferent fibres at their central ends (at /± 
 in Fig. 478), i. e., the connection between the corpora quadrigemina and the oculomotorius. It is 
 most frequently found in locomotor ataxia, although it also occurs in progressive paralysis of the 
 insane.] 
 
 Direct stimulation at the margin of the cornea causes dilatation of the pupil (E. H. Weber) ; in 
 fact, direct stimulation of circumscribed areas of the margin of the iris causes partial contraction of 
 the dilator fibres (Bernstein and Dogiel). Stimulation near the centre of the cornea contracts the 
 pupil (E. If. Weber). In addition, we must assume that the iris itself contains elements that in- 
 fluence the diameter of the pupil (Sig. Mayer and Pribram). 
 
 Our knowledge of the action of poisons on the iris is still very obscure. Those substances 
 which dilate the pupil are called mydriatics, e. g., atropin, homatropin, duboisin (Tweedy, v. 
 Hasner), daturin, and hyoscyamin. They act chiefly by paralyzing the oculomotorius. But, in 
 addition, there must be also an effect upon the dilating fibres, for after complete paralysis (section) 
 of the oculomotorius, the moderate dilatation of the pupil thereby produced (\ 345, 5) is still further 
 increased by atropin. Minimal doses of atropin contract the pupil, owing to stimulation of the 
 pupillo- constrictor fibres ; enormous doses cause moderate dilatation of the pupil in consequence of 
 paralysis of the dilating as well as of the constricting nerve fibres. Atropin acts after destruction 
 of the ciliary [ophthalmic] ganglion (Hensen and Vblciers) [and division of all the nerves except 
 the optic], and in the excised eye (De Ruyter, Rottmann), [so that atropin is a local mydriatic. 
 In moderate doses it paralyzes the nervous termina- 
 tions of the third nerve (but not in birds whose 
 iris contains striped muscle), and in larger doses 
 it also paralyzes the muscular fibres], [Cocaine, 
 or cucaine, is obtained from the leaves of Ery- 
 throxylon coca. When applied locally it acts as a 
 powerful local anaesthetic, and hence it is very 
 useful for operations about the muco-cutaneous ori- 
 fices. A 4 per cent, solution dropped into the eye 
 produces complete insensibility of the cornea in 
 a few minutes. It causes dilatation of the pupils, 
 though they react to light and to the movements 
 of accommodation. It also causes temporary pa- 
 ralysis of accommodation, a sensation of heaviness 
 and coldness of the eyeball, enlargement of the 
 palpebral fissure, constriction of the small peripheral 
 vessels, and slight lachrymation.] 
 
 Myotics are those substances which contract 
 the pupil : Physostigmin (= Eserin, the alka- 
 loid of Calabar bean), nicotin, pilocarpin, muscarin, 
 morphia, according to some observers (Grunhagen), 
 cause stimulation of the oculomotorius, while others 
 (Hirschmann, Rosenthal) say they paralyze the 
 sympathetic. As these substances cause spasm of 
 the ciliary muscle, it is supposed that the first of these 
 has an analogous action on the sphincter. It is 
 probable that they paralyze the dilator fibres and 
 stimulate the oculomotor fibres. [Among local my- "^ *££ ^fJ^Z^^%, fc 
 otics, 1. e., those which act on the eye, some act on centre (spinal) ; E, iris ; G, optic nerve ; H, ocu- 
 
 the muscular fibres of the iris, e. g., physostigmin or lomotor (sphincter) roots ; I, sympathetic (dila- 
 
 eserin, while others acton the peripheral termina- '"U^a iSr5tdnn ^iiIU™! n i?C.S , SJ« or 
 
 '_.,., F. r . . roots; j±, ?eat 01 legion, causing pupillary im mo- 
 
 tions of the third nerve, e. g., pilocarpin, muscann. bility ; * probable seat of lesion, causing myosis. 
 
 Fig. 478. 
 
778 
 
 GORHAMS PUPIL PHOTOMETER. 
 
 Muscarin causes very great contraction of the pupil from spasm of the circular fibres, due to its 
 action on the third nerve ; eserin, on the other hand, although contracting the pupil, also affects 
 the dilator fibres. The contraction of the pupil due to opium is central in its cause.] 
 
 If the one pupil be contracted or dilated by these substances, the other pupil, conversely, is 
 dilated or contracted, owing to the change in the amount of light admitted into the eye into which 
 the poison has been introduced. The anaesthetics (ether, chloroform, alcohol, etc.), when they 
 begin to cause stupor, contract the pupil, and when their action is intense they dilate it (Dogiel). 
 Chloroform, during the stage when it causes excitement (preceding the narcosis), stimulates the 
 centre for the dilatation of the pupil ; after a time this centre is paralyzed, so that the pupil no 
 longer dilates on the application of external stimuli. Thereafter the pupillo- constrictor centre is 
 stimulated, whereby the pupil may be contracted to the size of a pin's head ; ultimately this centre 
 is paralyzed, and the pupil becomes dilated. 
 
 Time for Movements of Iris. — The reflex dilatation of the pupil occurs slightly later than the 
 reflex contraction, the time in the two cases being 0.5 and 0.3 second respectively after stimulation 
 by light {v. Vintschgau). A certain time always elapses, until the iris, corresponding to the strength 
 of the stimulus of light exciting the retina, " adapts " (Aubert) itself to produce a suitable size of 
 the pupil. Contraction of the pupil occurs very rapidly after stimulation of the oculomotorius in 
 birds ; in rabbits 0.89 second elapses after stimulation of the sympathetic, until the dilatation begins 
 (Arlt, Jim.). 
 
 Excised Eye. — "Light causes contraction of the pupil in the excised eye of amphibians and fishes 
 {Arnold, Budge). Even the iris of the eel, when cut out and placed in normal saline solution, 
 contracts to light {Arnold, Gysi, and Luchsinger), the green and blue rays being most active. 
 Increase of the temperature causes mydriasis in the excised eye of the frog or eel, while cooling 
 causes myosis (H. Miiller, Biernalk). 
 
 Fig. 479. 
 
 Fig. 480. 
 
 Gorham's pupil photometer Fig. 479 shows the disk with a slot and two holes. Fig. 480 gives a side view with the 
 diameter of the pupil marked on it. The upper end is closed by the disk, while the lower end is open. 
 
 [Size of the Pupil. — Jonathan Hutchinson recommends a pupilometer, consisting of a metal 
 plate perforated with a series of holes of different sizes. The smallest hole measures about % of a 
 line, and the largest is 4^ lines. The plate is placed just below the patient's eye, and the hole is 
 selected which corresponds with the size of the pupil.] 
 
 [Gorham's Pupil Photometer. — This ingenious instrument may be used as a pupilometer, 
 and also as a photometer. It consists of a piece of bronzed tubing (Figs. 479 and 480), 1.9 in. 
 long and 1.5 in. diameter. One end is closed by a disk or cap (Fig. 479), which is pierced in its 
 radii by a series of holes at distances varying from .05 in. to .28 in. There is a slot in the cap 
 which allows one pair of holes to be visible at a time, while on the cylinder is engraved the linear 
 distance of each pair of holes. In using the instrument as a pupilometer, look through the open 
 end of the tube (the bottom in Fig. 480), with both eyes open, toward a sheet of white paper or the 
 sky, when two disks of light will be seen. Then revolve the lid or cap slowly until the two white 
 disks just touch one another at their edges. The decimal fraction opposite the two apertures seen 
 on the scale outside indicates the diameter of the pupil in looths of an inch.] 
 
 [When using it as a photometer, it is assumed that the size of the pupil gives an index of the 
 intensity of the amount of light which influences the diameter of the pupil.] 
 
 Intraocular Pressure. — The movements of the iris are always accompanied by variations of the 
 intraocular pressure. The muscles of the iris affect the intraocular pressure, in that the dilatation 
 of the pupil increases it, while contraction of the pupil diminishes it. The increased or diminished 
 tension can be felt when two fingers are pressed on the eyeball. Stimulation of the sympathetic 
 increases while its section diminishes the pressure. Action of Drugs. — Atropin dropped into the 
 eye, after producing a short temporary diminution of the tension, increases it ; eserin, after a primary 
 increase, causes a diminution of the pressure {Graser and Holzhe). 
 
ENTOPTICAL PHENOMENA. 779 
 
 393. ENTOPTICAL PHENOMENA.— Entoptical phenomena de- 
 pend upon the perception of objects present within the eyeball itself. Among 
 them are — 
 
 1. Shadows are formed upon the retina by different opaque bodies. In order to see them in 
 one's own eye proceed thus : By means of a strong convex lens project a small image of a flame 
 upon a paper screen, prick a small opening through the image of the flame, and place one eye at 
 the other side of the screen, so that the illuminated puncture lies in the anterior focus of the eye, 
 i. e., about 13 mm. in front of the cornea. As the rays proceeding from this point pass parallel 
 through the media of the eye, a diffuse bright field of vision, surrounded by the black margins of 
 the iris, is obtained. All dark bodies which lie in the course of the rays of light throw a shadow 
 upon the retina, and appear as specks. There are various forms of these shadows (Fig. 481). 
 
 (a) The spectrum mucro-lacrimale, especially upon the margin of the eyelids, depending 
 upon particles of mucus, fat globules from the Meibomian glands, dust mixed with tears, causing 
 cloudy or drop-like retinal shadows, which are removed by winking. 
 
 (b) Folds in the Cornea. — If the cornea be pressed laterally with the finger, wrinkled shadows, 
 due to temporary wrinkles in the cornea, are produced. 
 
 (c) Lens' Shadows. — Bead-like or dark specks, bright and star-like figures, the former due to 
 deposits on and in the lens, the latter to the radiate structure of the lens. 
 
 (d) The muscse volitantes [Dechales, 1690Y like strings of beads, circles, groups of balls or 
 pale stripes, depend upon opaque particles (cells, disintegrating cells, granular fibres — Donders, 
 Duncan) in the vitreous humor. They move about when the eye is moved rapidly. Listing 
 ( 1845) showed that one may determine pretty accurately the position of these objects. While making 
 the observation upon one's own eyes, raise or depress the source of light; those shadows which are 
 caused by bodies on a level with the pupil retain their relative positions in the bright fields of vision. 
 
 Entoptical shadows. 
 
 Shadows, which appear to move in the same direction as the source of light, are caused by bodies 
 which lie in front of the plane of the pupil — those, however, which appear to move in the opposite 
 direction depend upon objects behind the plane of the pupil. 
 
 2. Purkinje's figure (1819) depends upon the blood vessels within the retina, which cast a 
 shadow upon the most external layer of the retina, viz., upon the rods and cones, these being the 
 parts acted upon by light. In ordinary vision we do not observe these shadows. According to v. 
 Helmholtz, this is due to the fact that the sensibility of the shaded parts of the retina is greater, and 
 their excitability is less exhausted, than all the other parts of the retina. As soon, however, as we 
 change the position of the shadow of the blood vessels, instead of being directly behind, so that the 
 blood vessels come to lie more laterally and behind them, i. e., upon places which do not receive 
 shadows from the blood vessels when the rays of light pass through the eye in the ordinary way, 
 then the figure of the blood vessels becomes apparent at once. All that is necessary is to cause the 
 light to enter the eyeball obliquely. Method. — (1) This may be done by passing an intense light 
 through the sclerotic, e.g., by throwing upon the sclerotic a small, bright, luminous image from a 
 source of light. On moving the source of light, the figure of the blood vessels moves in the same 
 direction. (2) Look directly upward to the sky, wink with the upper eyelid drooping, so that for 
 a moment, corresponding to the act of winking, rays of light enter obliquely the lowest part of the 
 pupils. (3) Look through a small aperture toward a bright sky, and move the aperture rapidly to 
 and fro, so that from both sides of the blood vessels shadows fall rapidly upon the nearest series of 
 rods and cones. (4) In a darkened room look straight ahead, and move a light to and fro close 
 under the eyes. Occasionally, while performing this experiment, one may see the macula lutea as 
 a non-vascular shaded depression {Purkinje, Burma), and, owing to the inversion of the objects, it 
 lies on the inner side of the entrance of the optic nerve. 
 
 3. Observing the Movements of the Blood Corpuscles in the Retinal Capillaries (Bois- 
 ser). — On looking, without accommodating the eye, toward a large bright surface, or through a dark 
 
780 ENTOPTICAL PHENOMENA. 
 
 blue glass toward the sun, we see bright spots, like points, forming longer or shorter chains, moving 
 in tortuous paths. The phenomenon is, perhaps, caused by the red blood corpuscles (in the capil- 
 laries posterior to the external granular layer— His) acting as small, light-collecting concave disks,' 
 concentrating the light falling upon them from bright surfaces, and throwing it upon the rods of the 
 retina. Each corpuscle must be in a special position; should it rotate, the phenomenon disappears. 
 Vierordt, who projected the movement upon a screen, calculated, from the velocity of their motion, 
 the velocity of the blood stream in the retinal capillaries as equal to 0.5 to 0.75 mm. in a second, 
 which corresponds very closely with the results obtained directly in other capillaries by E. H. 
 Weber and Volkmann (\ 90, 4). When the carotids are compressed, the movement is slower on 
 freeing them from the compression ; during short, forced expirations the movement is accelerated 
 (Landois). 
 
 4. The entoptical pulse (§ 79, 2 — Landois) depends upon the pulsating arteries irritating 
 mechanically the rods lying outside them. 
 
 5. Pressure Phosphenes. — Pressure applied to the eye causes a series of phenomena : (a) 
 Partial pressure upon the eyeball causes the so-called illuminated "pressure picture" or phosphene, 
 which was known to Aristotle. As the impression upon the retina is referred to something outside 
 the eye, the phosphene is always perceived on the side of the field of vision opposite to where the 
 pressure affects the retina, e.g., pressure upon the outer surface of the eyeball causes the flash of 
 light to appear on the inner side. If the retina is not well lighted the phosphene appears luminous ; 
 if the retina is well lighted it appears as a dark speck, within which the visual perception is momen- 
 tarily abolished, (b) If a uniform pressure be applied of the eyeball continuously from before 
 backward, as Purkinje pointed out, after some time very sparkling, variable figures appear in the 
 field of vision, which perform a wonderful fantastic play, and often resemble the sparkling effects 
 obtained in a kaleidoscope (v. Helmholtz), and are probably comparable to the feeling of formica- 
 tion produced by pressure upon sensory nerves (" sleeping of the limbs " ). (c ) By applying equable 
 and continued pressure, Steinbach and Purkinje observed a network with moving contents of a 
 bluish silvery color, which seemed to correspond to the retinal veins. Vierordt and Laiblin observed 
 the branching of the blood vessels of the choroid v& a red network upon a black ground, (d) Ac- 
 cording to Houdin, we may detect the position of the yellow spot by pressure upon the eyeball. 
 
 6. The entrance of the optic nerve may be detected on moving the eyes rapidly backward, 
 and especially inward, as a fiery ring or semicircle about the size of a pea. Probably, owing to the 
 movement of the retina, the entrance of the optic nerve is stimulated mechanically by the rapid 
 bending. Purkinje and others observed that the ring remained persistent on turning the eye 
 strongly inward. If the retina be brightly illuminated, the ring appears dark, and when the field 
 of vision is colored the ring has a different tint. If Purkinje's figure be produced at the same time, 
 one may observe that the vascular trunk proceeds from this ring — a proof that the ring corresponds 
 to the entrance of the optic nerve (Landois). 
 
 7. Accommodation Spot. — On accommodating the eye strongly toward a white surface, there 
 appears in the middle a small, bright, trembling shimmer, and in its centre a coarse, brown speck,, 
 about the size of a pea, is seen (Purkinje, v. Helmholtz). If pressure be applied externally to the 
 eyeball this speck becomes more distinct. After having once observed the phenomenon, occasion- 
 ally on pressing laterally upon the opened eye we may see it as a bright speck in the field of vision 
 — another proof that the intraocular pressure is increased during accommodation (Landois). 
 
 8. Mechanical Optical Stimulation. — On dividing the optic nerve in man, as in extirpation of 
 the eyeball, a flash of light is observed at the moment of section by the person operated on. The 
 section of the nerve fibres themselves is painless, but section of the sheaths is painful. 
 
 9. The accommodation phosphene (Purkinje, Czermak) is the occurrence of a fiery ring at 
 the periphery of the field of vision, seen on suddenly bringing the eyes to rest after accommodating 
 for a long time in the dark. The sudden tension of the zonule of Zinn resulting from the relaxa- 
 tion causes a mechanical stretching of the outermost part of the margin of the retina, or it may be 
 of a part of the retina behind this (Hensen and Volckers, Berlin). Purkinje observed the phe- 
 nomenon after suddenly relaxing the pressure on the eye. 
 
 10. Electrical Phenomena. — Electrical currents, when applied to the eye, cause a strong flash 
 of light over the whole field of vision. One pole of the battery may be placed on the upper eyelid 
 and the other on the neck. The flash at closing [ma'cing] the current is strongest with an ascend- 
 ing current, that with opening [breaking] the current with a descending current (v. Helmholtz). 
 If a uniform continuous ascending current be transmitted through the closed eyes, the dark disk of 
 the elevation at the entrance of the optic nerve appears in a whitish violet field of vision ; with a 
 descending current, the field of vision is reddish and dark, in which the position of the optic nerve 
 appears light blue (v. Helmholtz). If external colors are looked at simultaneously, these colors 
 blend to form a violet or yellow with the colors looked at (Schelske). During the passage of the 
 ascending current we see external objects indistinctly and smaller when the eyes are open ; while 
 with the descending current they are more distinct and larger (Sitter). Sometimes the position of 
 the macula lutea appears dark on a bright ground, or the reverse, according to the direction of the 
 current. If the current be opened [broken] the phenomena are reversed ({S 335), and the eye soon 
 returns to rest (v. Helmholtz). 
 
 11. The yellow spot appears sometimes as a dark circle when there is a uniform blue ilium ina- 
 
ILLUMINATION OF THE EYE. 
 
 rsi 
 
 tion. In a strong light the position of the yellow spot is surrounded by a bright area, twice or 
 thrice as large, called "Lowe's ring," 
 
 [Clerk-Maxwell's Experiment. — On looking through a solution of chrome-alum in a bottle or 
 vessel with parallel glass sides, we observe an oval, purplish spot in the green color of the alum. 
 This is due to the pigment of the yellow spot.] 
 
 Haidinger's Brushes. — On directing the eye toward a source of polarized light, " Haidinger's 
 polarized brushes " appear at the point of fixation. They are seen on looking through a Nicol's 
 prism at a bright cloud (v. Helmholtz). They are bright and bluish on a surface, bounded by two 
 neighboring hyperbola on a white field ; the dark bundle separating them is smallest in the centre 
 and yellow. Of the various colors of homogeneous light, blue alone shows the brushes (Stokes). 
 According to v. Helmholtz the seat of the phenomenon is the yellow spot, and is due to the yellow 
 colored elements of the yellow spot being slightly doubly refractive, while at one part they absorb 
 more, at another less, of the rays entering the eye. 
 
 12. Lastly, there are the visual sensations depending on internal causes, e.g., increased bound- 
 ing of the blood through the retina, as during violent coughing, increased intraocular pressure. 
 Stimulation of the psycho-gptic centres (§ 378, IV) may produce spectra, which Cardanus (1550), 
 Goethe, Nicolai and Johannes Miiller could produce voluntarily. 
 
 394. ILLUMINATION OF THE EYE— OPHTHALMOSCOPE. 
 
 — The light which enters the eye is partly absorbed by the black uveal pigment, 
 
 Fig. 482. 
 
 x 
 
 1 
 
 Arrangement for examining the eye of B. A, eye of observer ; x, source of light; S, S, plate of glass directed ob- 
 liquely, reflecting light into B. 
 
 and partly again reflected from the eye, and always in the same direction in which 
 the rays entered the eye. By placing one's self in front of the eye of another 
 person, of course the head, being an opaque body, cuts off a large number of 
 rays. Owing to the position of the head, no rays of light can enter the eye ; and 
 of course none can be reflected back to the eye of the observer. Hence, the eye 
 of the person being examined always appears black, because those rays which 
 alone could be reflected in the direction of the eye of the observer are cut off. 
 As soon, however, as we succeed in causing rays of light to enter the eye at the 
 same time and in the same direction in which we observe the eye of another 
 person, the fundus of the eye appears brightly illuminated. 
 
 The following simple arrangement (Fig. 482)'is sufficient for the purpose : Let B be the eye of 
 the patient, A that of the observer, and let a flame be placed at x. The rays of light proceeding 
 from x impinge upon the obliquely placed plate of glass (S, S), and are reflected in the direction of 
 the dotted lines into the eye (B). The fundus of the eye appears in this position to be brightly 
 illuminated in diffusion circles around 0. As the observer ( A) can see through the obliquely plated 
 glass plate (S, S), and in the same direction as the reflected rays (x, y) he sees the retina around b 
 brightly illuminated. 
 
782 
 
 ILLUMINATION OF THE EYE. 
 
 In order that this method l>e made available for practical purposes, we must, of course, be able to 
 distinguish the details, such as the blood vessels of the fundus of the eye, the macula lutea, the 
 entrance of the optic nerve, abnormalities of the retina and the choroidal pigment, etc. The follow- 
 ing considerations show us how to proceed in order to accomplish this. As already mentioned, and 
 
 Fig. 483. 
 
 as Fig. 465 shows, a small inverted image is formed on the retina [c, d ) when we look at an object 
 (A, B); conversely, according to the same dioptric law, an enlarged inverted real image of a small 
 distinct area of the retina (c, d — depending on the distance for which the eye was accommodated), 
 must be formed outside the eye (A, B). 
 
 Fig. 484. 
 
 If the fundus of this eye be sufficiently illuminated, this aerial image will be correspondingly bright. 
 
 In order to see the individual parts of the retinal picture more distinctly, the observer must 
 accommodate his own eye for the position of this image. In such circumstances the eye of the 
 observer would be too near to the observed eye. 
 
 Fig. 485. 
 
 
 His eye when so accommodated is removed from the eye of the patient by his own visual 
 distance, and by the visual distance of the patient. As this distance is considerable, the individual 
 small details of the fundus cannot be seen distinctly. Further, owing to the contraction of the pupil 
 of the patient, only a small area of the fundus can be seen, and this only under a small visual 
 
THE OPHTHALMOSCOPE. 
 
 783 
 
 angle, quite apart from the fact that it is often impossible to accommodate for the real image of the 
 fundus of the patient. 
 
 Hence, the eye of the observer must be brought nearer to the eye of the patient. This may be 
 done in two ways : (i) Either by placing in front of the eye of the patient a strong convex lens (of 
 I to 3 inches focus — Fig. 483, C). This causes the retinal image to be nearer to the eye (at B), 
 owing to the strong lens refracting the rays of light. The observer (M) can come nearer to the eye, 
 and can still accommodate for the image of the fundus of the eye. (2) Or a concave lens is placed 
 immediately in front of the eye of the patient (Fig. 484, 0). The rays of light emerging from the 
 eye of the patient (P) are either made parallel by the concave lens (0), and are brought to a focus 
 on the retina of the emmetropic observer (A) ; or, if the lens causes the rays to diverge (Fig. 485), 
 an erect, virtual image is formed at a distance behind the eye of the patient (at R). In these cases, 
 also, the observer can go much nearer to the eye of the patient. 
 
 The ophthalmoscope invented by v. Helmholtz enables us to examine the 
 whole of the fundus of the eye. 
 
 [Direct Method. — Use a concave mirror of 20 centimetres focal distance, with a central open- 
 ing. Reflect a beam of light into the patient's eye, where they cross in the vitreous and illuminate 
 the fundus of the eye. These rays again pass out of the eye and reach the observer's eye through 
 
 Fig. 487. 
 
 The entrance of the optib nerve, with the adjacent parts ot Morton's ophthalmoscope, 
 
 the fundus of the normal eye. a, ring of connective 
 tissue ; b, choroidal ring ; c, arteries ; d, veins ; g, divi- 
 sion of the central artery ; k, division of the central vein ; 
 L, lamina cribrosa ; t, temporal (outer) side ; «, nasal 
 (inner) side. 
 
 the central hole in the mirror. If the observer be emmetropic, they come to a focus on his 
 retina. In this way all the parts of the retina are seen in their normal position, but enlarged. 
 Hence, it is sometimes called the examination of the upright image. The eye of the patient and 
 observer must be at rest, i. e., be negatively accommodated, while the mirror must be brought as 
 near as possible to the eye of the patient.] 
 
 [Indirect Method, by which a more general view of the fundus is obtained. Throw the light 
 into the patient's eye by an ophthalmoscopic mirror, as above, but held at a distance of about 50 
 cm. (10 inches) from the patient's eye. Hold a biconvex lens of 14 dioptrics focal length vertically 
 between the mirror and the patient's eye (Fig. 483), the observer looking through the hole of the 
 mirror. What he does see is an inverted aerial image at B. Only a small part of the fundus 
 oculi can be seen at one time.] 
 
 [The ophthalmoscope, besides being used for examining the interior of the eyeball, is of the 
 utmost use in determining the existence and amount of anomalies of refraction in the refractive 
 media. For this purpose an ophthalmoscope requires to be provided with plus and minus lenses, 
 which, can be readily brought before the eye of the observer. This is readily done by an ingenious 
 mechanism devised by Couper, and which is made use of in the handy students' ophthalmoscope 
 of Morton (Fig. 487). The lenses are moved by a driving-wheel on the left figure, while at the 
 same time is indicated at a certain aperture the lens presented at the sight hole. The instrument is 
 
784 
 
 THE ORTHOSCOPE. 
 
 also provided with a movable arrangement carrying a concave mirror at either end. One of these 
 mirrors is 10 inches in focus, and is used for indirect examination and retinoscopy, while the other 
 is of 3 inches focus for direct examination, and is fixed at an angle of 25 .] 
 
 [Retinoscopy. — The ophthalmoscope is used also for this purpose. A beam of light is reflected 
 into the eye by the ophthalmoscopic mirror, and the play of light and shade on the fundus oculi 
 observed. A study of this is important in determining anomalies of refraction. For the method, 
 the student is referred to a text book on " Diseases of the Eye."] 
 
 [Artificial Eye. — The student may practice the use of the ophthalmoscope on an artificial eye 
 such as that of Frost (Fig. 488) or Perrin.] 
 
 Illumination. — In order to illuminate the interior of the eye, v. Helmholtz used several plates 
 of glass, placed behind each other, in the position of S, S, in Fig. 482. Afterward he used aplane 
 or concave mirror of 7 inches focus (Fig. 483, Sj, S 2 ), with a hole in the centre. Fig. 486 shows 
 the appearance of the fundus of the eye, as seen with the ophthalmoscope. In albinos the fundus 
 of the eye appears red , because -light passes into the eye through the sclerotic and uvea, which are 
 devoid of pigment. If a diaphragm be placed over the eye, so that the pupil alone is free, the eye 
 appears black {Bonders). 
 
 Fig. 488. 
 
 Fig. 489. 
 
 Frost's artificial eye. 
 
 Action of the orthoscope. 
 
 Tapetum. — In many animals the eyes have a bright green lustre. These eyes have a special 
 layer, the tapetum or the membrana versicolor of Fielding ; in carnivora it consists of cells, in her- 
 bivora of fibres, placed between the capillaries of the choroid and the stroma of the uvea. These 
 structures exhibit interference colors and reflect much light, so that the colored lustre appears in the 
 eye. 
 
 Oblique illumination is used with advantage for investigating the anterior chamber. A bright 
 beam of light,' condensed by a convex lens, is thrown laterally upon the cornea into the eye, and so 
 directed upon the point to be investigated as to illuminate it. A point so illuminated, e.g., a part 
 of the iris, may be examined from a distance by means of a lens, or even by a microscope [Lieb- 
 reich). 
 
 The Orthoscope. — Czermak constructed this instrument (Fig. 489), in which the eye is placed 
 under water. Take a small glass trough with one of its walls removed. Press the margins of the 
 open side firmly against the region of the eye. The eye and its surroundings form, as it were, the 
 sixth side of the trough, which is filled with water, so that the cornea is bathed therewith. As 
 the refractive index of water is almost the same as the refractive index of the media of the eye, the 
 rays of light pass into the eye in a straight direction without being refracted. Hence, objects in the 
 
EXPERIMENTS ON THE RETINA. 785 
 
 anterior chamber can be seen directly, as if they were not within the eye at all. Another advantage 
 is that the objects can be brought nearer to the eye of the observer. The rays of light emerging 
 from the point (a) of the fundus, if the eye were surrounded by air, would leave the eye as the 
 parallel lines, b, c, b, c. Under water, these rays, a, b, continue in the direction a, b, as far as b, d, 
 where they emerge from the water, and are bent from the perpendicular to d, e, d, e. The eye of 
 the observer, looking in the direction e, d, sees the point, a, nearer, viz., in the direction e, d, a', 
 lying at a. 
 
 395. ACTIVITY OF THE RETINA IN VISION.— I. Blind Spot. 
 — The rods and cones alone are the parts of the retina sensitive to light 
 {Henr. Muller), they alone are excited by the vibrations of the ether. This is 
 confirmed by Marriotte's experiment (1688), which proves that the entrance of 
 the optic nerve, where rods and cones are absent, is devoid of visual sensibility. 
 Hence, it is spoken of as the " blind spot." 
 
 [Marriotte's Experiment. — Make two marks, about three inches apart, upon 
 paper (Fig. 490). Look at the cross with the right eye, keeping the left eye 
 closed, and hold the paper about a foot from the eye, when both the cross and 
 the circle will be seen. Gradually approximate the paper to the eye, keeping the 
 open eye steadily fixed on the cross ; at a certain moment the circle will dis- 
 appear, and on bringing the paper nearer to the eye it will reappear. The moment 
 when the circle disappears is when its image falls upon the entrance of the optic 
 nerve.] 
 
 Position and Size. — The entrance of the optic nerve lies about 3.5 mm. internal to the visual 
 axis of the eyeball, in the retina. Its diameter is 1.8 mm. {Helmkoltz). The apparent diameter of 
 the blind spot in the field of vision is in a horizontal direction 6° 56' — this lies 12° 35' to 18° 55' 
 
 Fig. 490. 
 
 -4- 
 
 horizontally from the fixed point. Eleven full moons placed side by side would disappear on the 
 surface, and so would a human face at a distance of over 2 metres. 
 
 Proofs. — The following facts prove that the entrance of the optic nerve is insensible to light : 
 
 (1) Donders projected, by means of a mirror, a small image of a flame upon the entrance of the 
 optic nerve of another person, and the person had no sensation of light. But a sensation of light 
 was experienced when the image of the flame was projected upon the neighboring parts of the retina. 
 
 (2) On combining with Marriotte's experiment, the experiment which causes entoptical phenomena 
 at the entrance of the optic nerve {\ 393, 6 and 7), this coincides with the blind spot {Landois). 
 
 Form of Blind Spot. — In order to determine the form and apparent she of the blind spot in 
 one's own eye, fix the head at about 25 centimetres from a surface of white paper; select a small 
 point on the latter and keep the eye directed toward it, then starting from the position of the blind 
 spot move a white feather in all directions over the paper ; whenever the tip of the feather becomes 
 visible, make a mark at this spot. Thus the blind spot may be mapped out. It is found to have 
 an irregular elliptical form from which processes proceed, due to the equally non-sensitive origins of 
 the large blood vessels of the retina [Hueck, Helmkoltz), (Marriotte concluded from his experiment 
 that the choroid, which is perforated by the optic nerve, is the membrane sensitive to light, as the 
 nerves are nowhere absent from the retina.) 
 
 The blind spot causes no appreciable gap in the field of vision. — As this area is not 
 excited by light, a black spot cannot appear in the field of vision, for the sensation of black implies 
 the presence of retinal elements, which, however, are absent from the blind spot. 
 The circumstance, however, that in spite of the existence of an inexcitable spot , 
 
 during vision, no part of the field of vision appears to be unoccupied, is due to a ft |J C 
 psychical action. The unoccupied area of the field of vision, corresponding to 
 the blind spot, is filled in according to probability by a psychical process (£. H. _ . „ 
 
 Weber). Hence, when a white point disappears from a black surface, the whole Q \Q) J 
 surface appears to us black ; a white surface, from which a black point falls 
 on the blind spot, appears quite white; a page of print, gray throughout; etc. , , 
 
 According to the probabilities, certain parts are supplied — parts of a circle, the ff fl 1 
 SO 
 
786 
 
 IMAGES FALLING ON THE RODS AND CONES. 
 
 middle parts of a long line, the central part of a cross. Such images, however, which cannot 
 be constructed according to the probabilities, are not perfected, e.g., the end of a line or a human 
 face. In other cases the condition known as " contraction " of the field of vision tends to fill 
 up the gap. This will be evident on looking at the nine preceding letters, so that e disappears ; 
 we no longer see the three letters on each side of it in straight lines, but b,f, h, d, are turned in 
 toward e. The adjoining parts of the field of vision seem to extend over and around the blind 
 spot, and thus help to compensate for the blind spot. 
 
 II. Optic Fibres Inexcitable to Light. — The layer of the fibres of the 
 optic nerve in the retina is not sensitive to light. This is proved by the fact that in 
 
 Fig. 491. 
 
 Horizontal section of the right eye. a, cornea ; b, conjunctiva; c, sclerotic; d, anterior chamber containing the 
 aqueous humor ; e, iris ; fj ', pupil : g, posterior chamber ; /, Petit's canal ; /, ciliary muscle ; k, comeo-scleral 
 limit; i, canal of Schlemm ; m, choroid ; n, retina; o, vitreous humor ; No, optic nerve ; q, nerve sheaths ; p, 
 nerve fibres ; Ic, lamina cribrosa. The line O A indicates the optic axis ; Sr, the axis of vision ; r, the position 
 of the fovea centralis. 
 
 the fovea centralis, which is the area of most acute vision, there are no nerve 
 fibres. Further, Purkinje's figure proves that, as the arteries of the retina lie 
 behind the optic fibres, the latter cannot be concerned in the perception of the 
 former. 
 
 III. Rods and Cones. — The outer segments of the rods and cones have 
 rounded outlines, and are packed close together, but natural spaces must exist 
 between them, corresponding to the spaces that must exist between groups of 
 
THE FOVEA CENTRALIS. 
 
 787 
 
 bodies with a circular outline. These parts are insensible to light, so that a retinal 
 image is composed like a mosaic of round stones. The diameter of a cone in the 
 yellow spot is 2 to 2.5 t>. (M. Schultze). If two images of two small points, placed 
 very near each other, fall upon the retina, they will still be distinguished as distinct 
 images, provided that both images fall upon two different cones. The two images 
 on the retina need only be 3-4-5.4 p. apart, in order that each may be seen sepa- 
 rately, for then the images still fall upon two adjoining cones. If the distance be 
 diminished so very much that both images fall upon one cone, or one upon one 
 cone and the other upon the intermediate [cement] substance, then only one 
 image is perceived. The images must be further apart in the peripheral portion 
 of the retina in order that they may be separately distinguished. 
 
 As the rounded end surfaces of the cones do not lie exactly under each other, but are so arranged 
 that one series of circles is adapted to the interstices of the following series, this explains why fine 
 
 ' Fig. 492. 
 
 M' Hardy's perimeter, i, porcelain button : M, bit; E, for fixing tbe head ; g, h, quadrant ; o, fixation point ; p, 
 pointer for piercing the record chart held in the frame (e) which moves on c ; D, upright supporting the quad- 
 rant and the automatic arrangement of slides (£ and /), which are moved by /. 
 
 dark lines lying near each other appear to have alternating twists upon them, as the images of these 
 must fall upon the cones, at one time to the right, at another to the left. 
 
 IV. The fovea centralis is the region of most acute vision, where only 
 cones are present, and where they are very numerous and closely packed (Fig. 
 455). The cones are less numerous in the peripheral areas of the retina, and. 
 consequently vision is much less acute in these regions. We may, therefore, con- 
 clude that the cones are more important for vision than the rods. When we wish 
 to see an object distinctly, we involuntarily turn our eyes so that the retinal image 
 falls upon the fovea centralis. In doing this, we are said to "fix" our eyes upon 
 an object. The line drawn from the fovea to the object is called the axis of 
 vision (Fig. 491, .S>). It forms an angle of only 3.5-7° with the " optical axis" 
 
788 
 
 PERIMETRY. 
 
 ( A), which unites the centres of the spherical surfaces of the refractive media 
 of the eye. The point of intersection, of course, lies in the nodal point (Kn~) of 
 the lens (p. 786). The term "direct vision" is applied to vision when the 
 direction of the axis of vision is in line with the object [t. e., when the image of 
 the object falls' directly on the fovea centralis]. 
 
 " Indirect vision " occurs when the rays of light from an object fall upon 
 the peripheral parts of the retina. Indirect vision is much less acute than the 
 direct. 
 
 To test the acuity of direct vision, draw two fine parallel lines close to each other, and 
 gradually remove them more and more from the eye, until both appear almost to unite and form one 
 line. The size of the retinal image may be ascertained by determining the distance of the two lines 
 from each other, and the distance of the lines from the eye; or, from the corresponding visual angle, 
 which is generally between 60 to 90 seconds. 
 
 Perimetry. — In order to test indirect vision we may use the perimeter of Aubert and Forster. 
 The eye is placed opposite a fixed point, from which a semicircle proceeds, so that the eye lies in 
 the centre of it. As the semicircle rotates round the fixed point, on rotating the former we can 
 circumscribe the surface of a hemisphere, in the centre of which the eye is placed. Proceeding 
 from the fixed point, objects are placed upon semicircles, and are gradually pushed more and more 
 toward the periphery of the field of vision, until the object becomes indistinct, and finally disappears. 
 The process of testing is continued by placing the arc successively in the different meridians of the 
 field of vision. 
 
 [M'Hardy's perimeter is a very convenient form (Fig. 492). It consists of two uprights (C 
 and D), which are fixed to the opposite ends of a flat basal plate (A). C carries an arrangement for 
 supporting the patient's head, while D carries the automatic arrangement for the perimetiic record. 
 Both of these can be raised or depressed by the screws (G and b). The patient's chin rests on the 
 chin-rest (E), while in the mouth is placed Landolt's biting fixation (L), which is detachable. The 
 position of the head can be altered by sliding F on L, which can be fixed in any position by the 
 screw (O). The porcelain button (I) just below the patient's eye (/) is connected with the adjust- 
 ment of the " fixation point." The automatic recording apparatus consists of a revolving quadrant 
 (A, h), which describes a hemisphere round a horizontal axis passing through the centre of the hol- 
 low male axle, turning in the female end of a, which is supported by D. The quadrant can be fixed 
 at any point by g. On the front concave surface of the quadrant is fixed a circular white piece of 
 ivory, which represents the " fixation point," from which a needle projects, and which is the zero of 
 the instrument. A carriage (i), in which the test objects are placed, can be moved in the concave 
 face of the quadrant by means of the milled head (/), which moves the carriage by means of a tooth 
 
 and pinion wheel.] 
 
 [When the milled head (_/) is turned, it moves 
 the carriage and two slides (k and /), the two 
 slides moving in the ratio of 2 to I. The rate of 
 the carriage is so adjusted that it travels ten times 
 faster than /, and five times faster than k. The 
 pointer (p) is connected with these slides, so that 
 it moves when they move, and records its move- 
 ments by piercing the record chart, which is fixed 
 in the double-faced frame (e). The frame for the 
 record chart is hinged near c to the upright (D). 
 The frame when upright comes so near the pointer 
 that the latter can pierce a chart placed in the 
 frame. The patient is directed to look at the 
 " fixation point," which is merely a small ivory 
 button placed in the imaginary axis of the hemi- 
 sphere on the front of the centre of the concave 
 surface of the quadrant; the projecting needle 
 point (o) indicates its position. This is the zero 
 of the quadrant, and on each side of it the quad- 
 rant is divided into 90 .] 
 
 [In testing the field of vision, place the carriage 
 so as to cover zero, adjust the eye for the fixation 
 point, and look steadily at it, and if all is right 
 the pointer (pj ought to pierce the centre of the 
 chart. Move the carriage along the quadrant by 
 / until it disappears from the field of vision, and 
 when it does so the pointer is made to pierce the 
 chart. Make another observation in another di- 
 Priestley Smith's perimeter. rection by altering the position of the quadrant, 
 
 Fig. 493. 
 
PERIMETRIC CHARTS. 
 
 789 
 
 and go on doing so until a complete record is obtained of the field of vision. Test the other eye 
 in the same way. The color field may be tested by using colored papers in the carriage.] 
 
 [Priestley Smith's perimeter (Fig. 493) is simpler. The wooden knob on the left of the 
 figure is placed under the eye of the patient, who stares at the fixed point in the axis of the quad- 
 rant, which can be moved in any meridian. The test object is a square piece of white paper which 
 is moved along the quadrant. The chart is placed on the posterior surface of the hand wheel and 
 moves with it, so that the meridians of the chart move with the quadrant. There is a scale behind 
 the hand wheel corresponding with the circles on the chart, so that the observer can prick off his 
 observations directly.] 
 
 [Scotoma is the term applied to dimness or blindness in certain parts of the field of vision, 
 which may be central, marginal, or in patches.] 
 
 The capacity for distinguishing colors diminishes more rapidly at the periphery of the retina 
 than that for distinguishing differences in the brightness or intensity of light. In fact, the periphery 
 of the retina is slightly red blind. The diminution is greater in the vertical meridian of the eye 
 than in the horizontal, and it diminishes with the distance from the fixation point (Aubert and 
 
 Perimetric chart of a healthy and a diseased eye. 
 
 Forster). These observers also state that, during accommodation for a distant object, the diminu- 
 tion of the capacity to distinguish brightness and color toward the periphery of the lens, occur 
 more rapidly than with near vision. The excitability of the retina for colors and brightness is 
 greater at a point equally distant from the fovea centralis on the temporal than on the nasal side of 
 the eye (Schon). 
 
 Perimetric Chart. — If the arc of the perimeter (Fig. 493) be divided into 90 degrees, beginning 
 at the fixation point (central point), and proceeding to L and M (Fig. 494) ; and if a series of con- 
 centric circles be inscribed on this, with the point of fixation as their centre, we can construct a 
 topographical chart of the visual capacity of the normal or healthy eye from the data obtained by 
 the examination of the retina. 
 
 Fig. 494 is an example; the thick lines indicate a diseased eye, the corresponding thin lines a 
 healthy eye. The continuous line indicates the limits for the perception of white; the interrupted 
 line that for blue; the punctuated and interrupted line that for red; m is the blind spot (flirsch- 
 berg). In the normal eye the limits for the perception of 
 
790 PERCEPTION OF COLORS. 
 
 Externally . 
 Internally . 
 Upward . . 
 Downward . 
 
 White. 
 
 70°-88° 
 50°-6o° 
 45°-55° 
 65°-7°° 
 
 Blue. 
 
 65° 
 60° 
 
 45° 
 6o° 
 
 Red. 
 
 60° 
 
 5o° 
 40° 
 
 Green. 
 
 40° 
 
 40° 
 
 3°°-35° 
 
 35° 
 
 V. Specific Energy. — The rods and cones alone are endowed with what 
 Johannes Miiller called "specific energy," i. e., they alone are set into activity by 
 the ethereal vibrations, to produce those impulses which result in vision. Mechan- 
 ical and electrical stimuli, however, when applied to any part of the course of 
 the nervous apparatus, produce visual phenomena. Mechanical stimuli are more 
 intense stimuli than light rays, as shown by performing the dark pressure figure 
 with the eyes open (jj 393, 5, a), whereby the circulation in the retina is inter- 
 fered with (Danders) ; in the region of pressure we cannot see external objects 
 which affect the retina uniformly and continuously. 
 
 VI. The duration of the retinal stimulation must be exceedingly short, as 
 the electrical spark lasts only 0.000000868 second ; still, as a general rule, a shorter 
 time is required the larger and brighter the object looked at. Alternate stimula- 
 tion with light, 17 to 18 times per minute, is perceived most intensely (Briicke). 
 Further, an increase or diminution of 0.01 part of the intensity of the light is 
 perceptible (§ 383). A shorter time is required to perceive yellow than is re- 
 quired for violet and red (Vierordi). The retina becomes more sensitive to light 
 after a person has been kept in the dark for a long time, and also after repose 
 during the night. If light be allowed to act on the eyes for a long time, and 
 especially if it be intense, it causes fatigue of the retina, which begins sooner in 
 the centre than in the periphery of the organ (Auberf). At first the fatigue comes 
 on rapidly and afterward develops more slowly ; it is most marked in the morning 
 (A. Pick, C. F. Miiller). The periphery of the retina is specially characterized 
 by its capacity for distinguishing movements (Exner). 
 
 VII. Visual Purple. — The mode of the action of light upon the end organs 
 of the retina has already been referred to in connection with the " visual purple" 
 [or Rhodopsin] (Boll, Kiihne~). Kiihne showed that, by illuminating the retina, 
 actual pictures (e. g., the image of a window) could be produced on the retina, 
 but they gradually disappeared. From this point of view we might regard the 
 retina as comparable, to a certain extent, to the sensitive plate of a photographic 
 apparatus. 
 
 Optogram. — The visual purple is formed by the pigment epithelium of the retina. Perhaps we 
 might compare the process to a kind of secretion. The visual purple may be restored in a retina 
 by laying the latter upon living choroidal epithelium. The pigment disappears from the mamma- 
 lian retina by the action of light 60 times more rapidly than from the retina of the frog. In a 
 rabbit's eye, whose pupil was dilated with atropin, Ewald and Kiihne obtained a sharp picture or 
 optogram of a bright object placed at a distance of 24 cm. from the eye; the image was "fixed" 
 by a 4 per cent, solution of alum. Visual purple withstands all the oxidizing reagents ; zinc chloride, 
 acetic acid and corrosive sublimate change it into a yellow substance ; it becomes white only through 
 the action of light; the dark heat rays are without effect, while it is decomposed above a tempera- 
 ture of 52° C. [As visual purple is absent from the cones, and cones only are present in the fovea 
 centralis, we cannot explain vision by optograms formed by the visual purple.] 
 
 VIII. Destruction of the rods and cones of the retina causes correspond- 
 ing dark spots in the field of vision. 
 
 396. PERCEPTION OF COLORS.- Physical.— The vibrations of the light ether are per- 
 ceived by the retina only within distinct limits. If a beam of white light, e.g., from the sun, be 
 transmitted through a prism, the light rays are refracted and dispersed, and a " prismatic spec- 
 trum " (Fig. 14) is obtained. White light contains rays of very different wave lengths or periods 
 of vibration. The dark heat rays, whose wave length is 0.00194 mm - (Fizeau), are refracted least. 
 They do not act upon the retina, and are therefore invisible. They act, however, upon sensory 
 nerves. About 90 per cent, of these rays is absorbed by the media of the eye (Briicke and Knob- 
 
CONTRAST AND COMPLEMENTARY COLORS. 791 
 
 lauih, Cima, Jansen). From Frauenhofer's line, A, onward, the oscillations of the light ether 
 exrite the retina in the following order : Red with 481 billions of vibrations per second, orange 
 with 532, yellow with 563, green with 607, blue with 653, indigo with 676, and violet with 764. bil- 
 lion vibrations per second. The sensation of color therefore depends on the number of vibra- 
 tions of the light ether, just as the pitch of a note depends on the number of vibrations of the 
 sounding body (Newton, 1704; Hartley, 1772). Beyond the' violet lie the chemically active 
 [actinic] rays of the spectrum. After cutting out all the spectrum, including the violet rays, v. 
 Helmholtz succeeded in seeing the ultra-violet rays, which had a feeble grayish-blue color. The 
 heat rays in the colored part of the spectrum are transmitted by the media of the eye in the same 
 way as through water (Franz), The existence of the ultra-violet rays is best ascertained by the 
 phenomenon of fluorescence. Von Helmholtz, on illuminating a solution of sulphate of quinine 
 with the ultra-violet rays, saw a bluish-white light proceeding from all parts of the solution which 
 were acted on by the ultra-violet rays. As the media of the eye themselves exhibit fluorescence 
 (v. Helmholtz, Setschenow), they must increase the power of the retina to distinguish these rays. 
 The ultra-violet rays are not largely absorbed by the media of the eye (Briicke, Donders). 
 
 In order that a color be perceived, it is essential that a certain quantity of light must fall upon the 
 retina. Blue, when at the lowest degree of brightness, gives a color sensation with a quantity of 
 light, which is sixteen times less than that required for red (Dobrowlosky). 
 
 Intensity of the Impression of Light. — While light of different periods of vibration applied 
 to the eye excites the different sensations of color, the amplitude of the vibrations (height of the 
 waves) determines the intensity of the impression of light; just as the loudness of a note depends 
 on the amplitude of the vibrations of the sounding body. The sun's light contains all the rays 
 which excite the sensation of color in us, and when all these rays fall simultaneously upon the retina 
 we experience the sensation of white. If the colors of the spectrum obtained by means of a prism 
 be reunited, white light is again obtained. If no vibrations of the light ether reach the retina, every 
 sensation of light and color is absent, but we can scarcely apply the term black to this condition. 
 It is rather the absence of sensation, such as, for example, is the case when a beam of light falls 
 on the skin of the back. This does not give the sensation of black, but rather that of no sensation 
 of light. 
 
 Simple and Mixed Colors. — We distinguish simple colors, e. g., those of 
 the spectrum. In order to perceive these, the retina must be excited (set into 
 vibration) by a distinct number of oscillations (see above). Further, we distin- 
 guish "mixed colors," whose sensation is produced when the retina is excited 
 by two or more simple colors, simultaneously or rapidly alternating. The most 
 complex mixed color is white, which is composed of a mixture of all the 
 simple colors of the spectrum. 
 
 The " complementary colors " are important. Any two colors which to- 
 gether give the sensation of white are complementary to each other. The " con- 
 trast colors " are mentioned here merely to complete the list. They are closely 
 related to the complementary colors. Any two colors which, when mixed, sup- 
 plement the generally prevailing tone of the light, are contrast colors. When the 
 sky is blue, the two contrast colors must be bluish white ; with bright gaslight 
 they must be yellowish white, and in pure white light, of course, all the comple- 
 mentary are the same as the contrast colors (Briicke). 
 
 Methods of Mixing Colors. — 1. Two solar spectra are projected upon a screen, and the spectra 
 are so arranged as to cause any one part of one spectrum to cover any part of the other. 2. Look 
 obliquely through a vertically arranged glass plate at a color placed behind it. Another color is 
 placed in front of the glass plate, so that its image is also reflected into the eye of the observer ; 
 thus, the light of one color transmitted through the glass plate and the reflected light from the other 
 color reach the eye simultaneously. [Lambert's Method. — This is easily done by Lambert's method. 
 Use colored wafers and a slip of glass ; place a red wafer on a sheet of white paper, and about three 
 inches behind it another blue one. Hold the plate of glass midway and vertically between them, 
 and so incline the glass that, while looking through it at the red wafer, a reflected image of the blue 
 one will be projected into the eye in the same direction as that of the red image, when we have the 
 sensation of purple.] 
 
 3. A rotatory disk, with sectors of various colors, is rapidly rotated in front of the eyes. On rapidly 
 rotating the colored disk, the impressions produced by the individual colors are united to produce a 
 mixed color. If the rotating disk, which yields, let us suppose, white, on mixing the colors of the 
 spectrum, be reflected in a rapidly rotating mirror, then the individual components of the white re- 
 appear (Landois). 
 
 4. Place in front of each of the small holes in the cardboard used for Scheiner's experiment 
 (Fig. 471), two differently colored pieces of glass; the colored rays of light passing through the 
 holes unite on the retina, and produce a mixed color (Czermak). 
 
792 
 
 GEOMETRICAL COLOR TABLE. 
 
 Complementary Colors. — Investigation shows that the following colors of the spectrum are 
 complementary, i. e., every pair gives rise to white : — 
 
 Red and greenish-blue, Orange and Cyan- blue, 
 
 Yellow and indigo-blue, Greenish-yellow and violet, 
 
 while green has the compound complementary color purple (v. Helmholtz). 
 
 The mixed colors may be determined from the following table. At the top of the vertical and 
 horizontal columns are placed the simple colors ; the mixed colors occur where they intersect the 
 corresponding vertical and horizontal columns ( Dk. = dark ; wh. = whitish) : — 
 
 
 Violet. 
 
 Indigo. 
 
 Cyan-blue. 
 
 Bluish-green. 
 
 Green. 
 
 Greenish-yellow. 
 
 Yellow. 
 
 Red 
 
 Orange 
 
 Yellow 
 
 Gr.-yellow 
 
 Green 
 
 Bluish-green 
 
 Cyan-blue 
 
 Purple 
 Dk.-rose 
 
 Wh.-rose 
 White " 
 White-blue 
 Water-blue 
 Indigo 
 
 Dk.-rose 
 
 Wh.-rose 
 
 White 
 
 Wh. -green 
 
 Water-blue 
 
 Water-blue 
 
 Wh.-rose 
 White 
 Wh. -green 
 Wh. -green 
 Bl. -green 
 
 White 
 Wh. -yellow 
 Wh. -yellow 
 Green 
 
 Wh. -yellow 
 
 Yellow 
 
 Gr.-yellow 
 
 Gold-yellow 
 Yellow 
 
 Orange. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 The following results have been obtained from observations on the mixture of 
 colors : — 
 
 i. If two simple, but non-complementary, spectral colors be mixed with each 
 other, they give rise to a color sensation, which may be represented by a color 
 lying in the spectrum between both, and mixed with a certain quantity of white, 
 Hence we may produce every impression of mixed colors by a color of the spec- 
 trum -f- white (Grassmati). 
 
 2. The less white the colors contain the more " saturated " they are said to 
 be ; the more white they contain they appear more unsaturated. The saturation 
 of a color diminishes with the intensity of the illumination. 
 
 Geometrical Color Table. — Since the time of Newton attempts have been made to construct 
 a so-called " geometrical color table," which will enable any mixed color to be readily found. Fig. 
 
 495 shows such a color table ; white is placed 
 
 Fig. 495. 
 
 Cyan blue 
 
 in the middle, and from it to every point in the 
 curve, — which is marked with the names of 
 the colors, — suppose each color to be so placed 
 that, proceeding from white, the colors are ar- 
 ranged, beginning with the brightest tone, then 
 always follows the most saturated tone, unlil 
 the pure saturated spectral color lies in the 
 point of the curve marked with the name of 
 the color. The mixed color purple is placed 
 between violet and red. In order to determine 
 from this table the mixed color of any two 
 spectral colors, unite the points of these colors 
 by a straight line. Suppose weights corre- 
 sponding to the units of intensity of these 
 colors be placed on both points of the curve 
 indicating colors, then the position of the 
 centre of gravity of both in the line connect- 
 ing the colors indicates the position of the 
 mixed color on the table. The mixed color 
 of two spectral colors always lies on the color 
 table in the straight line connecting the two 
 color points. Further, the impression of the 
 mixed color corresponds to an intermediate spectral color mixed with white. The complementary 
 color of any spectral color is found at once by making a line from the point of this color through 
 white, until it intersects the opposite margin of the color table ; the point of intersection indicates 
 the complementary color. If pure white be produced by mixing two complementary colors, the 
 color lying nearest white on the connecting line must be specially strong, as then only would the 
 centre of gravity of the lines uniting both colors lie in the point marked white. 
 
 By means of the color table we may ascertain the mixed color of three or more colors. For 
 example, it is required to find the mixed color resulting from the union of the point, a (pale yellow), 
 b (fairly saturated bluish-green), and c (fairly saturated blue). On the three points place weights 
 corresponding to their intensities, and ascertain the centre of gravity of the weight, a, b, c ; it will 
 
 Violet 
 
 Yellow 
 
 Orange 
 
 Red 
 
 Geometrical color cone or table. 
 
HERINGS THEORY OF COLOR SENSATION. 
 
 793 
 
 lie at p. It is obvious, however, that the impression of this mixed color, whitish green-blue, can 
 be produced by green-blue -f- white, so that p may be also the centre of gravity of two weights, 
 which lie in the line connecting white and green-blue. 
 
 We may describe a triangle, V, Gr, R, about the color table so as to enclose it completely. The 
 three fundamental or primary colors lie in the angles of this triangle, red, green, violet. It is 
 evident that each of the colored impressions, i. e„ any point of the color table, may be determined 
 by placing weights corresponding to the intensity of the primary colors at the angles of the triangle, 
 so that the point of the color table, or, what is the same thing, the desired mixed color, is the 
 centre of gravity of the triangle with its angles weighted as above. The intensity of the three 
 primary colors, in order to produce the mixed color, must be represented in the same proportion as 
 the weights. 
 
 Theories. — Various theories have been proposed to account for color sensation. 
 
 1. According to one theory, color sensation is produced by one kind of element present in the 
 retina, being excited in different ways by light of different colors (oscillations of the light ether of 
 different wave lengths, number of vibrations, and refractive indices). 
 
 2. Young-Helmholtz Theory. — The theory of Thomas Young (1807) and 
 v. Helmholtz (1852) assumes that three different kinds of nerve elements, 
 corresponding to the three primary colors, are present in the retina. Stimulation 
 of the first kind causes the sensation of red, of the second green, and of the 
 third violet. 
 
 The elements sensitive to red are most strongly excited by light with the longest wave length, the 
 red rays ; those for green by medium wave lengths, green rays ; those for violet by the rays of 
 shortest wave length, violet rays. Further, it is assumed, in order to explain a number of phe- 
 nomena, that every color of the spectrum excites all the kinds of fibres, some of them feebly, others 
 strongly. Suppose in Fig. 496 the colors of the spectrum are arranged in their natural order from 
 red to violet horizontal y, then the three curves raised upon the abscissa might indicate the strength 
 
 Fig. 496. 
 
 
 ^l 
 
 ^'""'"^ 
 
 
 ,*^ 
 
 x ,-' 
 
 "-\. 
 
 
 \ 
 \ 
 
 \ 
 V 
 
 1 
 
 \ 
 
 3 
 
 / • [ 
 
 r 
 
 1 
 
 1 
 
 
 / 
 
 of the stimulation of the three kinds of retinal elements. The continuous curve corresponds to the 
 rays producing the sensation of red, the dotted line that of green, and the broken line that of violet. 
 Pure red light, as indicated by the height of the ordinates in R, strongly excites the elements sensi- 
 tive to red, and feebly the other two kinds of terminations, resulting in the sensation of red. Simple 
 yellow excites moderately the elements for red and green, and feebly those for violet = sensation 
 of yellow. Simple green excites strongly the elements for green, but much more feebly the two 
 other kinds = sensation of green. Simple blue excites to a moderate extent the elements for green 
 and violet ; more feebly those for red = sensation of blue. Simple violet excites strongly the cor- 
 responding elements, feebly the others = sensation of violet. Stimulation of any two elements ex- 
 cites the impression of a mixed color ; while, if all of them be excited in a nearly equal degree, 
 the sensation of white is produced. As a matter of fact, the Young-Helmholtz theory gives a clear 
 and simple explanation of the phenomena of the physiological doctrine of color. It has been at- 
 tempted to make the results obtained by examination of the structure of the retina to accord with 
 this view. According to Max Schultze, the cones alone are end organs connected with the percep- 
 tion of color. The presence of longitudinal striation in their outer segments is regarded as consti- 
 tuting them multiple terminal end organs. Our power of color sensation, so far as it depends on 
 the retina, would, on this view of the matter, bear a relation to the number of cones. The degree 
 of color sensation is most developed in the macula lutea, which contains only cones, and diminishes 
 as the distance from the point increases, while it is absent in the peripheral parts of the retina. 
 
 The rods of the retina are said to be concerned only with the capacity to distinguish between 
 quantitative sensations of light. 
 
 3. Hering's Theory. — Ew. Hering, in order to explain the sensation of light, proceeds from 
 the axiom stated under I, p. 792. What we are conscious of, and call a visual sensation, is the 
 psychical expression for the metabolism in the visual substance (" Sehsubstanz "), i.e., in those 
 n;rve masses which are excited in the process of vision. Like every other corporeal matter, this 
 substance during the activity of the metabolic process undergoes decomposition or " disassimila- 
 tion ;" while during rest it must be again renewed, or " assimilate " new material. Hering 
 assumes that for the perception of white (bright) and black (dark), two different qualities of the 
 
794 COLOR BLINDNESS. 
 
 chemical processes take place in the visual substance, so that the sensation of white or bright cor- 
 responds to the disassimilation (decomposition), and that of black (dark) to the assimilation 
 (restitution) of the visual substance. According to this view, the different degrees of distinctness 
 or intensity with which these two sensations appear, occur in the several transitions between pure 
 white and deep black, or the proportions in which' they appear to be mixed (gray), correspond to 
 the intensity of these two psycho-physical processes. Thus the consumption and restitution of 
 matter in the visual substance are the primary processes in the sensation of white and black. In 
 the production of the sensation of white, the consumption of the visual substance is caused by the 
 vibrating ethereal waves acting as the discharging force or stimulus, while the degree of the sensa- 
 tion of whiteness (brightness) is proportional to the quantity of the matter consumed. The process 
 of restitution discharges the sensation of black ; the more rapidly it occurs the stronger is the sen- 
 sation of black. The consumption of the visual substance at one place causes a greater restitution 
 in the adjoining parts. Both processes influence each other simultaneously and conjointly. This 
 explains physiologically the phenomenon of contrast (p. 799), of which the old view could give 
 only a psychical interpretation. Similarly, color sensation is regarded as a sensation of decom- 
 position (disassimilation) and one of the restitution (assimilation) ; in addition to white, red and 
 yellow are the expression of decomposition ; while green and blue represent the sensation of resti- 
 tution. Thus the visual substance is subject to three different ways of chemical change or meta- 
 bolism. We may thus explain the colored phenomena of contrast and the complementary after 
 images. The sensation of black-white may occur simultaneously with all colors, so that every 
 color sensation is accompanied by that of dark or bright, so that we cannot have an absolutely pure 
 color. There are three different constituents of the visual substance; that connected with the sen- 
 sation of black- white (colorless), that with blue-yellow, and that with red-green.. All the rays of 
 the visible spectrum act in disassimilating the black-white substance, but the different rays act in 
 different degrees. The blue- yellow or red-green substances, on the other hand, are disassimilated only 
 by certain rays, some rays causing assimilation, and others are inactive. Mixed light appears colorless 
 when it causes an equally strong disassimilation and assimilation in the blue-yeilow and in the red- 
 green substance, so that the two processes mutually antagonize each other, and the action on the 
 black- white substance appears pure. Two objective kinds of light, which together yield white, are 
 not to be regarded as complementary, but as antagonistic kinds of light, as they do not supplement 
 each other to produce white, but only allow this to appear pure, because, being antagonistic, they 
 mutually prevent each other's action. 
 
 The imperfection of the Young-Helmholtz theory of color sensation is that it recognizes only one 
 kind of excitability, excitement and fatigue (corresponding to Hering's disassimilation), and that it 
 ignores the antagonistic relation of certain light rays to the eye. It does not regard white as con- 
 sisting of complementary light rays, which neutralize each other by their action on the colored 
 visual substance, but as uniting to form white {Hering}. 
 
 In applying this theory to color blindness (§ 397), we must assume that 
 those who are red blind want the red-green visual substance ; there are but two 
 partial spectra in their solar spectrum, the black-white and the yellow-blue. The 
 position of green appears to such an one to be colorless ; the rays of the red part 
 of the spectrum are so far visible, as the sensation of yellow and white produced 
 by these rays is strong enough to excite the retina. Hering divides his spectrum 
 into a yellow and a blue half. A violet-blind person wants the yellow-blue 
 visual substance ; in his spectrum there are only two partial spectra, the black- 
 white and the red-green. In cases of complete color blindness, the yellow- 
 blue and red-green substances are absent. Hence, such a person has only the 
 sensation of bright and dark. The sensibility to light and the length of the 
 spectrum are retained ; the brightest part in this case, as in the normal eye, is in 
 the yellow {Hering). 
 
 Von Kries devised the following experiment against Hering's theory : Arrange two gray surfaces, 
 one formed by mixing white and black, the other by yellow and blue, and let both appear equally 
 an intense gray. On staring at a red object on these surfaces until the retina is fatigued, and until 
 the object disappears, a gray after image appears in both cases. The mixture of yellow and blue 
 cannot in this case have acted as to cause restitution of the red-gray substance ; this is done rather 
 by the mixed gray composed of white and black. 
 
 397. COLOR BLINDNESS AND ITS PRACTICAL IMPORT- 
 ANCE. — Causes. — By the term color blindness (Dyschromatopsy) is 
 meant a pathological condition in which some individuals are unable to distin- 
 guish certain colors. Huddart (1777) was acquainted with the condition, but it 
 was first accurately described by Dalton (1794), who himself was red blind. 
 The term color blindness was given to it by Brewster. 
 
COLOR BLINDNESS. 795 
 
 The supporters of the Young- Helmholtz theory assume that, corresponding to the paralysis of the 
 three color-perceiving elements of the retina, there are the following kinds of color blindness : — 
 
 I. Red blindness. 2. Green blindness. 3. Violet blindness. 
 The highest degree being termed complete color blindness. 
 
 The supporters of E. Hering's theory of color sensation distinguish the following kinds : — 
 
 1. Complete Color Blindness (Achromatopsy). — The spectrum appears achromatic; the 
 position of the greenish-yellow is the brightest, while it is darker on both sides of it. A colored 
 picture appears like a photograph or an engraving. Occasionally the different degrees of light 
 intensity are perceived in one shade of color, e.g., yellow, which cannot be compared with any other 
 color. 0. Becker and v. Hippel observed cases of unilateral congenital complete color blindness, 
 while the other eye was normal for color perception. 
 
 2. Blue-yellow Blindness [Stilling). — The spectrum is dichromatic, and consists only of red 
 and green. The blue violet end of the spectrum is usually greatly shortened. In pure cases only 
 the red and green are correctly distinguished (Mauthner's Erythrochloropy), but not the other 
 colors. Unilateral cases have been observed. 
 
 3. Red-green Blindness. — The spectrum is also dichromatic. Yellow and blue are correctly 
 distinguished; violet and blue are both taken for blue. The sensations for red and green are absent 
 altogether. There are several forms of this — (a) Green blindness, or the red-green blindness, 
 with undiminished spectrum (Mauthner's Xanthokyanopy), in which bright green and dark red 
 are confounded. In the spectrum yellow abuts directly on blue, or between the two; at most, there 
 is a strip of gray. The maximum of brightness is in the yellow. It is often unilateral and often 
 hereditary, (b) Red blindness (or the red-green blindness with undiminished spectrum, also 
 called Daltonism), in which bright red and dark green are confounded. The spectrum consists 
 of yellow and blue, but the yellow lies in the orange. The red end of the spectrum is uncolored, 
 or even dark. The greatest brightness, as well as the limit between yellow and blue, lies more 
 toward the right. 
 
 4. Incomplete color blindness, or a diminished color sense, indicates the condition in which 
 the acuteness of color perception is diminished, so that the colors can be detected only in large 
 objects, or only when they are near, and when they are mixed with white they no longer appear as 
 such. A certain degree of this form is frequent, in as far as many persons are unable to distinguish 
 greenish-blue from .bluish-green. 
 
 Acquired color blindness occurs in diseases of the retina and atrophy of the optic nerve 
 (Benedict), in commencing tabes, in some forms of cerebral disease, (p. 731), and intoxications. 
 At first green blindness occurs, which is soon followed by red blindness. The peripheral zone of 
 the retina suffers sooner than the central area (Schirmer). In hysterical persons there may be 
 intermittent attacks of color blindness (Charcot, Landolt); and the same occurs in hypnotized 
 persons (p. 708). 
 
 H. Cohn found that, on heating the eyeball of some color-blind persons, the color blindness 
 disappeared temporarily. Occasionally in persons without a lens red vision is present, and is due 
 to unknown causes Percentage. — Holmgren found that 2.7 per cent, of persons were color blind, 
 most being red and green blind, and very few violet blind. 
 
 Limits of Normal Color Blindness. — The investigations on the power of color perception in 
 the normal retina are best earned out by means of Aubert-Forster's perimeter, or that of M'Hardy, 
 \ 395- It is found that our color perception is complete only in the middle of the field of vision. 
 Around this is a middle zone, in which only blue and yellow are perceived, in which, therefore, 
 there is red blindness. Outside this zone there is a peripheral girdle, where there is complete color 
 blindness (§ 395). Hence a red-blind person is distinguished from a person with normal vision, in 
 that the central area of the normal field of vision is absent in the former, this being rather included 
 in the middle zone. The field of vision of a green blind person differs from that of a person with 
 normal vision, in that his peripheral zone corresponds to the intermediate and peripheral zones of 
 the normal eye. The violet-blind person is distinguished by the complete absence of the normal 
 peripheral zone. The incomplete color blindness of these two kinds is characterized by a uniformly 
 diminished central field. [When very intense colors are used, such as those of the solar spectrum, 
 the retina can distinguish them quite up to its margin (Landolt).'] 
 
 In poisoning with santonin, violet blindness (yellow vision) occurs in consequence of the 
 paralysis of the violet perceptive retinal elements, which not unfrequently is preceded by stimulation 
 of these elements, resulting in violet vision, i. e., objects seem to be colored violet (Hiifner). Such 
 is the explanation of this phenomenon given by Holmgren. Max Schultze, however, referred the 
 yellow vision, i. e., seeing objects yellow, to an increase of the yellow pigment in the macula lutea. 
 
 When colored objects are very small, and illuminated only for a short time, the normal eye first 
 fails to perceive red (Aubert, Lamansky) ; hence it appears that a stronger stimulus is required to 
 excite the sensation of red. Briicke found that very rapidly intermittent white light is perceived 
 as green, because the short duration of the stimulation failed to excite the elements of the retina 
 connected with the sensation of red. 
 
 [The practical importance of color blindness was pointed out by George Wilson, and again 
 more recently by Holmgren.] No person should be employed in the marine or railway service 
 until he has been properly certified to be able to distinguish red from green. 
 
796 AFTER IMAGES. 
 
 Methods of Testing Color Blindness. — Following Seebeck, Holmgren used small skeins 
 of colored wools as the simplest material, in red, orange, yellow, greenish-yellow, green, greenish- 
 blue, blue, violet, purple, rose, brown, gray. There are five finely graduated shades of each of the 
 above colors. When testing a person, select only one skein — e.g., a bright red or rose — from the 
 mass of colored wools placed in front of him, and place it aside, asking him to seek out those skeins 
 which he supposes are nearest to it in color. 
 
 Mace and Nacati have measured the acuteness of vision by illuminating a small object with 
 different parts of the spectrum. They compared the observations on red and green-blind persons 
 with their own results, and found that a red-blind person perceives green light much brighter than 
 a normal person. The green blind had an excessive sensibility for red and violet. It appears that 
 what the color blind lose in perceptive power for one color they gain for another. 
 
 398. STIMULATION OF THE RETINA.— Positive and Nega- 
 tive After Images — Irradiation — Contrast. — As with every other nervous 
 apparatus, a certain but small amount of time elapses after the rays of light fall 
 upon the eye before the action of the light takes place, whether the light acts so 
 as to produce a conscious impression, or produces merely a reflex effect upon the 
 pupil. The strength of the impression produced depends partly and chiefly upon 
 the excitability of the retina and the other nervous structures. If the light acts 
 for a long time with equal intensity, the excitation, after having reached its 
 culminating point, rapidly diminishes again, at first more rapidly, and afterward 
 more and more slowly. 
 
 [When the retina is stimulated by light there is-(i) an effect on the rho- 
 dopsin (p. 756). (2) The electro-motive force is diminished (§ 332). (3) The 
 processes of the hexagonal pigment cells of the retina dipping between the rods 
 and cones are affected ; thus they are retracted in darkness, and protruded in the 
 light (Fig. 497). (4) Engelmann has shown that the length and shape of the 
 cones vary with the action of light. The cones are retracted in darkness and 
 protruded under the influence of light (Fig. 497). This alteration in the shape 
 of the cones takes place even if the light acts on the skin, and not on the eyeball 
 at all.] 
 
 After Images. — If the light acts on the eye for some time so as to excite the 
 retina, and if it be suddenly withheld, the retina still remains for some time in an 
 excited condition, which is more intense and lasts longer the stronger and the 
 longer the light was applied and the more excitable the condition of the retina. 
 Thus, after every visual perception, especially if it is very distinct and bright, there 
 remains a so-called " after image.''' We distinguish a " positive after image," 
 which is an image of similar brightness and a similar color. 
 
 " That the impression of any picture remains for some time upon the eye is a physiological phe- 
 nomenon ; when such an impression can be seen for a long time it becomes pathological. The 
 weaker the eye is the longer the image remains upon it. The retina does not recover itself so 
 quickly, and we may regard the action as a kind of paralysis. This is not to be wondered at in 
 the case of dazzling pictures. After looking at the sun, the image may remain on the retina for 
 several days. A similar result sometimes occurs with pictures which are not dazzling. Busch records 
 that the impression of an engraving, with all its details, remained on his eye for 17 minutes." 
 (Goethe.) 
 
 Experiments and Apparatus for Positive After Images. — 1. When a burning stick is 
 rapidly rotated it appears as a fiery circle. 
 
 2. The thaumatrope of Paris. 
 
 3. The phanakistoscope (Plateau) or the stroboscopic disks (Stampfer). Upon a disk or a 
 cylinder a series of objects are so depicted that successive drawings represent individual factors of 
 one continuous movement. On looking through an opening at such a disk rotated rapidly, we see 
 pictures of the different phases moving so quickly that the one rapidly follows the one in front of 
 it. As the impression of the one picture remains until the. following one takes its place, it has the 
 appearance as if the successive phases of the movement are continuous, and are one and the same 
 figure. The apparatus under the name of zoetrope, which is extensively used as a toy, is generally 
 stated to have been invented in 1832. It was described by Cardanus in 1550. It may be used to 
 represent certain movements, c. g., of the spermatozoa and ciliary motion (Purkinje and Valentin), 
 the movements of the heart and those of locomotion. 
 
 [Illusions of Motion. — Silvanus P. Thompson points out that if a series of concentric circles 
 in black and white be made on paper, and the sheet on which the circles are drawn be moved with 
 
NEGATIVE AFTER IMAGES IRRADIATION. 
 
 797 
 
 a motion as if one were rinsing out a pail, but with a very minute radius, then all the circles appear 
 to rotate with the same angular velocity as that imparted. Professor Thompson has contrived other 
 forms of this illusion, in the form of Strobic disks.] 
 
 4. The color top contains on the sectors of its disk the colors which are to be mixed. As the 
 color of each sector leaves a condition of excitation for the whole duration of a revolution, all the 
 colors must be perceived simultaneously, i. e., as a mixed color. 
 
 Negative After Images. — Occasionally, when the stimulation of the retina 
 is strong and very intense, a ' ' negative, ' ' instead of a positive, after image appears. 
 In a negative after image, the bright parts of the object appear dark, and the 
 colored parts in their corresponding contrast colors (p. 791). 
 
 Examples of Negative After Images. — After looking for a long time at a dazzlingly- illumi- 
 nated white window, on closing the eyes we have the impression of a bright cross, or crosses, as the 
 case may be, with dark panes. 
 
 Negative colored after images are beautifully shown by Norrenberg's apparatus. Look steadily 
 at a colored surface, e. g., a yellow board with a small blue square attached to the centre of its 
 surface. A white screen is allowed to fall suddenly in front of the board ; the white surface now 
 has a bluish appearance, with a yellow square in its centre. 
 
 The usual explanation of dark negative after images is, that the retinal elements are fatigued 
 by the light, so that for some time they become less excitable, and, consequently, light is but feebly 
 perceived in the corresponding areas of the retina ; hence darkness prevails. 
 
 Fig. 497. 
 
 Fig. 498. 
 
 Forshowing irradiation. 
 
 The cones of the retina and pigment cells (ot the 
 frog) as affected by light and darkness: x. After 
 two days in darkness ; 2. After ten minutes in 
 daylight. 
 
 Hering explains the dark after images as due to a process of assimilation in the black- white visual 
 substance. In explaining colored after images, the Young-Helmholtz theory assumes that, under 
 the action of the light waves, c. g., red, the retinal elements connected with the perception of this 
 color are paralyzed. On now looking suddenly on a white surface, the mixture of all the colors 
 appears as white minus red, i.e., the white appears green. In bright daylight the contrast color lies 
 very near the complementary color. According to Hering, the contrast after image is explained by the 
 assimilation of the corresponding colored visual substance, in this case, of the "red-green" (J 397). 
 
 Not unfrequently, after intense stimulation of the retina, positive and negative 
 after images alternate with each other until they gradually fuse. After looking at 
 the dark-red setting sun we see alternate disks of red and green. 
 
 The phenomena of contrast undergo some modification in the peripheral areas 
 of the retina, owing to the partial color blindness which occurs in these areas 
 (Adamuck and Woinow). 
 
 Irradiation is the term applied to certain phenomena where we form a false 
 estimate of visual impressions, owing to inexact accommodation. If from inexact 
 accommodation the margins of the object are projected upon the retina in diffu- 
 sion circles, the mind tends to add the undefined margin to those parts of the 
 visual image which are most prominent in the image itself. What is bright appears 
 
798 EXAMPLES OF CONTRAST. 
 
 larger (Fig. 498) and overcomes what is dark, while an object, without reference 
 to brightness or color, has the same relation to its background. When the accom- 
 modation is quite accurate the phenomenon of irradiation is not present. 
 
 " A dark object appears smaller than a bright one of the same size. On looking at the same time 
 from a certain distance at two circles of the same size, a white one on a black background, and a 
 black on a white background, we estimate the latter to be about one -fifth less than the former (Fig. 
 498). On making the black circle one-fifth ' larger, they will appear equal. Tycho de Brahe re- 
 marks that the moon, when in conjunction (dark), appears to be one-fifth smaller than in opposition 
 (full, bright). The first lunar crescent appears to belong to a larger disk than the dark one adjoin- 
 ing it, which can occasionally be distinguished at the time of the new light. Black clothes make 
 persons appear to be much smaller than light clothes. A light seen behind a margin gives the 
 appearance of a cut in the margin. A ruler, behind which is placed a lighted candle, appears to the 
 observer to have a notch in it. The sun, when rising and setting, appears to make a depression in 
 the horizon" {Goethe). 
 
 Simultaneous Contrast. — By this term is meant a phenomenon like the fol- 
 lowing : When bright and dark parts are present in a picture at the same time, 
 •the bright (white) parts always appear to be more intensely bright the less white 
 there is near them, or, what is the same thing, the darker the surroundings, and, 
 conversely, they appear less bright the more white tints that are present near them. 
 A similar phenomenon occurs with colored pictures. A color in a picture appears 
 to us to be more intense the less of this color there is in the adjoining parts, that 
 is, the more the surroundings resemble the tints of the contrast color. Simulta- 
 neous contrast arises from simultaneous impressions occurring in two adjoining and 
 different parts of the retina. 
 
 Examples of Contrast for Bright and Dark. — 1. Look at a white network on a black 
 ground ; the parts where the white lines intersect appear darker, because there is least black near 
 them. 
 
 2. Look at a point of a small strip of dark gray paper in front of a dark black background. Push 
 a large piece of white paper between the strip and the background ; the strip on the white ground 
 now appears to be much darker than before. On again removing the white paper, the strip at once 
 again appears bright (Hering). 
 
 3. Look with both eyes toward a grayish-white surface, e.g., the ceiling of a room. After gazing 
 for some, place in front of the eye a paper tube eight inches long, and an inch to an inch and a quar- 
 ter in diameter, blackened in the inside. The part of the ceiling seen through the tube appears as a 
 round white spot {Landois). 
 
 Examples for Colors.— 1. Place a piece of gray paper on a red, yellow, or blue ground; the 
 contrast colors appear at once, viz., green, blue, or yellow. The phenomenon is made still more 
 distinct by covering the whole with transparent tracing paper (Herm. Meyer). Under similar cir- 
 cumstances, printed matter on a colored ground appears in its complementary color ( W. v. Bezold). 
 
 2. An air bubble in the strongly tinged field of vision of a thick microscopical preparation appears 
 with an intense contrast color (Landois). 
 
 3. Paste four green sectors upon a rotatory white disk, leave a ring round the centre of the disk 
 uncovered by green, and cover it with a black strip. On rotating such a disk the black part appears 
 red and not gray (BrUcke). 
 
 4. Look with both eyes toward a grayish-white surface, and place in front of one eye a tube about 
 the length and breadth of a finger, composed of transparent oiled paper, gummed together to such 
 thickness as will permit light to pass through its walls. The part of the surface seen through the 
 tube appears in its contrast color. The experiment also shows the contrast in the intensity of the 
 illumination (Landois). A white piece of paper, with a round black spot in its centre, when looked 
 at through a blue glass, appears blue with a black spot. If a white spot of the same size on a black 
 ground be placed in front, so that it is reflected in the glass plate and just covers the black spot, it 
 shows the contrast color yellow (Ragona Scina). 
 
 5. The colored shadows also belong to the group of simultaneous contrasts. " Two conditions 
 are necessary for the production of colored shadows — firstly, that the light gives some kind of a color 
 to the white surface ; second, that the shadow is illuminated, to a certain extent, by another light. 
 During the twilight, place a short lighted candle on a white surface, between it and the fading day- 
 light hold a pencil vertically, so that the shadow thrown by the candle is illuminated, but not abol- 
 ished, by the feeble daylight ; the shadow appears of a beautiful blue. The blue shadow is easily 
 seen, but it requires a little attention to observe that the white paper acts like a reddish-yellow sur- 
 face, whereby the blue color apparent to the eye is improved. One of the most beautiful cases of 
 colored shadows is seen in connection with the full moon. The light of the candle and that of the 
 moon can be completely equalized. Both shadows can be obtained of equal strength and distinct- 
 ness, so that both colors are completely balanced. Place the plate opposite the light of the moon, 
 
MOVEMENTS OF THE EYEBALLS. 799 
 
 the lighted candle a little to one side at a suitable distance. In front of the plate hold an opaque 
 body, when a double shadow appears, the one thrown by the moon and lighted by the candle being 
 bright reddish-yellow ; and, conversely, the one thrown by the candle and lighted by the moon ap- 
 pears of a beautiful blue. Where the two shadows come together and unite is black ( Goethe). 
 
 6. " Take a plate of green grass of considerable thickness and hold it so as to get the bars of a 
 window reflected in it, the bars will be seen double ; the image formed by the under surface of the 
 glass being green, while the image coming from the under surface of the glass, and which ought 
 really to be colorless, appears to be purple. The experiment may be performed with a vessel filled 
 with water, with a mirror at its base. With pure water colorless images are obtained, while by col- 
 oring the water colored images are produced " {Goethe). 
 
 Explanation of Contrast. — Some of these phenomena may be explained as due to an error of 
 judgment. Luring the simultaneous action of several impressions, the judgment errs, so that when 
 an effect occurs at one place, this acts to the slightest extent in the neighboring parts. When, there- 
 fore, brightness acts upon a part of the retina, the judgment ascribes the smallest possible action of 
 the brightness to the adjoining parts of the retina. It is the same with colors. It is far more prob- 
 able that the phenomena are to be referred to actual physiological processes (Hering). Partial stim- 
 ulation with light affects not only the part so acted on, but also the surrounding area of the retina ; 
 the part directly excited undergoing increased disassimilation, the (indirectly stimulated) adjoining 
 area undergoing increased assimilation ; the increase of the latter is greatest in the immediate 
 neighborhood of the illuminated portion, and rapidly diminishes as the distance from it increases. 
 By the increase of the assimilation in those parts not acted on by the image of the object, this is 
 prevented, so that the diffused light is perceived. The increase of the assimilation in the immediate 
 neighborhood of the illuminated spot is greatest, so that the perception of this relatively stronger 
 different light is largely rendered impossible (Hering). 
 
 Successive Contrast. — Look for a long time at a dark or bright object, or at a colored (e.g., 
 red) one, and then allow the effect of the contrast to occur on the retina, i.e., with reference to the 
 above, bright and dark, or the contrast color green, then these become very intense. This phe- 
 nomenon has also been called " successive contrast." In this case the negative after image obviously 
 plays a part. 
 
 [Some drugs cause subjective visual sensations, but these do so by acting on the brain, e.g., 
 alcohol, as in delirium tremens, cannabis indica, sodic salicylate and large doses of digitalis 
 (Brunton).~\ 
 
 399. MOVEMENTS OF THE EYEBALLS— EYE MUSCLES.— 
 
 The globular eyeball is capable of extensive and free movement on the corre- 
 spondingly excavated fatty pad of the orbit, just like the head of a long bone in 
 the corresponding socket of a freely movable arthroidal joint. The movements 
 of the eyeball, however, are limited by certain conditions, by the mode in which 
 the eye muscles are attached to it. Thus, when one muscle contracts, its antag- 
 onistic muscle acts like a bridle, and so limits the movement ; the movements are 
 also limited by the insertion of the optic nerve. The soft elastic pad of the orbit 
 on which the eyeball rests is itself subject to be moved forward or backward, so 
 that the eyeball also must participate in these movements. 
 
 Protrusion of the eyeball takes place — 1. By congestion of the blood vessels, especially of the 
 veins in the orbit, such as occurs when the outflow of the venous blood from the head is interfered 
 with, as in cases of hanging. *. By contraction of the smooth muscular fibres in Tenon's cap- 
 sule, in the spheno-maxillary fissure, and in the eyelids {\ 404), which are innervated by the cer- 
 vical sympathetic nerve. 3. By voluntary forced opening of the palpebral fissure, whereby the 
 pressure of the eyelids acting on the eyeball is diminished. 4. By the action of the oblique 
 muscles, which act by pulling the eyeball inward and forward. If the superior oblique be con- 
 tracted when the eyelids are forcibly opened, the eyeball may be protruded about I mm. When 
 protrusion of the eyeball occurs pathologically (as in 1 and 2), the condition is called exoph- 
 thalmos. 
 
 Retraction of the eyeball is the opposite condition, and is caused — 1. By closing the eyelids 
 forcibly. 2. By an empty condition of the retrobulbar blood vessels, diminished succulence, or dis- 
 appearance of the tissue of the orbit. 3. Section of the cervical sympathetic in dogs causes the 
 eyeball to sink somewhat in the orbit. The smooth muscular fibres of Tenon's capsule are perhaps 
 antagonistic in their action to the four recti when acting together, and thus prevent the eyeball from 
 being drawn too far backward. Many animals have a special retractor bulbi muscle, e.g. amphi- 
 bians, reptiles and many mammals ; the ruminants have four. 
 
 The movements of the eyes are almost always accompanied by similar move- 
 ments of the head, chiefly on looking upward, less so on looking laterally, and 
 least of all when looking downward. 
 
800 POSITIONS OF THE EYEBALL. 
 
 The difficult investigations on the movements of the eyeballs have been carried out, especially by 
 Listing, Meissner, Helmholtz, Donders, A. Fick and E. Hering. 
 
 Axis. — All the movements of the eyeball take place round its point of rotation (Fig. 499, 0), 
 which lies 1.77 mm. behind the centre of the visual axis, or 10.957 mm ' fr° m tne vertex of the 
 cornea (Bonders). In order to determine more carefully the movements of the eyeball, it is neces- 
 sary to have certain definite data: 1. The visual axis (S, S / ), or the antero-posterior axis of the 
 eyeball, unites the point of rotation with the fovea centralis, and is continued straight forward to 
 the vertex of the cornea. 2. The transverse, or horizontal axis (Q, Q,), is the straight line con- 
 necting the points of rotation of both eyes and its extension outward. Of course, it is at right 
 angles to 1. 3. The vertical axis passes vertically through the point of rotation at right angles to 
 1 and 2. These three axes form a coordinate system. We must imagine that in the orbit there is 
 a fixed determinate axial system, whose point of intersection corresponds with the point of rotation 
 of the eyeball. When the eye is at rest (primary position), the three axes of the eyeball completely 
 coincide with the three axes of the coordinate system in the orbit. When the eyeball, however, is 
 moved, two or more axes are displaced from this, so that they must form angles with the fixed 
 orbital system. 
 
 Planes. — In order to be more exact, and also partly for further estimations, let us suppose three 
 planes passing through the eyeball, and that their position is secured by any two axes. 1. The 
 horizontal plane divides the eyeball into an upper and lower half; it is determined by the visual 
 transverse axes. In its course through the retina it forms the horizontal line of separation of the 
 latter ; the coats of the eyeball itself cut it in their horizontal meridian. 2. The vertical plane 
 divides the eyeball into an inner and outer half; it is determined by the visual and vertical axes. 
 It cuts the retina in the vertical line of separation of the latter and the periphery of the bulb in the 
 vertical meridian of the eyeball. 3. The equatorial plane divides the eyeball into an anterior and 
 posterior half ; its position is determined by the vertical and transverse axes, and it cuts the 
 sclerotic in the equator of the eyeball. The horizontal and vertical lines of separation of the 
 retina, which intersect in the fovea centralis, divide the retina into four quadrants. 
 
 In order to define more precisely the movements of the eyeball, v. Helmholtz has introduced the 
 following terms : He calls the straight line which connects the point of rotation of the eye with the 
 fixed point in the outer world the visual line ("Blicklinie"), while a plane passing through these 
 lines in both eyes he called the visual plane ; the ground line of this plane is the line uniting the 
 two points of rotation, viz., the transverse axis of the eyeball. Suppose a sagittal section to be made 
 through the head, so as to divide the latter into a right and left half, then this plane would halve the 
 ground line of the visual plane, and when prolonged forward would intersect the visual plane in 
 the median line. The visual point of the eye can be (1) raised or lowered — the field which it 
 traverses being called the visual field (" Blickfeld ") ; it is part of a spherical surface with the point 
 of rotation of the eye in its centre. Proceeding from the primary position of both eyes, which is 
 characterized by both visual lines being parallel with each other and horizontal, then the elevation 
 of the visual plane can be determined by the angle which this forms with the plane of the primary 
 position. This angle is called the angle of elevation — it is positive when the visual plane is raised 
 (to the forehead), and negative when it is lowered (chinwards). (2) From the primary position, 
 the visual line can be turned laterally in the visual plane. The extent of this lateral deviation is 
 measured by the angle of lateral rotation, i.e., by the angle which the visual line forms with the 
 median line of the visual plane ; it is said to be positive when the posterior part of the visual line 
 is turned to the right, negative when to the left. The following are the positions of the eyeball : — 
 
 i. Primary position, in which both the lines of vision are parallel with each 
 other, and the visual planes are horizontal. The three axes of the eyeball coin- 
 cide with the three fixed axes of the coordinate system in the orbit. 
 
 2. Secondary positions are due to movements of the eye from the primary 
 position. There are two different varieties : (a) where the visual lines are par- 
 allel, but are directed upward or downward. The transverse axis of both eyes 
 remains the same as in the primary position ; the deviations of the other two axes 
 expressed by the amount of the angle of elevation of the line of vision. (J>) 
 The second variety of the secondary position is produced by the convergence or 
 divergence of the lines of vision. In this variety the vertical axes, round which 
 the lateral rotation takes place, remain as in the primary position ; the other axes 
 form angles ; the amount of the deviation is expressed by the " angle of lateral 
 rotation." The eye, when in the primary position, can be rotated from this posi- 
 tion 42 outward, 45 inward, 34° upward and 57° downward (Schuurmanri). 
 
 3. Tertiary position is the position brought about by the movements of the 
 eye, in which the lines of vision are convergent, and are at the same time inclined 
 upward or downward. 
 
 All the three axes of the eye are no longer coincident with the axes in the pri- 
 
OCULAR MUSCLES. 801 
 
 mary position. The exact direction of the visual lines is determined by the 
 amount of the angle of lateral rotation and the angle of elevation. There is still 
 another important point. The eyeball is always rotated at the same time round 
 the line of vision and round its axis ( Volkmann, Hering, Donders). As the iris 
 rotates round the visual line like a wheel round its axis, this ' rotation is called 
 " circular rotation " (" Raddrekung") of the eye, which is always connected with 
 the tertiary positions. Even oblique movements may be regarded as composed 
 of — (i) a rotation round the vertical axis, and (2) round the transverse axis ; or 
 it may be referred to rotation round a single constant axis placed between the 
 above-named axes, passing through the point of rotation of the eyeball, and at 
 right angles to the secondary and primary direction of the visual axis (line of 
 vision) — {Listing). The amount of circular rotation is measured by the angle 
 which the horizontal separation line of the retina forms with the horizontal sepa- 
 ration line of the retina of the eye in the primary position. This angle is said to 
 be positive, when the eye itself rotates in the same direction as the hand of a 
 watch observed by the same eye, i.e., when the upper end of the vertical line of 
 separation of the retina is turned to the right. 
 
 According to Donders, the angle of rotation increases with the angle of elevation and the angle 
 of lateral rotation — it may exceed 10°. With equally great elevation or depression of the visual 
 plane, the rotation is greater the greater the elevation or depression of the line of vision. 
 
 On looking upward in the tertiary position, the upper ends of the vertical lines of separation of 
 the retina diverge ; on looking downward they converge. If the visual plane be raised, the eye, 
 when it deviates laterally to the right, makes a circular rotation to the left. When the visual plane 
 is depressed, on deviating the eye to the right or left, there is a corresponding circular rotation to 
 the right or left. Or we may express the result thus : When the angle of elevation and the angle 
 of deviation have the same sign (-|- or — ), then the rotation of the eyeball is negative; when, 
 however, the signs are unequal, the rotation is positive. In order to make the circular rotation 
 visible in one's own eye, accommodate one eye lor a surface divided by vertical and horizontal lines 
 until a positive after image is produced, and then rapidly rotate the eye into the third position. The 
 lines of the after image then form angles with the lines of the background. As the position of the 
 vertical meridian of the eye is important from a practical point of view, it is necessary to note that, 
 in the primary and secondary positions of the eyes, the vertical meridian retains its vertical position. 
 On looking to the left and upward, or to the right and downward, the vertical meridians of both 
 eyes are turned to the left ; conversely, they are turned to the right on looking to the left and down- 
 ward, or to the right and upward. 
 
 In the secondary positions of the eye, rotation of the axis of the eye never occurs (Listing). 
 Very slight rolling of the eyes occurs, however, when the head is inclined toward the shoulder, and 
 in the direction opposite to that of the head (Javal) — it is about 1° for every io° of inclination of 
 the head (Skrebitzky, Nagel). 
 
 Ocular Muscles. — The movements of the eyeball are accomplished by 
 means of the four straight and two oblique ocular muscles. In order 
 to understand the action of each of these muscles, we must know the plane 
 of traction of the muscles and the axis of rotation of the eyeball. The 
 plane of traction is found by the plane lying in the middle of the origin 
 and insertion of the muscle and the point of rotation of the eyeball. The 
 axis of rotation is always at right angles to the plane of traction in the 
 point of rotation of the eyeball. 
 
 The rectus internus (I) and externus (E) rotate the eye almost exactly 
 inward and outward (Fig. 499). The plane of traction lies in the plane of the 
 paper ; Q, E, is the direction of the traction of the external rectus, Q,, I, that of 
 the internal. The axis of rotation is in the point of rotation, O, at right angles 
 to the plane of the paper, so that it coincides with the vertical axis of the eyeball. 
 2. The axis of rotation of the R. superior and inferior (the dotted line, R. 
 sup., R. inf.), lies in the horizontal plane of separation of the eye, but it forms 
 an angle of about 2q° with the transverse axis (Q, Q,) ; the direction of the 
 traction for both muscles is indicated by the line, s, i. By the action of these 
 muscles, the cornea is turned upward and slightly inward, or downward and 
 slightly inward. 3. The axis of rotation of both oblique muscles (the dotted 
 5i 
 
 \ 
 
802 
 
 OCULAR MUSCLES. 
 
 lines, Obi. sup. and Obi. inf.) also lies in the horizontal plane of separation 
 of the eyeball, and it forms an angle of 6o° with the transverse axis. The 
 direction of the traction of the inferior oblique gives the line, a, b\ that of 
 the superior, the line, c, d. The action of these muscles, therefore, is in the 
 one case to rotate the cornea outward and upward, and in the other outward 
 and downward. These actions, of course, only obtain when the eyes are 
 in the primary position — in every other position the axis of rotation of each 
 muscle changes. 
 
 When the eyes are at rest, the muscles are in equilibrium. Owing to the power 
 of the internal recti, the visual axes converge and would meet, if prolonged 40 
 centimetres in front of the eye. In the movements of the eyeball, one, two, or 
 
 
 V* 
 
 & 
 
 
 
 ^"\ ^ 
 
 Q[ 
 
 
 ■fir 1 
 
 
 \ w .°^ 
 
 
 
 w a 
 
 —V^l- inf. 
 
 * 
 
 r>* 
 
 Vf 
 
 ^ 
 
 E j I 
 
 Scheme of the action of the ocular muscles. 
 
 three muscles may be concerned. One muscle acts only when the eye is moved 
 directly outward or inward, especially the internal and external rectus. Two 
 muscles act when the eyeball is moved directly upward (superior rectus and 
 inferior oblique), or downward (inferior rectus and superior oblique). Three 
 muscles are in action when the eyeballs take a diagonal direction, especially 
 for inward and upward, by the internal and the superior rectus and inferior 
 oblique ; for inward and downward, the internal and inferior rectus and 
 superior oblique; for outward and downward, the external and inferior rectus 
 and superior oblique ; for outward and upward, the external and superior 
 rectus and inferior oblique. 
 
IDENTICAL POINTS OF THE RETINA. 803 
 
 [The following table shows the action of the muscles of the eyeball : — 
 
 Inward Rectus internus. 
 
 Outward Rectus externus. 
 
 ... , f Rectus superior. 
 
 U t ward \Obliquus inferior. 
 
 „ , f Rectus inferior. 
 
 Downward j Obliquus superior. 
 
 {Rectus internus. 
 Rectus superior. 
 Obliquus inferior. 
 
 ( Rectus internus. 
 Inward and downward . I Rectus inferior. 
 
 ( Obliquus superior. 
 
 (Rectus externus. 
 Rectus superior. 
 Obliquus inferior. 
 ( Rectus externus. 
 Outward and downward. 1 Rectus inferior. 
 
 ( Obliquus superior.] 
 
 Ruete imitated the movements of the eyeballs by means of a model, which he called the oph- 
 thalmotrope. 
 
 The size of the eyeball and its length diminish with age. The mobility is less in the vertical than 
 in the lateral direction, and less upward than downward. The normal and myopic eye can be 
 moved more outward, and the long-sighted eye more inward, the external and internal rectus act 
 most when the eye is moved outward, the obliqui when it is rotated inward. An eye can be turned 
 inward to a greater extent when the other eye at the sfime time is turned outward than when the 
 other is turned inward. During near vision, the right eye can be turned less to the right, and the 
 left to the left, than during distant vision (Hering). 
 
 Simultaneous Ocular Movements. — Both eyes are always moved simul- 
 taneously. Even when one eye is quite blind, the ocular muscles move when the 
 whole eyeball is excited. When the head is straight, the movements always take 
 place so that both visual planes (visual axes) lie in the same plane. In front both 
 visual axes can diverge only to a trifling extent, while they can converge consider- 
 ably. If individual ocular muscles are paralyzed, the position of the visual axis 
 in the same place is disturbed, and squinting results, so that the patient no longer 
 can direct both visual axis simultaneously to the same point, but he directs the 
 one eye after the other. Even nystagmus (p. 738) occurs in both eyes simulta- 
 neously, and in the same direction. The innate simultaneous movement of both 
 eyes is spoken of as an associated movement (Joh. Miiller). E. Hering 
 snowed that in all ocular movements, there is a uniformity of the innervation as 
 well. Even during such movements, in which one eye apparently is at rest, there 
 is a movement, due to the action of two antagonistic forces, the movements result- 
 ing in a slight to and fro motion of the eyeball. 
 
 The motor nerves of the ocular muscles are the oculomotorius (§ 345), the trochlearis (g 346), 
 and the abducens ((j 348). The centre lies in the corpora quadrigemina, and below it ($ 379), and 
 partly in the medulla oblongata ({j 379). 
 
 400. BINOCULAR VISION.— Advantages.— Vision with both eyes 
 affords the following advantages : {1) The field of vision of both eyes is consider- 
 ably larger than that of one eye. (2) The perception of depth is rendered easier, 
 as the retinal images are obtained from two different points. (3) A more exact 
 estimate of the distance and size of an object can be formed, in consequence of 
 the perception of the degree of convergence of both eyes. (4) The correction of 
 certain errors in the one eye is rendered possible by the other. 
 
 When the position of the head is fixed, we can easily form a conception as to the form of the 
 entire field of vision if we close one eye and direct the open eye inward. We observe that it is 
 pear-shaped, broad above and smaller below, the silhouette, or profile of the nose, causes the de- 
 pression between the upper and lower part of the field. 
 
 401. SINGLE VISION— IDENTICAL POINTS— HOROPTER. 
 — Identical Points. — If we imagine the retinae of both eyes to be a pair of hollow 
 saucers placed one within the other, so that the yellow spots of both eyes coincide, 
 and also the similar quadrants of the retinae, then all those points of both retinae 
 which coincide or cover each other are called "identical" or " correspond- 
 ing points " of the retina. The two meridians which separate the quadrants 
 coinciding with each other are called the "lines of separation." Physiologi- 
 cally, the identical points are characterized by the fact that when they are both 
 simultaneously excited by light, the excitement proceeding from them is, by a 
 
804 
 
 THE HOROPTER. 
 
 psychical act, referred to one and the same point of the field of vision, lying, of 
 course, in a direction through the nodal point of each eye. Stimulation of both 
 identical points causes only one image in the field of vision. Hence all those 
 objects of the external world, whose rays of light pass through the nodal points 
 to fall upon identical points of the retina, are seen singly, because their images 
 from both eyes are referred to the same point of the field of vision, so that 
 they cover each other. All other objects whose images do not fall upon identical 
 points of the retina cause " double vision," or " diplopia." 
 
 Proofs. — If we look at a linear object with the points I, 2, 3, then the corresponding retinal 
 images are 1, 2, 3 and 1, 2, 3, which are, obviously, identical points of the retinae (Fig. 500). If, 
 while looking at this line, there be a point, A, nearer the eyes, or B, further from them, then, on 
 focussing for 1, 2, 3, neither the rays (A, a, A, a) coming from A, nor those (B, b, B, b) from B, 
 fall upon identical points ; hence A and B appear double. 
 
 Make a point (e.g., 2) with ink on paper; of course the image will fall upon both foveae centrales 
 of the retina: (2, 2), which, of course, are identical points. Now press laterally upon one eye, so 
 as to displace it slightly; then two points At once appear, because the image of the point no longer 
 falls upon the fovea centralis of the displaced eye, but on an adjoining non-identical part of the 
 retina. When we squint voluntarily all objects appear double. 
 
 Fig. 500. 
 
 B 
 
 Fig. 501. 
 
 1 / Z \ 3 
 
 Scheme of identical and non-identical points of the 
 retina. 
 
 horopter for the secondary position, with 
 convergence of the visual axes. 
 
 The vertical surfaces of separation of the retina do not exactly coincide with the vertical meri- 
 dians. There is a certain amount of divergence (o.5°-3°), less above, which varies in different 
 individuals, and it may be in the same individual at different times (Hering, Danders). The hori- 
 zontal lines of separation, however, coincide. Images which fall upon the vertical lines of separa- 
 tion appear to be vertical to those on the horizontal lines, although they are not actually so. Hence 
 the vertical lines of separation are the apparent vertical meridians. Some observers regard the 
 identical points of the retina as an acquired arrangement ; others regard it as normally innate. 
 Persons who have had a squint from their birth see singly ; in these cases the identical points must 
 be differently disposed. 
 
 The horopter represents all those points of the outer world from which rays 
 of light passing into both eyes fall upon identical points of the retina, the eyes 
 being in a certain position. It varies with the different positions of the eyes. 
 
 1. In the primary position of both eyes with the visual axes parallel, the rays of direction pro- 
 ceeding from two identical points of the two retinas are parallel and intersect only at infinity. Hence 
 for the primary position the horopter is a plane in infinity. 
 
 2. In the secondary position of the eyes with converging visual axes, the horopter for the trans- 
 verse lines of separation is a circle which passes through the nodal points of both eyes (Fig. 501, 
 
STEREOSCOPIC VISION. 805 
 
 K, K) and through the fixed points I, II, III (Jok. Muller). The horopter of the vertical lines of 
 separation is in this position vertical to the plane of vision. 
 
 3. In the symmetrical tertiary position, in which the horizontal and vertical lines of separation 
 form an angle, the horopter of the vertical lines of separation is a straight line inclined toward the 
 horizon. There is no horopter for the identical points of the horizontal lines of separation, as the 
 lines of direction prolonged from the identical points of these points do not intersect. 
 
 4. In the unsymmetrical tertiary position (with rolling) of the eyes, in which the fixed point lies 
 at unequal distances from both nodal points, the horopter is a curve of a complex form. 
 
 All objects, the rays proceeding from which fall upon non-identical points of 
 the retinae, appear double. We can distinguish direct or crossed double images, 
 according as the rays prolonged from the non-identical points of the retina inter- 
 sect in front or behind the fixed point. 
 
 Experiment. — Hold two fingers — the one behind the other — before both eyes. Accommodate 
 for the far one, and then the near one appears double ; and when we accommodate for the near 
 one, the far one appears double. If, when accommodating for the near one, the right eye be closed, 
 the left (crossed) image of the far finger disappears. On accommodating for the far finger and 
 closing the right eye, the right (direct) double image of the near finger disappears. 
 
 Double images are referred to the proper distance from the eyes, just as single 
 images are. 
 
 Neglect of Double Images. — Notwithstanding the very large number of 
 double images which must be formed during vision, they do not disturb vision. 
 As a general rule, they are " neglected," so that the attention must, as a rule, be 
 directed to them before they are perceived. This condition is favored thus : — 
 
 1. The attention is always directed to the point of the field of vision which is accommodated for 
 at the time. The image of this part is projected on to both yellow spots, which are identical points 
 of the retina. 
 
 2. The form and color of objects on the lateral parts of the retina are not perceived so sharply. 
 
 3. The eyes are always accommodated for those points which are looked at. Hence, indistinct 
 images with diffusion circles are always formed by those objects which yield double images, so that 
 they can be more readily neglected. 
 
 4. Many double images lie so close together that the greater part of them, when the images are 
 large, covers the other. 
 
 5. By practice, images which do not exactly coincide may be united. 
 
 402. STEREOSCOPIC VISION.— On looking at an object, both eyes 
 do not yield exactly similar images of that object — the images are slightly differ- 
 ent, because the two eyes look at the object from two different points of view. 
 With the right eye we can see more of the side of the body directed toward it, 
 and the same is the case with the left eye. Notwithstanding this inequality, the 
 two images are united. How two different images are combined is best under- 
 stood by analyzing the stereoscopic images. 
 
 Let, in Fig. 502, L and R represent two such images as are obtained with the left and right eyes. 
 These images, when seen with a stereoscope, look like a truncated 
 pyramid, which projects toward the eye of the observer, as the 
 points indicated by the same signs cover each other. On measur- 
 ing the distance of the points, which coincide or cover each other 
 in both figures, we find that the distances A, a, B, b, C, c, D, d, are 
 equally great, and at the same time are the widest of all the points 
 of both figures ; the distances E, e, ¥,/,G,g,H,A, are also equal, 
 but are smaller than the former. On looking at the coinciding 
 lines (A, E, ", e, and B, F, b,f) we observe that all the points of 
 this line which lie near to A a and B b are further apart than those 
 lying nearer E e and Ff. 
 
 Comparing these results with the stereoscopic image, Two stereoscopic drawings 
 we have the following laws for stereoscopic vi- 
 sion : 1. All those points of two stereoscopic images, and, of course, of two retinal 
 images of an object, which in both images are equally distant from each other, ap- 
 pear on the same plane. 2. All points which are nearer to each other, compared with 
 the distance of other points, appear to be nearer to the observer. 3. Conversely, 
 
806 
 
 THEORY OF STEREOSCOPIC VISION. 
 
 all points which lie further apart from each other appear perspectively in the 
 background. 
 
 The cause of this phenomenon lies in the fact that, " in vision with both eyes 
 we constantly refer the position of the individual images in the direction of the 
 visual axis to where they both intersect." 
 
 Proofs. — The following stereoscopic experiment (Fig. 503) proves this : Take both images of 
 two pairs of points (a, b, and a, /3), which are at unequal distances from each other on the sur- 
 face of the paper. By means of small, stereoscopic prisms cause them to coincide, then the com- 
 bined point, A of a, and a appears at a distance on the plane of the paper, while . the other point, 
 B, produced by the superposition of b and /?, floats in the air before the observer. Fig. 503 shows 
 how this occurs. The following experiment shows the same result : Draw two figures, which are 
 to be superposed similar to the lines B, A, A, E, b, a, and a, e, in Fig. 502. In the lines B, A, 
 and b, a, all the points which are to be superposed lie equally distant from each other, while, on the 
 contrary, all the points in A, E, and a, e, which lie nearer E and e, are constantly nearer to each 
 other. When looked at with a stereoscope, the superposed verticals, A, e, and B, b, lie in the plane 
 of the paper, while the superposed lines, A, a, and E,e, project obliquely toward the observer from 
 the plane of the paper. From these two fundamental experiments we may analyze all pairs of 
 
 Fig. 503. 
 
 Scheme of Brewster's stereoscope. 
 
 Wheatstone's stereoscope. 
 
 stereoscopic pictures. Thus, in Fig. 502, if we exchange the two pictures, so that R lies in the 
 place of L, then we must obtain the impression of a truncated hollow pyramid. 
 
 Two stereoscopic pictures, which are so constructed that the one contains the body from the 
 front and above, and the other, it from the front and below (suppose in Fig. 502 the lines A B and 
 a b were the ground lines), can never be superposed by means of the stereoscope. 
 
 This process has been explained in another way. Of the two figures, R and L 
 (Fig. 502), only A B C D and abed fall upon identical points of the retina, 
 hence these alone can be superposed ; or, when there is a different convergence 
 of the visual axis, only E F G H and efg h can be superposed for the same 
 reason. Suppose the square ground surfaces of the figures are first superposed, in 
 order to explain the stereoscopic impression, it is further assumed that both eyes, 
 after superposition of the ground squares, are rapidly moved toward the apex of the 
 pyramid. As the axis of the eyes must thereby converge more and more, the 
 apex of the pyramid appears to project ; as all points which require the conver- 
 gence of the eyes for their vision appear to us to be nearer (see below). Thus, all 
 
THE TELESTEREOSCOPE. 
 
 807 
 
 corresponding parts of both figures would be brought, one after the other, upon 
 identical points of the retina by the movements of the eyes (Brucke). 
 
 It has been urged against this view that the duration of an electrical spark 
 suffices for stereoscopic vision (Dove) — a time which is quite insufficient for the 
 movements of the eyes. Although this may be true for many figures, yet in the 
 correct combination of complex or extraordinary figures, these movements of the 
 visual axes are not excluded, and in many individuals they are distinctly advan- 
 tageous. Not only the actual movements necessary for this act, but the sensations 
 derived from the muscles are also concerned. 
 
 When two figures are momentarily combined to form a stereoscopic picture, 
 there being no movement of the eyes, clearly many points in the stereoscopic 
 pictures are superposed which, strictly speaking, do not fall upon identical points 
 of the retina. Hence we cannot characterize the identical points of the retina 
 as coinciding mathematically ; but, from a physiological point of view, we must 
 regard such points as identical, which, as a rule, by simultaneous stimulation, 
 give rise to a single image. The mind obviously plays a part in this combination 
 of images. There is a certain psychical tendency to fuse the double images on 
 the retinae into one image, in accordance with the fact that we, from experience, 
 
 Fig. 505. 
 
 w 
 
 Fig. 506. 
 
 Telestereoscope of v. Helmholtz. 
 
 Wheatstone's Pseudoscope. 
 
 recognize the existence of a single object. If the differences between two stereo- 
 scopic pictures be too great, so that parts of the retina too wide apart are excited 
 thereby, or when new lines are present in a picture, and do not admit of a stereo- 
 scopic effect, or disturb the combination, then the stereoscopic effect ceases. 
 
 The stereoscope is an instrument by means of which two somewhat similar pictures drawn in 
 perspective may be superposed so that they appear single. Wheatstone (1838) obtained this result 
 by means of two mirrors placed at an angle (Fig. 504) ; Brewster (1843) by two prisms (Fig. 503). 
 The construction and mode of action are obvious from the illustrations. 
 
 Some pairs of two such pictures may be combined, without a stereoscope, by directing the visual 
 axis of each eye to the picture held opposite to it. 
 
 Two completely identical pictures, i. c, in which all corresponding points have exactly the same 
 relation to each other, as the same sides of two copies of a book, appear quite flat under the sterSo- 
 scope ; as soon, however, as in one of them one or more points alters its relation to the corresponding 
 points, this point either projects or recedes from the plane. 
 
 Telestereoscope. — When objects, placed at a great distance, are looked at,c.g., the most distant 
 part of a landscape, they appear to us to be flat, as in a picture, and do not stand out, because the 
 slight differences of position of our eyes in the head are not to be compared with the great distance. 
 In order to obtain a stereoscopic view of such objects, v. Helmholtz constructed the telestereoscope 
 (Fig. 505), an apparatus which, by means of two parallel mirrors, places, as it were, the point of 
 view of both eyes wider apart. Of the mirrors, L and R each projects its image of the landscape 
 
808 ESTIMATION OF SIZE AND DISTANCE. 
 
 upon / and r, to which both eyes, O, o, are directed. According to the distance between L and R, 
 the eyes, O, o, as it were, are displaced to 0/, o r The distant landscape appears like a stereo- 
 scopic view. In order to see distant parts more clearly and nearer, a double telescope or opera 
 glass may be placed in front of the eyes (p. 809). 
 
 Take two corresponding stereoscopic pictures, with the surfaces black in one case and light in 
 the other. Draw two truncated pyramids like Fig. 502, make one figure exactly like L, i. e., with 
 a white surface and black lines, and the other with white lines and a black surface, then under the 
 stereoscope such objects glance. The causing of the glancing condition is that the glancing body 
 at a certain distance reflects bright light into one eye and not into the other, because a ray reflected 
 at an angle cannot enter both eyes simultaneously (Dove). 
 
 Wheatstone's Pseudoscope consists of two right-angled prisms (Fig. 506, A and B) enclosed 
 in a tube, through which we can look in a direction parallel with the surfaces of the hypotenuses. 
 If a spherical surface be looked at with this instrument, the image formed in each eye is inverted 
 laterally. The right eye sees the view usually obtained by the left eye, and conversely ; the shadow 
 which the body in the light throws upon a light ground is reversed. Hence the ball appears hollow. 
 
 Struggle of the Fields of Vision. — The stereoscope is also useful for the following purpose : 
 In vision with both eyes, both eyes are almost never active simultaneously and to the same extent ; 
 both undergo variations, so that first the impression on the one.re.tina and then that on the other is 
 stronger. If two different surfaces be placed in a stereoscope, then, especially when they are 
 luminous, these two alternate in the general field of vision, according as one or other eye is active 
 (Panum). Take two surfaces with lines ruled on them, so that when the surfaces are superposed 
 the lines will cross each other, then either the one or the other system of lines is more prominent 
 (Panum). The same is true with colored stereoscopic figures, so that there is a contest or struggle 
 of the colored fields of vision. 
 
 403. ESTIMATION OF SIZE AND DISTANCE— FALSE ES- 
 TIMATES OF SIZE AND DIRECTION.— Size.— We estimate the 
 size of an object — apart from all other factors — from the size of the retinal 
 image ; thus the moon is estimated to be larger than the stars. If, while looking 
 at a distant landscape, a fly should suddenly pass across our field of vision, near 
 to our eye, then the image of the fly, owing to the relatively great size of the 
 retinal image, may give one the impression of an object as large as a bird. If, 
 owing to defective accommodation, the image gives rise to diffusion circles, the 
 size may appear to be even greater. But objects of very unequal size give equally 
 large retinal images, especially if they are placed at such a distance that they form 
 the same visual angle (Fig. 465) ; so that in estimating the actual size of an 
 object, as opposed to the apparent size determined by the visual angle, the 
 estimate of distance is of the greatest importance. 
 
 As to the distance of an object, we obtain some information from the feeling 
 of accommodation, as a greater effort of the muscle of accommodation is re- 
 quired for exact vision of a near object than for seeing a distant one. But, as 
 with two objects at unequal distances giving retinal images of the same size, we 
 know from experience that that object is smaller which is near, then that object is 
 estimated to be the smaller for which, during vision, we must accommodate more 
 strongly. 
 
 In this way we explain the following : A person beginning to use a microscope always observes 
 with the eyes accommodated for a near object, while one used to the microscope looks through it 
 without accommodating. Hence beginners always estimate microscopic objects as too small, and 
 on making a drawing of them it is too small. If we produce an after image in one eye, it at once 
 appears smaller on accommodating for a near object, and again becomes larger during negative ac- 
 commodation. If we look with one eye at a small body placed as near as possible to the eye, then 
 a body lying behind it, but seen only indirectly, appears smaller. 
 
 t Angle of Convergence of Visual Axes. — In estimating the size of an 
 object, and taking into account our estimate of its distance, we also obtain much 
 more important information from the degree of convergence of the visual axes. 
 We refer the position of an object, viewed with both eyes, to the point where both 
 visual axes intersect. The angle formed by the two visual axes at this point is 
 called the "angle of convergence of the visual axes" (" Gesichtswinkel"). The 
 larger, therefore, the visual angle, the size of the retinal image remaining the same 
 — we judge the object to be nearer. The nearer the object is, it may be the smaller 
 
ESTIMATION OF DISTANCE. 
 
 809 
 
 in order to form a "visual angle " of the same size, such as a distant large 
 object would give. Hence, we conclude, that with the same apparent size (equally 
 large visual angle, or retinal images of the same size) we judge that object to be 
 smallest which gives the greatest convergence of the visual axes during binocular 
 vision. As to the muscular exertion necessary for this purpose, we obtain infor- 
 mation from the muscular sense of the ocular muscles. 
 
 Experiments and Proofs. — The Chessboard Phenomenon of H. Meyer. — i. If we look at 
 a uniform chessboard-like pattern (tapestry), then, when the visual axes are directed directly for- 
 ward, the spaces on the pattern appear of a certain size. If, now, we look at a nearer object, we 
 may cause the visual axes to cross, when the pattern apparently moves toward the plane of the fixed 
 point, so that the crossed double images are superposed, and the pattern at once appears smaller. 
 
 2. Rollett looks at an object through two thick plates of glass placed at an angle. The plates are 
 at one time so placed that the apex of the angle is directed toward the observer (Fig. 507, II), at 
 another in the reverse position (I). If both eyes,/and i, are to see the object a, in I, then as 
 the glass plates so displace the rays, a, c, and a, g, as to make them parallel with the direction of 
 these rays, viz., e,f, and h, i, then the eyes must converge more than when they are turned directly 
 toward a. Hence the object appears nearer and smaller, as at a. In II, the rays, 6 1 k, and b l 0, 
 from the nearer object i lt fall upon the glass plates. In order to see i lt the eyes (« and q) must 
 diverge more, so that i appears more distant and larger. 
 
 Fig. 507. 
 
 r i n 
 
 I I 
 
 Rollett's glass plate apparatus. 
 
 Fig. 508. 
 
 Zollner's lines. 
 
 3. In looking through Wheatstone 's reflecting stereoscope (Fig. 504, II), it is obvious that the 
 more the two images approach the observer, the more must the observer converge his visual axes, 
 because the angles of incidence and reflexion are greater. Hence the compound picture now ap- 
 pears to him to be smaller. If the centre of the image, R, recedes to Rj, then of course the angle, 
 S,i, rp, is equal to S 1? fR„ and the same on the left side. 
 
 4. In using the telestereoscope, the two eyes are, as it were, separated from each other, then, of 
 course, in looking at objects at a certain distance, the convergence of the visual axes must be grtater 
 than in normal vision. Hence objects in a landscape appear as in a small model. But as we are 
 accustomed to infer that such small objects are at a great distance, hence the objects themselves ap- 
 pear to recede in the distance. 
 
 Estimation of Distance. — When the retinal images are of the same size, we 
 estimate the distance to be greater the less the effort of accommodation, and 
 conversely. In binocular vision, when the retinal images are of the same size, we 
 infer that that object is most distant for which the optic axes are least converged, 
 and conversely. Thus the estimation of size and distance go hand in hand, in 
 great part at least, and the correct estimation of the distance also gives us a cor- 
 rect estimate of the size of objects {Descartes). A further aid to the estimation 
 of distance is the observation of the apparent displacement of objects, on moving 
 
810 THE LACHRYMAL APPARATUS. 
 
 our head or body. In the latter, especially, lateral objects appear to change their 
 position toward the background, the nearer they are to us. Hence, when travel- 
 ing in a train, in which case the change of position of the objects occurs very 
 rapidly, the objects themselves are regarded as nearer (Sick'), and also smaller 
 (Dove). Lastly, those objects appear to us to be nearest which are most distinct 
 in the field of vision. 
 
 Example. — A light in a dark landscape, and a dazzling crown of snow on a hill, appear to be 
 near to us ; looked at from the top of a high mountain, the silver glancing curved course of a river 
 not unfrequently appears as if it were raised from the plane. 
 
 False Estimates of Size and Direction. — i. A line divided by intermediate points appears 
 longer than one not so divided. Hence, the heavens do not appear to us as a hollow sphere, but 
 as curved like an ellipse ; and for the last reason the disk of the setting sun is estimated to be 
 larger than the sun when it is in the zenith {Ptolemy, 150 A.D.). 2. If we move a circle slowly to 
 and fro behind a slit it appears as a horizontal ellipse, if we move it rapidly it appears as a vertical 
 ellipse. 3. If a very fine line be drawn obliquely across a vertical thick black line, then the 
 direction of the fine line beyond the thick one appears to be different from its original direction. 
 4. Zollner's Lines. — Draw three parallel horizontal lines 1 centimetre apart, and through the 
 upper and lower ones draw short oblique parallel lines in the direction from above and the left to 
 below and the right ; through the middle line draw similar oblique lines, but in the opposite 
 direction, then the three horizontal lines no longer appear to be parallel. [Fig. 508 shows a 
 modification of this. The lines are actually parallel, although some of them appear to converge 
 and others to diverge.") If we look in a dark room at a bright vertical line, and then bend the 
 head toward the shoulder, the line appears to be bent in the opposite direction (Aubert). 
 
 404. PROTECTIVE ORGANS OF THE EYE.— I. The eyelids are represented in 
 section in Fig. 509. The tarsus is in reality not a cartilage, but merely a rigid plate of connective 
 tissue, in which the Meibomian glands are imbedded ; acinous sebaceous glands moisten the edges 
 of the eyelids with fatty matter. At the basal margin of the tarsus, especially of the upper one, 
 close to the reflection of the conjunctiva, there opens the acino-tubular glands of Krause. The 
 conjunctiva covers the anterior surface of the bulb as far as the margin of the cornea, over which 
 the epithelium alone is continued. On the posterior surface of the eyelid the conjunctiva is partly 
 provided with papillae. It is covered by stratified prismatic epithelium. Coiled glands occur in 
 ruminants just outside the margin of the cornea (Meissner), while outside this, toward the outer 
 angle of the eye in the pig, there are simple glandular sacks (Manz). Waldeyer describes modified 
 sweat glands in the tarsal margins in man. Small lymphatic sacks in the conjunctiva are called 
 trachoma glands. Krause found end bulbs in the conjunctiva bulbj. The blood vessels in the con- 
 junctiva communicate with the juice canals in the cornea and sclerotic (p. 753). The secretion of 
 the conjunctiva, besides some mucus, consists of tears, which may be as abundant as those formed 
 in the lachrymal glands. 
 
 The closure of the eyelids is accomplished by the orbicularis palpebrarum 
 (facial nerve, § 349), whereby the upper lid falls in virtue of its own weight. 
 This muscle contracts — (1) voluntarily ; (2) involuntarily (single contractions) ; 
 (3) reflexly, by stimulation of all the sensory fibres of the trigeminus distributed 
 to the bulb and its immediate neighborhood (§ 347), also by intense stimulation 
 of the retina by light ; (4) continued involuntary closure occurs during sleep. 
 
 The opening of the eyelids is brought about by the passive descent of the 
 lower one, and the active elevation of the upper eyelid by the levator palpebral 
 superioris (§ 345). The smooth muscular fibres of the eyelids also aid (p. 623). 
 
 II. The lachrymal apparatus consists of the lachrymal glands, which in structure closely 
 resemble the parotid, their acini being lined by low, cylindrical, granular epithelium. Four to five 
 larger and eight to ten smaller excretory ducts conduct the tears above the outer angle of the lid 
 into the fornix conjunctiva. The tear ducts, beginning at the puncta lachrymalia, are composed 
 of connective and elastic tissue, and are lined by stratified squamous epithelium. Striped muscle 
 accompanies the duct, and by its contraction keeps the duct open ( Wedl). Toldt found no 
 sphincter surrounding the puncta lachrymalia, while Gerlach found an incomplete circular muscu- 
 lature. The connective-tissue covering of the tear sack and canal is united with the adjoining 
 periosteum. The thin mucous membrane, which contains much adenoid tissue and lymph cells, is 
 lined by a single layer of ciliated cylindrical epithelium, which below passes into the stratified form. 
 The opening of the duct is often provided with a valve-like fold (Hasner's valve). 
 
 The conduction of the tears occurs between the lids and the bulb by means 
 of capillarity, the closure of the eyelids aiding the process. The Meibomian 
 
THE CONDUCTION OF TEARS. 
 
 811 
 
 secretion prevents the overflow of the tears [just as greasing the edge of a glass 
 vessel prevents the water in it from overflowing]. The tears are conducted from 
 the puncta through the duct, chiefly by a siphon action {Ad. Weber). Horner's 
 muscle (also known to Duvernoy, 1678) likewise aids, as every time the eyelids 
 are closed it pulls upon the posterior wall of the sack, and thus dilates the latter, 
 so that it aspirates tears into it (Henke). 
 
 a n 
 
 Vertical section through the upper eyelid {after Waldeyet). A, cutis* ; i, epidermis ; 2, chorium ; B and 3, subcuta- 
 neous connective tissue ; C and 7, orbicularis muscle and its bundles ; Z>, loose sub-muscular connective tissue ; 
 E, insertion of H. Mtiller's muscle ; F, tarsus ; G, conjunctiva ; J, inner edge of the lid : K, outer edge ; 4, pig- 
 ment cells in the cutis ; 5, sweat glands ; 6, hair follicles with hairs ; 8 and 23, sections of nerves ; 9, arteries ; 10, 
 veins ; 11, cilia ; 12, modified sweat glands ; 13, circular muscle of Riolan ; 14, opening of a Meibomian gland ; 
 15, section of an acinus of the same; 16, posterior tarsal glands ; 18 and 19, tissue of the tarsus ; 20, pretarsal or 
 sub-muscular connective tissue ; 21 and 22, conjunctiva, with its epithelium ; 24, fat ; 25, loosely woven posterior 
 end of the tarsus ; 26, section of a palpebral artery. 
 
 E. H. Weber and Hasner ascribe the aspiration of the tears to the diminution of the amount of 
 air in the nasal cavities during inspiration. Arlt asserts that the tear sack is compressed by the con- 
 traction of the orbicularis muscle, so that the tears must be forced toward the nose. Lastly, Stell- 
 wag supposes that when the eyelids are closed, the tears are simply pressed into the puncta, while 
 Gad denies that there is any kind of pumping mechanism in the nasal canal. Landois points out 
 that the tear ducts are surrounded by. a plexus of veins, which, according to their state of distention, 
 may influence the size of these tubes. 
 
812 COMPARATIVE HISTORICAL. 
 
 The secretion of tears takes place only by direct stimulation of the lachrymal 
 nerve (§ 347, I, 2), subcutaneous malar (§ 347, II, 2) and cervical sympathetic 
 (§ 356, A, 6), which have been called secretory nerves. Secretion may also be 
 excited reflexly (p. 623) by stimulation of the nasal mucous membrane only on 
 the same side {Herzenstein). The ordinary secretion in the waking condition is 
 really a reflex secretion produced by the stimulation of the anterior surface of the 
 bulb by the air or by the evaporation of tears. In sleep all these factors are 
 absent, and there is no secretion. Histological Changes. — Reichel found that 
 in the active gland (after injection of pilocarpin), the secretory cells became 
 granular, turbid and smaller, while the outlines of the cells became less distinct 
 and the nuclei spheroidal. In the resting gland the cells are bright and slightly 
 granular, with irregular nuclei. Intense stimulation by light acting on the optic 
 nerve causes a reflex secretion of tears. The flow of tears accompanying certain 
 violent emotions, and even hearty laughing, is still unexplained. During cough- 
 ing and vomiting the secretion of tears is increased, partly reflexly and partly by 
 the outflow being prevented by the expiratory pressure. 
 
 Function. — The tears moisten the bulb, prevent it from drying, and float 
 away small particles, being aided in this by the closure of the eyelids. Atropin 
 diminishes the tears (Mogaard). 
 
 Composition. — The tears are alkaline, saline to taste, and represent a " serous " 
 secretion. Water, 98.1 to 99 ; 1.46 organic substances (0.1 albumin and mucin, 
 0.1 epithelium) ; 0.4 to 0.8 salts (especially NaCl). 
 
 [Action of Drugs. — Essential volatile oils and eserin increase the secretion of tears, atropin 
 arrests it, while eserin antagonizes the effect of atropin and causes an increased secretion.] 
 
 405. COMPARATIVE— HISTORICAL.— Comparative.— The simplest form of visual 
 apparatus is represented by aggregations of pigment cells in the outer coverings of the body, which 
 are in connection with the termination of afferent nerves. The pigment absorbs the rays of light, 
 and in virtue of the light ether discharges kinetic energy, which excites the terminations of the 
 nervous apparatus. Collections of pigment cells, with nerve fibres attached, and provided with a 
 clear refractive body, occur on the margin of the bell of the higher medusae, while the lower forms 
 have only aggregations of pigment on the bases of their tentacles. Also, in many lower worms 
 there are pigment spots near the brain. In others the pigment lies as a covering round the termi- 
 nations of the nerves, which occur as "crystalline rods" or "crystalline spheres." In parasitic 
 worms the visual apparatus is absent. In star fishes the eyes are at the tips of the arms, and 
 consist of a spherical crystal organ surrounded with pigment, with a nerve going to it. In all 
 other eehinodermata there are only accumulations of pigment. Among the annulosa there are 
 several grades of visual apparatus — (1) Without a cornea there may be only one crystal sphere 
 (nervous end organ) near the brain, as in the young of the crab ; or there may be several crystal 
 spheres forming a compound eye, as in the lower crabs. (2) With a cornea, consisting of a len- 
 ticular body formed from the chitin of the outer integument, the eye itself may be simple, merely 
 consisting of one crystal rod, or it may be compound. The compound eye consists of only one 
 large lenticular cornea, common to all the crystal rods, as in the spiders ; or each crystal rod has a 
 special lenticular cornea for itself. The numerous rods surrounded by pigment are closely packed 
 together, and are arranged upon a curved surface, so that their free ends also form a part of a sphere. 
 The chitinous investment of the head is faceted, and forms a small corneal lens on the free end of 
 each rod. According to one view, each facette, with the lens and the crystal sphere, is a special 
 eye, and just as man has two eyes, so insects have several hundred. Each eye sees the picture of 
 the outer world in toto. This view is supported by the following experiment of van Leeuwenhock : 
 If the cornea be sliced off, each facette thereof gives a special image of an object. If a cross be 
 made on the mirror of a microscope, while a piece of the faceted cornea is placed as an object upon 
 the stage, then we see an image of the cross in each facette of the cornea. Thus, for each rod 
 (crystal sphere) there would be a special image. Each corneal facette, however, forms only a part 
 of the image of the outer world, so that we must regard the image as composed like a mosaic. 
 Among mollusca the fixed branchipoda have two pigment spots near the brain, but only in their 
 larval condition ; while the mussel has, under similar conditions, pigment spots with a refractive 
 body. The adult mussel, however, has pigment spots (oceli) only in the margin of the mantel, but 
 some molluscs have stalked and highly-developed eyes. Some of the lower snails have no eyes, 
 some have pigment spots on the head, while the garden snail has stalked eyes provided with a cornea, 
 an optic nerve with retina and pigment, and even a lens and vitreous body. Among cephalopoda 
 the nautilus has no cornea or lens, so that the sea water flows freely into the orbits. Others have a 
 lens and no cornea, while some have an opening in the cornea (Loligo, Sepia, Octopus). All the 
 
COMPARATIVE HISTORICAL. 813 
 
 other parts of the eye are well developed. Among vertebrata amphioxus has no eyes. They 
 exist in a degenerated condition in Proteus and the mammal Sp'alax. In many fishes, amphibians 
 and reptiles the eye is covered by a piece of transparent skin. Some hag-fishes, the crocodile, and 
 birds have eyelids, and a nictitating membrane at the inner angle of the eye. Connected with 
 it is the Harderian gland. In mammals the nictitating process is represented only by the plica 
 semilunaris. There is no lachrymal apparatus in fishes. The tears of snakes remain under the 
 watch-glass-like cutis with which the eye is covered. The sclerotic often contains cartilage which 
 may ossify. A vascular organ, the processus falciformis, passes from the middle of the choroid 
 into the interior of the vitreous body in osseous fishes, its anterior extremity being termed the cam- 
 panula Halleri. Similarly, there is the pecten in birds, but it is provided with muscular fibres. In 
 birds the cornea is surrounded by a bony ring. The whale has an enormously thick sclerotic. In 
 aquatic animals the lens is nearly spherical. The muscles of the iris and choroid are trans- 
 versely striped in birds and reptiles. The retinal rods in all vertebrates are directed from before 
 backward, while the analogous elements (crystal rods and spheres) in invertebrata are directed from 
 behind forward. 
 
 Historical. — The Hippocratic School were acquainted with the optic nerve and lens. Aristotle 
 (384 B. c.) mentions that section of the optic nerve causes blindness — he was acquainted with after 
 images, short and long sight. Herophilus (307 B. c.) discovered the retina, and the ciliary pro- 
 cesses received their name in his school. Galen (131-203 A. D.) described the six muscles of the 
 eyeball, the puncta lachrymalia, and tear duct. Aeranger (1521) was aware of the fatty matter at 
 the edge of the eyelids. Stephanus (1545) and Casseri (1609) described the Meibomian glands, 
 which were afterward redescribed by Meibom (1666). Fallopius described the vitreous membrane 
 and the ciliary ligament. Plater(l583) mentions that the posterior surface of the lens is more curved. 
 Aldrovandi observed the remainder of the pupillary membrane (1599). Observations were made 
 at the time of Vesalius (1540) on the refractive action of the lens. Leonardo da Vinci compared 
 the eye to a camera obscura. Maurolykos compared the action of the lens to that of a lens of glass, 
 but it was Kepler (1611) who first showed the true refractive index of the lens and the formation of 
 the retinal image, but he thought that during accommodation the retina moved forward and back- 
 ward. The Jesuit, Scheiner (f 1650), mentions, however, that the lens becomes more convex by 
 the ciliary processes, and he assumed the existence of muscular fibres in the uvea. He referred 
 long and short sight to the curvature of the lens, and he first showed the retinal image in an excised 
 eye. With regard to the use of spectacles there is a reference in Pliny. It is said that at the 
 beginning of the 14th century the Florentine, Saldino d'Armato degli Armati di Fir (f 1317), and 
 the monk, Alessandro de Spina (f 1313), invented spectacles. Kepler (161 1) and Descartes (1637) 
 described their action. Mayo (f 1852), described the third nerve as the constrictor nerve of the 
 pupil. Zinn contributed considerably to our knowledge of the structure of the eye. Ruysch de- 
 scribed muscular fibres in the iris, and Monro described the sphincter of the pupil (1794). Jacob 
 described the bacillary layer of the retina — Soemmering (1791) the yellow spot. Brewster and 
 Chossat (1819) tested the refractive indicesof the optical media. Purkinje (1819) studied subjective 
 vision. 
 
HEARING. 
 
 406. STRUCTURE OF THE ORGAN OF HEARING— Stimu- 
 lation of the Auditory Nerve. — The normal manner in which the auditory 
 nerve is excited by means of sonorous vibrations, which set in motion the end 
 organs of the acoustic nerve, which lie in the endolymph of the labyrinth of the 
 inner ear, on membranous expansions of the cochlea and semicircular canals. 
 Hence the sonorous vibrations are first transmitted to the fluid in the labyrinth, 
 and this, in turn, is thrown into waves, which set the end organs into vibration. 
 Thus the excitement of the auditory nerves is brought about by the mechanical 
 stimulation of the wave motion of the lymph of the labyrinth. 
 
 The fluid or lymph of the labyrinth is surrounded by the exceedingly hard osse- 
 
 Scheme of the organ of hearing. A G, external auditory meatus ; T, tympanic membrane ; K, malleus with Its head 
 
 i long process — the latter is united 
 1 ovalis ; r, fenestra rotunda ; 
 
 : //, its scala tympani, and vt, its scala vcstibuli ; V, vestibule ; 
 S, saccule ; U, utricle ; H, semicircular canals, T E ; Eustachian tube. The long arrow indicates the line of 
 traction of the tensor tympani ; the short curved one, that of the stapedius. 
 
 ous mass of the temporal bone (Fig. 510). Only at one small roundish and slightly 
 triangular point (r), the fenestra rotunda, the fluid is bounded by a delicate 
 yielding membrane, which is in contact with the air in the middle ear or tympanum 
 (P). Not far from the fenestra rotunda is the fenestra ovalis (0), in which the 
 base of the stapes (j) is fixed by means of a yielding membranous ring. The outer 
 surface of this, also, is in contact with the air in the middle ear. As the perilymph 
 of the inner ear is in contact at these two places with a yielding boundary, it is 
 clear that the lymph itself may exhibit oscillatory movements, as it must follow 
 the movements of the yielding boundaries. 
 
 814 
 
PHYSICAL INTRODUCTION. 815 
 
 The sonorous vibrations may set the perilymph in vibration in three different 
 ways : — 
 
 i. Conduction through the Bones of the Head. — This occurs especially 
 only when the vibrating solid body is applied directly to some part of the head, 
 e.g., a tuning-fork placed on the head, the sound being propagated most intensely 
 in the direction of the prolongation of the handle of the instrument — also when 
 the sound is conducted to the head by means of fluid, as when the head is 
 ducked under water. Vibrations of the air, however, are practically not transferred 
 directly to the bones of the head, as is shown by the fact that we are deaf when 
 the ears are stopped. 
 
 The soft parts of the head which lie immediately upon bone conduct sound best, and of the pro- 
 jecting part the best conductor is the cartilaginous portion of the external ear. But even under the 
 most favorable circumstance, conduction through the bones of the head is far less effective than the 
 conduction of the sound waves through the external auditory meatus. If a tuning-fork be made to 
 vibrate between the teeth until we no longer hear it, its tones may still be heard on bringing it near 
 the ear (Rinne). The conduction through the bones is favored when the oscillations are not trans- 
 ferred from the bones to the tympanic membrane, and are thus transferred to the air in the outer ear. 
 Hence, we hear the sound of the tuning-fork applied to the head better when the ears are stopped, 
 as this prevents the propagation of the sound waves through the air in the outer ear. If, in a deaf 
 person, the conduction is still normal through the cranial bones, then the cause of the deafness is 
 not in the nervous part of the ear, but in the external sound-conducting part of the apparatus. 
 
 2. Normal hearing takes place through the external auditory meatus. 
 The enormous vibrations of the air first set the tympanic membrane in vibration 
 (Fig. 510, T) ; this moves the malleus {h), whose long process is inserted into it ; 
 the malleus moves the incus (a), and this the stapes (s), which transfers the move- 
 ments of its plate to the perilymph of the labyrinth. 
 
 3. Direct Conduction to the Fenestra. — In man, in consequence of occasional disease of the 
 middle ear, whereby the tympanic membrane and auditory ossicles may be destroyed, the auditory 
 apparatus may be excited, although only in a very feeble manner, by the vibrations of the air being 
 directly transferred to the membrane of the fenestra rotunda (r), and theparts closing the fenestra 
 ovalis (0). The membrane of the fenestra rotunda may vibrate alone, even when the oval window 
 is rigidly closed ( Weber-Liel). 
 
 407. PHYSICAL INTRODUCTION.— Sound.— Sound is produced by the vibration of 
 elastic bodies capable of vibration. Alternate condensation and rarefaction of the surrounding 
 air are thus produced ; or, in other words, sound waves in which the particles vibrate longitudinally 
 or in the direction of the propagation of the sound are excited. Around the point of origin of the 
 sound these condensations and rarefactions occur in equal concentric circles, which conduct the sound 
 vibrations to our outer ear. The vibrations of the sounding body are so called " stationary vibra- 
 tions" (E. H. and IV. Weber), ie., all the particles of the vibrating body are always in the same 
 phase of movement, in that they pass into movement simultaneously, they reach the maximum of 
 movement simultaneously, e.g., in the particles of a sounding vibrating metal rod. Sound is pro- 
 duced by the stationary vibrations of elastic bodies ; it is propagated by progressive wave motion 
 of elastic media, generally the air. The wave length of a tone, i.e., the distance of one maximum 
 of condensation to the next one in the air, is proportional to the duration of the vibration of the 
 body, whose vibrations produce the sound waves. 
 
 If i. is the wave length of a tone, / in seconds the duration of a vibration of the body producing 
 the wave, then A = n t, where n = 340.88 metres, which is ihe rate per second of propagation of 
 sound waves in the air. The rapidity of the transmission of sound waves in water = 1435 metres per 
 second, i.e., nearly four times as rapid as in air ; while in solids capable of vibration it is propagated 
 from seven to eighteen times faster than in the air. Sound waves are conducted best through the 
 same medium ; when they have to pass through several media they are always weakened. 
 
 Reflection of the sound waves occurs when they impinge upon a solid obstacle, in which case 
 the angle of reflection is always equal to the angle of incidence. 
 
 Wave Movements. — We distinguish — I. Progressive wave movements which occur in two 
 forms — (1) As longitudinal waves (Cfiladni), in which the individual particles of the vibrating body 
 vibrate around their centre of gravity in the direction of the propagation of the wave; examples are 
 the waves in water and air. This movement causes an accumulation of the particles at certain places, 
 e.g., on the crests of the waves in water waves,, while at other places they are diminished. This 
 kind of wave is called a wave of condensation and rarefaction. (2) If, however, each particle 
 in the progressive wave moves vertically up and down, i.e., transversely to the direction of the pro- 
 pagation of the wave, then we have the simple transverse waves (CAladni), or progressive waves, in 
 
816 
 
 TYMPANIC MEMBRANE. 
 
 Fig. 511. 
 
 which there is no condensation or rarefaction in the direction of propagation, as each particle is 
 merely displaced laterally. An example of this is the progressive waves in a rope. 
 
 II. Stationary Flexion Waves. — When all the particles of an elastic vibrating body so oscil- 
 late that all of them are always in the same phase of movement as the limbs of a vibrating tuning- 
 fork or a plucked string, then this kind of movement is described as stationary flexion waves. As 
 •bodies, whose expansion in the direction of oscillation is very slight, vibrate to and fro in the station- 
 ary flexion wave, so we see that the small parts of the auditory apparatus (tympanic membrane, os- 
 sicles, lymph of the labyrinth) oscillate in stationary flexion waves. 
 
 408. EAR MUSCLES— EXTERNAL AUDITORY MEATUS.— External Ear.— 
 
 When the external ear is absent, little or no impairment of the hearing is observed ; hence, the 
 physiological functions of these organs are but slight. Boerhaave thought that the elevations and 
 depressions of the outer ear might be connected with the reflection of the sound waves. Numerous 
 sound waves, however, must be again reflected outward ; and those waves which reach the deep 
 part of the concha are said to be reflected toward the tragus, to be reflected by it into the external 
 auditory meatus. According to Schneider, when the depressions in the ear are filled up with wax, 
 hearing is impaired. Mach points out that the dimensions of the external ear are proportionally too 
 small to act as reflecting organs for the wave lengths of noises. 
 
 Muscles of the External Ear. — (1) The whole ear is moved by the retrahenter, attrahens, 
 
 and attollens. (2) The form of the ear may be altered 
 by the tragicus, antitragicus, helicis major and minor 
 internally ; and by the transversus and obliquus auricula; 
 externally. Persons who can move their ears do not 
 find that the hearing is influenced during the movement. 
 The Mm. helicis major and minor are regarded as ele- 
 vators of the helix, the transversus and obliquus auric- 
 ulae as dilators of the concha ; the tragicus and anti- 
 tragicus as constrictors of the meatus. In animals the 
 external ear and the action of its muscles have a marked 
 effect upon hearing. The muscles point the ear in the 
 direction of the sound, while other muscles contract or 
 dilate the space within the external ear. In many div- 
 ing animals the meatus can be closed by a kind of 
 valve. 
 
 The external meatus is 3 to 3.25 cm. 
 long [1^5 to 1% inch], 8 to 9 mm. high, and 
 6 to 8 mm. broad at its outer opening (Fig. 
 511). It is the conductor of the sound waves 
 to the tympanic membrane, so that almost all 
 the sound waves first impinge upon its wall, 
 and are then reflected toward the tympanic 
 membrane. To see well down into the 
 meatus, we must pull the auricle upward and 
 backward. Occlusion of the meatus, espe- 
 cially by a plug of inspissated wax (§ 287), of course interferes with the hearing 
 [and when it presses on the membrana tympani may give rise to severe vertigo]. 
 
 409. TYMPANIC MEMBRANE.— The tympanic membrane (Fig. 
 513), which is tolerably laxly fixed in a special osseous cleft, with a thickened 
 margin, is an elastic, unyielding, and almost non-extensible membrane, of about 
 0.1 mm. in thickness, and with a superficial area of 50 square millimetres. It is 
 elliptical in form, its greatest diameter being 9.5 to 10 mm., and its lesser 8 mm., 
 and it is fixed in the floor of the external meatus obliquely, at an angle of 40 , 
 being directed from above and outward, downward and inward. Both tympanic 
 membranes converge anteriorly, so that if both were prolonged they would meet 
 to form an angle of 130 to 135°. The oblique position enables a larger surface 
 to be presented than would be obtained if it were stretched vertically, so that 
 more sound waves can fall vertically upon it. The membrane is not stretched 
 flat, but a little under its centre (umbilicus) it is drawn slightly inward by the 
 handle of the malleus, which is attached to it ; while the short process of the 
 malleus slightly bulges out the membrane near its upper margin (Figs. 510 and 
 
 The external auditory meatus and the tympanic 
 cavity. M, osseous spaces in the temporal 
 bone; Pj, cartilaginous part of the meatus ; 
 L, membranous union between both : F, ar- 
 ticular surface for the condyle of the lower 
 jaw (after Urbantschitsch). 
 
FUNCTIONS OF THE OUTER EAR. 
 
 817 
 
 Structure. — The tympanic membrane consists of three layers: (i) The membrana propria is 
 a fibrous membrane with radial fibres on its outer surface, and circularly arranged fibres on its 
 inner aspect. (2) The surface directed toward the meatus. is covered with a thin and semi-trans- 
 parent part of the cutis. (3) The side toward the tympanum is covered with a delicate mucous 
 membrane, with simple squamous epithelium. Numerous nerves and lymph vessels as well as 
 inner and outer blood vessels occur in the membrane. 
 
 [The middle layer, or substantia propria, is fixed to a ring of bone, which is 
 deficient above. It is filled up by a layer composed of the mucous and cutaneous 
 layers called the membrana flaccida, or Shrapnell's membrane.] 
 
 [Examination. — When examining the outer ear and membrana tympani pull the auricle upward 
 and backward. The membrana tympani is examined by means of an ear speculum (Fig. 515). 
 The speculum is placedin the ear, and light is reflected into it by means of a concave mirror, per- 
 forated in the centre, and having a focal distance of four or five inches. It is convenient to have 
 the mirror fixed to a band placed round the head, as in the case of the laryngoscopic reflector (Fig. 
 327). It is important to remember that the membrane is placed obliquely, so that the posterior and 
 upper parts are nearer the surface. The membrane in health is grayish in color and transparent, 
 
 Fig. 513. 
 
 Fig. 514. 
 
 Fig. 512. — Tympanic membrane with the auditory ossicles (left) seen from within. Ci, incus ; Cm, malleus ; Ch, 
 chorda tympani; T, pouch-like depression (after Urbantschitsch). Kig. 513. — Tympanic membrane and the 
 auditory ossicles (left) seen from within, i. e., from the tympanic cavity. M, manubrium or handle of the mal- 
 leus; T, insertion of the tensor tympani ; h, head; IF, long process of the malleus ; a, incus, with the short (K) 
 and the long (?) process ; S, plate of the stapes; Ax, Ax, is the common axis of rotation of the auditory ossicles; 
 S, the pinion-wheel arrangement between the malleus and incus. Fig. 514. — Tympanic membrane of a new- 
 born child seen from without, with the handle of the malleus visible on it. At, tympanic ring with its anterior 
 (v) and posterior (h) ends. 
 
 so that the handle of the malleus is seen running from above downward and backward, while at the 
 anterior and inferior part there is a cone of light, with its apex directed inward.] 
 
 Function. — The tympanic membrane catches up the sound waves which pene- 
 trate into the external meatus, and is set into vibration by them, the vibrations 
 corresponding in number and amplitude to the vibrating movements of the air. 
 Politzer connected the auditory ossicles fixed to the tympanic membrane of a duck 
 with a recording apparatus, and could thus register the vibrations produced by 
 sounding any particular tone. Owing to its small dimensions, the tympanic mem- 
 brane can vibrate in toto to and fro in the direction of the sound waves corre- 
 sponding to the condensations and rarefactions of the vibrating air, and therefore 
 executes transverse vibrations, for which it is specially adapted, owing to the rela- 
 tively slight resistance. 
 
 Fundamental Note. — Stretched strings and membranes are generally only 
 thrown into actual and considerable sympathetic vibration when they are affected 
 S 2 
 
818 
 
 FUNCTIONS OF THE OUTER EAR. 
 
 by tones which correspond with their own fundamental tone, or whose number of 
 vibrations is some multiple of the number of vibrations of the same, as the octave. 
 When other tones act on them, they exhibit only inconsiderable sympathetic 
 vibration. If a membrane be stretched over a funnel or cylinder, and if a nodule 
 of sealing wax attached to a silk thread be made just to touch the centre of the 
 membrane, then the sealing wax remains nearly at rest when tones or sounds are 
 made in the neighborhood; as soon, however, as the fundamental or proper tone 
 of this arrangement is sounded, the nodule is propelled by the strong vibrations 
 of the membrane. 
 
 If we apply this to the tympanic membrane, then it also should exhibit very 
 great vibrations when its own fundamental note is sounded, but only slight vibra- 
 tions when other tones are produced. This, however, would produce great ine- 
 quality in the audible sounds. There is an arrangement of the membrane whereby 
 this is prevented, (i) Great resistance is offered to the vibrations of the tympanic 
 membrane, owing to its union with the auditory ossicles. These act as a damping 
 apparatus, which provides, as in damped membranes generally, that the tympanic 
 membrane shall not exhibit excessive sympathetic vibrations for its own funda- 
 mental note. But the damping also makes the sympathetic vibrations less for all 
 
 Fig. 515. 
 
 Fig. 516. 
 
 Fig. 517. 
 
 Fig. 515. — Ear specula of various sizes. Fig. 516. — Toynbee's artificial membrana tympani. Fig. 517. — The audi- 
 tory ossicles (right). Cm, head; C, neck; Pbr, snort process ; Prl, long process ; M, handle of the malleus ; 
 Ci', body ; G, articular surface ; h, short, and v, long process of the incus ; O.S., so-called lenticular ossicle ; 
 C.s. , head ; a, anterior, and/, posterior limb ; P, plate of the stapes. 
 
 the other tones. In this way, all vibrations of the tympanic membrane are modi- 
 fied ; especially, however, is the excessive vibration diminished during the sounding 
 of its fundamental tone. The membrane is at the same time rendered more capable 
 of responding to the vibrations of different wave lengths. The damping also 
 prevents after vibrations; (2) Corresponding to the small mass of the tympanic 
 membrane, its sympathetic vibrations must also be small. Nevertheless, these 
 slight elongations are quite sufficient to convey the sonorous movements to the 
 most delicate end organs of the auditory nerve ; in fact, there are arrangements 
 in the tympanum which still further diminish the vibrations of the tympanic 
 membrane. 
 
 As v. Helmholtz has shown, the strong sympathetic vibrations of the tympanic membrane are not 
 completely set aside by this damping arrangement. The painful sensations produced by some tones 
 are, perhaps, due to the sympathetic vibration of the membrana tympani. According to Kessel, 
 certain parts of the membrane vibrate to certain tones. 
 
 Pathological. — Thickenings or inequalities of the tympanic membrane interfere with the acute- 
 ness of hearing, owing to the diminished capacity for vibration thereby produced. Holes in and 
 loss of its substance act similarly. In extensive destruction, an artificial tympanum is placed in the 
 external meatus, and its vibrations, to a certain extent, replace those of the lost membrane ( Toyn- 
 dee). [Fig. 516 shows an ".rtificial tympanic membrane.] 
 
MECHANISM OF THE AUDITORY OSSICLES. 819 
 
 410. THE AUDITORY OSSICLES AND THEIR MUSCLES. 
 
 — Function. — The auditory ossicles have a double function — (1) By means of 
 the " chain " which they form, they transfer the vibrations of the tympanic mem- 
 brane to the perilymph of the labyrinth. (2) They also afford points of attach- 
 ment for the muscles of the middle ear, which can alter the tension of the mem- 
 brana tympani and the pressure on the lymph of the labyrinth. 
 
 Mechanism. — The form and position of the ossicles are given in Figures 517 
 and 5 18. They form a jointed chain which connects the tympanic membrane, M, 
 by means of the malleus, h, incus, a, and stapes, S, with the perilymph of the 
 labyrinth. The mode of movement of the ossicles is of special importance. 
 The handle of the malleus (Fig. 518, n) is firmly united to the fibres of the tym- 
 panic membrane. Besides this, the malleus is fixed by ligaments which prescribe 
 the direction of its movements. Two ligaments — the lig. mallei anticum (passing 
 from the processus Folianus), and the posticum (from a small crest on the neck) — 
 
 Tympanum and auditory ossicles (left) magnified. A.G, external meatus ; M, membrana tympani, which is attached 
 to the handle of the malleus, «, and near it the short process,/ ; h, head of the malleus ; a, incus ; k, its short 
 process with its ligament ; /, long process ; x. Sylvian ossicle ; S, stapes ; Ax, Ax, is the axis of rotation of the 
 ossicles, it is shown in perspective, and must be imagined to penetrate the plane of the paper ; t, line of traction 
 of the tensor tympani. The other arrows indicate the movement of the ossicles when the tensor contracts, 
 
 together form a common axial band (v. Helmholtz), which acts in the direction 
 from behind forward, i.e., parallel to the surface of the tympanic membrane. 
 The neck of the malleus lies between the insertions of both ligaments. The united 
 ligament determines the " axis of rotation " of the movement of the malleus. 
 
 When the handle of the malleus is drawn inward, of course its head moves in 
 the opposite direction, or outward. The incus, a, is only partially fixed by a 
 ligament, which attaches its short process to the wall of the tympanic cavity, in 
 front of the entrance to the mastoid cells, k. The not very tense articulation 
 joining it to the head of the malleus, h, which lies with its saddle-shaped articular 
 surface in the hollow of the incus, is important. The lower margin of the incus 
 (Fig. 517, S) acts like a tooth of a cog-wheel. Thus, when the handle of the 
 malleus moves inward to the tympanic cavity, the incus, and its long process, b, 
 which is parallel to the handle of the malleus, also pass inward'. The incus forms 
 almost a right angle with the stapes, S, through the intervention of the Sylvian 
 
820 MODE OF VIBRATION OF THE OSSICLES. 
 
 ossicle, s. If, however, as by condensation of the air in the tympanum, the 
 membrana tympani and the handle of the malleus move outward, the long pro- 
 cess of the incus does not make a similar movement, as the malleus moves away 
 from this margin of the incus. Hence the stapes is not liable to be torn from its 
 socket. The malleus and incus form an angular lever, which moves round a 
 common axis (Fig. 513 and Fig. 518, Ax, Ax). In the inward movement the 
 malleus follows the incus, as if both formed one piece. The common axis (Fig. 
 513) is not, however, the axial ligament of the malleus, but it is formed anteriorly 
 by the processus Folianus, IF, directed forward, and posteriorly by the short pro- 
 cess of the incus directed backward. The rotation of both ossicles around this 
 axis occurs in a plane vertical to the plane of the membrana tympani. During 
 the rotation, of course the parts above this axis (head of the malleus and upper 
 part of the body of the incus) take a direction opposite to the parts lying below 
 it (the handle of the malleus and the long process of the incus), as is indicated 
 in Fig. 518 by the direction of the arrows. The movement of the handle of the 
 malleus must follow that of the membrana tympani, and vice versd, while the 
 movement of the stapes is connected with the movement of the long process of 
 the incus. As the long process of the incus is only two-thirds of the length of 
 the handle of the malleus (Figs. 510, 513, 518), of course the excursion of the 
 tip of the former, and with it of the stapes, must be correspondingly less than the 
 movement of the tip of the handle of the malleus ; while, on the other hand, the 
 force of the movement of the tip of the handle of the malleus, corresponding to 
 the diminution of the excursion, will be increased. 
 
 Mode of Vibration. — Thus, the movement of the membrana tympani inward 
 causes a less extensive but a more powerful movement of the foot of the stapes 
 against the perilymph of the labyrinth. V. Helmholtz and Politzer calculated 
 the extent of the, movement to be 0.07 mm. The mode in which the vibrations 
 of the membrana tympani are conveyed to the lymph of the labyrinth, through 
 the chain of ossicles, is quite analogous to the mechanism of these parts already 
 .described. Long delicate glass threads have been fixed to these ossicles, and their 
 movements were thus graphically recorded on a smoked surface {Politzer, Hen- 
 sen). Or strongly refractive particles are fixed to the ossicles, while the beam of 
 light reflected from them can be examined by means of a microscope {Buck, v. 
 Helmholtz, Mach and Kessel). All the experiments showed that the transference 
 of the sound waves is accomplished by means of the mechanism of the angular 
 lever, composed of the auditory ossicles already described. As the vibrations 
 of the membrana tympani are conveyed to the handle of the malleus, they are 
 weakened to about one-fourth of their original strength {Politzer, Buck). [The 
 membrana tympani is many times (30) larger than the fenestra ovalis, and the 
 relation in size might be represented by a funnel. The arm of the malleal end 
 of the lever where the power acts is 9^ mm. long, while the short or stapedial 
 arm is 6yi mm., so that the latter moves less than the former, but what is lost in 
 extent is gained in force.] 
 
 [Methods. — Politzer attached small, very light levers to each of the ossicles, and inscribed their 
 movements on a revolving cylinder. An organ pipe was sounded, and when the levers were of the 
 same length, the malleus made the greatest excursion and the stapes the least. Buck attached starch 
 grains to the ossicles, illuminated them, and observed the movements of the refractive starch 
 granules by means of a microscope provided with a micrometer.] 
 
 [The ossicles move en masse, and not in the way of propagating molecular 
 vibrations.] As the excursions of the ossicles during sonorous vibrations are, how- 
 ever, only nominal, there is practically no change in the position of the joints 
 with each vibration. The latter will only occur when extensive movements take 
 place by means of the muscles. 
 
 The muscles of- the auditory ossicles alter the position and tension of the 
 membrana tympani, as well as the pressure of the lymph of the labyrinth. The 
 
CONTRACTION OF THE TENSOR. 821 
 
 tensor tympani, which lies in an osseous groove Fig. 519. 
 
 above the Eustachian tube, has its tendon deflected 
 round an osseous projection [processus cochleari- 
 formis], which lies external to it, almost at right 
 angles to the groove above it, and is inserted im- 
 mediately above the axes of the malleus (Fig. 519, 
 M). When the muscle contracts in the direction 
 of the arrow, /(Fig. 518), then the handle of the 
 malleus («) pulls the membrana tympani (M) in- 
 ward and tightens it. This also causes a move- 
 ment of the incus and stapes (S) which must be 
 pressed more deeply into the fenestra ovalis, as al- 
 ready described. When the muscle relaxes, then, 
 owing to the elasticity of the rotated axial ligament Tensor tympani _ the Eustachian tube (left), 
 and the tense membrana tympani itself, the posi- 
 tion of equilibrium is again restored. The motor nerve of this muscle arises 
 from the trigeminus, and passes through the otic ganglion (p. 628). C. Ludwig 
 and Politzer observed that stimulation of the fifth nerve within the cranium [dog] 
 caused the above-mentioned movement. 
 
 Use of the Tension. — The tension of the membrana tympani caused by the 
 tensor tympani has a double function {Joh. Milller). — 1. The tense membrane 
 offers very great resistance to sympathetic vibrations when the sound waves are 
 very intense, as it is a physical fact (Savart) that stretched membranes are more 
 difficult to throw into sympathetic vibration the tenser they are. Thus, the tension 
 so far protects the auditory organ, as it prevents too intense vibrations applied to 
 the membrana tympani from reaching the terminations of the nerves. 2. The tension 
 of the membrana tympani must vary according to the degree of contraction of the 
 tensor. Hereby the membrana for the time being has a different fundamental 
 tone, and is thus capable of vibrating to the correspondingly higher tone, it, as it 
 were, being in a certain sense accommodated. 
 
 Comparison with Iris. — The membrana tympani has been compared with the iris. Both mem- 
 branes prevent by contraction — narrowing of the pupil and tension of the membrana tympani — the 
 too intense action of the specific stimulus from causing too great stimulation, and both adapt the 
 sensory apparatus for the action of moderate or weak stimuli. This movement in both membranes 
 is brought about reflexly in the ear through the N. acusticus, which causes a reflex stimulation of 
 the motor fibres for the tensor tympani. 
 
 Effect of Tension. — That increased tension of the membrana tympani renders it less 
 sensitive to sound waves is easily proved, thus : Close the mouth and nose, and make either a 
 forced expiration, so that the air is forced into the Eustachian tube, which bulges out the 
 membrana tympani, or inspire forcibly, whereby the air in the tympanum is diminished, so 
 that the membrana bulges inward. In both cases hearing is interfered with as long as the 
 increased tension lasts. If a funnel with a small lateral opening, and whose wide end is 
 covered by a membrane, be placed in the external meatus, hearing becomes less distinct when 
 the membrane is stretched {Joh. Miiller). 
 
 Normally, the tensor tympani is excited reflexly. The muscle is not directly and by itself subject 
 to the control of the will. According to L. Fick, the following phenomenon is due to an " associ- 
 ated movement" of the tensor : When he pressed his jaws firmly against each other he heard in 
 his ear a piping, singing tone, while a capillary tube, which was fixed air tight into the meatus, had 
 a drop of water which was in it rapidly drawn inward. During this experiment, a person with 
 normal hearing hears all musical tones as if they were louder, while all the highest non-musical 
 tones are enfeebled (Lucae). When yawning, v. Helmholtz and Politzer found that hearing was 
 enfeebled for certain tones. 
 
 Contraction of the Tensor. — Hensen showed that the contraction of the 
 tensor tympani during hearing is not a continued contraction, but what might be 
 termed a " twitch." A twitch takes place at the beginning of the act of hearing, 
 which favors the perception of the sound, as the membrana tympani thus set in 
 motion vibrates more readily to higher tones than when it is at rest. On expos- 
 ing the tympanum in cats and dogs, it was found that this contraction or twitch 
 
822 THE EUSTACHIAN TUBE. 
 
 occurs only at the beginning of the sound, and that it soon ceases, although the 
 
 sound may continue. 
 
 Action of the Stapedius. — This muscle arises within the 
 Fig. 520. eminentia pyramidalis, and is inserted into the head of the 
 stapes and Sylvian ossicle (Fig. 520) ; when it draws upon the 
 head of the stapes, as indicated in Fig. 510, by the small curved 
 arrow, it must place the bone obliquely, whereby the posterior 
 end of the plate of the stapes is pressed somewhat deeper in- 
 ward into the fenestra ovalis, while the anterior is, as it were, 
 displaced somewhat outward. The stapes is thereby more fixed, 
 as the fibrous mass [annular ligament] which surrounds the fe- 
 nestra ovalis and keeps the stapes in its place becomes more tense. 
 
 Right stapedius muscle. The activity of this muscle, therefore, prevents too intense 
 shocks, which may be communicated from the incus to the stapes, 
 
 from being conveyed to the perilymph (§ 808, 5). It is supplied by the facial 
 
 nerve (§ 349, 3). 
 
 The stapedius in many persons executes an associated movement when the eyelids are forcibly 
 closed (g 349). Some persons can cause it to contract reflexly by scratching the skin in front of the 
 meatus, or by gently stroking the outer margin of the orbit (Henle). 
 
 Other Views. — According to Lucae, when the stapes is displaced obliquely, its head forces the 
 long process of the incus, and also the membrana tympani, outward, so that it is regarded as an 
 antagonist of the tensor tympani. Politzer observed that the pressure within the labyrinth fell 
 when he stimulated the muscle. According to Toynbee, the stapedius acts as a lever and moves 
 the stapes slightly out of the fenestra ovalis, thus making it more free to move, so that it is more 
 capable of vibrating. Henle supposes that the stapedius is more concerned m Jixing than in moving 
 the stapes, and that it comes into action when there is danger of too great movement being commu- 
 nicated to the stapes from the incus. Landois agrees with this opinion, and compares the stapedius 
 with the orbicularis palpebrarum, both being protective muscles. 
 
 Pathological.— Immobility of the auditory ossicles, either by adhesions or anchyloses, causing 
 diminished vibrations, interferes with hearing ; while the same result occurs when the stapes is 
 firmly anchylosed into the fenestra ovalis. The tendon of the tensor tympani has been divided in 
 cases of contracture of the muscles. For paralysis of the tensor, see p. 629, and for the stapedius, 
 P- 634. 
 
 411. EUSTACHIAN TUBE— TYMPANUM.— The Eustachian tube 
 
 [4 centimetres in length, z.S/% in.] is the ventilating tube 'of the tympanic cavity. 
 It keeps the tension of the air within the tympanum the same as that within the 
 pharynx and outer air (Figs. 510, 519). Only when the tension of the air is the 
 same outside and inside the tympanum is the normal vibration of the membrana 
 tympani possible. The tube is generally closed, as the surfaces of the mucous 
 membrane lining it come into apposition. During swallowing, however, the 
 tube is opened, owing to the traction of the fibres of the tensor veli palatini 
 [spheno-salpingo-staphylinus sive abductor tubae {v. Troltscfa, sive dilator tubae 
 (Rudinger)~\ inserted into the membrano-cartilaginous part of the tube {Toynbee, 
 Politzer, Moos). (Compare § 139, 2.) When the tube is closed the vibrations of 
 the membrana tympani are transferred in a more undiminished condition to 
 the auditory ossicles than when it is open, whereby part of the vibrating air is 
 forced through the tube (Mach and Kessef). If, however, the tympanic cavity is 
 closed permanently, the air within it becomes so rarefied (§ 139) that the mem- 
 brana tympani, owing to the abnormally low tension, becomes drawn inward, 
 thus causing difficulty of hearing. As the tube is lined by ciliated epithelium 
 (p. 491), it carries outward to the pharynx the secretions of the tympanum. 
 
 Noise in the Tube. — A sharp hissing noise is heard in the tube during swallowing, when we 
 swallow slowly and at the same time contract the tensor tympani, due to the separation of the 
 adhesive surfaces of its lining membrane. Another person may hear this noise by using a stetho- 
 scope or his ear. 
 
 In Valsalva's experiment (\ 60), as soon as the pressure of the air reaches 10 to 40 mm. Hg 
 air enters the tube. The sound is heard first, and then we feel the increased tension of the tympanic 
 membrane, owing to the entrance of air into the tympanum. During forced inspiration, when the 
 nose and mouth are closed, air is sucked out, while the tympanum is ultimately drawn inward. 
 
RELATIONS OF THE TYMPANUM. 
 
 823 
 
 The M. levator veli palatini, as it passes under the base of the opening of the tube into the 
 pharynx, forms the levator eminence or cushion (Fig. 332, W). Hence, when this muscle contracts 
 and its belly thickens, as at the commencement of the act of deglutition and during phonation, the 
 lower wall of the pharyngeal opening is raised, and the opening thereby narrowed (Lucae). The 
 contraction of the tensor, occurring during the latter part of the act of deglutition, dilates the tube. 
 
 Other Views. — According to Riidinger, the tube is always open, although only by a very narrow 
 passage in the upper part of the canal, while the canal is dilated during swallowing. According to 
 Cleland, the tube is generally open, and is closed during swallowing. 
 
 [Practical Importance. — The tympanic cavity forms an osseous box, and, 
 therefore, a protective organ for the auditory ossicles and their muscles, while the 
 increased air space, obtained by its communication with the mastoid cells, permits 
 free vibration of the membrana tympani. The six sides of the tympanum have 
 important practical relations. It is about half an inch in height, and one or two 
 lines in breadth, i. <?., from without inward. Its roof is separated from the cavity 
 of the brain by a very thin piece of bone, which is sometimes defective, so that 
 encephalitis may follow an abscess of the middle ear. The outer wall is formed 
 by the membrana tympani, while on the inner wall are the fenestra ovalis and 
 rotunda, the ridge of the aqueductus Fallopii, the promontory and the pyramid. 
 
 Fig. 521. 
 
 Fio. 522. 
 
 Folitzer's ear bag. 
 
 Eustachian catheter. 
 
 The floor consists of a thin plate of bone, which roofs in the jugular fossa and 
 separates it from the jugular vein. Fractures of the base of the skull may rupture 
 the carotid artery or internal jugular vein ; hence hemorrhage from the ears is a 
 bad symptom in these cases. Caries of the ear may extend to other organs. The 
 anterior wall is in close relation with the carotid artery, while the posterior com- 
 municates with the mastoid cells, so that fluids from the middle ear sometimes 
 escape through the mastoid cells.] 
 
 That the air in the tympanum can communicate its vibrations to the membrane of the fenestra 
 rotunda is true (p. 814), but normally this is so slight, when compared with the conduction through 
 the auditory ossicles, that it scarcely need be taken into account. 
 
 Structure. — The tube and tympanum are lined by a common mucous membrane, covered by 
 ciliated epithelium, while the membrana is lined by a layer of squamous epithelium. Mucous 
 glands were found by Troltsch and Wendt in the mucous membrane. [The epithelium covering the 
 ossicles and tensor tympani is not ciliated.] 
 
 Pathological. — The tube is often occluded, owing to chronic catarrh and narrowing from cica- 
 trices, hypertrophy of the mucous membrane, or the presence of tumors. The deafness thereby 
 produced may often be cured by catheterizing the tube from the nose (Fig. 521 ). Effusions into or 
 suppuration within the tympanum, of course, paralyze the sound-conducting mechanism, while in- 
 flammation often causes subsequent affections of the plexus tympanicus. If the temporal bone be 
 
824 METHOD OF TESTING SOUND CONDUCTION. 
 
 destroyed by progressive caries within the tympanum, inflammation of the neighboring cerebral 
 structures may occur and cause death. 
 
 [Methods. — Not unfrequcntly the aurist is called upon to dilate the Eustachian tube, which, in 
 certain cases, requires the use of a Eustachian catheter introduced into the tube along the floor 
 of the nose (Fig. 521). At other times he requires to fill the tympanic cavity with air, which is 
 easily done by means of a Politzer's bag (Fig. 522). The nozzle is introduced into one nostril, 
 while the other nostril is closed, and the patient is directed to swallow, while at the same moment 
 the surgeon compresses the bag, and the patient's mouth being closed, air is forced through the open 
 Eustachian tube into the middle ear. Sometimes a small, curved, narrow manometer, containing a 
 drop of colored water, is placed in the outer ear {Politzer). Normally, when the patient swallows, 
 the fluid ought to move in the tube.] 
 
 412. CONDUCTION OF SOUND IN THE LABYRINTH.— The 
 
 vibrations of the foot of the stapes in the fenestra ovalis give rise to waves in the 
 perilymph within the inner ear or labyrinth. These waves 
 are so-called "flexion waves," i. e., the perilymph moves in 
 mass before the impulse of the base of the stapes. This is 
 only possible from the existence of a yielding membrane — 
 that filling the fenestra rotunda, and sometimes called the 
 membrana secundaria, which during rest bulges inward to the 
 scala tympani, and can be bulged outward toward the tym- 
 panic cavity by the impulse communicated to it by the move- 
 ment of the perilymph (Fig. 510, r). The flexion waves 
 ^""fabyn'nthYfenestra must correspond in number and intensity to the vibrations of 
 ovaiis, cochlea to the the auditory ossicles, and must also excite the free termina- 
 te)' horizontal, "anS P (I) tions of the auditory nerve, which float free in the endolymph. 
 canai1°eft). semicircular As the endolymph of the saccule and utricle lying in the 
 ■vestibule receive the first impulse, and as they communicate 
 anteriorly with the cochlea, and posteriorly with the semicircular canals, conse- 
 quently the motion of the perilymph must be propagated through these canals. 
 To reach the cochlea the movement passes from the saccule (lying in the fovea 
 hemispherica) along the scala vestibuli to the helicotrema, where it passes into the 
 scala tympani, where it reaches the membrane of the fenestra rotunda, and causes 
 it to bulge outward. From the utricle (lying in the fovea hemielliptica), in a 
 similar manner, the movement is propagated through the semicircular canals. 
 Politzer observed that the endolymph in the superior semicircular canal rose when 
 he caused contraction of the tensor tympani by stimulating the trigeminus, just as 
 the base of the stapes must be forced against the perilymph with every vibration 
 of the membrani tympani. 
 
 [Practical. — It is well to view the organ of hearing as consisting of two mech- 
 anisms : — 
 
 1. The sound-conducting apparatus. 
 
 2. The sound-perceiving apparatus. 
 
 The former includes the outer ear, with its auricle and external meatus ; the 
 ■middle ear and the parts which bound it, or open into it. The latter consists of 
 the inner ear with the expansion of the auditory nerve in the labyrinth, the nerve 
 itself, and the sound-perceiving and interpreting centre or centres in the brain 
 
 (P- 723)-] 
 
 [Testing the Sound Conduction. — In any case of deafness it is essential to 
 estimate the degree of deafness by the methods stated at p. 815, and it is well to 
 do so both for such sounds as those of a watch and conversation. We have next 
 to determine whether the sound-conducting or the sound-perceiving apparatus is 
 affected. If a person is deaf to sounds transmitted through the air, on applying 
 a sounding tuning-fork to the middle line of the head or teeth, and if it be heard 
 distinctly, then the sound-perceiving apparatus is intact, and we have to look for 
 the cause of deafness in the outer or middle ear. In a healthy person, the sound 
 of the tuning-fork is heard of equal intensity in both ears. In this case the sound 
 is conducted directly to the labyrinth by the cranial bones. In cases of disease 
 
STRUCTURE OF THE LABYRINTH. 
 
 825 
 
 of the sound-conducting mechanism, the sound of the tuning-fork is heard loudest 
 in the deafer ear. Ed. Weber pointed out that, if one ear be stopped and a 
 vibrating tuning-fork placed on the head, the sound is referred to the plugged 
 ear, where it is heard loudest. It is assumed that when the ear is plugged, the 
 sound waves transmitted by the cranial bones are prevented from escaping {Mach). 
 If, on the contrary, the sound be heard loudest in the good ear, then in all proba- 
 bility there is some affection of the sound-perceiving apparatus or labyrinth, 
 although there are exceptions to this statement, especially in elderly people. 
 Another plan is to connect two telephones with an induction machine, provided 
 with a vibrating Neef 's hammer. The sounds of the vibrations of the latter are 
 reproduced in the telephones, and if they be placed to the ears, then the healthy 
 ears hear only one sound, which is referred to the middle line, and usually to the 
 back of the head. In diseased conditions this is altered— it is referred to one 
 side or the other.] 
 
 413. STRUCTURE OF THE LABYRINTH, AND TERMINATION OF THE 
 AUDITORY NERVE.— Scheme. — The vestibule (Fig. 524, III) contains two separate sacks, 
 one of them the saccule, s (round sack or S. hemisphasricus), communicates with the ductus 
 
 Fig. 524. 
 
 I, transverse section of a turn of the cochlea ; II, A, ampulla of a semicircular canal with the crista acustica ; a,p, 
 auditory cells ; p, provided with a fine hair ; T, otoliths ; III, scheme of the human labyrinth ; IV, scheme of 
 a bird's labyrinth ; V, scheme of a fish's labyrinth. 
 
 cochlearis, C c, of the cochlea, the other the utricle, U (elliptical sack, or sacculus hemiellipticus), 
 communicates with the semicircular canals, Cj,Cj. 
 
 The cochlea consists of 2,y z turns of a tube disposed round a central column or modiolus. The 
 tube is divided into two compartments (Fig. 527, Fig. 524, I) by a horizontal septum, partly osse- 
 ous and partly membranous, the lamina spiralis ossea and membranacea. The lowet compart- 
 ment is the scala tympani, and is separated from the cavity of the tympanum by the membrane of 
 the fenestra rotunda. 
 
 The upper compartment is the scala vestibuli, which communicates with the vestibule of the 
 labyrinth (Fig. 524, I). These two compartments communicate directly by a small opening at the 
 apex of the cochlea, a sickle-shaped edge ["hamulus "] of the lamina spiralis bounding the heli- 
 cotrema (Fig. 510). The scala vestibuli is divided by Reissner's membrane (Fig. 524, 1), 
 which arises near the outer part of the lamina spiralis ossea, and runs obliquely outward to the wall 
 of the cochlea so as to cut off a small triangular canal, the ductus or canalis cochlearis, or scala 
 media, C c, whose floor is formed for the most part by the lamina spiralis membranacea, and on 
 which the end organ of the auditory nerve — Corti's organ— is placed. The lower end of the can- 
 alis cochlearis is blind, III, and divided toward the saccule, with which it communicates by means 
 of the small canalis reuniens, C r (Hensen). The utricle (Fig. 524, III, U) communicates with 
 the three semicircular canals, C s, C j — each by means of an ampulla, within which lies the termi- 
 nations of the ampullary nerves, but as the posterior and the superior canals unite there is only one 
 
826 
 
 MACULE ACUSTICA AND COCHLEA. 
 
 common ampulla for them. The membranous semicircular canals lie within the osseous canals, 
 perilymph lying between the two. Perilymph also fills the scala vestibuli and tympani, so that all 
 the spaces within the labyrinth are filled by fluid, while the spaces themselves are lined by short 
 cylindrical epithelium. 
 
 The system of spaces, filled by endolymph, is the only part containing the nervous end organs 
 for hearing. All these spaces communicate with each other ; the semicircular canals directly with 
 the utricle, the ductus cochlearis with the saccule through thecanalis reuniens; and, lastly, the sac 
 cule and utricle through the " saccus endolymphaticus," which springs by an isolated limb from 
 each sack ; the limbs then unite, as in the letter Y ; and pass through-the osseous aqueductus vestibuli 
 to end blindly in the dura mater of the brain (Fig. Ill, K—BSttcAer, Returns). The aqueductus 
 cochleae is another narrow passage, which begins in the scala tympani, immediately in front of the 
 fenestra rotunda, and opens close to the fossa jugularis. It forms a direct means of communication 
 between the perilymph of the cochlea arid the subarachnoid space. 
 
 Semicircular Canals and Vestibular Sacks — The membranous semicircular canals do not fill 
 the corresponding osseous canals completely, but are separated from them by a pretty wide space, 
 which is filled with perilymph (Fig. 525). At the concave margin they are fixed by connective tis- 
 sue to the osseous walls. The ampullae, however, completely fill the corresponding osseous dilata- 
 tions. The canals and ampullae consist externally of an outer, vascular, connective-tissue layer, on 
 which there rests a well-marked hyaline layer, bearing a single layer of flattened epithelium. 
 
 Crista Acustica. — The vestibular branch of the auditory nerve sends a branch to each ampulla 
 and to the saccule and utricle (Fig. 526). In the ampulla (Fig. 524, II, A), the nerve (c) termi- 
 
 Fig. 525. 
 
 The interior of the right labyrinth with its membranous canals and nerves. In Fig. 525, A, the outer wall of the bony 
 labyrinth is removed to show the membranous parts within — 1, commencement of the spiral tube of the cochlea ; 
 2, posterior semicircular canal, partly opened ; 3, horizontal ; 4, superior canal ; 5, utricle ; 6, saccule ; 7, lamina 
 spiralis; 7', scala tympani; 8, ampulla of the superior membranous canal; 9, of the horizontal; to, of the 
 posterior canal. Fig. 526 shows the membranous labyrinth and nerves detached — 1, facial nerve in the internal 
 auditory meatus ; 2, anterior division of the auditory nerve giving branches to 5, 8, and 9, the utricle and the 
 ampullae of the superior and horizontal canals ; 3, posterior division of the auditory nerve, giving branches to 
 the saccule, 6, and posterior ampulla, 10, and cochlea, 4 ; 7, united part of the posterior and superior canals ; 
 11, posterior extremity of the horizontal canal. 
 
 nates in connection with the crista acustica, which is a yellow elevation projecting into the equa- 
 tor of the ampulla. The medullated nerve fibres, n, form a plexus in the connective-tissue layer, 
 lose their myelin as they pass to the hyaline basement membrane, and each ends in a cell provided 
 with a rigid hair (o,p) 90 fi in length, so that the crista is largely covered with these hair cells 
 (Hartmann), but between them are supporting cells like cylindrical epithelium {a), and not unfre- 
 quently containing granules of yellow pigment. The hairs or " auditory hairs " (M. Schultze) are 
 composed of many fine fibres (Retzitis). An excessively fine membrane (membrana tectoria) 
 covers the hairs (Pritchard, Lang). 
 
 Maculae Acusticae. — The nerve terminations in the maculae acusticae of the saccule and 
 utricle are exactly the same as in the ampullae, only the free surface of their membrana tectoria is 
 sprinkled with small, white, chalk-like crystals or otoliths (II, T), composed of calcic carbonate, 
 which are sometimes amorphous and partly in the form of arragonite, lying fixed in the viscid endo- 
 lymph. The non-medullated axis cylinders of the saccular nerves enter directly into the substance 
 of the hair cells. The terminations of the nerves have been investigated, chiefly in fishes, in the 
 rays. 
 
 Cochlea.— The terminations of the cochlear branch of the auditory nerve lie in connection with 
 Corti's organ, which is placed in the canalis or ductus cochlearis (Fig. 524, I, C c, and III, C <-, 
 and Fig. 527), the small triangular chamber or [scala media], cut off from the scala vestibuli by 
 the membrane of Reissner. Corti's organ is placed on the lamina spiralis membranacea, and con- 
 sists of a supporting apparatus composed of the so-called Corti's arches, each of which consists 
 of two Corti's rods (2,/), which lie upon each other like the beams of a house. But every two 
 
INTRA-LABYRINTHINE PRESSURE. 
 
 827 
 
 rods do not form an arch, as there are always three inner to two outer rods [Claudius). There are 
 about 4500 outer rods ( Waldeyer). 
 
 The ductus cochlearis becomes larger toward the apex of the cochlea, and the rods also become 
 longer; the inner ones are 30 fi long in the first turn, and 34 ft in the upper, the outer rods 47 ,u 
 and 69 11 respectively. The span of the arches also increases (Hensen). [The arches leave a 
 triangular tunnel beneath them.] The proper end organs of the cochlear nerve are the cylindrical 
 " hair cells " (Kolliker) previously observed by Corti, which are from 16,400 to 20,000 in number 
 (Hensen, Waldeyer). There is one row of inner cells (i) which rests on a layer of small granular 
 cells (K) (Bottcher, Waldeyer); the outer cells (a, a) number 12,000 in man (Retzius), and rest 
 upon the basement membrane, being disposed in three or even four rows. Between the outer hair 
 cells there are other cellular structures, which are either regarded as special cells (Deiter's cells), 
 or are regarded merely as processes of the hair cells (Lavdowsky). [The cochlear branch of the 
 auditory nerve enters the modiolus, and runs upward in the osseous channels there provided for it, 
 and as it does so gives branches to the lamina spiralis, where they run between the osseous plates 
 which form the lamina.] The fibres (N) come out of the lamina spiralis after traversing the gan- 
 glionic cells in their course (Figs. 524, 527, I, G), and end by fine varicose fibrils in the hair 
 cells (Fig. 527) (Waldeyer, Gottstein, Lavdowsky, Retzius). 
 
 FIG. 527. 
 
 Scheme of the ductus cochlearis and the organ of Corti. N, cochlear nerve : K, inner, and P, outer hair cells ; «, 
 nerve fibrils terminating in P ; a, a, supporting cells ; d, cells in the sulcus spiralis ; z, inner rod of Corti ; Mb. 
 Corti, membrane of Corti, or the membrana tectoria ; o, the membrana reticularis ; H, G, cells filling up the 
 space near the outer wall. 
 
 Membrana Reticularis. — Corti's rods and the hair cells are covered by a special membrane 
 (0), the membrana reticularis of Kolliker. The upper ends of the hair cells, however, project 
 through holes in this membrane, which consists of a kind of a cement substance holding these 
 parts together (Lavdowsky). [Springing from the outer end of the lamina spiralis, or crista spiralis, 
 is the membrana tinctoria, sometimes called the membrane of Corti. It is a well-defined struc- 
 ture, often fibrillated in appearance, and extends outward over the organ of Corti.] Waldeyer 
 regards it as a damping apparatus for this organ (Fig. 527, Mb. Corti). 
 
 [Basilar Membrane. — Its breadth increases from the base to the apex of the cochlea. This 
 fact is important in connection with the theory of the perception of tone. It is supposed that high 
 notes are appreciated by structures in connection with the former, and low notes by the upper parts 
 of the basilar membrane. In one case, recorded by Moss and Steinbrugge, a patient heard low 
 notes only in the right ear, and after death it was found that the auditory nerve in the first turn of 
 the cochlea was atrophied.] 
 
 Intra-Labyrinthine Pressure. — The lymph within the labyrinth is under a certain pressure. 
 Every diminution of the pressure of the air in the tympanum is accompanied by a corresponding 
 diminution of the intra-labyrinthine pressure, while conversely every increase of pressure is accom- 
 panied by an increase of the lymph pressure (F. Bezold). 
 
828 THE QUALITY OF A TONE. 
 
 The perilymph of the inner ear flows away chiefly through the aqueductus 
 cochleae, in the circumference of the foramen jugulare, into the peripheral lym- 
 phatic system, which also takes up the cerebro-spinal fluid of the subarachnoid 
 space, while a small part drains away to the subdural space through the internal 
 auditory meatus. The endolymph flows through the arachnoid sheath of the 
 N. acusticus into the subarachnoid space (C. Hasse). 
 
 414. QUALITY OF AUDITORY PERCEPTIONS-PERCEP- 
 TION OF THE PITCH AND STRENGTH OF TONES.— Tones 
 and Noises. — Every normal ear is able to distinguish musical tones and noises. 
 Physical experiments prove that tones are produced when a vibrating elastic body 
 executes periodic movements, i.e., when the sounding body executes the same 
 movement in equal intervals of time, as the vibrations of a string which has been 
 plucked. A noise is produced by non-periodic movements, i.e., when the, 
 sounding body executes unequal movements in equal intervals of time. [The 
 non-periodic movements clash together on the ear, and produce dissonance, as 
 when we strike the keyboard of a piano at random.] This is readily proved by 
 means of the siren. Suppose that there are forty holes in the rotatory disk of this 
 instrument, placed at exactly the same distance from each other — on rotating the 
 disk and directing a current of air against it, obviously with every rotation the 
 air will be rarefied and condensed exactly forty times. Every two condensations 
 and rarefactions are separated from each other by an equal interval of time. This 
 arrangement yields a characteristic musical tone or note. If a similar disk with 
 holes perforated in it at unequal distances be used, on air being forced against it, 
 a whirring, non-musical noise is produced, because the movements of the sounding 
 body (the condensations and rarefactions of the air) are non-periodic. [The 
 double siren of v. Helmholtz is an improved instrument for showing the same 
 facts.] 
 
 The normal ear also distinguishes in every tone three distinct factors : — 
 [(1) Intensity or force; (2) Pitch; (3) Quality, timbre or " klang."~] 
 
 1. The intensity of a tone depends upon the greater or lesser amplitude of 
 the vibrations of the sounding body. Every one knows that a vibrating string 
 emits a feebler sound when its excursions are smaller. (The intensity of a sound 
 corresponds to the degree of illumination or brightness in the case of the eye.) 
 
 2. The pitch depends upon the number of vibrations which occur in a given 
 time (Mersenne, i6j6) [or the length of time occupied by a single vibration]. 
 This is proved by means of the siren. If the rotating disk have- a series of forty 
 holes at equal intervals, and another series of eighty equidistant from each other, 
 on blowing a stream of air against the rotating disk we hear two sounds of unequal 
 pitch, one being the octave of the other. (The perception of pitch corresponds 
 to the sensation of color in the case of the eye.) 
 
 3. The quality or timbre ("Jflangfarbe") is peculiar to different sonorous 
 bodies. [It is the peculiarity of a musical tone by which we are enabled to distin- 
 guish it as coming from a particular instrument, or from the human voice. Thus, 
 the same note struck on a piano and sounded on a violin differs in quality or 
 timbre. ] It depends upon the peculiar form of the vibration, or the form of the 
 wave of the sonorous body.. (There is no analogous sensation in the case of 
 light.) 
 
 I. Perception of Pitch. — By means of the organ of hearing we can determine that different 
 tones have a different pitch. In the so called musical scale, or gamut, this difference is very marked 
 to a normal ear. But in the scale there are again four tones, which, when they are sounded together, 
 cause in a normal ear the sensation of an agreeable sound, which once heard can readily be repro- 
 duced. This is the tone of the so-called Accord, Triad, or Common Chord, consisting of the 1st, 
 3d, and 5th tones of the scale, to which the 8th tone or octave is added. We have next to determine 
 the pitch of the tones of the chord, and then that of the other tones' of the scale. The siren is used 
 for the fundamental experiment, from which the others can easily be calculated. Four concentric 
 circles are drawn upon the rotatory disk of the siren ; the inner circle contains 40 holes, the second 
 
PERCEPTION OF PITCH. 829 
 
 50, the third 60, and the outer 80 — all the holes being at equal distances from each other. If the 
 disk be rotated, and air forced against each series of holes in turn, we distinguish successively the 
 four tones of the accord (major chord with its octave) ; when all the four series are blown upon 
 simultaneously, we hear in complete purity the major chord itself. The relative number of the 
 holes in the four series indicates in the simplest manner the relative pitch of the tones of the major 
 chord. While one revolution of the disk is necessary to produce the fundamental ground tone 
 (key-note or tonic) with 40 condensations and rarefactions of the air — in order to produce the 
 octave, we must have double the number of condensations and rarefactions during one revolution 
 in the same time. Thus, the relation of the number of vibrations of the Ground tone or Tonic to 
 the Octave next above it, is 1 : 2. In the second series we have 50 holes, which cause the pitch of 
 the Third; hence, the relation of the Ground tone to the Third in this case is 40: 50, or 1 : l\ = \, 
 i. e., for every vibration of the Ground tone there are J vibrations in the Third. In the third series 
 are 60 holes, which, when blown upon, yield the Fifth ; hence, the ratio of the Ground tone to the 
 Fifth in our disk is 40 : 60, or 1 : 1 \ = f . In the same way. we can estimate the pitch of the Fourth 
 tone, and we find that the number of vibrations of the First, Third, Fifth, and Octave are to each 
 other as I : J : § : z. 
 
 The Minor chord is quite as characteristic to a normal ear as the Major. It is distinguished 
 essentially from the latter by its Third being half a tone lower. We can easily imitate it by the 
 siren, as the Minor Third consists of a number of vibrations which stand to the Ground tone as 
 6 : 5, i. e., if 5 vibrations occur in a given time in the Ground tone, then 6 occur in the Minor Third; 
 its vibration number, therefore, is f . 
 
 From these relations of the Major and Minor common chords we may calculate the relative tones 
 in the scale, and we must remember that the Octave of a tone always yields the fullest and most 
 complete harmony. It is evident that as the Major Third, the Minor Third, and the Fifth harmonize 
 with the fundamental Ground tone or key-note, they must also harmonize with the Octave of the 
 key-note. We obtain from the Major Third with the number of vibrations J, the Minor Sixth with 
 |, from the Minor Third with £, the Major Sixth = (^ =) f ; from the Fifth with f, the Fourth 
 = f . These relations are known as the •' Inversions of the intervals." These relations of the tones 
 are, collectively, the consonant intervals of the scale. The dissonant stages, or discords, of the scale 
 can be obtained as follows : Suppose that we have the Ground tone or key-note C, with the number 
 of vibrations = 1, the Third E = J, the Fifth G = f, and the Octave = 2, we then derive from the 
 Fifth or Dominant G a Major chord — this is G, B, Dl. The relative number of vibrations of these 
 3 tones is the same as in the Major chord of C,, C, E, G. Hence, the number of vibrations of G : B 
 is as C : E. When we substitute the values we obtain § ; B = 1 : { — i. e., B = y . But D 1 : B = 
 G : E ; so that D : y — § : J, i- e., D' = y , or an octave lower, we have D = f . Deduce from F 
 (subdominant) a Major chord, F, A, CI. The relation of A : Cl= E : G, or A : 2 = | : §, i. e., A 
 = f . Lastly, F : A = C : E, or F : $ = 1 : |, i. e., F = $ . So that all the tones of the scale have 
 the following number of vibrations : I, C = I ; II, D = | ; III, E = J ; IV, F = * ; V, G = f ; 
 VI, A = I ; VII, B = y ; . VIII, C = 2. 
 
 Conventional Estimate of Pitch. — Conventionally, the pitch or concert pitch of the note, a, 
 is taken at 440 vibrations in the second (Scheibler, 1834), although in France it is taken at 435 
 vibrations per second. From this we can estimate the absolute number of vibrations for the tones 
 of the scale: C = 33, = 37.125, E = 41.25, F = 44, 6 = 49.5, A = 55. B = 61.875 vibrations. 
 The number of vibrations of the next highest octave is found at once by multiplying these numbers 
 by 2. 
 
 Musical Notes. — The lowest notes used in music are the double bass, E, with 41.25 vibrations, 
 piano-forte C with 33, grand piano A 1 with 27.5, and organ C with 16.5. The highest notes in 
 music are the piano-forte c* with 4224, and d' on the piccolo flute, with 4752 vibrations per second. 
 
 Limits of Auditory Perception. — According to Preyer, the limit of the 
 perception of the lowest audible tone lies between sixteen and twenty-three vibra- 
 tions per second, and e Tl " with 40,960 vibrations as the highest 
 audible tone; so that this embraces about n^ octaves. FiG.^528. 
 
 [Audibility of Shrill Notes. — This varies very greatly in different persons 
 {Wollaston). There is a remarkable falling off of the power as age advances. 
 (Galton). For testing this, Galton uses a small whistle (Fig. 528] made of a 
 brass tube, with a diameter of le,s than T ] jth of an inch. A plug is fitted at the 
 lower end to lengthen or shorten the tube, whereby the pitch of the note is 
 altered. Among animals Galtoo finds none superior to cats in the power of hear- 
 ing shrill sounds, and he attributes this "to differentiation by natural selection 
 among these animals until they have the power of hearing all the high notes 
 made by mice and other little creatures they have to catch."] 
 
 Variations in Auditory Perception. — It is rare to find that tones produced by 
 more than 35,000 vibrations per second are heard. When the tensor tympani is 
 contracted, the perception maybe increased for tones 3000 to 5000 vibrations 
 higher, but rarely more. Pathologically, the perception for high notes may be Galton's whistle. 
 
830 PERCEPTION OF QUALITY. 
 
 abnormally acute — (i ) When the tension of the sound-conducting apparatus generally is increased. 
 (2) By elimination of the sound- conducting apparatus of the middle ear, which offers greater or 
 less resistance to the propagation of very high notes, as perforation of the membrana tympani, or 
 loss of the incus and malleus. In these cases the stapes is directly set in vibration by the sound 
 waves, when tones up to 80,000 vibrations have been perceived. Diminished tension of the sound- 
 conducting apparatus causes diminution of the perception for high tones (Blake). 
 
 A smaller number of vibrations than 16 per second (as in the organ) are no longer heard as a 
 tone, but as single, dull impulses. The tones that are produced beyond the highest audible note, 
 as by stroking small tuning-forks with a violin bow, are also no longer heard as tones, but they 
 cause a painful cutting kind of impression in the ear. In the musical scale the range is, approxi- 
 mately, from C of the first octave with 16.5 vibrations to e, the eighth octave. 
 
 Comparison of Ear and Eye. — In comparing the perception of the eye with that of the ear, 
 we see at once that the \ange of accommodation of the ear is much greater. Red has 456 billions 
 of vibrations per second, while the visible violet has but 667, so that the eye only takes cognizance 
 of vibrations which do not form even one octave. 
 
 Lowest Audible Tone. — As to the smallest number of successive vibrations 
 which the ear can perceive as a sensation of tone, Savart and Pfaundler considered 
 that two would suffice. If, however, we exclude in our experiments the possibility 
 of the occurrence of over-tones (4 to 8) (Mack), or even 16 to 20 vibrations (F, 
 Auerbach, KohlrauscK) are necessary to produce a characteristic tone. 
 
 When tones succeed each other rapidly, they are still perceived as distinct, 
 when at least 0.1 second intervenes between two successive tones (v. Helmholtz) ; 
 if they follow each other more rapidly they fuse with each other, although a short- 
 time interval is sufficient for many musical tones. 
 
 By the term, "fineness of the ear," or, as we say, a " good ear," is meant the 
 capacity of distinguishing from each other, as different, two tones of nearly the 
 same number of vibrations. This power can be greatly increased by practice, so 
 that musicians can distinguish tones that differ in pitch by only -^$, or even -j-j^-j, 
 of their vibrations. 
 
 With regard to the time sense, it is found that beats are more precisely per- 
 ceived by the ear than by the other sense organs (Horing, Mach, Vierordt). 
 
 Pathological. — According to Lucae, there are some ears that are better adapted for hearing low 
 notes and others for high notes. Both conditions are disadvantageous for hearing speech. Those 
 who hear low notes best hear the highest consonants imperfectly. The low notes are heard abnor- 
 mally loud in rheumatic facial paralysis, while the high tones are heard abnormally loud in cases of 
 loss of the membrana tympani, incus, and malleus. The stapedius is in full action, whereby the 
 highest tones are heard louder at the expense of the lower notes. Many persons with normal hear- 
 ing hear a tone higher with oife ear than with the otner. This condition is called diplacusis bin- 
 auralis. In rare cases sudden loss of the perception of certain tones has been observed, e. g., the 
 base-deafness of Moos. In a case described by Magnus, the tones dl , bl , were not heard 
 
 (2 3i6)- 
 
 II. Perception of the Intensity of Tone. — The intensity of a tone depends upon the ampli- 
 tude of the vibrations of the sounding body. The intensity of the tone is proportional to the square 
 of the amplitude of vibration of the sounding body, i. c, with 2, 3, or 4 times the amplitude the 
 intensity of the tone is 4, 9, 16 times as strong. As sonorous vibrations are communicated to our 
 ears by the wave movements of the air, it is evident that the tones must become less and less intense 
 the further we are from the source of the sound. The intensity of the sound is inversely propor- 
 tional to the square of the distance of the source of the sound from the ear. 
 
 Tests. — 1. Place a watch horizontally near the ear, and test how close it may be brought to the 
 ear, and also how far it may be removed, and still its sounds be heard. Measure the distance. 2. 
 Itard uses a small hammer suspended like a pendulum, and allowed to fall upon a hard surface. 3. 
 Balls of different weights are allowed to fall from varying heights upon a plate. In this case the 
 intensity of the sound is proportional to the product of the weight of the ball into the height it 
 falls. - 
 
 As to the limits of the perception of the intensity of a tone, it is found that a spherule weighing 
 1 milligram, and falling from a height of I mm. upon a glass plate, is heard at a distance of 5 cen- 
 timetres (Schafhauli). 
 
 415. PERCEPTION OF QUALITY— ANALYSIS OF VOWELS.-By the term 
 quality (" Klangfarbe "), musical color or timbre, is understood a peculiar character of the tone, 
 by which it can be distinguished apart from its pitch and intensity. Thus, a flute, horn, violin, and 
 the human .voice may all sound the same note with equal intensity, and yet all the four are distin- 
 guished at once by their specific quality. Wherein lies the essence (" Wesen ") of tone color ? The 
 
ANALYSIS OF VOWELS. 
 
 831 
 
 investigations of v. Helmholtz have proved that, among mechanisms which produce tones, only 
 those that produce pendulum-like vibrations, i. e., the to-and-fro vibrations of a metallic rod with 
 one end fixed, and tuning-forks, execute simple pendulum-like vibrations. This can be shown by 
 making a tuning-fork write off its vibrations on a recording surface, when a completely uniform 
 wave line, with equal elevations and depressions, is noted. The term " tone " is restricted to those 
 sounds, hardly ever occurring in nature, which are due to simple pendulum-like vibrations. Other 
 investigations have shown that the tones of musical instruments and of the human voice, all of 
 which have a characteristic quality of their own, are composed of many single simple tones. Among 
 these one is characterized by its intensity, and at the same time it determines the pitch of the whole 
 compound musical "tone-picture." This is called the fundamental tone-or key-note. The other 
 weaker tones which, as it were, spring from and are mingled with this, vary in different instruments 
 both in intensity and number. They are " upper tones," and their vibrations are always some 
 multiple — 2, 3, 4, 5 ... . times — of the fundamental tone or key-note. In general, we say that all 
 those outbursts of sound which embrace numerous strong upper tones, especially of high pitch, in 
 addition to the fundamental tone, are characterized by a sharp, piercing, and rough quality, such as 
 emanates from a trumpet or clarionet, and that conversely the quality is characterized by mildness 
 and softness when the over-tones are few, feeble, and low, e. g., such as are produced by the flute. 
 It requires a well-trained musical ear to distinguish, in an instrumental burst, the over-tones apart 
 from the fundamental tone. But this is very easily done with the aid of resonators (Fig. 532). 
 These consist of spherical or funnel-shaped hollow bodies, made of brass or some other substance, 
 which, by means of a short tube, can be placed in the outer ear. If a resonator be placed in the 
 ear, we can hear the feeblest over-tone of the same number of vibrations as the fundamental tone. 
 Thus, musical instruments are distinguished by the number, intensity, and pitch of the overtones 
 which they produce. A vibrating metallic rod and a tuning-fork have no over-tones ; they only give 
 the fundamental tone. As already mentioned, the term simple tone is applied to sounds due to 
 simple pendulum-like vibrations, while a sound composed of a fundamental tone and over-tones is 
 called a " klang " or compound musical tone. 
 
 Vibration Curve of a Musical Tone. — When we remember that a musical tone or clanjj con- 
 sists of a fundamental tone and a number of over- 
 tones of a certain intensity, which determine its 
 quality, then we ought to be able to construct 
 geometrically the vibration curve of the musical 
 tone. Let A represent the vibration curve of the 
 fundamental tone, and B that of the first moder- 
 ately weak over-tone (Fig. 529). The combina- 
 tion of these two curves is obtained simply by 
 computing the height of the ordinates, whereby 
 the ordinates of the over-tone curve, lying above 
 the abscissa or horizontal line, are added to the 
 fundamental lone curve, while those of the ordi- 
 nates below the line are subtracted from it. Thus 
 we obtain the curve C, which is not a simple pen- 
 dulum-like curve, but one which corresponds to 
 an unsteady movement. A new curve of the 
 second over- tone may be added to C, and so on. 
 The result of all these combinations is that the 
 vibration curves corresponding to the compound 
 musical tones are unsteady periodic curves. All 
 these curves must, of course, vary with the number 
 and pitch of the compounded over-tone curves. 
 
 Displacement of the Phases.— The form of Curves of a musica i tone obtained by compounding the 
 the vibration of one and the same musical tone curve of a fundamental tone with that of its over-tones, 
 may vary greatly, if, in compounding the curves 
 
 A and B, the curve B is only slightly displaced laterally. If B is displaced so that the hollow of 
 the wave r falls under A, the addition of both curves yields the curve r, r, r, with small elevations 
 and broad valleys. If B be displaced still further, until the elevation of the wave, h, coincides 
 with A, we obtain still another form, so that by displacement of the phases of the wave motions of 
 the compounded pendulum-like vibrations, we obtain numerous different forms of the same musical 
 tone. The displacement of the phases, however, has no effect on the ear. 
 
 The general result of these observations, and those of Fourier, is that the quality of a musical 
 tone depends upon the characteristic form of the vibratory movement. 
 
 Analysis of Vowels. — The human voice represents a reed instrument with vibrating elastic 
 membranes, the vocal cords (§ 312). In uttering the various vowels the mouth assumes a charac- 
 teristic form, so that its cavity has a certain fundamental tone peculiar to itself. Thus, to the funda- 
 mental tone of a certain pitch produced within the larynx, there are added certain over-tones, which 
 communicate to the larnygeal tone the vocal or vowel quality. Hence, a vowel is the timbre or 
 quality of a musical tone which is produced in the larynx. The quality depends upon the number, 
 
832 
 
 ARTIFICIAL VOWELS. 
 
 intensity, and pitch of the over-tones, and the latter, again, depend on the configuration of the 
 " vocal cavity" (g 317) in uttering the different vowels. 
 
 Suppose a person to sing the vowels one after the other on a special note, e. g., b JZ, we can, with 
 the aid of resonators, determine the over-tones, and in what intensity they are mixed with the fun- 
 damental tone, b J2, to give the characteristic quality. According to v. Helmholtz, when we sound 
 the vowels on b J2, for each of the three vowels, one over-tone is specially characteristic for A-b 11 )? ; 
 for O-blJz; for U-f. The other vowels and the diphthongs have each two specially characteristic 
 over-tones, because in these cases the mouth is so shaped that the posterior larger cavity, and also 
 the anterior narrower part, each yields a special tone (J 316, I and E). These two over-tones are 
 forE-B"'|2and fi; for I-d 1 ' and f ; for A-g" ' and d "; for6-c'" # and fi; for U-g 1 " and f. These, 
 however, are only the special upper tones. There are many more upper tones, but they are not so 
 prominent. 
 
 Artificial Vowels. — Just as it is possible to analyze a vowel into its fundamental tone and its 
 upper tones, it is possible to compound tones to produce the vowels by simultaneously sounding the 
 fundamental tone and the corresponding upper tones. (1) A vowel is produced simply by singing 
 loudly a vowel, e. g., A, upon a certain note against the free strings of an open piano, while by the 
 pedal the damper is kept raised. As soon as we stop singing, the characteristic vowel is sounded 
 by the strings of the piano. The voice sets into sympathetic vibration all those strings whose over- 
 
 Fig. 530. 
 
 Koenig's manometric capsule (A) and mirror (M) —(Koenig), 
 
 tones (in addition to the fundamental tone) occur in the vocal compound tone, so that they vibrate 
 for a time after the voice ceases {v. Helmholtz). (2) The vowel apparatus devised by v. Helm- 
 holtz consists of numerous tuning-forks, which are kept vibrating by means of electro-magnets. 
 The lowest tuning-fork gives the fundamental tone, B \t and the others the over-tones. A resonator 
 is placed in front of each tuning-fork, and the distance between the two can be varied at pleasure. 
 The resonators can be opened and closed by a lid passing in front of their openings. When the 
 resonator is closed, we cannot hear the tone emitted by the tuning-fork placed in front of it; but 
 when one or more resonators are opened the tone is heard distinctly, and it is louder the more the 
 resonator is opened. By means of a series of keys, like the keys of a piano-forte, we can rapidly 
 open and close the resonators at will, and thus combine various overtones with the fundamental 
 tone so as to produce vowels with different qualities. V. Helmholtz makes the following composi- 
 tions : — U = B k with b £ weak and f ' ; O = damped B Jz with b' J? strong and weaker b J2, f ' , 
 d" ; A = b |2 (fundamental tone) with moderately strong b 1 ]2 and f ", and strong b 1 ' J2 and d 1 " ; 
 A = b (j (fundamental tone) with b' j? and f ", somewhat stronger than for A, d' strong, b" b weaker, 
 d lll andf"' as strong as possible; E = b J2 (as fundamental tone) moderately strong, with b 1 [2 
 and f ' moderate also, and f "' , a 111 J2, and b 1 " )?, as strong as possible; I could not be produced. 
 
ACTION OF THE LABYRINTH DURING HEARING. 
 
 833 
 
 In Appunn's apparatus, the fundamental tone and the over-tones are produced by means of 
 organ pipes, whose notes can be combined to produce the vowels, but it is not so good as the tuning- 
 forks, since the organ pipes do not yield simple tones; but, nevertheless, some of the vowels can 
 be admirably reproduced with this apparatus. 
 
 Edison's Phonograph. — If we utter the vowels against a delicate membrane stretched over the 
 end of a hollow cylinder, and if a writing style be fixed to the centre of the membrane, and the 
 style be so arranged that it can writeor record its movements on a piece of soft tinfoil arranged on 
 a revolving apparatus, then the vowel curve is stamped, as it were, upon the tinfoil. If the style 
 now be made to touch the tinfoil while the latter is moved, then the style is moved; it moves the 
 membrane, and we hear distinctly, by resonance, the vowel sound reproduced. 
 
 [Koenig's Manometric Flames. — This is a most ingenious apparatus, and by means of it the 
 quality of the vowel sounds is easily shown. It consists of a small wooden capsule, A, divided 
 into two compartments by a piece of thin sheet India-rubber. Ordinary gas passes into the chamber 
 on one side of the membrane, through the stop-cock, and it is "lighted at a small burner. To the 
 other compartment is attached a wider tube, with a mouth piece. The whole is fixed on a stand 
 (Fig. 530), and near it is placed a four-sided rotating mirror, M, as suggested by Wheatstone. On 
 speaking or singing a vowel into the mouth piece, and rotating the mirror, a toothed or zigzag flame 
 
 Fig. 531. 
 
 B/ 4 4M4MlMji£d^JJfAA 
 
 '" so, P Zlfl j^B18W?3^^P?PQH^E^ 
 
 ^4tgB«P^ /±*W0U. Mjflm MsKml^ 
 
 2 
 
 4/iM/iM^^Mi 
 
 
 ^Sisl^ =^==S=fu;— 1^- -■■■ ._ — _----:-: -===_-^ _ ., ■.-..... 
 
 sol 
 
 1 
 
 *jM L lAJasJl iuhiij^ JjdAJ. 
 
 1 
 
 a/Ua a ' :Md ^ Jj^Mi 4 Sj^ a - 
 
 lit 
 2 
 
 ^ii jJldk.aM.uk MM.^kM 
 
 A sol 
 
 1 
 
 Si kik kiis k ik liM idJkfdi 
 
 1 
 
 adddji* mLdiddM " A ^ uJ *t±*\' At 'd - 4* 
 
 Flame pictures of the vowels ou, o and a (Koenig). 
 
 picture is obtained in the mirror. The form of the flame picture is characteristic for each vowel, 
 and varies, of course, with the pitch.] [Fig. 531 shows the form of the flame picture obtained in 
 the rotating mirror when the vowels OU, o, A, a:e sung at the pitch of uf lt sol^ and ut 2 . This 
 series shows how they differ in quality.] 
 
 [Koenig has also invented the apparatus (Fig. 532) for analyzing any compound tone whose 
 fundamental tone is UT 2 . It consists of a series of resonators, from ut 2 to ut 5 , fixed in an iron 
 frame. Each resonator is connected with its special flame, which is pictured in a long, narrow 
 square, rotating mirror. If a tuning-fork UT 2 be sounded, only the flame ut 2 is affected, and so 
 on with each tuning-fork of the harmonic series. Suppose a compound note containing the funda- 
 mental tone UT 2 , and its harmonics be sounded, then the flame of UT 2 , and those of the other har- 
 monics in the note are also affected, so that the tone can be analyzed optically. The same may be 
 done with the vowels.] 
 
 416. ACTION OF THE LABYRINTH DURING HEARING.— 
 
 If we ask what role the ear plays in the perception of the quality of sounds, then 
 we must assume that, just as with the help of" resonators a musical note can be 
 S3 
 
834 
 
 ACTION OF THE LABYRINTH DURING HEARING. 
 
 resolved into its fundamental tone and over-tones, so the ear is capable of per- 
 forming such an analysis. The ear resolves the complicated wave forms of mu- 
 sical tones into their components. These components it perceives as tones harmo- 
 nious with each other ; with marked attention each is perceived singly, so that 
 the ear distinguishes as different tone colors only different combinations of these 
 simple tone sensations. The resolution of complex vibrations, due to quality, into 
 simple pendulum-like vibrations is a characteristic function of the ear. What 
 apparatus in the ear is capable of doing this? If we sing vigorously — e.g., the 
 musical vowel A on a definite note, say b |z — against the strings of an open piano- 
 forte while the damper is raised, then we cause all those strings, and only those, to 
 vibrate sympathetically, which are contained in the vowel so sung. We must, 
 
 Fig. 532. 
 
 Koenig's apparatus for analyzing a compound tone with the fundamental tone ut,; 
 
 therefore, assume that an analogous sympathetic apparatus occurs in the ear, which 
 is tuned, as it were, for different pitches, and which will vibrate sympathetically 
 like the strings of a piano-forte. " If we could so connect every string of a piano 
 with a nerve fibre that the nerve fibre would be excited and perceived as often as 
 the string vibrated, then, as is actually the case in the ear, every musical tone 
 which affected the instrument would excite a series of sensations exactly corre- 
 sponding to the pendulum-like vibrations into which the original movements of 
 the air can be resolved ; and thus the existence of each individual over-tone 
 would be exactly perceived, as is actually the case with the ear. The perception 
 of tones of different pitch would, under these circumstances, depend upon dif- 
 ferent nerve fibres, and hence would occur quite independently of each other. 
 
SIMULTANEOUS ACTION OF TWO TONES. 835 
 
 Microscopic investigation shows that there are somewhat similar structures in the 
 ear. The free ends of all the nerve fibres are connected with small elastic par- 
 ticles, which we must assume are set into sympathetic vibration by the sound 
 waves" (v. Helmholtz). 
 
 Resolution by the Cochlea. — Formerly, v. Helmholtz considered the rods 
 of Corti to be the apparatus that vibrated and stimulated the terminations of 
 the nerves. But, as birds and amphibians, which certainly can distinguish 
 musical tones, have no rods (Hasse), the stretched radial fibres of the membrana 
 basilaris, on which the organ of Corti is placed, and which are shortest in the first 
 turn of the cochlea, becoming longer toward the apex of the cochlea, are now 
 regarded as the vibrating threads {Hensen). Thus, a string-like fibre of the mem- 
 brana basilaris, which is capable of vibrating, corresponds to every possible 
 simple tone. According to Hensen, the hairs of the labyrinth, which are of 
 unequal length, may serve this purpose. Destruction of the apex of the cochlea 
 causes deafness to deeper tones (Baginsky). 
 
 [Hensen's Experiments. — That the hairs in connection with the hair cells 
 vibrate to a particular note is also rendered probable by the experiments of Hensen 
 on the crustacean Mysis. He found that certain of the minute hairs (auditory 
 hairs) in the auditory organ of this animal, situate at the base of the antennas, 
 vibrated when certain tones were sounded on a keyed horn. The movements of 
 the hairs were observed by a low-power microscope. In mammals, however, there 
 is a difficulty, as the hairs attached to the cells appear to be all about the same 
 length. We must not forget that the perception of sound is a mental act.] 
 
 This assumption also explains the perception of noises. 
 
 Of noises in the strictly physical sense, it is assumed that they, like single 
 impulses, are perceived by the aid of the saccules and the ampullae. 
 
 It is assumed that the saccules and the ampullae are concerned in the general 
 perception of hearing, i.e., of shocks communicated to the auditory nerve (by 
 impulses and noises) ; while by the cochlea we estimate the pitch and depth of 
 the vibrations, and musical character of the vibrations produced by tones. 
 
 The relation of the semicircular canals to the equilibrium of the body is 
 referred to in § 350. 
 
 417. SIMULTANEOUS ACTION OF TWO TONES— HAR- 
 MONY — BEATS — DISCORDS — DIFFERENTIAL TONES. — 
 
 When two tones of different pitch fall upon the ear simultaneously, they cause 
 different sensations, according to the difference in pitch. 
 
 1. Consonance. — If the number of vibrations of the two tones is in the ratio 
 of simple multiples, as 1 : 2 : 3 : 4, so that when the low note makes one vibra- 
 tion the higher one makes 2 : 3 or 4 ... . then we experience a sensation of com- 
 plete harmony or concord. 
 
 2. Interference. — If, however, the two tones do not stand to each other in 
 the relation of simple multiples, then when both tones are sounded simultaneously 
 interference takes place. The hollows of the one sound wave can no longer coin- 
 cide with the hollows of the other, and the crests with the crests, but, corre- 
 sponding to the difference of number of vibrations of both curves, sometimes a 
 wave crest must coincide with a wave hollow. Hence, when wave crest meets 
 wave crest, there must be an increase in the strength of the tone, and when a 
 hollow coincides with a crest, the sound must be weakened. Thus we obtain 
 the impression of those variations in tone intensity which have been called 
 " beats." 
 
 The number of vibrations is, of course, always equal to the difference of the number of vibrations 
 of both tones. The beats are perceived most distinctly when two organ tones of low pitch are 
 sounded together in unison, but slightly out of tune. Suppose we take two organ pipes with 33 
 vibrations per second, and so alter one pipe that it gives 34 vibrations per second, then one distinct 
 beat will be heard every second. The beats are heard more frequently the greater the difference 
 between the number of vibrations of the two tones. 
 
836 PERCEPTION OF THE DIRECTION OF SOUNDS. 
 
 Successive Beats. — The beats, however, produce very different impressions 
 upon the ear, according to the rapidity with which they succeed each other. 
 
 i. Isolated Beats. — When they occur at long intervals, we may perceive them 
 as completely isolated, but single intensifications of the sound with subsequent 
 enfeeblement, so that they give rise to the impression of isolated beats. 
 
 2. Dissonance. — When the beats occur more rapidly they cause a continuous 
 disagreeable whirring impression, which is spoken of as dissonance, or an unhar- 
 monious sensation. The greatest degree of unpleasant painful dissonance occurs 
 when there are 33 beats per second. 
 
 3. Harmony. — If the beats take place more rapidly than 33 times per second, 
 the sensation of dissonance gradually diminishes, and it does so the more rapidly 
 the beats occur. The "sensation passes gradually from moderately inharmonious 
 relations (which in music have to be resolved by certain laws) toward consonance 
 or harmony. The tone relations are successively the Second, Seventh, Minor 
 Third, Minor Sixth, Major Third, Major Sixth, Fourth, and Fifth. 
 
 4. Action of the Musical Tones (" Klange"). — Two musical "klangs," 
 or compound tones, falling on the ear simultaneously, produce a result similar to 
 that of two simple tones ; but in this case we have to deal not only with the two 
 fundamental tones, but also with the over-tones. Hence the degree of dissonance 
 of two musical tones is the more pronounced the more the fundamental tones and 
 the over-tones (and the "differential" tones) produce beats which number about 
 33 per second. 
 
 5. Differential Tones. — Lastly, two "klangs," or two simple musical tones 
 sounding simultaneously, may give rise to new tones when they are uniformly and 
 simultaneously sounding in corresponding intensity. We can hear, if we listen 
 attentively, a third new tone, whose number of vibrations corresponds to the dif- 
 ference between the two primary tones, and hence it is called a "differential 
 tone." 
 
 Summational Tones. — It was formerly supposed that new tones could arise from the summation 
 or addition of their number of vibrations, but it has been shown that these tones are, in reality, 
 differential tones of a high order (Appunn, Preyer). 
 
 418. PERCEPTION OF SOUND— FATIGUE OF THE EAR- 
 OBJECTIVE AND SUBJECTIVE AUDITION— AFTER SEN- 
 SATION. — Objective Auditory Perceptions. — When the stimulation of 
 the terminations of the nerves of the labyrinth is referred to the outer world, 
 then we have objective auditory perceptions. Such stimulations are only referred 
 to the outer world as are conveyed to the membrana tympani by vibrations of the 
 air, as is shown by the fact that if the head be immersed in water, and the audi- 
 tory meatuses be filled thereby, we hear all the vibrations as if they occurred 
 within our head itself {Ed. Weber), and the same is the case with our own voice, 
 as well as with the sound waves conducted through the bones of the head, when 
 both ears are firmly plugged. 
 
 Perception of Direction. — As to the perception of the direction whence 
 sound comes, we obtain some information from the relation of both meatuses to 
 the source of the sound, especially if we turn the head in the supposed direction of 
 the sound. We distinguish more easily the direction from which noises mixed 
 with musical tones come than that of tones (RayleigK). When both ears are 
 stimulated equally, we refer the source of the sound to the middle line anteriorly, 
 but when one ear is stimulated more strongly than the other, we refer the source 
 of the sound more to one side (Kessel). The position of the ear muscles, which, 
 perhaps, act like an ear funnel, is important. According to Ed. Weber, it is 
 more difficult to determine the direction of sound when the ears are firmly fixed 
 to the side of the head. Further, if we place the hollow of both hands in front 
 of the ear, as to form an open cavity behind them, we are apt to suppose that a 
 sounding body placed in front is behind us. 
 
COMPARATIVE HISTORICAL. 837 
 
 The distance of a sound is judged of partly by the intensity or loudness of the 
 sound, such as we have learned to estimate from sound at a known distance. But 
 still we are subject to many misconceptions in this respect. 
 
 Among subjective auditory sensations are the after vibrations, especially of intense and 
 continued musical tones ; the tinnitus aurium (p 637), which often accompanies abnormal move- 
 ments of the blood in the ear, may be due to a mechanical stimulation of the auditory fibres, perhaps 
 by the blood stream {Brenner). 
 
 [Drugs. — Cannabis indica seems to act on the hearing centre, giving rise to subjective sounds ; 
 the hearing is rendered more acute by strychnin; while quinine and sodic salicylate in large doses 
 cause ringing in the ears (Brunton).~\ 
 
 Entotical perceptions, which are due to causes within the ear itself, are such as hearing the 
 pulse beats in the surrounding arteries, and the rushing sound of the blood, which is especially strong 
 when there is increased resonance of the ear (as when the meatus or tympanum is closed, or when 
 fluid accumulates in the latter), during increased cardiac action, or in hyperesthesia of the auditory 
 nerve (Brenner). Sometimes there is a cracking noise in the maxillary articulation, the noise pro- 
 duced by traction of the muscles on the Eustachian tube (\ 411), and when air is forced into the 
 latter, or when the membrana tympani is forced outward or inward (\ 350). 
 
 Fatigue. — The ear after a time becomes fatigued, either for one tone or for a series of tones 
 which have acted on it, while the perceptive activity is not affected for other tones. Complete re- 
 covery, however, takes place in a few seconds ( Urbantschitsch). 
 
 Auditory After Sensations. — (1) Those that correspond to positive after sensations, where the 
 after sensation is so closely connected with the original tone that both appear to be continuous. ( 2) 
 There are some after sensations, where a pause intervenes between the end of the objective and the 
 beginning of the subjective tone (Urbantschitsch). (3) There seems to be a form corresponding to 
 negative after images. 
 
 In some persons the perception of a tone is accompanied by the subjective colors, or the sensation 
 of light, e.g., the sound of a trumpet, accompanied by the sensation of yellow. More seldom are 
 visual sensations of this kind observed when the nerves of taste, smell, or touch are excited (Nuss- 
 baumer, Lehmann and Bleuler). It is more common to find that an intense sharp sound is accom- 
 panied by an associated sensation of the sensory nerves. Thus many people experience a cold shud- 
 der when a slate pencil is drawn in a peculiar manner across a slate. 
 
 [Color Associations. — Color is in some persons instantaneously associated with sound, and Gal- 
 ton remarks that it is rather common in children, although in an ill-developed degree, and the ten- 
 dency seems to be very hereditary. Sometimes a particular color is associated with a particular 
 letter, vowel sounds particularly evoking colors. Galton has given colored representations of these 
 color associations, and he points out their relation to what he calls number forms, or the associa- 
 tion of certain forms with certain numbers.] 
 
 An auditory impulse communicated to one ear at the same time often causes an increase in the 
 auditory function of the other ear, in consequence of the stimulation of the auditory centres of both 
 sides (Urbantschitsch, Eitelberg). 
 
 Other Stimuli. — The auditory apparatus, besides being excited by sound waves, is also affected 
 by heterologous stimuli. It is stimulated mechanically by a sudden blow on the ear. The effects 
 of electricity and pathological conditions are referred to in \ 350. 
 
 4ig. COMPARATIVE— HISTORICAL.— The lowest fishes, the cyclostomata (Petromy- 
 zon), have a saccule provided with auditory hairs containing otoliths, and communicating with two 
 semicircular canals, while the myxinoids have only one semicircular canal. Most of the other fishes, 
 however, have a utricle communicating with three semicircular canals. In the carp, prolongations 
 of the labyrinth communicate with the swimming bladder. In amphibia, the structure of the laby- 
 rinth is somewhat like that in fishes, but the cochlea is not typically developed. Most amphibia, 
 except the frog, are devoid of a membrani tympani. Only the fenestra ovalis (not the rotunda) ex- 
 ists, and it is connected in the frog by three ossicles with the freely exposed membrana tympani. 
 Among reptiles the appendix to the saccule, corresponding to the cochlea, begins to be prominent. 
 In the tortoise it is saccular, but in the crocodiles it is longer, and somewhat curved and dilated at 
 the end. In all reptiles the fenestra rotunda is developed, whereby the cochlea is connected with 
 the labyrinth. In crocodiles and birds the cochlea is divided into a scala vestibuli and S. tympani. 
 Snakes aTe devoid of a tympanic cavity. In birds both saccules (Fig. 524, IV, U S') are united 
 (Hasse), the canal of the cochlea (U C), which is connected by means of a fine tube (C), with the 
 saccule, is larger, and shows indications of a spiral arrangement, and has a flask-like blind end, the 
 lagena (L). The auditory ossicles in reptiles and birds are reduced to one column-like rod, corre- 
 sponding to the stapes, and called the columella. The lowest mammals (Echidna) have struc- 
 tures very like those of birds, while the higher mammals have the same type as in man (Fig. 524, 
 III). The Eustachian tube is always open in the whale. 
 
 Among invertebrata the auditory organ is very simple in medusse and mollusca. It is merely a 
 bladder filled with fluid, with the auditory nerves provided with ganglia in its walls. Hair cells 
 occur in the interior, provided with one or more otoliths. Hensen observed that in some of the 
 
838 COMPARATIVE — HISTORICAL. 
 
 annulosa, when sound was conducted into the water, some of the auditory bristles vibrated, being 
 adapted for special tones. In cephalopoda we distinguish the first differentiation into a membran 
 ous and cartilaginous labyrinth. 
 
 Historical. — Empedocles (473 B.c) referred auditory impressions to the cochlea. The Hippo 
 cratic School was acquainted with the tympanum, and Aristotle (384 B.c) with the Eustachian tube 
 Vesalius (1561) described the tensor tympani ; Cardanus (1560) the conduction through the bono 
 of the head; while Fallopius (1561) described the vestibule, the semicircular canals, chorda tym 
 pani, the two fenestra?, the cochlea, and the aqueduct. Eustachius (f 1570) described the modio 
 lus, the lamina spiralis of the cochlea, the Eustachian tube, as well as the muscles of the ear ; Plater 
 the^mpullae (1583); Casseri (1600) the lamina spiralis membranacea. Sylvius (1667) discovered 
 the ossicle called by his name ; Vesting (1641) the stapedius. Mersenne (1618) was acquainted 
 with over-tones; Gassendus (1658) experimented on the conduction of sound. Acoustics was greatly 
 advanced by the work of Chladni (1802). The most recent and largest work on the ear in verte- 
 brates is by G. Retzius (1881-84). 
 
THE ORGAN OF SMELL. 
 
 420. STRUCTURE OF THE ORGAN OF SMELL.— Regio Olfactoria.— The area 
 of the distribution of the olfactory nerve is the regio olfactoria, which embraces the upper part of 
 the septum, the upper (Fig. 534, Cs), and part of the middle (Cm) turbinated bone. All the re- 
 mainder of the nasal cavity is called the regio respiratoria. These two regions are distinguished 
 as follows : (1) The regio olfactoria has a thicker mucous membrane. (2) It is covered by a sin- 
 gle layer of cylindrical epithelium (Fig. 533, E), the cells being often branched at their lower ends, 
 and contain a yellow or brownish-red pigment. (3) It is colored by this pigment, and is thereby 
 distinguished from the uncolored regio respiratoria, which is covered by cilated epithelium. (4) 
 It contains peculiar tubular glands (Bowman's glands), while the rest of the mucous membrane 
 contains numerous acinous serous glands (Heidenhain). (5) Lastly, the regio olfactoria embraces 
 the end organs of the olfactory nerve (M. Schultze). The long, narrow olfactory cells (N) are 
 distributed between the ordinary cylindrical epithelium (E) covering the regia olfactoria. The body 
 of the cell is spindle shaped, with a large nucleus containing nucleoli, and it sends upward between 
 the cylindrical cells a narrow (0.9 to 1.8 /i), smooth rod, quite up to the free surface of the mucous 
 membrane. In the frog (»), the free end carries delicate projecting hairs or bristles. In the deeper 
 
 Fl °- 533- 
 
 Fig. 534. 
 
 Vs.jih 
 
 Fig. 533. — N, olfactory cells (human) ; «, from the frog ; E, epithelium of the regio olfactoria. Fig. 534 — Nasal and 
 pharyngo-nasal cavities. L, levator elevation; P, s p., plica salpingo-palatina ; Cs, Cm, Ci, the three turbi- 
 natea bones (Urbantsrhitsck). 
 
 part of the mucous membrane the olfactory cells pass into, and become continuous with, varicose fine 
 nerve fibres, which pass into the olfactory nerve (g 321, I, I). According to C. K. Hoffmann and 
 Exner, after section of the olfactory nerve the specific olfactory end organs become changed into 
 cylindrical epithelium (frog), and in warm blooded animals they undergo fatty degeneration, even 
 on the 15th day. V. Brunn found a homogeneous limiting membrane, which had holes in it for 
 transmitting the processes of the olfactory cells only. 
 
 [The respiratory part of the nasal mucous membrane is lined by ciliated epithelium stratified 
 like that in the trachea and resting on a basement membrane. Below this there are many lymph 
 corpuscles and aggregations of adenoid tissue.] 
 
 [The organ of Jacobson is present in all mammals, and consists of two narrow tubes protected 
 by cartilage, and placed in the lower and anterior part of the nasal septum. Each tube terminates 
 blindly behind, but anteriorly it opens into the nasal furrow or into the naso-palatine canal (dog). 
 The wall next the middle line is covered by olfactory epithelium, and receives olfactory nerves 
 (rabbit, guinea pig), and it contains glands similar to those of the olfactory . region ; the outer wall 
 is covered by columnar epithelium ciliated in some animals (A7«»).] 
 
 839 
 
840 OLFACTORY SENSATIONS. 
 
 421. OLFACTORY SENSATIONS.— Olfactory sensations are produced 
 by the action of gaseous odorous substances being brought into direct contact 
 with the olfactory cells, during the act of inspiration. The current of air is 
 divided by the anterior projection of the lowest turbinated bone, so that a part 
 above the latter is conducted to the regio olfactoria. Odorous bodies taken into 
 the mouth and then expired through the posterior nares are said not to be smelled 
 {Bidder). 
 
 During inspiration the air streams along close to the septum, while little of it passes through the 
 nasal passages, especially the superior {Paulsen and Exner). 
 
 'Wit, first moment of contact between the odorous body and the olfactory mucous 
 membrane appears to be the time when the sensation takes place, as, when we 
 wish to obtain a more exact perception, we sniff several times, i. <?,, a series of 
 rapid inspirations are taken, the mouth being kept closed. During sniffing, the 
 air within the nasal cavities is rarefied, and as air rushes in to equilibrate the 
 pressure, the air laden with odorous particles, streams over the olfactory region. 
 Odorous fluids are said not to give rise to the sensation of smell when they are 
 brought into direct contact with the olfactory mucous membrane, as by pouring 
 eau de Cologne into the nostrils ( Toitrtual, 1827 ; E. H. Weber, 1847). This is, 
 perhaps, due to the action of the fluid on the olfactory cells paralyzing them, per- 
 haps, owing to imbibition, shriveling, or chemical action. Even water alone 
 temporarily affects the cells. We know practically nothing about the nature of 
 the action of odorous bodies, but many odorous vapors have a considerable power 
 of absorbing heat {Tyndall). 
 
 The intensity of the sensation depends on — 1. The size of the olfactory 
 surface, as animals with a very keen sense of smell are found to have complex 
 turbinated bones covered by the olfactory mucous membrane. 2. The concen- 
 tration of the odorous mixture of the air. Still, some substances may be attenu- 
 ated enormously {e.g., musk to the two-millionth of a milligram), and still be 
 smelled. 3. The frequency of the conduction of the vapor to the olfactory cells 
 (sniffing). 
 
 I [The acuteness of the sense of smell is greatly improved by practice. A boy 
 named James Mitchell, who was deaf, dumb, and blind, used his sense of smell, 
 like a dog, to distinguish persons and things.] 
 
 Electrical, chemical, or thermal stimuli do not give rise to olfactory sensations. [Althaus found 
 that electrical stimulation of the olfactory mucous membrane gave rise to the sensation of the smell 
 of phosphorus.] 
 
 The variations are referred to in \ 343. If the two nostrils are filled with different odorous 
 substances there is no mixture of the odors, but we smell sometimes the one and sometimes the 
 other ( Valentin). The sense of smell, however, is very soon blunted, or even paralyzed. Mor- 
 phia, when mixed with a little sugar and, taken as snuff, paralyzes the olfactory apparatus, while 
 strychnin makes it more sensitive ( Lichtenfels and Frohlich). 
 
 The sensory nerves of the nasal mucous membrane (ji 347, II) [». e., those supplied from the 
 fifth cranial nerve] are stimulated by irritating vapors, and may even cause pain, e.g., ammonia and 
 acetic acid. In a very diluted condition.they may even act on the olfactory nerves. The nose is 
 useful as a sentinel for guarding against the introduction of disagreeable odors and foods. The 
 sense of smell is aided by the sense of taste, and conversely. 
 
 [Flavor depends on the sense of smell, and, to test it, use substances, solid or fluid, with an 
 aroma or bouquet, such as wine or roast beef.] 
 
 [Method of Testing. — In doing so, avoid the use of pungent substances like ammonia, which 
 excite the fifth nerve. Use some of the essential volatile oils, such as cloves, bergamot, and the fetid 
 gum resins, or musk and camphor. Electrical stimuli are not available. Action of Drugs, g 343.] 
 
 Comparative. — In the lowest vertebrata, pits, or depressions provided with an olfactory nerve, 
 represent the simplest olfactory organ. Amphioxus and the cyclostomata have only one olfactory 
 pit; all other vertebrates have two. In some animals ffrog),the nose communicates with the mouth 
 by ducts. The olfactory nerve is absent in the whale. > (p ^u^fe>i'< AJL 
 
 Historical. — Rufus Ephesius (97 a.d.) described the passage of the olfactory nerve through the 
 ethmoid bone. Rudius (1600) dissected the body of a man with congenital anosmia, in whom the 
 olfactory nerves were absent. Magendie originally supposed that the nasal branch of the fifth was 
 the nerve of smell, a view successfully combated by Eschricht. 
 
THE ORGAN OF TASTE. 
 
 422. STRUCTURE OF THE GUSTATORY ORGANS.— Gusta- 
 tory Region. — There is considerable difference of opinion as to what regions of 
 the mouth are endowed with taste : (1) The root of the tongue in the neighbor- 
 hood of the circumvallate papillae, the area of distribution of the glosso-pharyngeal 
 nerve, is undoubtedly endowed with taste (§ 351). (2) The tip and margins of 
 the tongue are gustatory, but there are very considerable variations ( Urbantschitsch). 
 (3) The lateral part of the soft palate and the glosso-palatine arch are endowed 
 with taste from the glosso-pharyngeal nerve. (4) It is uncertain whether the hard 
 palate and the entrance to the larynx are endowed with taste (Drielsmd). The 
 middle of the tongue is not gustatory. 
 
 Taste Bulbs. — The end organs of the gustatory nerves are the taste bulbs discovered by 
 Schwalbe and Loven (1867). They occur on the lateral surfaces of the circumvallate papillae (Fig. 
 535, I), also upon the opposite side, K, of the fossa or capillary slit, R R, which surrounds the 
 
 Fig. 535- 
 
 I, Transverse section of a circumvallate papilla ; W, the papilla : z^, v\, the wall in section ; R, R, the circular slit 
 or fossa ; K, K , the taste b-ulbs in position ; N, N, the nerves. II, Isolated taste bulbs ; D, supporting or pro- 
 tective cells : K. under end ; £, free end, open, with the projecting apices of the taste cells. Ill, Isolated pro- 
 tective cell (d) with a taste cell (e). 
 
 central eminence or papilla; they occur more rarely on the surface. They also occur on the fungi- 
 form papillae, in the papillae of the soft palate and uvula (A. Hoffman), on the under surface of the 
 epiglottis, the upper part of the posterior surface of the epiglottis, and the inner side of the arytenoid 
 cartilages ( Verson, Davis), and on the vocal cords (Siniimowsky). Many buds or bulbs disappear 
 in old age. 
 
 Structure. — The taste bulbs are 81 /i high and 33 ft thick, are barrel shaped and embedded in 
 the thick stratified squamous epithelium of the tongue. Each bulb consists of a series of lancet- 
 shaped, bent, nucleated, outer, supporting or protective cells, arranged like the staves of a barrel 
 (Fig. 53s, II, D, isolated in III, a). They are so arranged as to leave a small opening, or the 
 " gustatory pore " at the free enil of the bulb. Surrounded by the~e cells and lying in the axis of 
 the bud are 1 to 10 gustatory cells (II, E), some of which are provided with a delicate process 
 (III, e) at their free ends, while their lower fixed ends send out basal processes, which become 
 continuous with the terminations of the nerves of taste, which have become non medullated. After 
 section of the glosso pharyngeal, the taste buds degenerate, while the protective cells become changed 
 into ordinary epithelial cells within four months (v. Vinlschgau and Honigschmied '). Very similar 
 
 841 
 
842 GUSTATORY SENSATIONS. 
 
 structures were found by Leydig in the skin of fresh-water fishes. The glands of the tongue and 
 their secretory fibres from the 9th cranial nerve are referred to in \ 141 (Drasch). 
 
 423. GUSTATORY SENSATIONS.— Varieties.— There are four dif- 
 ferent gustatory qualities, the sensations of 
 
 1. Sweet. 3. Acid. 
 
 2. Bitter. 4. Saline. 
 
 Acid and saline substances at the same time also stimulate the sensory nerves of 
 the tongue, but when greatly diluted they only excite the end organs of the 
 specific nerves of taste. Perhaps there are special nerve fibres for each different 
 gustatory quality {v. Vintschgau). 
 
 Conditions. — Sapid substances, in order that they may be tasted, require the 
 following conditions : They must be dissolved in the fluid of the mouth, espe- 
 cially substances that are solid or gaseous. The intensity of the gustatory sen- 
 sation depends on : 1. The size of the surface acted on. Sensation is favored by 
 rubbing in the substance between the papillse, in fact, this is illustrated in the 
 rubbing movements of the tongue during mastication (§ 354). 2. The concen- 
 tration of the sapid substance is of great importance. Valentin found that the 
 following series of substances ceased to be tasted in the order here stated, as they 
 were gradually diluted — syrup, sugar, common salt, aloes, quinine, sulphuric acid. 
 Quinine can be diluted 20 times more than common salt and still be tasted (Cam- 
 erer). 3. The time which elapses between the application of the sapid substance 
 and the production of the sensation varies with different substances. Saline sub- 
 stances are tasted most rapidly (after 0.17 second, according to v. Vintschgau), 
 then sweet, acid and bitter (quinine after 0.258 second, v. Vintschgau). This even 
 occurs with a mixture of these substances (Schirmer). The last-named substances 
 produce the longest " after taste." 4.. The delicacy of the sense of taste is partly 
 congenital, but it can be greatly improved by practice. If a person uses the same 
 sapid substance, or a nearly related one, or even any very intensely sapid substance, 
 the sense of taste is soon affected, and it becomes impossible to give a correct 
 judgment as to the taste of the sapid body. 5. Taste is greatly aided by the sense 
 of smell, and in fact we often confound taste with smell ; thus vanilla, garlic, and 
 asafcetida only affect the organ of smell, while chloroform only excites taste. [The 
 combined action of taste and smell in some cases gives rise to flavor (p. 840). 
 The eye even may aid the determination, as in the experiment where in rapidly 
 tasting red and white wine one after the other, when the eyes are covered, we 
 soon become unable to distinguish between the one and the other. 6. The most 
 advantageous temperature for taste is between io°-35° C. ; hot and cold water 
 temporarily paralyze taste. 
 
 Action of the Electrical Current. — The constant current, when applied to the tongue, 
 excites, both during its passage and when it is opened or closed, a sensation of acidity at the -+- 
 pole, and at the — pole an alkaline taste, or, more correctly, a harsh, burning sensation [Sulzer, 
 1752). This is not due to the action of the electrolytes of the fluid in the mouth, for even when 
 the tongue is moistened with an acid fluid the alkaline sensation is experienced at the — pole 
 ( Volta). We cannot, however, set aside the supposition that perhaps electrolytes, or decomposi- 
 tion products, may be formed in the deeper parts and excite the gustatory fibres. Rapidly inter- 
 rupted currents do not excite taste (Griinhagen). V. Vintschgau, who has only incomplete taste 
 on the tip of the tongue, finds that when the tip of the tongue is traversed by an electrical current, 
 there is never a gustatory sensation, but always a distinct tactile one. In experiments on Honig. 
 schmeid, who is possessed of normal taste in the tip of the tongue, there was often a metallic or 
 acid taste at the -f- pole on the tip of the tongue, while at the — pole taste was often absent, and 
 when it was present it was almost always alkaline, and acid only exceptionally. After interrupting 
 the current there was a metallic after taste with both directions of the current. 
 
 [Testing Taste. — Direct the person to put out his tongue and close his eyes, 
 and after drying the tongue apply the sapid substance by means of a glass rod or 
 a small brush. Try to confine the stimulus as much as possible to one place, and 
 after each experiment rinse the mouth with water. A wine taster chews an olive 
 
PATHOLOGICAL COMPARATIVE HISTORICAL. 843 
 
 to "clean the palate," as he says. For testing bitter taste use a solution of 
 quinine or quassia ; for sweet sugar [or the intensely sweet substance " saccharine ' ' 
 obtained from coal tar] ; saline, common salt ; and acid, dilute citric or acetic 
 acid. The galvanic current may also be used.] 
 
 Pathological. — Diseases of the tongue, as well as dryness of the mouth caused by interference 
 with the salivary secretion, interfere with the sense of taste. Subjective gustatory impressions 
 are common among the insane, and are due to some central cause, perhaps to irritation of the 
 psychogeusic centre (§ 378, IV, 3). After poisoning with santonin a bitter taste is experienced, 
 while after the subcutaneous injection of morphia there is a bitter and acid taste. The terms 
 hypergeusia, hypogeusia and ageusia are applied to the increase, diminution and abolition of 
 the sense of taste. Many tactile impressions on the tongue are frequently confounded with gusta- 
 tory sensations, e.g., the so-called biting, cooling, prickling, sandy, mealy, astringent and harsh 
 tastes. 
 
 Comparative. — About 1760 taste bulbs occur on the circumvallate papillae of the ox. The 
 term papilla foliata is applied to a large folded gustatory organ placed laterally on the side of the 
 tongue, especially of the rabbit {Rapp, 1832), and which in man is represented by analogous 
 organs, composed of longitudinal folds, lying in the fimbria; linguae on each side of the posterior 
 part of the tongue (JCrause, v. Wyss). Taste bulbs are absent in reptiles and birds. They are 
 numerous in the mouth of the tadpole (F. E. Schultze), while the tongue of the frog is covered 
 with epithelium resembling gustatory cells {Billroth, Axel Key). The goblet shaped organs in the 
 skin of fishes and tadpoles have a structure similar to the taste bulbs, and may perhaps have the 
 same function. There are taste bulbs in the mouth of the carp and ray. 
 
 Historical. — Bellini regarded the papillne as the organs of taste (171 1 ). Richerand, Mayo and 
 Fodera thought that the lingual was the only nerve of taste, but Magendie proved that, after it was 
 divided, the posterior part of the tongue was still endowed with taste. Panizza (1834) described 
 the glosso-pharyngeal as the nerve of taste, the gustatory as the nerve of touch, and the hypoglossal 
 as the motor nerve of the tongue. 
 
THE SENSE OF TOUCH. 
 
 424 TERMINATIONS OF SENSORY NERVES.— 1. The touch corpuscles of 
 Wagner and Meissner lie in the papillae of the cutis vera (g 283), and are most numerous in 
 the palm of the hand and the sole of the foot, especially in the fingers and toes, there being about 
 21 to every square millimetre of skin, or 108 to 400 of the papillae containing blood vessels. They 
 are less abundant on the back of the hand and foot, mamma, lips and tip of the tongue, rare on 
 the glans clitoridis, and occur singly and scattered on the volar side of the fore arm, even in the 
 anthropoid apes. They are oval or elliptical bodies, 40-200 n long [^ J ff in.] , and 60-70 fi broad 
 [ 3 J^ to yj 5 in.], and are covered externally by layers of connective tissue arranged transversely in 
 layers, and within is a granular mass with elongated striped nuclei (Figs. 536, 537, e). One to three 
 medullated nerve fibres pass to the lower end of each corpuscle, and surround it in a spiral manner 
 
 Fig. 537. 
 
 Fig. 536 
 
 Hill 
 
 %~a 
 
 Fig. 536. — Wagner's touch corpuscle from the palm, treated with gold chloride, «, nerve fibres 
 glomeruli. Fig. 537. — Vertical section of the skin of the palm -of the hand. 
 
 a, blood vessel , 
 
 . groups ot 
 £, papilla of the 
 
 .^7-- . 
 
 cutis vera; c, capillary; d f nerve fibre passing to a touch corpuscle; f, nerve fibre divided transversely; 
 Wagner's touch corpuscle ; g, cells of the Malpighian layer of the skin. ' 
 
 two or three times ; the fibres then lose their myelin, and after dividing into 4 to 6 fibrils, divide 
 within the corpuscle. The exact mode of termination of the fibrils is not known. Some observers 
 suppose that the transverse fibrillation is due to the cojjs or windings of the nerve fibrils ; while, 
 according to others, the inner part consists of numerous flattened cells lying one over the other, 
 between which the pale terminal fibres end either in swellings or with disk-like expansions, such as 
 occur in Merkel's corpuscles. 
 
 [These corpuscles do not contain a soft core such as exists in Pacini's corpuscles. The corpuscles 
 appear to consist of connective tissue with imperfect septa passing into the interior from the fibrous 
 capsule. After the nerve fibre enters it loses its myelin, and then branches, while the branches 
 anastomose and follow a spiral course within the corpuscle, finally to terminate in slight enlarge- 
 
 844 
 
TERMINATIONS OF SENSORY NERVES. 
 
 845 
 
 Fig. 538. 
 
 ments. According to Thin, there are simple and compound corpuscles, depending on the number 
 of nerve fibres entering them.] 
 
 Kollmann describes three special tactile areas in the hand: (1) The tips of the fingers with 
 24 touch corpuscles in a length of 10 mm. ; (2) the three eminences lying on the palm 
 behind the slits between the fingers, with 5.4-2.7 touch corpuscles in the same length ; and 
 (3) the ball of the thumb and little finger with 3.1-3 5 touch corpuscles. The first two areas 
 also contain many of the corpuscles of Vater or Pacini, while in the latter these corpuscles 
 are fewer and scattered. In the other parts of the hand the nervous end organs are much 
 less developed. 
 
 2. Vater's (1741) or Pacini's corpuscles are oval bodies (Fig. 538), 1-2 mm. long, lyinp in 
 the subcutaneous tissue on the nerves of the fingers and toes (600-1400), in the neighborhood of 
 joints and muscles, the sympathetic abdominal plexuses, near the aorta and coccygeal gland, on the 
 dorsum of the penis and clitoris, and in the mesocolon [and mesentery] of the cat. [They also 
 occur in the course of the intercostal and periosteal nerves, and 
 Stirling has seen them in the capsule of lymphatic glands. 
 They are attached to the nerves of the hand and feet, and are 
 so Urge as to be visible to the naked eye, both in these regions 
 ar.d between the layers of the mesentery of the cat. They are 
 whitish or somewhat transparent, with a white line in the 
 centre (cat) ; in man, they are ^ to ^ inch long, and -j*- to 
 ■fe inch broad, and are attached by a stalk or pedicle (Fig. 
 538, a) to the nerve.] They consist of numerous nucleated 
 connective-tissue capsules or lamellae lined by endothelium 
 separated from each other by fluid, and lying one within the 
 other like the coats of an onion, while in the axis is a central 
 cere. A medullated nerve fibre passes to each, where its 
 sheath of Schwann unites with the capsule. It loses its myelin, 
 and passes into the interior as an axial cylinder (Fig. 538, e), 
 where it either ends in a small knob or may divide dichoto- 
 mously (Fig. 538,7°), each branch terminating in a small pear- 
 shaped enlargement. [Each large corpuscle is covered by 
 40-50 lamellae, or tunics, which are thinner and closer to 
 each other (Fig. 538, d) internally than in the outer part, 
 where they are thicker and wider apart. The lamellae are 
 like the laminae in the lamellated sheath of a nerve, and are 
 composed of an elastic basis mixed with white fibres of con- 
 nective tissue, while the inner surface of each lamella is lined 
 by a single continuous layer of endothelium continuous with 
 that of the perineurium. It is easily stained with silver nitrate. 
 The efferent nerve fibre is covered with a thick sheath of 
 lamellated connective tissue (sheath of Henle), which be- 
 comes blended with the outer lamellae of the corpuscle. The 
 medullated nerve is sometimes accompanied by a blood vessel, 
 and pierces the various tunics, retaining its myelin until it 
 reaches the core, where it terminates as already described. 
 
 3. Krause's end bulbs very probably occur as a regular 
 mode of nerve termination in the cutis and mucous membrane 
 of all mammals. They are elongated, oval, or round bodies, 
 0.075 to 0>I 4 mm - ' on g> an d nav ^ been f° un( 3 m tne deeper 
 layers of the conjunctiva bulbi, floor of the mouth, margins of 
 the lips, nasal mucous membrane, epiglottis, fungiform and cir- 
 cumvallate papillae, glans penis and clitoris, volar surface of 
 the toes of the guinea pig, ear and body of the mouse, and in 
 the wing of the bat. [In the calf, the " cylindrical end 
 bulbs " are oval, with a nerve fibre terminating within them. 
 The sheath of Henle becomes continuous with the nucleated 
 capsule, while the axial cylinder, devoid of its myelin, is con- 
 tinued into the soft core. In man the end bulbs are "spheroidal," 
 and consist of a nucleated connective tissue capsule continuous with Henle's sheath of the nerve, 
 and enclosing many cells, among which the axis cylinder which enters the bulb branches and ter- 
 minates.] The spheroidal and end bulbs occur in man, in the nasal mucous membrane, conjunctiva, 
 mouth, epiglottis, and the mucous folds of the rectum. According to Waldeyer and Longworth, 
 the nerve fibrils terminate in the cells within the capsule. These cells are said to be comparable t> 
 Merkel's tactile cells {Waldeyer). 
 
 The genital corpuscles of Krause, which occur in the skin and mucous membrane of the glans 
 penis, clitoris, and vagina, appear to be end bulbs more or less fused together. 
 
 The articulation nerve corpuscles occur in the synovial mucous membrane of the joints of the 
 
 Vater's or Pacini's corpuscle, a, stalk ; 
 b f nerve fibre entering it; c,d, con- 
 nective-tissue envelope ; e. axis cylin- 
 der, with its end divided at/*. 
 
846 
 
 SENSORY AND TACTILE SENSATIONS. 
 
 fingers. They are larger than the end bulbs, and have numerous oval nuclei externally, while one 
 to four nerve fibres enter them. 
 
 4. Tactile or touch corpuscles of Merkel, sometimes also called the corpuscles of Grandry, 
 occur in the beak and tongue of the duck and goose, in the epidermis of man and mammals, and 
 in the outer root sheath of tactile hairs or feelers. They are small bodies, composed of a capsule 
 enclosing two, three or more large, granular, somewhat flattened nucleated and nucleolated cells, 
 piled one on the other in a vertical row, like a row of cheeses. Each corpuscle receives at one side 
 a medullated nerve fibre, which loses its myelin, and branches, to terminate, according to some 
 observers (Merkel), in the cells themselves, and according to others (Ranvier, Izquierdo, Hesse), 
 in the protoplasmic transparent substance or disk lying between the cells. [This intercellular disk 
 is the " disk tactil " of Ranvier, or the " Tastplatte" of Hesse.] When there is a great aggregation 
 of these cells, large structures are formed, which appear to form a kind of transition between these 
 and touch corpuscles. [According to Klein, the terminal fibrils end neither in the touch cells nor 
 tactile disk, but in minute swellings in the interstitial substance between the touch cells, in a manner 
 very similar to that occurring in the end bulbs.] 
 
 [According to Merkel, tactile cells, either isolated or in groups, but in the latter case never form- 
 ing an independent end organ, occur in the deeper layers of the epidermis of man and mammals, 
 and also in the papillae. They consist of round or flask -shaped cells, with the lower pointed neck 
 of the flask continuous with the axis cylinder of a nerve fibre. They are regarded by Merkel as 
 the simplest form of a tactile end organ, but their existence is doubted by some observers.] 
 
 Among animals there are many other forms of sensory end organs. [Herbst's corpuscles 
 occur in the mucous membrane of the tongue of the duck, and resemble small Vater's corpuscles, 
 but their lamellae are thinner and nearer each other, while the axis cylinder within the central core 
 
 Bouchon epidermique from the groin of a guinea pig, after the action of gold chloride. 
 
 m, tactile disks ; c, epithelial cells. 
 
 n, nerve fibre ; a, tactile cells; 
 
 is bordered on each side by a row of nuclei.] In the nose of the mole there is a peculiar end 
 organ (Eimer), while there are "end capsules" in the penis of the hedgehog and the tongue of 
 the elephant, and " nerve rings" in the ears of the mouse. 
 
 5. [Other Modes of Ending of Sensory Nerves. — Some sensory nerves terminate not by 
 means of special end organs, but their axis cylinder splits up into fibrils to form a nervous network, 
 from which fine fibrils are given off to terminate in the tissue in which the nerve ends. These fibrils, 
 as in the cornea (\ 384), terminate by means of free ends between the epithelium on the anterior 
 surface of the cornea, and some observers state that the free ends are provided with small enlarge- 
 ments ("boutons terminals") (Fig. 539,a). These enlargements or " tactile cells " occur in the 
 groin of the guinea pig and mole. A similar mode of termination occurs between the cells of the 
 epidermis in man and mammals (Fig. 271).] 
 
 6. Tendons, especially at their junction with muscles, have special end organs {Sacks, Rollctt, 
 Golgi), which assume various forms; it may be a network of primitive nerve fibrils, or flattened 
 end flakes or plates in the sterno-radial muscle of the frog, or elongated oval end bulbs, not unlike 
 the end bulbs of the conjunctiva, or small simple, Pacinian corpuscles.] 
 
 425. SENSORY AND TACTILE SENSATIONS.— In the sensory 
 nerve trunks there are two functionally different kinds of nerve fibres: (1) Those 
 which administer to painful impressions, which are sensory nerves in the narrower 
 sense of the word ; and (2) which administer to tactile impressions, and may, 
 therefore, be called tactile nerves. The sensations of temperature and pressure are 
 also reckoned as belonging to the tactile group. It is extremely probable that the 
 
THE SENSE OF LOCALITY. 847 
 
 sensory and tactile nerves have different end organs and fibres, and that they have 
 also special perceptive nerve centres in the brain, although this is not definitely 
 proved. This view, however, is supported by the following facts: — 
 
 i. That sensory and tactile impressions cannot be discharged at the same time 
 from all the parts which are endowed with sensibility. Tactile sensations, in- 
 cluding pressure and temperature, are only discharged from the coverings of the 
 skin, the mouth, the entrance to and floor of the nose, the pharynx, the lower 
 end of the rectum and genito-urinary orifices ; feeble, indistinct sensations of tem- 
 perature are felt in the oesophagus. Tactile sensations are absent from all internal 
 viscera, as has been proved in man in cases of gastric, intestinal and urinary 
 fistulae. Pain alone can be discharged from these organs. 2. The conduction 
 channels of the tactile and sensory nerves lie in different parts of the spinal cord 
 (§ 364, 1 and 5). This renders probable the assumption that their central and 
 peripheral ends also are different. 3. Very probably the reflex acts discharged 
 by both kinds of nerve fibres — the tactile and pathic — are controlled, or even 
 inhibited, by special central nerve organs (§ 361 — ?). 4. Under pathological 
 conditions, and under the action of narcotics, the one sensation may be suppressed 
 while the other is retained (§ 364, 5). 
 
 Sensory Stimuli. — In order to discharge a painful impression from sensory 
 nerves, relatively strong stimuli are required. The stimuli may be mechanical, 
 chemical, electrical, thermal, and somatic, the last being due to inflammation or 
 anomalies of nutrition and the like. 
 
 Peripheral Reference of the Sensations. — These nerves are excitable 
 along their entire course, and so is their central termination, so that pain may 
 be produced by stimulating them in any part of their course ; but this pain, 
 according to the "law of peripheral perception," is always referred to 
 the periphery. 
 
 The tactile nerves can only discharge a tactile impression or sensation of con- 
 tact when moderately strong mechanical pressure is exerted, while thermal stimuli 
 are required to produce a temperature sensation ; and in both cases the results are 
 obtained only when the appropriate stimuli are applied to the end organs. If 
 pressure or cold be applied to the course of a nerve trunk, e. g., to the ulna at the 
 inner surface of the elbow joint, we are conscious of painful sensations, but never 
 of those of temperature, referable to the peripheral terminations of the nerves in 
 the inner fingers. All strong stimuli disturb normal tactile sensations by over- 
 stimulation, and hence cause pain. 
 
 426. THE SENSE OF LOCALITY.— We are not only able to distin- 
 guish differences of pressure or temperature by our sensory 
 nerves, but we are able to distinguish the part which has been Fig. 540. 
 
 touched. This capacity is spoken of as the sense of space or 
 locality. 
 
 Methods of Testing. — Place the two blunted points of a pair of com- 
 passes (Fig. 540) upon the part of the skin to be investigated, and determine 
 the smallest distance at which the two points are felt only as one impression. 
 Sieveking's aesthesiometer (Fig. 541) may be used instead; one of the 
 points is movable along a graduated rod, while the other is fixed. 2. The 
 distance between the points of the instrument being kept the same, touch 
 several parts of the skin, and ask if the person feels the impression of the 
 points coming nearer to or going wider apart. 3. Touch a part of the skin 
 with a blunt instrument, and observe if the spot touched is correctly indicated 
 by the patient. 
 
 The investigations have led to the following results : The 
 sense of locality of a part of the skin is more acute under the 
 following conditions : 
 
 1. The greater the number of tactile nerves in the correspond- ' ^sthesiometer 
 ing part of the skin. 
 
848 
 
 MODIFYING CONDITIONS. 
 
 2. The greater the mobility of the part, so that it increases in the extremities 
 toward the fingers and toes. The sense of locality is always very acute in parts 
 of the body that are very rapidly moved ( Vierordt). 
 
 3. The sensibility of the limbs is finer in the transverse axis than in the long 
 axis of the limb, to the extent of y& on the flexor surface of the upper limb, 
 and % on the extensor surface. 
 
 4. The mode of application of the points of the sesthesiometer : (a) According 
 as they are applied one after the other, instead of simultaneously, or as they are 
 considerably warmer or colder than the skin {Klug), a person may distinguish a 
 less distance between the points, (a) If we begin with the points wide apart and 
 approximate them, then we can distinguish a less distance than when we proceed 
 from imperceptible distances to larger ones, (c) If the one point is warm and the 
 other cold, on exceeding the next distance we feel two impressions, but we cannot 
 rightly judge of their relative positions (Czermak). 
 
 5. Exercise greatly improves the sense of locality ; hence the extraordinary 
 acuteness of this sense in the blind, and the improvement always occurs on both 
 sides of the body ( Volkmanri). 
 
 [Fr. Galton finds that the reputed increased acuteness of the other senses in the case of the blind 
 is not so great as is generally alleged. He tested a large number of boys at an educational blind 
 asylum, with the result that the performances of the blind boys were by no means superior to those 
 
 Fie. 541. 
 
 /Esthesiometer of Sieveking. 
 
 of other boys. He points out, however, that " the guidance of the blind depends mainly on the 
 multitude of collateral indications, to which they give much heed, and not in their superiority to any 
 one of them."] 
 
 6. Moistening the skin with indifferent fluids increases the acuteness. If, how- 
 ever, the skin between two points, which are still felt as two distinct objects, be 
 slightly tickled, or be traversed by an imperceptible electrical current, the im- 
 pressions become fused (Suslowd). The sense of locality is rendered more acute 
 at the cathode when a constant current is used (Suslowa), and when the skin is 
 congested by stimulation {Klinkenberg), and also by slight stretching of the skin 
 (JSchmey) ; further, by baths of carbonic acid {v. Basch and v. Dietl), or warm 
 common salt, and temporarily by the use of caffein (Jiumpf). 
 
 7. Ancemia, produced by elevating the limbs, or venous hyperemia (by com- 
 pressing the veins), blunts the sense, and so does too frequent testing of the sense 
 of locality, by producing fatigue. The sense is also blunted by cold applied to 
 the skin, the influence of the anode, strong stretching of the skin, as over the ab- 
 domen during pregnancy, previous exertion of the muscles under the part of the 
 skin tested, and some poisons, e. g., atropin, daturin, morphin, strychnin, alcohol, 
 potassium bromide, cannabin, and chloral hydrate. 
 
 Smallest Appreciable Distance. — The following statement gives the 
 smallest distance, in millimetres, at which two points of a pair of compasses can 
 
jESTHESIOMETRY. 
 
 849 
 
 still be distinguished as double by an adult. The corresponding numbers for a 
 boy twelve years of age are given within brackets : — 
 
 Millimetres. 
 
 Eyelid 11.3 [9.] 
 
 Centre of hard palate 13.5 [11.3] 
 
 Lower third of the forearm, volar 
 surface 15. 
 
 [i-7] 
 L3-9] 
 
 [3-9] 
 
 Millimetres. 
 
 Tip of tongue 1.1 [1.1] 
 
 Third phalanx of finger, volar 
 
 surface 2.-2.3 
 
 Red part of the lip 4.5 
 
 Second phalanx of finger, volar 
 
 surface 4.-4-5 
 
 First phalanx of finger, volar 
 
 surface '. . 5.-5.5 
 
 Third phalanx of finger, dorsal 
 
 surface 6.8 
 
 Tip of nose 6.8 
 
 Head of metacarpal bone, volar . 5--. 6. 8 
 
 Ball of thumb 6.5-7. 
 
 Ball of little finger 5.5-6. 
 
 Centre of palm 8.-9. 
 
 Dorsum and side of tongue, white 
 
 of the lips, metacarpal part of 
 
 the thumb 9. 
 
 Third phalanx of the great toe, 
 
 plantar surface 1 1 .3 [6.8] 
 
 Second phalanx of the fingers, 
 
 A-S. 
 
 "4-5; 
 4-5; 
 
 [6.8] 
 
 In front of the zygoma 15.8 [11.3] 
 
 Plantar surface of the great toe . . 15.8 [9.] 
 
 Inner surface of the lip 20.3 [13.5] 
 
 Behind the zygoma 22.6 15.8] 
 
 Forehead 22.6 18.] . 
 
 Occiput 27.1 '22.6 
 
 Back of the hand 31.6 [22.6 
 
 Under the chin 33.8 22.6 
 
 Vertex 33.8 [22.6 
 
 Knee 36.1 31.6 
 
 Sacrum, gluteal region 44.6 [33.8 
 
 Porearm and leg 45.1 33. 8_ 
 
 Neck 54.1 [36.1° 
 
 Back at the fifth dorsal vertebra, 
 
 lower dorsal and lumbar region . 54. 1 
 
 Middle of the neck 67.7 
 
 Upper arm, thigh and centre of the 
 
 back 67.7 [31.6-40.6] 
 
 dorsal surface 1 1 .3 [9.] 
 
 Back 1 1.3 [9.] 
 
 Illusions of the sense of locality occur very frequently ; the most marked are: (1) A uni- 
 form movement over a cutaneous surface appears to be quicker in those places which have the 
 finest sense of locality. (2) If we merely touch the skin with the two points of an sesthesiometer, 
 then they feel as if they were wider apart than when the two points are moved along the skin 
 (Feckner), (3) A sphere, when touched with short rods, feels larger than when long rods are 
 used ( Tourtual). (4) When the fingers of one hand are crossed, a small pebble or sphere placed 
 between them feels double (Aristotle's experiment). [When a pebble is rolled between the 
 crossed index and middle finger (Fig. 542, B), it feels as if two balls were present, but with the 
 fingers uncrossed single. (5) When pieces of skin are transplanted, e.g., from the forehead, to form 
 a nose, the person operated on feels, often for a long time, the new nasal part as if it were his fore- 
 head.] 
 
 Theoretical. — Numerous experiments were made by E. H. Weber, Lotze, Meissner, Czermak 
 and others, to explain the phenomena of the 
 
 sense of space. Weber's theory goes Fig. 542. 
 
 upon the assumption, that one and the same 
 nerve fibre proceeding from the brain to the 
 skin can only take up one kind of impres- 
 sion, and administer thereto. He called the 
 part of the skin to which each single nerve 
 fibre is distributed a. " circle of sensa- 
 tion." When two stimuli act simultaneously 
 upon the tactile end organ, then a double 
 sensation is felt, when one or more circles of 
 sensation lie between the two points stimu- 
 lated. This explanation, based upon ana- 
 tomical considerations, does not explain how 
 it is that, with practice, the circles of sensa- 
 tion become smaller, and also how it is that 
 only one sensation occurs, when both points 
 of the instrument are so applied, that both 
 points, although further apart than the di- 
 ameter of a circle of sensation, at one time Aristotle's experiment, 
 lie upon two adjoining circles, at another 
 between two others with another circle intercalated between them. 
 
 Wundt's Theory. — In accordance with the conclusions of Lotze, Wundt proceeds from a 
 psycho-physiological basis, that every part of the skin with tactile sensibility always conveys to the 
 brain the locality of the sensation. Every cutaneous area, therefore, gives to the tactile sensation a 
 " local color " or quality, which is spoken of as the " local sign." He assumes that this local color 
 diminishes from point to point of the skin. This gradation is very sudden in those parts of the 
 skin where the sense of space is very acute, but occurs very gradually where the sense of space is 
 
 54 
 
 B. 
 
850 
 
 THE PRESSURE SENSE. 
 
 more obtuse. Separate impressions unite into a common one, as soon as the gradation of the local 
 color becomes imperceptible. By practice and attention differences of sensation are experienced, 
 which ordinarily are not observed, so that he explains the diminution of the circles of sensation by 
 practice. The circle of sensation is an area of the skin, within which the local color of the sensa- 
 tion changes so little that two separate impressions fuse into one. 
 
 427. THE PRESSURE SENSE.— By the sense of pressure we obtain a 
 knowledge of the amount of weight or pressure which is being exercised at the 
 time on the different parts of the skin. 
 
 Methods. — 1. Place, on the part of the skin to be investigated, different weights, one after the 
 other, and ascertain what perceptions they give rise to, and the sense' of the difference of pressure 
 to which they give rise. We must be careful to exclude differences of temperature and prevent the 
 displacement of the weights — the weights must always be placed on the same spot, and the skin 
 should be covered beforehand with a plate, while the muscular sense must be eliminated ({} 430). 
 
 Fig. 543. 
 
 D 
 
 Landois' mercurial balance for testing the pressure sense. 
 
 [This is done by supporting the hand or part of the skin which is being tested, so that the action 
 of all the muscles is excluded.] 2. A process is attached to a balance and made to touch the skin, 
 while by placing weights in the scale pan or removing them, we test what differences in weight the 
 person experimented on is able to distinguish (Do&rn). 3. In order to avoid the necessity of 
 changing the weights, A. Eulenberg invented his baraesthesiometer, which is constructed on the 
 same principle as a spiral spring paper clip or balance. There is a small button which rests on the 
 skin and is depressed by the spring. An index shows at once the pressure in grammes, and the 
 instrument is so arranged that the pressure can be very easily varied. 4. Goltz uses a pulsating 
 elastic tube, in which he can produce waves of different height. He tested how high the latter 
 must be before they are experienced as pulse waves, when the tube is placed upon the skin. 5- 
 Landois uses a mercurial balance (Fig. 543). The beam of a balance (W) moves upon two 
 knife edges (O, O), and is carried on the horizontal arm (b) of a heavy support (T). One arm of 
 the beam is provided with a screw (m) on which an equilibrating weight (S) can be moved. The 
 
RESULTS OF THE PRESSURE SENSE. 851 
 
 other arm (<a?) passes into a vertical calibrated tube (R). Below this is the pressure pad (P), which 
 can be loaded as desired by a weight (G), and which can be placed upon the part of the skin to be 
 tested (H). From an adjoining burette (B) held in a clamp (A), mercury can pass through a tube 
 in the direction of the arrows, to one part of the balance and into the tube (R). On the stop-cock 
 (h) being closed, whenever pressure is exerted on the tube (D, D),the mercury rises through i/into 
 R, and increases the pressure on P. We measure the weight of the mercury corresponding to each 
 division of the tube (R). This instrument enables rapid variations of the weight to be made with- 
 out giving rise to any shock. In estimating both the pressure sense and temperature sense, it is best 
 to proceed on the principle of " the least perceptible difference," i.e., the different pressures or tem- 
 peratures are graduated, either beginning with great differences, or proceeding from the smallest 
 difference, and determining the limit at which the person can distinguish a difference in the sensa- 
 tion. 
 
 Results. — i. The smallest perceptible pressure, when applied to different parts 
 of the skin, varies very greatly according to the locality. The greatest acuteness 
 of sensibility is on the forehead, temples, and the back of the hand and forearm, 
 which perceive a pressure of 0:002 grm. ; the fingers first feel with a weight of 
 0.005 t0 °- OI S g rm - > tne chin, abdomen, and nose with 0.04 to 0.05 grm. ; the 
 finger nail 1 grm. {Kammler and Auberf). 
 
 The greater the sensibility of the skin, the more rapidly can single stimuli succeed each other, 
 and still be perceived as single impressions; 52 stimuli per second may be applied to the volar side 
 of the upper arm, 61 on the back of the hand, 70 to the tips of the fingers, and still be felt singly 
 {Block). 
 
 2. Intermittent variations of pressure, as in Goltz's tube, are felt more acutely 
 by the tips of the fingers than with the forehead. 
 
 3. Differences between two weights are perceived by the tips of the fingers when 
 the ratio is 29 : 30 (in the fore arm as 18.2 : 20), provided the weights are not 
 too light or too heavy, In passing from the use of very light to heavy weights, 
 the acuteness or fineness of the perception of difference increases at once, but 
 with heavier weights, the power of distinguishing differences rapidly diminishes 
 again (E. Hering, Lmwit, and Biedermann). This observation is at variance with 
 the psycho-physical law of Fechner (§ 383). 
 
 4. A. Eulenberg found the following gradations in the fineness of the pressure 
 sense : The forehead, lips, dorsum of the cheeks, and temples appreciate differ- 
 ences of -fo to -fa (200 : 205 to 300 : 310 grm.). The dorsal surface of the last 
 phalanx of the fingers, the fore arm, hand, 1st and 2d phalanx, the volar surface 
 of the hand, fore arm, and upper arm, distinguishes differences of ^ to -^ (200 : 
 220 to 220 : 210 grm.). The anterior surface of the leg and thigh are similar to 
 the fore arm. Then follow the dorsum of the foot and toes, the sole of the foot, 
 and the posterior surface of the leg and thigh. Dohrn determined the smallest 
 additional weight, which, when added to 1 grm. already resting on the skin, was 
 appreciated as a difference, and he found that for the 3d phalanx of the finger it 
 was .499 grm. ; back of the foot, 0.5 grm. ; 2d phalanx, 0.771 grm. ; 1st pha- 
 lanx, 0.02 grm. ; leg, 1 grm. ; back of the hand, 1.156 grm. ; palm, 1.018 grm. ; 
 patella, 1.5 grm.; fore arm, 1.99 grm.; umbilicus, 3.5 grms. ; and the back, 
 3 .8grms. 
 
 5. Too long time must not elapse between the application of two successive 
 weights, but 100 seconds may elapse when the difference between the weights is 
 4 : 5 (£. H. Weber). 
 
 6. The sensation of an after pressure is very marked, especially if the weight 
 is considerable and has been applied for a length of time. But even light weights, 
 when applied, must be separated by an interval of at least -^ to -gfo second, in 
 order to be perceived. When they are applied at shorter intervals, the sensations 
 become fused. When Valentin pressed the tips of his fingers against a wheel 
 provided with blunt teeth he felt the impression of a smooth margin, when the 
 teeth were applied to the skin at the intervals above mentioned ; when the wheel 
 was rotated more slowly, each tooth gave rise to a distinct impression. Vibrations 
 
852 RESULTS OF THE TEMPERATURE SENSE. 
 
 of strings are distinguished as such when the number of vibrations is 1506 to 1552 
 per second (v. Wittich and Grunhageri). 
 
 7. It is remarkable that pressure produced by the uniform compression of a part 
 of the body, e.g., by dipping a finger or arm in mercury, is not felt as such ; the 
 sensation is felt only at the limit of the fluid, on the volar surface of the finger, at 
 the limit of the surface of the mercury. 
 
 428. THE TEMPERATURE SENSE.— The temperature sense makes 
 us acquainted with the variations of the heat of the skin. The circumstance de- 
 termining the sensation of temperature is, according to E. Hering, the tempera- 
 ture of the thermal end organs themselves. As often as any part of the skin has 
 a temperature above its zero, i. e., its neutral proper temperature, we feel warm ; 
 in the opposite condition we feel cold. The one or the other sensation becomes 
 stronger the more the temperature of the thermal end organ differs from its zero 
 temperature. The zero temperature, however, may vary pretty rapidly from ex- 
 ternal causes within certain limits. 
 
 Methods. — To the surface of the skin objects of the same size and with the same thermal con- 
 ductivity are applied successively at different temperatures: 1. Nothnagel uses small wooden cups 
 with a metallic base, and filled with warm and cold water, the temperature being registered by a 
 thermometer placed in the cups. [2. Clinically, two test tubes filled with cold and warm water, 
 or two spoons, the one hot and the other cold, may be used.] 
 
 Results. — 1. As a general rule, the feeling of cold is produced when a body 
 applied to the skin robs it of heat ; and, conversely, we have a sensation of warmth 
 when heat is communicated to the skin. 
 
 2. The greater the thermal conductivity of the substance touching the skin, the 
 more intense is the feeling of heat or cold (§ 218). 
 
 3. At a temperature of iS.5°-3S° C., we distinguish distinctly differences of 
 temperature of o.2°-o.i6° R. with the tips of the fingers {£. H. Weber). Tem- 
 peratures just below that of the blood (33°-2 7° C. — Nothnagel) are distinguished 
 most distinctly by the most sensitive parts, even to differences of 0.05 C. (Lin- 
 dermanri). Differences of temperature are less easily made out when dealing with 
 temperatures of 33°-39° C, as well as between i4°-27° C. A temperature of 
 55° C, and also one a few degrees above zero, cause distinct pain in addition to 
 the sensation of temperature: 
 
 4. The different parts of the skin also vary in the acuteness of their thermal 
 sense, and in the following order : Tip of the tongue, eyelids, cheeks, lips, neck, 
 and body. The perceptible minimum Nothnagel found to be 0.4 on the breast; 
 0.9 on the back ; 0.3°, back of the hand ; 0.4 , palm ; 0.2 , arm ; 0.4 back of 
 the foot; 0.5°, thigh; o.6° leg; o.4°-o.2°, cheek; o.4°-o.3° C, temple. The 
 thermal sense is less acute in the middle line, e.g., the nose, than on each side of 
 it {E. H. Weber). 
 
 5. Differences of temperature are most easily perceived when the same part of 
 the skin is affected successively by objects of different temperature. If, however, 
 two different temperatures act simultaneously and side by side, the impressions are 
 apt to become fused, especially when the two areas are very near each other. 
 
 [Goldschneider finds that when two cold or two warm cylinders are applied to the skin, the 
 sensation of heat and cold can be appreciated as double at exceedingly small distances apart, e.g., 
 cold to the forehead, cheek, or chin at 0.8 mm. apart, palm of the little finger 0.1 mm.] 
 
 6. Practice improves the temperature sense; congestion of venous blood in the 
 skin diminishes it ; diminution of the amount of blood in the skin improves it {M. 
 Alsberg). When large areas of the skin are touched, the perception of differences 
 is more acute than with small areas. Rapid variations of temperature produce 
 more intense sensations than gradual changes of temperature. 
 
 [Goldschneider asserts that there are special cutaneous nerves, some of which administer only to 
 the sensation of cold, and others for that of heat, others for pressure, and, lastly, those for touch. In 
 the " cold points " of the skin, when gently touched with a cold conical metal cylinder, only the 
 
COMMON SENSATION — PAIN. 853 
 
 sensation of cold is felt, and in the " heat points " only heat, while such points are insensible to a 
 gentle touch. The sensation of cold occurs at once, that of heat gradually increases, and is more 
 diffuse. Pain cannot be discharged from these " temperature points." 
 
 Illusions are very common : I. The sensations of heat and cold sometimes alternate in a para- 
 doxical manner. When the skin is dipped first into water at io° C. we feel cold, and if it be then 
 dipped at once into water at l6° C. we have at first a feeling of warmth, but soon again of cold. 
 2. The same temperature applied to a large surface of the skin is estimated to be greater than when 
 it is applied to a small area, e.g., the whole hand when placed in water at 29.5 C. feels warmer 
 than when a finger is dipped into water at 32 C. 3. Cold weights are judged to be heavier than 
 warm ones. 
 
 Pathological. — Tactile sensibility is only seldom increased (hyperpselaphesia), but great sen- 
 sibility to differences of temperature is manifested by areas of the skin whose epidermis is partly 
 removed or altered by vesicants or herpes zoster, and the same occurs in some cases of locomotor 
 ataxia ; while the sense of locality is rendered more acute in the two former cases and in erysipelas. 
 An abnormal condition of the sense of locality was described by Brown- Sequard, where three points 
 were felt when only two were applied, and two when one was applied to the skin. Landois finds 
 that in himself pricking the skin of the sternum over the angle of Ludovicus is always accompanied 
 by a sensation in the knee. [Some persons, when cold water is applied to the scalp, have a sensa- 
 tion referable to the skin of the loins (Stirling).'] A remarkable variation of the sense of locality 
 occurs in moderate poisoning with morphia, where the person feels himself abnormally large or 
 greatly diminished. In degeneration of the posterior columns of the cord, Obersteiner observed that 
 the patient was unable to say whether his right or left side was touched (" Allochiria"). Ferrier 
 observed a case where a stimulus applied to the right side was referred to the left, and vice versa. 
 
 Diminution and paralysis of the tactile sense (Hypopselaphesia and Apselaphesia) 
 occur either in conjunction with simultaneous injury to the sensory nerves, or alone. It is rare to 
 find that one of the qualities of the tactile sense is lost, e . g., either the tactile sense or the sense of 
 temperature — a condition which has been called "partial tactile paralysis" Limbs which are 
 "sleeping" feel heat and not cold (fferzen). 
 
 429. COMMON SENSATION— PAIN.— Definition.— By the term 
 common sensation we understand pleasant or unpleasant sensations in those 
 parts of our bodies which are endowed with sensibility, and which are not refer- 
 able to external objects, and whose characters are difficult to describe, and cannot 
 be compared with other sensations. Each sensation is, as it were, a peculiar one. 
 To this belong pain, hunger, thirst, malaise, fatigue, horror, vertigo, tickling, 
 well-being, illness, the respiratory feeling of free or impeded respiration. 
 
 Pain may occur wherever sensory nerves are distributed, and it is invariably 
 caused by a stronger stimulus than normal being applied to sensory nerves. Every 
 kind of stimulation, mechanical, thermal, chemical, electrical, as well as somatic 
 (inflammation or disturbances of nutrition) may excite pain. The last appear to 
 be especially active, as many tissues become extremely painful during inflamma- 
 tion {e.g., muscles and bones), while they are comparatively insensible to cutting. 
 Pain may be produced by stimulating a sensory nerve in any part of its course, 
 from its centre to the periphery, but the sensation is invariably referred to the 
 peripheral end of the nerve. This is the law of the peripheral reference of 
 sensations. Hence, stimulation of a nerve, as in the scar of an amputated 
 limb, may give rise to a sensation of pain which is referred to the parts already 
 removed. Too violent stimulation of a sensory nerve in its course may render it 
 incapable of conducting impressions, so that peripheral impressions are no longer 
 perceived. If a sufficient stimulus to produce pain be then applied to the cen- 
 tral part of the nerve, such an impression is still leferred to the peripheral end of 
 the nerve. Thus we explain the paradoxical anaesthesia dolorosa. In con- 
 nection with painful impressions, the patient is often unable to localize them ex- 
 actly. This is most easily done when a small injury (prick of a needle) is made on 
 a peripheral part. When, however, the stimulation occurs in the course of the 
 nerve, or in the centre, or in nerves whose peripheral ends are not accessible, as 
 in the intestines, pain (as belly-ache), which cannot easily be localized, is the result. 
 
 Irradiation. — During violent pain there is not unfrequently irradiation of the 
 pain (§ 364, 5), whereby localization is impossible. It is rare for pain to remain 
 continuous and uniform ; more generally there are exacerbations and diminutions 
 of the intensity, and sometimes periodic intensification, as in some neuralgias. 
 
854 METHODS OF TESTING PAIN THE MUSCULAR SENSE. 
 
 The intensity of the pain depends especially upon the excitability of the sen- 
 sory nerves. There are considerable individual variations in this respect, some 
 nerves, e.g., the trigeminus and splanchnic, being very sensitive. The larger the 
 number of fibres affected the more severe the pain. The duration is also of im- 
 portance, in as far as the same stimulation, when long continued, may become 
 unbearable. We speak of piercing, cutting, boring, burning, throbbing, press- 
 ing, gnawing, dull, and other kinds of pain, but we are quite unacquainted with 
 the conditions on which such different sensations depend. Painful impressions are 
 abolished by anaesthetics and narcotics, such as ether, chloroform, morphia, 
 etc. (§364, s). 
 
 Methods of Testing. — To test the cutaneous sensibility, we usually employ the constant or in- 
 duced electrical current. Determine first the minimum sensibility, i.e., the strength of the current 
 which excites the first trace of sensation, and also the minimum of pain, i.e., the feeblest strength of 
 the current which first causes distinct impressions of pain. The electrodes consist of thin metallic 
 needles, and are placed I to 2 cm. apart (Fig. 375). 
 
 Pathological. — When the excitability of the nerves which administer to painful sensations is in- 
 creased, a slight touch of the skin, nay, even a breath of cold air, may excite the most violent pain, 
 constituting cutaneous hyperalgia, especially in inflammatory or exanthematic conditions of the 
 skin. The term cutaneous paralgia is applied to certain anomalous, disagreeable, or painful sen- 
 sations which are frequently referred to the skin — itching, creeping, formication, cold, and burning. 
 In cerebro-spinal meningitis, sometimes a prick in the sole of the foot produces a double sensation of 
 pain and a double reflex contraction. Perhaps this condition may be explained by supposing that 
 in a part of the nerve the condition is delayed (§ 337, 2). In neuralgia there is severe pain, oc- 
 curring in paroxysms, with violent exacerbations and pain shooting into other parts (p. 629). Very 
 frequently excessive pain is produced by pressure on the nerve where it makes its exit from a fora- 
 men or traverses a fascia. 
 
 Valleix's Points Douloureux (1841). — The skin itself to which the sensory nerve runs, espe- 
 cially at first, may be very sensitive; and when the neuralgia is of long duration the sensibility may 
 be diminished even to the condition of analgesia ( Tiirck) ; in the latter case there may be pro- 
 nounced anaesthesia dolorosa (p. 853). 
 
 Diminution or paralysis of the sense of pain (hypalgia and analgia) may be due to affections 
 of the ends of the nerves, or of their course, or central terminations. 
 
 Metalloscopy. — In hysterical patients suffering from hemianesthesia, it is found that the feeling 
 of the paralyzed side is r .'Stored, when small metallic plates or larger, pieces of different metals are 
 applied to the affected parts (Burcq, Charcot). At the same time that the affected part recovers its 
 sensibility the opposite limb or side becomes anaesthetic. This condition has been spoken of as 
 transference of sensibility. The phenomenon is not due to galvanic currents developed by the 
 metals. The phenomenon is, perhaps, explained by the fact that, under physiological conditions, 
 and in a healthy person, every increase of the sensibility on one side of the body, produced by the 
 application of warm metallic plates or bandages, is followed by a diminution of the sensibility of the 
 opposite side. Conversely, it is found that when one side of the body is rendered less sensitive by 
 the application of cold plates, the homologous part of the other side becomes more sensitive {Rumpf 
 and M. Rosenthal). 
 
 430. THE MUSCULAR SENSE.— Muscular Sensibility.— The sen- 
 sory nerves of the muscles (§ 292) always convey to us impressions as to the activ- 
 ity or non-activity of these organs, and in the former case these impressions enable 
 us to judge of the degree of contraction. It also informs us of the amount of the 
 contraction to be employed to overcome resistance. Obviously, the muscular 
 sense must be largely supported and aided by the sense of pressure, and conversely. 
 E. H. Weber showed, however, that the muscle sense is finer than the pressure 
 sense, as by it we can distinguish weights in the ratio of 39 : 40, while the pressure 
 sense only enables us to distinguish those in the ratio of 29 : 30. In some cases 
 there has been observed total cutaneous insensibility, while the muscular sense was 
 retained completely. A frog deprived of its skin can spring without any apparent 
 disturbance. The muscular sense is also greatly aided by the sensibility of the 
 joints, bones and fasciae. Many muscles, e.g., those of respiration, have only 
 slight muscular sensibility, while it seems to be absent normally in the heart and 
 non-striped muscle. 
 
 [The muscular sense stands midway between special and common sensations, 
 and by it we obtain a knowledge of the condition of our muscles, and to what 
 
METHODS OF TESTING THE MUSCULAR SENSE. 855 
 
 extent they are contracted ; also the position of the various parts of our bodies 
 and the resistance offered by external objects. Thus, sensations accompanying 
 muscular movement are twofold — (a) the movements in the unopposed muscles, 
 as the movements of the limbs in space ; and (J>) those of resistance where there 
 is opposition to the movement, as in lifting a weight. In the latter case the sen- 
 sations due to innervation are important, and, of course, in such cases we have 
 also to take into account the sensations obtained from mere pressure upon the 
 skin.. Our sensations derived from muscular movements depend on the direction 
 and duration of the movements. On the sensations thus conveyed to the senso- 
 rium we form judgments as to the direction of a point in space, as well as of the 
 distance between two points in space. This is very marked in the case of the 
 ocular muscles. It is also evident that the muscular sense is ultimately related to, 
 and often combined with, the exercise of the sensations of touch and sight 
 (Sully).] 
 
 Methods of Testing. — Weights are wrapped in a towel and suspended to the part to be tested. 
 The patient estimates the weight by raising and lowering it. The electro-muscular sensibility also 
 may be proved thus : cause the muscles to contract by means of induction shocks, and observe the 
 sensation thereby produced. [Direct the patient to place his feet together while standing, and then 
 close his eyes. A healthy person can stand quite steady, but in one with the muscular sense im- 
 paired, as in locomotor ataxia, the patient may move to and fro, or even fall. Again, a person with 
 his muscular sense impaired may not be able to touch accurately and at once some part of his body 
 when his eyes are closed.] 
 
 Section of a sensory nerve causes disturbance of the fine gradation of movement 
 (p. 646). Meynert supposes that the cerebral centre for muscular sensibility lies 
 in the motor cortical centres, the muscles being connected by motor and sensory 
 paths with the ganglionic cells in these centres. 
 
 Too severe muscular exercise causes the sensation of fatigue, oppression and 
 weight, in the limbs (§ 304). 
 
 Pathological. — Abnormal increase of the muscular sense is rare [muscular hyperlagia and 
 hyperesthesia), as in anxietas tibiarum, a painful condition of unrest which leads to a continual 
 change in the position of the limbs. In cramp there is intense pain, due to stimulation of the 
 sensory nerves of the muscle, and the same is the case in inflammation. Diminution of the mus- 
 cular sensibility occurs in some choreic and ataxic persons (J 364, 5). In locomotor ataxia the 
 muscular sense of the upper extremities may be normal or weakened, while it is usually consider- 
 ably diminished in the legs. [The muscular sense is said to be increased in the hypnotic condition 
 and in somnambulists.] 
 
REPRODUCTION AND DEVELOPMENT. 
 
 Fig. 544. 
 
 431. FORMS OF REPRODUCTION. — I. Abiogenesis (Generatio aequivoca, sive spon- 
 tanea, spontaneous generation). — It was formerly assumed that, under certain circumstances, 
 non-living matter derived from the decomposition of organic materials became changed sponta- 
 neously into living beings. While Aristotle ascribed this mode of origin to insects, the recent 
 observers who advocate this form of generation restrict its action solely to the lowest organism. 
 Experimental evidence is distinctly against spontaneous generation. If organized matter be heated 
 to a very high temperature in sealed tubes, and be thus deprived of all living organisms or their 
 spores, there is no generation of any organism. Hence the dictum " Omne vivum ex ovo " (Harvey, 
 or ex vivo). Some highly-organized invertebrate animals (Gordius, Anguillula, Tardigrada, and 
 Rotatoria) may be dried, and even heated to 140 C, and yet regain their vital activities on being 
 moistened (Anabiosis). 
 
 II. Division or fission occurs in many protozoa (amoeba, infusoria). The organism, just as is 
 the case with cells, divides, the nucleus, when present, taking an active part in the process, so that 
 two nuclei and two masses of protoplasm, forming two organisms, are produced. The Ophidiasters, 
 among the echinoderms, divide spontaneously, and they are said to throw off an arm which may 
 develop into a complete animal. According to Trembley (1744), the hydra may be divided into 
 pieces, and each piece gives rise to a new individual [although under normal circumstances the 
 hydra gives off buds, and is provided with generative organs]. 
 
 [Division of Cells. — Although a cell is defined as a " nucleated mass of living protoplasm," 
 recent researches have shown that, from a histological point of view, a cell is really a very complex 
 
 structure. The apparently homogeneous cell substance 
 is traversed by a fine plexus of fibrils, with a homoge- 
 neous substance in its meshes, while a similar network of 
 fibrils exists within the nucleus itself (Fig. 544). A cell 
 may divide directly, as it were, by simple cleavage, 
 and in the process the nucleus usually divides before the 
 cell protoplasm. The nucleus becomes constricted in 
 the centre, has an hour-glass shape, and soon divides 
 into two. But recent observations, confirmed by a great 
 number of investigators, conclusively prove that the pro- 
 cess of division in cells is a very complicated one, the 
 changes in the nucleus being very remarkable. The term 
 karyokinesis, or indirect division, has been applied 
 to this process. Fig. 544 shows the changes that take place in the nucleus. The intranuclear 
 network (a) passes into a convolution of thinner fibrils, while the nuclear envelope becomes less 
 distinct, the fibrils at the same time becoming thicker and forming loops, which gradually arrange 
 themselves around a centre (c and d) in the form of a wreath or rosette. The fibres curve round 
 both at the periphery and the centre ; but when their peripheral connections are severed or dis- 
 solved, we obtain a star-shaped form, or aster, composed of single loops radiating from the centre 
 (1?). After further subdivision, the whole is composed of fine radiating fibrils (/), which gradually 
 arrange themselves around two poles, or new centres, to form a diaster, or double star (g), the two 
 groups being separated by a substance called the equatorial plate. Each of the groups of fibrils 
 becomes more elongated, and forms a nuclear spindle, which indicates the position of a new 
 nucleus. The separate groups of fibrils again become convoluted; each group gets a nuclear 
 membrane, while the cell protoplasm divides, and two daughter nuclei are obtained from the 
 original cell.] 
 
 III. Budding or gemmation occurs in a well-marked form among the polyps and in some in- 
 fusorians (Vorticella). A bud is given off by the parent, and gradually comes more and more to 
 resemble the latter. The bud either remains permanently attached to the parent, so that a complex 
 organism is produced, in which the digestive organs communicate with each other directly, or in 
 some cases there may be a " colony " with a common nervous system, such as the polyzoa. In 
 some composite animals (siphonophora) the different polyps perform different functions. Some have 
 a digestive, others a motor, and a third a generative function, so that there is a physiological division 
 of labor. Buds which are given off from the parent are formed internally in the rhizopoda. In 
 some animals (polyps, infusoria), which can reproduce themselves by buds or divisions, there is also 
 
 856 
 
 Changes in a cell nucleus during karyokinesis. 
 
TESTIS. 857 
 
 the formation of male and female elements of generation, so that they have a sexual and non-sexual 
 mode of reproduction. 
 
 IV. Conjugation is a form of reproduction which leads up to the sexual form. It occurs in the 
 unicellular Gregarinae. The anterior end of one such organism unites with the posterior end of 
 another ; both become encysted, and form one passive spherical body. The conjoined structures 
 form an amorphous mass, from which numerous globular bodies are formed, and in each of which 
 numerous oblong structures — the pseudo-navicelli — are developed. These bodies become, or give 
 rise to, an amoeboid structure, which forms a nucleus and an envelope, and becomes transformed into 
 a gregarina. 
 
 Sexual reproduction requires the formation of the embryo from the conjunction of the male 
 and female reproductive elements, the sperm cell and the germ cell. These products may be 
 formed either in one individual (hermaphroditism, as in the flat worms and gasteropods), or in two 
 separate organisms (male or female). Sexual reproduction embraces the following varieties: — 
 
 V. Metamorphosis is that form of sexual reproduction in which the embryo from an early 
 period undergoes a series of marked changes of external form, e. g., the chrysalis stage, and the 
 pupa stage, and in none of these stages is reproduction possible. Lastly, the final sexually developed 
 form (the imago stage in butterflies) is produced, which forms the sexual products whose union gives 
 rise to organisms which repeat the same cycle of changes. Metamorphosis occurs extensively 
 among the insects; some of them have several stages (holo-metabolic), and others have few stages 
 (hemi-metabolic). It also occurs in some arthropoda, and worms, e.g., trichina; the sexual form 
 of the animal occurs in the intestine, the numerous larva 1 wander into the muscles, where they 
 become encysted, and form undeveloped sexual organs, constituting the pupa stage of the muscular 
 trichina. When the encysted form is eaten by another animal, the sexual organs come into activity, 
 a new brood is formed, and the cycle is repeated. Metamorphosis also occurs in the frog and in 
 petromyzon. [This is really a condition in which the embryo undergoes marked changes of form 
 before it becomes sexually mature.] 
 
 VI. Alternation of Generations (Steenstrup). — In this variety some of the members of the 
 cycle can produce new beings non-sexually, while in the final stage reproduction is always sexual. 
 From a medical point of view the life-history of the tapeworm or Taenia is most important. The 
 segments of the tapeworm are called proglottides, and each segment is hermaphrodite, with testes, 
 vas deferens, penis, ovary, etc., and numerous ova. The segments are evacuated with the faeces. 
 The eggs are fertilized after they are shed, and from them is developed an elliptical embryo, pro- 
 vided with six hooklets, which is swallowed by another animal, the host. These embryos bore their 
 way into the tissues of the host, where they undergo development, forming the encysted stage 
 (Cysticercus, Coenurus, or Echinococcus). The encysted capsule may contain one (cysticercus) or 
 many (coenurus) sessile heads of the taenia. In order to undergo further development, the cysti- 
 cercus must be eaten alive by another animal, when the head or scolex fixes itself by its hooklets 
 and suckers to the intestine of its new host, where it begins to bud and produce a series of new 
 segments between the head and the last-formed segment, and thus the cycle is repeated. 
 
 The most important flat worms are : Taenia solium, in man ; the Cysticercus cellulosaa in the 
 pig, where it constitutes the measle in pork; Tania mediocanellata, the encysted stage, in the ox; 
 Tcenia coenurus, in the dog's intestine ; the encysted stage, or Coenurus cerebralis, in the brain of 
 the sheep, where it gives rise to the condition of "staggers;" Tania echinococcus, in the dog's 
 intestine ; the embryos or scolices occur in the liver of man as " hydatids." 
 
 The medusae also exhibit alternation of generations, and so do some insects, especially the plant 
 lice or aphides. 
 
 VII. Parthenogenesis {Owen v. Siebold). — In this variety, in addition to sexual reproduction, 
 new individuals may be produced without sexual union. The non-sexually produced brood is always 
 of one sex, as in the bees. A bee-hive contains a queen, the workers, and the drones or males. 
 During the mutual flight the queen is impregnated by the males, and the seminal fluid is stored up 
 in the receptaculum seminis of the queen, and it appears that the queen may voluntarily permit the 
 contact of this fluid with the ova or withhold it. All fertilized eggs give rise to female, and all un- 
 fertilized ones to male bees. 
 
 VIII. Sexual reproduction without any intermediate stages occurs in, besides man, mammals, 
 birds, reptiles, and most fishes. 
 
 432. TESTIS — SEMINAL FLUID. — [Testis. — In the testis or male reproductive organ, 
 the seminal fluid which contains the male element or spermatozoa is formed. The framework of 
 the gland consists of a thick, strong, white fibrous covering, the tunica albuginea, composed 
 chiefly of white interlacing fibrous tissue. Externally this layer is covered by the visceral layer of 
 the serous membrane, or the tunica vaginalis, which invests the testis and epididymis. The tunica 
 albuginea is prolonged for some distance as a vertical septum into the posterior part of the testis, to 
 form the mediastinum testis or corpus Highmori. Septa or trabecular — more or less complete 
 — stretch from the under surface of the T. albuginea toward the mediastinum, so that the organ is 
 subdivided thereby into a number of compartments or lobules, with their bases directed outward 
 and their apices toward the mediastinum. From these, finer sustentacular fibres pass into the com- 
 partments to support the structures lying in these compartments. ] 
 
858 
 
 STRUCTURE OF A SEMINAL TUBULE. 
 
 [Arrangement of Tubules. — Each compartment contains several seminal tubules, long con- 
 voluted tubules ( T Jj in. in diam.) which rarely branch except at their outer end ; they are about 
 two feet in length and exceed 800 in number. These tubules run toward the mediastinum, those in 
 one compartment uniting at an acute angle with each other, to form a smaller number of narrower, 
 straight tubules — tubuli recti (Fig. 546). These straight tubules open into a network of tubules 
 in the mediastinum to form the rete testis, a dense network of tubules of irregular diameter (Fig. 
 546). From this network there proceed 12 to 15 wider ducts — the vasa efferentia — which after 
 emerging from the testis are at first straight, but soon become convoluted — and form a series of 
 conical eminences— the coni vasculosi — which together form the head of the epididymis. These 
 tubes gradually unite with each other and form the body and globus minor of the epididymis, 
 
 Fig. 545. 
 
 T. albuginea. 
 
 Blood vessels. 
 
 Straight tubules 
 
 Rete testis. 
 
 'Seminal tubules cut across. 
 
 Septum. 
 
 Transverse section of the testis (low -power view). 
 
 which, when unraveled, is a tube about 20 feet long terminating in the vas deferens (2 feet long), 
 which is the excretory duct of the testis]. 
 
 [Structure of a Tubule. — The seminal tubules consist of a thick, well-marked basement 
 membrane, composed of flattened, nucleated cells arranged like membranes (Fig. 550, I). These 
 tubes are lined by several layers of more or less cubical cells ; there is an outer row of such cells 
 next the basement membrane, and often showing a dividing large nucleus. Internal to these are 
 several layers of inner large clear cells with nuclei often dividing, so that they form many daughter 
 cells which lie internal to them and next the lumen. From these daughter cells are formed the 
 spermatozoa, and they constitute the spermatoblasts. These several layers of cells leave a 
 
CHEMICAL COMPOSITION OF THE SEMINAL FLUID. 
 
 859 
 
 distinct lumen. The tubuli recti are narrow in diameter, and lined by a single layer of squamous 
 or flattened epithelium (Fig. 546). The rete testis consists merely of channels in the fibrous 
 stroma without a distinct membrana propria, but lined by flattened epithelium. The vasa efferentia 
 and coni vasculosi have circular smooth muscular fibres in their walls, and are lined by a layer 
 of columnar ciliated epithelium with striated protoplasm. At the bases of these cells in some parts 
 is a layer of smaller granular cells. These tubules form the epididymis, whose tubules have the 
 same structure (Fig. 547)- In the sheep pigment cells are often found in the basement mem- 
 brane. The vas deferens is lined by several layers of columnar epithelium resting on a dense 
 layer of fibrous tissue — the mucosa. Outside this is the muscular coat, a thick layer of ton- 
 striped muscle composed of a thick inner circular, and thick outer longitudinal layer, a thin sub- 
 mucous coat connecting the muscular and mucous coats together; outside all is the fibrous 
 adventitia.] 
 
 [The interstitial tissue (Fig. 545), supporting the seminal tubules, is laminated, and covered by 
 endothelial plates, with slits or spaces between the limellse, which form the origin of the lym- 
 phatics. These lymph spaces are easily injected by the puncture method. In fact, if Berlin blue 
 be forced into the testis the lymphatics of the testis and spermatic cord are readily filled with the 
 injection. In some animals (boar), and a less extent in man, dog, there are also fairly large poly- 
 hedral interstitial cells, often with a large nucleus and sometimes pigmented. They represent 
 the residue of the epithelial cells of the Wolffian bodies [Klein), or, according to Waldeyer, they 
 
 Fig. 546. 
 
 End of 
 convo- 
 luted 
 tube. 
 
 Narrow 
 part. 
 
 Fig. 547. 
 
 Rete 
 testis. 
 
 Convoluted seminal tubule opening into a 
 narrow straight tubule. 
 
 Blood vessel. 
 
 Transverse 
 section of a tube 
 of epididymis. 
 
 Ciliated 
 
 cylindrical 
 
 epithelium. 
 
 Blood vessel. 
 
 Interstitial 
 connective 
 tissue. 
 
 Transverse section of the tubules of the 
 epididymis. 
 
 are plasma cells. The blood vessels are numerous, and form a dense plexus outside the base - 
 ment membrane of the seminal tubules.] 
 
 Chemical Composition. — The seminal fluid, as discharged from the 
 urethra, is mixed with the secretion of the glands of the vas deferens, Cowper's 
 glands, and those of the prostate, and with the fluid of the vesiculae seminales. 
 Its reaction is neutral or alkaline, and it contains 82 per cent, of water, serum- 
 albumin, alkali-albuminate, nuclein, lecithin, cholesterin, fats (protamin?), phos- 
 phorized fat, salts (2 per cent.), especially phosphates of the alkalies and earths, 
 together with sulphates, carbonates, and chlorides. The odorous body, whose 
 nature is unknown, was called " spermatin" by Vanquelin. 
 
 Seminal Fluid. — The sticky, whitish-yellow seminal fluid, largely composed of a mixture of 
 the secretions of the above-named glands, when exposed to the air, becomes more fluid, and on 
 adding water it becomes gelatinous, and from it separates whitish, transparent flakes. When long 
 exposed, it forms rhomboidal crystals, which, according to Schreiner, consist of phosphatic salts 
 with an organic base (C 2 H 5 N). These crystals (Fig. 548) are said to be derived from the pros- 
 
860 
 
 DEVELOPMENT OF SPERMATOZOA. 
 
 tatio fluid, and are identical with the so-called Charcot's crystals (Fig. 144, c, and \ 138). The 
 prostatic fluid is thin, milky, amphoteric, or of slightly acid -reaction, and is possessed of the seminal 
 odor. The phosphoric acid necessary for the formation of the crystals is obtained from the seminal 
 fluid. A somewhat similar odor occurs in the albumin of eggs not quite fresh. The secretion of 
 the vesiculae seminales of the guinea pig contains much fibrinogen (Jftensen and Landwehr). 
 
 The spermatozoa are 50 /i long, and consist of a flattened, pear-shaped head 
 (Fig. 549, 1 and 2, k), which is followed by a rod-shaped middle piece, m 
 
 (Schweigger-Seidel), and a long tail-like 
 Fig. 548. prolongation or cilium, f. The whole 
 
 spermatozoon is propelled forward by the 
 to-and-fro movements of the tail at the 
 rate of 0.05 to 0.5 mm. per second; the 
 movement is most rapid immediately 
 after the fluid is shed, but it gradually 
 becomes feebler. 
 
 Finer Structure. — The observations of Jensen 
 have shown that the middle piece and head are 
 still more complex, although this is not the case in 
 human spermatozoa and those of the bull (C Ret- 
 zius). These consist of a flattened, long, narrow, 
 transparent, protoplasmic mass, with a fibre com- 
 posed of many delicate threads in both margins. 
 At the tip of the tail both fibres unite into one. 
 The fibre of the one margin is generally straight; 
 the other is thrown into wave-like folds, or winds 
 in a spiral manner round the other ( W. Krause, 
 Gibbes). G. Retzius describes a special terminal 
 filament (Fig. 549> e). An axial thread, sur- 
 rounded by an envelope of protoplasm, traverses 
 the middle piece and the tail (Eimer, v. Braun). 
 [Leydig showed that in the salamander there is a delicate membrane attached to the tail, and Gibbes 
 has described a spiral thread attached to the head (newt) and connected with the middle piece by a 
 hyaline membrane.] 
 
 Motion of the Spermatozoa. — -[After the discharge of the seminal fluid, the spermatozoa ex- 
 hibit spontaneous movements for many hours or days.] The movements are due to the lashing 
 movements of the tail, which moves in a circle or rotates on its long axis, the impulse to movement 
 proceeding from the protoplasm of the middle piece and the tail, which seem to be capable of mov- 
 ing when they are detached {Eimer). These movements are comparable to those that occur in 
 cilia ({} 292), and there are transition forms between ciliary and amoeboid movements, as in the 
 Monera. Reagents. — Within the testis they do not exhibit movement, as the fluid is not sufficiently 
 dilute to permit them to move. Their movements are specially lively in the normal secretion of 
 the female sexual organs (Bischoff), and they move pretty freely, and for a long time, in all normal 
 animal secretions except saliva. Their movements are paralyzed by water, alcohol, ether, chloro- 
 form, creosote, gum, dextrin, vegetable mucin, syrup of grape sugar, or very alkaline or acid uterine 
 orvaginal mucus (Donne), acids and metallic salts, and a too high or too low temperature. The 
 narcotics, as long as they are chemically indifferent, behave as indifferent fluids, and so do medium 
 solutions of urea, sugar, albumin, common salt, glycerin, amygdalin, etc. ; but if these be too dilute 
 or too concentrated, they alter the amount of water in the spermatozoa and paralyze them. The 
 quiescence produced by water may be set aside by dilute alkalies ( Virchow), as with cilia (p. 491). 
 Engelmann finds that minute traces of acids, alcohol, and ether excite movements. The sperma- 
 tozoa of the frog may be frozen four times in succession without killing them. They bear a heat of 
 43-75° C., and they will live for 70 days when placed in the abdominal cavity of another frog 
 
 Crystals from spermatic fluid. 
 
 Resistance. — Owing to the large amount of earthy salts which they contain, when dried upon 
 a microscopical slide they still retain their form ( Valentin). Their form is not destroyed by nitric, 
 sulphuric, hydrochloric, or boiling acetic acid, or by caustic alkalies ; solutions of NaCl and salt- 
 petre (10 to 15 per cent.) change them into amorphous masses. Their organic basis resembles the 
 semi-solid albumin of epithelium. 
 
 Seminal fluid, besides spermatozoa, also contains seminal cells, a few epithelial cells from the 
 seminal passages, numerous lecithin granules, stratified amyloid bodies (inconstant), granular yellow 
 pigment, especially in old age, leucocytes, and sperma crystals (Fiirbinger). 
 
 Development of Spermatozoa. — The walls of the seminal tubules, n, which 
 are made up of spindle-shaped cells, are lined by a nucleated, protoplasmic layer 
 
DEVELOPMENT OF SPERMATOZA. 
 
 861 
 
 (Fig. 550, I, b, and IV, h), from which there project into the lumen of the tube, 
 long (0.053 nun.) column-like prolongations, (I, c, and II, III, IV), which break 
 
 Fig. 549. 
 
 Spermatozoa 1, human (X €00)1 the head seen from the side ; 2, on edge ; k, head ; ?«, middle piece ; /, tail ; e t ter- 
 minal filament ; 3, from the mouse ; 4, bothriocephalus latus ; 5 , deer ; 6, mole ; 7, green woodpecker ; 8, black 
 swan ; 9, from a cross between a goldfinch (M) and a canary (F) ; io, from cobitis. 
 
 up at their free end into several round or oval lobules (II) — the spermatoblasts 
 {v. Ebner) ; these consist of soft, finely granular. protoplasm, and usually have an 
 oval nucleus in their lower part. During development, each lobule of the sper- 
 
 Fig. 550. 
 
 Semi-diagrammatic spermatogenesis ; I, transverse section of a seminal tubule — a, membrane ; b, protoplasmic inner 
 lining ; c, spermatoblast ; s, seminal cells. II, Unripe spermatoblast—^ rounded cleavate lobules ; fi, seminal 
 cells. I V , spermatoblast, with ripe spermatozoa (£) not yet detached ; tail, r ; n, wall of the seminal tubule ; 
 A, its protoplasmic layer. Ill, spermatoblast with a spermatozoon free, t. 
 
 matoblast elongates into a tail (IV, r), while the deeper part forms the head and 
 middle piece of the future spermatozoon (IV, k). At this stage the spermatoblast 
 
862 STRUCTURE OF THE OVARY. 
 
 is like a greatly enlarged, irregular, cylindrical, epithelial cell. When develop- 
 ment is complete, the head and middle piece are detached (III, t), and ultimately 
 the remaining part of the spermatoblast undergoes fatty degeneration. Not un- 
 frequently in spermatozoa we may observe a small mass of protoplasm adhering to 
 the tail and the middle piece (III, /). Between the spermatoblasts are numerous 
 round amoeboid cells devoid of an envelope, and connected to each other by pro- 
 cesses. They seem to secrete the fluid part of the semen, and they may, therefore, 
 be called seminal cells (I, s, II, III, IV, /). A spermatozoon, therefore, 
 is a detached, independently mobile cilium of an enlarged epithelial cell. Some 
 observers adhere to the view that the spermatozoa are, in part, at least, formed 
 within round cells, by a process of endogenous development. 
 
 Shape. — The spermatozoa of most animals are like cilia with larger or smaller heads.- The head 
 is elliptical (mammals), or pear-shaped (mammals), or cylindrical (birds, amphibians, fish), or cork- 
 screw (singing birds, paludina), or merely like hairs (insects — Fig. 549). Immobile seminal cells, 
 quite different from the ordinary forms, occur in myriapoda and the oyster. 
 
 433. THE OVARY— OVUM— UTERUS.— [Structure of the Ovary (Fig. 551).— The 
 ovary consists of a connective-tissue framework, with blood vessels, nerves, lymphatics, and numer- 
 ous non-striped muscular fibres. The ova are embedded in this matrix. The surface of the ovary 
 is covered with a layer of columnar epithelium (Fig. 552, e), the remains of the germ epithelium. 
 
 Fig. 551. 
 
 Section of a cat's ovary. The place ot attachment or hilum is below. On the left is a corpus luteum. 
 
 The most superficial layer is called the albuginea ; it does not contain any ova. Below it is the 
 cortical layer of Schron, which contains the smallest Graafian follicles (j-J 5 inch — Fig. 551), while 
 deeper down are the larger follicles (3^ to T J^ inch). There are 40,000 to 70,000 follicles in the 
 ovary of a female infant. Each ovum lies within its follicle or Graafian vesicle.] 
 
 Structure of an Ovum. — The human ovum (C. E. v. Baer, 1827) is 0.18 to 0.2 mm. [-rijin.] 
 in diameter, and is a spherical, cellular body with a thick, solid, elastic envelope, the zona pellu- 
 cida, with radiating striae. The zona pellucida encloses the cell contents, represented by the pro- 
 toplasmic, granular, contractile vitellus or yelk, which in turn contains the eccentrically-placed 
 spherical nucleus or germinal vesicle (40-50/4 — Purkinjc, 182s; Cosle, 1834). The germinal 
 vesicle contains the nucleolus or germinal spot (5-7 /i — R. Wagner, /8jJ). The chemical com- 
 position is given in \ 232. 
 
 [Ovum. Cell. 
 
 Zona pellucida corresponds to the Cell wall. 
 
 Vitellus " " Cell contents. 
 
 Germinal vesicle " " Nucleus. 
 
 Germinal spot " " Nucleolus.] 
 
 [This arrangement shows the corresponding parts in a cell and the ovum, and in fact the ovum 
 represents a typical cell.] 
 
 The zona pellucida (Fig. 553, V, Z), to which cells of the Graafian follicle are often adherent, 
 is a cuticular membrane formed secondarily by the follicle (Pfiuger). According to van Beneden, 
 it is lined by a thin membrane next the vitellus, and he regards the thin membrane as the original 
 cell membrane of the ovum. The fine radiating striae in the zona are said to be due to the exist- 
 
DEVELOPMENT OF THE OVA. 
 
 863 
 
 ence of numerous canals (Kolliker, v. Seklen). It is still undecided whether there is a special 
 micropyle or hole for the entrance of the spermatozoa. 
 
 A micropyle has been observed in some ova (holothurians, many fishes, mussels). The ova of 
 some animals (many insects, e.g., the flea) have porous canals in some part of their zona, and these 
 serve both for the entrance of the spermatozoa and for the respiratory exchanges in the ovum. 
 
 The development of the ova takes place in the following manner : The 
 surface of the ovary is covered with a layer of cylindrical epithelium — the so- 
 called " germ epithelium " — and between these cells lie, somewhat spherical, 
 "primordial ova" (Fig. 553, I, a, a). The epithelium covering the surface 
 dips into the ovary at various places to form "ovarian tubes" (Waldeyer). 
 These tubes, from and in which the ova are developed ( Waldeyer), become deeper 
 and deeper, and they contain, in their interior, large, single spherical cells with 
 a nucleus and a nucleolus, and other smaller and more numerous cells lining the 
 tube. The large cells are the cells (primordial ova) that are to develop into 
 ova, while the smaller cells are the epithelium of the tube, and are direct con- 
 tinuations of the cylindrical epithelium on the surface of the ovary. The upper 
 extremities of the tubes become closed, while the tube itself is divided into a 
 
 Fig. 552. 
 
 Section of an ovary, e, germ epithelium ; i, large-sized follicles ; 2, 2, middle-sized, and 3, 3, smaller-sized follicles ; 
 o, ovum within a Graafian follicle ; v, v, blood vessels of the stroma ; g, cells of the membrana granulosa. 
 
 number of rounded compartments — snared off, as it were, by the ingrowth of the 
 ovarian stroma (I, c). Each compartment so snared off usually contains one, or, 
 at most, two, ova (IV, o, o), and becomes developed into a Graafian follicle. 
 The embryonic follicle enlarges, and fluid appears within it ; while its lateral 
 small cells become changed into the epithelium lining the Graafian follicle itself, 
 or those of the membrana granulosa. The cells of the membrana granulosa form 
 an elevation at one part — the discus proligerus — by which the ovum is attached 
 to the membrana granulosa. The follicles are at first only 0.03 mm. in diameter, 
 but they become larger, especially at puberty. [The smaller ova are near the 
 surface of the ovary, the larger ones deeper in its substance (Fig. 551). When a 
 Graafian follicle with its ovum is about to ripen (IV), it sinks or passes down- 
 ward into the substance of the ovary, and enlarges at the same time by the accu- 
 mulation of fluid — the liquor folliculi — between the tunica and membrana 
 granulosa. It is covered by a vascular outer membrane — the theca folliculi — 
 which is lined by the epithelium constituting the membrana granulosa (IV, 
 g). When a Graafian follicle is about to burst, it again rises to the surface of 
 
864 
 
 DEVELOPMENT OF THE OVA. 
 
 the ovary, and attains a diameter of i.o to 1.5 mm.,- and is now ready to burst 
 and discharge its ovum. [The tissue between the enlarged Graafian follicle and 
 the surface of the ovary gradually becomes thinner and thinner and less vascular, 
 and at last gives way, when the ovum is discharged and caught by the fimbriated 
 extremity of the Fallopian tube embracing the ovary, so that the ovum is shed 
 into the Fallopian tube itself.] Only a small number of the Graafian follicles 
 undergo development normally, by far the greatest number atrophy and never 
 ripen. (The study of the development of the ova and ovary was advanced par- 
 ticularly by Martin Barry, Pfluger, Billroth, Schron, His, Waldeyer, Kolliker, 
 Koster, Lindgren, Schulin, Foulis, Balfour and others.) 
 
 According to Waldeyer, the mammalian ovum is not a simple cell, but a compound structure. 
 The original primitive ovum is, according to him, formed only of the germinal vesicle and ger- 
 
 Fig- 553- 
 
 I, an ovarian tube in process of development (new-born girl), a, a, young ova between the epithelial cells on the 
 surface of the ovary ; b, the ovarian tube with ova and epithelial cells ; c, a small follicle cut off and enclosing 
 an ovum. II, Open ovarian tube from a bitch. Ill, Isolated primordial ovum (human). IV, Older follicle with 
 two ova (a, o) and the tunica granulosa (*-j of a bitch. V, Part of the surface oi a ripe ovum of a rabbit — z, 
 zona pellucida ; d, vitellus , e, adherent cells of the membrana granulosa. VI, First polar globule formed. VII, 
 Formation of the second polar globule (Fol). 
 
 minal spot, with the surrounding membranous clear part of the vitellus (Fig. 553, III). The 
 remainder of the vitellus is developed by the transformation Of granulosa cells, which also form the 
 zona pellucida. 
 
 Holoblastic and Meroblastic Ova. — The ova of frogs and cyclostomata are built on the same 
 type as mammalian ova ; they are called holoblastic ova, because all their contents go to form 
 cells which take part in the formation of the embryo. In contrast with these, the birds, the mono- 
 tremes alone among the mammals (Caldwell),.\.\ie reptiles, and the other fishes have meroblastic 
 ova {Reichert). The latter, in addition to the white or formative yelk, which corresponds to the 
 yelk of the holoblastic eggs, and gives rise to the embryonic cells, contains the food yelk (yellow in 
 birds), and which during development is a reserve store of food for the developing embryo. 
 
 Hen's Egg. — The small, white, round, finely granular speck, the cicatricula, blastoderm, or 
 tread, which is 2.5-3.5 mm> broad and 0.28-0.37 thick, lying upon the surface of the yellow yelk, 
 corresponds to the contents of the mammalian ovum, and is, therefore, the formative yelk. [The 
 
STRUCTURE OF A HEN S EGG. 
 
 865 
 
 cicatricula in an unincubated egg is always uppermost whatever the position of the egg, provided 
 the contents can rotate freely, and this is due to the lighter specific gravity of that part of the yelk 
 in connection with the cicatricula. In a fecundated egg the cicatricula has a white margin (the 
 area opaca), surrounding a clear, transparent area, the beginning of the area pellucida, containing 
 an opaque spot in its centre. If an egg be boiled very hard and a section made of the yelk, it will 
 be found to consist of alternating layers of white and yellow yelk. The outermost layer is a thin 
 layer of white yelk, which is slightly thicker at the margin of the cicatricula. Within the centre of 
 the yelk is a flask-shaped mass of white yelk, the neck of the flask being connected with the white 
 yelk outside. This flask-shaped mass does not become so hard on being boiled, and its upper, 
 expanded end is known as the "nucleus of Pander." The great mass of the yelk is made up, 
 however, of yellow yelk.] Microscopically, the yellow yelk consists of soft, yellow spheres, of 
 from 23-100 /i in diameter, and they are often polyhedral from mutual pressure. [They are very 
 delicate and non-nucleated, but filled with fine granules, which are, perhaps, proteid in their nature, 
 as they are insoluble in ether or alcohol. They are developed by the proliferation of the granulosa 
 cells of the Graafian follicle, which also seem ultimately to form the granulo-fibrous double envelope 
 or the vitelline membrane {Eimer). The whole yelk of the hen's egg is regarded by some ob- 
 
 Fig. 554. 
 
 Vertical section of the mucous membrane of the human uterus, e , columnar epithelium, the cilia absent ; g g, utric- 
 ular glands; c t t intra-glandular connective tissue ; v, v, blood vessels ; m m t muscularis mucosa;. 
 
 servers as equivalent to the mammalian ovum plus the corpus luteum. Microscopically, the white 
 yelk consists of small •vesicles (5-75 fi) containing a refractive substance, and larger spheres con- 
 taining several smaller spherules. The whole yelk is enveloped by the vitelline membrane, which 
 is transparent, but possesses a fine fibrous structure, and it seems to be allied to elastic tissue.] 
 When the yelk is fully developed within the Graafian follicle of the hen's ovarium, the follicle bursts 
 and discharges the yelk, which passes into the oviduct, where in its passage it rotates, owing to the 
 direction of the folds of the mucous membrane of the oviduct. The numerous glands of the oviduct 
 secrete the albumin, or white of the egg, which is deposited in layers around the yelk in its passage 
 along the duct, and forms at the anterior and posterior poles the chalazae. [The chalazae are 
 two twisted cords composed of twisted layers of the outer, denser part of the albumin. They extend 
 from the poles of the yelk not quite to the outer part of the albumin.] [The albumin is invested 
 by the membrana testacea, or shell membrane, which is composed of two layers — an outer 
 thicker and an inner thinner one. Over the greater part of the albumin these two layers are united, 
 but at the broad end of the hen's egg they tend to separate, and air passing through the porous shell 
 separates them more and more as the fluid of the egg evaporates. This air space is not found in 
 fresh-laid eggs.] The layers consist of spontaneously coagulated keratin-like fibres arranged in a 
 
 55 
 
866 
 
 PUBERTY. 
 
 spiral manner around the albumin (Lindvall and Hamarsten). [External to this is the test, or 
 shell, which consists of an organic matrix impregnated with lime salts.] The shell consists of 
 albumin impregnated with lime salts, which form a very porous mortar. [The shell is porous, and 
 its inner layer is perforated by vertical canals, through which the respiratory exchange of the gases 
 can take place.] In the eggs of some birds there is an outer structureless, porous, slimy, or fatty 
 cuticula. The shell is secreted in the lower part of the oviduct. The shell is partly used up for 
 the development of the bones of the chick (Prout, Gruwe, although this is denied by Polt and 
 Preyer). The pigment which often occurs in many layers on the surface of the eggs of some birds 
 appears to be a derivative of haemoglobin and biliverdin. 
 
 Chemical Composition. — The yellow yelk is alkaline and colored yellow, owing to the 
 presence of lutein, which contains iron. It contains several proteids [including a globulin body 
 called vitellin (p. 409)], a body resembling nuclein, lecithin, vitellin, glycerin-phosphoric acid, 
 cholesterin, olein, palmitin, dextrose, potassic chloride, iron, earthy phosphates, fluoric and silicic 
 acids. The presence of cerebrin, glycogen, and starch is uncertain. [Dareste states that starch is 
 present.] 
 
 [The albumin of egg contains— water, 86 per cent.; proteids, 12; fat and extractives, 1.5; 
 saline matter, including sodic and potassic chlorides, phosphates, and sulphates, .5 per cent.] 
 
 [The uterus, a thick, hollow, muscular organ, is covered externally by a serous coat, and lined 
 internally by a mucous membrane, while between the two is the thick muscular coat composed 
 of smooth muscular fibres arranged in a great number of layers and in different directions. The 
 
 Fig. 555. 
 
 Left broad ligament, Fallopian tube, ovary and parovarium, a, uterus ; b, isthmus of Fallopian tube; c, ampulla; 
 g, fimbriated end of the tube, with the parovarium to its right ; e, ovary ; /, ovarian ligament. 
 
 mucous membrane of the body of the uterus in the unimpregnated condition has no folds, while the 
 muscularis mucosae is very well developed and forms a great part of uterine muscular wall. 1 he 
 mucous membrane is lined by a single layer of columnar ciliated epithelium. A vertical section 
 shows the mucous membrane to contain numerous tubular glands (Fig. 554) — the uterine glands 
 — which branch toward their lower ends. They have a membrana propria, and are lined by a single 
 layer of ciliated epithelium, a small lumen being left in the centre. The utricular glands are not 
 formed during intrauterine life (Turner), nor are there any glands in the human uterus at birth 
 (G. J. Engelmann). There are numerous slit-like lymphatic spaces in the mucous membrane 
 (Leopold), which communicate with well-marked lymphatic vessels existing in this and the other 
 layers of the organ. In the cervix the mucous membrane is folded, presenting in the virgin the 
 appearance known as the arbor vitae. The external surface of the vaginal part of the neck is covered 
 by stratified squamous epithelium, like the vagina.] 
 
 [The Fallopian tubes are really the ducts of the ovaries (Fig. 555). They consist of a serous, 
 muscular (an external, longitudinal and an internal circular layer of non-striped muscle), and a 
 mucous layer thrown into many folds and lined by a single layer of ciliated columnar epithelium, 
 but no glands (Fig. 556).] 
 
 434. PUBERTY. — The term puberty is applied to the period at which a 
 human being becomes capable of procreating, which occurs from the 13th to 15th 
 
SIGNS OF MENSTRUATION. 
 
 867 
 
 years in the female and the 14th to 16th in the male. In warm climates, puberty 
 may occur in girls even at 8 years of age. Toward the 40th to 50th year the 
 procreative faculty ceases in the female with the cessation of the menses ; this 
 constitutes the menopause or grand climacteric, while in man procreation 
 has been observed up to any age. From the age of puberty onward, the sexual 
 appetite occurs, and the ripe ova are discharged from the ovary. [It seems, how- 
 ever, that ova are discharged even before puberty or menstruation has occurred.] 
 At puberty the internal and external generative organs and their annexes become 
 more vascular and undergo development ; the pelvis of the female assumes the 
 characteristic female shape. For the v changes in the mammae, see § 230. At the 
 same time hair is developed on the pubes and axilla, and in the male on the face, 
 while the sebaceous glands become larger and more active. 
 
 Other changes occur, especially in the larynx. In the boy the larynx elongates in its antero- 
 posterior diameter, the thyroid, or Adam's apple, becomes more prominent, while the vocal cords 
 lengthen, so that the voice is hoarse, or husky, or " breaks," the voice being lowered at least an 
 octave. In the female the larynx becomes longer, while the compass of the voice is increased. 
 The vital capacity (\ 108), corresponding to the increase in the size of the chest, undergoes a con- 
 
 Fig. 556. 
 
 m 
 
 £-?- 
 
 
 Connective tissue. 
 Ciliated epithelium, 
 Circular muscular fibres. 
 
 Muscular fibres cut 
 across. 
 
 Transverse section of the Fallopian tube. 
 
 siderable increase ; the whole form and expression assume the characteristic sexual appearance, 
 while the psychical energies also receive an impulse. ( 
 
 435. MENSTRUATION.— External Signs.— At regular intervals of 
 time, of 27^-28 days, in a mature female, there is a rupture of one or more ripe 
 Graafian follicles, while at the same time there is a discharge of blood from the 
 external genitals. This is known as the process of menstruation (or menses, cata- 
 menia or periods). Most women menstruate during the first quarter of the moon, 
 and only a few at new and full moon (StrohD. In mammals, the analogous con- 
 dition is spoken of as the period of heat [or the " rut " in deer]. There is a 
 slightly bloody discharge from the external genitals in parnivora, the mare and 
 cow (Aristotle), while apes in their wild condition have a well-marked menstrual 
 discharge (Neubert). [Observations on cases where abdominal section has been 
 performed have shown that the Graafian follicles mature" and burst at any time 
 (Lawson Tait, Leopold).] 
 
 The onset of menstruation is usually heralded by constitutional and local phenomena — there is 
 an increased feeling of congestion in the internal generative organs, pain in the back and loins, ten- 
 sion in the region of the uterus and ovaries, which are sensitive to pressure, fatigue in the limbs, 
 
8G8 
 
 OVULATION. 
 
 alternate feeling of heat and cold, and even a slight increase of the temperature of the skin 
 (Kersch). There may be retardation of the process of digestion and variations in the evacuation 
 of the faeces and urine, and in the secretion of sweat. The discharge is slimy at first, and then 
 becomes bloody, lasting three to four days ; the blood is venous, and shows little tendency to coagu- 
 late, provided it is mixed with much alkaline mucus from the genital passages; but if the hemor- 
 rhage be free, the blood may be clotted. The quantity of blood is ioo to 200 grms. [The blood 
 contains many white blood corpuscles and epithelial cells.] After cessation of the discharge of 
 blood there is a moderate amount of mucus given off. 
 
 The characteristic internal phenomena which accompany menstruation are : 
 (1) The changes in the uterine mucous membrane ; and (2) the rupture of the 
 Graafian follicle. 
 
 1. Changes in the Uterine Mucous Membrane. — The uterine mucous 
 membrane is the chief source of the blood. The ciliated epithelium of the con- 
 gested, swollen, and folded, soft, thick (3 
 to 6 mm.) mucous membrane is shed. The 
 orifices of the numerous mucous glands of 
 the mucous membrane are distinct, the 
 glands enlarge, and the cells undergo fatty 
 degeneration, and so do the tissue and the 
 blood vessels lying between the glands. The 
 tissue contains more leucocytes than normal. 
 This fatty degeneration and the excretion of 
 the degenerated tissue occur, however, only 
 in the superficial layers of the mucosa, 
 whose blood yessels, when torn across, yield 
 the blood. The deeper layers remain in- 
 tact, and from them, after menstruation is 
 over, the new mucous membrane is devel- 
 oped (Kundrat and G. J. Engelmanri). 
 [Leopold denies the existence of this fatty 
 degeneration. According to Williams, the 
 entire mucous membrane is removed at each 
 menstrual period, and it is regenerated from 
 the muscular coat (Fig. 558). The mucous 
 membrane of the cervix remains free from 
 these changes.] 
 
 Fig. 557.— Diagram of the uterus just before men- 2. Ovulation. The Second important 
 
 rc™rmemo r al ad 1 IG P °"5™-Terurwht einternal P^nomenon is ovulation, in which 
 
 menstruation has just ceased, showing the cavity process the ovary becomes more vascular — 
 
 . &&) ydeprived ° f mucous membrane U - the ripe follicle is turgid with fluid, and in 
 
 part projects above the surface of the ovary. 
 The follicle ultimately bursts, its membranes and the epithelium covering of the 
 ovary being torn or give way under the pressure, the bursting being accompanied 
 by the discharge of a small amount of blood. At the same time, the congested, 
 turgid, and erected fimbriated extremity of the Fallopian tube (Fig. 555) is applied 
 to the ovary, so that the discharged ovum, with its adherent granulosa cells, and the 
 liquor folliculi, are caught by the funnel-shaped extremity of the tube. The ovum, 
 when discharged, is carried toward the uterus by the ciliated epithelium (§ 433) 
 of the tube, and perhaps, also, partly by the contraction of its muscular coat. 
 Ducalliez and Kiiss found that, by fully injecting the blood vessels, they could 
 imitate the erection of the Fallopian tube. Rouget points out that the non-striped 
 muscle of the broad ligaments may cause constriction of the vessels, and thus 
 secure the necessary injection of the blood vessels of the Fallopian tube. 
 
 Pfliiger's Theory. — There are two theories as to the connection between ovulation or the dis- 
 charge of an ovum and the escape of blood from the uterine mucous membrane. Pfliiger regards 
 the bloody discharge from the superficial layers of the uterine mucous membrane as a physiological 
 preparation or "freshening" of the tissue (in the surgical sense;, by which it will be prepared to 
 
ERECTION OF THE PENIS. 
 
 869 
 
 receive the ovum when the latter reaches the uterus, so that union can take place between the ovum 
 and the freshly- ex posed surface of the mucous membrane, and thus the ovum will receive nourish- 
 ment from a new surface. 
 
 Reichert's Theory. — This view is opposed to that of Reichert, Engelmann, Williams, and 
 others. According to Reichert's theory, before an ovum is discharged at all there is a sympathetic 
 change in the uterine mucous membrane, whereby it becomes more vascular, more spongy, and 
 swollen up. The mucous membrane so altered is spoken of as the membrana decidua menstrualis, 
 and from its nature it is in a proper condition to receive, retain, and nourish a fertilized ovum which 
 may come into contact with it. If the ovum, however, be not fertilized, and escapes from the gen- 
 ital passages, then the uterine mucous membrane degenerates and blood is shed as above described. 
 According to this view, the hemorrhage from the uterine mucous membrane is a sign of the non- 
 occurrence of pregnancy; the mucous membrane degenerates because it is not required for this 
 occasion ; the menstrual blood is an external sign that the ovum has not been impregnated. So that 
 pregnancy, i. e., the development of the embryo in utero, is to be calculated, not from the last men- 
 struation, but from some time between the last menstruation and the period which does not occur. 
 
 In some cases the ovulation and the formation of the decidua menstrualis occur separately, so 
 that there may be menstruation without ovulation, and ovulation without menstruation. 
 
 Corpus Luteum. — When a Graafian follicle bursts, it discharges its contents and collapses ; in 
 the interior are the remains of the membrana granulosa and a small effusion of blood, which soon 
 coagulates. The small rupture soon heals, after the serum is absorbed. The vascular wall of the 
 
 Fig. 559. 
 
 Erectile tissue, a, trabeculae of connective tissue with elastic fibres and smooth muscles (C) ; b, venous spaces. 
 
 follicle swells up. Villous prolongations or granulations of young connective tissue, rich in capil- 
 laries and cells, grow into the interior of the follicle. Colorless blood corpuscles also wander into 
 the interior. At the same time the cells of the granulosa proliferate, and form several layers of 
 cells, which ultimately, after the disappearance of a number of blood vessels, undergo fatty degen- 
 eration, lutein mi fatty matter being formed, and it is this mass which gives the corpus luteum its 
 yellow color. The capsule becomes more and more fused with the ovarian stroma. If pregnancy 
 does not take place after the menstruation, then the fatty matter is rapidly absorbed, and the effused 
 blood is changed into hsematoidin ($ 20) and other derivatives of haemoglobin, while there is a 
 gradual shrivelling of the whole mass, which is complete in about four weeks, only a very small 
 remainder being left. Such a corpus luteum, i. e., one not accompanied by pregnancy, is called a 
 false corpus luteum. If, however, pregnancy occurs, then the corpus luteum, instead of shrivel- 
 ling, grows and becomes a large body, especially at the third and fourth month, the walls are thicker, 
 the color deeper, so that the corpus luteum at the period of delivery may be 6 to 10 mm. in diam- 
 eter, and its remains may be found in the ovary for a very long time thereafter (Fig. 551). This 
 form is sometimes spoken of as a true corpus luteum (Bischoff). [We cannot draw too sharp a 
 distinction between these two forms.] Only a very small number of the ova in the ovary undergo 
 development and are discharged; by far the greater number degenerates [Slavjansky). 
 
 436. PENIS ERECTION. — Penis. — [The penis i« composed of two long cylindrical corpora 
 cavernosa, the corpus spongiosum, which lies between and below them, and surrounds the 
 
870 MECHANISM OF ERECTION. 
 
 urethra; these are held together by fibrous and muscular sheaths, and are composed of erectile 
 tissue.] Our knowledge of the distribution of the blood within the penis is chiefly due to C. 
 Langer's researches. The albuginea of the corpus spongiosum consists of tendinous connective 
 tissue, containing thickly-woven elastic tissue and smooth muscular fibres, which together form a 
 solid fibrous envelope, from which numerous interlacing trabecular pass into the interior, so that the 
 corpus spongiosum comes to resemble a sponge. The anastomosing spaces bounded by these tra- 
 becule form a series of inter-communicating venous spaces, or sinuses, filled with blood and lined 
 by a layer of endothelium constituting erectile tissue (Fig. 559). The largest sinuses lie in the 
 lowerand external part of the corpus cavernosum, while they are less numerous and smaller in the 
 upper part. The small arteries arise from the A. profunda penis, which runs along the septum, 
 and pass to the trabecular after following a very sinuous course. At the outer part of the corpus 
 spongiosum some of the small arteries become directly continuous with the larger venous sinus.es ; 
 some of them, however, terminate in capillaries both in the outer part and within the corpus spongi- 
 osum, the capillaries ultimately terminating in the venous sinuses. The helicine arteries of the 
 penis described by Joh. Milller are merely much twisted arteries. The deep veins of the penis arise 
 by fine veinlets within the body of the organ, while the veins proceeding from the cavernous spaces 
 pass to the dorsum of the penis to form the vena dorsalis penis. As these vessels have to traverse 
 the meshes of the vascular network in the cortex of the corpora cavernosa penis, it is evident that, 
 when the network is congested by being filled with blood, it must compress the outgoing venous 
 trunks. The corpus cavernosum urethrae consists, for the most part, of an external layer of closely- 
 packed anastomosing veins, which surround the longitudinally-directed blood vessels of the urethra. 
 In the dog all the arteries of the penis run at first toward the surface, where they divide into 
 penicilli. The veins arise from the capillary loops in the papillae, and they empty their blood into 
 the cavernous spaces. Only a small part of the blood passes to the cavernous spaces through the 
 internal capillaries and veins, but arterial blood never flows directly into these spaces (M. v. Frey). 
 
 Mechanism of Erection. — Erection is due to the overfilling of the blood 
 vessels of the penis with blood, whereby the volume of the organ is increased four 
 or five times, while at the same time there are also a higher temperature, increased 
 blood pressure (to \ of that in the carotid — Eckhard), with at first a pulsatile 
 movement, increased consistence, and erection of the organ. 
 
 Regner de Graaf obtained complete erection of the penis by forcibly injecting its blood vessels 
 (1668). 
 
 The preliminary phenomena consist in a considerable increase of the arte- 
 rial blood supply, the arteries being dilated and pulsating strongly. The arteries 
 are controlled by the nervi erigentes. The nervi erigentes [called by Gaskell 
 the pelvic splanchnics (p. 649)] arise chiefly from the second (more rarely the 
 third) sacral nerves (dog), and have ganglionic cells in their course (Loven, 
 Nikolsky). These nerves contain vaso-dilator fibres, which can be excited in 
 part reflexly from the sensory nerves of the penis, the transference centre being 
 in the centre for erection in the spinal cord (§ 362, 4). Sensory impressions pro- 
 duced by voluntary movements of the genital apparatus (by the ischio- and bulbo- 
 cavernosi and cremaster muscles) can also discharge this reflex ; while the thought 
 of sexual impulses, referable to the penis, tends to induce erection. The nervi 
 erigentes also supply the longitudinal fibres of the rectum (Eellner). 
 
 The centre for erection in the spinal cord (§ 362, 2) is, however, controlled 
 by the dominating vaso-dilator centre in the medulla oblongata (§372), and the 
 two centres are connected by fibres within the cord; hence stimulation of the 
 upper part of the cord, as by asphyxiated blood (§ 362, 5) or muscarin, may also 
 be followed by erection (Nikolsky). [The seminal fluid is frequently found dis- 
 charged in persons who have been hanged.] 
 
 The psychical activity of the cerebrum has a decided influence on the genital 
 vaso-dilator nerves. Just as the psychical disturbance which accompanies anger 
 or shame is followed by dilatation of the blood vessels of the head, owing to 
 stimulation of the vaso-dilator fibres ; so when the attention is directed to the 
 sexual centres, there is an action upon the nervi erigentes. This action of the 
 brain is more comprehensible, since we know that the diameter of the blood 
 vessels is affected by the cortex cerebri (§ 377). The fibres probably pass from 
 the cerebrum through the peduncles of the cerebrum and the pons ; as a matter 
 of fact, if these parts be stimulated, erection may take place (§ 362, 4) (Eckhard). 
 
MECHANISM OF ERECTION. 
 
 871 
 
 When the impulse to erection is obtained by the increased supply of arterial 
 blood,, the full completion of the act is brought about by the activity of the follow- 
 ing transversely striped muscles : (i) The ischio-cavernosus (Fig. 164) arises 
 from the coccyx, and by its tendinous union surrounds the root of the penis. 
 When it contracts it compresses the root of the penis from above and laterally, so 
 that the outflow of blood from the penis is hindered. It has no action on the 
 dorsal vein of the penis, as this vessel lies in a groove on the dorsum of the penis, 
 and is, therefore, protected from compression by the tendon. (2) The deep 
 transversus perinei is perforated by the venae profundse penis, which come from 
 the corpora cavernosa, so that when it contracts it must compress these veins be-, 
 tween the tense horizontal fibres (Fig. 560, 6). The deep veins of the penis join 
 the common pudendal vein and the plexus Santorini. (3) Lastly, the bulbocav- 
 ernosus is concerned in the hardening of the urethral corpus spongiosum, as it corn- 
 
 Anterior wall of the pelvis with the urogenital septum seen from the front. The corpus cavernosum (4) with the ure- 
 thra (3) is cut across below its exit from the pelvis. 1 , symphysis pubis ; 2, dorsal vein of the penis ; 5, part 
 of the bulbo-cavernosus ; t, deep transversus perinei with its fascia (_/") ; 6, vena profunda penis ; 7, artery and 
 vein of the bulbo-caveruosus. 
 
 presses the bulb of the urethra (Figs. 560, 5, 164). All these muscles are partly 
 under the control of the will, whereby the erection may be increased. Normally, 
 however, their contraction is excited reflexly by stimulation of the sensory nerves 
 of the penis (§ 362, 4). 
 
 The congestion of blood is not complete, else, in pathological cases, continuous erection, as in 
 satyriasis, would give rise to gangrene. The accumulation of the blood in the penis is favored by 
 the fact that the origins of the veins of the penis lie in the corpus cavernosum, which, when it en- 
 larges, must compress them. There are also trabecular, smooth, muscular fibres, which compress the 
 large venous plexus of Santorini. 
 
 That erection is a complex motor act depending on the nervous system, is proved by an experi- 
 ment of Hausmann, who found that section of the nerves of the penis prevented erection in a stal- 
 lion. The imperfect erection which occurs in the female is confined to the corpora cavernosa clito- 
 ridis and the bulbi vestibuli. During erection, the passage from the urethra to the bladder is closed, 
 partly by the swelling of the caput gallinaginis, and partly by the action of the sphincter urethrje, 
 which is connected with the deep transversus perinei. 
 
872 FERTILIZATION OF THE OVUM. 
 
 437. EJACULATION— RECEPTION OF THE SEMEN.— In con- 
 nection with the ejaculation of the seminal fluid, we must distinguish two differ- 
 ent factors — (1) its passage from the testicles to the vesiculae seminales; (2) the 
 act of ejaculation itself. The former is caused by the newly-secreted fluid forcing 
 on that in front of it, by the action of the ciliated epithelium (which lines the 
 epididymis to the beginning of the vas deferens'), and also by the peristaltic 
 movements of the smooth muscular fibres of the vas deferens. Ejaculation, how- 
 ever, requires strong peristaltic contractions of the vasa deferentia and the vesiculae 
 seminales, which are brought about by the reflex stimulation of the ejaculation 
 centre in the spinal cord (§ 362, 5). As soon as the seminal fluid reaches the ure- 
 thra, there is a rhythmical contraction of the bulbo-cavernosus muscle (produced 
 by the mechanical dilatation of the urethra), whereby the fluid is forcibly ejected 
 from the urethra. Both vasa deferentia and vesicula? do not always eject their 
 contents into the urethra simultaneously. With moderate excitement the contents 
 of only one may be discharged. The ischio-cavernosus and deep transversus per- 
 inei contract at the same time as the bulbo-cavernosus, although the former have 
 no effect on the act of ejaculation. In the female also, under normal circum- 
 stances, at the height of the sexual excitement there is a reflex movement corre- 
 sponding to ejaculation. It consists of a movement analogous to that in man. At 
 first there is a reflex peristaltic movement of the Fallopian tube and uterus, pro- 
 ceeding from the end of the tube toward the vagina, and produced reflexly by the 
 stimulation of the genital nerves. Dembo observed that stimulation of the ante- 
 rior upper wall of the vagina in animals caused a gradual contraction of the uterus. 
 By this movement, corresponding to that of the vasa deferentia in man, a certain 
 amount of the mucus normally lining the uterus is forced into the vagina. 
 
 This is followed by the rhythmical contraction of the sphincter cunni (analo- 
 gous to the bulbo-cavernosus), also of the ischio-cavernosus, and deep transversus 
 perinei. The uterus is erected by the powerful contraction of its muscular fibres 
 and round ligaments, while at the same time it descends toward the vagina, its 
 cavity is more and more diminished, and its mucous contents are forced out. When 
 the uterus relaxes after the stage of excitement, it aspirates into its cavity the sem- 
 inal fluid injected into the vestibule {Aristotle, Bischoff}. 
 
 But the suction of the greatly excited uterus is not necessary for the reception of the semen {Aris- 
 totle). The spermatozoa may wriggle by their own movements from the vagina into the orifice of 
 the uterus (Kristeller). The cases of pregnancy where, from some pathological causes (partial 
 closure of the vagina or vulva), the penis has not passed into the vagina during coition, prove that 
 the spermatozoa can traverse the whole length of the vagina, and pass into the uterus. 
 
 438. FERTILIZATION OF THE OVUM.— The ovum is fertilized 
 by a spermatozoon passing into it. 
 
 Swammerdam (f 1685) proved that contact of the semen with the ovum was necessary for fer- 
 tilization. Spallanzani ( 1 768) proved that the fertilizing agent was the spermatozoa, and not the 
 clear, filtered fluid part of the semen, and that the spermatozoa, even after being enormously diluted, 
 were still capable of action. Martin Barry (1850) was the first to observe the entrance of a sperma- 
 tozoon into the ovum of the rabbit. This occurs pretty rapidly, by a boring movement through the 
 vitelline membrane (Leuckhart). The entrance is effected either through the porous canals or the 
 micropyle (Keber, p. 863). 
 
 Theories. — As to the manner in which the spermatozoon affects the ovum, there are great differ- 
 ences of opinion. Aristotle compared it to an action like that of rennet on milk ; Bischoff, to that 
 of yeast on a fermentable mass, i. e., to a catalytic action. These theories, however, are quite un- 
 satisfactory, as we know that the unfertilized ova of the hen, rabbit [ffensen), pig (Bisckoff), salpa 
 (Kuppfer), (but not the frog — Pfliiger) can undergo the initial stages of development as far as the 
 stage of cleavage, and the star fishes even as far as the larval form (Greef). 
 
 Place of Fertilization. — The place where fertilization occurs is either the 
 ovary, as indicated by the occurrence of abdominal pregnancy, or the Fallopian 
 tube, and the numerous recesses in the latter afford a good temporary nidus for the 
 spermatozoa. This view is supported by the occurrence of tubal pregnancy. Thus 
 the spermatozoa must be able to pass through the Fallopian tube to the ovary, 
 
MATURATION OF THE OVUM. 873 
 
 which is probably brought about chiefly by the movements proper to the sperma- 
 tozoa themselves. It is uncertain whether the peristaltic movements of the uterus 
 and Fallopian tube are concerned in this process ; certainly ciliary movement is 
 not concerned, as the cilia of the Fallopian tube act from above downward. 
 When once the ovum has passed unfertilized into the uterus, it is not fertilized in 
 the uterus. It is assumed that the ovum reaches the uterus within two to three 
 weeks (in the bitch, 8 to 14 days). 
 
 Twins occur in 1 in 87 pregnancies, but oftener in warm climates; triplets, 
 1 : 7600 ; four at a birth, 1 : 330,000. More than six at a birth have not been 
 observed. The average number of pregnancies in a woman is 4^. 
 
 Superfecundation. — By this term is understood the fertilization of two ova at the same men- 
 struation, by two different acts of coition. Thus, a mare may throw a foal and a mule, after being 
 covered first by a stallion and then by an ass. A white and a black child have been born as twins 
 by a woman. 
 
 Superfcetation is when a second impregnation takes place at a later period of pregnancy, as in 
 the second or third month. This, however, is only possible in a double uterus, or when menstrua- 
 tion persists until the time of the second impregnation. It is said to occur frequently in the hare. 
 
 Hybrids are produced when there is a cross between different species (horse, ass, zebra — dog, 
 jackal, wolf — goat, ibex — goat, sheep — species of llama — camel, dromedary — tiger, lion — species 
 of pheasant — goose, swan — carp, crucian — species of butterflies). Most hybrids are sterile, espe- 
 cially as regards the formation of properly formed spermatozoa ; while the hybrid females are for 
 the most part fertile with the male of both parents, c. g., the mule ; but the characters of the off- 
 spring tend to return to those of the species of the parents. Very few hybrids are fertile when 
 crossed by hybrids. Tn many species of frogs the absence of hybrids is accounted for by the me- 
 chanical obstacles to fertilization of the ova. 
 
 Tubal Migration of the Ovum. — Under exceptional circumstances, the 
 ovum discharged from a ruptured Graafian follicle passes into the Fallopian tube 
 of the other side, as is proved by the occurrence of tubal pregnancy and preg- 
 nancy of an abnormal rudimentary horn of the uterus, in which case the true 
 corpus luteum is found on the other side of the ovary. This is spoken of as " ex- 
 ternal migration " {Kussmaul, Leopold). This observation coincides with 
 experiment, as granular fluids, e. g., China ink, when injected into the peritoneal 
 cavity, pass into both Fallopian tubes, and are carried by the ciliated epithelium to 
 the uterus {Pinner). In animals, with a double uterus with two orifices, the ova 
 may migrate through the os of the one into the other uterus, a condition which 
 is spoken of as "internal migration." 
 
 439. IMPREGNATION OF THE OVUM— CLEAVAGE— LAY- 
 ERS AND POSITION OF THE EMBRYO.— Maturation of the 
 Ovum. — In birds and mammals important changes occur in the ovum before im- 
 pregnation. The germinal vesicle comes to the surface and disappears from view, 
 while the germinal spot also disappears {Rein). In place of the germinal vesicle, 
 a spindle-shaped body appears. The granular elements of the protoplasmic vitellus 
 arrange themselves around each of the two poles of the spindle, in the form of a 
 star, the double star, or diaster of Fol — nuclear spindle. When this takes place 
 the peripheral pole of the nucleus or altered germinal vesicle, along with some of 
 the cellular substance of the ovum, protrudes upon the surface of the vitellus, 
 where they are nipped off from the ovum in the form of small corpuscles just like 
 an excretory product (Fig. 553). These bodies, which are not made use of in the 
 further development and growth of the ovum, are called polar or directing 
 globules {Fol, Butschli, O. Hertwig), although the elimination of small bodies 
 from the yelk was known to Dumortier [1837], Bischoff, P. J. vanBeneden, Fritz 
 Miiller [1848], Rathke, and others. The remaining part of the germinal vesicle 
 stays within the vitellus and travels back toward the centre of the ovum, to form 
 the female pronucleus {O. Hertwig, Fol, Selenka, E. van Beneden). [Before, 
 however, the altered germinal vesicle travels downward again into the substance 
 of the ovum, it divides again as before, and from it is given off the second polar 
 globule, and then the remainder of the germinal vesicle forms the female pro- 
 
874 
 
 BLASTODERM. 
 
 nucleus. At the same time the vitellus shrinks somewhat within the vitelline 
 membrane.] 
 
 Impregnation. — As a rule, only one spermatozoon penetrates the ovum, and 
 as it does so it moves toward the female pronucleus, while its head becomes sur- 
 rounded with a star ; it then loses its head and cilium or tail, the latter only 
 serving as a motor organ, while the remaining middle piece swells up to form a 
 second new nucleus, the male pronucleus {Fol, Selenka). According to Flem- 
 ming, it is the anterior part of the head, and according to Rein and Eberth, it is 
 the head which is so changed. Thereafter, the male and female pronucleus 
 unite, undergoing amoeboid movements at the same time, to form the new nu- 
 cleus of the fertilized ovum. The female pronucleus receives the male pronucleus 
 in a little depression on its surface. Thereafter the yelk assumes a radiate appear- 
 ance {Rein). [The union of the representatives of the male and female elements 
 forms the first embryonic segmentation sphere or blastosphere.] 
 
 In Echinoderms, O. Hertwig and Fol observed that several embryos were formed when, under 
 abnormal conditions, several spermatozoa penetrated an ovum. The male pronuclei, formed from 
 the several spermatozoa, then fused each with a fragment of the female pronucleus. Under 
 similar circumstances, Born observed in amphibians abnormal cleavage, but no further develop- 
 ment. 
 
 Cleavage of the Yelk. — In an ovum so fertilized the yelk contracts some- 
 what around the newly-formed nucleus, 
 Fig. 561. so that it becomes slightly separated 
 
 from the vitelline membrane, and for 
 the first time the nucleus and the yelk 
 divides into two nucleated spheres. 
 This process is spoken of as complete 
 cleavage or fission. Each of these 
 two cells again divides into two, and 
 the process is repeated, so that 4, 8, 16, 
 32, and so on, spheres are formed (Fig. 
 561). This constitutes the cleavage of 
 the yelk, and the process goes on until the whole yelk is subdivided into numer- 
 ous small, nucleated spheres, the "mulberry mass" or "segmentation 
 spheres " or " morula," or the protoplasmic primordial spheres (20 to 25 y) 
 which are devoid of an envelope. 
 
 Variation of Lines of Cleavage. — According to the observations of Pfliiger, the ova of the 
 frog can be made to undergo cleavage in very different directions, according to the angle between 
 the axis of the egg and the line of gravitation. This, of course, we can alter as we please, by 
 placing the eggs at any angle to the line of gravitation. By the axis of the ovum is meant a line 
 connecting the centre of the black surface and the middle of the white part, which, in the fertilized 
 ovum, is always vertical. In such cases of abnormal cleavage the deposition of the organs takes 
 place from other constituents of the egg than those from which they are formed under normal con- 
 ditions. Under normal circumstances, according to Roux, the first line of cleavage in the frog is in 
 the same direction as the central nervous system. The second intersects the first at a right angle, 
 so as to divide the mass of the ovum into two unequal parts, the larger of which forms the anterior 
 partof the embryo. 
 
 Blastoderm. — During this time the ovum is enlarging by absorption of fluid 
 into its interior. All the cells, from mutual pressure against each other, become 
 polyhedral, and are so arranged as to form a cellular envelope or bladder, the 
 blastoderm, which lies on the internal surface of the vitelline membrane (De 
 Graaf, v. Baer, Bischoff, Caste). A small part of the cells not used in the for- 
 mation of the blastoderm is found on some part of the latter. [In the ovum of 
 the bird, where there is only partial segmentation, the blastoderm is a small 
 round body resting on the surface of the yelk, under the vitelline membrane, so 
 that it does not completely surround the yelk, or a hollow cavity, as in mammals.] 
 The hollow sphere, composed of cells, is called the blastodermic vesicle by 
 Reichert, and in the human embryo it is formed at the 10th to 12th day, in the 
 
 Cleavage of the yelk of the egg of Anchylostomum duo 
 denale. 
 
STRUCTURE OF THE BLASTODERM. 
 
 875 
 
 Fig. 562. 
 
 rabbit at the 4th, the guinea pig at the 3^, the cat 7th, dog nth, fox 14th, 
 ruminantia at the 10th to 12th day, and the deer at the 60th day. 
 
 When the blastoderm grows to 2 mm. (rabbit), whereby the vitelline membrane 
 is distended to a very thin, delicate membrane, then at one part of it there 
 appears the germinal area, the area germinativa, or the embryonal shield (Cosle, 
 .Kolliker), as a round white spot, in which the blastoderm, owing to proliferation 
 of its cells, becomes double. The upper layer is called the ectoderm or epi- 
 blast, and in some animals it consists of several layers of cells, while the lower 
 layer is the endoderm or hypoblast. The hypoblast continues to grow at its 
 edges, so that it ultimately forms a completely closed sack, on which the epiblast 
 is applied concentrically. The embryonal area soon becomes more pear-shaped, 
 and afterward biscuit-shaped. At the same time the surface of the zona pellu- 
 cida develops numerous small, hollow, structureless villi, and is called the primi- 
 tive chorion. 
 
 At the posterior part of the embryonic shield, the primitive streak (Fig. 
 562, I, Pr) appears at first as an elongated circular thickening {Hensen), and 
 later as a longer streak or groove, the primitive groove. This thickening, 
 however, is confined to the epiblast, while the hypoblast is completely unchanged 
 in the region of the streak, and the former consists of three layers of cells. At 
 the same time a new layer of cells is developed between the epiblast and hypo- 
 blast, the mesoderm or mesoblast (Fig. 563, I), which soon extends over the 
 embryonal area, and into the blastoderm. Blood vessels are formed within the 
 mesoblast, and are distributed over the blastoderm to form the area vasculosa. 
 
 Medullary Groove. — A longitudinal groove, the medullary groove, is formed 
 at the anterior part of the embryonal shield, 
 but it gradually extends posteriorly, embrac- 
 ing the anterior part of the primitive streak 
 with its divided posterior end, while the 
 primitive streak itself gradually becomes 
 relatively and absolutely smaller and less dis- 
 tinct, until it disappears altogether (Fig. 
 562, I and II, Pr — Kollikef). 
 
 The position of the embryo is indicated 
 by the central part becoming more trans- 
 parent, — the area pellucida, — which is 
 surrounded by a more opaque part — the area 
 opaca. [The area opaca rests directly upon 
 the white yelk in the fowl, and it takes no 
 share in the formation of the embryo, but 
 gives rise to structures which are temporary, and are connected with the nutrition 
 of the embryo. The embryo is formed in the area pellucida alone.] 
 
 From the epiblast \neuro-epidermal layer] are developed the central nervous 
 system and epidermal tissues, including the epithelium of the sense organs. 
 
 From the mesoblast are formed most of the organs of the body [including 
 the vascular, muscular, and skeletal systems, and, according to some, the connect- 
 ive tissue. It also gives rise to the generative glands and excretory organs]. 
 
 From the hypoblast, epithelio-glandular layer [which is the secretory layer], 
 arise the intestinal epithelium, and that of the glands which open into the intestine. 
 [The mouth and anus being formed by an inpushing of the epiblast, are lined by 
 epiblast, and are sometimes called the stomodceum and protodceum respect- 
 ively.] 
 
 [Structure of the Blastoderm.— Originally it is composed of only two 
 layers, and in a vertical section of it the epiblast consists of a single row of 
 nucleated granular cells arranged side by side, with their long axes placed verti- 
 cally. The hypoblast consists of larger cells than the foregoing, although they 
 vary in size. They are spherical and very granular, so that no nucleus is visible 
 
 Pr, primitive streak ; R, medullary groove ; U, 
 first protovertebra. 
 
876 
 
 STRUCTURES FORMED FROM THE EPIBLAST. 
 Fig. 563. 
 
 V! 
 
 I, The three layers of the blastoderm of the mammalian ovum — Z, zona pellucida ; E, ectoderm, or epiblast ; itt, 
 mesoblast; e, endoderm, or hypoblast. II, Section of an embryo, with six proto vertebrae at the zst day — M, 
 medullary groove; h, somatopleure ; U, protovertebra ; c, chord a dorsalis ; S, the lateral plates divided into 
 two ; e, hypoblast. Ill, Section of an embryo chick at the 2d day in the region behind the heart — M, medulla^ 
 groove ; k, outer part of somatopleure ; «, protovertebra ; c, chorda ; w, Wolffian duct ; K, coelom ; x, inner* 
 part of somatopleure ; y, inner part of splanchnopleure ; A, amniotic fold ; a, aorta; e, hypoblast. IV, Scheme 
 of a longitudinal section of an early embryo. V, Scheme of the formation of the head- and tail-folds — r, head- 
 fold ; D, anterior extremity of the future intestinal tract; S, tail-fold, first rudiment of the cavity of the rectum. 
 VI, Scheme of a longitudinal section through an embryo after the formation of the head- and tail-folds — A o, om- 
 phalo-mesenteric arteries ; V o, omphalo-mesenteric veins ; a, position of the allantoic ; A, amniotic fold. VII, 
 Scheme of a longitudinal section through a human ovum — Z, zona pellucida ; S, serous cavity ; r, union of the 
 amniotic folds ; A, cavity of the amnion; a, allantois; N, umbilical vesicle ; m, mesoblast; A, heart; U, primitive 
 intestine. VIII, Schematic transverse section of the pregnant uterus during the formation of the placenta; U, 
 muscular wall of the uterus ; /, uterine mucous membrane, or decidua vera ; b> maternal part of the placenta, or 
 decidua serontina ;'»*, decidua reflexa; ch, chorion ; A, amnion ; «, umbilical cord; a, allantois, with the urachus; 
 N, umbilical vesicle, with D, the omphalo-mesenteric duct : 1 1, openings of the Fallopian tubes ; G, canal of the 
 cervix uteri. IX, Scheme of a human embryo, with the visceral arches still persistent — A, amnion: V, fore- 
 brain ; M, mid-brain ; H, hind-brain ; N, after-brain ; U, primitive vertebra ; a , eye ; p, nasal pits ; S, frontal 
 process ; y, internal nasal process ; «, external nasal process ; r, superior maxillary process of the 1st visceral 
 arch ; 1, 2, 3 and 4, the four visceral arches, with the visceral clefrs between them ; o, auditory vesicle; k, heart, 
 with e t primitive aorta, which divides into five aortic arches ; f t descending aorta ; am, omphalo-mesenteric ar- 
 tery ; 6, the omphalo-mesenteric arteries on the umbilical vesicle ; c, omphalo-mesenteric vein ; L, Liver, with 
 venae advehentes and revehentes ; D, intestine ; /, inferior cava ; T, coccyx ; all, allantois, with z t one umbilical 
 artery, and x, an umbilical vein. 
 
STRUCTURES FORMED FROM THE MESOBLAST. 877 
 
 in them. The cells form a kind of network, and occur in more than one layer, 
 especially at the periphery. It rests on white yelk, and under it are large spher- 
 ical refractive cells, spoken of as formative cells.] 
 
 The cells of the epiblast, and especially those of the hypoblast, nourish themselves by the direct 
 absorption and incorporation of the constituents of the yelk ipto themselves. The amoeboid move- 
 ments of these cells play a part in the process of absorption. The absorbed particles are changed, 
 or, as it were, digested within the cells, and the product used in the processes of growth and de- 
 velopment {Kollmann). 
 
 440. STRUCTURES FORMED FROM THE EPIBLAST.— 
 Laminae Dorsales. — The medullary groove upon the epiblast (also called 
 outer, serous, sensorial, corneal, or animal layer) becomes deeper (Fig. 563, II). 
 The two longitudinal elevations or lamina dorsales consist of a thickening of the 
 epiblast, and grow up over the medullary groove, to meet each other and coalesce 
 by their free edges in the middle line posteriorly. Thus the open groove is 
 changed into a closed tube — the medullary or neural tube (III). The cells 
 next the lumen of the tube ultimately become the ciliated epithelium lining the 
 central canal of the spinal cord, while the other cells of the nipped-off portion of 
 the epiblast form the ganglionic part of the central nervous system and its pro- 
 cesses. 
 
 Primary Cerebral Vesicles. — [The laminae dorsales unite first in the region 
 of the neck of the embryo, and soon this is followed by the union of those over 
 the future head.] The medullary tube is not of uniform diameter, for at the 
 anterior end it becomes dilated and mapped out by constrictions into the primary 
 vesicles of the brain, which at first are arranged, one behind the other, in the 
 following order : Each one being smaller than the one in frout of it ; the fore- 
 brain (representing the structures from which the cerebral hemispheres are devel- 
 oped) ; the mid-brain (corpora quadrigemina) ; the hind-brain (cerebellum) \ 
 and the after-brain (medulla oblongata), which is gradually continued into the 
 spinal cord (IV and V). The posterior part of the medullary tube has a dilatation 
 at the lumbar enlargement. In birds, the medullary groove remains open in this 
 situation to form a lozenge-shaped dilatation, the sinus rhomboidalis. 
 
 Cranial Flexures. — The anterior part of the medullary tube curves on itself, 
 especially at the junction of the spinal cord and oblongata, between the mid-brain 
 and hind-brain, and again almost at right angles between the fore-brain and mid- 
 brain. [Thus is produced a displacement of the primary vesicles, and the head 
 of the future embryo is mapped off.] At first all the cerebral vesicles are devoid 
 of convolutions and sulci. On each side of the fore-brain there grows out a 
 stalked, hollow vesicle (VI), the primary optic vesicle. The remainder of 
 the epiblast forms the epidermal covering of the body. At an early period we 
 can distinguish the stratum corneum and the Malpighian layer of the skin (§ 283) ; 
 from the former are developed the hairs, nails, feathers, etc. 
 
 Partial Cleavage. — Only a partial cleavage takes place in the eggs of birds and in mesoblastic 
 ova, i. e., only the white yelk in the neighborhood of the cicatricula divides into numerous segmen- 
 tation spheres (Coste, 1848). The cells arrange themselves in two layers, lying one over the other. 
 The upper layer or epiblast is the larger, and contains small, pale cells; the lower layer, or hypo- 
 blast, which at first is not a continuous layer, ultimately forms a continuous layer, but its periphery 
 is smaller than the upper layer, while its cells are larger and more granular. 
 
 Between the epiblast and hypoblast, from the primitive streak outward, is formed the mesoblast, 
 which is said by Kolliker to be due to the division of the cells of the epiblast. It gradually extends 
 in a peripheral direction between the two other layers. All the three layers grow at their periphery. 
 In the mesoblast blood vessels are developed. All the three layers, as they grow, come ultimately 
 to enclose the yelk, so that their margins come together at the opposite pole of the yelk. 
 
 441. STRUCTURES FORMED FROM THE MESOBLAST 
 AND HYPOBLAST.— The mesoblast (vascular layer or middle layer) 
 forms, immediately under the medullary groove, a cylindrical, cellular cord, the 
 chorda dorsalis, or notochord, which is thicker at the tail than at the cephalic 
 
878 FORMATION OF EMBRYO, ETC. 
 
 end (Fig. 563, II, III, c). It is present in all vertebrata, and also in the larval 
 form of the ascidians, but in the latter it disappears in the adult form {Kowa- 
 lewsky). In man it is relatively small. It forms the basis of the bodies of the 
 vertebrae, and around it, as a central core, the substance of the bodies of the 
 vertebrae is deposited, so that they are strung on it, as it were, like beads on a 
 string. After it is formed it becomes surrounded by a double sheath-like covering 
 ( Gegenbaur, Kolliker). 
 
 The recent observations of L. Gerlach and Strahl ascribe the origin of the chorda to the hypoblast. 
 It does not contain chondrin or glutin, but albumin (Jietzius). 
 
 Protovertebrae. — The cells of the mesoblast, on each side of the chorda, 
 arrange themselves into cubical masses, always disposed in pairs behind each other, 
 the protovertebrae (U and u). The first pair correspond to the atlas. At a 
 later period each protovertebra shows a marginal, cellular area and a nuclear area. 
 Only part of it goes to form a future vertebra. The part of the mesoblast lying 
 external to the protovertebras, the lateral plates (II, s), splits into two layers 
 ( Wolff, 1768), an upper one and a lower one, which, however, are united by a 
 median plate at the protovertebrae. The space between the two layers of the 
 mesoblast is called the pleuro-peritoneal cavity, or the coelom (III, K) of 
 Haeckel. The upper layer of the lateral plate becomes united to the epiblast, 
 and forms the cutaneo-muscular plate of German authors, or the somatopleure 
 (III, x), while the inner one unites with the hypoblast to form the intestinal plate 
 of German authors, or the splanchnopleure (III, y). On the surfaces of these 
 plates, which are directed toward each other, the endothelium lining the pleuro- 
 peritoneal cavity is developed. On the surface of the median plate, directed 
 toward the coelom, some cylindrical cells, the " germ epithelium " of Waldeyer, 
 remain, which form the ovarian tubes and the ova (§ 433). 
 
 According to Remak, the skin, the muscles of the trunk, and the blood vessels, and according to 
 His, only the musculature of the trunk, are derived from the somatopleure. Both observers agree 
 that the splanchnopleure furnishes the musculature of the intestinal tract. 
 
 Parablastic and Archiblastic Cells. — According to His the blood vessels, 
 blood, and connective tissue are not developed from true mesoblastic cells, but he 
 asserts that for this purpose certain cells wander in from the margins of the blasto- 
 derm between the epiblast and hypoblast, these cells being derived from outside the 
 position of the embryo, from the elements of the white yelk. His calls these 
 structures parablastic, in opposition to the archiblastic, which belong to the three 
 layers of the embryo. Waldeyer also adheres to the parablastic structure of blood 
 and connective tissue, but he assumes that the material from which the latter is 
 formed is continuous protoplasm, and of equal value with the elements of the 
 blastoderm. 
 
 The hypoblast does not undergo any change at this time ; it applies itself to 
 the inner layer of the mesoblast, as a single layer of cells to form the splanchno- 
 pleure. 
 
 442. FORMATION OF EMBRYO, HEART, PRIMITIVE CIR- 
 CULATION. — Head- and Tail-Folds. — Up to this time the embryo lies 
 with its three layers in the plane of the layers themselves. The cephalic end of 
 the future embryo is first raised above the level of this plane (Fig. 563, V). In 
 front of, and under the head, there is an inflection or tucking in of the layers, 
 which is spoken of as the head-fold (V, r). [It gradually travels backward, so 
 that the embryo is raised above the level of its surroundings.] The raised cephalic 
 end is hollow, and it communicates with the space in the interior of the umbilical 
 vesicle. The cavity in the head is spoken of as the head-gut or fore-gut (V, 
 D). The formation of the fore-gut, by the elevation of the head from the plane 
 of the three layers, occurs on the second day in the chick, and in the dog on the 
 2 2d day. The tail-fold is formed in precisely the same way in the chick on the 
 3d day, and in the dog on the 2 2d day. The caudal elevation, S, also is hollow, 
 
FORMATION OF THE HEART. 879 
 
 and the space within it is the hind-gut, d. Thus the body of the embryo is sup- 
 ported or rests on a hollow stalk, which at first is wide, and communicates with the 
 cavity of the umbilical vesicle. This duct or communication is called the om- 
 phalo-mesenteric duct, or the vitello-intestinal or vitelline duct. The 
 saccular vesicle attached to it in mammals is called the umbilical vesicle (VII, 
 N), while the analogous much larger sack in birds, which contains the yellow nutri- 
 tive yelk, is called the yelk-sack. The omphalo-mesenteric or vitelline duct in 
 course of time becomes narrower, and is ultimately obliterated in the chick on the 
 5th day. The point where it is continuous with the abdominal wall is the abdom- 
 inal umbilicus, and where it is inserted into the primitive intestine, the intestinal 
 umbilicus. 
 
 [Sometimes part of the vitelline duct remains attached to the intestine, and may prove dangerous 
 by becoming so displaced as to constrict a loop of intestine, and thus cause strangulation of the gut:] 
 
 Heart. — Before this process of constriction is complete, some cells are mapped 
 off from that part of the splanchnopleure which lies immediately under the head- 
 gut ; this indicates the position of the heart, which appears in the chick at the end 
 of the first day, as a small, bright red, rhythmically contracting point, the functum 
 saliens, or the ariyiiy] xtvoufiivij of Aristotle. In mammals it appears much later. 
 
 The heart, VI, begins first as a mass of cells, some of which in the centre dis- 
 appear to form a central cavity, so that the whole looks like a pale hollow bud 
 (originally a pair) of the splachnopleure. The central cavity soon dilates ; it 
 grows, and becomes suspended in the coelom by a duplicature like a mesentery 
 (meso-cardium), while the space which it occupies is spoken of as Xht fovea ear- 
 dica. The heart now assumes an elongated tubular form with its aortic portion 
 directed forward and its venous end backward ; it then undergoes a slight/-shaped 
 curve (Fig. 570, 1). From the middle of the 2d day the heart begins to beat in the 
 chick at the rate of about 40 beats per minute. [It is very important to note that 
 at first, although the heart beats rhythmically, it does not contain any nerve cells.] 
 
 From the anterior end of the heart there proceeds from the bulbus aortse the 
 aorta, which passes forward and divides into two arches the primitive aorta; , 
 which then curve and pass backward under the cerebral vesicles, and run in front 
 of the pro to vertebrae. Opposite the omphalo-mesenteric duct each primitive aorta 
 in the chick sends off one, in mammals several (dog 4 to 5), omphalo-mesenteric 
 arteries (VI, A, 0), which spread out to form a vascular network within the meso- 
 blast of the umbilical vesicle. From this network there arise the omphalo-mesen- 
 teric veins, which run backward on the vitelline duct, and end by two trunks in 
 the venous end of the tubular heart. In the chick these veins arise from the sinus 
 terminalis of the subsequent vena terminalis of the area vasculosa. Thus the first 
 or primitive circulation is a closed system, and functionally it is concerned in 
 carrying nutriment and oxygen to the embryo. In the bird the latter is supplied 
 through the porous shell, and the former is supplied up to the end of incubation 
 by the yelk. In mammals both are supplied by the blood vessels of the uterine 
 mucous membrane to the ovum. In birds, owing to the absorption of the con- 
 tents of the yelk-sack, the vascular area steadily diminishes, until ultimately, to- 
 ward the end of the incubation time, the shriveled yelk-sack slips into the abdom- 
 inal cavity. In mammals, the circulation on the umbilical vesicle, i.e., through 
 the omphalo-mesenteric vessels, soon diminishes, while the umbilical vesicle itself 
 shrivels to a small appendix, and the second circulation is formed to replace 
 the omphalo-mesenteric system. The first blood vessels are formed in the chick, 
 in the area vasculosa, outside the position of the embryo, at the last quarter 
 of the first day, before any part of the heart is visible. The blood vessels begin 
 in vaso-formative cells [constituting the " blood islands " of Pander]. At first 
 they are solid, but they soon become hollow (§ 7, A). 
 
 A narrow-meshed plexus of lymphatics is formed in the area vasculosa of the chick {His), and 
 it commun.cates.with the amniotic cavity (A. Budge). 
 
880 VERTEBRAL COLUMN. 
 
 443. FURTHER FORMATION OF THE BODY.— Body Wall. 
 
 — (1) The coelom, or pleuro-peritoneal cavity, becomes larger and larger, while, 
 at the same time, the difference between the body wall and the wall of the intes- 
 tine becomes more pronounced. The latter becomes more separated from the 
 protovertebrse, as the middle plate begins to be elongated to form a mesentery. 
 The body wall, or somatopleure, composed of the epiblast and the outer layer of 
 the cleft mesoblast, becomes thickened by the ingrowth into it of the muscular 
 layer from the muscle plate, and the position of the bones and the spinal nerves 
 from the protovertebrse. These grow between the epiblast and the outer layer of 
 the mesoblast (RemaK). [The somatopleure, or parietal lamina, from each side 
 grows forward and toward the middle line, where they meet to form the body 
 wall, while at the same time the splanchnopleure, or visceral lamina, on each side 
 also grow and meet in the middle line, and when they do so they enclose the 
 intestine. Thus, there is one tube within the other, and the space between is the 
 pleuro-peritoneai cavity.] 
 
 (2) Vertebral Column. — A dorsally-placed structure, called the muscle 
 plate (Remak), is differentiated from each of the protovertebrae ; the remainder 
 of the protovertebra, the protovertebra proper (Kolliker), coalesces with that on 
 the other side, so that both completely surround the chorda,, to form the mem- 
 brana reuniens inferior {Reichert), in the chick on the 3d, and in the rabbit 
 on the 10th day, while at the same time they close over the medullary tube dor- 
 sally in the chick at the 4th day, to form the membrana reuniens superior. 
 Thus, there is a union of the masses of the protovertebrse in front of the medul- 
 lary tube, which encloses the chorda, and represents the basis of the bodies of all 
 the vertebrae, whilst the membrana reuniens superior, pushed between the muscle 
 plates and the epiblast on the one hand and the medullary tube on the other, 
 represents the position of the entire vertebral lamina as well as the intervertebral 
 ligaments between them. In some rare cases the membrana reuniens superior is 
 not developed, so that the medullary tube is covered only by the epiblast (epidermis'), 
 either throughout its entire extent or at certain parts. This constitutes the condi- 
 tion of spina bifida, or, when it occurs in the head, hemicephalia. The vertebral 
 column at this membranous stage is in the same condition as the vertebral column 
 of the cyclostomata (Petromyzon). The membranes of the spinal cord, the spinal 
 ganglia, and spinal nerves are formed from the membrana reuniens superior. 
 
 Lastly, parts of the somatopleures also grow toward the middle line of the back, 
 and insinuate themselves between the muscle plate and the epiblast ; thus, the 
 dorsal skin is formed {Remak). 
 
 In the membranous vertical column there are formed the several cartilaginous 
 vertebrae, the one behind the other, in man at the 6th to 7th week, although at 
 first they do not form closed vertebral arches ; the latter are closed in man about 
 the 4th month. " Each cartilaginous vertebra, however, is not formed from a pair 
 of protovertebrse, L e., the 6th cervical vertebra from the 6th pair of protover- 
 tebrse, but there is a new subdivision of the vertebral column {Remak), so that 
 the lower half of the preceding protovertebra and the upper half of the succeeding 
 protovertebra unite to form the final vertebra. While the bodies are becoming 
 cartilaginous the chorda becomes smaller, but it still remains larger in the inter- 
 vertebral disks. The body of the first vertebra or atlas unites with that of the 
 axis to form its odontoid process (Rathke), and, in addition, it forms the arcus 
 anterior atlantis and the transverse ligament {Hasse). The chorda can be followed 
 upward through the ligamentum suspensorium dentis as far as the posterior part of 
 the sphenoid bone. 
 
 The histogenetic formation of cartilage from the indifferent formative cells takes place by 
 division and growth of the cells, until they ultimately form clear nucleated sacks. The cement sub- 
 stance is probably formed by the outer parts of the cells (parietal substance) uniting and secreting 
 the intercellular substance. It is supposed by some that the latter contains fine canals, which connect 
 the protoplasm of the adjoining cells. 
 
FORMATION OF THE AMNION AND ALLANTOIS. 881 
 
 Visceral Clefts and Arches. — Each side of the cervical region contains 
 four slit-like openings — the visceral clefts or 
 branchial openings (Rathke) ; in the chick the f ig . 564. 
 
 upper three are formed at the 3d, and the 
 fourth on the 4th day. Above the slits are 
 thickenings of the lateral wall, which constitute 
 the visceral or branchial arches. The 
 clefts are formed by a perforation from the fore- 
 gut, but which, perhaps, does not always occur 
 in the chick, mammal and man (His), and they 
 are lined by the cells of the hypoblast. On 
 each side in each visceral arch, i.e., above and 
 below each cleft, there runs an aortic arch, five 
 on each side (Fig. 563, IX). These aortic 
 arches persist in fishes. In man all the slits 
 close except the uppermost one, from which the 
 auditory meatus, the tympanic cavity, and the 
 Eustachian tube are developed (Huschke, Rathke, 
 Reichert). The four visceral arches are, for the 
 most part, made use of later for other forma- Embryo of the mole ( x 7). 
 
 tions (p. 889). 
 
 Primitive Mouth and Anus. — Immediately under the fore-brain, in the 
 middle line, is a thin spot, where there is at first a small depression, and ulti- 
 mately a rupture, forming the primitive oral aperture, which represents both 
 the mouth and the nose. Similarly, there is a depression at the caudal end,^ and 
 the depression ultimately deepens, thus communicating with the hind-gut to form 
 the anus. When the latter part of the process is incomplete there is atresia ani, 
 or imperforate anus. Several processes are given off from the primitive intestine, 
 including the hypoblast and its muscular layers, to form the lungs, the liver, the 
 pancreas, the caecum (in birds), and the allantois. 
 
 The extremities appear at the sides of the body as short, unjointed stumps or 
 projections at the 3d or 4th week in the human embryo (Fig. 564). 
 
 444. FORMATION OF THE AMNION AND ALLANTOIS.— 
 Amnion. — During the elevation of the embryo from its surroundings, imme- 
 diately in front of the head (at the end of the 2d day in the chick), there rises up 
 a fold consisting of the epiblast and the outer layer of the mesoblast, which 
 gradually extends to form a sort of hood over the cephalic end of the embryo 
 (VI, A). In the same way, but somewhat later, a fold rises at the caudal end, 
 and between both along the lateral borders similar elevations occur, the lateral 
 folds (Fig. 563, III, A). All these folds grow over the back of the embryo to 
 meet over the middle line posteriorly, where they unite at the 3d day in the chick 
 to form the amniotic sack. Thus, a cavity which becomes filled with fluid — the 
 amniotic fluid — is developed around the embryo [so that the embryo really 
 floats in the fluid of the amniotic sack]. In mammals, also, the amnion is devel- 
 oped very early, just as in birds (Fig. 563, VII, A). From the middle of preg- 
 nancy onward the amnion is applied directly to the chorion, and united to it by 
 a gelatinous layer of tissue, the tunica medica of Bischoff. 
 
 Amniotic Fluid. — The amnion, and the allantois as well, are formed only in mammals, birds 
 and reptiles, which have hence been called amniota, while the lower vertebrates, which are devoid 
 of an amnion, are called anamnia. Composition. — The amniotic fluid is a clear, serous, alkaline 
 fluid, specific gravity 1007 to ion, containing, besides epithelium, lanugo hairs, ^ to 2 per cent, 
 of fixed solids. Among the latter are albumin ( T 'jto % per cent.), mucin, globulin, a vitelline like 
 body, some grape sugar, urea, ammonium carbonate, very probably derived from the decomposi- 
 tion of urea, sometimes lactic acid and kreatinin, calcic sulphate and phosphate, and common 
 salt. About the middle of pregnancy it amounts to about 1-1.5 kilo. [ 2 - 2- 3-3 K^.], and at the 
 end about 0.5 kilo. The amniotic fluid is of foetal origin, as is shown by its occurrence in birds, 
 
 5° 
 
882 ALLANTOIS. 
 
 and is, perhaps, a transudation through the foetal membranes. Tn mammals, the urine of the foetus 
 forms part of it during the second half of pregnancy (Gusserow). In the pathological condition 
 of Hydramnion, the blood vessels of the uterine mucous membrane secrete a watery fluid. The 
 fluid preserves the foetus, and also the vessels of the fcetal membranes, from mechanical injuries ; it 
 permits the limbs to move freely, and protects them from growing together; and, lastly, it is import- 
 ant for dilating the os uteri during labor. The amnion is capable of contraction at the 7th day in 
 the chick ; and this is due to the smooth muscular fibres which are developed in the cutaneous 
 plate in its mesoblastic portion (Remak), but nerves have not been found. 
 
 Allantois. — From the anterior surface of the caudal end of the embryo there 
 grows out a small double projection, which becomes hollowed out to form a sack 
 projecting into the cavity of the coelom or pleuro-peritoneal cavity (VI, a) ; it 
 constitutes the allantois, and is formed in the chick before the 5th day, and in 
 man during the 2d week. Being a true projection from the hind-gut, the allan- 
 tois has two layers, one from the hypoblast and the other from the muscular layer, 
 so that it is an offshoot from the splanchnopleure. From both sides there pass on 
 to the allantois the umbilical arteries from the hypogastric arteries, and they 
 ramify on the surface of the sack. The allantois grows, like a urinary bladder 
 gradually being distended, in front of the hind-gut in the pleuro-peritoneal cavity 
 toward the umbilicus ; and, lastly, it grows out of the umbilicus, and projects 
 beyond it alongside the omphalo-mesenteric or vitelline duct, its vessels growing 
 with it (VII, a) ; but after this stage it behaves differently in birds and mammals. 
 
 In birds, after the allantois passes out of the umbilicus, it undergoes great development, so that 
 within a short time it lines the whole of the interior of the shell as a highly vascular and saccular 
 membrane. Its arteries are at first branches of the primitive aortse, but with the development of the 
 posterior extremities they appear as branches of the hypogastric arteries. Two allantoidal, or um- 
 bilical veins, proceed from the numerous capillaries of the allantois. They pass backward through 
 the umbilicus, and at first unite with the omphalo-mesenteric veins to join the venous end of the 
 heart. In birds this circulation on the allantois, or second circulation, is respiratory in function, 
 as its vessels serve for the- exchange of gases through the porous shell. This circulation gradually 
 assumes the respiratory functions of the umbilical vesicle, as the latter gradually becomes smaller 
 and smaller, and ceases to be a sufficient respiratory organ. Toward the end of the period of in- 
 cubation, the chick may breathe and cry within the shell (Aristotle) — a proof that the respiratory 
 function of the allantois is partly taken over by the lungs. The allantois is also the excretory organ 
 of the urinary constituents. Into its cavity in mammals the ducts of the primitive kidneys, or the 
 Wolffian ducts, open, but in birds and reptiles, which possess a cloaca, these open into the posterior 
 wall of the cloaca. The primitive kidneys, or Wolffian bodies, consist of many glomeruli, and 
 empty their secretion through the Wolffian ducts into the allantois (in birds into the cloaca), and 
 the secretion passes through the allantois, per the umbilicus, into the peripheral part of the urinary 
 sack. Remak found ammonium and sodium urate, allantoin, grape sugar, and salts in the contents 
 of the allantois. From the eighth day onward, the allantois of the chick is contractile ( Vulpian), 
 owing to the presence of smooth fibres derived from the splanchnopleure. Lymphatics accompany 
 the branches of the arteries (A. Budge). 
 
 Allantois in Mammals. — In mammals and man the relation of the allantois 
 is somewhat different. The first part or its origin forms the urinary bladder, 
 and from the vertex of the latter there proceeds through the umbilicus a tube, the 
 urachus, which is open at first (VIII, a). The blind part of the sack of the al- 
 lantois outside the abdomen is in some animals filled with a fluid like urine. In 
 man, however, this sack disappears during the second month, so that there remains 
 only the vessels which lie in the muscular part of the allantois. In some animals, 
 however, the allantois grows larger, does not shrivel, but obtains through the 
 urachus from the bladder an alkaline turbid fluid, which contains some albumin, 
 sugar, urea, and allantoin. The relations of the umbilical vessels will be described 
 in connection with the foetal membranes. 
 
 445. FCETAL MEMBRANES, PLACENTA, FCETAL CIRCU- 
 LATION. — Decidua. — When a fecundated ovum reaches the uterus, it then 
 becomes surrounded by a special covering, which William Hunter (1775) described 
 as the membrana decidua, because it was shed at birth. We distinguish the 
 decidua vera (Fig, 563, VIII, /), which is merely the thickened, very vascular, 
 softened, more spongy, and somewhat altered mucous membrane of the uterus. 
 
STRUCTURE OF THE DECIDUA VERA. 883 
 
 [Sometimes in a diseased condition, as in dysmenorrhea, the superficial layer of 
 the uterine mucous membrane is thrown off nearly en masse in a triangular form 
 (Fig. 565V This serves to show the shape of the decidua, which is that of the 
 uterus.] When the ovum reaches the uterus it is caught in a crypt or fold of the 
 decidua, and from the latter there grow up elevations around the ovum ; but these 
 elevations are thin, and soon meet over the back of the ovum to form the de- 
 cidua reflexa (VIII, r). At the second to third month there is still a space in 
 the uterus outside the reflexa ; in the fourth month the whole cavity is filled by 
 the ovum. At one part the ovum lies directly upon the d. vera [and that part is 
 spoken of as the decidua serotina], but by far the greatest part of the surface 
 of the ovum is in contact with the reflexa. In the region of the d. serotina the 
 placenta is ultimately formed. 
 
 Structure of the Decidua Vera. — The d. vera at the third month is 4 to 7 mm. thick, and at 
 the fourth only I to 3 mm., and it no longer has any epithelium ; but it is very vascular, and is 
 possessed of lymphatics around the glands and blood vessels (Leopold), and in its loose substance 
 are large round cells (decidua cells — Kolliker), which in the deeper parts become changed into 
 fibre cells — there are also lymphoid cells. The uterine glands, which become greatly developed at 
 
 Fig. 565. 
 
 A dysmenorrhceal membrane laid open. 
 
 the commencement of pregnancy, at the third to the fourth month form non-cellular, wide, bulging 
 tubes, which become indistinct in the later months, and in which the epithelium disappears more 
 and more. The reflexa, much thinner than the vera from the middle of pregnancy, is devoid of 
 epithelium, and is without vessels and glands. Toward the end of pregnancy both deciduse unite. 
 
 The ovum, covered at first with small hollow villi, is surrounded by the decidua. 
 From the formation of the amnion it follows that, after it is closed, a completely 
 closed sack passes away from the embryo to lie next the primitive chorion. This 
 membrane is the "serous covering" of v. Baer (Fig. 563, VII, s), or the false 
 amnion. It becomes closely applied to the inner surface of the chorion, and 
 extends even into its villi. The allantois proceeding from the umbilicus comes 
 to lie directly in contact with the fcetal membrane ; its sack disappears about the 
 second month in man, but its vascular layer grows rapidly and lines the whole of 
 the inner surface of the chorion, where it is found on the eighteenth day (Caste). 
 From the fourth week the blood vessels, along with a covering of connective 
 tissue, branch and penetrate into the hollow cavities of the villi, and completely 
 fill them. At this time the primitive chorion disappears. Thus we have a stage 
 
884 
 
 PLACENTA. 
 
 of general vascularization of the chorion. In the place of the derivative of the 
 zona pellucida we have the vascular villi of the allantois, which are covered by 
 the epiblastic cells derived from the false amnion. This stage lasts only until the 
 third month ; when the chorionic villi disappear all over the surface of the ovum 
 in contact with the decidua reflexa. On the other hand, the villi of the chorion, 
 where they lie in direct contact with the decidua serotina, become larger and more 
 branched. Thus there is distinguished the chorion laeve and c. frondosum. 
 
 The chorion laeve, which consists of a connective-tissue matrix covered externally by several 
 layers of cells, has a few isolated villi at wide intervals. Between the chorion and the amnion is 
 a gelatinous substance (membrana intermedia) or undeveloped connective tissue. 
 
 Placenta. — The large villi of the chorion frondosum penetrate into the tissue 
 of the decidua serotina of the uterine mucous membrane. [It was formerly sup- 
 posed that the chorionic villi entered the mouths of the uterine glands, but the 
 researches of Ercolani and Turner have shown that, although the uterine glands 
 enlarge during the early months of utero-gestation, the villi do not enter the 
 
 Fig. 566. 
 
 Human placental villi. Blood vessels black. 
 
 glands. The villi enter the crypts of the uterine mucous membrane. The glands 
 of the inner layer of the decidua serotina soon disappear.] As the villi grow into 
 the decidua serotina they push against the walls of the large blood vessels, which 
 are similar to capillaries in structure, so that the villi come to be bathed by the 
 blood of the mother in the uterine sinuses, or they float in the colossal decidual 
 capillaries (VIII, b). The villi do not float naked in the maternal blood, but 
 tb*y are covered by a layer of cells derived from the decidua. Some villi, with 
 bulbous ends, unite firmly with the tissue of the uterine part of the placenta to 
 form a firm bond of connection. [The placenta is formed by the mutual inter- 
 growth of the chorionic villi and the decidua serotina.] Thus, it consists of a 
 fcetal part, including all the villi, and a maternal or uterine part, which is 
 the very vascular decidua serotina. At the time of birth, both parts are so firmly 
 united that they cannot be separated. Around the margin of the placenta is a 
 large venous vessel, the marginal sinus of the placenta. [Friedlander found the 
 uterine sinuses below the placental site blocked by giant cells after the 8th month 
 
STRUCTURE OF THE UMBILICAL CORD. 885 
 
 of pregnancy. Leopold confirms this, and found the same in the serotinal veins.] 
 Functions. — The placenta is the nutritive, excretory, and respiratory organ of 
 the foetus (§ 368) ; the latter receives its necessary pabulum by endosmosis from 
 the maternal sinuses through the coverings and vascular wall of the villi in which 
 the foetal blood circulates. [The placenta also contains glycogen.'] 
 
 [Structure. — If a piece of a fresh placenta be teased in normal saline solution, one sees the 
 structure at once. The villi are provided with lateral offshoots, and consist of a connective-tissue 
 framework, containing a capillary network with arteries and veins (Fig. 5°6), while the villi them- 
 selves are covered by a layer of somewhat cubical epithelium.] 
 
 Uterine Milk. — Between the villi of the placenta there is a clear fluid which 
 contains numerous small albuminous globules, and this fluid, which is abundant 
 in the cow, is spoken of as the uterine milk. It seems to be formed by the break- 
 ing up of the decidual cells. It has been supposed to be nutritive in function. 
 [The maternal placenta, therefore, seems to be a secreting structure, while the 
 fcetal part has an absorbing function. The uterine milk has been analyzed by 
 Gamgee, who found that it contained fatty, albuminous, and saline constituents, 
 while sugar and casein were absent.] 
 
 The investigations of Walter show that after poisoning pregnant animals with strychnin, morphia, 
 veratrin, curara, and ergotin, these substances are not found in the fcetus, although many other 
 chemical substances pass into it. 
 
 [Savory found that strychnin injected into a foetus in utero caused tetanic convulsions in the 
 mother (bitch), while syphilis may be communicated from the father to the mother through the 
 medium of the fcetus (Hutchinson). A. Harvey's record of observations on the crossing of breeds 
 of animals — chiefly of horses and allied species — show that materials can pass from the fcetus to 
 the mother.] 
 
 On looking at a placenta, it is seen that its villi are distributed on large areas separated from each 
 other by depressions. This complex arrangement might be compared with the cotyledons of some 
 animals. 
 
 The position of the placenta is, as a rule, on the anterior or posterior wall of the uterus, more 
 rarely on the fundus uteri, or laterally from the opening of the Fallopian tube, or over the internal 
 orifice of the cervix, the last constituting the condition of placenta praevia, which is a very dan- 
 gerous form of placental insertion, as the placenta has to be ruptured before birth can take place, 
 so that the mother often dies from hemorrhage. The umbilical cord may be inserted in the centre 
 ■ of the placenta (insertio centralis), or more toward the margin (ins. marginalis), or the cord may 
 be fixed to the chorion laeve. Sometimes, though rarely, there are small subsidiary placentas (pi. 
 succenturiuta), in addition to the large one (Hyrll). When the placenta consists of two halves, it 
 is called duplex or bipartite, a condition said by Hyrtl to be constant in the apes of the old world. 
 
 Structure of the Cord. — The umbilical cord (48 to 60 cm. [20 to 24 inches] 
 long, 11 to 13 mm. thick) is covered by a sheath from the amnion. The blood 
 vessels make about forty spiral turns, and they begin to appear about the 2d 
 month. [The cause of the twisting is not well understood, but Virchow has 
 shown that capillaries pass from the skin for a short distance on the cord, and 
 they do so unequally, and it may be that this may aid in the production of the 
 torsion.] It contains two strongly muscular and contractile arteries, and one 
 umbilical vein. The two arteries anastomose in the placenta {Hyrll). In addi- 
 tion, the cord contains the continuation of the urachus, the hypoblastic portion 
 of the allantois (VIII, a), which remains until the second month, but afterward 
 is much shrivelled. The omphalo-mesenteric d'iot of the umbilical vesicle (N) is 
 reduced to a thread-like stalk (VIII, D). Wharton's jelly surrounds the 
 umbilical blood vessels. Wharton's jelly is a gelatinous-like connective tissue, 
 consisting of branched corpuscles, lymphoid cells, some connective-tissue fibrils, 
 and even elastic fibres. It yields mucin. It is traversed by numerous juice 
 canals lined by endothelial cells, but other blood and lymphatic vessels are absent. 
 Nerves occur 3-8-1 1 cm. from the umbilicus (Schott, Valentin). 
 
 The fcetal circulation, which is established after the development of the 
 allantois, has the following course : The blood of the foetus passes. from the hypo- 
 gastric arteries through the two umbilical arteries, through the umbilical cord to 
 the placenta, where the arteries split up into capillaries. The blood is returned 
 
886 CHRONOLOGY OF HUMAN DEVELOPMENT. 
 
 from the placenta by the umbilical vein, although the color of the blood cannot 
 be distinguished from the venous or impure blood in the umbilical arteries. The 
 umbilical vein (Fig. 573, 3, u), returns to the umbilicus, passes upward under the 
 margin of the liver, gives a branch to the vena portae (a), and runs as the ductus 
 venosus into the inferior vena cava, which carries the blood into the right 
 auricle. Directed by the Eustachian valve and the tubercle of Lower (Fig. 570, 
 
 6, t, L), the great mass of the blood passes through the foramen ovale into the 
 left auricle, from which it cannot pass backward into the right auricle, owing to 
 the presence of the valve of the foramen ovale. From the left auricle it passes 
 into the left ventricle, aorta and hypogastric arteries, to the umbilical arteries. 
 The blood of the superior vena cava of the foetus passes from the right auricle 
 into the right ventricle (Fig. 570, 6, Cs). From the right ventricle it passes into 
 the pulmonary artery (Fig. 570, "],f), and through the ductus arteriosus of 
 Botalli (B) into the aorta. There are, therefore, two streams of blood in the 
 right auricle which cross each other, the descending one from the head through 
 the superior vena cava, passing in front of the transverse one from the inferior 
 vena cava to the foramen ovale.] Only a small amount of the blood passes 
 through the as yet small branches of the pulmonary artery to the lungs (Fig. 5 70, 
 
 7, 1, 2). The course of the blood makes it evident that the head and upper 
 limbs of the foetus are nourished by purer blood than the remainder of the trunk, 
 which is supplied with blood mixed with the blood of the superior vena cava. 
 After birth the umbilical arteries are obliterated, and become the lateral liga- 
 ments of the bladder, while their lower parts remain as the superior vesical arte- 
 ries. The umbilical vein is obliterated, and remains as the ligamentum teres, or 
 round ligament of the liver, and so is the ductus venosus Arantii. Lastly, the 
 foramen ovale is closed, and the ductus arteriosus is obliterated, the latter form- 
 ing the lig. arteriosus. 
 
 The condition of the membranes where there are more foetuses than one: (1) With twins 
 there are two completely separated ova, with two placentae and two decidual reflexae. (2) Two 
 completely separate ova may have only one reflexa, whereby the placenta? grow together, while 
 their blood vessels remain distinct. The chorion is actually double, but cannot be separated into 
 two lamellae at the point of union. (3) One reflexa, one chorion, one placenta, two umbilical 
 cords and two amnia. The vessels anastomose in the placenta. In this case there is one ovum' 
 with a double yelk, or with two germinal vesicles in one yelk. (4) As in (3), but only one amnion, 
 caused by the formation of two embryos in the same blastoderm of the same germinal vesicle. 
 
 Formation of the foetal membranes in animals. — The oldest mammals have no placenta or 
 umbilical vessels ; these are the Mammalia implacentalia ( Owen), including the monotremata 
 and marsupials. The second group includes the Mammalia placentalia. Among these (a) the 
 non-deciduata possess only chorionic villi supplied by the umbilical vessels, which project into the 
 depressions of the uterine mucous membrane, and from which they are pulled out at birth (PI. dif- 
 fusa, e.g., pachydermata, cetacea, solidungula. camelidaa). In the ruminants the villi are arranged 
 in groups or cotyledons, which grow into the uterine mucous membrane, from which they are 
 pulled out at birth, (b) In the deciduata there is such a firm union between the chorionic villi 
 with the uterine mucous membrane, that the uterine part of the placenta comes away with the foetal 
 part at birth. In this case the placenta is either zonary (carnivora, pinnipedia, elephant), or dis- 
 coid (apes, insectivora, edentata, rodentia). 
 
 446. CHRONOLOGY OF HUMAN DEVELOPMENT.—Development during the 
 1st Month. — At the I2th-I3th day the ovum is saccular (5.5 mm. and 3 mm. in diameter) ; there is 
 simply the blastodermic vesicle, with the blastoderm at one part, consisting of two layers ; the zona 
 pellucida beset with small villi (Reichert). At the I5th-l6th day the ovum (5-6 mm.) is covered 
 with simple cylindrical villi. The zona pellucida consists of embryonic connective tissue covered 
 with a layer of flattened epithelium. The primitive groove and the laminae dorsales appear. Then 
 follows the stage when the allantois is first formed. At the 15th— iSth day Coste investigated an 
 ovum. It was 13.2 mm. long, with small branched villi; the embryo itself was 2.2 mm. long, of a 
 curved form, and with a moderately enlarged cephalic end. The amnion, umbilical vesicle with a 
 wide vitelline duct, and the allantois were developed, the last already united to the false amnion. 
 The S-shaped heart lies in the cardiac cavity, shows a cavity and a bulbus aortae, but neither 
 auricles nor ventricles. The visceral arches and clefts are indicated, but they are not perforated. 
 The omphalo-mesenteric vessels forming the first circulation on the umbilical vesicle are developed, 
 the duct (vitelline) is still quite open, and two primitive aorta? run in front of the proto vertebrae. 
 The allantois attached to the foetal membranes is provided with blood vessels. The two omphalo- 
 
CHRONOLOGY OF HUMAN DEVELOPMENT. 
 
 887 
 
 mesenteric veins unite with the two umbilical veins, and pass to the venous end of the heart. The 
 mouth is in process of formation. The limbs and sense organs absent ; the Wolffian bodies pro- 
 bably present. . 
 
 At the 20th day all the visceral arches are formed, and the clefts are perforated. The mid-brain 
 forms the highest-part of the brain, while the two auricles appear in the heart. The connection with 
 the umbilical vesicle is still moderately wide. The embryo is 2.6-3.3-4 mm. long, while the head 
 is turned to one side (His). At a slightly later period the temporal and cervical flexures take place, 
 and the hemispheres appear more prominently ; the vitelline duct is narrowed, the position of the 
 liver is indicated, while the limbs are still absent (His). 
 
 At the 21st day the ovum is 13 mm. long and the embryo 4-4.5 mm. ; the umbilical vesicle 2.2 
 mm., and the intestine almost closed. Three branchial clefts, Wolffian bodies laid down, and the 
 first appearance of the limbs, three cerebral vesicles, auditory capsules present (R. Wagner). Coste 
 also observed, in addition, the n asal pits, eye, the opening for the mouth, with the frontal and supe- 
 rior maxillary processes, the heart with two ventricles and two auricles. 
 
 End of the 1st Month. — The embryos of 25-28 days are characterized by the distinctly stalked 
 condition of the umbilical vesicle and the distinct presence of limbs. Size of the ovum, 17.6 mm.; 
 embryo, 13 mm. ; umbilical vesicle, 4.5 mm., with blood vessels. 
 
 2d Month. — The embryos of 28-35 days are more elongated, and all the branchial clefts are 
 closed except the first. The allantois has now only three vessels, as the right umbilical vein is ob- 
 literated. At the 5th week the nasal jojjs are united by furrows with the angle of the mouth, which 
 close to form canals at the 6th week (Toldt). At 35-42 days the nasal and oral orifices are sepa- 
 rated, the face is flat, the limbs show three divisions, the toes are not so sharply defined as the fingers. 
 The outer ear appears as a low projection at the 7th week. The Wolffian bodies are much reduced 
 in size. 
 
 End of the 2d Month. — Ovum, 6y£ cm.; villi, 1.3 mm. long; the circulation on the umbilical 
 vesicle has disappeared; embryo, 26 mm. long, and weighs 4 grammes. Eyelids and uase. present, 
 umbilical cord 8 mm. long, ablominal cavity closed, ossification beginning in the lower jaw, clavicle, 
 ribs, bodies of the vertebrae ; sex indistinct, kidneys laid down. 
 
 3d Month. — Ovum as large as a goose's egg, beginning of the placenta, embryo 7-9 cm., weigh- 
 ing 20 grammes, and is now spoken of as a. foetus. External ear well formed, umbilical cord 7 cm. 
 long. Beginning of the difference between the sexes in the external genitals, umbilicus in the lower 
 fourth of the linea alba. 
 
 4th Month. — Foetus, 17 cm. long, weighing 120 grammes, sex distinct, hair and nails beginning 
 to be formed, placenta weighs 80 grammes, umbilical cord 19 cm. lonj, umbilicus above the lowest 
 fourth of the linea alba, contractions or movements of the limbs, meconium in the intestine, skin 
 with blood vessels shining through it, eyelids closed. 
 
 5th Month. — Foetus, 18 to 27 cm., weighing 284 grammes ; hair on the head and lanugo dis- 
 tinct; skin still somewhat red and thin, and covered with vernix caseosa (g 287, 2), is less trans- 
 parent; weight of placenta, 178 grammes ; umbilical cord, 31 cm. long. 
 
 6th Month. — Foetus, 28 to 34 cm., weighing 634 grammes: lanugo more abundant; vernix more 
 abundant; testicles in the abdomen ; pupillary membrane and eyelashes present ; meconium in the 
 large intestine. 
 
 7th Month.— Foetus, 28.34 cm. long, weighing 1218 grammes, the descent of the testicles begins 
 — one testicle in the inguinal canal, the eyes open, the pupillary membrane often absorbed at its 
 centre in the 28th week. In the brain other fissures are formed besides the primary ones. The 
 foetus U capable of living independently. At the beginning of this month there is a centre of ossi- 
 fication in the os calcis. 
 
 8th Month. — Foetus, 42 cm., weighing 1.5 tp 2 kilos. (3.3 to 4.4 lbs.), hair of the head abun- 
 dant, 1.3 cm. long, nails with a small margin, umbilicus below the middle of the linea alba, one 
 testicle in the scrotum. 
 
 gth Month. — Foetus, 47 cm., weighing 2j£ kilos. (5.5 lbs.), and is not distinguishable from the 
 child at the full period. 
 
 Foetus at the Full Period. —Length of body, 51 cm. [20 inches], weight 3^ kilos. [7 lbs.], 
 lanugo present only on the shoulders, skin white. The nails of the fingers project beyond the tips 
 of the fingers, umbilicus slightly below the middle of the linea alba. The centre of ossification in 
 the lower epiphysis of the femur is 4 to 8 mm. broad. 
 
 Period of Gestation or Incubation. 
 
 Days. 
 
 Coluber 12 
 
 Hen \ 
 
 Duck / ZI 
 
 Goose 29 
 
 Stork 42 
 
 Cassowary .... 65 
 Mouse 24 
 
 Rabbit , 
 Hare . 
 
 Rat ... . 
 Guinea pig 
 Cat ... . 
 Marten . . 
 
 Days. 
 • \Z2 
 Weeks. 
 
 . . .5 
 . . . 7 
 
 } 
 
 Dog . . 
 Fox . . 
 Foumart 
 Badger . 
 Wolf . 
 Lion . . 
 Pig 
 
 Weeks. 
 
 }.„ 
 
 . '4 
 17 
 
 Sheep . . 
 Goat . , . 
 Roe . . . 
 Bear . . . 
 Small apes 
 
 Deer 36-40 
 
 Woman 40 
 
 H 
 
 Weeks. 
 . . 21 
 . . 22 
 . ■ 24 
 
 " }3° 
 
 Horse, Camel, 13 months; Rhinoceros, 18 months; and the Elephant, 24 months (Schenk) 
 Limitation ui the supply of O to eggs, during incubation, leads to the formation of dwarf chicks 
 
888 FORMATION OF THE OSSEOUS SYSTEM. 
 
 447. FORMATION OF THE OSSEOUS SYSTEM.— Vertebral Column.— The ossi- 
 fication of the vertebra begins at the 8th to the 9th week, and first of all there is a centre in each 
 vertebral arch, then a centre is formed in the body behind the chorda (Robin), which, however, is 
 composed of two closely apposed centres. At the 5th month the osseous matter has reached the 
 surface, the chorda within the body of the vertebra is compressed ; the three parts unite in the 1st 
 year. The atlas has one centre in the anterior arch and two in the posterior ; they unite at the 3d 
 year. The epistropheus has a centre at the 1st year. The three points of the sacral vertebrae unite 
 or anchylose between the 2d and the 6th year, and all the vertebrae (sacral) become united to form 
 one body between the 18th and 25th years. Each of the four coccygeal vertebrae has a centre from 
 the 1st to 10th year. The vertebras in later years produce I to 2 centres in each process; I to 2 
 centres in each transverse process ; I in the mammillary process of the lumbar vertebrae ; and one 
 in each articular process (8 to 15 years). Of the upper and under surfaces of the body of a vertebra 
 each fcms an epiphysial, thin osseous plate, which may still be visible at the 20th year. Groups of 
 the cells of the chorda are still to be found within the intervertebral disks. As long as the coccy- 
 geal vertebrae, the odontoid process, and the base of the skull are cartilaginous, they still contain 
 the remains of the chorda (H. Milller). The coccygeal vertebrae form the tail, and they originally 
 project in man like a tail (Fig. 563, IX, T), which is ultimately covered over by the growth of the 
 soft parts (His). 
 
 The ribs bud out from the protovertebrae, and are represented on each vertebra. The thoracic 
 ribs become cartilaginous in the 2d month and grow forward into the wall of the chest, whereby the 
 seven upper ones are united by a median portion (Rathke), which represents the position of one- 
 half of the sternum, and when the two halves meet in the middle line the sternum is formed. When 
 this does not occur we have the condition of cleft sternum. At the 6th month there is a centre 
 of ossification in the manubrium, then 4 to 13 in pairs in the body, and I in the ensiform process. 
 Each rib has a centre of ossification in its body at the 2d month, and at the 8th to 14th one in the 
 tubercle and another in the head. These anchylose at the 14th to 25th year. Sometimes cervical 
 ribs are present in man, and they are largely developed in birds. 
 
 The skull. — The chorda extends forward into the axial part of the base to the sphenoid bone. 
 The skull at first is membranous, or the primordial cranium ; at the second month the. basal 
 portion becomes cartilaginous, including the occipital bone, except the upper half, the anterior 
 and posterior part and wings of the sphenoid bone, the petrous part and mastoid process of the tem- 
 poral bone, the ethnoid with the nasal septum, and the cartilaginous part of the nose. The other 
 parts of the skull remain membranous, so that there is a cartilaginous and a membranous primor- 
 dial cranium. 
 
 I. The occipital bone has a centre of ossification in the basilar part of the 3d month, and one 
 in the condyloid part and another in the fossa cerebelli, while there are two centres in the mem- 
 branous cerebral fossae. The four centres of the body unite during intra-uterine life. All the other 
 parts unite at the 1st to 2d year. 
 
 II. The post-sphenoid. — From the 3d month it has two centres in the sella turcica, two in the 
 sulcus caroticus, two in both great wings, which also form the lamina externa of the pterygoid pro- 
 cess, while the non-cartilaginous and previously formed inner lamina arises from the superior max- 
 illary process of the first branchial arch. During the first half of fetal life these centres unite as 
 far as the great wings ; the dorsum sellae and the clinoid process, as far as the synchondrosis spheno- 
 occipitalis, are still cartilaginous, but they ossify at the 13th year. 
 
 III. The pre-sphenoid at the 8th month has two centres in the small wings and two in the 
 body. At the 6th month they unite, but cartilage is still found within them even at the 13th year. 
 
 IV. The ethmoid has a centre in the labyrinth at the 5th month, then in the 1st year a centre 
 in the central lamina. They unite about the 5th or 6th year. 
 
 V. Among the membranous bones are the inner lamina of the pterygoid process (one centre), 
 the upper half of the tabular plate of the occipital (two points), the parietal bone (one centre in 
 the parietal eminence), the frontal bone (one double centre in the frontal eminence), three small 
 centres in the nasal spine, spina trochlearis and zygomatic process, nasal (one centre), the edges of 
 the parietal bones (one centre), the tympanic ring (one centre), the lachrymal, vomer, and inter- 
 maxillary bone. 
 
 The facial bones are intimately related to the transformations of the branchial arches and 
 branchial clefts. The median end of the first branchial arch projects inward from each side 
 toward the large oral aperture. It has two processes, the superior maxillary process, which 
 grows more laterally toward the side of the mouth, and the inferior maxillary process, which 
 surrounds the lower margin of the mouth (Fig. 563, IX). From above downward there grows as 
 an elongation of the basis cranii the frontal process (s), a broad process with a point (y) at its 
 lower and outer angle, the inner nasal process. The frontal and the superior maxillary processes 
 (r) unite with each other in such a way that the former projects between the two latter. At the 
 same time there is anchylosed with the superior maxillary process the small external nasal process 
 (»), a prolongation of the lateral part of the skull, and lying above the superior maxillary process. 
 Between the latter and the outer nasal process is a slit leading to the eye (a). Thus the mouth is 
 cut off from the nasal apertures which lie above it. But the separation is continued also within the 
 mouth ; the superior maxillary process produces the upper jaw, the nasal process, and the intermax- 
 
BRACHIAL CLEFTS AND THEIR RELATION TO NERVES. 889 
 
 illary process ( Goethe) — the latter is present in man, but is united to the upper jaw. The inter- 
 maxillary bone, which in many animals remains as a separate bone (os incisivum), carries the 
 incisor teeth. At the 9th week the hard palate is closed, and on it rests the septum of the nose, 
 descending vertically from the frontal process. The lower jaw is formed from the inferior maxil- 
 lary process. At the circumference of the oral aperture the lips and the alveolar walls are formed. 
 The tongue is formed behind the point of the union of the second and third branchial arches [His] ; 
 while, according to Born, it is formed by an intermediate part between the inferior maxillary pro- 
 cesses. 
 
 These transformations may be interrupted. If the frontal process remains separate from the 
 superior maxillary processes, then the mouth is not separated from the nose. This separation may 
 occur only in the soft parts, constituting hair-lip (Fig. 567) ; or it may involve the hard palate, con- 
 stituting cleft palate. Both conditions may occur on one or both sides. From the posterior part 
 of the first branchial arch are formed the malleus (ossified at the 4th month), and Meckel's carti- 
 lage (Fig. 568), which proceeds from the latter behind the tympanic ring as a long cartilaginous 
 process, extending along the inner side of the lower jaw, almost to its middle. It disappears after 
 the 6th month ; still its posterior part forms the internal lateral ligament of the maxillary articula- 
 tion. Near where it leaves the malleus is the processus Folii (Baumuller). A part of its median 
 end ossifies, and unites with the lower jaw. The lower jaw is laid down in membrane from the 
 first branchial arch, while the angle and condyle are formed from a cartilaginous process. The 
 union of both bones to form the chin occurs at the 1st year. From the superior maxillary process 
 are formed the inner lamella of the pterygoid process, the palatine process of .the upper jaw, and 
 the palatine bone at the end of the 2d month, and, lastly, the malar bone. 
 
 The second arch \hyoid~\, arising from the temporal bone, and running parallel with the first 
 arch, gives rise to the stapes (although, according to Salensky, this is derived from the first arch), 
 the eminentia pyramidalis, with the stapedius muscle, the incus, the styloid process of the temporal 
 
 Fig. 567. 
 
 Fig. 568. 
 
 Fig. 567. — Hare-lip on the left side. Fig. 568. — Inner view of the lower jaw of an embryo pig 3 inches long (X z%). 
 tnk, Meckel's cartilage ; rf, dentary bone ; cr, coronoid process ; or, articular process (condyle) ; ag, angular 
 process ; ml, malleus ; mb, manubrium. 
 
 bone, the (formerly cartilaginous) stylo-hyoid ligament, the smaller cornu of the hyoid bone, and, 
 lastly, the glosso-palatine arch (His). 
 
 The third arch [thyro-hyoid] forms the greater cornu and body of the hyoid bone and the 
 pharyngo-palatine arch (His). 
 
 The fourth arch give's rise to the thyroid cartilage (His). 
 
 Branchial Clefts. — The Jirsl branchial or visceral is represented by the external auditory meatus, 
 the tympanic cavity, and the Eustachian tube ; all the other clefts close. Should one or other of 
 the clefts remain open, a condition that is sometimes hereditary in some families, a cervical fistula 
 results, and it may be f >rmed either from without or within. Sometimes only a blind diverticulum 
 remains. Branchiogenic tumors and cysts depend upon the branchial arches (R. Volkmann). 
 
 [Relation of Branchial Clefts to Nerves. — It is important to note that the clefts in front of 
 the mouth (pre-oral), and those behind it (post-oral), have a relation to certain nerves. The 
 lachrymal slit between the frontal and nasal processes is supplied by the first division of the tri- 
 geminus. The nasal slit between the superior maxillary process and the nasal process is supplied by 
 the bifurcation of the third nerve. The oral cleft, between the superior maxillary processes and the 
 mandibular arch, is supplied by the second and third divisions of the trigeminus. The first post- 
 oral or tympanic-Eustachian cleft, between the mandibular arch (1st) and the hyoid arch, is sup- 
 plied by the portio dura. The next cleft is supplied by the glossopharyngeal, and the succeeding 
 clefts by branches of the vagus.~\ 
 
 The thymus and thyroid glands are formed as paired diverticula from the epithelium covering 
 the branchial arches. The epithelium of the last two clefts does not disappear (pig), but proliferates 
 and pushes inward cylindrical processes, which develop into two epithelial vesicles, the paired com- 
 mencement of the thyroid glands. These vesicles have at first a central slit, which communicates 
 with the pharynx ( Wolfler). According to His, the thyroid gland appears as an epithelial vesicle 
 
890 DEVELOPMENT OF THE BONES OF THE LIMBS. 
 
 in the region of the 2d pair of visceral arches in front of the tongue — in man at the 4th week. Solid 
 buds, which ultimately become hollow, are given off from the cavity in the centre of the embryonic 
 thyroid gland. The two glands ultimately unite together. The only epithelial part of the thymus 
 which remains is the so-called concentric corpuscles (p. 178). According to Born, this gland is a 
 diverticulum from the 3d cleft, while His ascribes its origin to the 4th and 5th aortic arches 
 in man at the 4th week. The carotid gland is of epithelial origin, being a variety of the 
 thyroid (Stieda). 
 
 The Extremities. — The origin and course of the nerves of the brachial plexus show that the 
 upper extremity was originally placed much nearer to the cranium, while the position of the poste- 
 rior pair corresponds to the last lumbar and the 3d or 4th sacral vertebra; {His). 
 
 The clavicle, according to Bruch, is not a membrane bone, but is formed in cartilage like the 
 furculum of birds ( Gegenbaur). At the 2d month it is four times as large as the upper limb ; it is 
 the first bone to ossify at the 7th week. At puberty a sternal epiphysis is formed. Episternal bones 
 must be referred to the clavicles {Gotte). Ruge regards pieces of cartilages existing between the 
 clavicle and the sternum, as the analogues of the episternum of animals. The clavicle is absent in 
 many mammals (carnivora) ; it is very large in flying animals, and in the rabbit is half membranous. 
 The furculum of birds represents the united clavicles. 
 
 The scapula at first is united with the clavicle (Rathke, Gotte), and at the end of the 2d month 
 
 Fig. 569. 
 
 Centres of ossification of the innominate bone. 
 
 it has a median centre of ossification, which rapidly extends. Morphologically, the accessory centre 
 in the coracoid process is interesting ; the latter also forms the upper part of the articular surface. 
 In birds the corresponding structure forms the coracoid bone, and is united with the sternum ; 
 while in man only a membranous band stretches from the tip of the coracoid process to the sternum. 
 The long, basal, osseous strip corresponds to the suprascapular bone of many animals. The other 
 centres of ossification are —one in the lower angle, two or three in the acromion, one in the articular 
 surface, and an inconstant one in the spine. Complete consolidation occurs at puberty. 
 
 The humerus ossifies at the 8th to the 9th week in its shaft. The other centres are —one in the 
 upper epiphysis, and one in the capitellum (1st year) ; one in the great tuberosity and one in the 
 small tuberosity (2d year) ; two in the condyles (5th to 10th year); one in the trochlea (12th year). 
 The epiphyses unite with the shaft at the 16th to 20th year. 
 
 The radius ossifies in the shaft at the 3d month. The other centres are — one in the lower epi- 
 physis (5th year), one in the upper (6th year), and an inconstant one in the tuberosity, and one in 
 the styloid process. They unite at puberty. 
 
 The ulna also ossifies in the shaft at the 3d month. There is a centre in the lower end (6th year), 
 two in the olecranon (nth to 14th year), and an inconstant one in the coronoid process, and one in 
 the styloid process. They consolidate at puberty. 
 
CHEMICAL COMPOSITION OF BONE. 891 
 
 The carpus is arranged in mammals in two rows. The first row contains three bones — the 
 radial, intermediate and ulnar bones. In man these are represented by the scaphoid, semilunar 
 and cuneiform bones ; the pisiform is only a sesamoid hone in the tendon of the flexor carpi ulnaris. 
 
 The second row really consists of as many bones as there are digits (eg., salamander). In man 
 the common position of the 4th and 5th fingers is represented by the unciform bone. Morphologic- 
 ally, it is interesting to observe that an os centrale, corresponding to the os carpale centrale of 
 reptiles, amphibians, and some mammals, is formed at first, but disappears at the end of the 3d 
 month, or unites with the scaphoid. Only in very rare cases is it persistent. All the carpal bones are 
 cartilaginous at birth. They ossify as follows : Os magnum, unciform (1st year), cuneiform (3d year), 
 trapezium, semilunar (5th year), scaphoid (6th year), trapezoid (7th year), and pisiform (12th year). 
 
 The metacarpal bones have a centre in their diaphyses at the end of the 3d month, and so 
 have the phalanges. All the phalanges and the first bone of the thumb have their cartilaginous 
 epiphyses at the central end, and the other metacarpal bones at the peripheral end, so that the first 
 bone of the thumb is to be regarded as a phalanx. The epiphyses of the metacarpal bones ossify at 
 the 2d, and those of the phalanges at the 3d year. They consolidate at puberty. 
 
 The innominate bone, when cartilaginous, consists of two parts — the pubis and the ischium 
 (Rosenberg). Ossification begins with three centres — one in the ilium (3d to 4th month), one in the 
 descending ramus of the ischium (4th to 5th month), one in the horizontal ramus of the pubis (5th 
 to 7th month). Between the 6th to the 14th year three centres are formed where the bodies of the 
 three bones meet in the acetabulum, another in the superficies auricularis, and one in the symphysis. 
 Other accessory centres are : One in the anterior inferior spine, the crest of the ilium, the tuberosity 
 and the spine of the ischium, the tuberculum pubis, eminentia ileopeclinea, and floor of the ace- 
 tabulum. At first the descending ramus of the pubis and the ascending ramus of the ischium unite 
 at the 7th to 8th year; the Y-shaped suture in the acetabulum remains until puberty (Fig. 569). 
 
 The femur has its middle centre at the end of the 2d month. At birth there is a centre in the 
 lower epiphysis ; slightly later in the head. In addition, there is one in the great trochanter (3d to 
 I Ith year), one in the lesser trochanter (13th to 14th year), two in the condyles (4th to 8th year) ; 
 all unite about the time of puberty. The patella is a sesamoid bone in the tendon of the quadriceps 
 femoris. It is cartilaginous at the 2d month, and ossifies from the 1st to the 3d year. 
 
 The tarsus generally resembles the carpus. The os ealcis ossifies at the beginning of the 7th 
 month, the astragalus at the beginning of the 8th month, the cuboid at the end of the 10th, the 
 scaphoid (1st to 5th year), the I and II cuneiform (3d year), and the III cuneiform (4th year). 
 An accessory centre is formed in the heel of the calcaneum at the 5th to loth year, which consoli- 
 dates at puberty. 
 
 The metatarsal bones are formed like the metacarpals, only later. 
 
 [Histogenesis of Bone. — The great majority of our bones are laid down in cartilage, or are 
 preceded by a cartilaginous stage, including the bones of the limbs, backbone, base of the skull, 
 sternum and ribs. These consist of solid masses of hyaline cartilage covered by a membrane, 
 which is identical with and ultimately becomes the periosteum. The formation of bone, when 
 preceded by cartilage, is called endochondral bone. Some bones, such as the tabular bones of 
 the vault of the cranium, the facial bones, and part of the lower jaw, are not preceded by cartilage. 
 In the latter there is merely a membrane present, while from and in it the future bone is formed. 
 It becomes the future periosteum as well. This is called the intra-membranous or periosteal 
 mode of formation.] 
 
 [Endochondral Formation. — (1) The cartilage has the shape of the future bone, only in minia- 
 ture, and it is covered with periosteum. In the cartilage an opaque spot or centre of ossification 
 appears, due to the deposition of lime salts in its matrix. The cartilage cells proliferate in this 
 area, but the first bone is formed under the periosteum in the shaft, so that an osseous case, like a 
 muff, surrounds the cartilage. This bone is formed by the subperiosteal osteoblasts. (2) Blood 
 vessels, accompanied by osteoblasts and connective tissue, grow into the cartilage from the osteogenic 
 layer of the periosteum (periosteal processes of Virchow), so that the cartilage becomes channelled 
 and vascular. As these channels extend they open into the already enlarged cartilage lacuna?, 
 absorption of the matrix taking place, while other parts of the cartilaginous matrix become calcified. 
 Thus, a series of cavities, bounded by calcified cartilage — the primary medullary cavities — are 
 formed. They contain the primary or cartilage marrow, consisting of blood vessels, osteoblasts, 
 and osteoclasts, carried in from the osteogenic layer of the periosteum, and, of course, the cartilage 
 cells that have been liberated from their lacunae. (3) The osteoblasts are now in the interior of the 
 cartilage, where they dispose themselves on the calcified cartilage, and secrete or form around them 
 an osseous matrix, thus enclosing the calcified cartilage, while the osteoblasts themselves become 
 embedded in the products of their own activity and remain as bone corpuscles. Bone, therefore, 
 is at first spongy bone, and as the primary medullary spaces gradually become filled up by new 
 osseous matter it becomes denser, while the calcified cartilage is gradually absorbed. It is to be 
 remembered that, pari passu with the deposition of the new bone, bone and cartilage are being 
 absorbed by the osteoclasts.] 
 
 Chemical Composition of Bone. — Dried bone contains £ of organic matter or ossein, from 
 which gelatin can be extracted by prolonged boiling; and about $ mineral matter, which consists 
 of neutral calcic phosphate, 57 per cent. ; calcic carbonate, 7 per cent. ; magnesic phosphate, 1 to 2 
 
892 DEVELOPMENT OF THE HEART. 
 
 per cent. ; calcic fluoride, I per cent., with traces of chlorine ; and water, about 23 per cent. The 
 marrow contains fluid, fat, albumin, hypoxanthin, cholesterin and extractives. The red marrow 
 contains more iron, corresponding to its larger proportion of haemoglobin (Nasse). 
 
 [The medullary cavity of a long bone is occupied by yellow marrow, which contains about 96 
 per cent, of fat. The red marrow occurs in the ends of long bones, in the flat bones of the skull, 
 and in some short bones. It contains very little fat, and is really lymphoid in its characters, being, 
 in fact, a blood-forming tissue (p. 28).] 
 
 Growth of Bones. — Long bones grow in thickness by the deposition of new bone from the 
 periosteum, the osteoblasts becoming embedded in the osseous matrix to form the bone corpuscles. 
 Some of the fibres of the connective tissue, which are caught up, as it were, in the process, remain as 
 Sharpey's fibres, which are calcified fibres of white fibrous tissue, bolting together the peripheric 
 lamellae. [Mtiller and Schafer have shown that there are also fibres in the peripheric lamellae com- 
 parable to yellow elastic fibres; they branch, stain deeply with magenta, and are best developed in 
 the bones of birds.] 
 
 [At the same time that bone is being deposited on the surface it is being absorbed in the marrow 
 cavity by the action of the osteoclasts, so that a metallic ring placed round a bone in a young 
 animal ultimately comes to lie in the medullary cavity (Duhatnel). The growth in length takes 
 place by the continual growth and ossification of the epiphysial cartilage. The cartilage is gradu- 
 ally absorbed from below, but it proliferates at the same time, so that what is lost in one direction is 
 more than made up in the other (J. Hunter).] 
 
 When the growth of bone is at an end, the epiphysis becomes united to the diaphysis, the epi- 
 physial cartilage itself becoming ossified. It is not definitely proved whether there is an interstitial 
 expansion or growth of the true osseous substance itself, as maintained by Wolff (<j 244, 9). 
 
 [Howship's Lacunae. — The osteoclasts or myeloplaxes are large multinuclear giant cells, 
 which erode bone. They can be seen in great numbers lying in small depressions, corresponding 
 to them — Howship's lacunae— on the fang of a temporary tooth, when it is being absorbed. They 
 are readily seen in a microscopical section of spongy bone with the soft parts preserved.] 
 
 The form of a bone is influenced by external conditions. The bones are stronger the greater 
 the activity of the muscles acting on them. If pressure acting normally upon a bone be removed, 
 the bone develops in the direction of least resistance, and becomes thicker in that direction. Bone 
 develops more slowly on the side of the greatest external pressure, and it is curved by unilateral 
 pressure (Lesshaft). 
 
 448. DEVELOPMENT OF THE VASCULAR SYSTEM.— Heart.— [The heart appears 
 as a solid mass of cells in the splanchnopleure, at the front end of the embryo, immediately under 
 the "fore-gut." Very soon a cavity appears in this mass of cells; some of the latter float free in 
 the fluid, while the cellular wall begins to pulsate rhythmically. This hollow cellular structure 
 elongates into a tube, which very soon assumes a shape somewhat like an S (Fig. 570, i), and there 
 are indications of its being subdivided into (a) an upper aortic part with the bulbus arteriosus ; 
 (b) a middle or ventricular part; and (v) a lower venous or auricular part. The heart then 
 curves on itself in the form of a horseshoe (2), so that the venous end (A) comes to lie above and 
 slightly behind the arterial end. On the right and left side, respectively, of the venous part is a 
 blind hollow outgrowth, which forms the large auricle on each side (3, o, Oj). The flexure of the 
 body of the heart corresponding to the great curvature (2, V) is divided into two large compart- 
 ments (3), the division being indicated by a slight depression on the surface. The large truncus 
 venosus (4, V), which joins with the middle of the posterior wall of the auricular part, is composed 
 of the superior and inferior vena? cavae. This common trunk is absorbed at a later period into the 
 enlarging auricle, and thus arise the separate terminations of the superior and inferior venae cavae. 
 In man, the heart soon comes to lie in a special cavity, which in part is bounded by a portion of 
 the diaphragm (His). At the 4th-5th week the heart begins to be divided into a right and a left 
 half. Corresponding to the position of the vertical ventricular furrow, a septum grows upward 
 vertically in the interior of the heart, and divides the ventricular part into a right and left ventricle 
 (5> R| L). There is a constriction in the heart between the auricular and ventricular portions, 
 forming the canalis auricularis. It contains a communication between the auricle and both 
 ventricles, lying between an anterior and posterior projecting lip of endothelium, from which the 
 auriculo-ventricular valves are formed (F. Schmidt). The ventricular septum grows upward toward 
 the canalis auricularis, and is complete at the 8th week. Thus, the large undivided auricle commu- 
 nicates by a right and left auriculo-ventricular opening with the corresponding ventricle (5). At 
 the same time two septa (4, p a) appear in the interior of the truncus arteriosus (4, /), which 
 ultimately meet, and thus divide this tube into two tubes (5, ap), the latter forming the aorta and 
 pulmonary artery, and are disposed toward each other like the tubes in a double-barrelled gun. 
 The septum grows downward until it meets the ventricular septum (5), so that the right ventricle 
 comes to be connected with the pulmonary artery, and the left with the aorta. The division of the 
 truncus arteriosus, however, takes place only in the first part of its course. The division does not 
 take place above, so that the pulmonary artery and aorta unite in one common trunk above. This 
 communication between the pulmonary artery and the aorta is the ductus arteriosus Botalli 
 (7, B). 
 
DEVELOPMENT OF THE HEART. 
 
 893 
 
 In the auricle a septum grows from the front and behind, ending internally with a concave 
 margin. The vena cava superior £6, Cs) terminates to the right of this fold, so that its blood will 
 tend to go toward the right ventricle, in the direction of the arrow in 6, x. The cava inferior, on 
 the other hand (6, Ci), opens directly opposite the fold. On the left of its orifice, the valve of the 
 
 Fig. 570. 
 
 Development of the heart, 1, Early appearance of the heart ; — a, aortic parj, with the bulbus, b ; v , venous end. 2, 
 Horseshoe-shaped curving of the heart — a, aortic end, with the bulbus, b\ V, ventricle; A, auricular part. 3, 
 Formation of the auricular appendages, 0, o lt and the external furrow in the ventricle. 4, Commencing division 
 of the aorta,/, into two tubes, a. 5. View from the behind of the opened auricle, v, v, into the L, and R ven- 
 tricles, and between the two latter the projecting ventricular septum, while the aorta (a) and pulmonary artery 
 ( fi) open into their respective ventricles. 6. Relation of the orifices of the superior (Cs) and inferior vena cava 
 ( Ct) to the auricle (schematic view from above) — x, direction of the blood of the superior vena cava into the 
 right auricle ; y, that of the inferior cava to the left auricle ; £L, tubercle of Lower. 7. Heart of the ripe foetus — 
 K, right, L, left ventricle ; a, aorta, with the innominate, c, c, carotid, c, and left subclavian artery, s ; B, ductus 
 arteriosus ; p, pulmonary artery, with the small branches / and 2, to the lungs. 
 
 1. 
 
 The aortic arches, i. The first position of the i, 2 and 3 arches ; 2, 5, aortic arches ; ga, common aortic trunk ; ad, 
 descending aorta. Disappearance of the upper two arches, on each side — S, subclavian artery ; v, vertebral 
 artery ; aje, axillary artery. 4. Transition to the final stage — P, pulmonary artery ; A, aorta ; dB, ductus arte- 
 riosus (Botalli) ; S, right subclavian, united with the right common carotid, which divides into the internal (CV) 
 and external carotid ( Ce) ; ax, axillary ; v t vertebral artery. 
 
 foramen ovale is formed by a fold growing toward the auricular fold, so that the blood current from 
 the inferior vena cava goes only to the left, in the direction of the arrow, y : on the right of the 
 orifice of the cava, and opposite the fold, is the Eustachian valve, which, in conjunction with the 
 tubercle of Lower {IL), directs the stream from the inferior vena cava to the left into the left 
 « 
 
894 
 
 DEVELOPMENT OF THE VEINS. 
 
 auricle, through the previous foramen ovale. Compare the foetal circulation (p. 885). After 
 birth, the valve of the foramen ovale closes that aperture, while the ductus arteriosus also becomes 
 impervious, so that the blood of the pulmonary artery is forced to go through the pulmonary 
 branches proceeding to the expanding lungs. Sometimes the foramen ovale remains pervious, 
 giving rise to serious symptoms after a time, and constituting morbus ceruleus. 
 
 Arteries. — With the formation of the branchial arches and clefts, the number of aortic arches 
 on each side becomes increased to 5 (Fig. 571), which run above and below each branchial cleft, 
 in a branchial arch, and then all reunite behind in a common descending trunk (2, ad) {Rathke). 
 These blood vessels remain only in animals that breathe by gills. In man, the upper two arches 
 disappear completely (3). When the truncus arteriosus divides into the pulmonary artery and the 
 aorta (4, P, A), the lowest arch on the left side, with its origin, forms the pulmonary artery (4), 
 and it springs from the right side of the heart. Of these the left lowest arch forms the ductus 
 arteriosus (dB), and from the commencement of the latter proceed the pulmonary branches of 
 the pulmonary artery. Of the remaining arches which are united with the aorta, the left middle 
 one (i.e., the fourth left) forms the permanent aortic arch into which the ductus arteriosus opens, 
 while the right one (fourth) forms the subclavian artery : the third arch forms on each side the 
 origin of the carotids (Ci, Ce). The arteries of the first and second circulations have been referred 
 to already (p. 879). When the umbilical vesicle, with its primary circulation, diminishes, only 
 
 I, First appearance of the veins of the embryo. II, Their transformations to form the final arrangement. 
 
 one omphalo-mesenteric artery is present, which gives a branch to the intestine. At a later period 
 the omphalo-mesenteric arteries atrophy, while the artery to the intestine — the superior mesenteric 
 — becomes the largest of all, it being originally derived from one of the omphalo-mesenteric 
 arteries. 
 
 Veins of the Body. — The veins first formed in the body of the embryo itself are the two 
 cardinal veins ; on each side an anterior (Fig. 572, I, c s), and a posterior (ci — Rathke), which 
 proceed toward the heart and unite on each side to form a large trunk, the duct of Cuvier (DO, 
 which passes into the venous part of the heart. The anterior cardinal veins give off the subclavian 
 veins (66) and the common jugular veins,. which divide into the external (I*) and internal (JY) 
 jugular veins. In addition, there is a transverse anastomosing branch passing obliquely from the 
 left (where it divides) to the right, which joins their trunk lower down. In the final arrangement 
 (II), this anastomosis (As) becomes very large to form the /eft innominate vein, while with the 
 growth of the arms the subclavian veins increase (66) ; and lastly, the calibre of the jugular vein 
 changes, the internal jugular (]i) becoming very large, and the external jugular (le) smaller. In 
 some animals, e.g., the dog and rabbit, the large embryonic size is retained. The part of the left 
 superior cardinal vein, from the anastomosis downward to the left duct of Cuvier, disappears. 
 The posterior cardinal veins divide in the pelvis into the hypogastric (I, h) and external iliac (/"/)• 
 The inferior cava at first is very small (I, Vc), divides at the entrance of the pelvis, and on each 
 side goes into the point of division of the cardinal veins. There is also a transverse ascending 
 
FORMATION OF THE INTESTINAL CANAL. 
 
 895 
 
 anastomosis between the right and left cardinal veins. For the final arrangement, the cava inferior 
 (II, Ci) dilates, and with it the hypogastric and external iliac vein on each side. The right car- 
 dinal vein remains very small ( Vena azygos, Az), and also the lower part from the left one to the 
 transverse anastomosis. The latter itself also remains very small ( Vena hemiazygos, He). On the 
 other hand, the upper part above the anastomosis to the duct of Cuvier disappears. Lastly, the 
 common large venous trunk is so absorbed into the wall of the auricle (V) that both vense cavse 
 have each a separate orifice (p. 892). The embryonic condition of the veins persists in fishes. 
 
 Veins of the First and Second Circulation, and Formation of the Portal System. — The 
 two omphalo-'mesenteric veins (om, om 1 ) open into the posterior or venous end of the tubular heart 
 (Fig. 573, 1, H). The right vein, however, disappears very soon. As soon as the allantois is 
 formed, the two umbilical veins join the truncus venosus (1, u a t ). At first, the omphalo-mesen- 
 teric veins are larger than the umbilical veins ; at a later period this is reversed, and the right 
 umbilical vein disappears. As soon as veins are formed within the body proper of the embryo, the 
 inferior cava also opens into the truncus venosus (2 Ci). Gradually, the umbilical vein (2, u t ) 
 becomes the chief trunk, while the small omphalo-mesenteric (2, om x ) carries little blood. 
 
 Portal System. — The umbilical and omphalo-mesenteric veins pass in part directly under the 
 liver to reach the heart. They send branches — carrying arterial blood^to the liver, and the latter 
 grows round these vessels. These branches are the venae advehentes (2 and 3, a). The blood 
 circulating through the liver from the venae advehentes is returned by other veins, the venae reve- 
 hentes (2 and 3, r), which reunite at the blunt margin of the liver with the chief trunk of the 
 umbilical vein. The umbilical vein (3, «j) and the omphalo-mesenteric vein (3, om^) anastomose 
 in the liver. When the intestine develops (3, II), the mesenteric vein (m) opens into the omphalo- 
 
 FlG. 573. 
 
 om 
 
 Development of the veins and portal system. H, heart; R L, right and left side of the body ; om, right omphalo- 
 mesenteric vein : tfw/i, left, «, right umbilical vein; K^left; Ci, vena cava inferior; a, vehx advehentes; r, 
 vena; revehentes ; D, intestine ; m, mesenteric vein ; 4, /, splenic vein; 2, /, liver. 
 
 mesenteric vein, and the splenic vein as well (4, I), when the spleen is formed. When the 
 omphalo-mesenteric vein (4, om^) at a later period disappears, the vein from the intestine now 
 becomes the common trunk of the previously united vessels. It unites in the liver with the umbili- 
 cal vein to form the trunk of the vena portse. When, after birth, the umbilical vein disappears 
 (4, u-i), the mesenteric alone remains as the portal vein. As the ductus venosus is obliterated, 
 the portal vein- must send its blood through the liver, and thus the portal circulation is completed. 
 
 449. FORMATION OF THE INTESTINAL CANAL.— The primitive intestine, or 
 gut, consists of a straight tube proceeding from the head to the tail. The vitelline duct is inserted 
 at that point, which at a later period corresponds to the lower part of the ileum. At the 4th week 
 the tube makes a slight bend toward the umbilicus (Fig. 574, I). As already mentioned, the 
 vitelline duct is obliterated, remaining only for a time as a thread attached to the intestine, being 
 still visible at the 3d month. Sometimes it remains as a short blind tube communicating with the 
 intestine. Thus is the so-called " true intestinal diverticulum ,■" occasionally a cord — the obliter- 
 ated omphalo mesenteric vessels— passes from it to the umbilicus. In very rare cases the duct may 
 remain open as far as the umbilicus, forming a congenital fistula of the ileum, or it may give rise to 
 cystic formations (M. Roth). In a human foetus at the 4th week,.His distinguished the cavity of 
 the mouth, pharynx, oesophagus, stomach, duodenum, mesenterial intestine, and the hind-gut, with 
 the cloaca. The intestine then forms the first coil (Fig. 574, II) by rotating on itself at the intes- 
 tinal umbilicus, so that the lower part of the intestine lying next the knee-like bend comes to lie 
 above, while the upper part lies below. From the lower part of this loop the coils of the small 
 intestine (III, t), which gradually grows longer. From the upper limb of the loop, which also 
 
896 
 
 SALIVARY GLANDS, LUNGS. 
 
 elongates, the large intestine is formed; first the descending colon, then by elongation the trans- 
 verse colon, and lastly the ascending colon. 
 
 Glands. — By diverticula, or protrusions from the intestine, the various glands are formed. The 
 cells of the hypoblast proliferate and take part in the process as they form the secretory cells of the 
 
 Fig. 575. 
 
 Fig. 574. — Development of the intestine, v, stomach ; o, insertion of the vitelline duct ; t, small intestine ; c, colon ; 
 r, rectum. Fig. 575. — Formation of the lungs. A, Diverticula of the lungs as double sacks — k, mesoblastic layen; 
 I, hypoblastic layer; m, stomach ; j, oesophagus. B, Further branching of the lungs — t, trachea; b t e, bronchi ; 
 f, projecting vesicles. 
 
 glands, while the mesoblastic part of the splanchnopleure forms the membranes of the glands, giv- 
 ing them their form. The diverticula are as follows : — 
 
 1. The salivary glands, which grow out from the oral cavity at first as simple solid buds, but 
 afterward become hollow and branched. [The salivary glands are developed from the epiblast lin- 
 ing the mouth (stomodceum).] 
 
 2. The lungs, which arise as two separate hollow buds (Fig. 575, A, 1), and ultimately have 
 only one common duct, are protrusions from the oesophagus. The upper part of the united tracheal 
 
 Fig. 576. 
 
 m 
 
 Formation of the omentum. I and 11.— hg, gastro-hepatic ligament; tn, great, «, lesser curvature of the stomach; 
 j, posterior, and * anterior fold or plate of the omentum ; mc, mesocolon ; c, colon. III. — L, Liver; t, small in- 
 testine; b, mesentery ; p, pancreas; ^duodenum; r, rectum; N, great omentum. 
 
 tube forms the larynx. The epiglottis and the thyroid cartilage originate from the part which forms 
 the tongue (Gaughofner). The two hollow spheres grow and ramify like branched tubular glands 
 with hollow processes (B,/). In the first period of development there is no essential difference 
 between the epithelium of the bronchi and that of the primitive air vesicles (Stieda). The spleen 
 
DEVELOPMENT OF THE URINARY APPARATUS. 
 
 897 
 
 and suprarenal capsules, however, are not developed in this way. The former arises in a fold of 
 the mesogastrium (His) at the second month ; the latter are originally larger than the kidneys. 
 
 3. The pancreas arises in the same way as the salivary glands, but is not visible at the fourth 
 week (His). 
 
 4. The liver begins very early, and appears as a diverticulum, with two hollow primitive hepatic 
 ducts, which branch and form bile ducts. At their periphery they penetrate between the solid 
 masses of cells — the liver cells — which are derived from the hypoblast. At the second month the 
 liver is a large organ, and secretes at the third month (J 182). 
 
 5. In birds two small blind sacks are formed from the hind-gut. 
 
 6. The fcetal respiratory organ, the allantois, is treated of specially (§ 444). 
 
 Peritoneum and Mesentery. — The inner surface of the coelom, or body cavity, the surface of 
 the intestine, and its mesentery are covered by a serous coat — the peritoneum. At first the simple 
 intestine is contained in a fold, or duplicature of the peritoneum ; on the stomach, which is merely 
 at first a spindle-shaped dilatation of the tube placed vertically, it is called mesogastrium. After- 
 ward, the stomach turns on its side, so that the left surface is directed forward and the right back- 
 ward. Thus, the insertion of the mesogastrium, which originally was directed backward (to the 
 vertebral column), is directed to the left ; the line of insertion forming the region of the great cur- 
 vature, which becomes still more curved. From the great curvature the mesogastrium becomes 
 elongated like a pouch (Fig. 576, I and II, s, i), constituting the omental sack, which extends so far 
 
 Development of the internal generative organs. I, Undifferential condition — D, reproductive gland, lying on the 
 tubules ot the Wolffian body ; W, Wolffian duct ; M, Miillerian duct ; S, uro-genital sinus. II, Transformations 
 in the female — F, fimbria, with the hydatid, A 1 ; T, Fallopian tube ; U, uterus ; S, uro-genital sinus ; O, ovary ; 
 P, parovarium. Ill, Transformations in the male — H, testis; E, epididymis, with the hydatid, k; a y vas aber- 
 rans ; V, vas deferens; S, uro-genital sinus; u, male uterus; 4, .-/, hind-gut ; a, allantois; u, urachus ; K, 
 cloaca; 5, M, rectum; m, perineum ; b, position of the bladder ; S, uro-genital sinus. 
 
 downward as to pass over the transverse colon and the loops of the small intestine (III, N). As 
 the mesogastrium originally consists of two plates, of course the omentum must consist of four 
 plates. At the fourth month the posterior surface of the omental sack unites with the surface of the 
 transverse colon {Jok. Milller). 
 
 450. DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS. 
 
 Urinary Apparatus. — The first indication of this apparatus occurs in the chick at the second 
 
 day, and in the rabbit at the ninth, as the ducts of the primitive kidneys or Wolffian ducts (Fig. 
 577> l> W), which are formed from some cells mapped off from the lateral plate above and to the 
 side of the protovertebrse, and extending from the fifth to the last vertebra. The ducts are solid at 
 first, but soon become hollow, and from their cavities there extend laterally a series of small tubes, 
 which in the chick communicate freely with the peritoneal cavity (Kolliker). Into one end of each 
 of these tubes grows a tuft of blood vessels forming a structure resembling the glomeruli of the 
 kidney. The tubes elongate, form convolutions, and increase in number. The upper end of the 
 Wolffian duct is closed at first, its lower end, which lies in a projecting fold — the plica urogenitalis 
 of Waldeyer — in the peritoneal cavity, opens into the uro-genital sinus. Close above the orifice of 
 the Wolffian duct appears the ureter as the duct of the kidney. The duct elongates, and branches 
 at its upper end. Each canal at its end is like a stalked caoutchouc sack {Toldt), and into it there 
 grows the already formed glomerules. The duct of the kidney opens independently into the uro- 
 genital sinus, and forms the ureter. The part where the branching of the duct stops forms the 
 
 57 
 
898 DEVELOPMENT OF THE OVARY AND TESTICLE. 
 
 pelvis of the kidney, and the branches themselves the renal tubules. Toldt found Malpighian cor- 
 puscles in the human kidney at the second month, and Henle's loops at the fourth. The first ap- 
 pearance of the urinary bladder is at the fourth week (His), and is more distinct at the second 
 month, as the dilated first part of the allantois (Fig. 577, 4, a). The upper part of the allantois 
 remains as the obliterated urachus, in the middle vesical ligament. 
 
 Internal Reproductive Organs. — In front of and internal to the Wolffian bodies, there arises 
 in the mesoblast the elongated reproductive gland or mass of germ epithelium (Fig. 577, I, D), 
 which in both sexes is originally alike. In addition, there is formed a canal or duct parallel to the 
 Wolffian duct (W), which also opens into the urogenital sinus ; this is Miiller's duct (M). The 
 elevation of the future reproductive gland is covered originally by germ epithelium ( Waldeyer) 
 The upper end of the Miillerian duct opens free into the abdominal cavity, while the lower ends of 
 both ducts unite for a distance. Some of the germinal cells covering the surface of the future 
 ovary enlarge to form ova, and sink into the stroma to form ova embedded in their Graafian follicles 
 (§ 433). In the female, the Miillerian ducts form the Fallopian tube (II, T), and the lower united 
 ends the uterus. 
 
 In the male the germ epithelum is not so tall. According to Waldeyer, there are two kinds of 
 tubes in the Wolffian bodies and some of these penetrate the position of the reproductive gland. 
 These tubes, which are connected with the Wolffian ducts, become the seminiferous tubules [v. 
 Wittich), and the Wolffian duct itself becomes the vas deferens, with the vesiculse seminales. 
 According to some other observers, however, tubes which become the seminiferous tubules, are de- 
 veloped within the reproductive gland itself, and these tubes lined with their germ epithelium ulti- 
 mately form a connection with the Wolffian ducts. 
 
 The Miillerian ducts, which are really the ducts of the reproductive glands, disappear in man, 
 all except the lowest part, which becomes the male uterus or vtsicula prostatica (III, «) — the homo- 
 logue of the uterus. The upper tubules of the Wolffian body unite at the 3d month with the 
 reproductive gland (which has now become the body of the testis), and become the coni vasculosi 
 of the epididymis, which are lined by ciliated epithelium (E); the remainder of the Wolffian body 
 disappears. Some detached tubules form the vasa aberrantia (a) of the testicle [Kobelt). The 
 hydatid of Morgagni (h), at the head of the epididymis, according to Luschka and others, is a part 
 of the epididymis — Fleischl regards it as the rudiment of the male ovary. The organ of Giraldes 
 is part of the Wolffian body. The Wolffian duct itself becomes the vas deferens (V) from which 
 the vesiculse seminales are developed. The two Wolffian and two Miillerian ducts, as they enter 
 the pelvis, unite to form a common cord — the genital cord. 
 
 In the female the tubes of the Wolffian bodies disappear, all except a few tubules, lined with 
 ciliated epithelium, constituting the parovarium, or organ of Rosemiiller (Fig. 555) and a part 
 analogous to the organ of Giraldes in the broad ligament of the uterus ( Waldeyer) (Fig. 577, P). 
 The same is the case with the Wolffian ducts. In some animals (ruminants, pig, cat, and fox) they 
 remain permanently as the ducts of Gaertner. 
 
 The Miillerian duct is frayed out at its upper end to form the fimbriae of the Fallopian tube, and 
 it is often provided with a hydatid (A 1 ). That part of the uro-genital sinus into which the four 
 ducts open grows above into a hollow sphere, which forms the vagina (Jiathke). According to 
 Thiersch and Leuckart, however, the two Miillerian ducts unite at their lower ends to form the 
 united uterus (U) and vagina, while their free upper ends form the Fallopian, tubes (T). The 
 Miillerian ducts at first open into the posterior part of the urinary bladder below the ureters (uro- 
 genital sinus, S), while ultimately this part of the bladder becomes so elongated posteriorly that the 
 vagina (the united Miillerian ducts) and the urethra are united below and deeply within the vesti- 
 bule of the vagina. At the 3d to the 4th month, the uterus and vagina are not separate from each 
 other, but at ihe 5th to 6th month the uterus is defined from the vagina. 
 
 The testicles lie originally in the lumbar region of the abdominal cavity (Fig. 578, V I), and 
 are carried by a fold of the peritoneum — the mesorchium (m). From the hilum of the testicle a 
 cord, the gubernaculum testis, runs through the inguinal canal into the base of the scrotum. 
 At the same time a septum-like process is developed independently from the peritoneum to 
 the base of Ihe scrotum {p. v). The testicle passes through the inguinal canal into the scrotum, 
 but the mechanism and cause of the descent are not accurately ascertained. — [Descent of 
 testis, \ 446.] 
 
 The ovaries also descend somewhat. The round ligament of the uterus corresponds to the 
 gubernaculum testis. A process of the peritoneum passes in the female into the inguinal canal as 
 Nuck's canal. It is rare to find the ovaries descending into the labia majora. 
 
 [The origin of the urinary and generative organs is undoubtedly associated with the development 
 of the Wolffian bodies. The researches of Semper and Balfour on elasmobranch fishes show that 
 the process is a very complex one. There is a mass of cells on each side of the vertebral column, 
 which is divided into three parts, the first called the pronephros, or head kidney of Balfour and 
 Sedgwick, the middle one, the mesonephros or Wolffian body, and the posterior one or meta- 
 nephros, which is formed after the other two, gives origin to the permanent kidney in the amniota. 
 The Miillerian duct is connected with the pronephros, the Wolffian duct with the mesonephros, and 
 the ureter to the metanephros.] 
 
 [The following table, modified from Quain, shows the destiny of these structures : — 
 
DEVELOPMENT OF THE EXTERNAL GENITALS. 
 
 899 
 
 Female. 
 Fallopian tubes. 
 Hydatid. 
 Uterus and vagina. 
 
 Mullerian Ducts (Ducts of the Pronephros). 
 
 Male. 
 Hydatid of Morgagni. 
 Male uterus. 
 
 Wolffian Bodies (Mesonephros). 
 
 Vasa efferentia, Coni vasculosi. 
 Organ of Giraldes, Vasa aberrantia. 
 Gubernaculum testis. 
 Wolffian Ducts. 
 
 Convoluted tube of epididymis. 
 Vas deferens and vesiculse seminales. 
 Metanephros. 
 
 Ureter.] 
 
 The external genitals are at first not distinguishable in the two sexes (Fig. 578, I). At the 4th 
 week there is merely a hole at the posterior extremity of the trunk, representing both the anus and 
 the opening of the urachus, and forming a cloaca (Fig. 577, 4, K). In front of this an elevation — 
 the genital eminence — appears about the 6th week, and on each side of the orifice a large cutane- 
 ous elevation (II, w). At the end of the 2d month there is a groove on the under surface of the 
 genital eminence, leading back to the cloaca, and with distinct walls bounding it (II, r). At the 
 
 Parovarium. 
 
 Paroophoron. 
 
 Round ligament of the uterus. 
 
 Chief tube of parovarium. 
 Ducts of Gaertner. 
 
 Kidney. 
 
 n. 
 
 VI. 
 
 Development of the external genitals. / and 77, — Genital eminence ; r, genital groove ; s, coccyx ; w, cutaneous ele- 
 vations. IV— P, Penis: R, raphe penis; S, scrotum. 777 — c, clitoris; /.labia minora; L, labia majora; a, 
 anus. V and VI— Descent of the testicle ; t, testis ; m, mesorchium ; p v, processus vaginalis of the perito- 
 neum ; M, abdominal wall ; S, scrotum. 
 
 middle of the 3d month the cloacal opening is divided by the growth of the perineum, between the 
 urachus (now become the urinary bladder) (Fig. 578, 5, b) and the rectum (M). 
 
 In the male the genital eminence enlarges, its groove deepens from the opening of the bladder 
 onward to the apex of the elevation at the 10th week. The two edges unite to enclose the groove 
 which becomes the urethra. When this does not take place, hypospadias occurs. At the 4th 
 month the glans, and at the 6th the prepuce, are formed. The large cutaneous folds meet in the 
 middle line or raphe to form the scrotum. 
 
 In the female the undifferentiated condition remains to a certain extent permanent. The small 
 genital eminence remains as # the clitoris, the margins of its furrow become the nympha, the cutane- 
 ous elevations remain separate to form the labia majora. The urogenital sinus remains short as the 
 vestibule of the vagina, while in man, by the closing of the genital groove, it has a long additional 
 tube, the urethra. [The following illustrations, after Schrceder, show the changes of the external 
 organs of generation in the female. In the early period (6th week) the hind-gut (Fig. 579, R,) al- 
 lantois (All), and the Mullerian ducts (M) communicate, but not with the exterior. About the 10th 
 week a depression or inflection of the skin takes place, genital cleft, until it meets the hind-gut and 
 allantois, whereby the cloaca (Fig. 580, CI) is formed. The cloaca is then divided into an anterior 
 part, the urogenital sinus, into which the Mullerian ducts open, and a posterior part the anus. 
 There is a downward growth of the tissue between the hind-gut and the allantois to form the peri- 
 neum (Fig. 581). The uro-genital sinus then contracts at its upper part to form the short urethra, 
 its lower part remaining as the vestibule (Fig. 582, Sv), while the vagina has been formed by the 
 union of the lower parts of the two Mullerian ducts. The bladder (B) is the expanded lower end. 
 of the stalk of the allantois.] 
 
 The causes of the difference of sex are by no means well known. From a statistical analysis 
 of 80,000 cases, the influence of the age of the parents has been shown by Hofacker and Sadler. 
 If the husband is younger than the wife, there are as many boys as girls; if both are of the same 
 
900 
 
 FORMATION OF THE CENTRAL NERVOUS SYSTEM. 
 
 age, there are 1029 boys to 1000 girls; if the husband is older, 1057 boys to 1000 girls. In insects, 
 food has a most important influence. Ffluger's investigations on frogs show that all external condi- 
 tions during development are without effect on the determination of the sex, so that the latter would 
 seem to be determined before impregnation. 
 
 451. FORMATION OF THE CENTRAL NERVOUS SYSTEM.— Fore brain.— At 
 
 each side of the fore brain, or anterior cerebral vesicle, which is covered externally by epiblast and 
 internally by the ependyma, there grows out a large stalked hollow vesicle, the rudiment of the cere- 
 bral hemispheres. The relatively wide opening in the stalk, or communication, ultimately be- 
 comes very small, and is the foramen of Monro. The middle part between the two cerebral vesi- 
 cles remains small, and is the 'tween or inter-brain with the 3d ventricle in its interior. It elon- 
 gates at the second month toward the base of the brain as a runnel shaped projection, to form the 
 tuber cinereum with the infundibulum. The thalami optici, projecting and enlarging from the sides 
 of the 3d ventricle, narrow the foramen of Monro to a semilunar slit. At the base of the brain are 
 formed, in the 2d month, the corpora albicantia, at the 3d the chiasma; while within the 3d ventri- 
 cle, the commissures are formed. The hypophysis, belonging to the mid-brain, is a diverticulum of 
 the nasal mucous membrane, extending through the base of the skull toward the hollow infundibulum, 
 which grows to meet it. The choroid plexus, which grows into the ventricles of the hemispheres 
 through the foramen of Monro, is a vascular development of the tependyma. At the 4th month, the 
 conarium (pineal gland) is formed, and at this time the corpora quadrigemina cover the hemi- 
 spheres. The corpora striata begin to be developed in the cerebral (lateral) ventricle at the 2d 
 month, while the cornu ammonis is formed at the 4th month. At the 3d month the Sylvian fissure 
 is formed, and the basis of the island of Reil. The permanent cerebral convolutions are formed 
 from the 7th month onward. 
 
 Fig. 579. 
 
 Fig. 580. 
 
 Fig. 581. 
 
 Fig. 582. 
 
 Fig. 579 — R . rectum continuous with the allantois (All— hladder) • M, duct of Miiller (vagina) ■ A depression ofskin 
 below genital eminence, growing inward toiorm the vulva. Fig. 580.— The depression has become continuous 
 with the rectum and allantois, to form the cloaca (C L). Fig. 581.— The cloaca is becoming divided into uro- 
 genital sinus (Su) and anus by the downward growth of the perineal septum. The ducts of Miiller are united 
 to form the vagina (V). Fig. 582.— Perineum completely formed. 
 
 The mid-brain, or middle cerebral vesicle, is gradually covered over by the backward growth of 
 the hemispheres ; its cavity forms the aqueduct of Sylvius. Depressions appear on the surface of ^ 
 the vesicle to divide it into four, the corpora quadrigemina, the longitudinal depression being W 
 formed at the 3d, and the transverse one at the 7th month. The cerebral peduncle is formed by a 
 thickening in the base of this vesicle. 
 
 In the hind-brain are formed the cerebellar hemispheres, which grow backward to meet in the 
 middle line. The vermes is formed at the 7th month. The cerebellum covers in the part of the 
 medullary tube lying below it, and which is not closed, as far as the calamus. The pons arises in 
 the floor of the hind-brain at the 3d month. 
 
 The spindle-shaped narrow after-brain forms the medulla oblongata, with the opening of the 
 medullary tube in its upper part. 
 
 [The following table, from Quain, shows the destiny of each cerebral vesicle : 
 
 I. Prosencephalen .... f Cerebral hemispheres, corpora striata, 
 (fore-brain.) 
 
 Anterior Primary 
 Vesicle . 
 
 I 2 - 
 I 
 
 II. 
 
 III. 
 
 Middle Primary 
 Vesicle . . . 
 
 Posterior Primary 
 Vesicle .... 
 
 Thalamencephalon . . 
 (inter or 'tween brain.) 
 
 Mesencephalon . . . . , 
 (mid-brain.) 
 
 corpus callosum, fornix lateral ven 
 
 . tricles, olfactory bulb. 
 
 ' Thalami optici, pineal gland, pituitary 
 
 body, crura cerebri, aqueduct of 
 
 Sylvius, optic nerve. 
 
 ' Corpora quadrigemina, crura cerebri, 
 
 aqueduct of Sylvius, optic nerve 
 
 (secondarily). 
 
 Epencephalon j Cerebellum, pons, anterior part of the 
 
 (hind-brain.) \ fourth ventricle. 
 
 5. Metencephalon j Medulla oblongata, fourth ventricle, 
 
 [ (after-brain.) \ auditory nerve. 
 
 [Spinal Cord.— The spinal cord is developed from the medullary tube behind the medulla 
 oblongata, first the gray matter around the canal, while the white matter is added afterward outside 
 this. The ganglionic cells increase by division in amphibians [Lominsky). At first the spinal cord 
 reaches the coccyx. The first muscles are formed in the back at the 2d month ; at the 4th month 
 
DEVELOPMENT OF THE SENSE ORGANS. 
 
 901 
 
 they are red. The spinal ganglia are formed from a special strip of cells, and they are seen at 
 the 4th week, and so are the anterior spinal roots and some of the trunks of the spinal nerves, 
 while the posterior roots are still absent. The peripheral nerves grow out from the ganglia of the 
 spinal cord (first the motor and afterward the sensory nerves), and penetrate into the other parts of 
 the body (His). At first they are devoid of myelin. 
 
 45». DEVELOPMENT OF THE SENSE ORGANS Eye.— The primary optic 
 
 vesicle grows out from the fore-brain toward the outer covering of the head or epiblast, and soon 
 becomes folded in on itself (4th week), so that the stalked optic vesicle is shaped like an egg-cup 
 (Fig. 583, 1). The cavity in the anterior of this cup is called the secondary optic vesicle. The 
 inflected part becomes the retina (IV, r), while the posterior part becomes the choroidal epithelium 
 (IV, p). The stalk becomes the optic nerve. At the under surface of the depression there is a 
 slit — the choroidal.fissure — which permits some of the mesoblast to gain access to the interior of 
 the eye. This slit forms the coloboma (II) ; it is prolonged backward on the stalk, and contains 
 the central artery of the retina. The margins of the coloboma afterward unite completely with 
 each other, but in some rare conditions this does not take place, in which case we have to deal 
 with a coloboma of the choroid or retina, as the case may be. In the bird, the embryonic colo- 
 boma slit does not close up, but a vascular process of the mesoblast dips into it, and passes into the 
 eye to form the pecten (p. 813) (Lieberkuhn). The same is the case in fishes where there is a 
 large vascular process of the meso- and epiblast forming the processus falciformis (p. 813). 
 
 Fig. 583. 
 
 /elopment of the eye. 1. — Inflexion of the sack of the lens (LJ into the primary optic vesicle (P) — e, epidermis ; 
 m, mesoblast. II. — The inflexion seen from below — «, optic nerve ; *, the outer ; t, the inner layer of the 
 inflected vesicle : L, lens. III. — Longitudinal section of II. IV. — Further development — e, corneal epithelium ; 
 c, cornea ; m, membrana capsulo-pupiliaris : L, lens : a, central artery of the retina ; s, sclerotic ; c k, choroid ; 
 
 p, pigment layer of the retina ; r, retina. V. — Persistent remains of the pupillary membrane. 
 
 The depression or inflection of the optic vesicle is due to the down growth into it of a thickening 
 of the epiblast (I, L). It is hollow, and as it grows inward ultimately becomes spherical and 
 separated from the epiblast to form the crystalline lens, so that the lens is epiblastic in its origin, 
 while the capsule of the lens is a cuticular structure formed from epiblast. That part of the epi- 
 blast which covers the vesicle in front of the lens ultimately becomes the stratified epithelium of the 
 cornea. The cornea is formed at the 6th week. The substance of the choroid, sclerotic and 
 cornea is formed around the position of the eye from the mesoblast (m). The capsule of the 
 lens is at first completely surrounded by a vascular membrane — the membrana capsulo-pupil- 
 iaris. Afterward the lens passes more posteriorly into the eye — the anterior part of the capsulo- 
 pupillary membrane, however, remains in the anterior part of the eye, while toward it grows the 
 margin of the iris (7th week), so that the pupil is closed by this part of the vascular capsule (mem- 
 brana pupillaris). The blood vessels of the iris are continuous with those of the pupillary mem- 
 brane ; those of the posterior capsule of the lens give off the hyaloid artery, a continuation of the 
 central artery of the retina ; its veins pass into those of the iris and choroid. The vitreous humor 
 at the 4th week is represented by a cellular mass between the lens and the retina (Kolliker). The 
 pupillary membrane disappears at the 7th month. It may remain throughout life (V). 
 
 Organ of Smell. — On the under surface and lateral limit of the fore-brain, the epiblast forms a 
 groove or pit with thickened epithelium, which forms a depression toward the brain, but always 
 remains as a pit or depression ; this is the olfactory or nasal pit, to which the olfactory nerve after- 
 ward sends its branches. 
 
 Organ of Hearing.— On both sides of the after- brain there is a depression or pit formed in the 
 epiblast, which gradually extends deeper toward the brain — this is the labyrinth pit. The pit is 
 ultimately completely cut off from the epiblast, just like the lens, and is now called the vesicle of 
 the labyrinth. It represents the utricle, from which, at the 2d month, the semicircular canals and 
 the cochlea are developed. The union with the brain occurs later along with the development of 
 the auditory nerve. The first visceral cleft remains as an irregular passage from the Eustachian 
 tube to the external auditory meatus. The outer ear appears at the 7th week. 
 
902 INFLUENCE OF NERVES ON THE UTERUS. 
 
 t 
 
 453. BIRTH. — With the growth of the ovum, the uterus becomes more dis- 
 tended, its walls more muscular and more vascular, although the uterine walls are 
 not thicker at the end of pregnancy. Toward the end of gestation the cervical 
 canal is intact until labor begins, or at any rate it is only slightly opened up at its 
 upper parts. After a period of 280 days of gestation "labor" begins, whereby 
 the contents of the uterus are discharged. The labor pains occur rhythmically 
 and periodically, being separated from each other by intervals free from pain. 
 Each pain begins gradually, reaches a maximum, and then slowly declines. With 
 each pain the heat of the uterus increases (§ 302), while the heart beat of the 
 fetus becomes slower and feebler, which is due to stimulation of the vagus in the 
 medulla oblongata (§ 369, 3). 
 
 [At the full time the membranes and placenta line the uterus. The membranes 
 consist, from within outward, of amnion, chorion, decidua reflexa, and decidua 
 vera. The fundi of the uterine glands persist in the deep part of the decidua 
 vera and thus form a spongy layer, the part above this being the compact layer 
 in the deep part of the placenta, e. g., near the uterine wall, we have also the 
 fundi of the uterine glands persisting in the decidua serotina. When the placenta 
 and membranes are expelled after birth, the line of separation takes place in 
 the part of the membranes and placenta where the fundi of the glands persist. 
 After labor is completely finished the uterus is lined by the remains of the spongy 
 layer of the decidua vera and serotina, e. g., is lined by a layer which contains 
 the fundi of the uterine glands. The new mucous membrane is regenerated by 
 the growth of the epithelium and connective tissue in this part. The mem- 
 branes expelled are made up of amnion, chorion, deciduse reflexa?, and the 
 compact layer of the decidua vera.] 
 
 [Power in Ordinary Labors. — Sometimes the ovum is expelled whole, the 
 membranes containing the liquor amnii remaining unruptured. Poppel has pointed 
 out that the force which ruptures the bag of membranes is sufficient to complete 
 delivery, so that, as Matthews Duncan remarks, the strength of the membranes 
 gives us a means of ascertaining the power of labor in the easiest class of natural 
 labors. Matthews Duncan, from experiments on the pressure required to rupture 
 the membranes, concludes that the great majority of labors are completed by a 
 propelling force not exceeding forty pounds.] 
 
 Polaillon estimates the pressure exerted by the uterus upon the fcetus at each pain to be 154 kilos.l 
 [338.8 lbs.], so that, according to this calculation, the uterus at each pain performs 8820 kilogram- * 
 melres of work ($ 301). [This estimate is certainly far too high.] 
 
 After-birth. — After the fcetus is expelled, the placenta remains behind ; but it is soon expelled 
 by the contractions of the uterus. During the contraction of the uterus to expel the placenta, a not 
 inconsiderable amount of the placental blood is forced into the child ($ 40). [It is more probable 
 that the child aspirates the blood from the foetal portion of the placenta. This can be seen in late 
 ligature of the cord. The child may thus gain two ounces of blood.] After a time the placenta, 
 the membranes, and the decidua— constituting the after-birth — are expelled. 
 
 Influence of Nerves on the Uterus. — 1. Stimulation of the hypogastric plexus causes con- 
 traction of the uterus. The fibres arise from the spinal cord, from the last dorsal, and upper three 
 or four lumbar nerves, run into the sympathetic, and then reach the hypogastric plexus (Franken- 
 hauser). 2. Stimulation of the nervi erigentes, which are derived from the sacral plexus, causes 
 movement [v. Basch and Hofmann). 3. Stimulation of the lumbar and sacral parts of the cord 
 causes powerful movements {Spiegelberg, Schijf). There is a. centre for the act of parturition in 
 the lumbar region of the cord ($ 362, 6). The uterus, like the intestine, probably contains inde- 
 pendent or parenchymatous nerve centres {/Corner), which can be excited by suspension of the 
 respiration, and by anaemia (by compressing the aorta, or rapid hemorrhage). Decrease of the 
 bodily temperature diminishes the movement, while an increase of the temperature increases it, 
 which, however, ceases during high fever (Fromme). The experiments made by Rein upon bitches 
 show that, if all the nerves going to the uterus be divided, practically all the functions connected 
 with conception, pregnancy, and parturition can take place, even although the uterus is separated 
 from all its cerebro-spinal connections. Hence we must look to the presence of some automatic 
 ganglia in the uterus itself. According to Dembo, there is a centre in the anterior wall of the 
 vagina of the rabbit. According to jastreboff, the vagina of the rabbit contracts rhythmically. 
 Sclerotic acid greatly excites the uterine contractions (v. Swiecicki). 4. The uterus contracts re- 
 flexly on stimulating the central end of the scatic nerve (v. Basch and Hofmann), the central end 
 of branchial plexus [Schlesinger), and the nipple {Soanzoni). 5. The uterus is supplied by vaso- 
 
COMPARATIVE HISTORICAL. 903 
 
 motor nerves (hypogastric plexus), which come from the splanchnic ; and also by vaso-dilator fibres, 
 the latter through the nervi erigentes. The vasomotor nerves are affected reflexly by stimulation of 
 the sciatic nerve {v. Basch and Hofmann). 
 
 Lochia. — After birth, the whole mucous membrane (decidua) is shed ; its inner 
 surface, therefore, represents a large wounded surface, on which a new mucous 
 membrane is developed. The discharge given off after birth constitutes the 
 lochia. 
 
 Involution of the Uterus. — After birth the thick muscular mass decreases 
 in size, some of its fibres undergoing fatty degeneration. Within the lumen of 
 the blood vessels of the uterus itself, there begins in the interna of these vessels a 
 proliferation of- the connective-tissue elements, whereby within a few months the 
 blood vessels so affected become completely occluded. The smooth muscular 
 fibres of the middle coat of the arteries undergo fatty degeneration. The rela- 
 tively large vascular spaces in the region of the placenta are filled by blood clots, 
 which are ultimately traversed by outgrowths of the connective tissue of the vas- 
 cular walls. 
 
 Milk Fever. — After birth there is a peculiar action on the vasomotor system, 
 constituting milk fever, while at the 2d to 3d day there is a more copious supply 
 of blood to the mammary gland for the secretion of milk (§ 231). [After birth 
 the pulse becomes slow and remains so in a normal puerperum. The so-called 
 milk fever is not found in cases where strict cleanliness is observed during the 
 labor and puerperum.] The cause of the first respiration in the child is referred 
 to at p. 692. 
 
 454. COMPARATIVE— HISTORICAL.— A sketch of the development of man must 
 necessarily have some reference to the general scheme of development in the Animal Kingdom. 
 The question as to how the numerous forms of. animal life at present existing on the globe have 
 arisen has been answered in several ways. It has been asserted that each species has retained its 
 characters unchanged from the beginning, so that we speak of the " constancy of species." This 
 view, developed by Linnaeus, Cuvier, Agassiz, and others, is opposed by that supported by Lamarck 
 (1809), or the doctrine of the " Unity of the Animal Kingdom," corresponding to the ancient view 
 of Empedocles, that all species of animals were derived by variations from a few fundamental 
 forms ; that at first there were only a few lower forms from' which the numerous species were devel- 
 oped — a view supported by Geoffrey St. Hilaire, and Goethe. After a long period this view was 
 restated and elucidated in the most brilliant and most fruitful manner by Charles Darwin (1859) in 
 his " Origin of Species," and other works. He attempted to show how modifications may be 
 brought about by uniform and varying conditions acting for a long time. Among created beings 
 each one struggles with its neighbor, so that there is a real "struggle for existence." Many 
 qualities, such as vigor, 'rapidity, color, reproductive activity, etc., are hereditary, so that in this way 
 by " natural selection " there may be a gradual improvement, and therewith a gradual change. 
 of the species. In addition, organisms can, within certain limits, accommodate themselves to their 
 surroundings or environment. Thus certain useful organs or parts may undergo development, 
 while inactive or useless parts may undergo retrogression, and form " rudimentary organs." 
 This process of "natural selection," causing gradual changes in the form of organisms, finds its 
 counterpart in " artificial selection," among plants and animals. Breeders of animals, for ex- 
 ample, by selecting the proper crosses, can within a relatively short time produce very material 
 alterations in the form and characters of the animals which they breed, the changes being 'more 
 pronounced than many of those that separate well-defined species. But, just as with artificial se- 
 lection, there is sometimes a sudden " reversion " to a former type, so in the development of species 
 by natural selection there is sometimes a condition of atavism. Obviously, a wide distribution of 
 one species in different climates must increase the liability to change, as very different conditions of 
 environment come into play. Thus, the migration of organisms may gradually lead to a change of 
 species. 
 
 Biological Law.— Without discussing the development of different organisms, we may refer to 
 the "fundamental biological law" of Hseckel, viz., "that the ontogeny is a short repetition of the 
 phytogeny ," [ontogeny being the history of the development of single beings, or of the individual 
 from the ovum onward, while phylogeny is the history of the development of a whole stock of 
 organisms, from the lowest forms of the series upward] (p. xxxii). When applied to man, this law 
 asserts that the individual stages in the course of the development of the human embryo, e.g., its 
 existence as a unicellular ovum, as a group of cells after complete cleavage, as a. blastodermic ves- 
 icle, as an organism without a body cavity, etc. ; that these stages of development indicate or rep- 
 resent so many animal forms, through which the human species in the course of untold ages has 
 been gradually evolved. The individual stages which the human race has passed in this process 
 of evolution are rapidly rehearsed in its embryonic development. This conception has not passed 
 
904 COMPARATIVE — HISTORICAL. 
 
 without challenge. In any case, the comparison of the human development and its indiyidua 
 organs with the corresponding perfect organs of the lower vertebrates is of great importance Jhus 
 a mammal during the development of its organs is originally possessed of the tubular heart th. 
 branchial clefts, fhe undeveloped brain, the cartilaginous chorda dorsalis and many arrangement 
 of the vascular system, etc , which are permanent throughout the life of the lowest vertebrates 
 These incomplete stages are perfected in the ascending classes of vertebrates. Still, there are man; 
 difficulties to contend with in establishing both the evolution hypothesis of Darwin and the biolog 
 ical law of Haeckel. , , 
 
 Historical.— Although the impetus to the study of the history of development has been mos 
 stimulated in recent times, the ancient philosophers held distinct but varied views on the question o 
 development. Passing over the views of Pythagoras (550 B.C.) and Anaxagoras (500 B.C.), Empe 
 docles (473 B.C.) taught that the embryo was nourished through the umbilicus; while he named th. 
 chorion and amnion. Hippocrates observed incubated eggs from day to day, noticed that th< 
 allantois protruded through the umbilicus, and observed that the chick escaped from the egg on tn< 
 20th day. He taught that a 7 months' foetus was viable, and explained the possibility of superfce 
 tation from the horns of the uterus. The writings of Aristotle (born 384 B.C.) contain many refer 
 ences to development, and many of them are already referred to in the text. He taught that th. 
 embryo receives its vascular supply through the umbilical vessels, and that the placenta sucked th. 
 blood from the vascular uterus, like the rootlets of a tree absorbing moisture. He distinguished th. 
 polycotyledonary from the diffuse placenta ; and he referred the former to animals without a com 
 plete row of teeth in both jaws. In the incubated egg of the chick, he distinguished the blooc 
 vessels of the umbilical vesicle, which carried food from the cavity of the latter, and also the allan 
 tois. He also observed that the head of the chick lay on its right leg, and that the umbilical sacl 
 was ultimately absorbed into the body. The formation of double monsters, he ascribed to th. 
 union of two germs or two embryos lying near each other. During generation, the female pro 
 duces the matter, the male the principle which gives it form and motion. There are also numeroui 
 references to reproduction in the lower animals. Erasistratus (304 B.C.) described the embryo a: 
 arising by new formations with the ovum or Epigenesis, while his contemporary, Herophilus, founc 
 that the pregnant uterus was closed. He was. aware of the glandular nature of the prostate, anc 
 named the vesiculse seminales and the epididymis. Galen (131-203 A.D.) was acquainted with th. 
 existence of the foramen ovale, and the course of the blood in the foetus through it, and througl 
 the ductus arteriosus. He was also aware of the physiological relation between the breast and thi 
 blood vessels of the uterus, and he described how the uterus contracted on pressure being appliec 
 to it. In the Talmud, it is stated that an animal with its uterus extirpated may live, that the pubei 
 separates during birth, and there is a record of a case of Caesarian section, the child beinj 
 saved. Sylvius described the value of the foramen ovale ; Vesalius (1540) the ovarian follicles 
 Eustachius (f 1570) the ductus arteriosus (Botalli) and the branches of the umbilical vein to thi 
 liver. Arantius investigated the duct which bears his name, and he asserted that the umbilical ar 
 teries do not anastomose with the maternal vessels in the placenta. In Libavius (1597) i' ' s state, 
 that the child may cry in utero. Riolan (1618) was aware of the existence of the corpus High 
 morianum testis. Pavius (1657) investigated the position of the testes in the lumbar region of thi 
 fcetus. Harvey (1633) stated? the fundamental axiom, " Omne vivum ex ovo." Fabricius al 
 Aquapendente (1600) collected the materials known for the history of the development of th 
 chick. Regner de Graaf described more carefully the follicles which bear his name, and he foun. 
 a mammalian ovum in the Fallopian tube. Swammerdam (-|- 1685) discovered metamorphosis 
 and he dissected a butterfly from the chrysalis before the Grand Duke of Tuscany. He describe! 
 the cleavage of the frog's egg. Malpighi (f 1694) gave a good description of the development o 
 the chick with illustrations. Hartsoecker (1730) asserted that the spermatozoa pass into the ovum 
 The first half of the 18th century was occupied with a discussion as to whether the ovum or th 
 sperm was the more important for the new formation (the Ovulists and Spermatists) ; and also a 
 to whether the foetus was formed or developed within the ovum (Epigenesis), or if it merely in 
 creased in growth. The question of spontaneous generation has been frequently investigated sino 
 the time of Needham in 1745. 
 
 New Epoch. — A new epoch began with Caspar Fried. Wolff (1759), who was the first t 
 teach that the embryo was formed from layers, and that the tissues were composed of smaller pari 
 (corresponding to the cells of the present period). He observed exactly the formation of the intes 
 tine. William Hunter (1775) described the membranes of the pregnant uterus. Scemmerin 
 (1799) described the formation of the external human configuration, and Oken and Kiesser that c 
 the intestines. Oken and Goethe taught that the skull was composed of vertebrae. Tiedeman 
 described the formation of the brain, and Meckel that of monsters. The basis for the study of th 
 development of an animal from the layers of the embryo, was laid by the researches of Pande 
 (1817), Carl Ernst v. Baer (1828-1834), Remak and many other observers; and Schwann was th 
 first to trace the development of all the tissues from the ovum. [Schleiden enunciated the ce 
 theory with reference to the minute structure of vegetable tissues, while Schwann applied th 
 theory to the structure of animal tissues. Among those whose names are most prominent in coi 
 nection with the evolution of this theory are Martin Barry, von Mohl, Leydig, Remak, Goodsi 
 Virchow, Beale, Max Schultze, and a host of recent observers.] 
 
INDEX. 
 
 Abdominal muscles in respira- 
 tion, 200 
 Abdominal reflex, 666 
 Abducens, 630 
 Abiogenesis, 856 
 Absolute blindness, 722 
 Absorption by fluids, 56 
 by solids, 56 
 Absorption of — 
 Carbohydrates, 328 
 Coloring matter, 329 
 Digested food, 325 
 Effusions, 344 
 Fat soaps, 329 
 Forces of, 330 
 Grape sugar, 328 
 Influence of nerves on, 331 
 Inorganic substances, 328 
 Nutrient enemata, 331 
 Organs of, 319 
 Oxygen, 217 
 Peptones, 328 
 Small particles, 330 
 Solutions, 328 
 f Sugars, 328 
 t Unchanged proteids, 329 
 f Absorption spectra, 39 
 Accelerans nerve, 693 
 
 in frog, 695 
 Accommodation of eye, 766 
 defective, 772 
 r # force of, 772 
 
 line of, 770 
 phosphene, 780 
 range of, 772 
 spot, 780 
 time for, 769 
 Accord, 828 
 Acetic acid, 309 
 Aceton, 292, 441, 452 
 Acetonemia, 292 
 Acetylene, 42 
 Achromatopsy, 795 
 Achroodextrin, 244 
 Acid albumin, 409 
 Acids, free, 413 
 Acoustic nerve, 634 
 
 tetanus, 585 
 Acquired movements, 727 
 Acrylic acid series, 413 
 Action currents, 597 
 Active insufficiency, 537 
 Addison's disease, 486, 614 
 Adelomorphous cells, 267 
 Adenoid tissue, 335 
 Adipocere, 398 
 
 Adventitia, 112 
 
 ^Egophony, 205 
 
 Aerobes, 308 
 
 /Esthesiometer, 847 
 
 /Esthesodic substance, 670 
 
 Afferent nerves, 615 
 
 After birth, 902 
 
 After images, 797 
 
 After sensation, 749 
 
 Ageusia, 843 
 
 Agoraphobia, 637 
 
 Agrammatism, 730 
 
 Agraphia, 729 
 
 Ague, 367 
 
 Air, changes in respiration, 212. 
 
 collection of, 209 
 
 composition of, 2 1 2 
 
 diffusion of, 216 
 
 expired, 213 
 
 impurities in, 225 
 
 quantity exchanged, 213 
 Air cells, 184 
 Alanin, 411 
 Albuminoids, 411 
 Albumins, 408 
 Albuminuria, 445 
 Albumoses, vegetable, 410 
 Alcohol, 385 
 Alcohols, 415 
 Alcoholic drinks, 386 
 Aleurone grains, 410 
 Alexia, 731 
 Alkali albumin, 409 
 Alkaline fermentation, 445 
 Alkaloids, 385 
 Alkophyr, 275 
 Allantoin, 417, 439 
 Allantois, 882 
 Allochiria, 853 
 Alloxan, 435 
 Almen's test, 450 
 Alternate hemiplegia, 681 
 
 paralysis, 681 
 Alternation of generations, 857 
 Amaurosis, 618 
 Amblyopia, 618 
 American crow-bar case, 704 
 Amido acids, 733 
 Amido-caproic acid, 281 
 Amines, 417 
 Aminia, 729 
 Ammoniaemia, 469 
 Amnesia, 730 
 Amnion, 881 
 Amniota, 881 
 Amniotic fluid, 881 
 905 
 
 Amoeboid movement, 31 
 Ampere's rule, 578 
 Amphiarthroses, 535 
 Amphoric breathing, 205 
 Amygdalin, 344 
 Amyloid substance, 410 
 Amylopsin, 280 
 Amylum, 416 
 Anabiosis, 856 
 Anacrotism, 130 
 Anaemia, 34, 65 
 
 metabolism in, 65 
 
 pernicious, 35 
 Anaerobes, 308 
 Anaesthesia dolorosa, 853 
 Anaesthetic leprosy, 614 
 Anaesthetics, 854 
 Anabolic, 373 
 Anakusis, 635 
 Analgesia, 672 
 Analgia, 854 
 Anamnia, 881 
 Anarthria, 729 
 Anasarca, 345 
 Anelectrotonus, 597 
 Aneurism, 137 
 Angiometer, 129 
 Angioneuroses, 700 
 Angiograph, 121 
 Anidrosis, 488 
 
 Animals, characters of, xxxvii 
 Animal foods, 390 
 
 magnetism, 708 
 Anions, 579 
 
 Anisotropous substance, 495 
 Ankle clonus, 668 
 Anode, 579 
 Anosmia, 616 
 Antagonistic muscles, 538 
 Anthracometer, 209 
 Anthracosis, 188, 226 
 Anthropocholic acid, 293 
 Anti-albumin, 274 
 Antiar, 344 
 Antihydrotics, 486 
 Antipeptone, 282 
 Antiperistalsis, 259 
 Anti-sialics, 241 
 Aortic valves, 72 
 Aperistalsis, 262 
 Apex beat, 78, 86 
 Aphakia, 757 
 Aphasia, 729, 730 
 Aphonia, 558 
 Apnoea, 687 
 Appunn's apparatus, 833 
 
906 
 
 INDEX. 
 
 Apselaphesia, 853 
 
 Aqueous humor, 758 
 
 Arachnoid mater, 743 
 
 Archiblastic cells, 878 
 
 Area opaca, 865 
 
 pellucida, 865 
 vasculosa, 879 
 
 Argyll Robertson pupil, 777 
 
 Arhythmia cordis, 128 
 
 Aristotle's experiment, 849 
 
 Aromatic acids, 415 
 
 oxyacids, 417 
 
 Arrector pili muscle, 482 
 
 Arteries, 1 1 1 
 
 development of, 894 
 emptiness of, 696 
 rhythmical contraction 
 
 of, 698 
 sounds in, 164 
 structure of, III 
 tension in, 145 
 termination in veins, 
 160 
 
 Arteriogram, 121 
 
 Arterial tension, 125 
 
 Arthrodial joints, 535 
 
 Articular cartilage, 533 
 
 Articulation nerve corpuscles, 
 
 845 
 Artificial' cold-blooded condition, 
 
 371 
 Artificial digestion, 275 
 
 gastric juice, 273 
 pancreatic juice, 283 
 Artificial respiration, 224 
 
 Marshall Hall's me- 
 thod, 224 
 Sylvester's method, 
 224 
 Artificial selection, 903 
 Asparaginic acid, 417 
 Asphyxia, 222, 688 
 
 artificial respiration in, 
 
 224 
 recovery from, 224 
 Aspirates, 558 
 Aspiration of heart, 152 
 Assimilation, 373 
 Associated movement, 803 
 Astatic needles, 579 
 Asteatosis, 489 
 Asthma nervosum, 643 
 
 dyspepticum, 644 
 Astigmatism, 774 
 
 correction of, 775 
 test for, 775 
 Atavism, 903 
 Ataxaphasia, 729 
 Ataxia, 648, 721, 729, 731 
 Ataxic tabes, 672 
 Atelectasis, 225 
 Atmospheric pressure, 229 
 
 diminution of, 229 
 increase of, 230 
 Atresia ani, 881 
 Atrophy, 539 
 
 of the face, 630 
 
 Atropin, 511 
 
 in eye, 619, 777 
 Attention, time for, 707 
 Audible tone, lowest, 830 
 Auditory after sensations, 837 
 
 area, 723 
 
 aurse, 723 
 
 centre, 723 
 
 delusions, 635 
 
 meatus, 816 
 
 nerve, 814 
 
 ossicles, 819 
 
 paths, 724 
 
 perception, 829 
 Auerbach's plexus, 262, 325 
 Auricles of heart, 68, 75, 83 
 Auscultation of heart, 93 
 
 of lungs, 195 
 Automatic excitement, 653 
 Autonomy, 708 
 Auxocardia, 104 
 Axis of vision, 787 
 
 Bacillus, 66, 307 
 
 amylobacter, 309 
 anthracis, 66 
 butyricus, 309 
 subtilis, 310 
 tubercle and others, 
 226 
 Bacterium, 66, 307, 313, 380 
 aceti, 309 
 cyanogeneum, 380 
 foetidum, 489 
 lacticum, 308, 378 
 synxanthum, 380 
 termo, 313 
 Ball and socket joints, 535 
 Bantingism, 399 
 Baraesthesiometer, 850 
 Basal ganglia, 733 
 Basedow's disease, 180, 701 
 Bases, 408 
 
 Basilar membrane, 827 
 Batteries, galvanic, 579 
 Bunsen's, 580 
 Grennet's, 581 
 Grove's, 580. 
 Lechlanche's, 581 
 Smee's, 581 
 Beats, 836 
 
 isolated, 836 
 successive, 836 
 Bed sore, 614 
 Beef tea, 383 
 Beer, 387 
 Bell's law, 646 
 
 deductions from, 647 
 Bell's paralysis, 633 
 Benzoic acid, 415 
 Bert's experiment, 606 
 Bidder's ganglion, 94 
 Bile acids, 293 
 
 composition of, 293 
 crystallized, 293 
 ducts, 286 
 
 ligature of, 288 
 
 Bile, effect of drugs on, 300 
 
 excretion of, 298 
 
 fate of, 302 
 
 functions of, 301 
 
 pigments, 295 
 
 pressure, 299 
 
 reabsorption of, 299 
 
 secretion of, 296 
 
 spectrum of, 295 
 
 test for, 294, 295 
 Biliary fistula, 298 
 Bilicyanin, 295 
 Bilifuscin, 295 
 Biliprasin, 295 
 Bilirubin, 295 
 Biliverdin, 295 
 Binocular vision, 803 
 Biological law, 903 
 Biology, xxxi 
 Birth, 902 
 Biuret reaction, 275 
 Blastoderm, 864, 874 
 Blastosphere, 874 
 Blepharospasm, 634 
 Blind spot, 785 
 Blood, 17 
 
 abnormal, 63 
 
 analysis, 45 
 
 arterial, 62 
 
 carbon dioxide in, 40 
 
 clot, 47 
 
 coagulation, 47 
 
 color, 17 
 
 coloring matter, 35 
 
 defibrinated, 47 
 
 distribution of, 167 
 
 electrical condition of, 61 1 
 
 extractives, 56 
 
 fats in, SS 
 
 fibrin in, 34, 47 
 
 lake-colored, 23 
 
 loss of, 65 ' 
 
 microscopic examination 
 18 
 
 nitrogen in, 61 
 
 odor, 18 
 
 organisms in, 66 
 
 oxygen in, 59 
 
 ozone in, 60 
 
 plasma, 46 
 
 plates, 33 
 
 portal vein, 62 
 
 quantity, 63, 160 
 
 reaction, 17 
 
 salts in, 56, 65 
 
 serum, 46 
 
 specific gravity, 18 
 
 taste, 18 
 
 temperature, 18 
 
 transfusion of, 63 
 
 variations in, 63 
 
 venous, 62 
 
 water in, 54 
 Blood channels, intercellular, 1 1 4 
 Blood corpuscles — struma, 2 1 , 44 
 
 abnormal changes, 34 
 
 action of reagents on,2l,32 
 
INDEX. 
 
 907 
 
 Blcod corpuscles — amoeboid 
 movements, 32 
 
 circulation of, 67 
 
 change of form, 22 
 
 chemical composition, 45 
 
 color, 21 
 
 conservation of, 33 
 
 crenation, 21 
 
 decay, 28 
 
 diapedesis, 32 
 
 distribution of, 157 
 
 effect of drugs, 32 
 
 effect of reagents, 21 
 
 form, 18, 24 
 
 Gower's method, 21 
 
 human, red, 18 
 white, 29 
 
 intracellular origin, 25 
 
 Malassez's method, 19 
 
 nucleated, 34 
 
 number, 19, 30 
 
 of newt, 30 
 
 origin, 25 
 
 pathological changes, 28 
 
 proteids of, 44 
 
 staining of, 23 
 
 size, 18, 24 
 
 stroma, 21, 44 
 
 transfusion of, 63 
 
 weight, 19 
 Blood current, 139 
 
 in capillaries, 140 
 
 velocity of, 155 
 Blood gases, 59 
 
 estimation of O, C0 2 , and 
 
 N,S9 
 extraction, 57 
 gas pumps for, 57 
 quantity, 59 
 Blood glands, 172 
 
 islands, 25, 879 
 . plasma, 18 
 
 Blood pressure, 141 
 arterial, 145 
 capillary, 151 
 estimation of, 141 
 in pulmonary artery, 153 
 in veins, 152 
 relation to pulse, 150 
 variations of, 145 
 Blood vessels, 1 1 1 
 
 action of acids 
 
 on, 115 
 cohesion of, 116 
 elasticity of, 116 
 lymphatics, 114 
 pathology of, 116 
 properties of, 115 
 structure of, 1 1 1 
 Blue pus, 489 
 
 sweat, 489 
 Body, vibrations of, 137 
 
 wall, formation of, 880 
 Bone, chemical composition of, 
 891 
 callus of, 404 
 development of, 892 
 
 Bone, effect of madder on, 405 
 fracture of, 404 
 growth of, 892 
 histogenesis of, 891 
 red marrow, 27 
 
 Bones, mechanism of, 533 
 
 Bothriocephalus, 857 
 
 Bottger's test, 246 
 
 Bouton's terminals, 846 
 
 Bowman's tubes, 751 
 
 Box pulse measurer, 117 
 
 Bradyphasia, 730 
 
 Brain, 675 
 
 arteries of, 7 1 1 
 blood vessels of, 710 
 general scheme of, 675 
 impulses, course of, 679 
 influence of, on cord, 700 
 in invertebrata, 746 
 membranes of, 740 
 motor centres of, 713, 
 
 718,719 
 movements of, 743 
 pressure on, 746 
 protective apparatus of, 
 
 742 
 pulse in, 137 
 psychical functions of, 
 
 703 
 pyramidal tracts of, 678 
 topography of, 725 
 weight of, 706 
 
 Brandy, 387 
 
 Bread, 383 
 
 Brenner's formula, 635 
 
 Broca's convolution, 729 
 
 Bromidrosis, 489 
 
 Bronchial breathing, 204 
 fremitus, 205 
 
 Bronchiole, 185 
 
 Bronchophony, 205 
 
 Bronchus extra pulmonary, 185 
 intra-pulmonary, 185 
 small, 185 
 
 Bronzed skin, 181 
 
 Brownian movement, 244 
 
 Bruit, 164 
 
 de diable, 164 
 
 Brunner's glands, 303, 324 
 
 Buchanan's experiments, 50 
 
 Bulbar paralysis, 686 
 
 Butter, 378 
 
 Butyric acid, 309 
 
 Caffein, 385 
 Calabar bean on eye, 619 
 Calcic phosphate, 458 
 Calculi biliary, 399 
 salivary, 242 
 urinary, 458 
 Callus, 404 
 Calorimeter, 347 
 Canal of cochlea, 825 
 
 hyaloid, 757 
 
 Nuck, 898 
 
 Petit, 757 
 
 Schlemm, 753 
 
 Canal, semicircular, 826 
 of spinal cord 654 
 of Stilling, 758 
 Canalis cochlearis, 825 
 
 reuniens, 825 
 Capillaries, 112 
 
 action of silver ni- 
 trate on, 113 
 blood current in, 
 
 160 
 circulation, 161 
 contractility of, 115 
 development of, 26 
 form and arrange- 
 ment of, 160 
 pressure in, 151 
 stigmata of, 113 
 velocity of blood in, 
 
 157 
 Capillary electrometer, 589 
 Capsule, external, 735 
 Glisson's, 285 
 internal, 735 
 of Tenon, 758 
 Carbolic acid urine, 440 
 Carbohydrates, 415 
 
 fermentation of, 
 308 
 Carbon dioxide, Conditions af- 
 fecting, 213 
 estimation of, 209 
 excretion of, 217 
 in air, 2 1 2 
 . in blood, 61 
 in expired air, 212 
 where formed, 219 
 Carbonic haemoglobin, 40 
 oxide, 40 
 poisoning by, 41 
 Cardiac cycle, 75 
 
 dullness, 93 
 ganglia, 94 
 hypertrophy, 77 
 impulse, 78 
 murmurs^ 91 
 nerves, 93 
 nutritive fluids, 96 
 plexus, 93 
 poisons, 103 
 revolution, 75 
 sounds, 88 
 Cardinal points, 761 
 Cardiogram, 78 
 Cardiograph, 79 
 
 Cardio-inhibitory centre, 148, 
 691 
 nerves, 640 
 Cardio - pneumatic movement, 
 
 104 
 Caricin, 266 
 Carnin, 417 
 Cartilage, 533, 880 
 Carotid gland, 114, 181 
 Casein, 378, 410 
 Catacrotic pulse, 121 
 Cataphoric action, 583 
 Cataract, 757 
 
908 
 
 INDEX. 
 
 Cathartics, 265 
 Cathelectrotonus, 598 
 Cathode, 579 
 Caudal heart of eel, 344 
 Caudate nucleus, 733 
 Cavernous formations, 114 
 Cells, division of, 856 
 Cellulose, 416 
 Cement, 251 
 
 action of silver nitrate 
 
 °n> "3.333 
 substance, 113 
 Centre, accelerans, 693 
 ano-spinal, 669 
 cardio-inhibitory, 691 
 cilio-spinal, 668 
 closure of eyelids, 685 
 dilator of pupil, 685 
 ejaculation, 669 
 erection. 669 
 for coughing, 685 
 for defalcation, 669 
 for mastication, 685 
 heat regulating, 702 
 micturition, 669 
 parturition, 669 
 pupil, 685 
 respiratory, 686 
 for saliva, 686 
 sneezing, 685 
 spasm, 685, 702 
 speech, 729 
 swallowing, 685 
 sweat, 669, 703 
 vasodilator, 669', 701 
 vasomotor, 669, 695 
 vesico-spinal, 669 
 vomiting, 685 
 of gravity, 540 
 Centrifugal nerves, 613 
 Centripetal nerves, 615 
 Centro-acinar cells, 278 
 Cereals, 383 
 Cerebellum — 
 Action of electricity on, 742 
 Connections of, 677 
 Function of, 740 
 Pathology of, 742 
 Removal of, 740 
 Structure of, 739 
 Cerebral arteries, 711, 744 
 epilepsy, 717, 728 
 fissures, dog, 715 
 inspiratory centre, 687, 
 motor centres, 713,718, 
 
 719 
 sensory centres, 721 
 vesicles, 877 
 Cerebrin, 413, 567 
 Cerebrospinal fluid, 743 
 Cerebrum, 709 
 
 bloodvessels of, 710, 
 
 743 
 convolutions of, 709 
 epilepsy of, 717 
 excision of centres, 
 
 721 
 
 Cerebrum, extirpation of, 704 
 Flourens' doctrine, 
 
 704 
 functions of, 704 
 Goltz's theory of, 725 
 imperfect develop- 
 ment of, 704 
 lobes of, 711 
 motor centres of, 
 
 713, 718, 720 
 motor regions of, 7 1 5, 
 
 725 
 movements of, 743 
 sensory centres, 721 
 sensory regions of, 
 
 721, 73' 
 structure of, 7°9 
 sulci and gyri of, 706 
 tactile areas of, 724 
 thermal centres of, 
 
 724 
 weight of, 706 
 
 Cerumen, 485 
 
 Cervical sympathetic, section of, 
 651 
 
 Chalazae, 865 
 
 Charcot's crystals, 228 
 disease, 614 
 
 Cheese, 380 
 
 Chemical affinity, xxxv 
 
 Chess-board phenomenon, 809 
 
 Chest, dimensions of, 201 
 
 Cheyne-Stokes' phenomenon, 
 196 
 
 Chiasma, 617 
 
 Chitin, 413 
 
 Chloasma, 486 
 
 Chlorophane, 757 
 
 Chlorosis, 34 
 
 Chocolate, 385 
 
 Cholsemia, 301 
 
 Cholalic acid, 294, 415 
 
 Cholesteraemia, 301 
 
 Cholesterin, 45, 296, 302, 415 
 
 Choletelin, 295 
 
 Cholin, 567 
 
 Choloidinic acid, 294 
 
 Choluria, 450 
 
 Chondrin, 411 
 
 Chondrogen, 412 
 
 Chorda dorsalis, 877 
 
 Chorda tympani, 631, 701 
 
 Chordae tendine<e, 76 
 
 Chorion laeve, 884 
 
 frondosum, 884 
 primitive, 883 
 
 Choroid, 753 
 
 Choroidal fissure, 901 
 
 Christison's formula, 427 
 
 Chromatic aberration, 774 
 
 Chromatophores, 490 
 
 Chromatopsia, 618 
 
 Chromidrosis, 489 
 
 Chromophanes, 757 
 
 Chronograph, 515 
 
 Chyle, 337, 339 
 
 movement of, 341 
 
 Chyle vessels, 341 
 Chylous urine, 457 
 Chyme, 274 
 Cicatricula, 864 
 Cilia, 491 
 
 conditions for movement, 
 
 492 
 effect of reagents on, 492 
 functions of, 492 
 Ciliary motion, 491 
 
 force of, 492 
 ganglion, 623 
 muscle, 768 
 nerves, 623 
 Ciliated epithelium, 491 
 Cilio-spinal region, 668, 776 
 Circle of Willis, 744 
 Circulating albumin, 389 
 Circulation, capillary, 161 
 duration of, 159 
 first, 879 
 portal, 67 
 pulmonary, 67 \ 
 schemata of, 140 
 second, 879 
 systemic, 67 
 Circumpolarization, 247 
 Claustrum, 735 
 Cleavage of yelk, 874 
 lines of, 874 
 partial, 877 
 Cleft sternum, 77 
 palate, 889 
 Clerk - Maxwell's experiment, 
 
 781 
 Climacteric, 867 
 Clitoris, 899 
 Closing, continued contraction, 
 
 600 
 Closing shock, 584 
 Clothing, 363 
 Coagulable fluids, 54 
 Coagulated proteids, 410 
 Coagulation experiments, 52 
 Coagulation of blood, 46-52 
 
 theories of, 52, 53 
 Cocaine, 777. 
 
 Coccygeal gland, 114, 181, 490 
 Cochlea, 825 
 Cocoa, 385 
 Coecitas verbal is, 731 
 Coelom, 880 
 Coffee, 385 
 
 Cold-blooded animals, 350, 370 
 Cold on the body, 370, 371 
 
 uses of, 371 
 Collagen, 277, 411 
 Colloids, 327 
 Coloboma, 901 
 Color associations, 837 
 blindness, 794 
 
 acquired, 795 
 testing, 796 
 sensation, 791 
 Hering's theory, 793 
 Young- Helmholtz theory, 
 793 
 
INDEX. 
 
 909 
 
 Colorless corpuscles, 29 
 Color top, 797 
 Colors, complementary, 791 
 contrast, 791 
 geometrical table, 792 
 methods of mixing, 791 
 mixed, 791 
 simple, 791 
 Colostrum, 379 
 Columella, 837 
 Columns of the cord, 614 
 Coma, diabetic, 292 
 Comedo, 489 
 Common sensation, 853 
 Comparative — 
 Absorption, 346 
 Circulation, 181 
 Digestion, 317 
 Hearing, 837 
 Heat, 372 
 
 Kidney and urine, 476 
 Metabolism, 417 
 Motor organs, 543 
 Nerve centres, 746 
 Nerves and electro-physiology, 
 
 611 
 Peripheral nerves, 652 
 Reproduction and develop- 
 ment, 903 
 Respiration, 230 
 Sight, 312 
 Skin, 490 
 
 Voice and speech, 558 
 Compensation, 589 
 Complemental air, 191 
 Complementary colors, 791 
 Compound eye, 312 
 Condensed milk, 380 
 Condiments, 385 
 Conduction in the cord, 671 
 Conductivity, 605 
 Conglutin, 410 
 Conjugate deviation,' 620, 727 
 Conjugation, 857 
 Connective-tissue spaces, 332. 
 Consonance, 835 
 Consonants, 555 
 Constant current, use of, 518 
 Constant elements — 
 Bunsen's, 580 
 Daniell's, 581 
 Grennet, 581 
 Grove's, 580 
 Leclanche's, 581 
 Smee's, 581 
 Constipation, 316 
 Contraction, cardiac, 105 
 
 muscular(see Myo 
 
 gram). 
 fibrillar, 512 
 initial, 523 
 of blood vessels, 
 
 114. 
 remainder, 520 
 rhythmical, 510 
 secondary, 592 
 without metals, 591 
 
 Contracture, 520 
 Contrast, 798 
 
 colors, 791 
 Convergent lens, action of, 759 
 Cornea, 750 
 Coronary vessels, 73 
 
 effects of ligature of, 
 
 74 
 Corpora quadrigemina, 737 
 Corpulence, 399 
 Corpus callosum, 739 
 
 luteum, 869 
 
 spongiosum, 869 
 
 striatum, 733 
 Cortical blindness, 722 
 Corti's organ, 825 
 Cotyledons, 886 
 Coughing, 207 
 
 centre for, 685 
 Cracked-pot sound, 204 
 Cramp, 855 
 Cranial flexures, 877 
 
 nerves, 596- 6 / j 
 Cranioscopy, 704 
 Crepitation, 205 
 Crescents of Gianuzzi, 234 
 Crista acustica, 826 
 Crossed reflexes, 663 
 Crusta petrosa, 250 
 
 phlogistica, 47 
 Crying, 208 
 CrystalHn, 409, 757 
 Crystalline spheres, 81 2 
 Crystallized bile, 293 
 Crystalloids, 327 
 Cubic space, 226 
 Curara, action of, 507, 510 
 Cutaneous respiration, 219 
 
 trophic affections, 613 
 Cuticular membrane, 250 
 Cyanogen, 42 
 Cyanuric acid, 417 
 Cylindrical lenses, 774 
 Cyrtometer, 201 
 Cysticercus, 857 
 Cystin, 417 
 Cytozoon, 22 
 
 Daltonism, 795 
 Damping apparatus, 818 
 Darby's fluid meat, 275 
 Death of a nerve, 576 
 Debove's membrane, 183 
 Decidua reflexa, 883 
 serotina, 883 
 vera, 882 
 Decubitus acutus, 735 
 Defecation, 261 
 
 centre for, 669 
 Degeneration, fatty, 400 
 Deglutition^ 254 
 
 nerves of, 255 
 Deiter's cells, 827 
 Demarcation current, 592 
 Demodex folliculorum, 485 
 Dentine, 249 
 Dentition, 249 
 
 Depressor fibres, 697 
 
 nerve, 146, 640 
 Development, chronology of, 
 
 886 
 Dextrin, 416 
 Dextrose, 415 
 Diabetes mellitus, 64, 451 
 Diabetic coma, 292 
 Dialysis, 327 
 Diapedesis, 32, 162 
 Diaphragm, 197 
 Diaphoretics, 486 
 Diarrhoea, 316 
 
 Diastatic action, 245, 280, 412 
 Diastole, 75, 78 
 Dicrotic pulse, 1 23 
 wave, 124 
 Diet, adequate, 389 
 
 effect of age on, 393 
 effect of work on, 393 
 flesh, 397 
 flesh and fat, 397 
 of carbohydrates, 397 
 quality of, 391 
 quantity, 392 
 Difference theory, 596 
 Differential rheotom, 594 
 
 tones, 836 
 Diffusion, 326 
 
 circles, 766 
 of gases, 57 
 Digestion during fever, 315 
 
 in plants, 317 
 Digestion, 232 
 
 artificial, 275, 315 
 Digestive apparatus, 248 
 Dilatation of pupil, centre for, 
 
 668 
 Dilator pupillas, 776 
 Dioptric, 774 
 
 observations, 759 
 Diphthongia, 558 
 Diphthongs, 557 
 Diplopia, 619, 804 
 Direct vision, 788 
 Direction, 836 
 Discharging forces, 506 
 Discus proligerus, 863 
 Disdiaclasts, 500 
 Dissociation, 218 
 Dissonance, 836 
 Distance, estimation of, 809 
 
 false estimate of, 810 
 Diuretics, 460 
 
 Double conduction in nerve, 
 605 
 images, neglect of, 805 
 Dreams, 707 
 Drepanidium, 23 
 Dromograph, 156 
 Dropsy, 344 
 Ductus arteriosus, 886 
 
 venosus, 886 
 Dura mater, 742 
 Dust particles, 225 
 Dyschromatopsy, 794 
 Dyslysin, 294 
 
910 
 
 INDEX. 
 
 Dysperistalsis, 263 
 Dyspnoea, 195, 222, 688 
 
 Ear, 814 
 
 conduction in, 815 
 development of, 901 
 external, 816 
 fatigue of, 837 
 fineness of, 830 
 labyrinth of, 825 
 meatus of, 816 
 ossicles of, 819 
 speculum, 819 
 tympanum of, 816 
 Earthy phosphates, 442 
 Eccentric hypertrophy, 77 
 Ecchymoses, 698 
 Echo speech, 708 
 Ectoderm, 875 
 Ectopia cordis, 85 
 Efferent nerves, 613 
 Egg albumin, 55 
 Eggs, 381 
 
 Ejaculation, centre for, 870 
 Elastic after effect, 116 
 elevations, 126 
 tension, 154, 190 
 tubes, no 
 Elasticity of blood vessels, 1 1 5 
 lens, 768 
 muscle, 526 
 Elastin, 411 
 
 Electrical charge of body, 611 
 fishes, 61 1 
 nerves, 606 
 organs, 612 
 Electrical currents of muscle,588 
 eye, 594 
 glands, 59 1 
 mucous membranes, 
 
 591 
 nerve, 590 
 skin, 591 
 Electricity, therapeutical uses, 
 
 606 
 Electrodes, non-polarizable, 582 
 
 other forms, 606 
 Electrolysis, 579 
 Electrometer, 589 
 Electro-therapeutics, 606 
 Electro-motive force, 577 
 Electro- physiology, 577 
 Electrotonus, 594 
 
 in inhibitory nerves, 
 
 601 
 in motor nerves, 598 
 in muscle, 601 
 in sensory nerves, 
 601 
 Eleidin, 477 
 Elementary granules of blood, 
 
 34 
 Emetics, 259 
 Emmetropic eye, 770 
 Emotions, expression of, 559 
 Emulsification, 283 
 Emulson, 344 
 
 Emydin, 410 
 
 Enamel, 250 
 
 Enamel organ, 251 
 
 End arteries, 160 
 bulbs, 846 
 capsules, 846 
 organ, 613 
 plate, 498 
 
 Endocardial pressure, 85 
 
 Endocardium, 71 
 
 Endoderm, 875 
 
 Endolymph, 825 
 
 Endoneurium, 565 
 
 Endosmometer, 326 
 
 Endosmosis, 327 
 
 Endosmotic equivalent, 326 
 
 Enemata, 331 
 
 Energy, conservation of, xxxvi 
 potential, xxxvi 
 
 Entoptical phenomena, 779 
 pulse, 780 
 
 Entotical perceptions, 837 
 
 Enuresis nocturna, 475 
 
 Enzym, 412 
 
 Epiblast, 875 
 
 Epicardium, 68 
 
 Epidural space, 947 
 
 Epididymis, 858 
 
 Epigenesis, 904 
 
 Epiglottis, 255 
 
 Epilepsy, 703, 717, 728 
 
 Epineurium, 565 
 
 Epithelium ciliated, 183, 225 
 squamous, 232 
 
 Eponychium, 480 
 
 Equator, 588 
 
 Erectile tissue, 870 
 
 Erection, centre, for, 870 
 
 of penis, 869 
 Erect vision, 766 
 Errhines, 207 
 Erythrochlorophy, 795 
 Erythrodextrin, 244 
 Ether, xxxii 
 Eudiometer, 59 
 Eukalyn, 417 
 Euperii-talsis, 262 
 Eupncea, 688 
 Eustachian catheter, 824 
 
 tube, 822 
 Excitability, action of poisons 
 
 on, 671 
 Excitable points of a nerve, 576 
 Excito-motor nerves, 615 
 Excretin, 311 
 
 Excretion of faecal matter, 260 
 Exophthalmos, 799 
 Expectorants, 227 
 Expiration, 197 
 Expiratory muscles, 197 
 Explosives, 557 
 Extensor tetanus, 663 
 External genitals, 899 
 Extra current, 584 
 Extrapolar region, 598 
 Extremities, development of, 
 881 
 
 Exudation, 345 
 Eye, 750 
 
 accommodation of, 766 
 
 artificial, 765 
 
 astigmatism, 775 
 
 chromatic aberration of, 
 
 774 
 compound, 812 
 development of, 901 
 effect of electrical currents, 
 
 780 
 emmetropic, 773 
 entoptical phenomena, 779 
 excised, 778 
 fundus of, 781 
 hypermetropic, 771 
 illumination of, 781 
 movements of, 799 
 muscles of, 801 
 myopic, 771 
 presbyopic, 772 
 protective organs of, 810 
 structure of, 750 
 Eyeballs, axis of, 800 
 
 movements of, 801 
 muscles of, 801 
 planes of, 800 
 positions of, 800 
 protrusion of, 799 
 retraction of 799 
 simultaneous move- 
 ments of, 803 
 Eye currents, 594 
 Eyelids, 810 
 
 Facial nerve, 631 
 Faecal matter, 312 
 Fainting, 78 
 Fallopian tubes, 866 
 Falsetto voice, 554 
 Faradic current, 584 
 Faradization in paralysis, 607 
 Far point, 770 
 Fascia, lymphatics of, 341 
 Fatigue of muscle, 518 
 stuffs, 519, 531 
 Fats, 413 
 
 decomposition of, 282 
 fermentation of, 309 
 metabolism of, 397 
 origin of, 398 
 Fat-splitting ferment, 283 
 Fatty acids, 413 
 
 degeneration, 400 
 Fechner's law, 749 
 Fchling's solution, 246, 452 
 Ferments, 41 2 
 
 fate of, 306 
 organized, 412 
 unorganized, 412 
 Fermentation, 386 
 
 in intestine, 307 
 test, 247 
 Fertilization of ovum, 872 
 Fever, 367 
 
 after transfusion, 169 
 Fibres of Tomes, 249 
 
INDEX. 
 
 911 
 
 Fibrillar contraction, 512 
 Fibrin, 34, 46 
 Fibrin factors, 46 
 Fibrin ferment, 46, 52 
 Fibrinogen, 50,410 
 Fibrinoplastin, 50 
 Fibroin, 41 1 
 Field of vision, 765 
 
 contest of, 808 
 Filaria sanguinis, 457 
 Filtration, 327 
 
 First" respiration, discharge of, 
 690 
 effects of, on thorax, 206 
 Fish extract, 383 
 Fission, 856 
 Fistula, biliary, 298 
 gastric, 273 
 intestinal, 304 
 pancreatic, 279 
 Thiry's, 304 
 Vella's, 305 
 Flame spectra, 38 
 Flavor, 840 
 Fleischl's law of contraction, 
 
 601 
 Flesh, 38 r 
 Floor space, 226 
 Flourens' doctrine, 704 
 Fluid vein, 164 
 Fluids, flow of, 108 
 
 introduction of, 248 
 Fluorescence, 791 
 
 of eye, 766 
 Fluorescin, 759 
 Focal line, 761 
 
 point, 761 
 Foetal circulation, 885 
 membranes, 886 
 Follicles, solitary, 324 
 Fontana's markings, 568 
 Fontanelle,. pulse in, 137 
 Foods — 
 
 isodynamic, 348 
 plastic, 389 
 quantity, 392 
 respiratory, 393 
 Foramen ovale, 886 
 
 of Magendie, 743 
 Force of accommodation, 772 
 Forced movements, 738 
 Forces, xxxiii 
 Formatio reticularis, 683 
 Formative cells, 877 
 Fovea cardica, 879 
 centralis, 787 
 Fractional heat coagulation, 
 
 55 
 Free acid, formation of, 271 
 Fremitus, 205 
 Friction sounds, 205 
 Frog current, 591 
 Fiomann's lines, 563 
 Fruits, 384 
 
 Fundamental note, 817 
 Fundus glands, 266 
 Fungi, 307 
 
 Gaertner, ducts of, 889 
 Galactorrhcea, 370 
 Galactose, 415 
 Gallop, 544 
 Gall stones, 315 
 Galton's whistle, 829 
 Galvanic battery, 577 
 
 excitability, 609 
 Gal vano cautery, 611 
 Galvanometer, 578 
 
 reflecting, 582 
 Galvano-puncture, 611 
 
 tetanus, 571 
 Ganglionic arteries, 744 
 Gangrene, 614 
 Gargling, 208 
 Gas pump for blood, 57 
 Gaseous exchanges, 213, 216 
 
 effects on, 
 213 
 Gases, 307 
 
 diffusion of, 216 
 
 in blood, 59 
 
 in stomach, 278 
 
 indifferent, 225 
 
 irrespirable, 225 
 
 poisonous, 225 
 
 respired, 191 
 Gaskell's clamp, 97 
 Gas sphygmoscope, 122 
 Gasserian ganglion, 626 
 Gastric digestion, 274 
 
 conditions affecting, 275, 
 
 3H 
 fistula, 315 
 pathological variations, 
 
 3'4 
 
 Gastric giddiness, 636 
 
 Gastric juice, 269 
 
 action of drugs on, 273 
 action on tissues, 277 
 actions of, 276 
 artificial, 273 
 
 Gaule's experiment, 22 
 
 Gelatin v. albumin, 396 
 
 Gemmation, 856 
 
 Genital cord, 898 
 
 eminence, 899 
 
 Genu valgum, 538 
 varum, 538 
 
 Geometrical color table, 792 
 
 Germ epithelium, 863 
 
 Germinal area, 875 
 
 Germs, 226 
 
 Gestation, period of, 887 
 
 Giddiness, 625, 636 
 
 Ginglymus, 534 
 
 Giraldes, organ of, 899 
 
 Girdle sensaiion, 672 
 
 Glance, 808 
 
 Glands, albuminous, 232 
 Bowman's, 839 
 Brunner's, 303 
 buccal, 232 
 carotid, 114, 181 
 ceruminous, 482 
 changes in, 235, 253 
 
 Glands, coccygeal, 114, 181 
 
 Ebner's, 232 
 
 fundus, 266 
 
 Harderiau, 813 
 
 lachrymal, 810 
 
 Lieberkiihn's, 304 
 
 lingual, 232 
 
 lymph, 336 
 
 mammary, 375 
 
 Meibomian, 810 
 
 mixed, 232 
 
 mucus, 232, 236 
 
 Nuhn's, 232 
 
 parotid, 233 
 
 peptic, 266 
 
 Peyer's, 325 
 
 pyloric, 267 
 
 salivary, 233 
 
 sebaceous, 482 
 
 serous, 232, 235 
 
 solitary, 324 
 
 sublingual, 240 
 
 sweat, 483 
 
 uterine, 866 
 
 Weber's, 233 
 Glaucoma, 626 
 Gliadin, 410 
 Globin, 409 
 Globulins, 410 
 Glomerulus, 421 
 Glosso-pharyngeal nerve, 627 
 Glossoplegia, 645 
 Glossy skin, 614 
 Glottis, 547 
 Glucose, 415 
 
 tests for, 246, 451 
 Glucosides, 413 
 Glutaminic acid, 417 
 Gluten, 384, 410 
 Glycerin, 414, 415 
 
 method, 273 
 Glycerin-phosphoric acid, 414 
 Glycerinic acid, 310 
 Glycin, 310, 411 
 Glycocholic acid, 293 
 Glycogen, 288, 416 
 Glycolic acids, 414 
 Glycosuria, 290, 451 
 Gmelin-Heintz, reaction, 295, 
 
 451 
 
 Goblet cells, 321 
 
 Goitre, 180 
 
 Goll's column, 655 
 
 Goltz's croaking experiment, 
 663 
 embrace experiment, 664 
 
 Gorham's pupil photometer, 778 
 
 Gout, 65 
 
 Graafian follicle, 863 
 
 Granules, elementary, 34 
 
 Granulose, 244 
 
 Grape sugar, 415 
 
 absorption of, 328 
 estimation of, 247 
 in urine, 45 1 
 tests for, 246, 45 1 
 volumetric analysis, 452 
 
912 
 
 INDEX. 
 
 Gravitation, xxxiii 
 
 Great auricular nerve, 698 
 
 Green blindness, 795 
 
 Green vegetables, 384 
 
 Growth, 388, 417 
 
 of bones, 613 
 
 Guanidin, 519 
 
 Guanin, 417 
 
 Gubernaculum testis, 898 
 
 Gum, 416 
 
 Gustatory fibres, 632 
 centre, 724 
 region, 841 
 sensations, 842 
 
 Gymnastics, 538 
 
 Gymnotus, 612 
 
 Gyri, 675 
 
 Hay's reaction, 45 1 
 
 Hemacytometer, 21 
 
 Haemadynamometer, 141 
 
 Hematin, 42,413 
 
 Hematoblasts, 33 
 
 Haematohidrosis, 489 
 
 Haematoidin, 44, 451, 869 
 
 Hematoma aurium, 6 14 
 
 Hematoporphyrin, 42 
 
 Hematuria, 447 
 
 Hsemautography, 122 
 
 Hsemin and its tests, 43 
 
 Hemochromogen, 42 
 
 Hemocyanin, 25 
 
 Hemocytolysis, 22 
 
 Hemocytometer, 21 
 
 Hemocytotrypsis, 22 
 
 Haemodromometer, 155 
 
 Hsemodynamometer, 141 
 
 Haemoglobin, 35 
 
 analysis, 35 
 carbonic oxide, 40 
 compounds of, 39 
 crystals, 36 
 decomposition of, 
 
 42 
 estimation of, 36 
 nitric oxide, 42 
 pathological, 38 
 preparation, 36 
 proteids of, 44 
 reduced, 40 
 spectrum, 39 
 
 Haemoglobinometer, 36 
 
 Haemoglobinuria, 170, 447 
 
 Haemophilia, 48 
 
 Hemorrhage, death by, 65 
 effect of, 696 
 
 Hemorrhagic diathesis, 48 
 
 Haemotachometer, 156 
 
 Haidinger's brushes, 78 1 
 
 Hair, 480 
 
 follicle, 481 
 
 Halisterisis, 539 
 
 Hallucinations, 749 
 
 Hammarsten on blood, 54 
 
 Harderian gland, 813 
 
 Hare-lip, 889 
 
 Harmony, 836 
 
 Harrison's groove, 195 
 
 Hassall's corpuscles, 177 
 
 Hawking, 207 
 
 Head-fold, 878 
 
 Head-gut, 878 
 
 Heart, 67 
 
 accelerated action, 84 
 action of fluids on, 96 
 action of gases, 92, 103 
 action of poisons on, 103 
 apex beat, 99 
 arrangement of fibres, 70 
 aspiration of, 152 
 auricular systole, 75 
 automatic centres, 95 
 blood vessels of, 72 
 changes in shape, 82 
 chordae tendineae, 76 
 cutting experiments, 96, 
 
 97 
 
 development of, 879 
 
 diastole, 75 
 
 duration of movements, 
 92 
 
 endocardium, 141 
 
 examination of, 92 
 
 frog's, 94 
 
 ganglia of, 93 
 
 innervation of, 93 
 
 movements of, 75 
 
 muscular fibres', 67 
 
 myocardium, 68 
 
 nerves, 93 
 
 nutritive fluids, 96 
 
 palpitation of, 78 
 
 pause of, 77 
 
 pericardium, 71 
 
 Purkinje's fibres, 72 
 
 regulation of, 73 
 
 sounds of, 88, 91 
 
 staircase beats of, 97 
 
 systole, 75 
 
 valves of, 72 
 
 weight.73 
 
 work of, 159 
 Heat, xxxv 
 
 balance of, 363 
 calorimeter, 356 
 conductivity, 357 
 dyspnoea, 688 
 employment of, 369 
 estimation of, 356 
 excretion of, 362 
 income and expenditure, 
 
 303 
 in inflamed parts, 372 
 latent, 347 
 
 regulating centre, 702 
 relation to work, 365 
 sources of, 347, 348 
 specific, 356 
 stiffening, 504 
 storage of, 367 
 units, xxv, 348 
 variations in production, 
 36S 
 Helicotrema, 825 
 
 Heller's test, 246, 446 
 blood test, 450 
 
 Helmholtz's modification, 585 
 
 Hemeralopia, 618 
 
 Hemialbumin, 274 
 
 Hemialbumose, 274 
 
 Hemianaesthesia, 733 
 
 Hemianopsia, 617 
 
 Hemicrania, 701 
 
 Hemiopia, 617, 732 
 
 Hemipeptone, 282 
 
 Hemiplegia, 726 
 
 Hemisystole, 88 
 
 Henle's loop, 424 
 sheath, 565 
 
 Hen's egg, 864 
 
 Hensen's experiments, 835 
 
 Hepatic cells, 286 
 
 chemical composition 
 
 of, 288 
 zones, 286 
 
 Hepatogenic icterus, 299 
 
 Herbst's corpuscles, 846 
 
 Hermann's theory of tissue cur- 
 rents, 596 
 
 Herpes, 614 
 
 Heterologous stimuli, 748 
 
 Hewson's experiments, 49 
 
 Hiccough, 208 
 
 Hippuric acid, 438, 465 
 
 Hippus, 620 
 
 Historical — 
 Absorption, 346 
 Circulation, 182 
 Digestion, 317 
 Hearing, 837 
 Heat, 372 
 
 Kidney and urine, 475 
 Nerves and electro- physi- 
 ology, 61 1 
 Nerve centres, 746 
 Peripheral nerves, 652 
 Reproduction and develop- 
 ment, 903 
 Respiration, 230 
 Sight, 812 
 Skin, 490 
 Voice and speech, 559 
 
 Hoarseness, 558 
 
 Holoblastic ova, 864 
 
 Homoiothermal animals, 350 
 
 Homologous stimuli, 748 
 
 Horopter, 804 
 
 Howship's lacunae, 892 
 
 Humor, aqueous, 758 
 
 Hunger and starvation, 394 
 
 Hyaloid canal, 757 
 
 Hybernation, 371 
 
 Hybrids, 873 
 
 Hydatids, 857 
 
 Hydremia, 66 
 
 Hydramnion, 882 
 
 Hydrobilirubin, 295 
 
 Hydrocephalus, 745 
 
 Hydrochinon, 440 
 
 Hydrochloric acid, 269 
 
 Hydrocyanic acid, 42 
 
INDEX. 
 
 913 
 
 Hydrogen given off, 418 
 
 in body, 407 
 Hydrolytic ferments, 41 2 
 Hydronephrosis, 475 
 Hydrostatic test, 190 
 Hydroxylbenzol, 440 
 Hypakusis, 635 
 Hypalgia, 854 
 Hyperesthesia, 671 
 Hyperakusis, 634, 635 
 Hyperalgia, 854 
 Hyperdicrotism, 127 
 Hypergeusia, 843 
 Hyperglobulie, 64 
 Hyperidrosis, 488 
 Hyperinosis, 65 
 Hyperkinesia, 671 
 Hypermetropia, 771, 774 
 Hyperoptic, 771 
 Hyperosmia, 616 
 Hyperpselaphesia, 853 
 Hypertrophy of heart, 77 
 
 muscle, 539 
 Hypnotism, 708 
 Hypoblast, 875 
 Hypogeusia, 843 
 Hypoglossal nerve, 645 
 Hypophysis cerebri, 181, 900 
 Hypopselaphesia, 853 
 Hyposmia, 616 
 Hypospadias, 899 
 Hypoxanthin, 41 1 
 
 Ichthidin, 410 
 
 Icterus, 299 
 
 Identical points, 803 
 
 Ileo-colic valve, 259 
 
 Ileus, 259 
 
 Illumination of eye, 781 
 
 Illusion, 749 
 
 Images, formation of, 761 
 
 Imbibition currents, 597 
 
 Impregnation, 874 
 
 Impulse, cardiac, 78 
 
 Impulses in brain, course of, 
 671, 678 
 
 Inanition, 395 
 
 Income, 389 
 
 Indican, 440 
 
 Indifferent point, 590 
 
 Indigo blue, 440 
 
 Indigogen, 440 
 
 Indirect vision, 784 
 
 Indol, 310 
 
 Induction, 584 
 
 Indiictorium, 586 
 
 Inferior maxillary nerve, 627 
 
 Inhibition, nature of, 665 
 
 Inhibition of reflexes, 664 
 
 Inhibitory action of brain, 725 
 nerves, 614 
 for heart, 691 
 for intestine, 264 
 for respiration, 686 
 
 Inosinic acid, 417 
 
 Inosit, 416 
 
 Insectivorous plants, 317 
 
 58 
 
 Inspiration, 196 
 
 muscles of, 196 
 ordinary, 196 
 Intelligence, degree of, 706 
 Intercellular blood channels, 1 14 
 Intercentral nerves, 615 
 Intercostal muscles, 199 
 Interference, 835 
 Interglobular spaces, 250 
 Interlobular vein, 285 
 Internal capsule, 734 
 
 reproductive organs, 898 
 respiration, 219 
 Intestinal fistula, 304 
 gases, 307 
 juice, 303 
 
 actions of, 305 
 paresis, 264 
 Intestine, 259 
 
 artificial circulation, 
 
 265 
 development of, 895 
 effect of drugs on, 265 
 fermentation processes 
 
 in, 307 
 large, 311, 320 
 movements of, 259 
 small, 319 
 Intralobular vein, 285 
 Intraocular pressure, 624, 758 
 Intussusception, 259 
 Inulin, 416 
 Inunction, 489 
 Invertin, 306 
 Invert sugar, 306 
 Ions, 579 
 Iris, 775 
 
 Iris, action of poisons on, 777 
 blood vessels of, 776 
 functions of, 775 
 movements of, 778 
 muscles of, 776 
 nerves of, 776 
 Irradiation, 797 
 
 of pain, 672, 853 
 Ischuria, 475 
 Island of Reil, 711 
 Isodynamic foods, 348 
 Isolated beats, 836 
 Isotropous, 500 
 
 Jacksonian epilepsy, 717, 728 
 
 Jacobson's organ, 839 
 
 Jaeger's types, 771 
 
 Jaundice, 299 
 
 Jaw-jerk, 667 
 
 Joints — 
 
 Arthrodial, 535 
 Ball and socket, 535 
 Ginglymus, 534 
 Mechanism of, 533 
 Rigid, S3S 
 Screw-hinge, 534 
 
 Juice canals, 332 
 
 Karyokinesis, 856 
 Katabolic, 373, 615 
 Katalepsy, 708 
 
 Kations, 579 
 Keratin, 411 
 Keratitis, 633 
 Key-note, 829 
 Keys — 
 
 Capillary contact, 588 
 
 Friction, 588 
 
 Plug, 588 
 Kidney, 419 
 
 blood of, 424 
 
 chemistry of, 465 
 
 conditions affecting, 466 
 
 reabsorption in, 463 
 
 structure of, 419 
 
 volume of, 467 
 Kinsesodic substance, 670 
 Kinetic energy, 347 
 theory, 636 
 Klang, 828, 836 
 Knee phenomenon, 667 
 
 reflex, 667 
 Kcenig's manometric flames, 833 
 Koumiss, 380 
 Krause's end bulbs, 845 
 Kreatin, 417 
 Kreatinin, 417, 436 
 
 properties, 436 
 quantity, 436 
 test, 436 * 
 Kresol, 417 
 
 Kryptophanic acid, 441 
 Kymograph, 141 
 
 Fick's, 143 
 Ludwig's, 141 
 Kyphosis, 538 
 
 Labials, 557 
 
 Labor, power of, 902 
 
 Labyrinth, 824 
 
 Lachrymal apparatus, 810 
 
 Lacteals, 319 
 
 Lactic acid, 414, 441 
 
 ferment, 277 
 
 Lactoprotein, 378 
 
 Lactose, 376 
 
 Lsevulose, 415 
 
 Lagophthalmus, 620 
 
 Lambert's method, 791 
 
 Lamina spiralis, 825 
 
 Laminae dorsales, 877 
 
 Language, 729 
 
 Lanoline, 485 
 
 Lanugo, 480 
 
 Lapping, 248 
 
 Lardacein, 410 
 
 Large intestine, 311, 319 
 absorption in, 311 
 
 Laryngoscope, 551 
 
 Larynx — 
 
 Cartilages of, 545 
 During respiration, 200 
 Experiments on, 552 
 Illumination of, 551 
 Mucous membrane of, 550 
 Muscles of, 547 
 View of, 552 
 Vocal cords, 546 
 
914 
 
 Latent heat, 347 
 
 period, 664 
 Lateral plates, 878 
 Laughing, 208 
 Law of conservation of energy, 
 
 xxxvi 
 contraction, 601 
 isolated conduction, 606 
 peripheral perception, 847 
 specific energy, 748 
 Leaping, 542 
 Lecithin, 45, 414, S 6 7 
 Legumin, 383, 410 
 Lens, chemistry of, 757 
 crystalline, 757 
 - development of, 901 
 Lenticular nucleus, 733 
 Leptothrix buccalis, 228 
 Leucic acid, 414 
 Leucin, 310, 414, 454 
 Leucocytes, 29 
 Leucoderma, 614 
 Leukaemia, 35 
 Levers, 536 
 Lichenin, 416 
 Lieberkiihn's glands, 304 
 Liebig's extract, 383 
 Life, xxxix 
 Liminal intensity, 748 
 Line of accommodation, 770 
 Ling's system, 538 
 Lingual nerve, 627 
 Lipaemia, 65 
 Liquor sanguinis, 46 
 Listing's reduced eye, 764 
 Liver, 284 
 
 chemical composition, 
 288 
 
 cirrhosis of, 288 
 
 development of, 897 
 
 fat in, 289 
 
 functions of, 292 
 
 glycogen in, 291 
 
 influence on metabolism, 
 298 
 
 pathology of, 288 
 
 pulse in, 166 
 
 regeneration of, 288 
 
 structure of, 284 
 Locality, sense of, 847 
 
 illusions of, 849 
 Lochia, 903 
 Locomotor ataxia, 672 
 Lordosis, 538 
 Loss of weight, 395 
 Loss by skin, 219 
 Lowe's ring, 781 
 Lungs, 183 
 
 chemical composition of, 
 189 
 
 development of, 896 
 
 elastic tension of, 154 
 
 examination of, 194 
 
 excision of, 190 
 
 limits of, 202 
 
 physical properties, 189 
 
 structure of, 188 
 
 INDEX. 
 
 Lungs, tonus, 189 
 
 Lunule, 480 
 
 Lutein, 869 
 
 Luxus consumption, 389 
 
 Lymph, 332 
 
 movement of, 341 
 
 gases of, 220 
 Lymph corpuscles, 337 
 
 ' origin and decay of, 340 
 Lymphatics, 332 
 
 of eye, 758 
 origin of, 332 
 Lymph follicles, 335 
 
 glands, 335 
 
 hearts, 343 
 
 Macropia, 620 
 
 Macula lutea, 755 
 
 Maculae acusticse, 826 
 
 Madder, feeding with, 405 
 
 Magnetization, 584 
 
 Magneto-induction, 585 
 
 Major cord, 829 
 
 Malapterurus, 616 
 
 Malt, 387 
 
 Maltose, 244, 415 
 
 Mammary glands, 375 
 
 changes in, 375 
 development of, 376 
 structure of, 375 
 
 Manometer, 106 
 
 Manometric flames, 833 
 
 Marey's tambour, 80 
 
 Margarin, 478 
 
 Mariotte's experiment, 785 
 
 Mastication, 248 
 
 muscles of, 248 
 nerves of, 249 
 
 Massage, 538 
 
 Mate, 385 
 
 Matter, xxxii 
 
 Maturation of ovum, 873 
 
 Meat soup, 383 
 
 Meckel's cartilage, 889 
 ganglion, 626 
 
 Meconium, 302 
 
 Medulla oblongata — 
 
 Functions of, 682 
 Gray matter of, 682 
 Reflex centres in, 685 
 Structure of, 681 
 
 Medullary groove, 875 
 tube, 877 
 
 Meiocardia, 104 
 
 Meissner's plexus, 262 
 
 Melansemia, 35 
 
 Melanin, 413 
 
 Melitose, 416 
 
 Mellittemia, 64 
 
 Membrana decidua menstrualis, 
 882 
 flaccida, 817 
 reticularis, 827 
 reuniens, 880 
 secundaria, 824 
 tectoria, 827 
 
 Membranes of brain, 742 
 
 Meniere's disease, 637 
 
 Menopause, 867 
 
 Menstruation, 867 
 
 Merkel's cells, 846 
 
 Meroblastic ova, 864 
 
 Mesentery, development of, 897 
 
 Mesoblast, 875 
 
 Mesonephros, 898 
 
 Metabolic equilibrium, 388 
 phenomena, 373 
 
 Metabolism, xxxix, 373, 388 
 
 Metakresol, 440 
 
 Metalbumin, 409 
 
 Metallic tinkling, 205 
 
 Metalloscopy, 854 
 
 Metamorphosis, 857 
 
 Metanephros, 898 
 
 Meteorism, 264 
 
 Methaemoglobin, 39 
 
 Methylamine, 417 
 
 Meynert's projection systems, 
 676 
 theory, 706 
 
 Micrococci, 66 
 
 Micrococcus urese, 445 
 
 Microcytes, 34 
 
 Micropyle, 863 
 
 Micturition, 473 
 
 centre for, 669 
 
 Migration of ovum, 873 
 
 Milk, 377 
 
 action of drugs on, 379 
 coagulation of, 378 
 colostrum, 379 
 composition of, 379 
 curdling ferment, 276, 283, 
 
 379 
 
 digestion of, 276 
 
 fever, 377, 903 
 
 globules of, 377 
 
 plasma, 378 
 
 preparations of, 380 
 
 substitutes for, 379 
 
 sugar, 378, 415 
 
 tests for, 380 
 Millon's reagent, 275 
 Mimetic spasm, 634 
 Mimicry, 559 
 Minor chord, 829 
 Mixed colors, 791 
 Molecular basis of chyle, 338 
 Molecules, xxxii 
 Monoplegia, 727 
 Monospasm, 728 
 Moore's test, 246 
 Moreau's experiment, 306 
 Morphology, xxxii 
 Morula, 874 
 Motor centres, dog, 715 
 excision of, 721 
 nerves, 613 
 Motor points on the surface, 606 
 Mouth, 232 
 
 glands of, 232 
 Mouvement de Manege, 738 
 Movements of the eye, 799 
 forced, 738 
 
INDEX. 
 
 915 
 
 Movements, incoordinated, 648 
 
 JMucedin, 41 1 
 
 Mucigen, 321 
 
 Mucin, 411 
 
 Mucous membrane currents, 591 
 
 tissue, 758 
 Mucus, effect of drugs.on, 227 
 
 formation of, 227 
 Mulberry mass, 874 
 Mulder's test, 246 
 Milller's ducts, 898 
 
 experiment, 106, 133 
 
 fibres, 755 
 
 valve, 209 
 Multiplicator, 579 
 Murexide test, 435 
 Murmurs, cardiac, 91 
 venous, 164 
 Muscat volitantes, 779 
 Muscarin, 259 
 Muscle, 493 
 
 action of two stimuli 
 on, 520 
 
 action of veratrin, 519 
 
 active changes in, 511 
 
 arrangement of, 535 
 
 atrophic proliferation of, 
 
 S39 
 blood vessels of, 500 
 cardiac, 498 
 changes during contrac- 
 tion, 511 
 chemical composition, 
 
 500 
 curve of, 515 
 degenerations of, 539 
 development of, 499 
 effect of acids on, 506 
 effect of cold on, 507 
 effect of distilled water 
 
 on, 505 
 effect of exercise on, 
 
 502 
 effect of fatigue on, 518 
 effect of heat on, 505 
 elasticity of, 526 
 electricity of, 588 
 excitability of, 506 
 extractives of, 503 
 fatigue of, 531 
 formation of heat in, 529 
 glycogen in, 503 
 of heart, 67 
 involuntary, 493 
 lymphatics of, 497 
 metabolism of, 502 
 myosin of, 501 
 nerves of, 497 
 nutrition of, 538 
 perimysium of, 493 
 physical characters, 500 
 plasma of, 501 
 polarized light on, 496 
 red and pale, 498, 523 
 relation to tendons, 497 
 rhythmical contraction, 
 510 
 
 Muscle, rigor mortis of, 504 
 
 rods, 496 
 
 sensibility, 529, 854 
 
 serum of, 501 
 
 smooth, 499 
 
 sound of, 530 
 
 spectrum of, 498 
 
 stimuli of, 506 
 
 structure of striped, 493 
 
 tetanus, 521 
 
 tonus, 529, 669 
 
 uses of, 535 
 
 voluntary, 493 
 
 work of, 524 
 Muscle current, 591 
 
 theories, 595 
 Muscle plate, 878 
 Muscular contraction (see Myo- 
 gram), rate of, 523 
 Muscular sense, 854 
 
 work, 524 
 
 laws of, 525 
 Mutes, 558 
 Mydriasis, 619 
 Mydriatics, 777 
 Myelin forms, 283, 564 
 Myocardium, 68 
 Myogram, effect of weights on, 
 
 - 5i8 
 effect of fatigue on, 
 
 5i8 
 
 effect of constant cur- 
 rent on, 518 
 
 method of studying, 
 
 5'3 
 stages of, 515 
 Myograph, Helmholtz's, 514 
 
 pendulum, 515 
 
 Pfluger's, 515 
 
 simple, 515 
 
 spring, 515 
 Myohaematin, 413 
 Myopia, 771, 773 
 Myoryctes Weismanni, 500 
 Myosin, 381, 409, 501 
 Myosis, 620 
 Myotics, 777 
 Myxoedema, 179, 614 
 
 Nails, 479 
 
 Narcotics, 854 
 
 Nasal breathing, 207 
 timbre, 557 
 
 Nasmyth's membrane, 250 
 
 Native albumins, 409 
 
 Natural selection, 903 
 
 Near point, 770 
 
 Neef's hammer, 585 
 
 Negative accommodation, 766 
 pressure, 327 
 variation, 591, 593 
 
 Nephrozymose, 441 
 
 Nerve cells, bipolar, 566 
 
 multipolar, 565, 659 
 of aerebrum, 709 
 Purkinje's, 739 
 with a spiral fibre, 566 
 
 Nerve centres, general functions, 
 
 653 
 Nerve current, 588 
 Nerve fibres, 561 
 
 action of nitrate of silver 
 on, 564 
 
 chemical properties of, 
 566 
 
 classification of, 613 
 
 death of, 576 
 
 degeneration of, 572 
 
 development of, 565 
 
 division of, 564 
 
 effect of a constant cur- 
 rent on, 571 
 
 electrical current of, 591, 
 
 594 
 excitability of, 568 
 fatigue of, 572 
 incisures of, 564 
 mechanical properties of, 
 
 568 
 medullated, 562 
 metabolism of, 568 
 nutrition of, 572 
 Ranvier's nodes, 564 
 reaction of, 567 
 regeneration of, 575 
 sheaths of, 562 
 stimuli of, 568 
 structure of, 561 
 suture of, 575 
 terminations of, 844 
 to glands, 237 
 traumatic degeneration 
 
 of. 574 
 trophic centres of, 574 
 unequal excitability of, 
 
 572 
 Nerve impulse, rate of, 602 
 
 method of measuring, 603 
 modifying conditions, 
 
 603 
 variations of, 605 
 Nerve motion, 606 
 Nerve-muscle preparation, 593 
 Nerves, anabolic, 615 
 cranial, 615 
 electrical, 606 
 intercentral, 615 
 katabolic, 373, 615 
 motor, 613 
 secretory, 613 
 sensory, 615 
 special sense, 615 
 spinal, 645 
 trophic, 613 
 union of, 575 
 visceral, 615 
 Nerve stretching, 569 
 Nervi nervorum, 565 
 Nervous system, 561 
 
 development of, 900 
 Nervus abducens, 630 
 accessorius, 644 
 acusticus, 634 
 depressor, 132, 640 
 
916 
 
 Nervus erigens, 669, 701, 870 
 facialis, 631 
 glossopharyngeus, 637 
 hypoglossus, 645 
 oculomotorius, 618 
 olfactorius, 615 
 opticus, 616 
 sympathicus, 649 
 trigeminus, 621 
 trochlearis, 621 
 ■ vagus, 638 
 Neubauer's test, 346 
 Neuralgia, 854 
 Neural tube, 827 
 Neurasthenia gastrica, 315 
 Neurin, 414 
 Neuro-epithelium, 756 
 Neuroglia, 657 
 Neuro-keratin,4H, 564 
 Neuro-muscular cells, 509 
 New-born child, digestion of, 
 283 
 pulse, 127 
 size, 405 
 temperature, 358 
 urine of, 428 
 weight, 405 
 Nictitating membrane, 813 
 Nitrites, 42 
 Nitrogen in air, 212 
 in blood, 62 
 in body, 407 
 „ given off, 393 
 Nceud vital, 686 
 Noises, 828 
 Nose, development of, 901 
 
 structure, 839 
 Notochord, 877 
 Nuclear spindle, 873 
 Nuclein, 45, 411 
 Nucleus of Pander, 865 
 Nussbaum's experiments, 462 
 Nutrient arteries, 744 
 enemata, 331 
 Nyctalopia, 618 
 Nystagmus, 620, 738 
 
 Oatmeal, 383 
 
 Oculomotorius, 618 
 
 Odontoblasts, 249 
 
 OEdema, 344 
 
 cachectic, 345 
 pulmonary, 207 
 
 CEsophagus, 256 
 
 Ohm's law, 577 
 
 Oidium albicans, 229 
 
 Oleic acid, 414 
 
 Oligemia, 66 
 
 Olfactory centre, 724 
 
 nerve, ^fcVW^ 
 sensations, 849. 
 
 Omphalo-mesenteric duct, 879 
 vessels, 879 
 
 Onamatopoesy, 559 
 
 Oncograph, 467 
 
 Oncometer, 467 
 
 Ontogeny, 904 
 
 INDEX. 
 
 Opening shock, 584 
 Ophthalmia neuro-paralytica, 
 624 
 intermittens, 626 
 sympathetic, 626 
 Ophthalmic nerve, 621 
 Ophthalmometer, 765 
 Ophthalmoscope, 783 
 Optic nerve, 616 
 
 radiation, 616 
 thalamus, 735 
 tract, 616 
 vesicle, 877 
 Optical cardinal points, 764 
 Optogram, 790 
 Optometer, 772 
 Organ albumin, 388 
 Organic albumin, 389 
 
 compounds, 408 
 reflexes, 668 
 Orthopncea, 196 
 Orthoscope, 784 
 Osmasome, 382 
 Ossein, 411 
 Osseous system, formation of, 
 
 888 
 Osteoblasts, 891 
 Osteoclasts, 892 
 Osteomalacia, 539 
 Otic ganglion, 628 
 Ovarian tubes, 863 
 Ovary, 862, 898 
 Overcrowding, 226 
 Ovulation, 868 
 
 theories of, 868 
 Ovum,' 862 
 
 development of, 863 
 discharge of, 863 
 fertilization of, 872 
 impregnation of, 873 
 maturation of, 873 
 migration of, 873 
 structure of, 862 
 Oxalic acid, 414, 437 
 series, 414 
 Oxaluria, 437 
 Oxaluric acid, 437 
 Oxy-acids, 417 
 Oxygen, absorption of, 217 
 in blood, 59 
 estimation of, 209 
 forms of, 61 
 in body, 407 
 Oxyhsemoglobin, 39 
 Oxyakoia, 634 
 Ozone in blood, 60 
 
 Pacchionian bodies, 743 
 Pacini's corpuscles, 844 
 Pain, 853 
 
 irradiation of, 853 
 Painful impressions, conduction 
 
 of, 672 
 Palmitic acid, 414 
 Palpitation, 78 , 
 
 Pancreas, 278 
 
 changes in, 279 
 
 Pancreas, development of, 897 
 fistula of, 279 
 juice of, 279 
 paralytic secretion, 
 284 
 Pancreatic secretion, 283 
 . actions of, 283 
 artificial juice, 282 
 action of nerves on, 
 
 284 
 action of poisons on, 
 
 284 
 composition, 280 
 extracts, 283 
 Panophthalmia, 624 
 Pansphygmograph, 120 
 Papain, 282 
 Papilla foliata, 844 
 Parablastic cells, 878 
 Paradoxical contraction, 595 
 
 reaction, 244 
 Paraglobulin, 409 
 Parakresol, 440 
 Paralbumin, 409 
 Paralgia, 854 
 
 Paralytic secretion of saliva, 
 239 
 pancreatic juice, 283 
 Paramylum, 416 
 Paraphasia, 731 
 Paraxanthin, 417, 436 
 Parelectronomy, 596 
 Paridrosis, 489 
 Paroophoron, 899 
 Parotid gland, 233 
 Parovarium, 898 
 Parthenogenesis, 857 
 Partial pressure, 57 
 reflexes, 661 
 Particles, xxxii 
 Parturition, centre for, 669 
 Passavant's elevation, 254 
 Passive insufficiency, 537 
 Patellar reflex, 667 
 Pathic reflex, 666 
 Pavy's test, 246 
 Pecten, 813,901 • 
 Pectoral fremitus, 205 
 Pedunculi cerebri, 736 
 Penis, erection of, 869 
 Pepsin, 269 
 Pepsinogen, 271 
 Peptic glands, 266 
 
 changes in, 270 
 Peptone, 274 
 
 forming ferment, 270, 
 
 280 
 metabolism of, 396 
 tests for, 275 
 Peptonized foods, 284 
 Peptonuria, 447 
 Percussion of heart, 93 
 
 lungs, 195, 203 
 Perforating ulcer of the foot, 
 
 614 
 Pericardium, 71 
 Perilymph, 826 
 
INDEX. 
 
 917 
 
 Perimeter, Aubert and Forster, 
 788 
 
 McHardy's, 788 
 
 Priestley Smith's, 789 
 Perimetric chart, 789 
 Perimetry, 788 
 Perimysium, 493 
 Perineurium, 565 
 Periodontal membrane, 25 1 
 Peristaltic movement, 259 
 
 action of blood on, 
 262 
 
 action of nerves on, 
 264 
 Peritoneum, development of, 
 
 897 
 Perivascular spaces, 334 
 Pettenkofer's test, 294 
 Peyer's glands, 318 
 ■ Pfltiger's law, 601 
 
 law of reflexes, 662 
 Phagocytes, 31 
 Phakoscope, 769 
 Phanakistoscope, 796 
 Phases, displacement of, 831 
 Phenol, 311, 415, 440 
 Phenolsulphuric acid, 440 
 Phlebogram, 165 
 Phonation, 547 
 Phonograph, 833 
 Phonometry, 204 
 Phosphoric acid, 442 
 Phosphenes, 780 
 Photophobia, 634 
 Photopsia, 618 
 Phrenograph, 194 
 Phrenology, 704 
 Phylogeny, 904 
 Phytalbumose, 410 
 Phytomycetes, 456 
 Pia mater, 742 
 Picric acid test, 452 
 Picro-saccharimeter, 453 
 Pigment cells, 492 
 Pitch, 828 
 Placenta, 884 
 Placental bruit, 164 
 Plantar reflex, 666 
 Plants, characters of, xxxviii 
 
 electrical currents . in, 
 
 597 
 
 Plasma cells, 742 
 
 of blood, 46, 54 
 of lymph, 338 
 of milk, 378 
 of muscle, 501 
 
 Plasmine, 50 
 
 Plethora, 64 
 
 Plethysmography, 167 
 
 Pleura, 187 
 
 Pleuro-peritoneal cavity, 878 
 
 Pleximeter, 202 
 
 Pneumatogram, 194 
 
 Pneumatometer, 206 
 
 Pneumograph, 194 
 
 Pneumonia after section of vagi, 
 641 
 
 Pneumothorax, 190 
 Poikilothermal animals, 350 
 Poiseuille's space, 161 
 Poisons, heart, 103 
 
 on vasomotor nerves, 
 
 696 
 spinal cord, 664 
 Polar globules, 873 
 Polarization, galvanic, 579 
 internal, 583 
 Polarizing after currents, 595 
 Politzer's ear bag, 824 
 Polyasmia, 63 
 
 apocoptica, 63 
 aquosa, 64 
 hyperalbuminosa, 64 
 polycythsemica, 64 
 serosa, 64 
 transfusoria, 63 
 Polyopia monocularis, 775 
 Pons Varolii, 736 
 Porret's phenomenon, 500, 583 
 Portal canals, 285 
 
 circulation, 67 
 
 system, development of, 
 
 895 
 vein in liver, 285 
 vein, ligature of, 153 
 Positive accommodation, 768 
 
 after images, 796 
 Potash salts, 407 
 Potassium sulphocyanide, 441 
 Potatoes, 384 
 Presbyopia, 772 
 Pressor fibres, 673, 697 
 Pressure, arterial, 145 
 
 atmospheric, 229 
 intra-labyrinthine, 827 
 of blood, 141 
 respiratory, 205 
 sense of, 850 
 Presystolic sound, 91 
 Prickle cells, 477 
 Primitive anus, 881 
 
 chorion, 875, 883 
 circulation, 879 
 groove, 875 
 kidneys, 897 
 mouth, 881 
 streak, 875 
 Primordial cranium, 888 
 
 ova, 863 
 Principal focus, 759 
 point, 761 
 Progressive muscular atrophy, 
 
 539 
 Pronephros, 898 
 Pronucleus, male, 874 
 
 female, 873 
 Propepsin, 271 
 Propeptone, 274 
 Protagon, 413, 567 
 Proteids, 408 
 
 coagulated, 410 
 gastric digestion of, 
 
 274 
 fermentation of, 310 
 
 Proteids, pancreatic digestion of, 
 280 
 
 reactions of, 408 
 
 vegetable, 410 
 Protistae, xxxi 
 Protodceum, 875 
 Protovertebrae, 878 
 Pseudo-hypertrophic paralysis, 
 
 539 
 
 Pseudo-motor action, 632 
 
 Pseudoscope, 808 
 
 Pseudo-stomata, 186 
 
 Psychical activities, 703 
 blindness, 722 
 deafness, 723 
 
 Psycho-acoustic centre, 732 
 geusic centre, 732 
 motor centre, 718 
 optic centre, 731 
 physical law, 748 
 sensorial centres, 721 
 sensory paths, 731 
 
 Ptomaines, 275 
 
 Ptosis, 619 
 
 Ptyalin, 244 
 
 Ptyalism, 241 
 
 Puberty, 866 
 
 Pulmonary artery .pressure in,l 53 
 
 Pulmonary oedema, 207 
 
 Pulp of tooth, 251 
 spleen, 173 
 
 Pulse, 117 
 
 capillary, 140 , 
 catacrotic, 121 
 characters of, 127 
 conditions affecting, 127 
 curve, 129 
 dicrotic, 126 
 entoptical, 137, 780 
 historical, 116 
 hyperdicrotic, 127 
 in animals, 128 
 in jugular vein, 166 
 influence of pressure on, 
 
 133 
 
 influence of respiration 
 on, 131 
 
 instruments for investi- 
 gating, 117 
 
 in liver, 166 
 
 monocrotic, 127 
 
 of various arteries, 129 
 
 paradoxical, 133 
 
 pathological, 137 
 
 recurrent, 130 
 
 trigeminal, 128 
 
 variatians in, 128 
 
 venous, 165 
 
 wave, 132, 136 
 Pulses, 383 
 Pulsus alternans, 128 
 
 bigeminus, 128 
 
 caprizans, 127 
 
 dicrotus, 126 
 
 intercurrens, 128 
 
 myurus, 128 
 Pumping mechanisms, 342 
 
918 
 
 INDEX. 
 
 Pupil, 776 
 
 action of poisons on, 777 
 Argyll Robertson, 777 
 functions of, 775 
 movements of, 776 
 photometer, 778 
 size of, 378 
 Purgatives, 265 
 Purkinje, cells of, 739 
 
 fibres of, 72, 498 
 figure, 779 
 Sanson's images, 768 
 Putrefactive processes, 307 
 Pyloric glands, 267 
 
 changes in, 270 
 Pyramidal tracts, 678 
 
 degeneration of, 727 
 Pyrokatechin, 415, 440 
 
 Quality of a note, 828 
 Quantity of blood, 63, 159 
 food, 389 
 
 Rales, dry, 205 
 
 moist, 205 
 Rami communicantes, 649 
 Range of accommodation, 770 
 Ranvier's nodes, 564 
 Raynaud's disease, 614 
 Reaction impulse, 81 
 Reaction of degeneration, 607, 
 
 610 
 Reaction time, 605 
 Recovery, 533 
 Rectum, 265 
 Recurrent pulse, 130 
 
 sensibility, 646 
 Red blindness, 794 
 Reduced eye of Listing, 764 
 Reductions in intestine, 308 
 Reflex acts, examples of, 662 
 
 inhibition of, 664 
 
 movements, 666 
 
 movements, theory of, 
 666 
 
 nerves, 615 
 
 spasms, 661 
 
 tactile, 672 
 
 time, 664 
 
 tonus, 670 
 Refracted ray, 761 
 Refractive indices, 761 
 Regeneration of tissues, 402 
 nerve, 575 
 Regio olfactoria, 839 
 
 respiratoria, 839 
 Reissner's membrane, 825 
 Relative proportions of diet, 389 
 Remak's ganglion, 94 
 Renal plexus, 461 
 Rennet, 276, 378 
 Reproduction, forms of, 856 
 Requisites in a proper diet, 
 
 389 
 Reserve air, 191 
 Residual air, 191 
 
 Resistance, 109 
 Resonance organs, 545 
 Resonants, 557 
 Resonators, 11,31 
 Respiration, 183 
 
 amphoric, 205 
 artificial, 224 
 bronchial, 204 
 centre for, 686 
 chemistry of, 209 
 cog-wheel, 205 
 cutaneous, 219 
 forced, 195 
 in a closed space, 
 
 221 
 in animals, 192 
 internal, 219 
 intestinal, 230 
 mechanism of, 190 
 muscles of, 196 
 nasal, 207 
 number of, 192 
 periodic, 196 
 pressure during, 205 
 sounds of, 204 
 time of, 192 
 type, 195 
 variations of, 192 
 vesicular, 204 
 Respiratory apparatus, 183 
 
 Andral and Gavar- 
 
 ret, 209 
 centre, 686 
 mechanism of, 190 
 v. Pettenkofer, 211 
 quotient, 212 
 Regnault and Rei- 
 
 set, 211 
 Scharling, 210 
 Rete mirabile, 67 
 Retina, 754 
 
 activity in vision, 785 
 blood vessels of, 753 
 chemistry of, 757 
 capillaries, movements 
 
 in, 779 
 epithelium of, 756 
 rods and cones of, 756 
 stimulation of, 796 
 structure of, 757 
 visual purple of, 756 
 Retinal image, formation of, 764 
 
 size of, 765 
 Retinoscopy, 784 
 Rigor mortis, 504 
 Rheocord, 578 
 Rheometer, 155 
 Rheophores, 606 
 Rheoscopic limb, 590 
 Rheostat, 578 
 Rheotom, 593 
 Rhinoscopy, 552 
 Rhodophane, 757 
 Rhodopshv 756 
 Rickets, 539 
 
 Ritter's opening tetanus, 600, 
 602 
 
 Ritter's tetanus, 600 
 Ritter-Valli law, 576 
 Rods and cones, 756 
 Rotatory disk for colors, 791 
 Running, 543 
 
 Saccharomycetes, 386 
 
 Saccharose, 415 
 
 Saccule, 825 
 
 Saftcanalchen, 332 
 
 Saline cathartics, 265 
 
 Saliva, action of nerves on, 237 
 action of poisons on, 241 
 action on starch, 244 
 chorda, 238 
 composition of, 243 
 
 Saliva facial, 237 
 
 functions of, 244 
 mixed, 243 
 new-born child, 244 
 parotid, 240 
 pathological, 314 
 ptyalin, 245 
 reflex secretion of, 238 
 sublingual, 243 
 submaxillary, 242 
 sympathetic, 238 
 theory of secretion, 239 
 
 Salivary corpuscles, 243 
 glands, 233 
 changes in, 235 
 development of, 896 
 nerves of, 237 
 
 Salts, 407 
 
 Sanson-Purkinje's images, 779 
 
 Saponification, 283 
 
 Sarcini ventriculi, 315 
 
 Sarcolactic acid, 501 
 
 Sarcolemma, 494 
 
 Sarkin, 417, 436 
 
 Sarkosin, 417 
 
 Saviotti's canals, 279 
 
 Scheiner's experiment, 770 
 
 Schift's test, 436 
 
 Schizomycetes, 66 
 
 Schmidt's researches, 50 
 
 Schreger's lines, 250 
 
 Schwann's sheath, 562 \ 
 
 Sclerotic, 753 
 
 Scoliosis, 538 
 
 Scotoma, 789 
 
 Screw-hinge j'oint, 534 
 
 Scrotum, formation of, 899 
 
 Scurvy, 65 
 
 Scyllit, 417 
 
 Sebaceous glands, 482 
 
 secretion, 483 
 
 Seborrhcea, 489 
 
 Secondary circulation, 879 
 contraction, 592 
 degeneration, 660 
 tetanus, 592 
 
 Secretion currents, 596 
 
 Secretory nerves, 613 
 
 Sectional area, 157 
 
 Segmentation sphere, 874 
 
 Self-stimulation of muscle, 591 
 
INDEX. 
 
 919 
 
 Semen, composition of, 860 
 ejaculation of, 872 
 reception of, 872 
 Semicircular canals, 826 
 Sensation, 748 
 Sense organs, 748 
 
 development of, 901 
 Sensory areas, 724 
 
 crossway, 679 
 paths, 679 
 Serin, 417 
 
 Serum of blood, 46, 54 
 Serum albumin, 55, 409 
 globulin, 54, 409 
 Setschenow's centres, 665 
 Sex, difference of, 900 
 Shadows, lens, 779 
 
 colored, 798 
 Sharpey's fibres, 892 
 Short-sightedness, 771 
 Shunt, 582 
 Sialogogues, 241 
 Sighing, 208 
 Simple colors, 791 
 Simultaneous contrast, 784 
 Single vision, 803 
 Sitting, 540 
 Size, 405 
 
 estimation of, 808 
 false estimate of, 808 
 Skatol, 311, 441 
 Skin, absorption by, 489 
 chorium of, 477 
 epidermis, 477 
 functions of, 484 
 galvanic conduction of, 489 
 glands of, 482 
 historical, 490 
 protective covering, 483 
 respiratory organ, 484 
 structure of, 477 
 varnishing the, 371, 484 
 Skin currents, 591 
 Sleep, 707 
 Small intestine, 319 
 
 absorption by, 327 
 structure of, 319 
 Smegma, 485 
 Smell, sense of, 839 
 Sneezing, 207 
 Snellen's types, 772 
 Sniffing, 840 
 Snoring, 208 
 Sodic chloride, 407, 442 
 
 salts, 408 
 Solitary follicles, 324 
 Somatopleure, 878 
 Sorbin, 417 
 Sound, 815 
 
 conduction to ear, 815 
 direction of, 836 
 distance of, 837 
 perception of, 837 
 reflection of, 815 
 Sounds, cardiac, 85 
 
 cracked-pot, 204 
 tympanitic, 203 
 
 Sounds, vesicular, 204 
 Spasm centre, 702 
 Spasmus nictitans, 634 
 Specific energy, 790 
 Spectacles, 773, 813 
 Spectra, absorption, 38 
 flame, 38 
 optical, 781 
 Spectroscope, 38 
 Spectrum mucro-lacrimale, 779 
 of bile, 295 
 of blood, 39 
 of muscle, 496 
 Speech, 555 
 
 centre for, 729 
 pathological variations, 
 
 558 
 
 Spermatin, 860 
 
 Spermatozoa, 860 
 
 Spermatoblasts, 858 
 
 Spina bifida, 743, 880 
 
 Spinal accessory nerve, 644 
 
 Spinal cord, 654 
 
 action of blood and poi- 
 sons on, 671 
 anterior roots of, 647 
 blood vessels of, 658 
 centres, 668 
 
 conducting paths in, 671 
 conducting system of, 659 
 development of, 901 
 degeneration of, 659 
 excitability of, 670 
 Flechsig's systems, 659 
 ganglion, 645 
 Gerlach's theory, 657 
 nerves, 645 
 neuroglia of, 657 
 nutritive centres in, 660 
 posterior roots of, 648 
 reflexes, 661 
 regeneration of, 703 
 secondary degeneration 
 
 of, 659 
 segment of, 680 
 structure of, 654 
 time of development, 661 
 transverse section of, 673 
 unilateral section of, 674 
 vasomotor centres in, 696 
 WoroschilofPs observa- 
 tions, 656 
 
 Spheno-palatine ganglion, 626 
 
 Spherical aberration, 774 
 
 Sphincters, 535 
 
 Sphincter ani, 260 
 
 pupillfe, 754 
 urethra, 472 
 
 Sphymograph, 118 
 
 Dudgeon's, 120 
 Marey's, 118 
 
 Sphygmometer, 129 
 
 Sphygmogram, 122 
 
 Sphygmomanometer, 144 
 
 Sphygmoscope, 122 
 
 Spiral joints, 534 
 
 Spirillum, 66 
 
 Spirochaeta, 66 
 
 Spirometer, 191 
 
 Splanchnic nerve, 65 1 
 
 Splanchnopleure, 878 
 
 Spleen, 172 • 
 
 action of drugs on, 175 
 chemical composition, 
 
 174 
 
 contraction of, 175 
 
 extirpation of, 174 
 
 functions of, 174 
 
 influence of nerves on, 
 176 
 
 oncograph, 175 
 
 regeneration of, 174 
 
 structure, 172 
 
 tumors of, 177 
 Spongin, 41 1 
 
 Spontaneous generation, 856 
 Spores, 308 
 
 Spring kymograph, 143 
 Spring myograph, 515 
 Springing, 542 
 Sputum abnormal, 229 
 
 normal, 227 
 Squint, 619 
 Stammering, 559 
 Standing, 539 
 Stannius's experiment, 96 
 Stapedius, 822 
 Starch, 416 
 Stasis, 162 
 
 Statical theory of Goltz, 637 
 Stationary vibrations, 816 
 Steapsin, 283 
 Stenopaic spectacles, 774 
 Stenosis, 88 
 
 Stenson's experiment, 505 
 Stercobilin, 296, 312 
 Stercorin, 313 
 Stereoscope, 807 
 Stereoscopic vision, 805 
 Sternutatories, 207 
 Stethograph, 193 
 Stigmata, 113 
 Stilling, canal of, 758 
 Stimuli, 506 
 
 adequate, 748 
 
 heterologous, 748 
 
 homologous, 748 
 
 muscular, 509 
 Stoffwechsel, xxxix 
 Stomach, 266 
 
 catarrh of, 319 
 changes in glands, 270 
 diseases of, 314 
 gases in, 278 
 glands of, 266 
 movements of, 256 
 structure of, 266 
 Stomata, 113, 335 
 Stomodceum, 875 
 Storage albumin, 388 
 Strabismus, 738 
 Strangury, 475 
 Strasburg's test, 451 
 Strobic disks, 797 
 
920 
 
 INDEX. 
 
 Stroma fibrin and plasma fibrin, 
 
 54 
 Struggle for existence, 903 
 Strychnin, action of, 663 
 Stuttering, 559 
 Subarachnoid space, 742' 
 
 fluid, 743 
 Subdural space, 742 
 Subjective sensations, 749 
 Sublingual gland, 240 
 Submaxillary ganglion, 628 
 atropin on, 239 
 gland, 237 
 saliva, 239 
 Successive beats, 836 
 
 contrast, 799 
 Succinic acid, 414 
 Succus entericus, 303 
 
 action of drugs on, 306 
 Suction, 248 
 Sudorifics, 486 
 Sugars, 415 
 
 estimation of, 247 
 tests for, 246 
 Sulphindigotate of soda, 461 
 Summation of stimuli, 521, 622 
 Summational tones, 836 
 Superfecundation, 873 
 Superficial reflexes, 666 
 Superfcetation, 873 
 Superior maxillary nerve, 626 
 Suprarenal capsules, 180 
 Surditas verbalis, 732 
 Sutures, 535 
 Sweat, 484 
 
 chemical composition, 
 
 48S 
 conditions influencing se- 
 cretion, 486 
 excretion of substances 
 
 by, 486 
 glands, 483 
 insensible, 485 
 nerves, 487 
 pathological variations of, 
 
 488 
 centre, 488 
 
 spinal, 670 
 Swimming, 544 
 Sympathetic ganglion, 649 
 nerve, 649 
 section, 651 
 stimulation of, 651 
 Sympheses, 535 
 Synchondroses, 535 
 Syncope, 78 
 Synergetic muscles, 538 
 Synovia, 534 
 Syntonin, 274 
 Systole, cardiac, 75 
 
 Tabes, 672 
 
 Taches cerebrales, 701 
 
 Tactile, areas, 724 
 
 corpuscles, 846 
 
 sensations, conduction 
 of, 846 
 
 Tsenia, 857 
 Tail-fold, 878 
 Talipes calcaneus, 538 
 equinus, 538 
 varus, 538 
 Tambour, Marey's, 1 20 
 Tapetum, 784 
 Tapping experiment, 691 
 Taste bulbs, 841 
 organ of, 841 
 testing, 842 
 Taurin, 417 
 Taurocholic acid, 293 
 Tea, 385 
 Tears, 810 
 Tegmentum, 676 
 Telestereoscope, 807 
 Temperature of animals, 351 
 
 accommodation for, 
 
 366 
 artificial increase 
 
 of, 369 
 estimation of, 351 
 how influenced, 354 
 lowering of, 370 
 postmortem, 369 
 regulation of, 361 
 topography of, 353 
 variations of, 358 
 Temperature sense, 852 
 
 illusions of, 853 
 Tendon, 500 
 
 nerves of, 500, 846 
 reflexes, 667 
 Tensor, choroideae, 753 
 
 tympani, 821 
 Testicle, descent of, 887 
 Testis, 857 
 Tetanomotor, 569 
 Tetanus, 521, 571, 663 
 
 secondary, 592 
 Thaumatrope, 796 
 Theobromin, 385 
 Thermal cortical centre, 160 
 Thermo-electric methods, 351 
 needles, 353 
 Thermometer, 351 
 
 metastatic, 351 
 maximal and mini- 
 mal, 351 
 outflow, 351 
 Thermometry, 351 
 Thirst, 390 
 Thiry's fistula, 304 
 Thomson's disease, 520 
 Thoracometer, 201 
 Thymus, 177 
 
 development of, 889 
 Thyroid, 178 
 
 development of, 889 
 Tidal air, 191 
 
 wave, 123 • 
 Timbre, 557, 828 
 Time in psychical processes, 
 
 707 
 Time sense, 830 
 Tinnitus, 637 
 
 Tissue formers, 390 
 
 regeneration of, 402 
 Tissue metabolism, 400 
 Tobin's tubes, 227 
 Tomes, fibres of, 249 
 Tone inductorium, 523 
 Tones, 828 
 Tongue, glands of, 232 
 
 movements of, 253 
 nerves of, 253 
 taste bulbs, 841 
 Tonometer, 98 
 Tonus, 670 
 Tonsils, 233 
 Tooth, 249 
 
 action of drugs on, 253 
 chemistry of, 251 
 development of, 251 
 eruption of, 252 
 permanent, 252 
 pulp of, 25 I 
 structure of, 249 
 temporary, 252 
 Toricelli's theorem, 108 
 Torpedo, 612 
 Torticollis, 644 
 Touch corpuscles, 844 
 Touch, sense of, 844 
 Trachea, 183 
 Transfusion, 63, 168 
 
 of blood, 168 
 of other fluids, 171 
 Transitional epithelium, 471 
 Transudations, 345 
 Transplantation of tissues, 405 
 Trapezius, spasm of, 644 
 Traube-Hering curves, 147 
 Traumatic . degeneration of 
 
 nerves, 574 
 Trichina, 857 
 Trigeminus, 624 
 
 ganglia of, 623, 626, 628 
 inferior maxillary branch, 
 
 627 
 neuralgia of, 629 
 ophthalmic branch, 621 
 paralysis of, 629 
 pathological, 629 
 section of, 628, 630 
 superiormaxillary branch, 
 
 626 
 trophic functions of, 624 
 Triple phosphate, 445 
 Trismus, 629 
 Trochlearis, 621 
 Trommer's test, 246 
 Trophic centres, 575 
 fibres, 624 
 nerves, 613, 624 
 Trophoneuroses, 614 
 Trotting, 544 
 Trypsin, 281 
 Trypsinogen. 281 
 Tryptone, 281 
 Tube casts, 456 
 Tubes, capillary, 115 
 division of, 115 
 
INDEX. 
 
 921 
 
 Tubes, elastic, 115 
 
 movements of fluids in, 
 116 
 
 rigid, 134 
 Tumullus sermonis, 730 
 Tunicin, 416 
 Turck's method, 666 
 Twins, 873 
 Twitch, 515 
 Tympanic membrane, 816 
 
 artificial, 818 
 Tyrosin, 310,411,454 
 
 Ulcer of foot, perforating, 614 
 Unipolar induction, 585 
 
 stimulation, 572 
 Umbilical arteries, 882 
 cord, 885 
 veins, 882, 886 
 vesicle, 879 
 Upper tones, 83 1 
 Urachus, 882 
 Uraemia, 469 
 Urates, 435 
 Urea, 417, 430 
 
 compounds of, 432 
 
 decomposition, 430 
 
 effect of exercise on, 431 
 
 ferment, 443 
 
 formation of, 431, 463 
 
 nitrate of, 432 
 
 occurrence of, 431 
 
 oxalate of, 432 
 
 pathological, 431 
 
 phosphate of, 432 
 
 preparation of, 432 
 
 properties of, 430 
 
 qualitative estimation of, 
 
 43 2 
 quantitative estimation of, 
 
 432 
 quantity of, 430 
 relation of, to muscular 
 work, 431, 503 
 Ureameter, 432 
 Ureter, ligature of, 463 
 
 structure and functions 
 of, 470 
 Uric acid, 417 
 diathesis, 470 
 formation of, 434, 464 
 occurrence, 435 
 properties of, 434 
 qualitative estimation, 435 
 quantitative estimation, 436 
 quantity, 434 
 solubility, 435 
 tests for, 435 
 Urinary bladder, 471 
 calculi, 458 
 closure of, 472 
 deposits, 455 
 development of, 882 
 organs, 419 
 pressure in, 475 
 Urine, 426 
 
 accumulation of, 472 
 
 Urine, acid fermentation, 443 
 acidity, 430 
 albumin in, 445 
 alkaline fermentation, 
 
 445 
 alkaloids in, 469 
 amount of solids, 427 
 bile in, 450 
 blood in, 447 
 calculi, 458 
 changes of in bladder, 
 
 475 
 color; 427 
 
 coloring matters of, 428 
 consistence, 429 
 cystin in, 454 
 deposits in, 455 
 dextrin in, 453 
 effect of blood pressure 
 
 on, 465 
 egg albumin in, 447 
 electrical condition of, 
 
 611 
 excretion of pigments by, 
 
 462 
 fermentations of, 443 
 fluorescence, 429 
 fungi in, 455 
 gases in, 443 
 globulin in, 447 
 incontinence of, 475 
 influence of nerves on, 
 
 465 
 inorganic constituents, 
 
 441 
 inosit in, 454 
 leucin in, 454 
 milk sugar in, 453 
 movement of, 470 
 mucin in, 447 
 mucus in, 447 
 organisms in, 455 
 passage of substances 
 
 into, 465 
 peptone in, 447 
 phosphoric acid in, 442 
 physical characters of, 
 
 426 
 pigments of, 427 
 preparation of, 463 
 propeptone in, 447 
 quantity, 426 
 reaction, 429 
 retention of, 475 
 secretion of, 459 
 silicic acid in, 443 
 sodic chloride in, 442 
 specific gravity, 427 
 spontaneous changes in, 
 
 443 
 sugar in, 451 
 sulphuric acid in, 443 
 taste of, 429 
 test for albumin in, 446 
 tube casts in, 456 
 tyrosin in, 454 
 volume of, 467 
 
 Urinometer, 427 
 
 Urobilin, 439 
 
 Urochrome, 439 
 
 Uroerythrin, 439 
 
 Uro-genital sinus, 899 
 
 Uroglaucin, 439 
 
 Uromelanin, 439 
 
 Urostealith, 458 
 
 Uterine milk, 885 
 
 Uterus, 866 
 
 development of, 898 
 involution of, 903 
 nerves of, 902 
 
 Utricle, 825 
 
 Uvea, 753 
 
 Vagus, 638 
 
 cardiac branches, 640 
 depressor nerve of, 146, 
 
 640 
 effect of section, 641 
 pathological, 643 
 pneumonia after sec- 
 tion, 641 
 reflex effects of, 643 
 stimulation of, 1 50 
 unequal excitability of, 
 
 643 
 Valleix's points douloureux, 854 
 Valsalva's experiment, 105, 132, 
 
 822 
 Valve, ileo-colic, 259 
 
 pyloric, 257 
 Valves of heart, 7 1 
 disease of, 88 
 injury to, 78 
 of veins, 113 
 sounds of, 165 
 Valvular conniventes, 319 
 Varicose fibres, 561 
 Varix, 152 
 
 Varnishing the skin, 484 
 Vas deferens, 859 
 Vasa vasorum, 1 14 
 Vascular system, development 
 
 of, 892 
 Vaso-dilator centre, 701 
 nerves, 701 
 Vaso-formative cells, 26 
 Vasomotor centre, 695 
 spinal, 700 
 Vasomotor nerves, course of, 696 
 Vater's corpuscles, 845 
 Vegetable albumin, 410 
 casein, 410 
 foods, 383 
 proteids, 410 
 Veins, 113 
 
 cardinal, 894 
 development of, 894 
 movement of blood in, 
 
 163 
 
 murmurs in, 164 
 pressure in, 152 
 pulse in, 152 
 structure of, 112 
 tonus of, 700 
 
922 
 
 INDEX. 
 
 Veins, valves in, 113 
 
 valvular sounds in, 165 
 varicose, 152 
 velocity of blood in, 157 
 "Velocity of blood stream, 155 
 Ventilation, 226 
 Ventricles, 70, 75 
 
 aspiration of, 75 
 capacity of, 140, 159 
 duration of, 159 
 impulse of, 81 
 negative pressure in, 
 
 77 
 systole of, 82 
 Veratrin, 519 
 Vernix caseosa, 485 
 Vertebrae, mobility of, 540 
 Vertebral column, 880 
 Vertigo, 637 
 Vibrations of body, 137 
 Vibratives, 557 
 Vibrio, 66 
 Villus intestinal, 320 
 
 absorption by, 328 
 
 chorionic, 875 
 
 contractility of, 322 
 
 placental, 885 
 Violet blindness, 794 
 Visceral arches, 881 
 clefts, 881 
 Vision binocular, 803 
 
 single, 803 
 
 stereoscopic, 805 
 Visual angle, 765 
 
 apparatus, 750 
 
 centre, 722 
 
 purple, 756, 790 
 Vital capacity, 191 
 Vitellin, 409, 866 
 Vitelline duct, 879 
 
 Vitreous humor, 757 
 Vocal cords, 546 
 
 conditions influencing 
 the, 553 
 
 varying conditions of, 
 
 S49 
 Voice, falsetto, 554 
 
 in animals, 559 
 pathological variations of, 
 
 558 
 physics of, 545 
 pitch of, 545 
 production of, 554 
 range of, 554 
 Vomiting, 257 
 
 centre for, 258 
 Vowels, 830 
 
 analysis of, 555 
 artificial, 832 
 formation of, 555 
 Koenig's apparatus for, 
 833 
 
 Waking, 707 
 
 Walking, 541 
 
 Wallerian law of degeneration, 
 
 574 
 Warm-blooded animals, 350 
 Washed-blood clot, 50 
 Water, 373, 390, 407 
 
 absorbed by skin, 489 
 
 absorption of, 328 
 
 amount of, 407 
 
 exhaled by skin, 219, 
 484 
 
 exhaled frorn lungs, 212 
 
 hardness of, 374 
 
 impurities, 374 
 
 in urine, 428 
 
 vapor of, in air, 212 
 
 Wave pulse, 122 
 
 propagation of, 136 
 Wave movements, 815 
 Waves, in elastic tubes, 134 
 Weber's paradox, 528 
 
 law, 749 
 Weight, 405 
 Wharton's jelly, 885 
 Whispering, 555 
 White of egg, 409 
 Wine, 387 
 Wolffian bodies, 897 
 ducts, 899 
 Word blindness, 730, 731 
 
 deafness, 723 
 Work, 524 
 
 unit of, xxxiv 
 
 Xanthin, 417, 436 
 Xanthokyanopy, 795 
 Xanthophane, 757 
 Xanthoproteic, reaction, 408 
 Xerosis, 624 
 
 Yawning, 208 
 
 Yeast, 386 
 Yelk, 865 
 
 sack, 879 
 Yellow spot, 780 
 Young- Helmholtz theory, 793 
 
 Zimmermann, particles of, 34 
 Zinn, zonule of, 757 
 Zoetrope, 796 
 Zollner's lines, 810 
 Zona pellucida, 862 
 Zoogloea, 308 
 Zymogen, 281 
 Zymophytes, 277 
 
*Z?m 
 
 .-3»**"-